1 Radiation Protection Basics http://www.ansto.gov.au/__data/assets/image/0005/8762/Training_DSC_0114.jpg Internal Dose 2 • 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 A snapshot 3 • 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 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 4 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 5 Uptake of commonly used radioisotopes 6 • 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 continued • 7 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 continued • 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. 8 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) 9 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. 10 The 3 Guiding Principles of Radiation protection 11 • 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. Rules reflect concerns 12 • 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 Emergency actions • • • • 13 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. http://www.georgetown.edu/gumc/ehs/chemsafe/images/spill.gif http://www.worldprayer.org.uk/images/user/Footsteps%20web1.gif Regulatory Issues 14 • 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 Who’s in charge? 15 • 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 Who’s in charge-2 16 • 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 The License 17 • 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. 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: – http://ehc.astate.edu/Radiation.htm 18 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. 19 20 The biggest issue on campus: Control of material Safety obviously important, but danger posed by isotopes used on campus is minimal.