The Nuclear Decommissioning Authority

 

Built 60 years ago, the Pile Fuel Cladding Silo, was Sellafield's first storage facility for Intermediate Level Waste (ILW) and, like any building exposed to British weather for decades, needs care and attention.

Its initial function was to store the outer metallic parts – the cladding - of the irradiated fuel elements from the Windscale Piles.

The cladding was shaved off in underwater decanning plants, to be stored in the facility as ILW, while more active spent fuel was consigned to a storage pond.

In later years, fuel cladding from the Magnox fleet, including Calder Hall and Chapelcross, was also transferred to the facility and by 1964, it was full.

The facility has six tall chambers known as silos, arranged side by side and holding more than 3,400 cubic metres of waste. Emptied in from above, the precise composition of this mixed radioactive material remains to be established before treatment can take place.

The atmosphere inside the chambers was changed in the 1980s from air to the inert gas argon, which reduces fire risks significantly but, although non-toxic, cannot be breathed and therefore prevents direct workforce access.

External refurbishment, including extra radioactive shielding, has already been carried out on the building to ensure that the safe storage of waste can continue. Meanwhile, the waste ultimately needs to be removed from the silo, treated and immobilised in cement for long-term storage until the deep Geological Disposal Facility (GDF) becomes available. 

Finally, the facility will need to be decommissioned and demolished in a programme that will stretch well into the future, and cost at least £600 million. Planning and design work on the facilities needed has been under way for many years and work is now taking place to construct a super-structure adjoining the silo which will house a range of equipment to retrieve the contents.

Holes will be cut into the side of the silo so each compartment can be accessed in turn – trials of this work are under way. A remotely operated grab will then reach inside and bring out the waste for a process of analysis and characterisation before it is packed into boxes, with retrievals due to start in 2017.

The collected data will be used as a basis for designing a waste treatment facility which will condition the boxed waste for long-term storage before it is eventually disposed of in the GDF.    

 

"There is a highly skilled and motivated team driving forward the work towards the safe retrieval of waste from this legacy facility." Dr Ian Hudson, NDA Head of Programme, Sellafield

 

A schematic of the superstructure under construction