Turbulence modeling of thermal and fluid mixing in PWR's during high-pressure coolant injection using COMMIX-1B

The purpose of this study is to analyze the thermal and fluid mixing in a pressurized water reactor during the high pressure coolant injection (HPI). The postulated consequence of the primary side overcooling is generally referred to as thermal shock. Recently, there has been several publications discussing the effect of primary side overcooling on reactor vessel integrity. When the ratio of loop flow to HPI flow is high, the Reynolds number is generally high, the Froude number is small, and the agreement between experimental results and numerical prediction is poor without the proper turbulence modeling. In this case, near the injection, both buoyancy effects amd turbulence mixing are very important. The 2-equation (kappa-epsilon) turbulence modeling proposed by Launder and Spalding and modified by Sha and Launder is used for the present model with some modifications. The current calculations were performed using COMMIX-1B, an extended version of the COMMIX-1A computer code