Validation of Correlations Between Nd Isotopes and Difficult-to-Measure Nuclides Predicted With Burn-Up Calculation Code by Postirradiation Examination

Correlations between Nd isotopes and difficult-to-measure (DTM) nuclides, such as Se-79, Tc-99, Sn-126, and Cs-135, predicted using a calculation code have been validated by postirradiation examination (PIE). The calculation was performed with a burnup calculation code, MVP-BURN, using the updated nuclear data library JENDL-4.0. An irradiated PWR fuel with a burnup of 44.9 GWd/t and a cooling time of 7458 days was used as a standard sample. The concentrations of Nd isotopes in the sample solutions were determined by inductively coupled plasma mass spectrometry (ICP-MS) after purification by two consecutive anion-exchange separations. The ratios of Se-79 and Cs-135 to Nd isotopes (Nd-145, Nd-146, and Nd-145+Nd-146) calculated using MVP-BURN were in good agreement with PIE values within the deviations of 8% and 6%, respectively. This indicates that these calculated ratios are applicable to the scaling factors of Se-79 and Cs-135. For Tc-99 and Sn-126, the calculated values were respectively about 50% and 20% higher than the PIE values. These overestimations were mainly caused by the lack of the contribution of an insoluble residue to the measured concentrations.