Owner/Operator: Florida Power & Light
Florida Power & Light’s St. Lucie Unit 2 reactor vessel head and steam generator replacement project was an ambitious undertaking that required more than a year of intensive planning before the outage began. The highly motivated and experienced project team’s accomplishments are without equal. The team surely set a new industry standard for integrating a highly complex maintenance outage.
Florida Power & Light Co. (FPL) completed a scheduled refueling and maintenance outage at its St. Lucie Nuclear Power Plant Unit 2 during the fourth quarter of 2007 (Figure 1). But calling it merely a maintenance outage does a disservice to the project team. This was no routine refueling outage. It’s my opinion that this was one of the most ambitious and complex outages ever attempted in the nuclear power industry.
1. Florida coast fixture. Florida Power & Light’s St. Lucie Unit 2 recently completed a maintenance and refueling outage by replacing two steam generators, a reactor vessel head, and a reactor coolant pump while handling thousands of other work activities. Source: Nuclear Regulatory Commission
This project also demonstrates how fast a utility can spend millions in capital improvements to keep a nuclear plant in tip-top shape and ready for another 25 years of service.
St. Lucie Nuclear Power Plant is located on Hutchinson Island, about 8 miles southeast of Fort Pierce, along the east coast of southern Florida. It consists of two 829-MW pressurized water reactors, each featuring a freestanding carbon steel containment vessel with a reinforced concrete shield building forming an annular space between the vessel and shield building. Unit 1 entered commercial service in June 1976; Unit 2 followed in August 1983. Both units’ operating licenses were renewed by the Nuclear Regulatory Commission (NRC) in October 2003. The reactors were provided by Combustion Engineering.
A significant amount of work
The outage that earned Top Plant recognition began when Unit 2 was taken off-line Sept. 30, 2007, for the 17th refueling outage since it began commercial operation in 1983. More than 16,500 activities were accomplished during the outage. In addition to routine maintenance and the replacement of one-third of the unit’s 217 uranium fuel assemblies in the reactor core, the centerpiece of the outage work package was replacing the two steam generators and the reactor vessel head. Each steam generator is 63 feet tall, 19 feet in diameter, and weighs close to 500 tons. The reactor vessel head might be thought of as the reactor’s "lid," although it is about 8 feet high, 16 feet in diameter, and weighs more than 70 tons (Figure 2).
2. Off with its head. The old reactor vessel head was removed and then upended as it was extricated from the containment building Courtesy: SGT
The outage also included replacement of one of Unit 2’s four 6,500-horsepower reactor coolant pump motors; an alloy 600 mitigation project that deposited 120 pounds of weld metal on components in the containment area; and modifying the containment sump, a system inside the containment building that is used to collect and filter spilled coolant for reuse in the event of an accident.
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