LSM Webinar: Benchmark Exercise on Large Sodium Cooled Fast Reactor Core Neutronics and Transient Behaviour

by Dr Alexander Ponomarev (PSI)

Thursday 28 Jan 2021, 14:00 → 15:00 Europe/Zurich

https://ethz.zoom.us/j/8837492509 (Join Zoom meeting)

Abstract:

A new benchmark exercise has been performed within the ongoing EU Horizon-2020 ESFR-SMART project with the goal of validation of neutronic and thermal hydraulic codes. This presentation will summarize the scope of activities and highlight main achievements.

New calculation benchmark proposed by PSI uses the startup core configuration of the large Sodium cooled Fast Reactor Superphénix. This French fast neutron reactor operated in eighties-nineties stays the largest ever constructed liquid metal cooled reactor in the history of nuclear energy production. During its operation time, countless experiments and measurements were conducted and considerable amount of precious data from the lifetime of large fast reactor were collected. This data should not be forgotten but employed in order to validate the codes calculating the fast reactors.

The benchmark comprises two phases: static and transient. In the first phase, the core specification for neutronic analysis has been developed using available open literature sources. It allowed to reproduce criticality level, flux distribution and main core safety characteristics, experimentally observed. The preparation of the benchmark specification will be discussed and the results obtained by seven different participants will be presented in comparison with the reference benchmark solution of Serpent 2 prepared by PSI.

Evaluated neutronic characteristics obtained in the first phase, such as power spatial distribution, worth of control rods, reactivity feedback coefficients, were used further in the second, transient phase related to modelling of core transient behaviour. A simplified primary circuit model for the TRACE code has been elaborated, which consists of few channels representing fuel subassemblies connected by inlet and outlet plena with appropriate boundary conditions, as well as number of heat structures allowing to account for reactivity feedbacks related to primary circuit structures thermal expansion, such as vessel wall, diagrid plate, core support structure (strongback). For six selected operational transients initiated at different power levels from zero to ~50% nominal these effects cannot be neglected. First the model was tested using available in open literature experimental data on core reactivity balance and corresponding reactivity coefficients at the core conditions from cold zero power to nominal power operation. Next the benchmark simulations were performed for the selected transients with three system codes TRACE (PSI), ATHLET (HZDR) and SIM-SFR (KIT). Choice of the specification for simulations of selected transients will be highlighted followed by presenting selected transient results.