Specially developed LR-0 reactor graphite environment for gen IV reactor support and cross-section measurement

Abstract

This paper is focused on the development of the experimental environment connected to reactor graphite. Regarding its very good neutronic and mechanical properties, graphite will be very important in some new reactor designs, such as high-temperature or molten salt SMR reactors. These new reactor concepts require a new experimental environment as support for further research. In the laboratories of the Research Centre Řež and at the LR-0 reactor, the new experimentally validated graphite environment was created. This large graphite insertion is the largest graphite mono-block, which is possible to assemble at the LR-0 reactor. Sets of experiments for measuring reaction rates of different activation detectors for neutron field mapping were performed. This approach was used for thermal and epithermal region descriptions. For the fast neutron spectrum evaluation, the stilbene scintillation detector was used. All parameters, such as criticality height of moderator level, neutron spectrum, and other parameters for all experiments, were performed using Monte Carlo neutronic codes Serpent and MCNP. The obtained results were finally compared to the measurement of neutron leakage spectra from the graphite cube and graphite cylinder. These specially developed graphite-shaped neutron fields, reactor insertions, and external cube and cylinder with Cf neutron source can be used in the future for validation of not only materials used in SMR reactors but for arbitrary cross-section verification.