Study on the Thermophysical Properties of 80% ¹⁰B Enrichment of B₄C

In this paper, a specific type of Boron Carbide (B₄C) with a high enrichment of 80 ± 0.3 at% ¹⁰B was prepared as an absorbing material for control rods in nuclear reactors. The enrichment of ¹⁰B was achieved using a chemical exchange method, followed by obtaining boron carbide powder through a carbothermal reduction method. Finally, B₄C 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 B₄C compared to natural B₄C 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 B₄C 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 B₄C, 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.