Comparative analysis of BWR core transient benchmarks - 227

This paper describes the research performed jointly by the Pennsylvania State University Nuclear Engineering Department and Toden Software Incorporation to evaluate the effect of employed neutronics model on coupled three-dimensional (3D) transient predictions. The TRACBF1/ NEM and TRAC-BF1/ENTReE codes use the same thermal hydraulics code applied to different neutronics codes. These codes were used to model the OECD/NEA BWR core transient benchmarks. A brief description of these benchmarks is given in this paper. Modeling schemes are described in detail, followed by comparisons of steady state and transient results obtained from both codes. Some results from other coupled codes are also presented for a more complete comparison. The performed comparative analysis suggests that the neutronics effects (in terms of nodalization schemes, cross-section modeling algorithm and used method in the framework of transverse integrated nodal procedure) are small in both steady-state and transient predictions. Once the optimal spatial overlay (mapping) scheme is chosen the major contributor in the observed deviations in the different coupled code predictions seems to follow from different thermal-hydraulics models and their degree of sophistication. (author)