The module that will house the reactor pressure vessel of the second AP1000 unit under construction at the VC Summer site in South Carolina has been installed. Meanwhile, the reactor vessel itself has been delivered to the site.

The 32-tonne CA04 module — also known as the reactor vessel cavity — was placed on the containment vessel bottom head of Summer 3 on 29 June, South Carolina Electric & Gas (SCE&G) said in a statement yesterday.

The module is over eight metres tall and 6.4 m in diameter, and comprises five sub-modules, which were fabricated in Lakeland, Florida by MetalTek International’s SMCI division. These were then assembled on site in the modular assembly building, moved to the nuclear island as one piece and lifted into place using one of the largest cranes in the world — a heavy lift derrick that stands about 170 metres tall.

The construction milestone at Summer 3 was reached the day after the reactor pressure vessel was delivered to the site. The vessel had been transported to the site by rail from the Port of Charleston.

SCE&G said that once the CA04 module is fully encased in concrete, the reactor vessel will be lowered into it and mounted on top.

The AP1000 design uses modular construction techniques, enabling large structural modules to be built at factories and then installed at the site. This means that more construction activities can take place at the same time, reducing the time taken to build a plant as well as offering economic and quality control benefits. According to Westinghouse, factory-built modules can be installed on-site within a planned three-year construction schedule.

Two AP1000s are being constructed as units 2 and 3 of the Summer plant. Construction officially began on Summer 2 in March 2013, with the pouring of the concrete basemat for the unit. That for unit 3 was poured in November 2013. The CA04 module for unit 2 was put in place in September 2013. Unit 2 is scheduled to begin operating in mid-2019 with unit 3 starting up in early 2020.

Another two AP1000s are also under construction as units 3 and 4 of the Vogtle plant in Georgia. Construction of the units began in March and November 2013, respectively. The CA04 module for unit 3 was installed in December 2013, while that of unit 4 was put in place last month. Those reactors are also scheduled to start operation in 2019 and 2020, respectively.

Four further AP1000s are being built in China, two each at Sanmen and Haiyang. All four Chinese units are scheduled to be in operation by the end of 2017.

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