Evaluation of the PDS-XADS reactivity level at Beginning of Cycle by means of deterministic methods

This work is performed within the framework of the ANSALDO-ENEA collaboration for the PDS-XADS project. A detailed neutronic analysis of the reactor LBE XADS in the absence of the external source has been carried out by means of Eranos modular system ver. 1.2. Starting from a detailed geometrical model of the LBE XADS, the reactivity of the system at different temperatures has been calculated by Eranos deterministic code. The results obtained ara very close to the Monte Carlo (MCNP) values, in spite of the different nuclear data libraries adopted. One of the purposes of this work is to simplify the reactor geometry model in order to perform the fuel cycle analysis in the near future. Of course the simplified geometrical model must give reactivity levels as near as possible to those obtained with the more detailed description. However, the peculiarity of this work is the very detailed geometric modelling of the system that made it possible to compare accurately the Keff results obtained by deterministic and Monte Carlo methods at different temperatures.