Study on the rationalization of fuel design by adopting the probabilistic fuel design method

not registered; not registered

The design margin for uncertainties is evaluated by accumulating the uncertainties conservatively in the present LMFBR fuel design. However rationalization, such as reduction of design margin for uncertainties, is required to increase the linear heat rate and burn-up in the future. Probabilistic design method is considered to be effective to cut the excess design margin, because the design margin can be evaluated quantitatively by this method. In order to apply the probabilistic design method instead of present deterministic method, it is considered that the design criteria, design method and database should be provided. In the previous studies, the LWR statistic design method was investigated and BORNFREE-DIRAD and BORNFREE-STRESS were developed to apply the probabilistic fuel design method to evaluation of CDF, the cladding stress and the maximum fuel temperature. In this study, the database of material properties was investigated. The FP gas release ratio and FCCI (Fuel cladding chemical Interaction) related to evaluation of cladding stress were investigated based on irradiated data in JOYO and other foreign LMFBR. New correlation of FP gas release ratio and FCCI were proposed and their uncertainties were evaluated. These correlation were made as the function of various parameters such as linear heat rate and burn-up and the sensitivity of these parameter to the fuel performance were able to be evaluated by using these correlation. It was evaluated that the nominal FP gas release ratio by new correlation was smaller than that of old one, and uncertainty of new correlation was larger than that of old one. The 2 -base values of cladding stress and CDF decreased comparing to these values evaluated by old correlation. It was shown that using new correlation could increase the burn-up. The necessity database for probabilistic method was clarified by above results.