Abstract
U.S. Nuclear Regulatory Commission (NRC) and French Nuclear Specialist successively point out that although the decay power of Pressurized Water Reactor (PWR) in Mid-Loop Operation (MLO) during the outage is quite low (<0.5%), once the normal Residual Heat Removal (RHR) is lost, the possible system responses and thermal hydraulic phenomena involved are quite complicated. If it was not handled by correct procedure, the safety risk is higher than that of normal operation. Mid-loop operation state is a very special condition which involves low temperature, low pressure, fluid stratification, and abundant non-condensable gas in the Reactor Coolant System (RCS). Most generic system safety analysis codes (RETRAN, RELAP5) are difficult to simulate this kind of state, so as the RETACT code, a thermal hydraulic code installed in Maanshan Nuclear Station training simulator. In the light of this situation INER Integral System Test (IIST) Facility was rearranged to conduct the mid-loop operation tests, and also devoted effort to develop a computer code(ROSE: Reactor Outages Simulation & Evaluation) particularly aiming at the analysis of reactor shutdown thermal hydraulics. The purpose of this thesis is to evaluate RETACT code in simulating Mid-loop operation event and to implement ROSE code into the training simulator. ROSE code will replace RETACT code for the simulation of Mid-loop operation. The final goal is to improve the integral simulating capability of Maanshan Nuclear Station training simulator.