The representative radioactive nuclides in this study (Table 20.5) include not only the important nuclides for various evaluations of radioactive wastes but also the nuclides whose concentrations have been measured in the past, which will be useful for the validation of numerical evaluations.

Target nuclides of sensitivity analyses were selected on the basis of two criteria. The first was that the concentrations of activation products be larger than or comparable to the concentration of fission products generated from impurity ura­nium in the materials. The contents of impurity uranium in Zircaloy-2 and SUS304 stainless steel were 0.00035 wt% and 0.0001 wt% [5], respectively. This value in INCONEL alloy is unknown. The second criterion was that the concentrations of activation products be comparatively large. In these analyses, activation products with concentrations more than 1 x 10~9 g/t were chosen.

The concentrations of activation products larger than 1 x 10~9 g/t and fission products generated from impurity uranium are shown in Table 20.6. The fission products were calculated under the condition that the initial composition contains only the uranium impurity. Table 20.6 also shows the selected target nuclides that satisfy the foregoing criterion: 17 nuclides in Zircaloy-2 and Zircaloy-4, 8 nuclides in SUS304 stainless steel, and 16 nuclides in INCONEL alloy were selected as the target nuclides of sensitivity analyses.

No. Nuclide Half-life No. Nuclide Half-life No. Nuclide Half-life 1 H-3 12.3 years 21 Se-79 377.0 E3 years 41 Cs-137 30.1 years 2 Be-10 1.5 E6 years 22 Rb-87 48.1 E9 years 42 Ba-133 10.5 years 3 C-14 5.7 E3 years 23 Sr-90 28.8 years 43 Sn-126 198.0 E3 years 4 Na-22 2.6 years 24 Nb-94 20.3 E3 years 44 Sb-124 60.2 days 5 Si-32 153.0 years 25 Nb-95 35.0 days 45 Sb-125 2.8 years 6 S-35 87.5 days 26 Mo-93 4.0 E3 years 46 Ce-141 32.5 days 7 Cl-36 301.0 E3 years 27 Mo-99 2.7 days 47 Ce-144 284.9 days 8 K-40 1.2 E9 years 28 Tc-99 211.1 E3 years 48 Eu-152 13.5 years 9 Sc-46 83.8 days 29 Tc-99m 6.0 hours 49 Eu-154 8.6 years 10 Ca-41 102.0 E3 years 30 Zr-93 1.5 E6 years 50 Eu-155 4.8 years 11 Cr-51 27.7 days 31 Zr-95 64.0 days 51 Gd-153 240.4 days 12 Mn-54 312.1 days 32 Ru-103 39.3 days 52 Ho-166m 1.2 E3 years 13 Fe-55 2.7 years 33 Ru-106 1.0 years 53 Hf-181 42.4 days 14 Fe-59 44.5 days 34 Ag-108m 438.0 years 54 Au-199 3.1 days 15 Co-57 271.7 days0 35 Ag-llOm 249.8 days 16 Co-58 70.9 days 36 1-129 15.7 E6 years 17 Co-60 5.3 years 37 Cd-113m 14.1 years 18 Ni-59 76.0 E3 years 38 1-131 8.0 days 19 Ni-63 100.1 years 39 Cs-134 2.1 years 20 Zn-65 244.1 days 40 Cs-135 2.3 E6 years aHalf-life is referred to ORLIBJ40 decay library bE3 years = 103 years, E6 years = 106 years °Half-life of Co-57 is not contained in ORLIBJ40, so it is referred to [4]