Optimization and Analysis of Low-Leakage Core Management for Pressurized Water Reactors

Low-leakage extended burnup fuel management is a promising pressurized water reactor (PWR) improvement that yields better neutron economy than the traditional out-in fuel management scheme with resulting economic savings and a likely reduction in vessel fast neutron fluence. The Commonwealth Edison Zion-1 reactor was selected as representative of current operating PWRs and analyzed. A major objective was to develop and analyze optimum transition loading arrangements leading from present out-in management to the desired low-leakage scheme. A so-called “wet” burnable poison was used in the calcula-tional model, which was based on various Electric Power Research Institute/Advanced Recycle Methodology Program modules. An accelerated direct search scheme was developed to optimize the loading pattern utilizing the initial boron concentration as the objective function, which would correspond to a maximum cycle length for a given number of loaded fresh assemblies. The equilibrium cycle, with 32 of 48 fresh assemblies loaded in the core interior, resulted in a 6.4% saving in fuel cycle costs compared with a three-batch out-in strategy, and a 3.8% saving compared with a four-batch out-in strategy. Therefore, the low-leakage option is a promising improvement and detailed design is justified.