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Cover: The Advanced Gas -Cooled Reactor at Windscale, England. Reproducedby kind permission of the United Kingdom Atomic Energy Authority.

WHO Regional Publications

European Series No. 3

HEALTH IMPLICATIONS

OF NUCLEAR POWERPRODUCTION

Report on a Working GroupBrussels, 1 -5 December 1975

WORLD HEALTH ORGANIZATIONREGIONAL OFFICE FOR EUROPE

COPENHAGEN

1978

ISBN 92 9020 103 7

© World Health Organization 1977

Publications of the World Health Organization enjoy copyright protec-tion in accordance with the provisions of Protocol 2 of the Universal Copy-right Convention. For rights of reproduction or translation, in part or in toto,of publications issued by the WHO Regional Office for Europe applicationshould be made to that Office, Scherfigsvej 8, DK -2100 Copenhagen 0,Denmark. The Regional Office welcomes such applications.

The designations employed and the presentation of the material in thispublication do not imply the expression of any opinion whatsoever on thepart of the Secretariat of the World Health Organization concerning the legalstatus of any country, territory, city or area or of its authorities, or con-cerning the delimitation of its frontiers or boundaries.

The mention of specific companies or of certain manufacturers' productsdoes not imply that they are endorsed or recommended by the World HealthOrganization in preference to others of a similar nature that are not men-tioned. Errors and omissions excepted, the names of proprietary productsare distinguished by initial capital letters.

This report contains the collective views of a Working Group and doesnot necessarily represent the decisions or the stated policy of the WorldHealth Organization.

PRINTED IN DENMARK

Note

This report was previously issued for limited distribution under the sym-bol ICP /CEP 804(1) but some minor editorial amendments have been made.The Thirtieth World Health Assembly in May 1977 endorsed the use of SIunits in medicine, and such units will therefore be used in future publicationsof the World Health Organization. However, the present report was preparedbefore this resolution was taken, and it contains a few non -SI radiation units.In addition, Fig. 2 (pages 18 -20), which is reproduced from another publica-tion, contains a number of non -metric units. The conversion factors for all ofthese are given in the tables below.

Non -SI unit SI unit and symbol Conversion factor

rad gray, Gy 1 rad = 0.01 Gy

curie, Ci becquerel, Bq 1 Ci = 3.7 X 1010 Bq(or 37 GBq, gigabecquerel)

rem joule per kilogram, J /kg 1 rem = 0.01 J /kg

Unit asgiven in

Fig. 2

Correct name andsymbol if differentfrom those given

in Fig. 2

SI unit and symbolApproximate

conversionfactor

kwh kilowatt hour, joule, J 1 kW h = 3.6 X 106 Jkwh

acre square metre, m2 1 acre = 4 047 m2

ton ) 1 ton = 1 016 kgkilogram, kg (or 1 ton = 1.016 t)

( (or tonne, t)MT tonne, t / 1 t = 1 000 kg

gal. US gallon, 1 gal (US) = 3.785 X 10 -3 m3gal (US) cubic metre, m3 (or 1 gal = 3.785 litres)

(or litre, I)cu. ft. cubic foot, ft3 1 ft3 = 2.832 X 10 -3 m3

gal. /min. US gallon perminute,gal (US) /min

cubic metre per second, 1 gal (US) /min =m3 Is (or cubic metre 6.309 X 10 -5 m3 /sper minute, m3 /min) (or 3.785 X 10 -3 m3 /min)(or litres per secondor per minute may beused instead)

CONTENTS

Introduction1. Conclusions and recommendations2. Health effects of radiation

2.1 Somatic effects

2.2 Genetic effects2.3 Other carcinogenic and mutagenic agents

3. The nuclear fuel cycle3.1 Mining, extraction and milling

3.2 Enrichment3.3 Fuel fabrication3.4 Power reactor operation3.5 Fuel reprocessing

3.6 Waste management

3.7 Transport4. Health and safety regulations of the nuclear fuel cycle5. Radioactive waste management

5.1 Highly active waste from fuel reprocessing5.2 Other highly active solid waste5.3 Medium and low activity solid waste5.4

5.5

Medium and low activity liquid wasteDischarges into the atmosphere

6. Siting and decommissioning of nuclear facilities6.1 Siting6.2 Decommissioning

7. Accidents in the nuclear fuel cycle7.1 Power plant accidents7.2 Transport accidents7.3 Accidents in fuel reprocessing plants7.4 Accidents during disposal of high -level radioactive waste.7.5 Procedures for mitigating the consequences of accidents ... .7.6 Non -radiation occupational accidents in nuclear power

production

Page

5

6

11

12

13

14

16

16

16

21

21

21

21

23

23

26

27

32

33

33

3436

36

36

38

38

42

43

43

44

44

3

8. Radiation exposures from normal operation of the nuclear fuelcycle 44

8.1 Construction of installations 46

8.2 Mining and milling 46

8.3 Fuel fabrication and enrichment 50

8.4 Reactor operation 50

8.5 Fuel reprocessing 51

8.6 Transport 52

8.7 Waste storage 52

8.8 Decommissioning of nuclear facilities 53

8.9 Accidents to nuclear plants 53

8.10 Total radiation exposure from nuclear power programmesand consequent effects 53

9. Environmental effects 54

9.1 Thermal effects 54

9.2 Chemical waste 56

10. Proliferation of nuclear explosives, sabotage and terrorism 56

11. Consideration of health effects from nuclear and alternativeenergy production systems 58

11.1 Public health effects 58

11.2 Occupational health effects 60

11.3 Radioactivity from plants utilizing fossil fuels 61

11.4 Environmental impacts 61

11.5 Alternative energy production systems 62

11.6 Conclusions 62

12. Public information 63

References 64

Annex I Definitions of "risk ", "detriment ", and "collective dose" 72

Annex II Participants 7

4

INTRODUCTION

The Regional Office for Europe of the World Health Organization, at therequest of, and in collaboration with, the Government of Belgium, convened aWorking Group in Brussels, 1 -5 December 1975, to study, discuss, andappraise the effects of nuclear power industry on man and the environment.One of the reasons for the meeting is the concern of the general public aboutthe safety of nuclear power generation. This report, which is based on thecollective knowledge and experience of the members of the Working Group,as well as on the available literature, provides some guidelines for publichealth authorities. It was not the purpose of the Working Group to expressany opinions on the advisability of the construction of nuclear power facili-ties.

The meeting was attended by 19 temporary advisers from 12 Europeancountries and from the USA. Six major disciplines (health administration,health physics, human biology, human genetics, environmental science andtechnology, and nuclear engineering) and five professional categories (physi-cians, biologists, engineers, physicists and chemists) were represented, thusensuring a multidisciplinary approach to the discussions. Representativesfrom five international governmental and nongovernmental organizationswere also present. The temporary advisers acted in an individual capacity andnot as representatives of their countries or organizations.

The Working Group reviewed the experience gained from building andoperating nuclear facilities and made estimates of the attendant health risks.The Group also considered estimates of the risks associated with the genera-tion of electrical power from other types of fuel. It was agreed to accept thedefinition of "risk ", "detriment ", and "collective dose" as given in full inPublication No. 22 of the International Commission for Radiological Pro-tection (ICRP) (see Annex I). The Working Group discussed the magnitudeof these risks to the general population and to workers in the nuclear powerindustry.

Attention was focused on:

(a) the radiation risks to man, both somatic and genetic, and the environ-mental aspects of the nuclear fuel cycle, from the mining of uranium to thefinal stages of decommissioning a nuclear plant and the storage and disposalof radioactive waste products;

(b) the likelihood and consequences of nuclear and non -nuclear acci-dents, sabotage, and theft of nuclear material.

The Working Group considered measures to protect the population,(including safety regulations and emergency procedures following an accident);

5

technical and administrative procedures on both the national and internationallevels; education and training of personnel in the nuclear power industry; andpublic information.

A quantitative evaluation of radiation risks for workers and the generalpopulation, as well as non -radiation occupational fatalities in the variousstages of the nuclear fuel cycle, was incorporated in a summary table (Table 9)as a function of power output.

Dr B. Lindell was elected Chairman, Dr E. Komarov, Vice -Chairman,Dr J. Schubert, Rapporteur, and Dr P. Czerski, Co- Rapporteur. Dr M.J. Suessacted as Scientific Secretary.

The conclusions and recommendations of the Working Group are givenin section 1 of the report. The programme of the meeting, a list of workingdocuments, and a list of participants are given in Annexes II, III and IV,respectively.

On the basis of a preliminary draft drawn up by the Rapporteur and thecomments of the members of the Working Group on this preliminary draft,a drafting committee, consisting of Dr Dgiderlein, Dr Lister, and Dr Schubert,prepared a draft final report. The Group members subsequently reviewedthis draft, and their comments were taken into consideration by the draftingcommittee in preparing the final version.

1. CONCLUSIONS AND RECOMMENDATIONS

In their discussions, the members of the Working Group drew upontheir collective experience and numerous sources of information in evalu-ating the health implications, hazards and problems involved in the differentstages of the nuclear fuel cycle. They kept in mind public health aspects atnational and international levels. Subsequently, they formulated the followingconclusions and recommendations regarding the generation of electricity bynuclear power reactors.

1.1 Comparative effects of nuclear and alternative energy sources

Quantitative analyses of the effects of the nuclear power industry on thehealth and wellbeing of individuals and populations must be assessed in com-parison with the corresponding effects of alternative energy sources (presentand future). In such assessments, data should be treated on an equivalentbasis, i.e., for equal energy output and for the complete cycle of operations.

Since knowledge of the health effects of alternative sources of energy(for example, fossil fuels) is generally less precise than that of radiationeffects, available information should be critically reviewed and appropriateresearch conducted on the health effects of alternative energy sources.

6

1.2 Radiation exposure

Radiation exposure of workers in the nuclear power industry is generallykept well within the dose limits recommended by the International Commis-sion for Radiological Protection (ICRP). Future exposure of the generalpublic to radiation from all phases of nuclear power production can remainfar below the limits recommended by ICRP. It was anticipated that exposuresper megawatt of electricity per year (MW(e)a) in the future can and will bereduced by using the available technology.

The Group identified the activities in all phases of nuclear power produc-tion which are expected to have health consequences to man. The more im-portant ones are:

(1) occupational accidents, not involving radiation, during mining andconstruction;

(2) whole -body radiation exposures of workers in reactor and fuelreprocessing operations;

(3) radiation doses to the lungs of uranium miners;

(4) the collective radiation dose to the world's population due to therelease into the atmosphere of long -lived gaseous radionuclides, particularlyfrom carbon -14 compounds. Technology for the reduction of the release into

of carbon -14 and other long -lived radionuclides is beingdeveloped, and its use, in due course, should be encouraged.

The average radiation exposures to local and global populations fromnuclear power production, even at a high level, are low compared with theaverage levels of exposure from natural sources or medical practices.

The annual collective radiation dose to radiation workers in nuclearpower plants is greater than that to the general population. Most of theradiation dose to the workers occurs during inspection of structural compon-ents, maintenance and repair work. The Group agreed that it was neitheracceptable nor desirable that radiation exposure from such activities bereduced by decreasing the frequency of this type of work. Only a relativelysmall reduction in terms of manrem per MW(e)a may be attainable.

Whereas the collective occupational radiation doses per MW(e)a asso-ciated with reprocessing plants have been high in comparison with thoseresulting from the operation of nuclear reactors, there is no reason for accept-ing this situation. With improved design of reprocessing plants, these higherdoses can be reduced to the lower levels attained in reactor operation.

1.3 Genetic -somatic effects and epidemiological needs

After reviewing the various factors involved in exposure to radiation andcancer induction, induced mutation rates, and induction of chromosomal

7

aberrations, the Working Group concluded that a linear relationship stillserves best for purposes of radiological protection. Indeed, there is increasingevidence that the use of such a relationship might not overestimate the risk tothe degree thought earlier.

Current estimates of radiation- induced genetic effects are based onexperimental data obtained in mammals, largely under conditions of low doserate exposure where repair of premutational damage is expected already tohave taken place. These experimental data support the concept of linearity inthe dose range relevant to radiation protection and give no indication of thepresence of a threshold dose.

In view of the uncertainties inherent in the use of data from animalexperimentation for quantitative prediction of effects in human beings, theimportance of continued support for epidemiological studies in human popu-lations with special characteristics was emphasized. It is also important thatnational health statistics be used, after careful scrutiny, to evaluate possiblegenetic and somatic effects of radiation and other environmental factors.

The development and use of biological monitoring methods (cytologicaland biochemical) should be encouraged.

There is need for continuing international initiative and cooperation indeveloping such programmes under WHO guidance.

1.4 Radioactive waste

With respect to the storage and disposal of long -lived highly active waste,it was concluded that, although the present practice of using modern,specially designed containers for storing this waste in liquid form had provedsafe, long -term safety could be further improved by converting this liquidwaste into a solid form. There is a genuine need for further development andtesting of processes for this purpose.

A number of options are available for the final disposal of this waste,but the lack of any immediate need for deciding and acting upon a methodallows time for proper and thorough evaluation of these options. Suchevaluations should proceed, but pressures to take rapid decisions that mighteventually prove to be premature should be resisted.

The management of large volumes of solid contaminated materials,e.g., contaminated equipment, requires continued attention.

The dumping of conditioned low -level solid waste into the deep oceanunder the control of the Nuclear Energy Agency of the Organisation forEconomic Co- operation and Development (NEA /OECD) is at present practisedon a small scale in relation to limits now under review by the InternationalAtomic Energy Agency (IAEA). The Group called for the acceleration ofacceptance of IAEA recommendations on procedures as requested in the

8

Final Act of the Intergovernmental Conference on the Dumping of Wastesat Sea, London, 13 November 1972 (known as the London Convention) .a

The Group discussed the effects on man and the aquatic environment ofdischarges of radioactive substances into fresh water and the sea. The effectsdepend on the quantities, nature and conditions of the discharge, particularlyon the radionuclides concerned, and the degree of initial and final dilution inthe water mass. Particular attention must be given to the possible effects onman through various exposure routes, e.g., food chains, rather than on thepossible (temporary) effects on aquatic populations.

It is important to establish the predominant exposure routes to manthrough bioaccumulation or external radiation before major discharges aremade, and to carry out and publish the results of appropriate monitoringprogrammes. Current and predicted discharges to the marine environmentconstitute only a minute addition to its total natural levels of radioactivity.

1.5 Chemical waste

The Group discussed the control of non -radioactive chemical wastegenerated during various stages of the nuclear fuel cycle. Although chemicaleffluents are controllable, within and outside the plants, available technologymay not always be utilized to the best advantage. The control of many non-radioactive chemical effluents is also a public health, environmental and regu-latory problem in the conventional chemical industry.

1.6 Thermal effects

The Group discussed various aspects and consequences of the dischargeof heated water from nuclear power plants. This discharge is not differentin kind from that produced by conventional power plants, except that anuclear power plant discharges somewhat more heat per unit of energy pro-duced. Since both harmful and beneficial ecological effects may occur, theoverall consequences of thermal discharges for any specific reactor locationmust be carefully assessed.

1.7 Siting

The Group considered various factors which govern the siting of nuclearreactors, including the population density around the reactor. It was empha-sized that siting can never be a substitute for sound design, construction andoperation.

a The London Convention came into force in 1975 and the IAEA ProvisionalDefinitions and Recommendations were accepted as operative for the purposes of theConvention by the contracting parties in September 1976.

9

1.8 Decommissioning

Detailed studies are being made on the decommissioning and dismantlingof reactors and plants, and several pilot plants have already been decommis-sioned and dismantled without considerable problems. I lowever, such opera-tions inevitably produce large amounts of low- activity waste. The inclusion ofa requirement for safe and efficient decommissioning in the planning anddesign of future nuclear facilities is desirable_

1.9 Accidents

The Group saw no reason to dissent from the general conclusions of thesafety analyses of nuclear power plants recently carried out in a number ofcountries. All of these analyses assess the risk to the public from accidentsinvolving releases of radioactivity from the reactor core to the environmentto be low. Whereas many small accidents might occur, their impact would bemore in terms of loss of generating capacity, financial penalties and emotion,than of physical harm.

For the assessment and treatment of possible injury caused by high dosesof radiation or by the intake of potentially harmful amounts of radioactivematerials, there is a need for planned collaboration of various disciplines(medical, dosimetric, analytical) and the establishment of necessary linkswith specialist services outside the organization involved, which would varywith the type and severity of injury foreseen.

It is important that public health authorities be involved in establishingand reviewing emergency arrangements which would apply following anaccident serious enough to involve the evacuation of residents for radio-logical protection purposes.

1.10 Sabotage and terrorist acts

Although there is no way of obtaining absolute assurance againstterrorist thefts of radioactive materials (which might be used for the produc-tion of a weapon) or against sabotage of a nuclear plant, any risk to the pub-lic from such acts would not contribute substantially above that already exist-ing in contemporary society from other similar threats.

Reducing the rate of nuclear power development would not substan-tially reduce the overall possibility of terrorist threats. However, it is impor-tant to continue efforts to minimize the possibility of risk from plutoniumdiversion and from sabotage against nuclear plants.

1.11 Public information

It is important to keep the public currently and fully informed onthe likely consequences of operating nuclear power plants, as well as on

10

comparisons with alternative power production sources. Public health autho-rities would be expected to participate in the dissemination of such informa-tion. Contacts established with the general public should continue after con-struction of these plants.

International organizations should play an important role in the dis-semination of information on nuclear energy and should contribute to thegeneral awareness and confidence of the public.

1.12 Inspection and personnel training

In addition to the routine inspections of nuclear operations which arecarried out by the operators of the facility, the practice of independentchecks should be continued.

The education and training of personnel was discussed. Operators andother personnel involved in nuclear reactor operations should be technicallycapable and stable persons. The competence of operating personnel should atleast be maintained at the present level.

2. HEALTH EFFECTS OF RADIATION

The biological effects of ionizing radiation on organisms are describedin numerous publications, including handbooks on radiobiology, monographs,and compilations such as those in references 1 and 2. Radiation can produceharm when arising from sources outside the body or originating from radio-active isotopes deposited within the body (1,2,3,4,5). The acceptable levelsto man of individual radionuclides are based not only on calculations of dosedelivered, but on well -established data derived from human epidemiologicalsurveys and on relatively high doses given to experimental animals.

Radiation can cause acute (short-term) or long -term health effects.The acute effects are manifested immediately or within days or weeks follow-ing exposure. The long -term effects are not manifested before many yearsafter the radiation exposure. There are several types of long -term effects,including malignant diseases in the exposed individual, abnormal develop-ment following irradiation of the foetus (somatic effects), and inheritedabnormalities in the descendants of the exposed individuals (genetic effects).There is no evidence at low doses of any life shortening in man from causesother than the induction of fatal malignant diseases.

The frequency with which long -term effects may be induced per unitdose of radiation has been estimated, including those resulting from nuclearpower programmes, on the basis of a substantial body of experimental andepidemiological data (e.g., references 2, 5, 6, 7).

11

2.1 Somatic effects

When whole -body radiation is delivered in a short period of time(minutes or hours), the dose of radiation which could kill 50% of the personsirradiated (the LD 50) has been estimated at 250 -450 rad. However, theseacute effects would only occur in case of highly unlikely accidents (seeSection 7). In normal circumstances, radiation exposures (controlled inaccordance with internationally accepted protection standards) amount to atmost a few rad per year.

Under these circumstances the main somatic radiation hazard, apartfrom that to the embryo, is the induction of malignancies, including leukae-mia. At very low doses, it is cautiously assumed that the risk of cancer in-duced is simply (linearly) proportional to radiation dose. Estimates canthereby be made of the maximum likely risk of a fatal or non -fatal cancerbeing induced by applying this dose /risk relationship to the estimated averageirradiation of populations (such as might result from nuclear power produc-tion) from both more or less uniform irradiation of the whole body and fromlocal organ exposures.

Observations on the effects of radiation in humans have been made infollow -up studies on persons who have received radiation for medical diag-nostic or therapeutic purposes, studies of survivors of the attacks on twoJapanese cities (8), epidemiological studies on populations in areas of highnatural background radiation (9,10,11,12,13) and on groups of personsexposed in the course of their work (14). The actual incidence of radiation -induced cancer depends on many factors, especially age, because of the longdelay between radiation exposure and cancer; this can exceed 30 years.

An upper limit to the risk of inducing malignant disease by largedoses of radiation, in the region of 100 rad or more (delivered in a shortperiod of time), can now be estimated from a number of epidemiologicalsurveys of human populations followed for prolonged periods of time afterknown radiation exposure. These indicate total risk rates of fatal cancerinduction in the region of 100 to 150 cases per million persons exposed toone rad of whole -body exposure. The additional risk of non -fatal (or curable)cancer is likely to be lower.

At the much lower dose levels of a few rad (occupational) or a fewmillirad (general population) exposure per year, there is no adequate evidenceof the risk rate per rad, and those quoted may overestimate the risk per radat these low doses and dose rates. There is no direct evidence of any risk ofcausing other diseases at these dose levels.

The evidence for the induction of malignancies at low radiation doseshas been reviewed many times, e.g., in the 1972 BEIR report (2). This evi-dence has been recently examined (15); the available data for minimum dosesproducing a detectable increase in the induction of malignancies in humansare summarized as follows: (1) thyroid cancer in children at estimated

12

mean doses of about 6 rad; (2) malignancies following exposure of thefoetus, probably at mean doses of a few rad; and (3) leukaemia in the sur-vivors of Hiroshima and Nagasaki exposed to doses of less than 10 rad. Areasonably dependable estimate for radiation carcinogenesis is that for everycase of induction of leukaemia 4 -5 other malignancies will eventually occur.

2.2 Genetic effects

The genetic effects of ionizing radiation have been known for nearlyhalf a century in a large number of organisms, from microorganisms to plantsand higher animals. Regardless of species, the genetic effects of radiation, as ofchemical agents, involve attack on DNA, the essential component of the genes.

It is well recognized that the incidence of diseases with a partial or fullgenetic component is significant in human populations (16,1 7). It appearsthat some 6% of all liveborn children have diseases of genetic origin, dividedas follows:

(1) 1% dominant and X- linked diseases;(2) 1% chromosomal and recessive diseases; and(3) 4% congenital anomalies and constitutional and degenerative

diseases.More recent data (18) present substantially lower figures for dominant dis-eases and higher values for the third category (congenital anomalies andother multifactorial diseases).

An increase in the mutation rate in humans from any source would bea matter of concern. It is assumed that the dominant or X- chromosome- linkeddisease would increase in proportion to the mutation rate, i.e., it is assumedthat there is a linear relationship between the radiation dose and the fre-quency of radiation induced genetic diseases. The increase in the mutationrates for recessive diseases is very small, requiring scores of generations toreach an equilibrium value (Table 1). The best estimated value for the doub-ling dose for protracted radiation exposure is now considered to be 100 radfor both sexes (7). Estimates of the effect of 1 rad per generation on a popu-lation of 1 million, assuming a doubling dose of 100 rad, are given in Table 2.

Estimates of genetic damage to man from any type of mutagenic agentinvolves assumptions about dose -effect relationships in low dose and lowdose -rate regions. Although precise calculations of genetic damage from radia-tion, among other mutagenic agents, may not be attainable, it is necessaryand possible to make simplified estimates of the probable level of geneticeffect (2, 7). Dose -rate data for specific locus mutation induction in micegive a reasonably close approach (at less than 0.8 rad min-1) to a linear dose -effect curve. Some acute exposures have a higher effectiveness, some a lower.The mechanisms causing variation in effectiveness are not known. As a basisfor risk estimates, however, the linear regression based on the low- dose -ratedata can be used, with suitable adjustment for acute exposures.

13

Table 1. Effect of a doubling in mutation rate from 10 6 to 2 X 10.6 a

Type ofdetrimental gene

Number of affected individuals (per 106)

Oldequilibrium

After onegeneration

Newequilibrium

Recessive;fitness of as =0

Semi dominant;fitness of Aa =0.9of as =0

Dominant;fitness of Aa =0

Sex linked;recessive fitnessof aa and aY =0

1 aa

20 Aa

2 Aa

3 aY males

1.002 aa

22 Aa

4 Aa

4 aY males

2 aa

40 Aa

4 Aa

6 aY males

a After Ramel (19).

As the average "child expectancy" (of having children subsequently)falls rapidly after the age of 30 in both sexes, gonadal radiation exposure isnot of the same "genetic significance" at all ages. When the total risk ofsignificant inherited abnormalities is estimated, therefore, the age distribu-tion of the irradiated population must be taken into account.

Per rad of exposure, the risk of inducing any serious inherited abnor-mality is estimated as being in the region of 10 -4 (in the first two generations)or 2X 10-4 to 3 X10-4 (in all generations) of the fraction of the radiationexposure which is of genetic significance. For the general population, thisfraction is in the region of 0.5 of the total exposure; for occupational expo-sures it is about 0.25.

2.3 Other carcinogenic and mutagenic agents

Many factors, other than radiation, including exposure to a growing num-ber of chemicals, are now recognized to be carcinogenic and mutagenic (19).In the opinion of the International Agency for Research on Cancer (IARC),approximately 80% of all cancer cases have an environmental cause, whereaseven higher figures are quoted by others (20). Most of the relevant environ-mental factors are likely to be man -made or naturally occurring chemicals.Although the world's exposure to potentially carcinogenic and mutagenicchemicals is growing, a quantitative comparison of the relative effects of

14

Table 2. Estimated effects of 1 rad per generation of low dose, low dose -rate,low -level irradiation on a population of one million live births if

the doubling is 100 rada

Disease

classificationbCurrent

incidence

Effects of 1 radper generation :first generation

incidence d

Equilibriumincidence

Autosomal dominant andX- linked 1 000 - 10 000e 2 - 20f 10 - 100f

Recessive diseases 1 100 Relatively slight Very slowincrease

Chromosomal diseases 6 000g ? ?

Congenital anomaliesAnomalies expressed laterConstitutional and

degenerative diseases

90 100b 5 - 45' 45 - 450'

Total 98 200 - 107 200 10 - 701 60 - 600g

% of current incidence 0.01 - 0.07 0.06 - 0.6

a After San karanarayanan (7).b Follows that given in BEIR report (2).

c Current incidence values based on Trimble & Doughty (181 with certain modi-fications.

d The first generation incidence is assumed to be about 0.2 of the equilibriumincidence for autosomal dominant and X- linked diseases; for those included under theheading "congenital anomalies, etc." it is 0.1 of the equilibrium incidence.

e The low value of 1 000 is based on Trimble & Doughty (18) and the high valuesof 10 000 on Stevenson's used in the 1972 UNSCEAR (51 and BEIR reports (2).

f The low and high values are based on current incidences of 1 000 and 10 000respectively.

g Based on pooled values from 7 surveys of new -borns; includes mosaics.h Includes an unknown proportion of numerical (other than Down's syndrome) and

structural chromosomal anomalies.

' The range reflects the assumption of 5 and 50% mutational components.

Rounded off values.

15

chemical agents and radiation is not yet possible because of a lack of informa-tion on the former. The information presented later in this report suggeststhat, with continuation or improvement of present radiation protectionpractices, it is unlikely that radiation from present and projected nuclearpower programmes will contribute a major fraction of the total carcinogenicand genetic effects observed.

3. THE NUCLEAR FUEL CYCLE

The term "nuclear fuel cycle" refers to the sequence of processesthrough which the materials used in the production of nuclear energy pass.It covers all steps from the mining of uranium ore to the conditioning, storageand final disposal of the waste materials; the intermediate stages are uraniumextraction and milling, enrichment of the fissile uranium content, conversionto fuel, fabrication of the fuel elements, irradiation in the reactor, separationof the unused fuel from the products of the nuclear reaction and its reconsti-tution into fuel. These stages, in each of which potential exposure of workersand public to radiation must be controlled, are illustrated in Fig. 1 and 2 anddescribed briefly in the following paragraphs (see also reference 21). As in theremainder of the report, attention is focused on the nuclear fuel cycle forthermal reactors.

3.1 Mining, extraction and milling

Uranium occurs relatively widely in nature, although it forms only about2X 104% of the earth's crust. The largest resources are in North America,southem Africa, Australia and Sweden. Present commercial ores typicallycontain between 0.1 and 0.3% of uranium and are converted into a concen-trate known as "yellow cake ". The well- documented hazards of uraniummining, which are dealt with in Section 8, must not be overlooked in anyassessment of the health consequences of the nuclear fuel cycle.

3.2 Enrichment

Many reactors have been designed to operate with uranium fuel with itsfissile uranium -235 content artificially enriched. Enrichment is now carriedout by a diffusion process after conversion of the uranium into a volatilecompound (the hexafluoride). Alternative processes being developed commer-cially include use of the gas centrifuge.

16

Fig. 1. The main stages of the uranium nuclear fuel cycle

Enrichment

Mining, extractionand milling of

uranium

1

Plutonium

Conversion to fuel

f

Fabrication offuel elements

i

Power reactoroperation

Irradiated fuel

Storage

Uranium

Fuel rep ocessing

Waste productsstorage /disposal

17

Fig. 2. The fuel cycle of a 1 000 MW(e) uranium -fuelled water -reactor power planta00

Input16 acres85,700 MT ore2.54x106 MT overburden Mining

(Open - Pit)0.2% ore

12.54 x 106MT overburden

Gaseous56.7 Ci Rn2220.0226 Ci Ra2260.0226 Ci Th2300.0334 Ci U15.0 MT NOx

Gaseous Gaseous9.43 MT NOx 12.21 MT NOx0.11 MT fluorides 0.69 MT fluorides25.7 MT SO2 22.4 MT SOx0.0132 Ci U 0.002 Ci U

EnrichedIsotopeMilling

and ConversionSeparation Uranium

(as UF6 )Concentration U308 -UF6 ( separative

work-172 MT)U (as U30e) U (as UF6) 34.53 MT U2.7 acres 171.4 MT 2.4 acres 171.4 MT 3.3% U235

0.71% U235 1.2 acres

Solid tailings86,200 MT53.5 Ci Th2 0

Ra226

Liquid1.9 Ci U0.051 Ci Ra2263.20 Ci Th230

(T

Elec. Energy )

(j 4.20x108 kwh

Liquid0.027 Ci U0.025 Ci Th'0.25 Ci Ra226

Liquid:Ci

Recycled uranium(as UF6)

33.04 MT0.798% U235

rDepleted uraniumstored os UF6170 MT 0.2% U23656.3 Ci

56.6 Ci 0.029 USolid: 37.7 MT ash 24.4 MT NaCIStored solid: 7.91 MT Ca+0.26 Ci Th -U 7.91 MT SOqin 15.5 Kg ash 0.52 MT Fe

3.96 MT NO3

Note. The quantities were calculated assuming operation for one year at 100% load factor. The material quantities assume an equi-librium annual reload cycle with each fuel element operating 1100 full -power days prior to discharge, corresponding to an averagethermal energy generation of 33 000 MW(e)d per ton of uranium and an average thermal power of 30 MW(e) per ton of uranium. Thereactor is refuelled by a programme of partial batch uranium, in which one third of the reactor is replaced with fuel each year. The freshfuel contains uranium enriched to 3.3% uranium -235.

Fig. 2 (continued)

EnrichedUranium(as UF6)

34.53 MT U3.3% U235

.0

Gaseous5.18 MT NO38.29 MT NH30.39 MT fluorides0.00019 Ci U

Conversionand

Fabrication

FabricatedFuel

34.53 MT U3.3% U

Liquid0.0196 Ci U0.0098 Ci Th23

33.8 MT solid CaF20.059 Ci U in CaF20.024 Ci other U

Makeup water

ElectricalEnergy:8.76x109 kwh

Transmission Delivered Electrical Energy:7.984x109 kwh

Transmission Losses: 0.7761109 kwh

Boiling PressurizedWater Water

Gaseous Reactor Reactor

H3 10 to 50 Ci1131 0.3 to 0.8 CiKr + Xe 50,000 7000 Ci

NuclearSteam- Electric

Generating Plant

1000 Mwe32% Thermal EfficiencyP ant area: 160 ocres2738x101° kwh /yr

Circulating water966,000 gal. /min.

Cooling Tower

19,230 gal. /min.

IrradiatedFuel

33.044 MT U0.296 MT Pu5.17x109 Ci

Storage ofIrradiated

Fuel

150 days33.044 MT U0.296 MT Pu1.35x108 Ci

Liquid radioactive discharge

Shipment ofIrradiated

Fuel

Blowdown water: 7210 gal. /min.7180 MT dissolved solids

BWR PWRH3 90 450 CiOther 5 5 Ci

Humidified air: 23.0x106 MT H2O evaporated1.86 x 1010 kwh waste heat

Drift: 483 gal. /min.481 MT dissolved solids

Fig. 2 (continued)

Surface Water3340 Ci H33.67 Ci Ru1065.03 MT Na'0.23 MT CI-0.415 MT SOâ0.176 MT NO3

ShippedIrradiatedFuel

Gaseous.Ci Kr85

20,580 Ci H30.06 Ci 1129, 1310.918 Ci other F.P.0.0037 Ci transuranics7.4 MT NOx

Reprocessing

3.7 acres

High -levelWastes

Process water9 gal. /min.

1.32x108 Ci F.P.0.0015 MT Pu20,500 Ci Pu11,400 gal. if liqu d114 cu.ft. if solidCladding hulls:4.28 x106 Ci72 cu.ft.

Interim( 5 -year )Storage ofHigh Level

Wastes

High -levelWastes

1.83x107Ci F.P.114 cu. ft.Cladding hulls:1.67x105 Ci72 cu.ft.

Intermediate -level ( 104 to 106 x MPC 1liquid wastes to storage: 6900 gal.

> Low -level ( 10 to 104 x MPC )liquid wastes: 340,000 gal.

Buried solid wastes: 6900 cu.ft.: 0.14 acres

Sole, recycle or storagePu (as Pu( NO3 )4 )0.296 MT

Y

4.09x106 Ci

t 33.04 MT U, 0.798% U

Shipmentto

FederalRepository

High -levelWastes

1.83 x107 F.P.114 cu. ft.Cladding hulls:1.67x103Ci72 cu.ft.

PerpetualStorage ofHigh- Level

Wastes andOther Wastes

Storage Area:0.2 to 1.6 acres

a After Pigford (22). Reproduced, by permission, from Annual review of nuclear science, volume 24. Copyright ©1974 by AnnualReviews Inc. All rights reserved.

3.3 Fuel fabrication

Uranium from the ore concentrate, or uranium hexafluoride after enrich-ment, is converted by a series of chemical reactions into oxide or metal. Inone or another of these forms it is loaded into metal tubes (cladding), whichare filled with gas and sealed. The filled tubes, either singly or in clusters, areassembled into fuel elements for insertion into the nuclear reactor.

3.4 Power reactor operation

In the core of a nuclear reactor the process of fission (splitting) of theatoms of fuel by neutrons produces heat and a range of lighter elements(the fission products), most of which are radioactive. In an additionalreaction, atoms heavier than uranium are produced (the transuranic elements,including plutonium, americium and curium), which are also radioactive andare of special importance in the nuclear industry. The amounts of transuranicelements formed are summarized in Table 3. In normal operation the pro-ducts of the nuclear reaction are retained within the cladding of the fuelelements. Spent fuel elements unloaded from reactors are stored in heavilyshielded areas; they require cooling for some time until the radioactivity ofthe irradiated fuel has fallen substantially by natural radioactive decay.

3.5 Fuel reprocessing

If the waste products and the plutonium are to be separated from theunburnt fuel, the spent fuel containing these materials is transferred afterseveral months to a reprocessing plant in massive, thick -walled containers.There the fuel is dissolved in acid and the solution is treated chemically toseparate it into a number of streams. One stream contains the unuseduranium, which is recovered to make new fuel. The second stream containsthe bulk of the plutonium, which can be kept for future use in fast reactorsor for recycling in thermal reactors. The third stream contains the fissionproducts and most of the other transuranic elements; this is highly radio-active waste. The chemical separation process is carried out remotely in plantsequipped for safe handling of the highly radioactive materials.

3.6 Waste management

As in all industrial processes, including most methods of producingpower, a variety of waste materials is produced at various stages of the fuelcycle. National and international bodies concerned with health and safetyhave made recommendations and established procedures for managing thiswaste (23) without undue risk to the general population or the workers inthe nuclear industry. The different kinds of waste produced and their presentand future management are discussed in greater detail in Section 5 of thisreport.

21

Table 3. Annual amounts of transuranic elements in the fuel cycle of 1 000 MW(e) nuclear reactors(80% load factor)a

Occurrence Element

Uranium -fuelledwater reactor

Uranium -plutoniumfuelled water reactor

Fast breederreactor

kg /a Cita kg /a Cita kg /a Cita

In fuel processing Plutonium 2456 1.06X 105(a) 1 573c 6.78 X105 (a) 1 970d 4.49 X 105(a)3.1 X106(0) 3.1 X107(13) 1.3 X107(0)

Americium 4.39 6.36X 103 (a) 75.7 1.126X 105 (a) 17.8 3.82 X104 (a)1.10X 102 (ß) 2.65 X103 (ß) 1.869X 103 (ß)

Curium 0.926 3.80X 105 (a) 9.73 3.65 X106 (a) 0.676 1.12 X106 (a)

Net productionin reactor Fissile plutonium 172 - ( -304)e - 132 -In fuel fabrication Plutonium 0 - 1 958 - 1 757 -

a After Pigford (22).

6 1.8% Pu-238, 59.3% Pu-239, 24% Pu-240, 11.1% Pu-241, 3.8% Pu-242.

1.9% Pu-238, 34.2% Pu-239, 31.4% Pu-240, 18.5% Pu-241, 13.9% Pu-242.

d 0.77% Pu-238, 66.9% Pu-239, 22.4% Pu-240, 6.1% Pu-241, 3.8% Pu-242.

e Required make -up from uranium -fuelled water reactors.

3.7 Transport

Continued geographical separation of facilities for different stages of thefuel cycle will require an increasing number of transport operations involvingnuclear materials. Transport of raw fuel materials and fresh fuel assemblies donot entail significant radiation risks, whereas transport of irradiated fuel andseparated products of the nuclear reaction have a higher potential for acci-dents which could involve exposure of workers or members of the generalpopulation (see Section 7). Co- location of power plants with fuel fabricationand reprocessing plants would reduce but not eliminate transport operations.

4. HEALTH AND SAFETY REGULATIONS OF THENUCLEAR FUEL CYCLE

In all countries using or planning to use nuclear power, there are exten-sive regulations, rules, and codes of practice for protection of workers and thepublic.

International bodies, e.g., the International Commission for RadiologicalProtection (ICRP), provide recommendations on health protection standards(e.g., 24), which serve as bases for national regulations adapted to national andlocal conditions. These recommendations (examples of which are shown inTables 4 and 5) derive from extensive world -wide research and experience onthe effects of radiation on man, on metabolic behaviour and on studies of dis-persion and /or concentration of radioactive substances in air, water and foodchains. The scientific bases for these and other radiation -related recommenda-tions are kept under constant review by international bodies such as the UnitedNations Committee on the Effects of Ionizing Radiations (UNSCEAR), ICRPand IAEA. Continued international cooperation on radiation protection isimportant, as the distribution of some materials released from nuclear facilitiesadds to levels of radioactivity on a world -wide basis.

Other international actions relating to the protection of the public in-clude the Treaty on the Non- Proliferation of Nuclear Weapons, covering thepeaceful uses of fissile materials, and the London and Oslo Conventionson the disposal of low -level radioactive waste at sea. Other relevant materialis provided in IAEA publications (e.g., in references 25, 26, 27, 28, 29, 30).

In most countries the formulation and enforcement of detailed regula-tions and carrying out national reviews of radiation exposure are the respon-sibility of national radiation protection institutions or special nuclear regula-tory or inspection bodies.

A basic principle in formulating radiation protection regulations is theICRP recommendation that all radiation exposures be kept as low as readily

23

Table 4. Maximum permissible annual radiation doses recommended byICRP for occupational exposure'

Organ irradiated Dose (rem)

Whole -body )

Bone marrow ) 5

Gonads

Skin and boneThyroid gland

1 30

Hands and forearmsFeet and ankles

)

)

Other single organs 15

Note. Values for individual members of the population (except for the thyroid glandof children up to 16 years of age when the limit is 1.5 rem /a) are 10 times lower andfor exposed populations 30 times lower than those for occupational exposure.

a After International Commission on Radiological Protection (31).

achievable, economic and social considerations being taken into account (32).In the nuclear industry all stages of the nuclear fuel cycle must be considered.For members of the general population, direct measurement of radiationexposure is not practicable, and protection must depend on effective controlof radioactivity releases at the source. Following discharges of radioactivematerials with half -lives of days or longer, these materials may travel large dis-tances in air or water. Regulations and dose assessments must therefore con-sider the collective dose to national, regional and global populations. In manycases, regulations are also framed to provide for future expanded use ofnuclear power.

Regulations covering general industrial activities (site permits, buildingpermits, water discharge permits, boiler codes, etc.) also apply to nuclearfacilities, where applicable. Permits for the erection and operation of nuclearfacilities are only granted by governmental bodies. Governments thereforeexert a more direct control over nuclear power production than over manyother industrial developments. Siting of nuclear facilities is subject to specialregulations and practices. These may, for example, relate to thermal ef-fects of cooling water, seismic activity and local population characteristics,as well as provisions to include public participation in the siting decisionprocess.

24

Table 5, Some environmentally important nuclides associated with thenuclear fuel cycle, their half -lives and ICRP recommended

concentration limits

NuclideRadioactive

half -life

Derived concentration limits for workersexposed for 40 hours per week'

3µCi cm in airpCi cm 3 in water

Soluble materialb Insoluble material

H -3 12.5a 8X10-6 3X10-3 1X10-1(as water vapour) (as gas) c

C -14 5.7X103 a 4X10-6 1X10-7 2X 10-2

Ar -41 1.8h - 2X10-6 C

Kr -85 10.8a - 1X10-5 _c

Sr -90 27.7a 1X10-9 5X 10 -9 1X10-5

Zr -95 65.5d 1X10-7 3X 10-8

2X10-3

Nb -95 35.0d 5X10-' 1X10-7 3X 10 -3

Ru-106 368d 8X10-8 6X10-9 4X10-4

1 -129 1.7X 10' a 2X10-9 7X10-8 1X10-5

I -131 8.1d 9X10-9 3X10-7 6X10-5

Xe -133 5.3d - 1X10-5 -Cs -137 30.0a 6X10-8 1X10-8 4X 10 -4

Np-237 2.1 X 106 a 4X10-12 1X10-1° 9X 10 -5

Pu -239 2.4X 104a 2X10-12 4X10-11 1X10-4

Am -241 458a 6X10-12 1X10-'9 1 X 10 -4

Cm -242 163d 1X10-19 2X 10 -10 7X10-4

a The derived concentration limit, if maintained, will not lead to the relevantmaximum permissible annual dose being exceeded. For members of the general popula-tion the limits are reduced by a factor of 10 for all radionuclides other than iodine,for which the factor is 20. All limits are reduced by a further factor of 3 if exposure isfor the full 168 h w .

b i.e., compounds of the nuclide soluble in body fluids.

Limit is based on external radiation from surrounding airborne gas.

25

The Working Group agreed that, in addition to the usual self- monitoringprocedures of the nuclear industry, the practice of independent inspection bygovernmental organizations should be continued and possibly expanded.

The importance of broad, high -level training of nuclear facility personnelwas emphasized by the Working Group. As in several other industries, mentalstability as well as technical capability are essential criteria in the selectionof personnel (33). The Group also noted the importance of effective trainingof the staff of governmental regulatory and inspection agencies.

5. RADIOACTIVE WASTE MANAGEMENT

In general, there are only two acceptable ways of dealing with waste ofany kind if it cannot be destroyed or is uneconomical to recycle. It mayeither be stored in a safe and well- managed way, or it may be disposed of.In the latter case, physical barriers and natural processes, e.g., dilution effectsor chemical changes, may assist in reducing the environmental impact to anacceptable level. Both storage and disposal are practised in the case of radio-active waste.

It is necessary to maintain a clear distinction between the terms "storage"and "disposal ". Storage signifies the supervised retention of material, isolatedfrom human and other forms of life, but under such conditions that it can berecovered when desirable. Disposal refers, on the one hand, to the discardingof material (in a controlled manner in the case of radioactive waste) with nointention of its ever being recovered; this may be achieved either by deliberatedispersion in the atmosphere, the sea or fresh water, or by isolation from thebiosphere. On the other hand, radioactive decay during storage may so reducethe toxicity of the material that immobilizing it at the site of storage maythen be considered an adequate form of disposal. It is also acceptable incertain cases to ensure the isolation of the waste for long periods followed byslow dispersion when the initial high levels of radioactivity have decayedaway. Storage always involves surveillance of the waste; disposal may involvemore limited surveillance of the disposal site.

If the irradiated fuel is to be reprocessed, its unwanted constituents andthe associated metal cladding and other components of the fuel elements willeventually become waste. If, however, there is no intention to reprocess thefuel, the whole or large parts of the irradiated fuel element itself is treated asa waste material, which must be safely managed.

Classification of radioactive waste depends on a number of factors,including the type of radiation, its activity per unit of weight (specific activ-ity), and the toxicity of the radionuclides concerned, including their half -lives. For examples of definitions see the IAEA Report (34). For convenience

26

in this report the terms "high ", "medium" and "low" have been loosely usedto quantify the activity of the waste, although these terms do not refer toprecisely defined levels of radioactivity. The quantities of waste produced areinfluenced by the type of reactor, its construction, operating conditions, thesite conditions, and by the subsequent treatment of the fuel (for example seeTables 6 and 7). Many publications giving details of waste managementprocedures, which depend on the nature of the materials and the levels ofradioactivity involved, are listed in the references (e.g., 35, 36, 37, 38).

5.1 Highly active waste from fuel reprocessing

Nearly all the highly active liquid waste arises from the reprocessing ofnuclear fuels. The liquid concentrates from the reprocessing plant after theuranium and plutonium have been recovered contain about 99.9% of theresidual total fission product activity. This liquid, which is waste material ofvery high specific activity, also contains small amounts of unrecovereduranium and plutonium and other radioactive transuranic elements (particu-larly americium and curium) formed during irradiation in the reactor. Be-cause of the high toxicity of some of the long -lived radioactive components,the waste has to be isolated from the biosphere for a very long time. At thetime of separation of the waste from the uranium and plutonium, nearlyall of its activity is due to the fission products. Although at first the activityof the fission products falls quite rapidly as the shorter -lived radionuclides

such as strontium -90 and caesium -137(which have half -lives of about 30 years), require isolation for a few hundredyears. By this time, the toxicity of the waste would have decayed by a factorof over a million. Several of the highly radiotoxic isotopes of the transuranicelements contained in the waste have half -lives of thousands of years, andafter a few hundred years they become the dominant hazard (see, e.g., Fig. 3).

Although the fission product activity of the highly active liquid waste(about 109 Ci per 1000 MW(e)a of power produced after one month's stor-age) is largely independent of reactor type, the degree of concentrationachievable and hence the final volume of the liquid waste depends on thechemical separation process used. However, the volume is always very smallper unit of power produced, compared with that of (less toxic) waste fromfossil fuel power production. As an example, the total volume of highly activeliquid waste produced from the United Kingdom nuclear power programmesince its start in 1955 is less than 700 m3 (40). By the end of the century thiscould reach at most 6000 m3 containing 1010 Ci of fission products and108 Ci of transuranic elements. At present, this waste is stored in speciallydesigned, cooled, steel tanks with outer containment. In the more modern,doubly contained, stainless steel tanks, monitoring would rapidly detect anyleak, and spare tank capacity is always maintained. Experience with moderndesigns of tank has led to confidence that this method of storage could besafely continued for many decades.

27

Table 6. Annual production of liquid waste from operation of a 1 000 MW(e) pressurized water reactor (PWR)a

Characterization of the wasteAnnual volume (m3)of untreated waste

Annual volume (m3)of conditioned waste

Cate orgoryActivity(Ci m )

Radioactivecontaminantb

Reactoroperation

Fuelreprocessing

Reactoroperation

Fuelreprocessing

Very low

Low

Medium

High

10s to 10-2

<1

<1 000

>1 000

FP + AP

FP + TU

FP + TU

FP + TU

7 000

4 000

--

-2 000

45

40

4 to 8

20

--

-20

45

4

a Personnel communication from Dr P. Dejonghe.

b FP = mixed fission productsAP = activation productsTU = transuranic elements

The figures given for reprocessing were obtained by estimation of the volumes anticipated for an industrial -size reprocessingplant capable of handling 500 -1 000 t/a of uranium, corresponding to the needs of 15 to 30 PWRs of 1 000 MW(ela. They dependconsiderably on the chemical separation and waste conditioning processes.

Table 7. Summary of rates of discharge of radioactive materials to atmosphere for various reactor types'

Reactor

Discharge rate Ci per 1000 MW(e)a

Krypton -85 Iodine -129 Tritium Carbon -14

At reprocessingplant

At reprocessingplant

Atreactor

At reprocessingplant

Atreactor

At reprocessingplant

PWR

BWR

Magnox

HWR

3X 105

3X105

3X105

3X105

10-2

10-2

10-2

10-2

12

20 -100

--2 104

5X103

5X 103

5X103

5X103

6

15

6

10

1.5

1.5

6

1.5

a After Commission of the European Communities (39).

N

Fig. 3. Relative ingestion radiotoxicity of components of highly active wasteand naturally occurring radioactive pitchblende.a

10

106

104

103

102

10

1

Fissionin

products1g of waste glass

. .</in'

Transuranic1g of waste

elementsglass

Typical1g

forpitchblende

\..,\'10 102 102 104

Age of wastes (years)105

Assumptions: pressurized water reactor fuel, uranium fuel cycle, 1% plutonium inwaste, 15% waste in solidified (glass) material, typical pitchblende toxicity normalizedto unit weight.

a After McGrath (41), additional data for pitchblende provided by Dr B. Skytte-Jensen (personal communication, 1977).

30

Any storage system needs surveillance, but the degree and importance ofsurveillance would be reduced, and the storage of the waste made even safer,if the liquid were converted to a stable solid. In a number of countries rele-vant development programmes are well advanced, the favoured product beinga form of glass which has been shown to be highly resistant to water leaching,to chemical attack and to high levels of radioactivity. Plans are being made tostore these blocks of glass, encased in steel, in a cooled, controlled and moni-tored environment. 1000 MW(e)a of nuclear electricity would result in from1 to 4 m3 of contained vitrified high -level waste, depending upon its decaytime and chemical composition. It has been reported (43, 44) that a nuclearpower programme rising to 100 000 MW(e) installed by the end of the cen-tury would produce, by then, about 3000 m3 of vitrified waste which couldbe stored in water basins covering an area of ground less than 10 000 m2.The Working Group considered it important that the development and testingof solidification processes continue energetically.

There is no technical reason why such methods of engineered and super-vised storage should not be safely applied indefinitely. Even so, various methodsare being developed in several countries for this waste to be disposed of in iso-lation from man's environment without the need for permanent supervision.These studies include examination of burial in deep geological formations, suchas salt domes, clay or hard rock, and disposal in or on the deep ocean bed(42). In Europe the Commission of European Communities (CEC) is coordi-nating a comprehensive programme of work in this field (45).

An illustration of the radiotoxicity of vitrified highly active waste can begained from comparing it with the toxicity of naturally radioactive minerals.Such a comparison is shown in Fig. 3, indicating the relative radiotoxicityof fission products and transuranic elements in the glass and naturally occur-ring pitchblende. All toxicities are evaluated on the basis of data from ICRPand are derived from ICRP recommendations on maximum permissiblenuclide concentrations in drinking- water. It is to note that after some 1000-3000 years the toxicity of the waste material will become (gram for gram)less than that of typical radioactive minerals.

Geological stability at the disposal site is important and it is relevant tonote a recent discovery that 2000 million years ago high uranium concen-trations, in the Oklo mine in Gabon, West Africa, initiated a number ofnatural "reactors" which operated for about a million years (46). Evidenceon the migration away from their site of formation of the tons of fissionproducts and transuranic elements formed by these natural reactors con-firms what would have been expected from geochemical knowledge. Thoseelements which, from their chemical and physical properties, would havebeen expected to remain had done so, and those which would be expectedto be mobile, had moved. There is evidence that plutonium -239 did not mig-rate during its lifetime, and the circumstances were certainly less favourablethan would be expected in a carefully selected disposal site.

31

A number of more exotic suggestions for disposal have been made, suchas firing the waste into space in rockets and burial in the polar ice caps (47).

In principle, it is possible to convert the very long -lived component ofthe waste into shorter -lived or stable materials. If the small amounts of trans-uranic elements associated with the fission product waste could be separatedand used as fuel in a reactor, they would eventually be converted into shorter -lived or stable fission products (nuclear incineration) (48). After a total of30 years of neutron irradiation, 99.9% of the transuranic elements would beconverted to fission products. This approach is theoretically feasible, butdevelopment of the specialized new technology would be lengthy and expen-sive. The processes involved are being examined collaboratively in a numberof countries, but there is no assurance that its application would give anoverall environmental advantage compared with disposal without separation:the introduction of new plants and new processes would inevitably resultin an increase in occupational exposure. Although nuclear incinerationwould substantially remove the long -lived radioactive component of thewaste, it is not a disposal method and should not be looked upon as analternative to the disposal options already referred to.

The Working Group concluded that there are a number of options forthe safe disposal of high level radioactive waste and that no insurmountabletechnical problems have been identified. However, to reach a conclusion asto the best option will involve substantial research programmes. Such pro-grammes and the present trend towards international collaboration shouldbe encouraged. Although for the proper development of nuclear power itwill be necessary to demonstrate the feasibility and safety of any disposalroute, the Group concluded that the lack of any immediate need for decidingand acting upon a method allows time for proper and thorough evaluation ofthe options. Pressures to take rapid and irreversible decisions that mighteventually prove to be premature and ill- advised should be resisted.

In summary, experience has shown modern methods of storing liquidwaste to be safe; technology and plans for converting this waste into solidform are well advanced, and a number of technologically and economicallyfeasible options for final disposal are under detailed study.

5.2 Other highly active solid waste

Much of the highly active solid waste arising from the nuclear industryconsists of contaminated swarf or metal cladding removed from the irradiatedfuel before reprocessing and highly activated structural parts of reactor cores.At present, these and other highly active wastes are stored in heavily shieldedfacilities. Retrievability of the waste for final disposal must be a considerationin the design of these facilities. The major source of the long -lived activity issmall amounts of irradiated fuel which adhere to the metal. Waste from thereprocessing of high burn -up fuel, e.g., from fast reactors, will present a

32

special problem because of the presence of plutonium and other transuranicelements. Decontamination to reduce the amount of plutonium will be neces-sary in the preparation of the waste for long -term storage or disposal.

5.3 Medium and low activity solid waste

All major users of radioactive materials produce a miscellaneous collec-tion of solid waste of medium and low activity. At power stations, activesludge and ion exchange resins arise from the treatment of liquid effluent andcooling pond water. At present, according to its level of radioactivity, someof the waste in this category is stored in a retrievable way, some is buried incontrolled areas, and some is immobilized in concrete or bitumen and dis-posed of into the deep ocean (49, 50, 51, 52).

Several dumping operations into the north Atlantic Ocean have beenjointly carried out since 1967 by a number of European countries under thesurveillance of NEA /OECD. It is strictly controlled in respect of amounts,packaging, the dumping area, safety precautions during transportation, etc.,and the operations are carried out within the terms of the 1972 LondonConvention (the Intergovernmental Conference on the Dumping of Wastes atSea), which requires prior authorization from national authorities and pro-hibits the dumping of high level waste. Following this Convention, IAEA wasasked to define the upper limits for dumping. The present IAEA definition(53), which is subject to periodic review, defines the waste according to thetype of radiation and its concentration on an activity /weight basis; it assumesan upper limit of 100 000 t a-1 at any one site.

Although aware of some public concern on possible late consequences ofdumping waste into the oceans, the Working Group recognized that currentlevels of dumping represent only a minute fraction of the amounts permittedin the IAEA definition and are a factor of 10' lower than the amounts whichthe model adopted by NEA /OECD (54) predicts could give rise to exposureat the ICRP recommended maximum permissible level. The Group recom-mended that studies be continued in this and alternative fields of waste dis-posal and called on WHO and IAEA to accelerate acceptance by the memberstates of the IAEA recommendations on procedures, as requested in the FinalAct of the London Convention (55).

5.4 Medium and low activity liquid waste

A variety of medium and low level liquid waste arises from nuclearpower stations and reprocessing plants and from medical, laboratory andindustrial uses of radioactive materials. In the nuclear industry this waste istreated, if necessary, to reduce its content of radioactive materials to a levelat which the effluent is safely discharged to the environment. Such treatmentalso produces various forms of solid waste which have to be stored. The

33

amounts of low activity liquids which are permitted to be discharged to theenvironment are determined by national regulatory bodies on the basis ofinternational recommendations in such a way that exposures to the generalpublic are kept well below accepted health protection standards.

For example, the impact on man and on the aquatic environment re-ceiving liquid effluent depends on the quantities and nature of the materialsdischarged and on the conditions of the release, particularly on the radio-nuclides concerned and the degree of initial and final dilution in the watermass. The Working Group stressed that particular attention must be paid tothe possible effects on man through various exposure routes, e.g., foodchains, rather than to the possible (and probably temporary) effects onaquatic populations.

Before major discharges are made, it is important to establish the pre-dominant exposure routes for man through bioaccumulation and /or externalradiation. During and following periods of discharge it is necessary to carryout appropriate monitoring programmes and to publish the results in termsof human exposure. The Group agreed that current and predicted releasesof radioactive waste to the sea make only a minute addition to its total naturallevels of radioactivity (25C Ci km-3, mainly potassium -40) and that extensivedata offer no evidence that these releases have been harmful to man (56).However, prudence dictates that the exposure routes leading to man and toaccumulation in marine organisms should be kept under close review.

As the nuclear industry grows, maintenance of the present low levels ofexposure (see Section 8) will demand improved decontamination of some ofthe liquid effluents. The Working Group recognized that developments arebeing undertaken to achieve these improvements.

Discharges to the aquatic environment have been the subject of extensivereview, and there are many detailed publications (50, 51, 57).

5.5 Discharges into the atmosphere

Discharges from reactors into the air may include argon -41 (from irradia-tion of air), krypton -85 (a fission product), xenon -133 and isotopes ofiodine, and carbon -14 from irradiation of reactor materials. From fuel repro-cessing plants, the most volatile elements still remaining in the fuel, mostimportantly krypton -85 and tritium, are likely to be released during dissolu-tion of the fuel. Quantities of radionuclides which could be of importanceto health are eliminated or reduced to acceptable levels by present technology.Atmospheric transport on a global scale and the long half -lives of some of theradionuclides concerned necessitate an evaluation of the collective exposureof populations on a world -wide as well as on a local or individual basis. To beeffective, control measures to limit exposure from discharges of these radio-nuclides will require international agreement and implementation.

34

The discharges of greatest importance in the nuclear industry consist oflong -lived tritium, carbon -14, krypton -85 and iodine -129.

Tritium (half -life 12.2a) is produced naturally in the atmosphere by theinteraction of cosmic rays with nitrogen and oxygen. Its production rateis 1.6X106 Ci a-1 and the natural inventory is 2.8X107 Ci. Ninety per cent ofnatural tritium is in the hydrosphere, 10% in the stratosphere and 0.1% in thetroposphere (1). Tritium can be formed in reactors in a number of ways, e.g.,by neutron activation of constituents of light or heavy water or as a fissionproduct. Total production in gas -cooled and light water reactors has beenquoted as about 2X104 Ci per 1000 MW(e)a and from heavy water reactors asabout 5X 105 Ci per 1000 MW(e)a (39, 58). Its quantity in, and distributionamong, the various waste streams also depend on the reactor type and on thenature of the cladding and quality of the fuel (39). Dilution in the sea islikely to result in a lower radiological impact on the population than dis-charge to atmosphere. In the long term, schemes will be required to preventtritium from reaching waste streams and for its safe storage or disposal.

Carbon -14 (half -life 5730a) is continuously formed in the upper atmo-sphere through cosmic ray bombardment at a rate of about 3X 104 Ci a-1,maintaining a total atmospheric inventory of 2.8X 108 Ci. The human bodycontains about 10 -9 Ci. Small quantities are produced in reactors by thereaction of neutrons with atoms of nitrogen, oxygen and carbon in fuel,coolant and moderator. The production rate of carbon -14 will vary withreactor type, graphite moderated gas -cooled reactors producing more thanlight water or fast reactors for which the production rate has variously beenquoted as 10 -50 Ci per 1000 MW(e)a (6, 59). The relative fraction dis-charged from reactors and reprocessing plants also depends on the reactortype (39). The Working Group noted that technology to reduce carbon -14discharges is being developed and will be available when required.

At fuel reprocessing plants the greatest discharge of radioactivity to theatmosphere is of the noble gas krypton -85 (half -life 10.8a), a fission productwhich is released into the atmosphere on dissolution of the irradiated fuel.A 1000 MW(e) power reactor will produce about 3X 105 Ci of krypton -85 ina year's operation (39, 58). It has been estimated (60) that at the end of thecentury the atmospheric inventory could be more than 109 Ci, producing agenetically significant dose approaching 1% of that from natural backgroundradiation. Means for removal and safe storage of krypton are being developedfor the time when they are deemed necessary.

Although the shorter -lived iodine -131 fission product (half -life 8d)has substantially decayed before fuel reprocessing, iodine -129 (half -life1.7X 107a), formed in much smaller quantities (about 1 Ci a-1 in a 1000MW(e) reactor (39)) has a half -life of 16 million years. Radiological protectionauthorities do not expect that health considerations will necessitate furtherprovisions for removing it from airborne effluents from reprocessing plantsfor the time being, but if the need arises methods for doing so already exist.

35

6. SITING AND DECOMMISSIONING OFNUCLEAR FACILITIES

6.1 Siting

Factors influencing the selection of sites for nuclear facilities includesite characteristics which influence the effects of normal or accidental releasesof radioactivity (population distribution, hydrology, meteorology and landuse for agriculture or industrial purposes), site technical features (trans-mission lines, availability of cooling water, accessibility), site characteristicspossibly endangering the facility (flooding, earthquakes, geotechnical featuresof the soil, transport operations) and amenity and economical factors (in-cluding possible future use of the land). IAEA has recently issued a publica-tion dealing with many aspects of siting nuclear facilities (27).

In the unlikely event of an accidental release into the atmosphere ofradioactivity from a nuclear plant, an important factor affecting controlof potential population exposure is the population density and distributionnear the facility. Criteria have been developed by some licensing authoritieswhich specify an acceptable population distribution relative to the plantdesign and its engineered safety factors. With improving safety technology,and a growing desire to locate power plants close to energy consumptionareas, there has been a tendency in the past few years towards acceptinghigher population density sites. Population characteristics of nuclear sitesvary widely, with densities from less than about 0.1 persons per km2 within20 km from the site to sites with a population of more than a million personswithin 20 -30 km. Exclusion zones with various restrictions around powerplants vary from 0 to about 2 km.

The Working Group strongly emphasized that remote siting cannot beconsidered as a substitute for sound design, construction and operation of theplant.

6.2 Decommissioning

The operating life of a commercial nuclear reactor is variously assumedto be 25 -35 years (49). Most of the sites licensed for nuclear power plantswere chosen for features which provide a strong incentive for their continuedfull use. It would therefore normally be desirable for a plant at the end of itslife to be dismantled, as far as is necessary and as quickly as is consistent withsafety, to make way for a new plant which can use existing site facilities.

Some nuclear installations, including a number of small reactors andother plants, have already been successfully dismantled. This experienceincludes the decommissioning of the 22 MW(e) Elk River reactor and anexperimental fast reactor in the USA. A large section of the fuel reprocessing

36

plant at Dounreay in Scotland was decontaminated prior to its reconstructionto handle fuel from the 250 MW(e) fast reactor, and dismantling operationshave begun on the Le Bouchet uranium fabrication plant in France. Butdismantling has not yet been necessary for large power reactors.

After years of operation many reactor components and structures willhave become radioactive as a result of their intense irradiation by neutrons,and some will have become contaminated. Their dismantling will requirespecial techniques and will create thousands of tons of waste material ofvarious low and intermediate levels of radioactivity. In the steel structures theactivity will at first be dominated by relatively short -lived isotopes of ironand cobalt. Later, however, the longer -lived nickel -63 (half -life 92a) becomesthe principal radionuclide, and after 40 -50 years the total activity in thesteel will decay with a half -life of about 100 years. There are also smalleramounts of longer -lived radionuclides, such as nickel -59 (half -life 8X1 04 a).

For a number of years the problems and costs of decommissioningredundant nuclear plant (particularly reactors) have been under examination.Three stages are envisaged.

Stage 1. Permanently taking the installation out of service, withoutdismantling it, and putting it into a state in which it would be safe underroutine surveillance and monitoring.

Stage 2. Reduction of the installation to the minimum size withoutpenetrating the highly irradiated or contaminated parts, e.g., thoseassociated with the reactor core. Surveillance of the plant and the en-vironment would be continued.

Stage 3. Complete removal of radioactive components of the plant andrelease of the area without restriction.

Decisions on how far to proceed will depend on energy demands, oneconomic considerations, on the radiation exposure penalty to the dismant-ling staff, and on future policies on the disposal of radioactive waste. Al-though it is premature to make firm cost estimates, it is likely that the costof dismantling would be a reasonably small fraction (perhaps a few per cent)of the initial investment. An IAEA Technical Committee (61) has consideredvarious aspects of decommissioning.

Whatever the future policies may be, it will be important for the sitelayout and the design and construction of nuclear plants to incorporatefeatures which would aid their eventual decommissioning and dismantling.Requirements to this effect, on plant design, etc., are being implementedin several countries.

37

7. ACCIDENTS IN THE NUCLEAR FUEL CYCLE

As is the case with all energy production facilities, nuclear plants entailrisks of accidents that could affect workers and the public. This sectiondiscusses potential accidents in the thermal reactor fuel cycle that couldconceivably lead to substantial releases of radioactive materials to the atmo-sphere and hence to uncontrolled radiation exposures of the population.(The case of the fast reactor was not specifically discussed by the Group.)Occupational accidents in the nuclear industry not involving radiation expo-sure are also considered.

Extensive analyses have been made of the probabilities and health conse-quences of accidental releases of radioactivity from nuclear facilities. Nuclearplants are designed and constructed so as to ensure very low probabilities foraccidents that could potentially have serious consequences for the public.If such an accident did happen, siting policies (Section 6) and emergencyplans and procedures would help to mitigate the consequences.

7.1 Power plant accidents

A number of detailed studies have been made to assess the probabilitiesand health and environmental consequences of reactor accidents (62, 63, 64,65). All these studies are consistent in showing low risks for the populationfrom nuclear power plants (66).

Even following simultaneous failure of a number of independent safetysystems, a major release of radioactivity can only take place after the fuelhas overheated, a substantial part of the reactor core has melted, and thebarriers surrounding the fuel and the reactor have been broken. In general,therefore, it is the gaseous and volatile fission products which would bereleased most readily. Such an accident could conceivably lead to radiationexposure of large numbers of people in the population.

Froni a public health point of view, the most important isotopes wouldbe those of the fission product gases (krypton and xenon), iodine (iodine-131),tellurium, ruthenium and caesium (caesium -137). Following a release, a cloudof radioactive material could be carried downwind, progressively decreasingin concentration, at a rate which would depend on wind speed and weatherconditions, and with a reduction in radioactivity due to radioactive decayand deposition. At very short distances direct radiation from the cloud wouldbe important, but as the cloud dispersed inhalation of fission products wouldbe the dominant immediate hazard. For the first few days the most importantsource of exposure would be radioactive iodine, but after some time radiationfrom deposited caesium would be the dominating factor. The most importantfactors in determining the consequences of a given release of activity are themeteorological conditions, the population distribution, and the actions takento mitigate the consequences, such as taking shelter or eventually evacuating.

38

The most detailed study of reactor accidents is that sponsored by the USNuclear Regulatory Commission (62). Although this study (referred to belowas the Reactor Safety Study (RSS)) was made for American conditions(60 actual reactor sites in the USA were considered), the results are in line withstudies carried out in other countries. The main results are summarized inFig. 4. In order to put the nuclear accident risks for society into perspective,data for other types of major accidents caused by the activities of man areincluded. A tabular presentation of the data pertaining to the acute deathrisk is given in Table 8, which refers to the USA.

The long -term effects of a reactor accident could include genetic effectsand cancer. The total numbers of delayed deaths could be substantiallygreater than the numbers of acute deaths. The RSS concluded that, forexampsle, for the serious accident which might occur at a frequency of oncein 10 reactor years of operation, the number of delayed cancer deaths peryear would be similar to or somewhat greater than the number of acutedeaths. For accidents of decreasing severity (and higher probability) thenumber of cancer effects would be increasingly important relative to thenumber of acute deaths. However, on a national basis, the number of thesehealth effects would be difficult or impossible to detect statistically fromthe normal incidence rate.

The RSS further shows that whereas there is a small probability of alarge accident (for instance, about 1 chance in 100 million years for an acci-dent in one reactor causing 1000 acute radiation fatalities), an accidentinvolving melting of the fuel in the reactor core will most probably not leadto breaches of the containment and hence will not result in any acute radiation-

induced fatalities, cancers or genetic effects in the public.The RSS was based on a detailed examination of possible plant failures

that could lead to radioactivity releases. There is no way of proving withabsolute certainty that all possible failure sequences that could contributeto public health risk have been taken into account. However, the systematicapproach used in identifying possible accident sequences makes it very un-likely that a dominant contributor to the overall risk was overlooked. Al-though not extensively reported, parametric studies were performed, as partof the RSS, to test this conclusion. These studies gave corroboratory results.A further important factor is that only those failure sequences that couldlead to core meltdown need be considered, substantially limiting the typeand number of failures of equipment and human failures that could contri-bute to public risk (reference 62, Appendix XI, Chapter 3).

In discussing the probabilities and consequences of possible major acci-dents involving nuclear power plants, the Working Group saw no reason todissent from the general conclusions of safety analyses recently carried out ina number of countries which have assessed the risk to the public from accidentsinvolving releases of radioactivity from the reactor core to the environment as

39

Fig. 4. Examples of frequency of accidents involving acute fatalities dueto human activities, including operation of nuclear power plants'

10

10 -1

y, I

J`,3 - - - - - --t-o,

10 ` --

10

- -

0-5-^ II -t -+ - -

10-6

0' f

I

I I I

I I 100 Nuclear Power Plants- -1- - - 1-- - -

I I I

I I I I

I I I I

1 i 1 I

10 100 1 000 10 000 100 000 1 000 000

Number of acute fatalities (X) per accident

a After Reactor safety study - an assessment of accident risks in US commercialnuclear power plants (62). Reproduced by kind permission of the US Nuclear Regu-latory Commission.

40

Table 8. Risks of acute death from various causes'

Accident typeAnnual number

of fatalitiesIndividual death

risk per year

Motor vehicle 55 791 1 in 4 000

Falls 17 827 1 in 10 000

Fires and hot substances 7 451 1 in 25 000

Drowning 6 181 1 in 30 000

Firearms 2 309 1 in 100 000

Air travel 1 778 1 in 100 000

Falling objects 1 271 1 in 160 000

Electrocution 1 148 1 in 160 000

Lightning 160 1 in 2 000 000

Tornadoes 91 1 in 2 500 000

Hurricanes 93 1 in 2 500 000

All accidents 111 992 1 in 1 600

Nuclear reactor accidents 1 in 5 000 000 000(100 plants) (estimated)

a After US Nuclear Regulatory Commission (62).

41

low. It was pointed out that although, as in any industry, many small andlocalized accidents might occur, their impact would be more likely to involveloss of generating capacity and financial penalties than physical harm.

7.2 Transport accidents

The potential for accidental radiation exposures of the public duringtransport of radioactive materials in the nuclear fuel cycle is, in practice,mainly associated with the transport of spent fuel elements from powerplants to reprocessing plants and possible future transport of high level wastefrom reprocessing plants to waste storage installations or disposal sites.

IAEA has published recommendations for the transport of radioactivematerials including spent fuel elements (26). They include requirementsthat type B transport casks (those used for potentially more hazardousconsignments) are able to withstand the following conditions without theescape of radioactivity from the cask:

- a free fall of 9 m on to a hard surface;

a free fall of 1 m on to a 15 cm diameter steel bar;

a 30- minute fire at 800 °C;

immersion under water to a depth of 15 m.

Thus, it is considered highly unlikely that transport accidents couldrupture the cask and the fuel assemblies and thereby give rise to harmfulreleases of radioactivity. As the fuel assemblies are stored for extended periodsbefore shipment, most of the radioactivity will be due to the longer livedstrontium -90 and caesium -137, which are not volatile. Numerous studieshave been performed on the risks and consequences of transport accidents(67, 68). Estimates suggest that an accident serious enough to cause a minorrelease of radioactivity may occur once every 80 -200 million vehicle .kmfor road and rail. One 1100 MW(e) reactor can be expected to require about60 truck or 10 rail shipments of spent fuel per year (69). In the USA to dateabout 4000 shipments of spent fuel have been made. Half a dozen seriousaccidents have taken place during these shipments. In no case has a type Bpackage released activity into the environment as a result of an accident andin no case have members of the population been exposed to excessive dosesof radiation.

In an accident causing rupture of the shipping container, any radioactivecontamination occurring would be localized. Although in extreme casesevacuation of people from the immediate vicinity might be desirable, moregeneral evacuation, although common in accidents including releases of othertoxic materials such as noxious gases, would not be necessary (68). On thebasis of experience and the assessment studies made, the Working Group con-cluded that public health risks from transport of spent fuel are very small.

42

High level radioactive waste will be transported from reprocessing plantsto waste storage or disposal sites only in solidified form and a number ofyears after the fuel has been taken out of the reactor. Considering the form ofthe waste and the lower number of transport operations, the public healthrisks from the transport of high level waste are expected to be even less thanthose from spent fuel transportation.

7.3 Accidents in fuel reprocessing plants

A reprocessing plant may contain roughly as much radioactivity as a1000 MW(e) operating reactor. However, all fission gases except krypton -85,as well as the most volatile fission products, will have substantially decayed.The most important nuclides will be strontium -90, ruthenium -106 andcaesium -137. Operations in reprocessing plants do not involve high pressuresand temperatures and involve a lower specific heat generation than in areactor; the potential for releases of radioactivity into the atmosphere or intowater is lower, even though the material is mostly present in liquid formduring the reprocessing operation. Hence, it is not considered likely thatmajor concentrated releases to the atmosphere could occur that would leadto public health consequences similar to those which might follow a majorreactor accident.

7.4 Accidents during disposal of high -level radioactive waste

As indicated in Section 5, a likely method of permanent disposal ofsolidified high -level radioactive waste is in geologically stable formationsunderground, e.g., in rock salt or other rock formations.

The extreme consequences of an accident following disposal wouldinvolve total leaching of the radioactivity into ground water, which wouldsubsequently reach surface water and be consumed by the public. An exten-sive study of the worst possible situation has been made (78), assumingburial in average, undisturbed geological formations. Following leaching,movement of radioactive materials in the ground water towards the surfacewould be retarded by chemical and physical processes in rock and soil.The delay in reaching the surface would be tens of thousands of years forstrontium -90 and probably millions of years for the transuranic elements.If this water were ingested by the population, the study estimates that itcould cause less than 0.5 fatality during the first million years after disposal.A combination of this type of accident with major geological upheavalscould have more serious consequences. However, disposal sites would becarefully selected in areas of high geological stability and isolated frommoving ground water (or where the flow of any ground water is very slow)(see also Section 5.1). The probability of an accident involving exposure toman following carefully controlled disposal of high -level radioactive waste isconsidered to be remote and would have very limited consequences.

43

7.5 Procedures for mitigating the consequences of accidents

Following accidents involving the release of radioactivity to the environ-ment, the implementation of comprehensive emergency plans would serve toreduce substantially the public health impact. In some circumstances limitedevacuation of people from the downwind sector might be necessary. Incase of longer -term hazards due to contamination, consumption of 'foodand drink might have to be controlled for a period of time. Other actionsmight include decontamination and distribution of tablets containing stableiodine to reduce thyroid uptake of radioiodine. Mitigating actions will varyaccording to the type of accident, local conditions, available facilities, etc.It is expected that local and central health authorities would be heavily in-volved both in planning and execution of the emergency plan. In takingdecisions on emergency action, e.g., evacuation, it must not be overlo'okedthat these actions may have associated risks of their own, e.g., transportaccidents, and due regard must be paid to the local conditions at the time ofthe accident.

Emergency plans and radiation monitoring programmes must be developedin close cooperation between the relevent public health authorities and thestaff at the nuclear facility. Periodic exercises involving plant personnel,emergency teams and local authorities should be carried out.

IAEA and WHO have issued reports on the role of public health auth-orities in the radiological field (49, 71).

7.6 Non -radiation occupational accidents in nuclear power production

As for other types of energy production, nuclear power brings with itthe risk of occupational accidents in fuel production, plant construction andoperation, transport and handling of waste. A summary of some recent data(6, 72) is presented in the final column of Table 9, which shows that thenon -radiation occupational accident fatality rate in the nuclear industry isdominated by mining and construction accidents.

S. RADIATION EXPOSURES FROM NORMAL OPERATIONOF THE NUCLEAR FUEL CYCLE

Drawing on the combined experience of members of the Working Groupand on the results of a review made for NEA /OECD (6), the state of know-ledge on present health risks from radiation exposure from the various stagesof the nuclear power industry was reviewed.

44

Table 9. Collective whole -body doses, partial -body exposures and occupational fatality rates occurring at different stagesof the nuclear power production process

Stage

Whole -body exposures(manrem per MW1e)a) Partial -body

exposures

Occupational(non -radiation)

fatalitiesper 1 000 MW1e)aPopulation Occupational

Construction ofinstallations - - - 0.25

Uranium mining - External, to miners 0.05 Lungs (miners) 0.1

Milling and processing - (Probably) <0.1 Lungs and hands, slight -0.1

Fabrication andenrichment - - Probably slight <0.01

Liquid waste From activation and

Reactor operation <0.01Gaseous waste

fission products (externaland tritium) 1.0

- 0.02

0.1 Carbon4

Liquid waste O. a From activation and Occupational, occasionally to0.2 fission products lungs and other tissues.

Reprocessing plants Gaseous waste0.25

(mainly external) 1.0 Public, to skin, intestine, thyroidand bone for small groups

0.02

Other fuel steps - 0.03 - <0.01

Transport <0.01 <0.01 - <0.01

Accidents 0.05 - - <0.01

Decommissioning - 0.03 - 0.05

TOTAL 0.7 2.2 - 0.55

TOTAL (genetically significant) 0.3 0.6 - -

a Exposure from carbon -14 integrated over 500e and assuming 90% retention (see Section 8.4). Modified after Pochin 16).

The doses received by members of the population are generally too lowto be measured directly. In most cases they must be estimated by usingmodels of the distribution of radioactive materials following their releaseinto air or water in association with surveys which identify the exposed popu-lation and important exposure pathways. This review takes into accountexposure of individuals, populations near nuclear sites and, where appro-priate, global populations. In drawing conclusions as to health effects fromradiation exposure, the Group used the best current information on dose/effect relationships, as detailed in Section 2: for radiation protection pur-poses a linear relationship extending down to the very lowest levels ofradiation to which the general population is exposed from nuclear poweroperations was adopted following ICRP recommendations (32). The analysistakes account of the total dose involved, including not only the dose receivedduring the year of operation but also that to which the population is com-mitted in the year of operation to receive in the future.

The total exposure of populations is expressed as "collective doses"in manrem and represents the average dose or dose commitment in remmultiplied by the number of persons in the population considered (seeAnnex I). The calculated health effects are summarized in terms of thetotal collective dose per unit of nuclear electrical power production. Themain sources of exposure involve whole -body radiation. The radiation expo-sures received as a result of the operations of the nuclear industry must be

of man from otherman -made sources (medical applications, nuclear weapon fallout and con-sumer products) and the inescapable background radiation from naturalsources (from cosmic radiation, radioactive constituents of rocks and buildingmaterials and from radioactive materials present naturally in all humanbodies). The levels of these various sources of radiation are shown in Table 10.Geographical variations in the natural levels of terrestrial radiation, even oversmall distances, far outweigh increases in radiation exposure calculated fromthe world's predicted nuclear power programmes.

8.1 Construction of installations

The only significant potential source of radiation exposure during con-struction of nuclear plants, as for other large constructional projects, isindustrial radiography.

8.2 Mining and milling

The mining of uranium ore is associated with radiation health risks dueto the inhalation of radon and its daughter products. The principal internalradiation exposure is from alpha radiation, the emitters being attached tovery small particles which are inhaled from the mine atmosphere. The problem

46

Table 10. Estimates of average annual whole -bodyradiation exposure (mrem) to the population from

various natural and man -made sources'

Source

USA UnitedKingdom

1970 2000 1973

(whole -body dose) (gonad dose)

Natural background 102b 876Cosmic radiation 44 28Terrestrial radiation 40b 38bInternal radiation 18 21

Medical practices 73 -73 14

Man -made environmentalGlobal fallout 4 5 2.2Nuclear power (wastes) 0.003 0.4 0.01cMiscellaneous sources 2.6 1.1 0.7

Occupational exposure(from nuclear power pro-duction, industrial radiographymedical and dental work, etc.)

0.8 0.9 0.6

Total 182 182 105

a After National Academy of Sciences, National Research Council (2) and Webb(72).

b There are wide variations in natural levels of radiation and individual levels ofexposure in different parts of the same country. For example, the United Kingdomstudy (72) reports individual variations of 65 -200 mrem.

c More recent estimates suggest a figure of about 0.1 mrem.

47

seems to be minimal in open -pit mines and may be partially controlledunderground by care through mine ventilation and related measures, suchas sealing off unused sections of a mine. The technology needed to provideacceptable working conditions appears to be available. Although personalprotective devices may be used their overall effectiveness is probably lowdue to various physical and usage factors. When radiation levels in the mineatmosphere are not adequately controlled, serious health consequencesresult.

The health consequences and epidemiology have been thoroughly re-viewed and evaluated (25, 73, 74, 75, 76, 77). Health consequences ofmining must be considered as an inevitable component of the use of nuclearfuel and should not be overlooked in countries which do not mine uraniumbut import it.

The cumulative radiation exposures of uranium miners are expressed(76) in terms of working levels months (WLM), the cumulative product ofperiods of underground exposure in working months (each of 170 hours)and the corresponding air concentrations of radon daughters in workinglevels (WL)a.

Much of what we know about the exposure- response relationship be-tween inhalation of radon and its daugher products and lung cancer comesfrom a study of miners in the USA during the period 1951 -1960 and inCzechoslovakia. In the American study (73), the exposures of the minerswere estimated from their histories of employment and from yearly average(measured or estimated) mine radiation levels. Subsequent mortality of theminers, including lung cancer mortality, was then related to the estimatedradiation exposures and other important factors such as cigarette smoking.By 1974 mortality from lung cancer in this group was roughly 4 -5 timesgreater than that in the general population. The incidence was higher amongcigarette smokers, but adjustments for smoking did not account for most ofthe excess. (At present, many mining officials prohibit uranium miners fromsmoking while underground.) The mortality from lung cancer was muchhigher than that in other mining operations, such as coal and potash mining,where radiation levels are low. Other studies of miners working at intermediateto low levels of radiation show intermediate lung cancer risks. Non -malignantrespiratory diseases were also high, as in other types of mining (77).

Estimates of excess lung cancer mortality have been made for the cur-rent US maximum permissible exposure level in mining (4 WLM /a). Forminers working 30 years, starting at 20 years of age, these range from 2.1to 5.5 excess deaths up to age 80 per 10 000 man. a 1 of mining. This range

a One WL is any combination of radon daughters in 1 litre of air which resultsin the ultimate release of 1.3x105 MeV of alpha energy. This numerical value is derivedfrom the alpha energyeleased by the total decay of the short -lived daughter productsin equilibrium with 10 µCi of radon -222 per litre of air.

48

depends upon whether the estimated risks from all levels of exposure areused or only those from the lower levels of exposure in the American study.As far as possible, assumptions made were checked by analyses of the data(77). Most respiratory cancer deaths occur 10 or more years after the startof mining (76).

In a recent Czechoslovak study (78), covering on average 24 years ofobservation after the onset of the exposure, the exposure- effect relationshipin the total group was not at variance with the assumption of a linear dose-

response relationship. The presumption of direct proportionality of theexposure and effects yields 0.23 ± 0.04 lung cancer cases per 1000 workersper WLM as an estimate of average radiation risk. If the same "modifiedlife table method" as in the USA study (73) is applied, the excess deathrate from lung cancer in Czechoslovak uranium miners is about 30 deathsper 10 000 man a, or the excess death rate about 78 per 10 000 manaof mining.

Whereas the technology needed to provide acceptable working condi-tions in uranium mines is available, it has been stressed (74) that ventilationalone will not reduce concentrations of radon daughters to much lowerlevels than those prevalent in 1969. As has been pointed out "studies ofmethods of reducing radon emission into working areas, more effectiveand more lasting means of closing off inactive areas, more acceptable respi-rators, and of removing radon from mine air might well result infurther reductions in atmospheric contamination" (74).

The radioactive materials in rock may produce external exposures ofroughly 0.5 rem a-1. Thus, assuming (6) that 100 miners are involved insupplying uranium ore for a 1 000 MW(e)a output, a collective dose of50 manrem or 0.05 manrem per MW(e)a would result. The dose will dependon the percentage of open -pit mining, the grade of ore, the degree of mech-anization, etc.

The accidental fatality rate in uranium mines in the USA was about10 deaths per year per 10 000 miners over the period 1966 -76,a corre-sponding to an average of about 0.1 death per year for a 1 000 MW(e)aoutput. The tailings from uranium milling produce continuing releases ofradon -222 which can result in the exposure of members of the general popu-lation (49, 80, 81, 82, 83). However, the problem can be minimized, forexample, by covering the tailings with about 6 m of earth. This has beenestimated (82) to reduce the radon emission by as much as 98 %. If the tail-ings pilings are exposed to weathering and leaching by water care must beexercised because the water runoff contains radium. In some cases in theUSA the radioactivity of the river into which liquid tailings have been dis-charged may be 10 or more times the normal level (35).

a Lundin, F.E., private communication (1976).

49

8.3 Fuel fabrication and enrichment

In the fabrication of uranium fuel elements, the control of potentialrisks is relatively straightforward (84) and experience has shown contain-ment procedures to be adequate. No appreciable discharge of radioactivematerial to the environment is to be expected, and there is little or no riskto the population. Exposure of operating staff is low.

The introduction of plutonium- bearing fuels in thermal and fast reactorsrequires a high degree of containment because of the toxicity of plutonium(5, 85). In the handling and storage of plutonium and enriched uranium fuels,elaborate precautions are taken to prevent the possibility of over -accumulationwhich could lead to a criticality accident, giving potentially lethal levels ofradiation in the working area.

8.4 Reactor operation

Exposure of populations during normal reactor operation comes mostlyfrom controlled releases of radioactive materials, particularly fission products,discharged to the atmosphere. Far smaller amounts of radioactive materials(from induced activity in corrosion products, etc.) may be discharged withaqueous effluents. The magnitude and route of human exposure dependon the type of reactor; the radioactive content of the effluent depends onthe delay, if any, before its discharge.

During irradiation of the fuel, small amounts of some of the fissionproducts which build up in the fuel leak through the cladding. This appliesespecially to the gaseous radionuclide such as tritium, isotopes of kryptonand xenon and volatile compounds of carbon -14. In reactors using heavywater as moderator, some small proportion of the tritium produced can alsoleak into the atmosphere, and tritium is also produced where light water isused for cooling. In gas- cooled reactors (particularly the earlier designs)exposure of local populations occurs through the release of short -livedargon -41 (half -life 1.8 h) formed by irradiation of air used for cooling thereactor shielding.

The collective dose to populations within 80 km of modern boilingwater reactors from short -lived gases has been estimated to be 0.02 manremper MW(e)a whereas the dose from gas -cooled reactors is about 0.04 manremper MW(e)a. Pressurized water reactors release mainly xenon -133, the expo-sure within 80 km being estimated to be 0.01 manrem per MW(e)a (6).

Various figures have been calculated for the average annual dose receivedby individual members of the population from worldwide nuclear reactoroperation (49). For the USA a figure of 0.013 mrem has been reported and forthe United Kingdom a figure of less than 0.003 mrem. These are less than 0.02%of the average natural radiation background. These figures lead (6) to overallestimates of about 0.1 manrem per MW(e)a from discharges into the

50

atmosphere and less than 0.01 manrem per MW(e)a from discharge of liquidwaste. The total collective dose from all liquid discharges from reactorsproducing 3000 MW(e) of nuclear power in 1971 was estimated (49) not toexceed 3 manrem.

Radioactive carbon -14 is at present released predominantly from reac-tors, with smaller amounts being released during fuel reprocessing. The radio-activity of carbon -14 released per 1000 MW(e) of power produced (-1 Ci) ismany orders of magnitude lower than for krypton (3X 105 Ci) or tritium(2X 104 Ci). However, its very long half -life and its long circulation in the bio-sphere will cause it to accumulate slowly and cause irradiation at low doserates for long periods of time. Assuming production of 50 Ci per 1000 MW(e)a,taking current atmospheric, hydrological and biological models and assumingtotal release of the carbon -14 formed, the collective dose commitment duringthe first 30 years has been calculated to be about 0.5 manrem per MW(e)a(6). Over 500 years the integrated collective dose commitment would be1 manrem per MW(e)a. Further calculations extrapolated to the whole offuture time yield a value of 10 manrem per MW(e)a for the limit of collec-tive dose commitment from this source. Assuming formation of 30 Ci per1000 MW(e)a, a collective dose extrapolated to infinity has been calculatedto be 4.5 manrem per 1000 MW(e)a (86). All these values include the assump-tion (certainly over -pessimistic) that presently available or future technologywill not be applied to reduce the releases. The Group felt it would be reason-able to assume 90% retention and suggested use in overall estimates a500 -year integrated value of 0.1 manrem per MW(e)a.

A wealth of data from a number of countries permits estimation of theexposure of workers in nuclear power plants, e.g., data published by theUnited Nations Scientific Committee on the Effects of Atomic Radiation( UNSCEAR) (1). The UNSCEAR data, expressed in terms of power produced,show considerable uniformity between exposures from 20 reactors in sixdifferent countries despite variations in age, although the relative contribu-tions from external and internal exposure show some differences. Much ofthe exposure in reactor operation is received during fuel replacement, main-tenance and unscheduled repairs. Experience of the Working Group andpublished information led to a figure of 1 manrem per MW(e)a for the presentcontribution of whole -body occupational exposure (internal plus external)during reactor operations.

8.5 Fuel reprocessing

Exposure of populations from reprocessing plants comes partly fromrelease to atmosphere of the most volatile radioactive materials (particularlyfission products), still remaining at the time of full dissolution, and partlyfrom discharges of low activity liquid effluents.

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The main source of whole -body exposure is from the release of krypton -85, and estimates of global exposure from thermal reactor fuel reprocessingare in the range 0.15 -0.2 manrem per MW(e)a (6) (for fast reactors 0.1 man -rem per MW(e)a). Lower exposures are expected from releases of tritium andother radionuclides (0.02 manrem per MW(e)a for thermal reactors and0.02 manrem per MW(e)a for fast reactors (30)), the total exposure from allairborne releases being perhaps 0.25 manrem per MW(e)a. The very lowactivities of iodine -129 released contribute very small exposures to thethyroid gland.

There are few major discharges of liquid waste from reprocessing plantsto coastal waters. Calculations of population exposure from the amountsdischarged is complex, depending very much on the local circumstances inthe area of release and exposure pathways specific to that area. Examinationof published information suggests that it would be reasonable to predictfuture collective population exposures by this route from the normal opera-tion of reprocessing plants of the order of 0.2 manrem per MW(e)a.

The reprocessing of nuclear fuels involves exposure of operating staffboth to external radiation and to the risk of internal contamination, althoughmost of the measured exposure is from external sources. In noting that theindividual doses to workers in reprocessing plants are at present higherthan those in the operation of nuclear reactors, the Working Group agreedthat there was no reason why this exposure situation should be accepted.With improved design of reprocessing plants it should eventually be possibleto reduce individual occupational exposures to the levels attained in reactoroperation. Experience of the Working Group and published information ledto an average of about 1 manrem per MW(e)a for present whole -body expo-sure from combined external and internal sources from fuel reprocessing.

8.6 Transport

Strict application of internationally recommended standards for trans-port operations (87) keeps radiation exposure of the general population andoperators to very low levels. Figures of 0.03 and 0.005 manrem respectivelyper MW(e)a have been calculated (6).

8.7 Waste storage

The storage of waste materials and stocks of fuel and other radioactiveproducts within nuclear sites is carried out in such a way that exposure ofoperators and the public is minimal. Storage and eventual disposal of wasteon storage sites should also result in minimal exposure of operators and thepublic compared with exposure to other parts of the fuel cycle.

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8.8 Decommissioning of nuclear facilities

Radiation exposure of workers will occur during the dismantling ofcontaminated and activated components of redundant nuclear plants. Thelevel will depend markedly on the techniques developed for remote operationand on design features incorporated in future reactors to ease dismantling. Itis too early for anything but very crude estimates to be made but the WorkingGroup accepted that a collective dose of about 1000 manrem might bereceived during the eventual dismantling of a large power station. This wouldlead, averaged over a 30 -year plant life, to a figure of 0.03 manrem perMW(e)a.

8.9 Accidents to nuclear plants

The consequences of individual nuclear accidents have been discussedin Section 7. On the basis of the results of reactor safety studies it has beenestimated (6) that accidents involving radiation might contribute to the totaleffects of the nuclear cycle, an annual average exposure of 0.05 manrem perMW(e)a.

8.10 Total radiation exposure from nuclear power programmes and conse-quent effects

The values derived above and in Section 7 for collective whole -bodyexposures and fatal accidents in the various stages of the nuclear fuel cyclea_ re summarized in Table 9.

Within the limitations of the assessment, the total whole -body expo-sures to workers in the nuclear industry and to the public are 2.2 and 0.7manrem per MW(e)a, respectively, whereas the genetically significant dose toworkers and the general population are somewhat less, i.e., 0.6 and 0.3 man-rem per MW(e)a, respectively.

The generation of 1000 MW(e)a of electrical power from nuclearplants would entail, each year, an estimated collective dose commitment ofsome 3000 manrem of whole -body radiation, roughly three -quarters of whichis received by the workers and the remaining one -quarter by the generalpopulation. The collective dose to the population would be made up ofhigher individual doses to relatively small numbers of people near the nuclearfacilities and lower doses to a much larger number of people from widespreaddistribution through the atmosphere or water masses (88).

The smaller genetically significant component of the collective annualdose commitment from 1000 MW(e)a of nuclear power has been estimatedto be about 900 manrem, of which two- thirds is received by workers in theindustry. These estimates of whole -body and genetically significant dosecommitment include extrapolation of the collective population exposure

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from release of carbon -14 forward for 500 years. For carbon -14 a retentionof 90% has been assumed. Assessments for other radionuclides are based onpresent practices and make no allowance for future and presently availabletechnological improvements for reducing exposure of the general populationand workers in the industry.

When considering the incorporation of plant improvements to reducealready small population exposures, it must not be overlooked that thiswould almost inevitably increase occupational exposure still further as wellas produce other forms of waste. It is necessary to evaluate the total impactof exposure and not only that affecting the general population.

By combining these figures with the dose /effect relationships developedin Section 2, the possible total health effects from exposure to workers andthe general population have been evaluated. The results of the evaluationindicate that the supply of 1000 MW(e)a of nuclear power (which wouldserve the needs of about a million people) would give rise to less than onemalignant tumour; in about half the cases the cancer would be curable.For each 1000 MW(e)a of operation, less than 0.5 genetic defect on theaverage might be expected within a range of varying severity. In addition,workers in the industry would probably suffer on the average about 0.5fatal accident and about 30 other disabling accidents not associated withradiation.

9. ENVIRONMENTAL EFFECTS

All industries, including all energy producing operations, have someimpact on the environment. This section considers thermal effects (and theirbiological and ecological consequences) and chemical wastes. These are notunique to nuclear power plants; the environmental effects of fossil- fuelplants are further discussed in Section 11.

9.1 Thermal effects

The discharge of warmed water from a nuclear power plant is nodifferent qualitatively, and little different quantitatively, from that fromconventional power plants. "Thermal pollution ", as it is sometimes called,refers to the accumulation of unwanted heat energy in any phase of theenvironment (89). Reviews of thermal effects in the environment havecurrently been published (90, 91).

The "spent" steam used to drive a turbine is condensed by cooling withlarge amounts of water. For the same electrical output, nuclear plants usemore cooling water than modern fossil -fuel plants and produce about 20% more

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waste heat (92, 90). The thermal efficiency of present nuclear plants is about33 %, whereas future plants are expected to reach thermal efficiencies ofabout 35 -40 %. Under full load conditions the temperature of the coolingwater coming from the outlet of a nuclear station is about 8 -10 degC abovethat of the inlet. This has to be taken into account if direct cooling by river,lake or sea water is considered.

Various methods of heat disposal are employed (93) which can minimizethe impact of thermal discharges upon such natural bodies of water; theseinclude cooling towers, dilution in artificial lakes or canals (if sufficient landis available), water intake from deeper, cooler points, or the addition ofcooler water before discharge (49).

Biological and ecological consequences. The environmental effects ofthermal discharges depend on the size of the water -body receiving the warmwater, its depth, movements, etc. Increased temperature may produce pro-found effects upon reproduction, growth, breeding habits, survival, anddisturbances in the varieties of aquatic life at a given site. Increased tempera-ture also reduces the solubility of gases in water; for example, between 20 °Cand 30 °C the dissolved oxygen decreases by 17% (89), i.e., from 9.2 mg 1-' to7.6 mg 1 -1. Simultaneously, the use of oxygen by organisms increases sincethe metabolic rate roughly doubles for a 10 degC rise in temperature. Mixingbetween the upper and lower layers of water may be inhibited by thermalstratification so that organic waste is kept separate from the higher amountsof oxygen contained in the upper layer; this leads to oxygen depletion inlower strata (90).

One consequence of increasing metabolic rate with increasing tempera-ture is a higher uptake of many radionuclides, e.g., caesium, cobalt, iodineand zinc. Concomitantly, the biological half -life of these radionuclides isreduced, resulting in a more rapid attainment of equilibrium concentrationlevels (57).

Although some fish may favour warmer temperatures, generally few willsurvive above 30 °C. Their food supply, such as diatoms, decreases as thetemperature rises above 20 °C and becomes replaced by the less desirable andoften toxic blue -green algae. Above 35 °C nearly all the diatoms disappear.Hence, at temperatures of 30 -35 °C a water -body is essentially a biologicaldesert (89). For these and other reasons, as for example the scouring effect ofthe discharged water on the bottom characteristics, regulatory agencies indifferent countries have imposed strict limits on cooling water discharges.

Beneficial effects of the discharged warm water (91) include the use ofheated effluents to maintain optimal temperatures for growth and highyields of fish and other seafood, warm water irrigation, soil heating andprotection of crops, and district heating.

Detailed information on the biological and ecological effects of thermaldischarges is available (27, 28, 49, 50, 51, 53, 57, 89, 90, 91, 94, 95).

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Climatic effects. Some evaporation of cooling water takes place in a wetcooling tower; it can be expedited by blowing air through the sprays of waterinside the tower. Discharges of water into the atmosphere at temperaturesabove that of the air can result in localized effects, e.g., fog, ice formation ontrees, roads and transmission lines (90). Chemicals added to the water incooling towers to inhibit the growth of organisms can be transported and mayhave adverse environmental effects (49).

Because of the environmental impacts of wet cooling towers (direct water/air contact), dry air cooling towers with closed loop water transport are beingconsidered in many places despite higher costs and greater land requirements.

9.2 Chemical waste

The control of chemical effluents is important in both nuclear andfossil- fuelled power production, as well as in other industrial operations.Although the means exist to control chemical effluents, available technologyis not always utilized to the best advantage for meeting acceptable limits.

Numerous chemicals are used during the operations of fossil -fuel andnuclear power plants (96). These include those used for corrosion control,such as mixtures of chromate, zinc, phosphate and silicates. Microbial growthis controlled by additives to the water in the cooling towers such as chlorine,hypochlorites, chlorophenols, quaternary amines and organometallics. ThepH of water is controlled by acids and alkalies. Silt deposition may be re-duced by the use of polymers such as lignin- tannin dispersives, polyacryla-mides, polyacrylates and other polyelectrolytes. An extensive list ofchemicals associated with nuclear power plants and their effects on testorganisms is included in 96.

Non -radioactive waste from the nuclear fuel cycle (see Fig. 2) includesoxides of nitrogen and sulfur, fluorides, sulfates, inorganic salts of calciumand iron, sodium chloride, nitrates and ammonia. Maximum safe levels andregulations for the disposal of these chemicals are usually set by governmentalauthorities (97).

10. PROLIFERATION OF NUCLEAR EXPLOSIVES,SABOTAGE AND TERRORISM

Proliferation of nuclear explosives must be seen in two different contexts:that of a possible increase in the number of sovereign nations that have accessto atomic weapons, and that of sub -national groups obtaining and usingnuclear explosives for terrorist purposes.

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Regarding the question of the proliferation of nuclear weapons, theWorking Group noted the status of the Treaty on the Non -Proliferation ofNuclear Weapons, now ratified by 100 nations, and the efforts of nuclearexport countries concerning coordination of measures to assist in reducingprobabilities of international proliferation. Taking into account the increasingamounts of fissile material expected to be handled in the future, the WorkingGroup pointed to the importance of continued efforts to minimize a possiblerisk to the public from illegal future diversion of materials from the nuclearfuel cycle. Individual governments and international organizations are devel-oping stricter measures for physical protection and control of fissile materialin use, transit, or storage (98, 99, 100).

Many assessments have been made of the effort needed to construct anuclear weapon if the necessary material has been acquired. These assess-ments range from a few man -months (79, 101) to tens of man -years (102)of highly skilled effort. One study (102) has concluded that theft of a nuclearweapon from one of the nuclear weapon states represented the greater risk.

Studies of the susceptibility of nuclear facilities to sabotage for a broadrange of threats have been made (103, 104, 105). These studies point out thatsuch plants appear far less susceptible to sabotage than most other civil indus-trial targets. Evaluations of probable consequences following sequences ofsabotage actions conclude that they are likely to be small fractions of themaximum consequences for reactor accidents yielded by the American RSS(Section 7).

The consequences of wilful dispersion by terrorists of a plutoniumaerosol in densely populated areas could be serious. The health consequencesof such dispersion have been the subject of several studies (104, 106). Forrealistic scenarios, inhalation of the cloud appears to be the main risk fol-lowing dispersal, causing eventually approximately 0.05 death per gram ofplutonium dioxide dispersed (106). Local areas could become contaminatedto such an extent that limited evacuation followed by decontaminationwould be necessary. It has been estimated (107) that for relatively smallamounts dispersed, the costs of decontamination could run into millions ofdollars. Since most health effects of the dispersal will be delayed by 15 to45 years, and because of the difficulty of executing this type of terrorist act,it is concluded that plutonium dispersal would probably represent a verysmall part of the overall risk from acts of terrorism.

One perspective on the dispersion of plutonium is obtained from theobservation that, as a result of nuclear weapons tests, some 5 t of plutoniumhave been dispersed in the atmosphere (108). If this were evenly distributedin the world's population each person would have accumulated a body burdenin excess of 1 mg; in fact measured plutonium body burdens are tens ofmillions of times lower than this (109).

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One recent study (105) has indicated the possible usefulness of quanti-tative decision theory in evaluating the potential economic and social risks ofnuclear terrorism and sabotage. The Working Group concluded that, althoughthere is no way of obtaining absolute assurance against terrorist thefts ofradioactive materials which may be used for the production of a nucleardevice, or against nuclear plant sabotage, any risk to the public from such actswould not contribute substantially above that already existing in contem-porary society from other similar threats.

It was also concluded that reducing the rate of nuclear power develop-ment would not substantially reduce the overall possibility of terroristthreats. However, the Group emphasized the importance of continued effortsto minimize the possibility of risk from plutonium diversion and sabotage ofnuclear plants.

11. CONSIDERATION OF HEALTH EFFECTS FROM NUCLEARAND ALTERNATIVE ENERGY PRODUCTION SYSTEMS

A meaningful perspective on the health and environmental effects ofnuclear power can only be obtained by comparing them with alternativemeans of energy production. Comparative assessments are also needed as abasis for rational and cost /effective safety and control procedures. The mainalternatives to nuclear power generation are at present coal- and oil -firedpower plants.

11.1 Public health effects

The increasingly stringent effluent controls for fossil- fuelled powerplants will presumably lead to future reductions of the health effects per unitof electricity produced from these plants. Future technology could lead tosubstantial reductions in the emission of a number of the toxic chemicalpollutants (Table 11 and ref. 110). In addition to the pollutants listed in theTable, about 30 trace elements present in coal are released during combustion.Several of these elements are toxic, including beryllium, mercury, arsenic,cadmium, lead, vanadium, and nickel.

Attempts have been made to relate air pollution to various healtheffects (19, 40, 111, 112, 113, 114, 115, 116). In the absence of reliable dataat low pollutant exposures, a threshold -type relationship is generally assumedfor acute and chronic diseases caused by air pollution. However, as in the caseof radiation, a non -threshold relationship is generally assumed for geneticand carcinogenic effects (117).

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Table 11. Annual releases of chemical pollutants from1000 MW(e) fossil -fuelled power stations'

PollutantsTotal annual emissions (per 1000 t)

Coalb Oilc

Aldehydes 0.052 0.12

Carbon monoxide 0.52 0.0084

Hydrocarbons 0.21 0.67

Nitrogen oxides 21 22

Sulfur oxides 139d 53

Particulate matter 4.58 0.7

a

b

Modified after Terril et al. (118).

Represents the burning of about 2.1x106 t a 1 of semi -bituminous coal.

c Represents the burning of about 1.7x105 m3 a-1 of oil with an assumed ashcontent of 0.05% and 1 .6% sulfur content by weight (present sulfur values are closerto an average of about 0.7% (113)). The emissions given here assume the operation iscarried out with no pollution control.

d Assuming 3.5% sulfur content, of which 15% remains in ash.

Assuming 9% ash content and 97.5% fly ash removal efficiency.

A number of estimates of possible fatalities among the members of thegeneral population have been made. A recent survey of these estimates (111)concludes that the number of premature deaths from emission from fossil -fuelled power plants may be considerably higher than for nuclear plants.However, the uncertainties in these estimates are considerable, as shown bythe wide range of the number of estimated deaths (e.g., for one year ofoperation of a 1000 MW(e) coal -fired station, 1.6 -111 deaths), and truecomparisons with nuclear power are difficult.

A difficult problem in evaluating health effects of emissions from fossil -fuelled power plants is the identification of the individual contributions, ifany, of the various chemical pollutants, bearing in mind the known syner-gistic effects of, for example, suspended particulates, ozone and nitrogenoxides. An additional complication is the unknown influence of the chemicaland physical nature of the suspended particulates.

Sulfur dioxide, in combination with particulate matter, has generally beenbelieved to represent the main health hazard from fossil -fuelled power plant

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emissions. Thus, air quality standards usually include limits on sulfur dioxideto protect human health. The safety margins on some of those standardsappear to be small.

The standards have been set in a range of pollutant concentrationswhere adverse health effects appear to be perceivable. These are described asranging from "discomforts, through physiological deviations from the norm,prevalence of symptoms, appearance of illness, lost working time and prema-ture retirement, to complete incapacity and death" (119).

It is now being increasingly realized that sulfur dioxide concentrationsare probably not the best indication of the health hazard from sulfur pollu-tion. Rather, sulfate or sulfuric acid particles, to which atmospheric sulfurdioxide is converted, are believed to be the most important harmful agents.

It is clear that the safety margins for fossil- fuelled plant emissions (interms of those levels producing readily detectable health effects) are muchsmaller than those for radiation from the nuclear fuel cycle.

11.2 Occupational health effects

Statistical information is available on accidents involving death orinjury for workers in the nuclear, coal and oil power production industries,including mining operations. A survey of this information has been made(111) and respective data are presented in Table 12, together with the WorkingGroup's estimate for the nuclear power industry.

Table 12. Occupational accidental deaths from 1 year of operation of a1000 MW(e) electrical power plant and associated fuel cycle services'

Fuel Occupational accidental deaths/3

Coal 0.54 -5Oil 0.14 - 1.3Nuclear 0.01 - 0.86

^' 0.3e

a Data on accidents during construction of installations are not included becauseof lack of data for fossil -fuelled power plants.

b

(111).

C

The ranges shown are the lowest and highest estimates from four studies cited

The figure is taken from Table 9. It does not include occupational fatalitiesduring construction.

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11.3 Radioactivity from plants utilizing fossil fuels

The fly ash from coal- and oil- fuelled plants contains trace quantitiesof uranium and thorium and their radioactive decay products, especiallyradium -226 and radium -228. The actual amounts depend on the efficiencyof fly ash removal and the composition of the coal. The quantities of radiumreleased by an oil -fired power plant are much less, because oil fly ash containsabout a tenth as much radium as coal fly ash and, in addition, coal has a higherash content than oil (120). The radiological exposure from fossil- fuelled plantsis small, corresponding (per MW(e)) to somewhere in the range of 1 part per10 8 of the ICRP recommended limits as determined from field measure-ments (120). A number of comparisons have been made between the radio-logical health impacts of fossil -fuel and nuclear power generation plants (112,120). Generally, it appears that with present technology the health effectsfrom airborne radioactivity from coal -fired power stations is less than thatfrom boiling water reactors and larger than that from pressurized waterreactors. The radiological impact of liquid effluents from coal -fired plants(including that from waste) does not appear to have been evaluated, but isexpected to be far less than that from nuclear power plant liquid effluents.

11.4 Environmental impacts

Generally, the land areas required for power plants and fuel miningand production are smaller for nuclear plants than for fossil -fuelled plants(121).

Whereas large nuclear power plants generally require the equivalent ofless than 70 truck transports of fresh and spent fuel per year, fossil -fuelledpower plants of similar output require transport by ship or rail of 1.5 -2.5X106 t a' of fuel. Movements of waste from fossil- fuelled plants willvary substantially with solid waste handling procedures. Thus the environ-mental impact of fuel and waste transportation systems will be markedlygreater for coal- and oil -fired plants.

As is well known, the environmental impact of emissions into the airfrom fossil -fuelled power plants can be substantial over large regions. Such animpact is mainly determined by acid precipitation (caused by oxides of sulfurand nitrogen) and includes increased acidity of lakes, rivers and soil, withconsequent effects on aquatic life forms and on the composition and growthrates of vegetation. Releases of radioactivity from fossil -fuelled and nuclearplants probably have no environmental impact.

Rejection of waste heat from nuclear and fossil -fuelled plants aresimilar, the nuclear plants generally releasing about 20% more waste heat towater than fossil- fuelled plants. In certain locations, increase in the tempera-ture of cooling water can lead to substantial local impacts on aquatic con-ditions.

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Climatic effects of fossil- fuelled and nuclear power plants can be causedby waste heat releases, which generally are only of local importance (122),and for fossil -fuelled power plants on a global scale by release of carbondioxide (123, 124). The global temperature increases that could be caused bycarbon dioxide releases from fossil -fuelled power plants are, however, counter-acted by accompanying releases of dust and fly ash. It has, for example, beenestimated (122) that there would be a global average temperature increase ofabout 5 degC in the period 1980 -2050 if the energy needs of the worldpopulation were met largely by fossil- fuelled power plants. Such estimates aresubject to major uncertainties due to insufficient data and knowledge.

11.5 Alternative energy production systems

The main future large -scale alternatives to present energy productionsystems appear to be nuclear fusion and solar energy. Even if successfullydeveloped, these alternatives will also have health and environmental impacts(125).

Possible future nuclear- fusion power plants will, at the end of theirlives, produce large volumes of solid radioactive waste which will requiredisposal or safe storage for generations. Some release of radioactivity duringoperation appears inevitable (126), tritium almost certainly presenting themain radiological health hazard from nuclear- fusion power plants. Radio-active waste production is, however, expected to be substantially less thanthat from nuclear -fission power plants.

Electrical power production plants using solar energy could introducesubstantial environmental effects due to the large land area required. Produc-tion of the materials required for such large plants, their maintenance andoperation, the required transmission systems, and plant decommissioningentail possible health consequences which are difficult to evaluate in theabsence of more detailed plant designs and information on operations andwaste handling procedures.

Other proposed commercial sources of power, the wind, waves, tidesand geothermal energy, will certainly not be without risks and environ-mental impact. However, since quantitative predictions of health and environ-mental impacts of all these possible future sources of power cannot yet bemade owing to lack of information on plant design and operational pro-cedures, a meaningful comparison of impacts with existing power productionsystems is not possible.

11.6 Conclusions

Quantitative analyses of the effects of the nuclear power industry on thehealth and wellbeing of individuals and populations must be assessed in com-parison with the corresponding effects of alternative energy sources (present

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and future). In such assessments, data should be treated on an equivalentbasis, i.e., for equal energy output and for the complete cycle of operations.Indeed, estimates of harm should be compared with what would result fromfailure to develop necessary additional power by any of the alternative means.

Since knowledge of the health effects of alternative sources of energy(e.g., fossil fuels) is generally less precise than that of radiation effects, it wasrecommended that available information be critically reviewed and approp-riate research conducted on the health effects of alternative energy sources.A recent review (127) suggests the priorities which should be given to anyfuture research on health effects of fossil fuels.

12. PUBLIC INFORMATION

Nuclear power has been introduced into several countries withoutgiving rise to public discussions or controversy. In many countries, however,there is increasing public debate on the acceptability of nuclear power. Publicand private organizations are providing the public with increasing amounts ofoften conflicting information on all aspects of the growth of nuclear power.Health effects of radiation from the nuclear fuel cycle are a prominentconcern in the public debate.

The Working Group stressed the importance of early and continuousdissemination to the public of full and factual information on the likely con-sequences of operating nuclear power plants, including comparison withalternative power production sources. Public health authorities would beexpected to participate in the dissemination of such information.

International organizations should play an important role in the dis-semination of information on nuclear energy and should contribute to thegeneral awareness and confidence of the public.

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71

Annex I

DEFINITIONS OF "RISK ", "DETRIMENT ", AND"COLLECTIVE DOSE"

(From ICRP Publication 22 (32), where the present term"collective dose" was referred to as "population dose ")

Risk (R)

In this report the word "risk" is used to mean the probability that agiven individual will incur a deleterious effect as a result of a dose of radia-tion. If pi is the probability of suffering the ith effect, then R = 1 - 7ri(1 - pi).When the different effects are mutually exclusive, the expression mentionedabove reduces to R = Epi. This simplified formulation would also be approxi-mately correct when all piG < <1, even if the effects are not mutually exclusive.

Detriment (G)

The "detriment" in a population is defined as the mathematical concept"expectation" of the harm incurred from a radiation dose, taking intoaccount not only the probabilities of each type of deleterious effect, but theseverity of the effects as well. Thus, if pi is the probability of suffering theeffect i, the severity of which is expressed by a weighting factor gi, then thedetriment G in a group composed of P persons is G = P Eipigi.

Collective dose

This is a measure of the total exposure of the whole body or a specifiedorgan of a population of people. If the number of people receiving dosesbetween H and H +dH is N(H) dH, the collective dose is given by the integral:

f H N(H) dH,

where the integration is carried out over the total dose distribution over theworld population. In some cases, it may be useful to identify a component ofthe collective dose related to a given sub -population, which, for some pur-poses, may be the population of a country or a region. This component maythen be called the collective dose for that sub -population.

72

Annex II

PARTICIPANTS

Temporary Advisers

Mr G. Bresson, Deputy Chief, Radiation Protection Department, AtomicEnergy Commission, Fontenay -aux- Roses, France

Dr P. Courvoisier, Chief, Nuclear Safety Division, Federal Office ofEnergy, Würenlingen, Switzerland

Dr P. Czerski, Associate Professor and Head, Department of Genetics,National Research Institute of Mother and Child, Warsaw, Poland(Co- Rapporteur)

Dr P. Dejonghe, Head, Division of Applied Research, Nuclear EnergyResearch Centre, Mol, Belgium

Dr J.M. D$derlein, Director, Safety Technology Division, Institute forAtomic Energy, Kjeller, Norway (member of drafting committee offinal report)

Dr M. Faber, Professor and Director, Finsen Laboratory, Finsen Insti-tute, Copenhagen, Denmark

Dr S. Halter, Chief Medical Officer, Ministry of Public Health and FamilyWelfare, Brussels, Belgium

Dr V. Klener, Head, Centre of Radiation Hygiene, Institute of Hygieneand Epidemiology, Prague, Czechoslovakia

Dr E. Komarov, Deputy Director, Central Research Institute of Roent-genology and Radiology, Leningrad, USSR (Vice- Chairman)

Dr P. Korringa, Director, Netherlands Institute for Fishery Investiga-tions, Ijmuiden, Netherlands

Dr A. Lafontaine, Professor and Director, Institute of Hygiene and Epi-demiology, Brussels, Belgium

Dr B. Lindell, Professor and Director, Swedish National Institute ofRadiation Protection, Stockholm, Sweden (Chairman)

Dr B.A.J. Lister, Head, Nuclear Environment Branch, Atomic EnergyResearch Establishment, Harwell, Didcot, United Kingdom (memberof drafting committee of final report)

73

Dr F.E. Lundin, Chief, Epidemiology Studies Branch, Division of Bio-logical Effects, Bureau of Radiological Health, Department ofHealth, Education and Welfare, Rockville, MD, USA

Dr P. Oftedal, Professor, Institute for General Genetics, University ofOslo, Norway

Dr E.E. Pochin, National Radiological Protection Board, Harwell, Didcot,United Kingdom

Dr J. Schubert, Professor of Environmental Health Sciences, Divisionof Natural Sciences, Hope College, Holland, MI, USA (Rapporteurand member of drafting committee of final report)

Dr. J. Schwibach, Institute for Radiation Protection, Neuherberg, FederalRepublic of Germany

Mr P. Tanguy, Head, Nuclear Safety Department, Nuclear EnergyCentre - Saclay, Gif- sur -Yvette, France

Representatives of Other Organizations

Commission of the European Communities

Mr H. Eriskat, Chief of Service, Directorate for Health Protection,Luxembourg

International Atomic Energy Agency

Dr F.N. Flakus, Radiological Safety Section, Division of Nuclear Safetyand Environmental Protection, Vienna, Austria

International Commission on Radiological Protection

Dr B. Lindell (of the Swedish National Institute of Radiation Protection,Stockholm, Sweden)

International Radiation Protection Association

Dr A. Lafontaine (of the Institute of Hygiene and Epidemiology,Brussels, Belgium)

74

Organisation for Economic Co- operation and Development

Dr B. Rüegger, Administrator, OECD Nuclear Energy Agency, Paris,France

World Health Organization

Regional Office for Europe

Dr M.J. Suess, Regional Officer for Environmental Pollution Control(Scientific Secretary)

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