1 Course : بسم الله الرّحمن الرّحيم Chapter 6: Internal Radiation Protection Omrane KADRI, Ph.D. Office 2021 Health Safety & Radiation Protection (RAD453)

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 2. Internal Exposure Limits 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 2. Internal Exposure Limits

Deterministic effects (e.g. Sterility for man or woman) No need for separate organ dose limit if 20 mSv/yr adopted Skin, hands, forearms mSv/yr Feet and ankles mSv/yr Lens of eye mSv/yr The severity of the deterministic effect with the dose The probability of the stochastic effect with the dose 7 2. Internal Exposure Limits

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 entry The chemical properties of the isotope The particle size (especially in the case of inhalation) The types and energies of the radiation and the physical and biological half-life Concentration in particular organs, etc E.g. 125 I is given as 2.7 MBq (inhalation) and 1.3 MBq (ingestion) 8 2. Internal Exposure Limits

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.

 I n 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) Treatment of Internal Contamination Internal contamination

 Reduce absorption and internal deposition  Enhance excretion of absorbed contaminants Treatment of Internal Contamination 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 3 H -Precipitation of radionuclide in intestinal lumen followed by faecal excretion e.g. barium sulphate administration for 90 Sr -Ion exchange in gastrointestinal tract, e.g. Prussian blue for 137 Cs Treatment of Internal Contamination 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 4. Treatment of Internal Contamination 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 Treatment of Internal Contamination Diluting agents: water for tritium – 3 H

 137 Cs - physical half-life T p =30 years; biological half- life in adults average T b =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 T b to about 1/3 normal value Treatment of Internal Contamination Ion exchange: prussian blue for 137 Cs

 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 Treatment of Internal Contamination 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 59 Fe  Penicillamine (PCA) chelates with copper, iron, mercury, lead, gold. Superior to BAL and Ca-EDTA for removal of copper (Wilson’s disease) Treatment of Internal Contamination Additional chelating agents

18 5. Radioactive Waste 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 5. Radioactive Waste 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 5. Radioactive Waste 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.

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Take a white paper Write (on top of the page): – Quiz N° 3 (RAD 453) – Full Name: – Student Number: Answer: 24 Quiz N° 3