The construction and commissioning of the Sizewell B nuclear power station in only 78 months was an outstanding achievement for Nuclear Electric and their vast team of contractors and designers. Cleveland Bridge undertook a key role in the project as main contractor for the steel liner plate to the reactor building - a non-structural protective element that had to behave as a structure during construction.
Sizewell B Power Station |
The pressurised water reactor, with its primary cooling circuit and steam generators is housed in a cylindrical building 45m in diameter and 65m high with a hemispherical roof dome. The building has 1.4m thick pre-stressed concrete walls that are designed to resist the most catastrophic failure of the plant or a major earthquake without leakage. A 6mm thick mild steel plate lines the whole of the interior surface of the building – floor, walls and dome – and is gas-tight: there are more than 200 penetrations for access, pipework and services, and over 400 embedments fixed into the liner plate. The liner plate is securely attached to the concrete by angle ribs and shear connectors. Cleveland Bridge won the contract to fabricate, supply and erect the 2000t of liner plate together with all the embedments, and some major items of equipment that are integral with the plate. The contract presented the company's engineers with one of their most onerous and complex tasks ever. In particular, working with the American specifications (ASME codes) linked to the design, the quality management system for nuclear work (BS5882), and the set of third party inspection authorities within the extended project team presented a major cultural leap – quality assurance was a large part of the company's added value in the workscope. The floor liner plate represented, for Sizewell, a fairly straightforward task enabling the team to adapt to the nuclear culture. The construction of the cylindrical wall liner 45m high presented interesting engineering problems, fabrication challenges and the problems of working in tandem with the civil engineering work. The wall liner plate was fabricate 9m x 3m curved panels for erection in 3m high tiers. This non-structural plate was erected well in advance of concreting so it had to work as a shutter without changing shape and stand up in high winds without collapsing. The spherical shape of the dome liner was much more difficult to fabricate precisely, and it was not practicable to erect it in small panels. The complete dome was assembled at ground level in three horizontal slices, "onion rings", that were lifted into place using a 1500t Gottwald mobile crane. |
This project introduced Cleveland Bridge to construction for the nuclear industry with its rigorous quality requirements, and established the capability to undertake such work successfully.