A nuclear reactor’s design and safety assessment relies on a calculation platform consisting of a series of calculations performed using different simulation tools, each dedicated to modeling a specific phenomenon. The European Union H2020 CAMIVVER Work Package 4 aims to establish lattice neutronics calculation methodologies for VVER and pressurized water reactor fuel assemblies employing the new-generation deterministic multipurpose neutron transport code APOLLO3®, developed by the CEA (Commissariat à l’Énergie Atomique et aux Énergies Alternatives) with the support of EDF (Electricité de France) and Framatome.

The present work aims to present NEMESI, an industrial prototype of a flexible lattice calculation tool developed as part of the CAMIVVER project, showing the applicability of APOLLO3 for industrial research and development and proposing dedicated VVER calculation schemes. Given the intense focus on the industrial issues of the entire CAMIVVER project, the elements constituting the rationale behind the development of such a computational platform are flexible modeling and analysis options, compliance with a series of specified requirements, implementation of innovative algorithms with improved precision, and a modern software and architectural base.