On September 20th a CNSL team consisting of James Fisher Nuclear (JFN) and Shepley Engineers Limited (SEL) successfully started deflector plate cutting operations on the Pile Fuel Cladding Silo (PFCS) facility at Sellafield. This is the culmination of a collaborative working approach since 2012 when CNSL was awarded the first phase of the contract which would eventually see the removal of redundant steelwork in preparation for waste-retrieval operations.

Key to the success has been a full scale mock-up of the top section of the PFCS at JFN’s Egremont facility, where CNSL and Sellafield Limited (SL) teams have been co-located and working collaboratively. This allowed the CNSL team to design and manufacture, develop and optimise the equipment and processes; the Sellafield project team were also able to validate the approach and ensure that the project fitted into the overall “Silo programme".

“The first phase of the project to remove debris from on top of the plates went like clockwork because of the preparatory work in the full-scale mock-up of PFCS. Whilst the debris-removal operations were on-going, we worked on the cutting process and managed to substantially increase its speed and efficiency. Transfer to site operations has been a smooth process and we are now making excellent progress” Graham Parker, JFN Project Manager.

The cutting is being carried out with a water jet containing entrained abrasive. John Reekie, the JFN senior engineer commented:

[This] cutting method was selected as it is quick and efficient and does not generate excessive heat or sparks. Cutting accuracy is essential for efficient operations and vital to meet strict water usage targets. Using the Full Scale Test Rig we were able to develop techniques which could meet the challenging technical requirements and overcome replicated spatial constraints whilst proving the viability of the chosen solution and simultaneously training and up-skilling operators prior to site works

Gary Snow, Head of the PFCS programme said: “It’s a highly unique and complex engineering challenge, but we have the right people and the right technology to safely make this key step forward in the decommissioning journey of the building.”

You Tube Video of the Jet cutter in action

Background information on the PFCS
The Pile Fuel Cladding Silo is one of four Legacy Ponds and Silos facilities at Sellafield prioritised for clean up by the NDA as part of our hazard and risk reduction programme.

PFCS consists of a series of silos built in the 1950s to store intermediate level waste from the Windscale Pile reactors. A programme of work is underway to safely retrieve this material and package into a passively safe form (in 3m3 boxes) ready for disposal. A new retrievals ‘superstructure’ building has been erected in a small footprint directly adjacent to the silo to house the machinery which will reach into the silo to grab the waste so it can be transferred into shielded containers. Another challenging aspect of the programme is because the facility contains high levels of argon gas to prevent possible combustion, therefore preventing human access.

The PFCS Programme Strategy is to retrieve waste, interim store in 3m3 boxes in BEPPS/DIF subsequent to treatment prior to final disposal in the Geological Disposal Facility (GDF).

Project background
During its operational life, the PFCS contents were gravity-fed into the silo. To ensure the contents were evenly distributed, the silo was fitted with steel “deflector plates” supported on a steel framework. Prior to waste retrieval operations commencing, this steelwork has to be cleared of obstructions and cut up. The interior of the silo is not man-accessible. There are limited penetrations and camera positions, and throughout all operations, the silo’s sensitive atmosphere which contains the inert gas Argon has to be maintained to eradicate the risk of fire.

Fore more information visit the James Fish Nuclear dedicated site.