DEVELOPMENT OF AN ADVANCED CORE ANALYSIS SYSTEM FOR BOILING WATER-REACTOR DESIGNS

A core analysis system has been developed for the recent advanced desi gns of boiling water reactors. This system consists of a fuel assembly analysis code VMONT and a three-dimensional core simulator COSNEX. To cope with heterogeneous structures found in the recent high-performan ce fuel, VMONT employs a Monte Carlo neutron transport calculation met hod. COSNEX is based on a three-group nodal expansion method to treat spectral interactions among fuel assemblies. Both codes are vectorized to meet timing requirements as design tools. The analysis system is v erified by the tracking of recent plant operations. Although the analy zed cores are highly heterogeneous in the multienrichment configuratio n, the system gives sufficient accuracy both in critical eigenvalues a nd thermal power distributions.