ABSTRACT
MeV, yet many in the range 1-2 MeV. All phases of the nuclear fuel cycle have radiation hazard problems. Obviously, most of the stronger radioactive isotopes are generated by nuclear reactors.
The nuclear fuel cycle includes the following:
Mining, milling, and refining of uranium Enrichment to increase the percentage of uranium-235 Fabrication of fuel elements Irradiation of fuel in nuclear reactors Reprocessing of irradiated fuel to recover plutonium and remaining uranium Disposal of low-level waste from various steps in the fuel cycle Disposal of high level waste, either as unprocessed spent fuel or as a solid incorporating the radioactive material discarded from reprocessing
Gamma-shielding requirements are minor in mining and milling, and also in enrichment and fuel fabrication when fresh uranium is used. Recycled uranium, if reprocessing is resumed in the United States, may accumulate
Table 80 Thermal Neutron Capture Cross Section and Gamma-Ray Emission in the Energy Range 0-11 MeV per 100 Captures for Pb and Its Alloying Elements; the Data Correspond to the Most Common Isotopes of These Elements [272]
Photons/IOO captures for energy ranges (MeV) Z Element a".y 0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11
3 Li 33 mb 12.42 4.91 89.33 0 0 0 1.07 4.02 0 0 0 13 AI 235 mb 27.51 8.77 31.25 26.02 37.09 8.12 10.29 38.74 0 0 0 20 Ca 430 mb 24.01 93.49 51.87 17.11 23.03 12.54 43.84 2.16 0 0 0 26 Fe 2.62 b 27.83 24.76 9.54 11.32 11.22 10.93 10.12 58.86 0.82 4.15 0.11 27 Co 38.0 b 93.74 20.54 15.94 17.84 15.66 33.62 34.67 11.39 0 0 0 28 Ni 4.6 b 26.16 6.59 6.05 3.65 3.70 7.45 17.04 14.04 58.99 0 0 29 Cu 3.85 b 81.75 6.02 4.57 4.96 10.10 10.19 16.21 64.87 0 0 0 30 Zn l.Ib 16 63.86 51.02 28.37 21.16 19.64 18.20 18.70 1.30 l.ll 0 47 Ag 63.0 b 68.31 44.12 78.09 42.41 25.12 19.08 5.93 1.74 0 0 0 48 Cd 3620 b 103.99 37.27 98.08 59.40 30.72 24.32 5.58 2.62 0.81 0.29 0 49 In 198 b 33.57 106.96 100.67 37.58 18.27 7.40 0.93 0 0 0 0 50 Sn 625 mb 14.1 61.46 105.42 59.74 32.28 18.01 9.94 6.18 l.l 0.29 0 51 Sb 5.7 b 150 99 58 38" 12b 52 Te 4.7 b >58 82 Pb 170 mb 0 0 0 0 0 0 5.04 94.06 0 0 0 83 Bi 34 mb 0 0 0 0 111.70 0 0 0 0 0 0
enough radioactive impurities to require removal by additional processing or shielding during enrichment and fuel fabrication. Fuel must be removed from the reactor before all of the mU is consumed. Much of the mU and most of the 238U still remain in the burnt fuel element. Decay of the fission products causes high gamma-radiation levels and the generation of much heat. The spent fuel is stored in water-filled basins for several months before transfer to a reprocessing plant. or for several years before removal to storage elsewhere or for disposal as high-level waste.
