Impact of integral burnable absorbers on SMART reactor behaviour under normal and anomalous operational conditions

Burnable poisons are used to safely prolong reactor core cycle time. They are effective alternatives to regulate power peaking factor and to reduce soluble boron concentration. One of common materials employed for this purpose is Gd2O3 dispersed homogenously in UO2 fuel material. The amount of Gd2O3 content impacts directly on thermophysical properties of integral burnable absorber rods. Therefore, especial care must be taken at the design stage of the reactor core. In this paper, the effects of various Gd2O3 contents, as a burnable poison, on neutronic and thermal hydraulic behaviour of a SMART reactor are investigated. MCNPX 2.6 code is used to perform neutronic simulations of the core. The COBRA-EN with modified MATPRO subroutine is employed for calculating integral burnable absorber rods temperature in normal operation and control rod withdrawal accident. Results show that 12 percent of weight fraction for Gd2O3 lead to the suitable neutronic design which does not break the thermal hydraulic and safety constraints. The performance of the core design is evaluated in steady state and transient conditions in details in the paper.