Cavendish Nuclear is turning conventional building techniques inside out to help Magnox Ltd decommission the redundant Sizewell A nuclear power plant.
The company’s innovative solution has earned it a contract worth in the region of £2.5 million to design and build the plant needed to retrieve historic waste from a storage area.
The store contains scraps of metal cladding and other components that were removed from the spent reactor fuel before it was transported off site to be reprocessed.
Its removal and packaging as low-level radioactive waste is the next phase of decommissioning work at Sizewell A, a Magnox station that operated between 1966 and 2006.
Site licence company Magnox Ltd invited tenders for a contract to design and build the plant that will retrieve and sort the waste.
The construction needed to avoid encroaching onto an area under the existing flask transit crane, rendering conventional construction methods unviable.
The solution put forward by Cavendish Nuclear was to build the structure inside out, as project co-ordinator Hugh Grehan explains,
“A conventional construction approach of applying cladding to this elevation of the building was not practicable. We could see an inevitable clash between construction activities and the use of the flask transit crane, so we are building from the inside out.
“The structural frame will be erected and then prefabricated panels will be craned into position and positioned from the inside of the building. The building will meet all the Magnox performance requirements but unusually will have the structural steelwork exposed on the external face.
“This innovation offers considerable programme benefits as the panels are constructed off site, installation of the panels will be a rapid process and we have minimised the need to work from scaffolding, significantly improving site safety.”
The contract includes the supply and installation of a crane and ancillary equipment, and allows for the cutting of three retrieval holes in the roof of the waste store after the completion of construction.
“We were asked to install a secondary floor above the splitter vane store (SVS).
“We would not have crane coverage to the top of the SVS building once the new overbuilding was erected and conventional flooring systems such as precast concrete slabs would be impossible to install, so we developed a lightweight flooring system solution that can be transported into the building by the installed lift.
“This system proved to be more economic and has removed the floor construction from the programme critical path. It also avoids moving heavy concrete slabs, which improves safety on site.”
Work commenced during the summer and is expected to take 15 months to complete.