Uncertainty propagation from neutron flux to decay gamma source in R2S methodology

Abstract

A new methodology to propagate the uncertainties from the neutron flux to the decay gamma source in R2S calculations is presented. The calculation of the gamma source uncertainty is an intermediate step in the propagation of the neutron flux uncertainty to the shutdown dose rate calculated using the R2S approach. The estimation of such uncertainty is not carried out in the usual implementation of current R2S tools, in spite of being an important issue of the R2S methodology.The methodology presented propagates the neutron flux uncertainty through intermediate quantities, like the reaction rates and isotope activity, to the gamma source uncertainty. In a first approach, the activation step is performed considering one step pathway.The tool based on this methodology and developed to calculate the gamma source uncertainty is also presented. Besides, it can also obtain maps with the activity of each isotope and its associated uncertainties. This tool has been tested for the simple case of the activation of a slab. The results obtained are in good agreement with the expected values.