Analysis of the Feed & Bleed procedure for the Ascó NPP: First approach study for operation support

The Asociación Nuclear Ascó-Vandellòs (ANAV) is the consortium responsible for the Ascó and Vandellòs-II reactors. The reactors are Westinghouse-design 3-loop PWRs with an approximate electrical power of 1000 MW. In order to operate the reactors ANAV prepared an Integral Plant Model for each plant. The model is used for supporting plant operation and control from the point of view of safety and competitiveness. The Technical University of Catalonia (UPC) has been working with ANAV in order to establish, qualify and use these Best Estimate (BE) models. This paper develops a specific use of the Ascó plant model for operation support and tries to clarify a group of scenarios related to the total loss of feed water (FW) and the corresponding Feed & Bleed (F&B) recovery procedure. The study characterizes the procedure with different calculations and provides results that have become helpful in establishing the impact of partial availability of Power Operated Relief Valves (PORVs) and HPIS trains, the maximum time for starting the procedure and some considerations on heat sink recovery. The use of the BE model provides a consistent overview of the final problem. The results of the analysis are a first approach for operation support.