Thermal hydraulics experiments on the behaviour of a safety relief sparger (SRV) and a containment spray system are carried out at the PPOOLEX facility at Lappeenranta University of Technology (LUT). The effectiveness of mixing a thermally stratified water pool due to injection through a sparger is studied. Modelling work is done at VTT Technical Research Centre of Finland Ltd (VTT) and at Kungliga Tekniska Högskolan (KTH).
Summary of the experimental work at LUT:
Efficiency of mixing a thermally stratified pool with the help of steam injection through a safety relief valve (SRV) sparger pipe or water injection through a residual heat removal (RHR) nozzle has been studied in tests carried out with the PPOOLEX facility in 2016. In 2017, the SRV sparger will be moved to the center of the pool and the submergence will be reduced from 1.8 to 1.5 m. This will allow developing a thicker stratified layer at the bottom and will contribute to the Effective Heat Source (EHS) and Effective Momentum Source (EMS) models based on the Richardson scaling. A small-scale separate effect facility, where it is possible to measure directly the effective momentum induced by a steam injection through a single hole, will be designed and constructed. Tests with the facility will help to map the effective momentum of many condensation regimes. Closures for the EMS model development for spargers by KTH will be provided.
Wet well spray tests for studying the interplay between the suppression pool behavior and the spray system will continue. Mixing of a thermally stratified pool as a result of spray injection from above will be of interest. With the help of pre-test simulations done at VTT and KTH a representative test matrix, the initial thermal hydraulic state of the facility and the correct spray injection rate to be used can be determined.
Summary of the modelling work at VTT:
Pre-calculations will be performed with ANSYS Fluent for the small-scale separate effect facility, where steam will be injected through a single hole into water pool. The Euler-Euler method of Fluent with condensation model will be used. The effective momentum and heat sources generated by the steam injection into the water pool will be studied and later compared to the experimental results.
A spray experiment performed at PPOOLEX will be calculated with ANSYS Fluent. The water pool will be modelled with the Euler-Euler model of Fluent, where droplets will be described with the Discrete Particle Model (DPM). The effect of the spray droplets on the stratified pool will be calculated. The results will be compared to PPOOLEX experiment.
Summary of the modelling work at KTH:
KTH will perform pre-test analysis and simulations for selection of operational regimes and test procedures, and post-test analysis and validation with EHS/EMS models implemented in GOTHIC against PPOOLEX tests. Further development of the EHS/EMS models for spargers and RHR nozzles will be pursued to simulate dynamics of the pool mixing and stratification. The models will be validated against respective separate effect tests.