second_lecture - NPRE 442. Radioactive Waste Classification...

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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 . 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)
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2 Spent Nuclear Fuel About a third of the fuel is replaced every 18 to 24 months. During the combustion of UO 2 , 235 U is fissioned, reduced from about 3% to 1%. 238 U from 97 to 94%. Fission products include zinc through the lanthanides. Spent Nuclear Fuel; fission products 235 U 92 + 1 η 0 236 U 92 A X Z + a η 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.
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3 Formation of 239 Pu 93 238 U 92 + 1 η 0 239 U 92 239 U 92 239 Np 93 + β (a neutron becomes a proton) Half-life of 23.5 minutes. 239 Np 93 239 Pu 93 + β Half-life of 2.36 days. Then 239 Pu 93 has a half-life of 24,110 years Composition of fresh and SNF After 0 20 40 60 80 100 U -235 -236 Pu-239 Pu-240 Pu-241 Pu-242 Fission prod u cts U-238 Percent Before 0 20 40 60 80 100 U-2 3 5 U-236 Pu- 2 42 Fision products U- 38 After 0 1 2 3 4 U-235 U-236 Pu-239 Pu-240 Pu-241 Pu-242 Fission products
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4 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. Radioactive Waste Classification Transuranic Wastes (TRU) Atomic number greater than 92 such as 239 Pu, 241 Am, or 237 Np At present, almost all from DOE weapons programs. May include Pu-contaminated clothing, tools, sludge, liquids…
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5 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. Low-Level Radioactive Wastes
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Low-Level Radioactive Wastes Activation of reactor components creates 14 C, 53 Ni, 59 Ni, and others. Also called induced radioactivity; elements in the core or corrosion products in the cooling water are made unstable (radioactive) by absorbing neutrons. Low-Level Radioactive Wastes Most tritium from boron in the cooling water via neutron capture: 5 B 10 + 0 n 1 -> [ 5 B 11 ] * -> 1 H 3 + 2( 2 He 4 ) t 1/2 = 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
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second_lecture - NPRE 442. Radioactive Waste Classification...

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