Validation of the Serpent 2-HEXTRAN-SMABRE code sequence in a VVER-1000 coolant transient

This paper presents a VVER-1000 coolant transient benchmark calculated using Serpent 2 generated group constants in the reactor dynamics code HEXTRAN coupled with the system code SMABRE. Two different sets of group constants applying different leakage correction methods are generated. The purpose of the paper is to validate the Serpent 2-HEXTRAN–SMABRE code sequence in plant transient calculations for a commercial VVER-1000 reactor. Calculated radial power distributions, relative fission power, mass flow rate and coolant heat-up are compared to experimental data. These factors, axial power distributions, radial and axial peaking factors and axial offset are also compared to results calculated using HELIOS generated group constants provided in the benchmark. Results calculated with Serpent generated group constants agree with the experimental data mostly within measurement uncertainty. Deviations larger than measurement uncertainty are explained by the insufficiency of available data needed for the HEXTRAN–SMABRE simulation or the albedo calculations.