Optimized Control Rod of the Research Reactor BR2

At the present time the BR2 reactor uses Control Rods with cadmium as neutron absorbing part. Due to the burn up of cadmium during the reactor operation, the presently used rods for reactivity control of the BR2 reactor have to be replaced by new ones. Considered are various types CR with full active part of cadmium, hafnium, europium oxide, gadolinium oxide. Options to decrease the burn up in the hot spot, such as use of stainless steel in the lower active part of the Control Rod are discussed. The changing of the characteristics of different types Control Rods and the perturbation effects on the reactor neutronics during the BR2 fuel cycle are investigated. The burn up of the Control Rod absorbing material, total and differential control rods worth, macroscopic and effective microscopic absorption cross sections, fuel and reactivity evolution are evaluated during 30 operating cycles (1000 EFPD). The calculations are performed for the full scale 3-D heterogeneous geometry model of BR2 using MCNP&ORIGEN-S combined method. A criterion for choice of the new control rod types is presented. The main procedures for control of the BR2 reactor are revisited and modified to satisfy the new irradiation conditions.