NPRE 442. Radioactive Waste Classification

1. NPRE 442. Radioactive Waste Classification “My anxiety was to gain real knowledge of the earth.” —Henry Lawson in “Journey to the Center of the Earth” by Jules Verne.

2. Radioactive Waste Classification Waste classification based more on origin than composition. Sometimes “described by what it isn’t than what is it” (Greenpeace) In the U.S. we have (according to the Nuclear Waste Policy Act of 1982): Spent Nuclear Fuel (SNF)

3. Spent Nuclear Fuel About a third of the fuel is replaced every 18 to 24 months. During the combustion of UO2, 235U is fissioned, reduced from about 3% to 1%. 238U from 97 to 94%. Fission products include zinc through the lanthanides.

4. Spent Nuclear Fuel; fission products 235U92 + 1?0 ? 236U92 ? AXZ + a?0 + Q where X can be about 35 different elements from Zn (Z = 30) to Tb (Z = 65), A (mass) can range from 95 to 140, the average value for a is 2.5, and Q is about 200 Mev per fission.

5. Formation of 239Pu93 238U92 + 1?0 ? 239U92 239U92 ? 239Np93 + ß (a neutron becomes a proton) Half-life of 23.5 minutes. 239Np93 ? 239Pu93 + ß Half-life of 2.36 days. Then 239Pu93 has a half-life of 24,110 years

6. Composition of fresh and SNF

7. Radioactive Waste Classification High-Level Wastes (HLW). The Act defined the by-products of fuel reprocessing as HLW. Acidic, liquid wastes that contain U, Pu and fission products.

8. Radioactive Waste Classification Transuranic Wastes (TRU) Atomic number greater than 92 such as 239Pu, 241Am, or 237Np At present, almost all from DOE weapons programs. May include Pu-contaminated clothing, tools, sludge, liquids…

9. Radioactive Waste Classification Low-Level Radioactive Wastes (LLRW or LLW) Wastes derived from the reactor cooling water: filter cakes, sludge, ion exchange resins used to treat water, solids from evaporating liquids. Contaminated protective shoe covers and clothing, wiping rags, mops, filters, equipment and tools.

10. Low-Level Radioactive Wastes 

11. Low-Level Radioactive Wastes  Activation of reactor components creates 14C, 53Ni, 59Ni, and others. Also called induced radioactivity; elements in the core or corrosion products in the cooling water are made unstable (radioactive) by absorbing neutrons.

12. Low-Level Radioactive Wastes Most tritium from boron in the cooling water via neutron capture: 5B10 + 0n1 -> [5B11]* -> 1H3 + 2(2He4) t1/2 = 12.32 years t bio 1/2 = 10 days Also from Li-6 neutron capture, and deuterium activation. Fission products derived from residual U on fuel-rod surfaces during manufacturing.

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14. Spent ion exchange resin.“Reactor water clean up”

15. Low-Level Radioactive Wastes Wastes from nuclear medicine. Radionuclides used in medicine have relatively short half-lives. Technetium-99m used to treat cancer; half life = 6 hours by gamma decay. Radioactive pellets containing 125I and 89Sr mixed with tumor disposed as a biological waste.

16. Low-Level Radioactive Wastes Radioactive wastes from research projects and instruments. Carcasses of animals treated with radioactive materials used in medical or pharmaceutical research. Wastes from the University of Illinois: Division of Research Safety (DRS), Radiation Safety.

17. LLW pick up at UI DRS will pick up radioactive wastes after a form is filled out on-line and approved. Wastes can include solids, liquids, carcasses, and sharps (vials, glassware, plastic containers). DRS uses a waste broker, Chase Environmental in Knoxville, TN. Chase transports and handles the final disposal (more later).

18. LLRW Classification The US Nuclear Regulatory Commission conducted a study to derive LLRW classification criteria. Published in 1981 as “Environmental Impact Statement on 10 CFR part 61 Licensing Requirements for Land Disposal of Radioactive Waste” Report number NUREG-0782

19. “Part 61” Based on the operations and field data form the commercial LLRW sites of that era: Beatty, Maxey Flats, West Valley, Richland, Sheffield and Barnwell (more about these later). Also based on laboratory studies, risk assessment, worst-case assumptions and professional judgment.

20. “Part 61” NRC conducted numerous analyses with different disposal site characteristics, exposed populations, time frames, radionuclide-specific leaching and transport behavior, wastes packaging, climates, costs, and engineered barriers. A reference facility was created for the analyses.

21. The reference facility 20-year operating life. Surveillance, monitoring, and maintenance for 100 years (institutional control). Shallow trenches 100 ft x 591 ft each with a gravel drain. 1-meter thick caps when trench is full.

22. Exposure scenarios considered (examples) The facility is closed. Institutional controls are failing. Exposure to an in advertent intruder who constructs a building (construction worker) on the site or the agricultural intruder who grows crops on the closed site. Exposure limit: 500 mrem/year whole body.

23. Exposure to contaminated groundwater Radionuclides are assumed to leach from the wastes into shallow groundwater. Consumption of radionuclide-contaminated groundwater from the site in each scenario: 1. A water well in the disposal site used by the inadvertent intruder following the 100-year institutional control period. 2. A water well at the site boundary 3. A water well 500 m down gradient from the disposal site. 4. A small stream 1 km away receiving shallow groundwater discharge.

24. Observations 14C, 99Tc, and 129I identified as the major long-term threats to groundwater quality. 3H was the major short-term threat to groundwater quality. Largest doses predicted at the intruder well and sometimes at the boundary well. Of all the radionuclides ever identified have a half-life of days or less. Only about 100 have life-lives greater than 5 years.

25. Classification for shallow land disposal Class A Lowest level No special stability requirements such as solidification or stable waste packages. Cannot use cardboard boxes. Not a threat to the inadvertent intruder beyond 100 years: exposure to intruder is less than 500 mrem/year.

26. Classification for shallow land disposal Class B Next lowest level Special stability requirements required such as solidification or stable waste packages. Not a threat to the inadvertent intruder beyond 100 years; exposure to intruder is less than 500 mrem/year. Must be segregated from Class A wastes at the site.

27. Classification for shallow land disposal Class C Highest level for shallow land disposal. Requires some type of engineered barrier. Special stability requirements required such as solidification or stable waste packages. Will not endanger inadvertent intruder beyond 500 years; exposure to intruder is less than 500 mrem/year. Must be segregated from Class A wastes at the site.

28. Classification for shallow land disposal Greater than Class C (GTCC). Most radioactive. Generally not acceptable for shallow-land disposal. Poses a threat to the inadvertent intruder beyond 500 years. Must be disposed in a geologic repository or an alternative proposed by DOE and approved by NRC.

29. Examples of GTCC wastes Sealed sources commonly 137Cs and 241Am Activated metals decommission wastes, 60Co, 137Cs, 241Am “Other Wastes”

31. Table 2. All as Ci/m3

32. Mixtures of radionuclides Most wastes are mixtures. To classify a waste with more than one radionuclide, we add fractions. For example, Sr-90 (50 Ci/m3) and Cs-137 (22 Ci/m3). Both greater than Class A. Divide concentration by limit then add.

33. Mixtures of radionuclides For 90Sr, 50/150 = 0.33 For 137Cs, 22/44 = 0.5 0.33 + 0.5 = 0.83 Because the result is < 1, it’s Class B

34. Other Wastes Waste Rock (mining debris) “Tailings” Waste slurry of ground rock Uranium mill tailings are not considered LLRW

35. Shortcomings with current LLRW classification system Any substance containing any radionuclide is Class A: there is no “below regulatory-concern” (BRC) level. This adds to the costs of site remediation. Analyses and data 30 years old. The NRC is currently considering revising Part 61 making use of new data and DOE experiences.

36. Waste effluents During the normal operation of a nuclear power plant, waste gases and liquids are vented or released. The amount of radioactivity is monitored (measured), and limited by applicable permits issued by the NCR using criteria from the US. EPA.

37. Waste effluents example Braidwood 1, 2004 data, third quarter sampling (http://www.reirs.com/effluent/EDB_Main.asp) Fission gases 41Ar 2.91 mCi 85Kr 1.52 Ci 133Xe 10.8 Ci 135Xe 18.9 mCi Total 12.4 Ci (12.4% of the limit)

38. Waste effluents example Braidwood 1, 2004 data, third quarter sampling (http://www.reirs.com/effluent/EDB_Main.asp) Liquid waste 139Ba 9.3 uCi 57Co 1.7 uCi 58Co 312 uCi 60Co 1.94 mCi 134Cs 19.3 uCi 137Cs 16.3 uCi 3H 354 Ci Total 354 Ci (1.34% of the limit)

39. Radioactive wastes in general “Front-end Wastes” “Back-end Wastes” U, Th, Rn and Fission products Daughter products Activation products Larger volumes Smaller volumes

40. Comparison of waste types MSW = municipal solid waste. Nonhazardous city trash and yard wastes (2000) RCRA HW = Resource Conversation and Recovery Act Hazardous Wastes (spend organic solvents, acids, listed chemicals, radioactive wastes and more in 1995) CCP = Coal combustion products (coal ash, flue-gas scrubber sludge in 2007) LLRW = Low level wastes disposed at commercial facilities in 2005. 99% Class A waste. 78% from DOE. SNF = Spent nuclear fuel currently being stored—NOT the amount generated per year (as of 2009)

41. Comparison of waste types

42. “Legacy Radioactive Wastes” “Legacy wastes” from WWII and the Cold War era. Not to be confused with utility radioactive wastes. The Hanford site, for example. Between 1943 to 1987, produced about 73 tons of weapons-grade and reactor-fuel grade Pu.

43. Early history of the Hanford facility

44. The Hanford Site Top priority was the production of Pu. Waste management was crude. HLW was discharged to the surface soil when the tanks were full.

45. LLRW and TRU wastes disposed in cardboard boxes in unlined trenches

46. Legacy Wastes at Hanford SNF in pools (about 50,000,000 Ci). Pu and Pu residues. 137Cs and 90Sr in drums (150,000,000 Ci). Liquid wastes in 177 underground tanks (about 215,000,000 Ci). Contaminated soil and groundwater (1.5,000,000 Ci)

47. “Legacy Wastes” at Hanford Ducts, glove boxes, reactor cores, demolition debris, and mixed-LLW wastes; radioactive plus U.S. EPA-defined hazardous wastes such as spent chemicals. The site is slowly being cleaned up by the US DOE with a target date of 2035 for completion.

48. The International Atomic Energy Agency classification system Low Level Waste “Contains enough radioactive material to require action for the protection of people, but not so much that it requires shielding during handling, storage, or transportation.”

49. The International Atomic Energy Agency classification system Intermediate level, short-lived “Waste requires shielding, but little or no provision for heat dissipation, and contains….less than 4,000 Becquerels/g of alpha emitters. The radionuclides generally have a half-life of less than 30 years.”

50. The International Atomic Energy Agency classification system Intermediate level, long-lived “Waste requires shielding, but little or no provision for heat dissipation.The radionuclides generally have a half-life of more than 30 years.”

51. The International Atomic Energy Agency classification system High-level waste “Waste which contains large concentrations of both short- and long-lived radionuclides and is sufficiently radioactive to require both shielding and cooling. The waste generates more that 2 kW of heat per cubic meter.”