Large Eddy Simulation of the injection of cold ECC water into the cold leg of a pressurized water reactor

摘要

The aging of the reactor pressure vessel (RPV) can be a limiting factor for the lifetime extension of pressurized water reactors. In case of loss of coolant accidents, cold emergency core cooling (ECC) water will be injected under high-pressure thermal-hydraulic conditions into the cold leg that is filled with hot coolant The hot RPV wall can be exposed to this cold fluid, suffering important thermal stresses. This process is called pressurized thermal shock (PTS). The efficiency of the PTS depends on the mixing between cold ECC water and hot coolant in the cold leg and the upper downcomer. A single-phase PTS scenario was investigated experimentally in the TOPFLOW facility under representative thermal-hydraulic conditions. A transient of 390s of this experiment is analyzed here numerically with Large Eddy Simulations and two different hypothesis to account for thermal effects: incompressible fluid and dilatable fluid (low Mach number compressible fluid). Detailed information is given on the temporal development of both thermal stratification and flow behavior in the cold leg. Calculated temperature profiles in the cold leg are compared to detailed temperature measurements. The dilatable approach reproduces well the experimental results and outperforms the incompressible fluid approach.