1 Radiation Protection Basics

2 Internal Dose Routes of entry –Inhalation –Ingestion –Percutaneous (skin absorption) –Wounds (through openings in skin) Bioassay: measurement of radioisotope burden –Products for sampling: urine, nail clippings, sweat, exhaled air, hair, etc. –In vivo: various whole body scanners

3 A snapshot Radioisotope burden at time of measurement is just that. –Actual amount of radioactivity at time of uptake will be greater Decay Excretion Chemical form of radioisotope is important –Especially, whether soluble or insoluble

4 Fate of contaminants Insoluble –If inhaled, trapped in mucus layer –Eventually shuttled to GI tract –Particle size, pulmonary rates important –Pass through GI tract if ingested. Soluble –Evenly dispersed through body fluid, or –Seeks specific organ (testis, thyroid, colon) –Seeks bone

5 Kinetics of soluble contaminants Body fluids –Filtered by kidneys –Exponential decrease in concentration Organ uptake –Rapidly cleared with sizeable portion take up by organ –Slower, long term release from organ Bone uptake –Much slower turnover, long term deposition

6 Uptake of commonly used radioisotopes Note: levels of interest range from organ system down to molecular Tritium ( 3 H) –Readily exchangeable element –Absorbed through skin, enters total body fluid –Limits on how much can be used before bioassay is required; urine samples 14 C –Critical organ: fat tissue (high C concentration?) –Entry depends on chemical form

7 continued 32 P, 33 P –20% of ingested or inhaled soluble isotope taken up by bone. Lungs and GI tract also affected, depending on route of entry. –Rapidly dividing cells incorporate isotope into nucleic acids, long retention. 35 S –Entry depending on exposure –Testis most at risk

8 continued 125 I, 131 I –Sizeable amount absorbed by thyroid gland. –Iodine isotopes are gamma emitters –Work with Iodine usually requires monitoring by thyroid scan. 51 Cr –Used in immunology research –Excreted through GI tract, so accumulated and concentrated there.

9 Terms related to dose calculations Effective dose –Like rem calculations, except in addition to the radiation type getting a fudge factor, the target organ gets one also. –The rem x the organ sensitivity factor, all added to get a whole body equivalent dose. Committed dose –Dose received from an intake, calculated on the basis of 50 years (70 for children or members of public)

10 Basic Tenets of Radiation Safety ALARA –As Low As Reasonably Achievable –Reflects uncertainty re dangers of low dose radiation. –All work to be carried out in ways that minimize dose as much as possible without huge inconvenience or expense.

11 The 3 Guiding Principles of Radiation protection Shielding –Know the radiation you are working with; choose a barrier that is suitable. Lead for gammas, wax for neutrons; avoid lead for high energy betas Time –The less time you spend in a radiation field, the lower your dose. Distance –The inverse square rule: intensity = 1/r 2 The farther you are away, the lower your dose.

12 Rules reflect concerns Danger: internal contamination –Radioisotopes used in biological research seldom irradiate much, so internal exposure bigger problem –NO EATING, DRINKING, SMOKING or applying of cosmetics. All actions that potentially produce internal exposures. Loss of Control –Careful record keeping –Frequent swipe tests, surveys –Locking of doors, challenging the unauthorized

13 Emergency actions 1. health is first 2. cordon off area 3. maintain constant monitoring 4. contact RSO- he makes further decisions on calling ADH, instructing on cleanup

14 Regulatory Issues Society’s changing views and historical events –Pre-1945: Drinks & baths in radium salts for health –1945: Boom; 1950’s mutants in the movies –1960’s: counterculture + industry arrogance + earthquake zones in California, epicenter of counterculture. “The Atom and the Fault”- good reading –March 1979: Three Mile Island, Pennsylvania –April 1986: Chernobyl, the Ukraine –September 11, 2001: Terrorist attack on NYC Increasing fear, so increased regulatory pressure

15 Who’s in charge? Nuclear Regulatory Commission (NRC) –Reports to Congress –Oversees programs of “agreement states” –Oversees nuclear power industry and governement research facilities. Agreement states –Make up their own rules, within NRC guidelines –Administer their own programs –34 out of 50 currently –Arkansas is an agreement state

16 Who’s in charge-2 Arkansas Department of Health (ADH) –Not as reasonable as in the past –The BIG YELLOW BOOK Rules and Regulations for Control of Sources of Ionizing Radiation” –Universities, hospitals, industries –Issue a license to use and possess radioactive materials On campus: the Radiation Safety Committee

17 The License The license spells out our responsibilities as an institution –We spell out how we will meet the requirements specified by ADH –We get to write the license (within certain guidelines), but we are held explicitly to it! –Examples: how much radioactive material we will have on hand, who gets to use it, how we will police its use and check for contamination, etc.

18 Radiation Safety Manual Mostly for benefit of faculty and staff –Shows ADH that we are in control of program Lists a variety of useful information –Summary of state regulations –License requirements –Administrative structures –General practices and requirements Online: –

19 To use radioactivity on campus Provide proof of training Specific requests for isotope and amounts Clearly described experimental procedures –So committee can evaluate safety Promise to be in compliance with all rules, regulations, and procedures –Includes records of receipt, use, disposal, wipe tests.

20 The biggest issue on campus: Control of material Safety obviously important, but danger posed by isotopes used on campus is minimal.