Radioactive Materials Safety Training

1. Radioactive Materials Safety Training Massachusetts Institute of Technology Radiation Protection Program

2. Outline • Introduction • Delegation of Authority • Radiation Physics • Units and Quantities • Background and Occupational Radiation Doses • Biological Effects of Ionizing Radiation • Minimizing Radiation Exposures - ALARA • General Radiation Safety and Surveys

3. + - - - - + + + + - - - + - + + - - - + - + Radiation • Radiation: Energy in the form of particles or electromagnetic waves • Ionizing Radiation: Radiation with sufficient energy to remove an electron from an atom or molecule.

4. $- Radioactivity • The process by which unstable atoms spontaneously transform to new atoms* and in the process emit radiation. * The “new atom” may be the same atom in a lower energy state.

5. Units of Activity • Curie (Ci): 37 Billion transformations per second. (2.22 trillion per minute) • Bequerel (Bq): 1 transformation per second. mCi and uCi are common quantities used in the lab (10 uCi up to 50 mCi). 0.0013 uCi (48 Bq) - Ra-226 in a 1 kg rock 0.12 uCi (4400 Bq) - K-40 in your body 330 pCi - C-14 in ¼ lb of beef

6. t T1/2 1 f l t f e 2 ln ( 2 ) l T1/2 Half-Life • Half-life is the amount of time needed for the activity to reach one half of the original amount. Days

7. ExposureR (roentgen): Amount of charge produced per unit mass of air from x-rays and gamma rays. Absorbed Dose rad: Amount of Energy deposited per unit mass of material. 1Gy = 100 rad. Dose Equivalentrem: Risk adjusted absorbed dose. The absorbed dose is weighted by the radiation type and tissue susceptibility to biological damage. 1 Sv = 100 rem. Radiation weighting factors: alpha(20), beta(1), n(10). Tissue weighting factors: lung(0.12), thyroid(0.03), and gonads(0.25). For whole body x or gamma-ray exposure 1 R  1 rad  1 rem Definitions

8. Alpha Decay • Helium Nucleus – Very massive and doubly ionized • Only a hazard via ingestion or inhalation of alpha emitter • Not usually an external radiation hazard • Stopped by paper and dead layer of skin • Uranium, Thorium, Radon and radon daughters

9. Beta Decay • Energetic electron – singly ionized • External hazard to skin and eyes • Internal hazard via ingestion or inhalation of beta emitter • Produces bremsstrahlung radiation • A 1 MeV beta can travel up to 12 feet in air and 1 cm in plastic • Phosphorus, Tritium, Carbon, Sulfur

10. Gamma Decay • X-rays and gamma rays are photons – no charge • External radiation hazard to deep organs and tissues • Internal hazard via ingestion or inhalation of gamma emitter • Lead (high electron density) is good for shielding x and gamma rays • Iodine 125 gammas (30 keV) can be easily stopped with 1/8 inch of lead

11. Neutron shielding material depends on the energy of the neutrons

12. x-ray e- Bremsstrahlung X-Rays plastic electrons • Bremsstrahlung x-ray intensity increases with increasing atomic number of absorber, and the average x-ray energy increases with increasing electron energy. (activity of the source is also a factor) lead

13. Shielding for beta emitting material plastic lead 90Sr

14. Shielding for gamma emitting material Low energy gamma or x-ray High energy gamma or x-ray

15. Typical background is 0.03 mR/hr or 100 cpm GM pancake probe NaI probe Battery check Range selector

16. Background Radiation360 millirem per year Source: BEIR V Report, 1990

17. Annual Occupational Dose Limits * Declared Pregnant Woman

18. Biological Effects • Many groups exposed to ionizing radiation at high levels resulted in adverse effects. • Somatic effects • Prompt - skin burns and cataracts • Delayed - cancer • Genetic effects • Teratogenetic effects

19. X-Ray Burns 500+ rad 5,000+ rad P-32 - 6.5 rad/hr/uCi S-35 - 2.5 rad/hr/uCi

20. Cancer • Radiation can damage cells through two methods; • Production of free radicals and • Direct damage to the DNA. • Risk factor for radiation dose: • 4% increase in risk of dying of cancer for every 100 rem of dose. • Normal cancer risk is 20%.

21. 0.03 r e c n a c m 0.02 o r f h t a e d f o k s i R 0.01 0.00 0 10 20 30 40 50 60 70 Committed Lifetime Dose (rem) Dose Response Relationship Effect is Detrimental risk level is uncertain Predictable Effects Risk Is not Predictable below 20 rem Occupational dose – above background

22. ALARA • ALARA - As Low As Reasonably Achievable • Time • Distance (inverse square law) • Shielding • Contamination Control

23. 2 x 1 . D D 2 1 x 2 Inverse Square Law 45 mrem/hr @ 3.3 cm D - Dose x - distance 5 mrem/hr @ 10 cm 50,000 mrem/hr @ 0.1 cm

24. Radioactive Sealed Sources • Sealed sources used as a source of radiation • Alpha particles • Beta particles • Gamma ray • Bremsstrahlung • Neutron sources • Permanently enclosed in either a capsule or another suitable container designed to prevent leakage or escape of the radioactive material • Inventory and Use records are required

25. Radioactive Sealed Sources • Tested for surface contamination and leakage • Sources may leak radioactive material • Tested usually once every 6 months for beta & gamma emitters that are > 100 uCi • Tested every 3 months for alpha emitters > 10 uCi • Allowable limit is less than 0.005 uCi • A leaking source shall immediately be removed from use • Action to be taken to prevent contamination • Source to be repaired or disposed of • RPP has a shielded storage facility for sources that are not in use.

26. Security and Transportation • All radiation sources must be kept locked up when not in use. • Experiments left unattended should be labeled “Experiment in Progress.” • An up-to-date use log of all sources must be kept at the storage location. • All radiation laboratories will be locked when unattended for extended periods. • When you are the means for security, you must challenge unknown persons entering the lab.

27. General Radiation Safety • No food or beverages in the lab • Keep a survey meter conveniently close by • ALARA - time, distance, and shielding • Label radioactive materials and equipment • Never remove sources from the Jr Physics Lab