Abstract
ABSTRACT The loss of coolant accident (LOCA) is an important issue of design basis accidents (DBA) because it will cause the failure of containment. This thesis has focused on the investigation of the main steam line break and recirculation line break (Double ended guillotine) for the Mark-III containment to ensure that the containment must withstand the peak values of pressure and temperature loadings as an accident impact occurs. We have utilized GOTHIC program to establish the short-term and long-term analysis models respectively. For the short-term analysis model, we have adopted the blowdown mass and energy release data offered from final safety analysis report (FSAR) to build up the boundary condition. For the long-term analysis model, we have joined the RPV and ECCS models with the homogeneous equilibrium critical flow model to calculate the value of blowdown rate. Furthermore, given in more confident and crucial, the short-term analysis model and the long-term analysis model of the conditions have been assumed to be different, in which the initial water level of suppression pool is higher for the short-term one but lower for the long-term one. As a result, the simulated data have been compared to the data of FSAR, and we will analysis and specify the reasonableness and corrections of the results. In conclusions, the given results from this work are consistent with the data of FSAR dependent on time. More importantly, the peak value of the temperature and pressure for this accident is much lower than the designed safe value so the containment will be safe and sound when a single accident event occurs. Key words：GOTHIC、Mark-III、Containment、LOCA、DBA