Tunnel breakthrough at Hinkley Point C

By Mike Hayes06 October 2020


Onshore cooling water tunnel at the UK’s Hinkley Point C power station

UK-based contractor Balfour Beatty has broken through on a significant tunnelling project, as part of the construction of the Hinkley Point C nuclear power station in Somerset, England.

With the completion of the longest and final onshore cooling-water tunnel at the power station, the company has finalised its sprayed concrete lining works on the site.

In total, across the five onshore tunnels it was tasked with constructing, Balfour Beatty says it has so far spent more than 1.6 million hours on the project.

On the final tunnel, some 600m of ground was excavated, before being sprayed with 9,000m3 of concrete to stabilise the tunnel structure.

With the spraying work complete, secondary lining work will follow, as well as the addition of reinforced rebar concrete structures to further shore up the tunnel.

When fully operational, the tunnels will transport over 120,000 litres of water per second to the plant from the Bristol Channel.

For the main cooling water system, the Balfour Beatty team has again been tasked with the tunnelling work and has prepared three portals through which three tunnel boring machines (TBMs) will launch.

Ultimately, there will be three 3.5km intake tunnels and one 1.8km outfall tunnel.

The first TBM is already underway, and Balfour Beatty says it has currently travelled more than 2.5km at a depth of 33m beneath the Bristol Channel.

As it cuts through the rock it will line the tunnel with a ring of concrete segments, each one weighing over 4,000kg.

Commenting on the progress made with the onshore tunnelling work, Alistair Geddes, Balfour Beatty project director for Hinkley Point C’s tunnelling and marine project, said, “This is a significant step forward in the successful delivery of the first new nuclear power station in the UK for over 20 years.”

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