Review of the neutron physics results of radial profiling using the example of a VVER-1200 reactor unit cell

It is necessary to create a reserve of the maximum service life of fuel and structural materials to increase the service life of fuel rods in a nuclear reactor. This paper considers various methods of reducing the radial unevenness of fuel element burnup by redistributing fissionable nuclei (profiling) using the example of the unit cell of the VVER-1200 reactor in the infinite breeding medium. The fuel pellet is divided into a different number of concentric layers to be profiled, the enrichment of the layers varis while maintaining the total number of fissile nuclei in the fuel pellet at the beginning of the fuel campaign. In the Serpent 2 PC, neutron physics calculations of the corresponding models are performed, after that the characteristics obtained for them are compared: the infinite multiplication factor, the average rate of reactivity loss, the proportion of delayed neutrons at the beginning of the campaign, radial burnup profile and energy release distributions (at different time points), and changes in reactivity effects after profiling. The result of this work is a selected optimal method to reduce burnup on the fuel pellet periphery by increasing enrichment in the central part of the fuel pellet and, as a result, a more uniform burnup profile in the whole of the tablet. The research shows that there is no change in the neutron-physical characteristics as a result of the transformations carried out. A possible problem when using this profiling method may be an increase in the peripheral layer temperature as a result of a significant increase in energy release in it during the fuel campaign.