Method of burnup calculation of spent fuel assemblies of the IVV-2M research reactor using the MCU-PTR software tool

Research reactors (RRs) are widely used for research in fundamental physics, materials science, and for radioisotope production. One of the problems in the field of mathematical modeling of research reactors is the verification of computational codes used for the calculation of neutron-physical parameters. To pass the verification procedure, it is necessary to justify the methods of mathematical modeling and the accuracy of the RR geometric model. Currently, precision programs allow creating a RR geometric model of any degree of detail. However, the degree of this detail has not been formulated. The paper considers the justification of the parameters of spatio-temporal discretization of IVV-2M-type fuel assemblies when calculating the burnup distribution. Determining the frequency of dividing the fuel assembly model into layers by the height of its active part significantly affects such parameters as the effective neutron multiplication factor (Keff), energy release at the maximum stress point. Moreover, the degree of detail and the set of calculation statistics affect the calculation duration, which can be reduced by applying a certain approach to modeling. It should also be noted that the issue of the need for a fuel pin (or more detailed, in the horizontal plane) degree of burnup calculation was not considered due to the lack of control over the orientation of the IVV-2M fuel assemblies in the horizontal plane during the operation of the IVV-2M research reactor.