Reactivity Effect of Borated Stainless Steel Plate in Single and Coupled Cores Composed of Low-Enriched UO2 Rods

For the criticality safety designs of the storage pools which store large number of spent fuels, neutron poison materials are useful for increasing capacity of the storage pool by minimizing the spacing between the fuel assemblies. Since few experimental data exist for examining the validation of calculation methods which evaluate the nuclear criticality safety of fuel storage using the borated SUS (B-SUS) plates, critical experiments with B-SUS plates in the water region of single and coupled cores were performed at the Tank-type Critical Assembly (TCA). The systematic data on the reactivity effect of B-SUS plate as a function of the thickness, the boron content and the position of B-SUS plates in the water region were obtained using the critical water level method. The interacting effect between the two cores was also measured to clarify the nuclear characteristics of the coupled two core system which is the simplest system among multiple unit system. Criticality calculations with the combination of a Monte Carlo code, KENO-IV, and the MGCL-137 neutron cross section library in JACS were carried out, and these calculations reproduced the reactivity effect of B-SUS plate within ±0.6%ΔK/K.