Six enormous tunnel heads needed for Hinkley Point C nuclear power station’s cooling water system will soon be lifted into place on Bristol Channel's seabed.
The intake and outfall heads will cap the 8km of tunnels which will supply Hinkley Point C’s two nuclear reactors with cooling water.
The precision placement of the 5,000t heads kicks off a summer of complex offshore operations works for the new nuclear power station, which is the first to be built in a generation.
The four intake heads are each 44m long, around 17m high and weigh 4,650t. They are made from 775t of reinforcement, 125,000 individual reinforcing bars and 1,600m3 of concrete.
The two outfall heads weigh 3,500t each. They are made from 250t of reinforcement, 52,000 individual reinforcing bars and 1,100m3 of concrete.
The have now been loaded onto barges at Bristol Port’s Avonmouth docks. The barges will then be towed to meet two floating heavy lift cranes, Guilliver and Rambiz. Due to the weight of the heads the cranes will work in tandem to lower the structures into place on the seabed.
Lifting specialist Mammoet will carry out the loading operation, which will take several hours for each head. The water levels will be adjusted at the dock to ensure the barge can receive the load safely.
The Balfour Beatty built heads are big for a reason. Their size means water will enter the intakes slowly, reducing the number of fish entering the cooling pipes. They are also placed sideways to the tidal flow. In addition, screens and a fish return system will transfer fish back to sea.
The project team completed the construction of the £20M intake heads at Avonmouth in December 2020.
In March 2021 the Hinkley Point C marine works team then poured the final concrete to complete all six heads, completing the work ahead of time.
Balfour Beatty project director Roger Frost said: “Today marks yet another exciting milestone in the construction of Hinkley Point C with the arrival of some of the largest heavy lift vessels in the world, on site. We are now readying ourselves to successfully complete our next feat of engineering: lowering the head structures, which will support the nuclear power station's critical water-cooling system, to the very bottom of the Bristol Channel.”
In October last year the second of three offshore tunnels needed for Hinkley Point C’s cooling water system was completed under the Bristol Channel.
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