Westinghouse Electric Co. (NYSE: TOSBF) has developed and implemented a passive thermal shutdown seal at the 851 MW Unit 1 at the Farley Nuclear Power Plant in Alabama. Plant owner Southern Nuclear Operating Co. (NYSE: SO) said it also plans to install the seal, known as the “Shield” at the Farley Station’s 860 MW Unit 2. Both units are Westinghouse three-loop pressurized water reactors.
The design is applicable to all Model 93A Westinghouse reactor coolant pumps. It is designed to protect a nuclear plant’s reactor core by preventing loss of reactor coolant system water inventory should an event occur that causes a loss of all reactor coolant pump seal cooling.
The Shield passive thermal shutdown seal is activated by heated reactor coolant and provides a tight seal if cooling for the reactor coolant pumps seals is lost. Westinghouse said installing the shutdown seal reduced the estimated risk of core damage by s40 percent.
The seal is made to improve Mitigating System Performance Index (MSPI) margin by reducing reactor coolant pump (RCP) seal cooling vulnerabilities and decreasing core damage frequency by up to 50 percent. Westinghouse said it has been proven reliable for a minimum of 24 hours under station blackout conditions and an additional 48 hours after blackout with residual heat removal pumps operational.
The Shield seal safety evaluation report has been reviewed and approved by the NRC for the Model 93A RCP and is acceptable for referencing in licensing applications for nuclear power plants that install the Westinghouse reactor coolant pump shut down seal. Approval for other RCP models is expected in early 2012.
Subscribe to Nuclear Power International