UNCERTAINTY ANALYSIS ON REACTIVITY AND DISCHARGED INVENTORY DUE TO ~(235,238)U~(239,240,241) Pu,AND FISSION PRODUCTS: APPLICATION TO A PRESSURIZED WATER REACTOR FUEL ASSEMBLY

摘要

Uncertainty analysis on reactivity and discharged inventory for a typical pressurized water reactor fuel element as a result of uncertainties in ~(235,238)U~(239,240,241) Pu and fission products nuclear data was performed. A typical Westinghouse three-loop fuel assembly fueled with UO_2 fuel with 4.8% enrichment was selected. The Total Monte Carlo method was applied using the deterministic transport code DRAGON. This code allows the generation of the few-groups nuclear data libraries by directly using data contained in the nuclear data evaluation files. The nuclear data used in this study are from the JEFF3.1 evaluation, with the exception of the nuclear data files for U, Pu, and fission products isotopes (randomized for the generation of the various DRAGON libraries). These are taken from the TALYS evaluated nuclear data library TENDL-2012. Results show that the calculated total uncertainty in k_(eff) (as a result of uncertainties in nuclear data of the considered isotopes) is virtually independent of fuel burnup, and amounts to 700 pcm. The uncertainties in the inventory of the discharged fuel are dependent on the element considered and lie in the range 1% to 15% for most fission products, and are ＜5% for the most important actinides. The total uncertainty on the reactor parameters was also split into different components (different nuclear reaction channels), and the main sources of uncertainties were identified.