Experimental analysis of small sample reactivity measured in the SEG experiment by a deterministic reactor physics code system CBZ

Abstract

Experimental analysis of the sample reactivity measured in the SEG experiment is carried out with the deterministic reactor physics code system CBZ with the recent evaluated nuclear data files, JENDL-4.0, ENDF/B-VIII.0 and JEFF-3.3.Since the systems to be analysed are fast-thermal coupled ones, 211-energy group neutron reaction cross section libraries applicable to both the fast and thermal neutron systems are generated and utilized. In the multi-group library generation, the recentlydeveloped FRENDY and FRENDY/MG codes are used. Forward and adjoint neutron fluxes at the sample position are calculated by solving the neutron transport equation, and the sample reactivity is obtained by the first-order perturbation calculations. In order to simplify the systems calculated, two-dimensional cylinder model is prepared based on the previous work.Whereas the simplified model is employed, generally the reactivity of many different samples is well predicted by the calculations in comparison with the experimental uncertainties. On some of the samples, large discrepancies of the C/E values from unity are observed, and also relatively large differences in the C/E values among different nuclear data files are observed. These information are still useful for future development of the 1