Transient Analysis of Pressurizer Steam Bleed Valves Stuck Open for 700 MWe PHWRs

Indian pressurizer heavy-water reactor (700 MWe) is a horizontal-channel-type nuclear reactor with partial boiling present at the outlet of channels. Heat which is generated due to fission reaction in the reactor core is transferred to primary coolant through primary heat transport system. There are two loops in the primary heat transport system, and each loop is in the shape of figure-of-eight and has two steam generators connected in series. The steam generated in the steam generators through the transfer of energy from primary side drives the turbine for generation of power. Primary heat transport system (PHTS) pressure control is done with the help of pressurizer. It has heaters and two pressurizer steam bleed valves (PSBVs). Pressurizer level control is achieved by feed and bleed control system. In this work, it is postulated that both the pressurizer steam bleed valves are stuck open. The scenario can be the result of faulty pressure control signal and is thus analyzed in this work. The impact of such an event on the overall safety of the reactor is hereby analyzed using in-house developed computer code ATMIKA-T. ATMIKA-T code is a coupled thermal hydraulics and 3D neutron kinetics computer code which captures the plant dynamics.