Study on the Thermophysical Properties of 80% B Enrichment of BC.

In this paper, a specific type of Boron Carbide (BC) with a high enrichment of 80 ± 0.3 at% B was prepared as an absorbing material for control rods in nuclear reactors. The enrichment of B was achieved using a chemical exchange method, followed by obtaining boron carbide powder through a carbothermal reduction method. Finally, BC with a high enrichment of 68.3~74.2% theoretical density was obtained using a hot-pressed sintering process. This study focused on investigating the basic out-of-pile thermophysical properties of the high enrichment BC compared to natural BC reference pellets under non-irradiated conditions. These properties included the thermal expansion coefficient, thermal conductivity, emissivity, elastic limit, elastic modulus, and Poisson's ratio. The research results indicate that the enriched BC pellet exhibits good thermal stability and meets the technical requirements for mechanical capability. It was observed that porosity plays a significant role in determining the out-of-pile mechanical capability of BC, with higher porosity samples having a lower thermal conductivity, elastic-plastic limit, and elastic modulus. In short, all the technical indexes studied meet the requirements of nuclear-grade Boron Carbide pellets for Pressurized Water Reactors.