Work starts to clear Sellafield nuclear fuel pond

The pond contains more than 15,000m3 of radioactive water, 300m3 sludge and various nuclear wastes

Engineers at Sellafield have taken an important step towards decommissioning a 60-year-old storage pond originally built to store fuel from the Windscale Pile Reactors, by overseeing the retrieval of the first nuclear fuel out of the pond since the 1960s.

The Pile Fuel Storage Pond (PFSP) was the very first nuclear fuel storage pond constructed at Sellafield and it remains the largest open air nuclear storage pond in the world. It was built to store nuclear fuel and isotopes from the Windscale Reactors that produced nuclear materials for the defence industry. The Windscales Piles, as they are known, never actually generated electricity, but were the precursor to the Calder Hall reactor – the first commercial reactor in the world.

The PFSP contains over 15,000m3 of radioactive water, more than 300m3 sludge, various nuclear wastes and legacy spent nuclear fuel in around what was originally 180 metal skips in the pond.

Considerable work has had to be carried out in support of the fuel retrieval. Improvements had to be made to the building structure which started in the 1980s and included the replacement of the skip handler. The project team had to find a solution to the layer of radioactive sludge which has built up on the pond floor and on top of the open skips of fuel. The layer of sludge had to be removed from the fuel skips using a bespoke skip washing mechanism.

Finally, significant modifications had to be made to the bay crane to allow it to be operated remotely to reduce the radioactive dose to the crane driver. Also, the cuboid transport flask had never been used in this facility before and extensive preparations had to be made.

Jim French, Nuclear Management Partners’ (NMP) executive decommissioning director said the decommissioning programme was 5 years ahead of previous expectations. He said: “Our original timescale was to start retrieving this fuel in 2016, however we’ve brought this forward by concentrating resources and technical expertise on what is a priority project. The plan is that all the fuel will now be retrieved by July 2015, however opportunities are being sought to bring this date even further forward.”

About the Pile Fuel Storage Pond (PFSP)

• Built and commissioned between 1948 and 1952, the pond and adjoining decanning building provided the storage and cooling facility for irradiated fuel and isotopes from the two Windscale reactors. The pond processed 2100 tonnes of pile fuel and 300 tonnes of Magnox fuel.
• The pond is a sub-divided outdoor storage pond containing skips of irradiated fuel. The building contains a series of sub-ponds, otherwise known as bays, connected underwater to the main pond.
• All operations in the pond ceased in the 1970s. The plant was left in a care and maintenance regime, whilst operations were then transferred to more modern facilities. Extensive refurbishment and re-equipping took place in the 1980s and decommissioning started in the 1990s. 
• The pond is 100 metres long, 25 metres wide and 7 metres deep, containing over 15 million litres of water. In total there were around 180 metal skips in the pond each holding up to 6m3 of fuel and waste, 26 of these have now been emptied, cleaned and exported by the project team to create space within the pond.
• Sludge retrieval operations commenced in 2008. Six out of the twelve bays have been desludged and the Sludge Retrieval Hood has been deployed transferring sludge into the Sludge Corral, prior to transfer to the Local Sludge Treatment Plant in 2012.