Vogtle nuclear update: Milestones at Units 3-4 construction sites

Vogtle unit 4 water storage
Photo courtesy Georgia Power

By Rod Walton, Power Engineering and POWERGEN Content Director

Georgia Power announced two major milestones for the Unit 3 and 4 construction projects expanding the Vogtle nuclear power plant.

All modules for the $25 billion-plus project have been set in place, with a massive water tank lifted to its position atop the Unit 4 containment vessel and shield building roof. It was the last major crane lift at the site in Waynesboro, Ga., after nearly a decade of work.

Perhaps even more timely is the announcement that hot functional testing was started for Unit 3, which will enter commercial operations first among the two new units at Vogtle. Unit 3 is expected to go online later this year or early next year, depending on timetables complicated by COVID-19 and other issues.

Hot functional testing is conducted to verify the successful operation of reactor components and systems together and confirm the reactor is ready for fuel load. As part of the testing, the site team will begin running Unit 3 plant systems without nuclear fuel and advance through the testing process towards reaching normal operating pressure and temperature.

Over the next several weeks, nuclear operators will use the heat generated by the unit’s four reactor coolant pumps to raise the temperature and pressure of plant systems to normal operating levels. Once normal operating temperature and pressure levels are achieved and sustained, the unit’s main turbine will be raised to normal operating speed using steam from the plant.

During these series of tests, nuclear operators will be able to exercise and validate procedures as required ahead of fuel load. Hot functional testing is expected to take six to eight weeks.

As for Unit 4, scheduled to be commercial operational in late 2022, the passive containment cooling water storage tank was put into place as a major part of the AP1000 reactor’s advanced passive safety system.

Known as CB -20 (pictured), the storage tank stands 35 feet tall, weighs more than 720,000 pounds and will hold approximately 750,000 gallons of water ready to flow down in the unlikely event of an emergency to help cool the reactor.

According to Georgia Power, the AP1000 plant’s passive safety systems require no operator actions to mitigate potential emergency situations. These systems use only natural forces such as gravity, natural circulation and compressed gas to achieve their safety function. No pumps, fans, diesels, chillers or other active machinery are used, except for a few simple valves that automatically align and actuate the passive safety systems.

Construction on Units 3 and 4 began in 2013 and have proceeded despite cost overruns, the bankruptcy of contractor Westinghouse (later replaced by EPC firm Bechtel) and the workforce delays brought on by the coronavirus pandemic.

Once operational, Vogtle Units 3 and 4 will be the first new nuclear generation systems brought online since the TVA’s Watts Bar Unit 2 several years ago and only the second such projects in more than 30 years.

The U.S. nuclear energy sector has never had an accident which resulted in direct loss of human life. The worst was the Three Mile Island radiation leak in 1979 which led to a partial meltdown at Unit 2 and release of radioactive emissions.

Nuclear power plants currently account about 20 percent of the U.S. net generation and more than half of the nation’s carbon-free electricity.

(Rod Walton, a 13-year veteran of covering energy issues both as a newspaper journalist and trade editor, is content director for Power Engineering, POWERGEN International and the online POWERGEN+ Series. He can be reached at 918-831-9177 and rod.walton@clarionevents.com about story ideas of sessions for POWERGEN live or online).

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