The paper describes the methodology for the calculation of neutron fluence and energy release in WWER-1000 reactor cavity and baffle using the Monte Carlo MCNPX code. It formulates an approach to the simulation of a 3-D neutron source and conditions for the transport of neutrons and photons in the core. The research presents preliminary results of neutron fluence and energy release calculation in WWER-1000 reactor cavity and baffle.

The paper considers the development stages and results of a set of organizational, scientific and technical decisions on the implementation of a new nuclear fuel from an alternative supplier, Westinghouse Company, to Ukrainian NPPs with VVER-1000 type reactors. Testing of six trial fuel assemblies of the Westinghouse Company (FA-W) during SUNPP Unit 3 Cycles 17 – 20 (2005 – 2010) and 42 FA-W of the reload batch during Cycles 21-24 (2011-2014) confirmed compliance with design parameters, integrity and reliability of a new fuel during a four-year operation cycle.