Using various point wise and multi-group cross sections libraries in morets criticality calculations
Congress title :ND 2007 International Conference on Nuclear Data and Technology
Congress location :Nice
Congress date :22/04/2007
Most modern criticality safety Monte Carlo codes have reached a good level of achievement concerning the implemented simulation algorithms. Discrepancies observed on final results (for example performed by different teams with different codes and data) are mainly due to the nuclear data used. Therefore, knowing and controlling the way of processing nuclear data libraries used by these codes is nowadays crucial. Recent MORET improvements have focused on the development of a prototypic continuous-energy version. Indeed, so far, the cross-sections used by the MORET code (developed by IRSN) are read from external multi-group libraries. It has been then decided to plan new developments in MORET 5 to control the whole criticality calculation process, from the reading of nuclear data to the Monte Carlo simulation itself. The new features related to this new version will allow performing criticality calculations either with a multi-group or a continuous energy treatment. The goal of this paper is to present:
the main topics needed to ensure proper development of a continuous-energy version of MORET (control of the basic nuclear data tools to generate continuous and multi-group energy cross-section libraries from any evaluation (JEF, ENDF/B
), adaptation of the tracking routines, ways to reduce simulation time),
the first reflexions and results concerning the use of various multigroup or pointwise cross sections libraries in MORET : a very fine energy mesh of several thousand groups for the multi-group approach, without needing preliminary calculations performed with a cell code (necessary to take into account self-shielding and homogenization), a universal energy grid (the same for all isotopes and media) for a continuous energy treatment, and cross-sections from other multi-group libraries (from SCALE system for example).