Technical note

Natural radioactivity of Indian building materials andby-products

Viresh Kumara, T.V. Ramachandranb, Rajendra Prasada, *aDepartment of Applied Physics, Z.H. College of Engineering and Technology, Aligarh Muslim University, Aligarh 202 002, India

bEnvironmental Assessment Division, Bhabha Atomic Research Centre, Mumbai 400 085, India

Received 8 May 1998; received in revised form 16 July 1998; accepted 4 August 1998

Abstract

Conventional building materials and by-products from coal power plants which are being used or have thepotential for use in buildings in India were analysed for natural radioactivity due to the presence of 226Ra, 232Th

and 40K using g-ray spectroscopy. The materials examined in this work showed the radioactivity levels below thelimit estimated from radium equivalent activity the criterion formula for g-activity suggested for acceptableradiation doses attributable to building materials in OECD countries. # 1999 Elsevier Science Ltd. All rightsreserved.

Keywords: Radium; Thorium; Potassium-40; Fly ash; Concrete

1. Introduction

For the assessment of possible radiological risks to

human health, it is important to have a knowledge of

the radioactivity levels of the materials used in build-

ings. The measurements will also help in the develop-

ment of standards and guidelines for the use and

management of these materials. Several natural ma-

terials and those derived from industrial wastes and

by-products have been shown to have high levels of

radioactivity in many countries (Hamilton, 1971;

Stranden, 1976; Umwelt-radioactivitat und Strahlen-

belastung, 1976; UNSCEAR, 1977; Harley, 1978; Kolb

and Schmier, 1978; OECD, 1979; Krieger, 1981; Jojo

et al., 1994).

In recent years there has been increasing interest in

using waste products as substitutes for natural pro-

ducts in building materials. Fly ash, the particulate by-

product of coal combustion, has been found to have a

higher concentration of radionuclides than the coal

itself (Eisenbud and Petrow, 1964; Coles et al., 1978;

Jojo et al., 1994). In recent years ¯y ash has been used

as a replacement of sand and cement in premixed con-

crete, manufacture of blended ¯y ash portland cement,

aerated concrete, ¯y ash clay bricks and blocks and for

the ®lling of underground cavities etc.

Due to the high ash content (30±50%) of Indian

coal (Powell et al., 1991), it is estimated that coal ash

production is likely to exceed 1.3�1011 tonne per year

by the turn of the century. In a thermal power plant

consuming about 10 tonnes of coal per day, the mobil-

ization of radioactivity due to 238U alone is about 1850

KBq. (UNSCEAR, 1982). 238U supports a series of 13

main decay products and several other radionuclides

including radon which is considered to be the largest

single source of public radiation exposure (Cohen,

1982).

In the present work, concentration of 226Ra, 232Th

and 40K contents of materials has been estimated using

g-ray spectroscopy. Common natural materials and the

by-products of coal power plants which are being

used, or have potential for use, in building construc-

tion were selected for the study. The results are dis-

cussed in the light of the criterion formula for

Applied Radiation and Isotopes 51 (1999) 93±96

0969-8043/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved.

PII: S0969-8043(98 )00154-7

AppliedRadiation andIsotopes

PERGAMON

* Corresponding author. Tel.: +91-571-403169; fax: +91-

571-400-528; e-mail: apto1rp@amu.nic.in.

acceptable radiation dose rates attributable to buildingmaterials.

2. Experimental methods

The materials investigated were (i) natural materialsand the bricks, etc. made from these materials and (ii)particulate by-products of a coal power plant havingthe potential for use in large quantities in the building

industry. The materials were collected from construc-tion sites, as well as from various agencies supplyingraw materials for building construction. Fly ash and

slag samples were obtained from two large thermalpower stations (Kasimpur and Parichha) of the stateof Uttar Pradesh (India). These materials are represen-

tative of this huge state of India.Most of the materials were studied `as received'.

Some were dried and sieved, while others (bricks, etc.)

were crushed and sieved. Aliquots of 250 g of thesamples were ground, sieved through a 100 mesh sieve,dried and sealed in a cylindrical plastic container 4.5cm in diameter and 7.0 cm in height. They were stored

for at least 30 days before counting so as to ensurethat 226Ra and 224Ra attain radioactive equilibriumwith their daughters.

The spectrometer system consisted of a 12.5�10.0cm NaI(T1) detector kept inside the lead shield of 15cm thickness lined with 30 mm each of cadmium and

copper on all sides. The internal dimensions of theshield were 23�23�60 cm. The detector was coupledto a 256 multichannel pulse height analyzer and the

system was calibrated for the g-energy range 80 KeVto 3.2 MeV. The energy regions for 40K, 1.46 MeV g-rays, 226Ra, 1.76 Mev g-rays and 232Th, 2.62 Mev g-rays were chosen as 1.39±1.52; 1.64±1.98 and 2.42±

2.68 MeV, respectively. The samples were counted for0400±1000 min depending upon the activity levels pre-

sent in the samples. To obtain net counts backgroundwas subtracted by the method of Ramachandran andSubba Ramu (1989). The counts due to each element

were converted to concentrations using standardizedsource parameters (Lalit and Ramachandran, 1976).

3. Results and discussion

Table 1 presents the mean concentrations of radium,

thorium and potassium in the various building ma-terials and by-products investigated in this work.Hamilton (1971) de®ned a common index called the

`radium equivalent activity' to obtain the sum of activi-

ties for the comparison of the speci®c radioactivities ofmaterials containing Ra, Th and K. Krisiuk et al.(1971) and Stranden (1976) estimated that 370 Bq/Kg

(10 pCi/g) of 226Ra, 260 Bq/Kg (7 pCi/g) of 232Th and4810 Bq/Kg (130 pCi/g) of 40K produce the same g-ray dose rate. Thus the radium equivalent activities

(Raeq) may be calculated using the formula:

Raeq � ARa � �ATh � 1:43� � �AK � 0:077�, �1�where ARa, A Th and AK are the activities in Bq/Kg

(pCi/g) of 226Ra, 232Th and 40K respectively. The rangeof radium equivalents of the samples and the meanradium equivalent of their total activity are also shown

in Table 1.There are variations in the radium equivalent activi-

ties of di�erent materials and also within the same

type of materials. The results may be important fromthe point of view of selecting suitable materials for usein building construction. Large variations in radiumequilibrium activities may suggest that it is advisable

Table 1

Speci®c radioactivities and radium equivalent activities of building materials and by-products used in the building construction in

India

Material No. of

samples

Mean speci®c activity

(Bq/kg)

Criteria

formula result

Radium equivalent

(Bq/kg)

226Ra 232Th 40K range mean

(1) soil 1 42.9 60.7 435.9 0.22 ± 163.2

(2) sand 2 43.7 64.4 455.8 0.23 163.3±178.8 170.8

(3) Portland cement 1 37.0 24.1 432.2 0.15 ± 104.7

(4) plaster of cement and sand 1 39.6 56.2 201.7 0.18 ± 135.4

(5) ¯y ash 9 45.1 39.9 88.4 0.15 93.2±157.3 109.2

(6) slag 3 67.3 77.7 145.1 0.26 186.1±193.1 189.8

(7) clay brick (un®red) 1 38.5 48.1 347.8 0.18 ± 133.9

(8) clay brick (®red) 1 48.1 52.2 381.1 0.21 ± 151.7

(9) clay brick (®red and plastered

with cement and sand)

1 47.7 28.9 354.1 0.16 ± 116.2

V. Kumar et al. / Applied Radiation and Isotopes 51 (1999) 93±9694

to monitor the radioactivity levels of materials from a

new source, before adopting it for using as a building

material.

For limiting the radiation dose from building ma-

terials in Germany to 1.5 m Gy/yr Krieger (1981) pro-

posed the following conservative model based on

in®nitely thick walls without windows and doors to

serve as a criterion:

ARa

370 Bq=kg� ATh

260 Bq=kg� AK

4810 Bq=kg<1, �2�

where ARa, A Th and AK are the mean activities of226Ra, 232Th and 40K, respectively, in Bq/kg in building

materials. This criterion considers only the external ex-

posure risk due to g-rays and corresponds to a maxi-

mum Raeq of 370 Bq/kg for the material. The model

was also accepted by the former Soviet Union (Krisiuk

et al., 1971) and Norway (Stranden, 1976). These very

conservative assumptions were later corrected by the

authors after considering a ®nite thickness of walls,

windows and doors through the application of weigh-

ing factor of 0.7 in each case (Keller and Muth, 1990).

Therefore, the maximum permissible concentrations

were increased by a factor of 2. That means

ARa

740 Bq=kg� ATh

520 Bq=kg� AK

9620 Bq=kg<1: �3�

Based on the criterion formula (Eq. (3)) for g-ac-tivity, the results presented in Table 1 indicate that the

commonly used Indian building materials examined in

this work could be used in building construction with-

out exceeding the proposed radioactivity criterion

level. It is desirable to select the materials of low

speci®c radioactivity for use in building construction.

Table 2 compares the speci®c radium equivalent ac-

tivities of some of the Indian building materials with

those of similar materials from other countries.

4. Conclusions

The natural radioactivity of a variety of Indian

building materials and by-products of coal ®red powerplants has been measured using g-ray spectroscopy.Conventional building materials such as clay bricks,sand, cement, ¯y ash and slag were found to have

radioactivity levels below the acceptable limit of ac-tivity estimated from the criterion formula for g-ac-tivity suggested for use in OECD countries.

References

Beretka, J., Mathew, P.J., 1985. Natural radioactivity of

Australian building materials, industrial wastes and by-pro-

ducts. Health Phys. 48, 87.

Cohen, B.L., 1982. Health e�ects of radon from coal burning.

Health Phys. 42, 725.

Coles, D.G., Ragaini, R.C., Ondov, J.M., 1978. Behaviour of

natural radionuclides in Western coal-®red power plants.

Environ. Sci. Technol. 12, 442.

Eisenbud, M., Petrow, H.G., 1964. Radioactivity in the at-

mospheric e�uents of power plants that use fossil fuels.

Science 144, 288.

Hamilton, E.I., 1971. The relative radioactivity of building

materials. Am. Ind. Hyg. Ass. J. 32, 298.

Harley, J.H., 1978. Radioactivity in building materials. In:

Moghissi, A.A., Paras, P., Carter, M.V., Barker, R.F.

(Eds.). Radioactivity in Consumer Products, NUREG/CP-

0001. US Nuclear Regulatory Commission, Washington,

DC, p. 332.

Jojo, P.J., Rawat, A., Kumar, A., Prasad, R., 1994. Trace

uranium analysis in Indian coal samples. Nucl. Geophys. 7,

445.

Keller, G., Muth, H., 1990. Natural radiation exposure in

medical radiology. In: Scherer, E., Stre�er, Ch., Tolt, K.R.

(Eds.). Radiation Exposure and Occupational Risks.

Springer Verlag, Berlin.

Kolb, W., Schmier, H., 1978. Building material induced radi-

ation exposure of the population. Environ. Int. 1, 69.

Table 2

Comparison of the mean radium equivalent activities (Raeq) of Indian building materials and by-products with other countries (all

data in Bq/kg)

Material India

(present

work)

Australia

(Beretka and

Mathew, 1985)

Finland

(OECD, 1979)

Germany

(OECD, 1979:

Krieger, 1981)

Norway

(Stranden, 1976)

Sweden

(OECD, 1979)

UK

(Hamilton, 1971:

O'Riordan and

Hunt, 1977)

(1) sand 170.8 70.3 177.6 59.2 18.5

(2) Portland cement 104.7 114.7 99.9 70.3 7.4 140.6 59.2

(3) ¯y ash 109.2 355.2 451.4

(4) slag 189.8 340.4 214.6 421.8

(5) clay brick 151.7 218.3 240.5 207.2 27.4 351.5 170.2

V. Kumar et al. / Applied Radiation and Isotopes 51 (1999) 93±96 95

Krieger, R., 1981. Radioactivity of construction materials.

Betonwerk Fertigteil Techn. 47, 468.

Krisiuk, E.M., Tarasov, S.I., Shamov, V.P., Shalak, N.I.,

Lisachenko, E.P., Gomelsky, L.G., 1971. A Study on

Radioactivity in Building Materials. Research Institute for

Radiation Hygiene, Leningrad.

Lalit, B.Y., Ramachandran, T.V., 1976 Environm. Q. HASL-

306, I±21.

Organization for Economic Cooperation and Development

(OECD), 1979. Exposure to radiation from the natural

radioactivity in building materials. Report by a group of

experts of the OECD Nuclear Energy Agency. OECD,

Paris.

O'Riordan, M.C., Hunt, G.J., 1977. Radiological controls for

construction materials. In: Proceedings of the 4th

International Congress of Radiation Protection Assn. 3.

IRPA, Vienna, p. 1053.

Powell, M.A., Hart, B.R., Fyfe, W.S., Sahu, K.C., Tripathy,

S., Samuel, C., 1991. Geochemistry of Indian coal and ¯y

ash, environmental considerations. In: Proceedings of the

International Conference of the Environmental Impact of

Coal Utilization, Bombay, p. 23.

Ramachandran, T.V., Subba Ramu, M.C., 1989. Estimation

of indoor radiation exposure from the natural radioactivity

content of building materials. Encology 3, 21.

Stranden, E., 1976. Some aspects on radioactivity of building

materials. Physica Norvegica 8, 167.

Umwelt-radioactivitat und Strahlenbelastung, 1976. Nat-

urliche Radioactivitat in Baumaterialen, Der Bundes-

minister des Innern, Referat O�enlichkeits Arbeit, Bonn.

United Nations Scienti®c Committee on the E�ects of Atomic

Radiation (UNSCEAR), 1977. Sources and e�ects of ioniz-

ing radiation. Report to the General Assembly. United

Nations, New York.

United Nations Scienti®c Committee on the E�ects of Atomic

Radiation (UNSCEAR), 1982. Report to the General

Assembly with annexes, United Nations, New York, p. 108.

V. Kumar et al. / Applied Radiation and Isotopes 51 (1999) 93±9696