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Radiation Protection Basics

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2Internal 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

3A 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

4Fate 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

5Kinetics 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

6Uptake of commonly used radioisotopes

• Note: levels of interest range from organ system down to molecular

• Tritium (3H)– Readily exchangeable element– Absorbed through skin, enters total body fluid– Limits on how much can be used before bioassay is

required; urine samples

• 14C– Critical organ: fat tissue (high C concentration?)– Entry depends on chemical form

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• 32P, 33P– 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.

• 35S – Entry depending on exposure– Testis most at risk

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• 125I, 131I – Sizeable amount absorbed by thyroid gland.– Iodine isotopes are gamma emitters– Work with Iodine usually requires monitoring by

thyroid scan.

• 51Cr– Used in immunology research– Excreted through GI tract, so accumulated and

concentrated there.

9Terms 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)

10Basic 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.

11The 3 Guiding Principlesof 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/r2 The farther

you are away, the lower your dose.

12Rules 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

13Emergency 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.

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14Regulatory 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

15Who’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

16Who’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

17The 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.

18Radiation 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: – http://ehc.astate.edu/Radiation.htm

19To 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.

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The biggest issue on campus:Control of material

Safety obviously important, but danger posed by isotopes used on

campus is minimal.