Development of a model for the approximation of the neutron and photon flux in a BWR spent fuel assembly

摘要

This paper proposes a simplified model built with Matlab to compute an approximation of the neutron and photon flux in a BWR spent fuel assembly in a pond. Starting from a reduced number of Monte Carlo simulations, a set of transmission probabilities has been calculated. These values allow the estimation of the particle flux inside a fuel assembly placed in a generic storage rack. This calculation is possible provided the transmission probability has been calculated for the desired value of burnup and cooling time of the assemblies in the rack. The validity of the model has been tested first with a uniform pattern of the storage rack and finally with a generic configuration. Reference values from the equivalent Monte Carlo simulations show very good agreement and the relative error between the two measures is always within few percents. The main advantage of this simplified model is the great reduction of computational time required to perform the estimation and the fact that the basic idea behind the model can be applied to any fuel geometry and type of storage pond.