Reevaluation of fuel enthalpy in NSRR test for high burnup fuels

Udagawa, Yutaka  ; Sugiyama, Tomoyuki ; Amaya, Masaki  

Previously, the fuel enthalpy in high burnup fuel tests at the NSRR had been evaluated by the procedure based on the short-life fission product measurement. But a part of the results showed significant scattering even within the similar tests with similar fuels, which should have showed similar fuel enthalpies. Hence, an alternative procedure, which is based on the evaluation of total amount of fissile materials evaluated by mass analysis, was developed. This procedure does not require quickness and is repeatable, so it is applicable even many years later if the fuel sample is available. The recent procedure was thus applied to the tests before 2003, whose burnups are below 60 GWd/tU. It was shown that the fuel enthalpy had been significantly underestimated in the tests with high burnup PWR fuels: the test series HBO and TK.