The first of two 13m long reactor pressure vessels (RPV) will produce enough energy alone to generate electricity for 3m homes. With two units, the power station will provide Britain with 7% of its electricity.

This major milestone comes less than 12 months after the huge steel dome was lifted in place to close the reactor building. The reactor is the first to be installed at a British power station since Sizewell B’s in 1991.

The RPV is a 500-tonne steel container that holds nuclear fuel used to make heat to produce steam for the world’s largest turbine, from Arabelle Solutions. The RPV, manufactured by Framatome in France, arrived at Hinkley Point C in February last year and has been in store until the installation, which was completed yesterday.

In a precision operation, the RPV was lifted onto rails and inserted through a 19.5m high equipment hatch, before being rotated by the large internal polar crane and lowered onto a support ring with just 40mm clearance on either side.  It will be flanked by four 25m high steam generators due to be fitted next year.

The installation marks another step forward in the fit out of the power station with equipment, including 360km of pipes and 10,000km of cable. This is the first of two nuclear reactors to be installed at Hinkley Point C.