Continuous-energy Monte Carlo calculation analysis of light-water moderation critical experiments with aqueous solution samples of B, Rh, Cs, Nd, Sm, Eu, Gd, and Er

ABSTRACT

In order to validate the neutron absorption cross sections in the JENDL-4.0 nuclear data library, critical analysis was performed using a continuous-energy Monte Carlo calculation code for the light-water moderation UO₂ cores loaded with the aqueous solution samples of eight elements (B, Rh, Cs, Nd, Sm, Eu, Gd, and Er). The concentrations of the elements in the solution samples were changed in the experiments, and the criticality water levels were measured. The calculated k_eff values of the critical cores for the different concentrations of each element were plotted against the reactivity worth of the solution samples calculated based on the differences in the critical water levels. They were fitted by an approximate linear curve to obtain the slope which was regarded as a negative value of a fractional bias of the absorption cross section in the thermal and epi-thermal neutron energy regions. The obtained fractional biases indicated that the absorption cross sections of Sm, Eu, and Gd agreed with the actual values with the uncertainties of about 3%, and those of B, Rh, and Er overestimated them by 6 $\pm$ 3%, 5 $\pm$ 3%, and 6 $\pm$ 4%, respectively.

KEYWORDS:

• Light-water moderation
• UO₂ fuel core
• aqueous solution sample
• boron
• fission product nuclide
• erbium
• critical water level
• continuous-energy Monte Carlo calculation
• MVP3
• JENDL-4.0

Disclosure statement

No potential conflict of interest was reported by the author.