Evaluation of PWR pressure vessel fast neutron fluence benchmarks from NUREG/CR-6115 with ares transport code

Abstract

An ac cu rate eval u a tion of PWR pres sure ves sel fast neu tron fluence is es sen tial to en sure pressure ves sel in teg rity over the de sign life time. The dis crete or di nates method is one of the main meth ods to treat such prob lems. In this pa per, eval u a tions have been per formed for three PWR benchmarks de scribed in NUREG/CR-6115 us ing ARES trans port code. The cal cu lated results were com pared to the ref er ence val ues and a sat is fac tory agree ment was ob tained. In ad dition, the ef fects of S N nu meric and source dis tri bu tion mod el ing for pres sure ves sel fast neu tron fluence cal cu la tion are in ves ti gated. Based on the fine enough grids adopted, the dif fer ent spatial and an gu lar discretization in tro duces der i va tions less than 3 %, and fix-up for neg a tive scatter ing source causes no no tice able ef fects when cal cu lat ing pres sure ves sel fast neu tron fluence. How ever, the dis crep ancy of as sem bly-wise and pin-wise source mod el ing for pe riph eral as semblies reaches ~20 %, which in di cates that pin-wise mod el ing for pe riph eral as sem blies is es sential. These re sults pro vide guide lines for pres sure ves sel fast neu tron fluence cal cu la tion and dem on strate that the ARES trans port code is ca pa ble of per form ing neu tron trans port cal cu lations for eval u at ing PWR pres sure ves sel fast neu tron fluence.