Neutronic analysis of maximum cores with the ERANOS deterministic code (and JEFF3.1 nuclear data library)

This work was carried out in the framework of the EU FP7 project MAXSIMA “Methodology, Analysis and eXperiments for the Safety In MYRRHA Assessment”. The MAXSIMA WP2 deals with the safety analyses to support the licensing of MYRRHA (a 100 MW LBE cooled irradiation facility planned to be built at the SCK-CEN research centre in Mol, Belgium) and Task 2.1 is devoted to the neutronic and shielding analyses in support of safety studies. The neutronic parameters (for TH safety studies) have to be evaluated through the analysis of envelope cases - minimum and maximum cores in both critical and sub-critical operational modes - yielding the possible working range of the MYRRHA core. This document summarizes the presentation done by the author in the SEARCH-MAXSIMA meeting on April 28-30th, 2014, at the University of Gent (B). He showed the results of the neutronic analyses of the MYRRHA maximum cores, having equilibrium fuel compositions and some In-Pile Sections for sample irradiation, with the ERANOS deterministic code and JEFF3.1 nuclear data library. The studies, carried out in critical and sub-critical operational modes, were performed in three different core conditions: at 20 °C (to assess safety limits), at 200 °C (the zero power level) and in nominal conditions. The analyses include the evaluation of the reactivity feedbacks / coefficients due to temperature effects (in both operational modes), as well as the core reactivity variation in case of accidental situations in sub-critical mode. In conclusion, the most significant differences between the neutronic results of the minimum and maximum cores were shown. Such data set provides an envelope for safety studies, that is a variation range of the main neutronic core features in both DBC and DEC cases.