Magnox North is currently 14 years into the proposed 100 year decommissioning program for Hunterston A nuclear power station, a program which they intend to reduce considerably. Having successfully de-fuelled Hunterston’s twin reactors they are currently mid way through the care and maintenance preparations of the program.
Decommissioning of the stations fuel storage pond requires the pondto be dewatered. In order to undertake testing works to establish the best methodology for decontaminating the pond walls the water level needed to be lowered. Lowering the water level across the entire pond to carry out trials would expose a large contaminated surface area of pond wall and so was not an expectable solution. It was proposed that one of the loading bays be sectioned of from the main pond. “B” bay being the more suitable and the smaller was chosen.
Proserve and Norfolk Marine Ltd were approached by Magnox to design a solution that would allow “B” bay to be sectioned off. A full height permanent shutter was designed which once filled with micro concrete would dam off “B” bay. It then fell for Norfolk Marine to carry out full scale tests of the fabric formwork seals, then construct, install and fill the permanent shutter. Testing of the seals was carried out at Norfolk Marines base in Co. Donegal on a full scale mock up of the pond section to be sealed. Testing was completed in 2008
A full size shutter was then built, due to the capacity of the stations gantry crane the shutter was constructed from aluminium, in order to save more weight the shutters faces were fabric stretched over an aluminium weld mesh. The shutter was transported to site and installed in sections by NM’s staff working in C2 and C3 conditions from specially constructed plastic modular work pontoons. Once in place the fabric formwork seals and then the main shutter were pump filled with micro concrete to form the dam.