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Nuclear reactor buildings

Best value for the public purse and peace of mind

The two reactor buildings at Bradwell required weather envelopes capable of covering and protecting both buildings for the next 100 years.

ClientVinci Construction/Magnox
ExpertiseEngineering design and environmental assessment


Radiation levels will decay naturally over this period, after which the buildings will be demolished. The client wanted a result that would minimise the need for inspection and maintenance activities, and reduce onsite personnel requirements over the decades. The capacity of the buildings to withstand environmental loads also had to be assessed, and any required building strengthening designed.


A 3D laser scan of the buildings was carried out in order to produce a millimetre-accurate as-built model enabling seamless integration of the new structural works with the old. 3D modelling was used to assess the capacity of the new envelopes to withstand environmental loads such as wind and snow. Our building services engineers also modelled how the internal environment would react to a range of external ambient conditions.


Our cocoons will protect the local environment and community from the unpredictable decay of the old structures. The 40m high, 40m deep, 85m long envelopes, made from weathertight aluminium Kalzip cladding, were completed in September 2016. They incorporate passive ventilation to reduce corrosion-causing condensation and remove the need for maintenance activities, keeping site operatives safe and workforce needs to a minimum. The buildings will only have to be inspected every five years. Bradwell is now a ‘safe store’, which means the costs of immediate disassembly and disposal of radioactive waste have been avoided. It’s intended that a similar solution will be used at Hunterston A in Scotland.

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