Latest from Vogtle: Unit 3 hot functional testing begins, Unit 4 water tank placed

April 27, 2021, 3:01PMNuclear News
The CB-20 module is placed atop the Vogtle-4 containment vessel. Photo: Georgia Power

Georgia Power yesterday announced two significant milestones at the Vogtle nuclear plant’s expansion project: the commencement of hot functional testing at Unit 3 and the placement of Unit 4’s passive containment cooling water storage tank, known as CB-20.

Final exam: Hot functional testing comprises the last series of major tests for Vogtle-3 ahead of initial fuel load. The tests are conducted to verify the successful operation of reactor components and systems together and confirm that the unit is ready for fuel load. As part of this testing, Georgia Power said, the site team will begin running Unit 3 plant systems without nuclear fuel and advance through the testing process toward reaching normal operating pressure and temperature.

Over the next several weeks, the heat generated by the unit’s four reactor coolant pumps will be used to raise the temperature and pressure of plant systems to normal operating levels, according to the utility. 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 this series of tests, nuclear operators will be able to exercise and validate procedures as required ahead of fuel load. Georgia Power expects hot functional testing to take six to eight weeks.

Passive and massive: Placement of the CB-20 module atop the Unit 4 containment vessel and shield building roof represents the last major crane lift for the Vogtle project. Standing 35 feet tall and weighing more than 720,000 pounds, CB-20 will hold approximately 750,000 gallons of water that will flow down to help cool the reactor in the event of an emergency. The water can also be directed into the spent fuel pool, while the tank itself can be refilled from water stored elsewhere on-site.

In case you missed it: In January of this year, Georgia Power announced that Vogtle-4 had begun integrated flush, the testing process that pushes water through the permanent plant system piping that feeds into the reactor vessel and reactor coolant loops.

Recently achieved milestones at Unit 3 include the initial receipt of nuclear fuel assemblies and the completion of the condenser vacuum test, both in December 2020, and in October 2020, the completion of cold hydro testing, which confirms that a reactor’s coolant system functions as designed and verifies that the welds, joints, pipes, and other components of the coolant system and associated high-pressure systems do not leak when under pressure.


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