Non-Destructive and Destructive Measurements on Burnup Characteristics of Japan Power Demonstration Reactor-I Full-Core Fuel Assemblies

A non-destructive γ-ray spectrometry technique was applied to 72 spent fuel assemblies discharged from the Japan Power Demonstration Reactor-I. The assemblies were dissolved at the Tokai Reprocessing Plant, and 19 batch-samples taken out of the dissolver vessels were subjected to detailed chemical analysis. Burnups and Pu/U atom ratios were obtained from the non-destructively measured 137 Cs activities and the 134 s/ 137 Cs activity ratios, respectively, by making reference to the correlations established in an experiment on fuel rods of a typical assembly in the core. The results were compared with those from chemical analysis, and a good agreement was found between the values obtained from the respective methods. A small deviation observed partly in the correlations was discussed in terms of the variation of spatial distribution of the fission-product activities in the individual assemblies. Capability for the non-destructive method to estimate amounts of transuranium nuclides other than Pu was also discussed.