Engineering teams were able to lift the 304-tonne steel liner ring into place in the early hours of Monday morning thanks to the still wind conditions.
It is the third and final ring to be installed on the building, which will eventually contain one of Hinkley Point C’s two nuclear reactors.
The unit has now grown in height by 11.6-metres and stands at 44-metres.
The liner ring, which was prefabricated in a factory on site, also features supporting brackets for the Polar Crane Beam. This internal crane will rotate 360° above the reactor and be used for refuelling.
The reactor building now only has the ‘lid’ to be placed on top, with the iconic dome lift scheduled for next year.