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Radioactivity & Waste

GEORGIA STATE UNIVERSITY. Peter Farina 404-651-4866. Radioactivity & Waste. Structure of the Atom. Nucleus. Neutrons. +. +. +. Protons. Electrons (Electron Clouds). Radioactivity. Definition Any spontaneous change in the state of the nucleus accompanied by the release of energy.

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Radioactivity & Waste

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  1. GEORGIA STATE UNIVERSITY Peter Farina 404-651-4866 Radioactivity & Waste

  2. Structure of the Atom Nucleus Neutrons + + + Protons Electrons (Electron Clouds)

  3. Radioactivity Definition Any spontaneous change in the state of the nucleus accompanied by the release of energy. Major Types alpha () particle emission (decay) beta () particle emission (-), positron emission (+) and orbital electron capture (ec) gamma () decay including internal conversion

  4. Ionizing Radiation + + Definition - Any type of radiation possessing enough energy to eject an electron from an atom, thus producing an ion. Major Types of Ionizing Radiation Alpha, Beta, Gamma Alpha Particle Large Mass (nuclei) – Helium Atom with a +2 charge Beta Particle Small Mass - Electron (subatomic particle) No Mass (Electromagnetic Radiation) Gamma Photon and X-Rays

  5.  Decay + + + + + + + + + 238U 4He + 234Th  has a discrete energy that can be measured and related to the parent. The neutron to proton ratio is to low ! 4He Nucleus Ejected from Nucleus +2 Most of the energy associated with  (monoenergetic) This is radioactive!!

  6.  Decay + + + + + + + + + + - 3 products share energy – therefore beta has a continuous range of energies Either too many neutrons or too many protons neutrino Change a neutron into a proton take away - charge Electron (negatron) anti-neutrino Change a proton into a neutron take away + charge (positron)

  7. Electron Capture X-ray X-ray Change proton into neutron

  8.  Decay + + + Gamma Photon + + + + + + - neutrino • Emission of a photon from the nucleus • Most often occurs after  or  emission when nucleus is left in an excited state • Given off with discrete energies • Can measure photon energy and possibly identify parent or +2

  9. Radiation Dosimetry Units Exposure, X: amount of charge produced anywhere in air by the complete stoppage of all electrons liberated by photons in an incremental volume of air per unit mass of air in that volume. Standard International (SI) unit: Coulomb/kilogram (C/kg) Traditional unit: roentgen ( R ) 1 R = 2.58x10-4 C/kg Exposure definition applies only to photons of energy less than or equal to 3 MeV interacting in air.

  10. Radiation Dosimetry Units Absorbed dose: RAD is the energy deposited by any type of ionizing radiation in a volume element of mass. SI unit: gray (Gy) Traditional unit: rad 1Gy = 100 rad Absorbed dose definition applies to all forms of ionizing radiation in any material.

  11. Biological effect of radiation Y at dose X Biological effect of 250 kVp x-rays at dose X Both produce the same biological effect. ) ( Relative Biological Effectiveness and Quality Factor Relative Biological Effectiveness (RBE) Quality factor (Q) radiationQ photon,  1 proton, neutron 10 alpha 20

  12. Relative Biological Effectiveness Ln (S) Shoulder of curve indicates cell repair at low doses No shoulder - no cell repair Neutrons Effect Gamma Photons Dn Dg Same Biological Effect Different Dose from 2 types of radiation Dose

  13. Radiation Dosimetry Units Dose Equivalent Dose equivalent: allows the description of the biological effect of an absorbed dose of a particular type of radiation or mixed radiations for the Human Body. Dose Equivalent (DE) in Rem = Dose in Rads x Q SI unit: sievert (Sv) traditional unit: rem 1 Sv = 100 rem millirem For photons: 1 R  1 rad = 1 rem

  14. PRECAUTIONS FOR AVOIDING UNNECESSARY RADIATION EXPOSURE

  15. External Radiation Exposure Definition: Exposure of the body from radiation originating outside of the body Level of Hazard and Control Depend Upon: 1. Type of Radiation (Alpha, Beta Gamma) 2. Energy of the Radiation (Low or high energy) 3. Dose Rate (Low or high dose rate)

  16. Reducing External Radiation Exposure • Time: • reduce time spent in radiation area • Distance: • stay as far away from the radiation source as possible • Shielding: • interpose appropriate materials between the source and the body

  17. Radioactive Waste We will discuss - • Low Level Radioactive Waste • High Level Radioactive Waste • Mining Tailings

  18. Radioactive Waste Low Level Radioactive waste consists of microcurie, millicurie and at times curie activity waste. (A Curie is a unit of nuclear transformations. 1 Curie is 3.7 x1010 transformations per second)

  19. Radioactive Waste • Low level radioactive waste consists of: • Contaminated solids • liquids • animal carcasses • small sealed sources

  20. Radioactive Waste • Low level radioactive liquids are either: • Incinerated • Deep well injected (not as frequent anymore) • Solidified • Sewer Disposed (Regulations allow curie levels of some isotopes to be sewer disposed of if dilution is large enough)

  21. Radioactive Waste • Radioactive animal carcasses are either incinerated or buried onsite.

  22. Radioactive Waste • Small sealed sources are “Stabilized” in concrete and buried. Stabilized concrete is concrete that is certified to resist wear for a certain time period.

  23. Radioactive Waste • Low level contaminated solid wastes are buried. GSU has it’s solid waste “Supercompacted” at 30,000 psi to reduce the volume to be buried

  24. Most low level wastes come from Government and Utilities. These consist of contaminated solids from nuclear reactor usage and weapon construction. Radioactive Waste

  25. Radioactive Waste • Colleges, research and medical applications account for less than 25% of the low level Radioactive wastes created

  26. Radioactive Waste • Class A low-level radioactive waste is the least hazardous, containing mostly short-lived radionuclides that will be reduced in radioactivity (decay) in a relatively short time. It contains only small amounts of radionuclides that take a relatively short time to decay. Class A waste will be disposed of in concrete canisters that will maintain their shape and strength for hundreds of years.

  27. Radioactive Waste • Class B low-level radioactive waste is more hazardous than Class A waste. Most of it comes from nuclear reactors. It must be in a stable form for disposal and will also be disposed of in concrete canisters. Stabilization can be accomplished by solidifying liquid waste, compacting solid waste, or placing the low-level radioactive waste in a container that will be stable for many years. Class B low-level radioactive waste makes up only a small percent of the waste volume generated; but along with Class C waste, it contains the largest portion of the total radioactivity.

  28. Radioactive Waste • Class C low-level radioactive waste is the most hazardous and must be handled accordingly. It also must be disposed of in a stable form.

  29. Radioactive Waste

  30. Radioactive Waste • There are 3 LLRW Burial sites: • Hanford • Envirocare • Barnwell

  31. Radioactive Waste

  32. Radioactive Waste

  33. Radioactive Waste • Politics of LLRW • Compacts • On-site burial • NIMBY

  34. Radioactive Waste • The compact system was set up by NRC to have all states share in the responsibility of disposal of radioactive waste and to limit waste transport distance. Georgia is in the Southeast compact. • Until 1992, all states within the SE compact (excluding Florida) would host a LLRW landfill on a 20-25 year revolving timetable.

  35. Radioactive Waste • Kentucky was the first (Maxie Flats), then South Carolina (Barnwell). In 1995, North Carolina was to open a site but the citizens protested and sued. The State legislature refused. • North Carolina was then “kicked out” of the S.E. compact and left with no place to dispose of waste. Other States followed N.C.’s lead and refused • This lead to the collapse of the traditional compact system and the

  36. Radioactive Waste

  37. Radioactive Waste In the past, many Universities and companies were allowed to bury their radioactive wastes onsite. Some were allowed to deep well inject liquid radioactive waste.

  38. Radioactive Waste N.I.M.B.Y. Not In My Back Yard The true politics of Hazardous Waste

  39. Radioactive Waste Did North Carolina, by not opening up a waste site, better protect it’s citizens?

  40. Radioactive Waste • High-Level Radioactive Waste is: the irradiated fuel from the cores of nuclear reactors, the liquid and sludge wastes that are left over after irradiated fuel has been reprocessed (a procedure used to extract uranium and plutonium), the solid that would result from efforts to solidify that liquid and sludge from reprocessing.

  41. Radioactive Waste Because there is currently no high level radioactive waste disposal facility, HLRW is held On-Site in water pools

  42. Radioactive Waste Once these Pools are full, Waste is transferred to casks which are also held on-site

  43. Radioactive Waste

  44. Radioactive Waste A HLRW repository is being constructed at Yucca Mountain in Nevada to hold all this waste. NIMBY again is playing a role in the opening

  45. Radioactive Waste YOUR THOUGHTS AND DISCUSSION

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