Results and experiences from the analysis of the OECD PWR MSLB and BWR TT benchmarks by the coupled code system ATHLET-QUABOX/CUBBOX

The GRS results of the two QECD/NRC benchmarks for coupled codes - PWR Main Steam Line Break (MSLB) and BWR Turbine Trip (TT) are presented in the paper. Both benchmarks have been calculated for all exercises by the coupled code system ATHLET - QUABOX/CUBBOX developed by GRS. The OECD PWR Main Steam Line Break Benchmark has been defined to validate the coupled code systems with 3D neutronics by comparing solutions of different codes (code-to-code comparison). The BWR TT Benchmark is based on measurements. Both benchmarks proved to be a valuable source for coupled code validation. The sensitivity of results on modelling features is also discussed in the paper. In addition, the effect of different mapping schemes between fuel assemblies of the core loading and the thermal-fluid dynamics on the accuracy of 3D neutronics solutions is shown. The results for the MSLB transient are also evaluated to compare 3D neutronics and point-kinetics solutions in view of integral and local parameters. Thus, the experiences with the coupled code system ATHLET - QUABOX/CUBBOX during the MSLB and TT benchmarks activities are summarised. (author)