Benchmark evaluation of zero-power critical parameters for the Temelin VVER nuclear reactor using SERPENT & NESTLE and MCNP

•Benchmark study of a VVER 1000 core simulation of hot zero power (HZP) tests.•The Serpent-NESTLE combination is capable of providing high quality simulations.•The Serpent-NESTLE combination and MCNP, both, provided reasonable results. This article presents a benchmark study of a VVER 1000 core simulation of hot zero power (HZP) tests. Measured experimental data from the Temelin Unit 2 nuclear power plant’s operation test during its first reactor startup were compared using MCNP as well as the combination of Serpent + NESTLE lattice-to-diffusion nodal simulation. Results from full-core 3D models included multiplication factor and moderator temperature coefficients (MTC) that were compared to experimental data, which revealed a very good agreement with criticality states during HZP tests, and a reasonable agreement for MTC. Therefore, it is concluded that the Serpent-NESTLE combination and MCNP, both, provided reasonable results for this benchmark. The Serpent-NESTLE code combination was used for the first time in this study and has shown to be capable of providing high quality simulations in an efficient fashion. To encourage future benchmarks by other researchers, this article makes a special effort to document the core design information and details that would facilitate such efforts.