Hydraulic analysis of the start-up monitoring module (STUMM) for IFMIF-DONES

Abstract

The International Fusion Materials Irradiation Facility – Demo Oriented Neutron Source (IFMIF-DONES) will allow accelerated material testing in fusion-like conditions, up to the doses above the expected lifetime. To successfully irradiate the samples in the High Flux Test Module (HFTM) an extensive start-up phase is needed to confirm the irradiation parameters as well as the conditions inside HFTM. STUMM (Start-Up Monitoring Module) is designed exactly for that purpose and will be operated during the commissioning phase of IFMIF-DONES. The outer part of STUMM resembles HFTM, but inside is equipped with measuring systems: active detectors and Rabbit Systems tightly arranged in the Container. The flow of helium gas used for cooling was analyzed in Ansys Fluent. A pressure drop of 2.9 kPa and 3.4 kPa was found for the two possible flow directions. 8 turbulence models were tested: Spalart-Allmaras, Standard k-ε, RNG k-ε, Realizable k-ε, Standard k-ω, Baseline k-ω, SST k-ω and the Reynolds Stress Model. Out of them, only the Standard k-ε mode did not converge and all the other models gave a correct result. The solution time was analyzed for both the Single Precision and Dual Precision solvers. The Single Precision solver was 3.6-5.5 faster. Analysis of the solution residuals, outlet velocity, and pressure drop showed that both solvers gave almost identical results, therefore the Single Precision solver is sufficient to obtain a correct solution and only 100 iterations are required.