Abstract
The performance of passive safety systems of a natural circulation BWR in a Large Break Loss Of Coolant Accident (LB LOCA) is evaluated with integral tests using a scaled test facility and RELAP5 (Mod3.3) code simulation. The Main Steam Line Break (MSLB) test has been conducted in the Purdue University Multi-Dimensional Integral Test Assembly (PUMA) with the initial conditions given by the code simulation. The PUMA facility is designed to reproduce thermal-hydraulic phenomena during the low-pressure blowndown and long-term cooling period of the LOCA transient. The MSLB test is initialized when Reactor Pressure Vessel (RPV) depressurizes to 1 MPa (150 psi) and lasts for 8 hours. This test aims to demonstrate the performance of passive safety systems during the LB LOCA. Test results show that core heat-up is not observed during the test transient due to the function of Emergency Core Cooling System (ECCS). The containment peak pressure and temperature are below the design limit, which is mainly contributed by the function of Passive Containment Cooling System (PCCS). The MSLB accident transient has been simulated with RELAP5 code using prototypic plant mode and test facility model. The code models give reasonably accurate predictions on most system behaviors, while having some distortions for certain local phenomena. The integral test scalability and code applicability are evaluated by comparing the test data and the code simulation results, taking into consideration of the scaling methodology and code uncertainties.
