Low Temperature Overpressurization Protection System setpoint analysis using retran for Salem

The Low Temperature Overpressurization Protection System (LTOPS) is designed to protect the Reactor Pressure Vessel (RPV) from brittle failure during startup and cooldown maneuvers in Westinghouse Pressurized Water Reactors. For the Public Service Electric and Gas Company Salem power plants, the Power-Operated Relief Valves (PORVs) mitigate pressure increases above a setpoint where an operational startup transient may put the RPV in the embrittlement fracture zone. The 10 CFR 50 Appendix-G limit, given by the Salem Technical Specifications, conservatively bounds the maximum pressure allowed during those transients where the RPV can suffer brittle fracture (usually below 350°F). The Appendix-G limit is a pressure versus temperature curve that is more restrictive at lower RPV temperatures, and allows for higher pressures as the temperature approaches the upper bounding fracture temperature. Salem currently uses a very restrictive constant LTOPS setpoint pressure. Since there is only about 50 pounds per square inch between the minimum pressure to start and run a Reactor Coolant Pump (RCP) and the current PORV setpoint, it is difficult to start an RCP without actuating LTOPS, which is a reportable licensing event. A new methodology is presented for determining an LTOPS pressure setpoint that is less restrictive than the current setpoint, but still conservative enough to protect the RPV from any credible pressurization transient. This new setpoint has the potential to decrease the number of LTOPS actuations by providing more operating margin during startup and cooldown maneuvers.