Evaluation of the Serpent-Aleph code system to capture the photo-neutron physics of the BR2 reactor

The purpose of this thesis is therefore to evaluate the suitability of the ‘new’ coupled SERPENT-ALEPH code system for calculations involving photonuclear physics in the BR2 reactor. SERPENT in this case would be used for the Monte Carlo particle-transport, while ALEPH would account for irradiation histories, fuel depletion, and evolving isotopic compositions. Their combined application could provide a framework for investigating prompt and delayed photon sources, their contributions to secondary-neutron production, and their potential influence on relevant reactor-physics quantities, such as the effective delayed neutron fraction.

The thesis would first involve the development and verification of a coupled neutron-photon transport model for a representative single channel of BR2 using SERPENT, based on existing and validated BR2 neutronics models. Particular attention would be given to the use of channel and position specific neutron and photon energy spectra to accurately characterize the local irradiation environment. Next the spatial distribution of the ALEPH calculated decay sources within the geometry must be defined.

Next step would be to carry out model comparisons between neutron-only, coupled neutron-photon calculations to isolate and quantify the effects introduced by each additional physical process. This would allow the contribution of photonuclear reactions to the local neutron field, reaction rates, and selected reactor-physics quantities to be assessed. Finally, selected SERPENT-ALEPH results would be compared with available ALEPH-MCNP6 calculations, where possible, to evaluate the consistency of the new computational framework and identify potential differences arising from the transport methods, nuclear data, or the treatment of the underlying reactor physics.