Comparison of Calculated Values with Measured Values on the Amount of TRU and FP Nuclides Accumulated in Gadolinium Bearing PWR Spent Fuels

Destructive analyses for five spent fuel samples taken from a Gd bearing fuel assembly were done. The measured amounts of actinides of ^234-238U, ²³⁷Np, ^238-242p_u 241,242m,243Am ^242,244Cm, and fission products of ¹³⁴Cs and ¹⁵⁴Eu were used for evaluating the accuracy of calculation made by CASMO-MICBURN and ORIGEN-2 codes. The effect of Gd on the neutron spectrum was taken into account in the CASMO-MICBURN calculation.

The amounts of ²³⁵U, ²³⁹Pu and ²⁴¹Pu calculated by CASMO-MICBURN agreed well with the observed values within about 3%. On the other hand, the amounts obtained from ORIGEN-2 calculation showed lower values than those observed, especially by —12% in average in ²³⁵U for Gd₂0₃U0₂ fuel. The main cause of this large difference may be attributed to the effect of Gd on the neutron spectrum. The amounts of the other actinides by both calculation codes revealed no significant difference in nearly 10% except for ^242mAm, in which a large fluctuation among the samples was observed. About 10% difference between the measured values and the calculated values was also observed for ¹³⁴Cs, but the calculated values for ¹⁵⁴Eu showed a significant difference from measured values.