Sensitivity and uncertainty analyses of fission product nuclide inventories for passive gamma spectroscopy

The passive gamma spectroscopy (PGS) is a useful technique to extract information on spent nuclear fuels without any destructive actions. This method requires a correlation between number densities (NDs) of target nuclides, and it is generally estimated by numerical simulation. Therefore, the prediction accuracy of these nuclide generations is one of the key issues in PGS. Nuclear data used in nuclear fuel depletion calculations is one of the dominant uncertainty sources, so we quantify nuclear data-induced uncertainties of NDs of six fission product nuclides, which are important in PGS: Ce-144, Cs-134, −137, Ru-106, Sb-125, and Eu-154. Generation mechanisms of these nuclides are quantitatively investigated through sensitivities of these NDs to nuclear data. With the sensitivities and covariance data of nuclear data, uncertainties of NDs of these nuclides are quantified. The uncertainties of Ce-144, Cs-137, and Ru-106 are less than 2%, and that of Sb-125 is around 6%. In these uncertainties, fission yield uncertainties are dominant. On the Cs-134 and Eu-154 generations, total uncertainties are around 5% and uncertainties of (n,γ) cross-sections are dominant.