Effect of Neutron Induced Reactions of Neodymium-147 and 148 on Burnup Evaluation

Burnup is an important parameter in criticality safety evaluations of spent nuclear fuel in which burnup credit is taken into account. The Neodymium-148 method is widely used to evaluate the burnup of post irradiation examination (PIE) samples, and it is well known for its good accuracy. However, accuracy of the evaluated burnup values may be affected by the neutron capture reaction of 147Nd and 148Nd. Moreover, in the analysis of PIE data from a PWR, the calculation results of 148Nd have more than a 1% deviation from the experiment. In this study, the contribution of neutron capture reactions of 147Nd and 148Nd to the amount of 148Nd is discussed. The PIE data analyses using new evaluation of 147Nd capture cross section show that the JENDL-3.2 cross section data is overestimated. The change in the amount of 148Nd due to both reactions is less than 0.7% under normal reactor operation conditions. In particular, it is in the 0.1% range if burnup is approximately 30 GWd/t for a BWR and 40 GWd/t for a PWR.