Validation of SOP Procedure for Dealing With FWLB

The State Oriented Procedure (SOP) is developed to improve the existing emergency operation procedures, namely, the Event Oriented Procedure (EOP). It is developed based on the finite Nuclear Steam Supply System (NSSS) states instead of an infinite number of possible events, therefore it can cover all of the events/accidents including the accidents caused by more than one initial event. On the other hand, the operator can take actions without diagnosing the events/accidents according to SOP, and thus the human mistakes which will possible happen during the events/accidents diagnosing can be avoided. However, as a generalized procedure system, the SOP needs a lot of validations based on various events/accidents. In this work, an analysis of a postulated Feed Water Line Break (FWLB) accident for LingAo phase II NPP based on the SOP is given and both the automatic protections and operator manual actions required by the SOP are modeled with an advanced, two-fluid, thermal-hydraulic code called CATHARE. The initial conditions and assumptions are chosen to get a severe state of the NPP. Since the EOP addresses the given accident perfectly, the results are then compared with those based on the EOP for a similar NPP to validate the SOP. The main parameters relevant with FWLB of this NPP are the same with LingAo phase II. Therefore, there is no need to perform analyses based on the EOP for LingAo phase II. The results demonstrate that the main operator manual actions required by the SOP are similar to those required by the EOP, and the operator can take the plant to a controllable safe state according to the SOP procedures. Therefore, the SOP is effective and reasonable for FWLB accident.