Tungsten Carbide compact primary shielding for Small Medium Reactor

Abstract

In order to improve the Small Medium Reactor’s radiation protection system, a new design for primary radiation shielding based on Tungsten Carbide and Lead is presented. The application of Tungsten Carbide is considered, so that a compromise between low weight and high absorption is found, to achieve allowed radiation dose rate after reactor shutdown. Its high density and the presence of Carbon nuclei, makes this material an interesting shielding against photons and fast neutrons as well, leading to an original design. Tungsten Carbide is arranged in absorbing rods of 17.05 mm inner diameter with a pitch of 20 mm, voids between absorbing rods are filled with Lead in order to increase the self-shielding of the structure. Design process is illustrated with an application example for a hypothetical 200 MW Small Medium Reactor. Radiation source was quantified with ORIGEN code and radiation transport throughout shielding was calculated with MCNP5 code. The result was a shielding of 31 cm thickness and 150 MT of weight. The maximum dose rate was 3 µSv/h, after 83 min since reactor shutdown.