Monte Carlo analysis of direct measurements of the thermal eta (.025 eV) for 233U and 235U (LWBR development program)

Significant inconsistencies have been observed between measured values of eta and of ν, which are related by eta = ν/(1+α). In support of the LWBR program, manganese bath measurements of eta of 233U and 235U employing monoenergetic 0.025 eV neutrons were analyzed using Monte Carlo methods and ENDF-4 cross sections. The calculated (eta*/eta2200) ratios are essentially independent of the values assumed for eta2200. The standard deviation on our calculated values of eta includes Monte Carlo, cross section, and experimental uncertainties. The Monte Carlo analysis was confirmed by calculating measured quantities used by the experimentalists in their reduction of eta* to eta. (4 figures, 12 tables) (U.S.)