Comparison of Results of SAS-SFR Calculations of the CP-ESFR Working Horse and Optimized Core Designs during the Initial Phase of an ULOF Accident

Simulations using the code SAS-SFR were performed to assess the behaviour of two core designs investigated within the European Collaborative Project CP-ESFR. The results for an unprotected loss of flow (ULOF) accident in the initiation phase are presented and analysed for the Working Horse and Optimized Oxide core designs under Beginning-Of-Life (BOL) conditions. The core geometry has to be represented according to simulation capabilities of the SAS-SFR code. The values for the spatial distributions of material worth (sodium, fuel, and steel) and Doppler coefficient were calculated with the modular code system KANEXT using the JEFF 3.1.1 cross section data library. The cores are compared regarding the design optimization related to the consequences of severe accidents. For the optimized core design, the grace time rises considerably and the power excursion is milder. It is a step in the right direction, but not yet sufficient to prevent core destruction. (author)