Estimation of LWR spent fuel composition

In the nuclear transmutation reactor, minor actinide (MA) and fission product (FP) included in high-level waste solution after the reprocessing of spent fuels from the nuclear power plant are transmuted with the nuclear power production. In future, MA and FP compositions in spent fuels will be diversified with the use of high discharged burnup fuels and MOX fuels in LWRs (BWRs and PWRs) taking a leading part of power reactors. In this report, compositions of various LWR spent fuels (discharged burnup: 33, 45 and 60 GWd/tHM, fuel type: UO2 and MOX) are estimated by the burnup calculation code system SWAT and studied by the comparison among various forms of fuels and cooling periods. Main results about MA composition in spent fuels are summarized as follows. (1) Results based on the comparison between real irradiation mock-up calculation and simplified calculations considering only discharged burnup. In the estimation of compositions of transuranium beyond Am, axial burnup profile during the irradiation should be considered. In the estimation of compositions such as Pu-239, 241, Am-241, 243,Cm-244 in BWR fuels, axial void profiles during the irradiation should be considered. (2) Results based on the MA compositions between PWR fuels and BWR fuels in the same discharged burnup. Np-237 compositions are 10% less in BWR-UO2 fuels than PWR-UO2 fuels, but almost same between BWR-MOX fuels and PWR-MOX fuels. Am-241 compositions are a little larger in BWR fuels than PWR fuels in both UO2 type and MOX type. Am-243 compositions are 10% larger in BWR-UO2 fuels than PWR-UO2 fuels, but 20% larger in PWR-MOX fuels than BWR-MOX fuels. Cm-244 compositions are 20% larger in BWR-UO2 fuels than PWR-UO2 fuels, but 20% larger in PWR-MOX fuels than BWR-MOX fuels. Main results about FP compositions in spent fuels are summarized as follows. Buildup quantities of most FPs increase in proportion to burnup. However, those of FPs having less atomic number than Mo are much larger in UO2 fuels than MOX fuels and those of FPs having larger atomic number than Eu are much larger in MOX fuels than UO2 fuels. Buildup quantities of FPs such as Nb, Gd, Ho, Er, Yb strongly depend on power density during the irradiation. The results in this report will be used as basic data for the study of nuclear transmutation reactor. (author)