Sizewell C secures approval for tunnel segment factory

Sizewell C has secured planning permission for a precast concrete production facility at Avonmouth that will manufacture 38,500 segments for the nuclear power station’s three major marine tunnels. The cooling-water system comprises two intake tunnels, each up to 3.5km long and 6m internal diameter, and a common outfall tunnel up to 3.5km long and 8m internal diameter. The three tunnels will be driven by TBMs from land beneath the seabed, extending around 3km offshore. At their deepest point the tunnels are permitted to run up to 35m below the seabed. The two intake tunnels will connect to four offshore intake heads through vertical shafts, while the larger outfall tunnel will connect to two outfall heads. The Avonmouth facility, around 10km north-west of Bristol city centre, will manufacture the precast segmental linings and tunnel heads required for the works. Completed components will be transported to Suffolk by rail and sea. Production is expected to begin in 2028, subject to planning conditions being met. The development will reuse and expand the Avonmouth facility previously established to manufacture tunnel components for Hinkley Point C, Sizewell C’s sister nuclear project in Somerset. Sizewell C said the approach will allow the project to draw on the workforce, manufacturing experience and lessons developed during construction of Hinkley Point C. Temporary infrastructure at Avonmouth will include concrete batching plants, cranes, offices, welfare facilities and storage areas. Daniel Altier, Marine and Tunnelling Delivery Director for Sizewell C’s Civil Works Alliance (CWA), said: “The CWA is committed to not only establishing a state-of-the-art factory that will manufacture the 38,500 segments required for the three tunnels, but also to train a skilled workforce, with the majority coming from the local area.” Early works are already underway, with 55 people directly employed by the CWA at Avonmouth and a further 86 supply-chain workers on site. The facility is expected to support up to 400 jobs. Sizewell C CEO Nigel Cann said manufacturing the precast components off site and transporting them by rail and sea would reduce construction traffic in Suffolk while building on the prefabrication techniques developed at Hinkley Point C. “By reusing existing infrastructure and experienced teams, we can reap the benefits across safety, quality, cost, and schedule,” he said. Sizewell C has committed to moving at least 60% of construction materials by rail and sea. The three marine tunnels will form the main cooling-water system for the two-reactor, 3.2GW Sizewell C nuclear power station on the Suffolk coast. Comments: