Development and Validation of a New APOLLO2-Based Calculation Scheme Dedicated to ISABELLE1 Ex-Core Rod Irradiations in the OSIRIS MTR Reactor

摘要

This paper describes a new neutron calculation scheme, based on the APOLLO2 neutron transport code with the linear surface Method of Characteristics (LS-MOC). This scheme was dedicated to high-flux fuel rod irradiations carried out with the ISABELLE1 movable loop located in the core periphery of the OSIRIS material testing reactor (CEA, Saclay Center), until the reactor shutdown in December 2015. This loop was used to study the behavior under irradiation of fuel rods during power transients. The aim of this new calculation scheme was to predict the loop-core distance to reach a given power of the irradiated rod in ISABELLE1, taking into account the relevant irradiation parameters, in particular the core-loading map, the control rod effects and the fuel depletion in the core assemblies. Validation has been performed by comparisons to reference calculations using the TRIPOLI-4® Monte-Carlo code and measured quantities. Validation over reference calculations shows discrepancies on the rod power around 5%. The experimental validation shows discrepancies on the loop-core distance less than 1 cm (about 3% of the maximum distance).