Transport core solver validation for the ASTRID conceptual design study with APOLLO3^®

In this study, we are questioning the capability of 3D deterministic transport solvers available at CEA and EPM to accurately predict the void effect of the sodium plenum of the CEV core (GEN IV Sodium Fast Reactor concept selected for the ASTRID project at CEA). Discrete Ordinates, Spherical Harmonics and Simplified Spherical Harmonics transport solvers have been tested against Monte Carlo method on Takeda Benchmark Model 4 and on a new variant with a sodium plenum. Sn solvers offer the best accuracy on multiplication factor, void effect and control rod worth, with values very close to reference Monte Carlo ones. However, even using acceleration techniques, computing time are quite consequent. This difficulty should be solved by the parallelization of the MINARET Sn solver in the APOLLO3^® platform. SPn solvers are very fast, but also quite distant from the reference, especially for the calculation of the void effect where they prove largely inadequate. A good compromise between accuracy and computational time is obtained with the Pu solver VARIANT. The corresponding nodal method is being implemented in APOLLO3^®. (author)