Reactivity measurements of SiC for accident-tolerant fuel

•We measured nuclear reactivity worths of SiC in Toshiba Nuclear Critical Assembly.•We calculated reactivity worths for measured system with MCNP code.•SiC worth was negative for softer spectrum in consequence of neutron absorption.•SiC worth was positive for harder spectrum in consequence of neutron scattering.•Positive worth was overestimated by calculation in about 10 cents.

Silicon carbide (SiC) is a candidate structural material for application with accident-tolerant fuel for light water reactors, which is expected to decrease heat and hydrogen generation resulting from oxidation reaction with high-temperature steam. Although there are studies on irradiation properties of SiC for fusion reactors and gas-cooled reactors, there are no published reports on critical experiments to validate the nuclear reactivity of SiC. We performed SiC nuclear reactivity measurements. Measured reactivity worths of SiC were analyzed by a continuous-energy Monte Carlo code MCNP4c3. We obtained the neutron spectrum-dependent reactivity worths of SiC samples, which imply that the neutron scattering with SiC plays an important role concerning the reactivity worths as well as neutron absorption with SiC. Comparison of analyses with measurements reveals the possibility of room for improvement in SiC cross-sections mainly related to neutron scattering, whereas thermal neutron absorption cross-sections of SiC can well describe the experimental results.