1 course : بسم الله الرّحمن الرّحيم chapter 6: internal radiation protection...

1

Course :حمن بسم الله الّر�

حيم الّر�

Chapter 6: Internal Radiation Protection

Omrane KADRI, Ph.D.

[email protected]

Office 2021

Health Safety & Radiation Protection (RAD453)

mailto:[email protected]

2

1. Methods of Entry

2. Internal Exposure Limits

3. Internal Exposure Monitoring

4. Treatment of Internal Contamination

5. Radioactive Waste

6. Guidelines

7. Summary

Outline

Chapter 6: Internal Radiation Protection

3

1. Methods of Entry

Radioactive substances, like other toxic agents, may gain entry

into the body by four processes:

1.Inhalation - Breathing radioactive aerosols or dust.

2.Ingestion - Drinking contaminated water, or transferring

radioactivity to the mouth.

3.Absorption - Entering through intact skin.

4.Injection - Entering through a puncture of the skin with an object

bearing radioactive materials.

4

1. Methods of Entry

Inhalation

Ingestion/Absorption

5


International Commission on Radiological Protection (ICRP).

Radioactive Substances Act 1993 (RSA93).

Ionising Radiation Regulations 1999 (IRR99).

Current UK Legislation

ICRP 60 (1983) - Dose limit recommendations

Incorporated into IRR 1999

Stochastic effects (e.g. Genetic effect)

Radiation worker > 18 yrs - 20 mSv (effective) / yr.

Members of the Public

Average annual dose of 1 mSv/yr averaging over 5 years

Dose in any one year not exceeding 5 mSv.

UK further restricts that contributions from discharges from nuclear installations must not exceed 0.5 mSv/yr

6


Deterministic effects (e.g. Sterility for man or woman)

No need for separate organ dose limit if 20 mSv/yr adopted

Skin, hands, forearms .....................500mSv/yr

Feet and ankles...............................500 mSv/yr

Lens of eye...................................... 150 mSv/yr

•The severity of the deterministic effect with the dose •The probability of the stochastic effect with the dose

7


Annual Limit on Intake (ALI)

Intake (of radioisotope) which would give an effective dose equal to the annual dose of a radiation worker when we calculate the accumulated dose over a period of 50 years.

The value of ALI for a particular isotope depends on :The route of entryThe chemical properties of the isotopeThe particle size (especially in the case of inhalation)The types and energies of the radiation and the physical and biological half-lifeConcentration in particular organs, etc

E.g. 125I is given as 2.7 MBq (inhalation) and 1.3 MBq (ingestion)

8


9

3. Internal Exposure Monitoring

Internally deposited radioactive material can be monitored by measuring the radiation emitted from the body or by measuring the amount of radioactive material contained in the urine or feces. Such monitoring techniques are called "bioassays".

Bioassays are required whenever surveys or calculations indicate that an individual has been exposed to concentrations of radioactive material in excess of established limits or when required by State or Federal regulations.

In internal contamination the radio-elements are in contact with living cells. This position does not much alter the risk induced by beta or X

radiation. By contrast, the risk associated with alpha radiation, which did not exist for the other modes of exposure, is major here .

The presence of radio-elements in an organism is not always pathological, a certain number of atoms, of which the organism is constructed, are

radio-elements (example: K-40) .

10


Internal contamination

Reduce absorption and internal deposition

Enhance excretion of absorbed contaminants

11


Basic principles of treatment of internal contamination

-Saturation of target organ, e.g. potassium iodide for iodine isotopes

-Complex formation at site of entry or in body fluids followed by rapid excretion, e.g. DTPA for Pu isotopes

-Acceleration of metabolic cycle of radionuclide by isotope dilution, e.g. water for 3H

-Precipitation of radionuclide in intestinal lumen followed by faecal excretion e.g. barium sulphate administration for 90Sr

-Ion exchange in gastrointestinal tract, e.g. Prussian blue for 137Cs

12


Methods of treatment of internal contamination

13

Application of KI in tablets allows to prevent the harmful effects of internal radiation caused inhalation or per reception of iodine-131

Time after incorporation of iodine-131, hours

Time before inhalation Time after inhalation


Application of preparations of stable iodine

Single exposures are treated by forced fluid intake: Enhanced fluid intake e.g. water, tea, beer, milk has dual

value of diluting tritium and increasing excretion (accelerated metabolism)

Biological half-life of tritium - 10 days Forcing fluids to tolerance (3-4 L/day) reduces biological half-

life to 1/3-1/2 of normal value

14


Diluting agents: water for tritium – 3H

137Cs - physical half-life Tp=30 years; biological half-life in adults average Tb=110 days, in children 1/3 of this

Prussian blue effective means to reduce body's uptake of caesium, thallium and rubidium from the gastrointestinal tract

Dosage of prussian blue: one gram orally 3 x daily for 3 weeks reduces Tb to about 1/3 normal value

15


Ion exchange: prussian blue for 137Cs

Ca-DTPA is 10 times more effective than Zn-DTPA for initial chelation of transuranics. Must be given as soon as possible after accident

After 24 hours, Ca-DTPA and Zn-DTPA equally effective Repeated dosing of Ca-DTPA can deplete body of zinc and

manganese Dosage of Ca-DTPA and Zn-DTPA:

1 g iv. or inhalation in a nebulizer Initially: 1 g Ca-DTPA, repeat 1 g Zn-DTPA daily up to five days

if bioassay results indicate need for additional chelation Pregnancy: First dose Zn-DTPA instead of Ca-DTPA

16


Chelation agents: DTPA for heavy metals and transuranic elements

Dimercaprol (BAL) forms stable chelates, and may therefore be used for the treatment of internal contamination with

mercury, lead, arsenic, gold, bismuth, chromium and nickel

Deferoxamine (DFOA) effective for chelation of 59Fe

Penicillamine (PCA) chelates with copper, iron, mercury, lead, gold. Superior to BAL and Ca-EDTA for removal of

copper (Wilson’s disease)

17


Additional chelating agents

18


Three routes for disposal :

1. Liquid waste, via disposal sink.

2. Solid waste to authorised contractor, via RPS.

3. Gaseous disposal, via authorised fume cupboard.

19


Radioactive Liquid Waste:

Aqueous waste should be diluted before disposal

Use only marked disposal sinks

Run water through sink to disperse waste (avoid splashes)

Log all activity discharged – very important

SEPA will ask you to justify your disposal figures

Do not exceed your monthly disposal limits expensive!

No organic solvents

20


Radioactive Solid Waste :

Segregate the waste into 3H/14C; 32P; others.

Dispose to marked bins only.

Do not put non-radioactive waste into these bins.

Do not put biohazard waste into these bins.

Do not put radioactive waste into ‘normal’ waste bins.

Contents of bins must be labelled.

Units must be in Bq, kBq, MBq etc – legal document.

21

6. Guidelines

Three basic methods to control radioactive contamination which can lead to

internal radiation exposures are:

1.Minimize the amount of radioactive material being handled. Use only as much

activity that is needed.

2.Contain the radioactive material. Different physical states (gas, liquid, solid)

require different containment techniques. Generally, two levels of containment

should be provided. For example, a vial containing a stock solution of radioactive

material should be properly capped and placed or transported using a drip tray or

other similar device lined with absorbent paper.

3.Follow established laboratory procedures. Proper protective clothing,

designated work areas, surface contamination monitoring, etc., are required in all

laboratories that use radioactive material.

22

7. Summary

The internal hazard is the principal hazard encountered in the use of unsealed radioactive materials.

There is NO shielding from an internal intake.

There is NO distance protection from an internal intake.

Irradiation occurs 24 hours/day.

Emissions will be dissipated in the cells of the body.

Certain isotopes will concentrate in particular organs.

•Take a white paper•Write (on top of the page):

–Quiz N° 3 (RAD 453)–Full Name:–Student Number:

•Answer:

24

Quiz N° 3

1 course : بسم الله الرّحمن الرّحيم chapter 6: internal radiation protection...

Documents