Westinghouse Electric Company said Tuesday that two new power plant modules, CAO3 and CAO2, are now in place for Unit 2 at the V.C. Summer Nuclear Station project that is underway in Jenkinsville, S.C.
The two recently placed modules, the final two "super modules" for Unit 2, make up the in-containment refueling water storage tank (IRWST) in the Unit 2 containment building. The tank, which holds up to 500,000 gallons of borated water, is positioned above the reactor and relies on gravity as the only driving force needed to release the water to keep the reactor cool should the reactor experience an unexpected shutdown.
They are considered super modules, because they are too large to transport and, thus, must be constructed on site and hoisted into place by use of a 560-feet tall heavy lift derrick.
Workers placed the CA03 super module in the nuclear island July 20 and the CA02 super module Aug. 5. The structural steel modules weighed 250 tons and 60 tons, respectively.
The AP1000 plant under construction relies on the “laws of nature,” to maintain containment and to automatically shut down the reactor without human intervention for up to 72 hours. Westinghouse said the safety features built into the plant, which make use of such forces as gravity, natural circulation and condensation, are known as passive, because the plant's safety does not require operator actions, mechanical equipment or even AC power to function.
The passive systems provide operators with the time necessary to achieve and maintain safe shut down of the plant “in the unlikely event of a design-basis accident,” Westinghouse said.
V.C. Summer Unit 2 is a part of a global fleet of AP1000 plants now under construction at Jenkinsville and at Waynesboro, Ga., at Plant Vogtle. There are also two units each under construction at the Sanmen and Haiyang sites in China.