Fuel performance code BERKUT-U to simulate the in-pile behavior of a single oxide or nitride fuel rod for fast reactors

This paper describes the fuel performance code BERKUT-U, which the Nuclear Safety Institute of the Russian Academy of Sciences (IBRAE RAN) designed as part of the "Codes of The New Generation" subproject of the Proryv Project. The code aims to model oxide or nitride single fuel rod behavior with a gas or liquid metal sublayer under normal and accident conditions of a liquid metal-cooled fast reactor operation. The BERKUT-U code's models, incorporating the MFPR/R code, are grounded in the contemporary understanding of mechanisms governing the fundamental processes in fuel rods under irradiation, which substantially enhances the code's predictive ability in comparison with the engineering analogs. Simulations of the nitride and oxide fuel rod behavior in BN-600 and BOR-60 fast reactors have demonstrated good agreement with the post-irradiation examination data. Further validation is foreseen as the corresponding data are available.