High-Performance Computing for Nuclear Reactor Design and Safety Applications

Large-scale computations play an important role in many engineering and scientific applications. In the nuclear field, in particular, the crucial need for accurate simulations and reliable reference data for validation purposes makes high-fidelity simulations an extremely important tool. Due to the too-large computational resources required, these simulations must be performed on dedicated computational facilities. This paper focuses on the description of the high-performance computing facility at the Świerk Computing Centre (CIŚ) in Poland. More specifically, the hardware configuration, software used for on-demand deployment of dedicated subclusters, and queuing systems are described. The computational capabilities at the CIŚ are assessed by performing scalability tests with the massive parallel code NEK5000. The tests assess the influence of the CPU architecture, cooling infrastructure, and interconnection performance on the solver running times. Subsequently, selected applications are presented. These applications concern the direct numerical simulations of mixed convection and fluid flow in a rod bundle. The mean velocity and temperature, the root mean square of the velocity components, and the novel results related to the budgets of turbulent kinetic energy as well the budgets of the wall-normal and streamwise turbulent heat flux are reported for different Prandtl numbers for the mixed convection case. For the rod bundle case an instantaneous temperature for the isothermal and isoflux boundary conditions is reported. Moreover, the frequency of the velocity pulsation has been computed.