Water-Moderated Cores with Boron Steel Septa at Elevated Temperatures

A series of fifteen experiments were carried out on an 8 × 30 × 32 in. core in the Pressurized Critical Assembly at KAPL. In twelve of these experiments, 0.030-in. boron stainless steel septa bisected the 8-in. dimension. These septa contained various weight per cent B¹⁰. In the remaining three experiments, there were no boron-stainless steel septa in the core. The eigenvalues and neutron density distributions were compared with values which were calculated using Deutsch cross sections and “Thin Region Theory.” The eigenvalues which were calculated were within one per cent of the experimental values, with a spread of approximately one per cent. For all the cores, the calculated eigenvalues were lower than the experimental values. Analyses of the neutron density distributions showed the calculated results in fairly good agreement with the experimental results. In all cases, this agreement was as good for the cores which contained the boron septa as for the ones which did not. It therefore appears that the boron has been well represented by “Thin Region Theory,” and that the main discrepancies between calculated and experimental values are due to the inadequacies of adapting the Deutsch scheme to these cores.