Benchmark analysis of the pebble bed modular reactor with Flownex and COMSOL

The analysis of many Small Modular Reactor designs utilizes a variety of codes to predict both steady-state and transient behaviour. Assessment of code-to-code predictions can be used to benchmark and examine the important differences in analysis methodologies. This paper presents a study conducted to assess the capabilities implemented in Flownex and COMSOL for pebble-bed reactor analysis. For this purpose, Flownex and COMSOL calculations of the standalone steady-state thermalhydraulics exercise and one of the transient scenarios defined in the OECD Nuclear Energy Agency PBMR-400 benchmark were performed. Overall, the comparison of the results shows good agreement between Flownex and COMSOL, and with those submitted by the benchmark participants. Given the large number of differences in methodological approaches (FEM vs. 1D system code) and empiricism, the level of agreement was deemed very good. (author)