Pile Fuel Cladding Silo – Potential use of Remotely Operated Vehicles (ROVs) for waste retrieval
31 January, 2014
NES’ facilities at Beckermet, Cumbria have hosted a demonstration showing the use of remotely operated vehicles (ROVs) and how they could be potentially used as part of the decommissioning process. Commissioned by Sellafield Ltd via Cavendish Nuclear who are part of Progressive DSA, NES have been working alongside Sellafield Ltd to demonstrate the concept of utilising tried and tested remote operated vehicles (ROVs) to extract Intermediate Level Waste (ILW) from the Pile Fuel Cladding Silo (PFCS) for containerisation and storage in purpose built stores on the Sellafield site.
The PFCS, built more than 60 years ago, was Sellafield Ltd's first storage facility for ILW. The original purpose was to store the cladding (outer metallic parts) removed from the irradiated fuel elements from the Windscale Piles.
In the intervening years, fuel cladding from the Magnox fleet, including Calder Hall and Chapelcross, was also transferred to the facility until it reached capacity in the early 1960s. The composition of this mixed radioactive material poses one of the more onerous challenges for the project team.
The series of demonstrations at NES Beckermet showcased a means of removing the waste from the silo that is currently being used on the equivalent Berkeley and Trawsfynydd Magnox stations, both are currently undergoing decommissioning. The demonstration involved the use of ROVs operating within a facility that mimics aspects of a silo compartment on a small scale. The two ROVs used were approximately half the size of the proposed active system and the facility was scaled accordingly.
Two Brokk ROVs demonstrated a range of operations for the potential handing of the PFCS waste material in at the Sellafield Ltd site. One ROV was configured as a standard off the shelf unit. The second incorporated a sophisticated control system with a “teach and repeat” capability which potentially reduces operator fatigue, at the expense of increased complexity. These alternative options gave the Sellafield Ltd operators an early indication of what is available and enabled their initial thoughts and comments to be taken on by the team.
There are thousands of these ROVs in use in other industry sectors around the world and as a consequence a wide variety of end effectors has been developed. The end effectors can be rapidly exchanged to handle the waste material inside the silo, which may have become compacted over time. If required, the ROV can size reduce the waste prior to its removal from the compartment.
The demonstrations at NES’ facilities were attended by visitors from the Nuclear Decommissioning Authority (NDA) and Sellafield Ltd including Jack DeVine Chief Decommissioning Officer and Steve Bostock Head of the Spend Fuel Management Directorate. These were accompanied by a number of the PFCS operators who were able to take the opportunity of gaining hands on experience under the safety supervision of Callum Nelson, QHSE Coordinator for NES. Also in attendance were NES Chairman Tony Eckford and George Andrews NES Programme & Deputy Managing Director.
Jack DeVine, Sellafield Ltd’s Chief Decommissioning Officer, commented:
“A bridge has been crossed in terms of time, safety, and commercially available equipment allowing us to confront real material sooner to prevent future delays.”
The Sellafield Ltd host John Eldridge, Principal Engineer Spent Fuel Management, commented:
“We were delighted by the interest shown in our demonstrations and in particular the enthusiasm shown by the PFCS operators for this potential approach. All without exception were asking to continue to be directly involved with any future development of the concept in NES. We really appreciate the rapid response to our request to NES, Cavendish Nuclear and others enabling a quick, efficient and safe mobilisation. “