Magnox Ltd Decommissioning: Chapelcross Ponds. Agreement to Retrieval of Empty Skips from Pond

Permission requested

Magnox Ltd has written to the Office for Nuclear Regulation (ONR) to request permission to retrieve redundant, empty skips from Pond 2, a fuel storage pond that now contains only various radioactive wastes and is being decommissioned. This work will constitute a modification to the processes on the plant, retrieval never having been carried out in this manner previously. The request was accompanied by a safety case for the proposed process.

Background

The skips to be retrieved are metal boxes that once held spent Magnox fuel elements. They have thereby become radioactive, but many fall within the UK’s definition of Low Level Waste (LLW) and so can be disposed of now, without further treatment. The permission would allow the LLW skips to be retrieved, monitored, bagged, and put into ordinary transport containers for temporary storage elsewhere on the Chapelcross site, to await transfer to a disposal site.

The main radiological fault that might arise is that a skip containing waste is brought out of the pond in error, exposing workers to high, unplanned radiation doses. There are no credible faults that would affect the public.

Assessment and inspection work carried out by ONR in consideration of this request

ONR’s assessment and inspection have concentrated on ensuring that the design of the equipment for this work, and the procedures by which it will be carried out, make the risk associated with the fault described above as low as is reasonably practicable.

Since ONR’s assessment began, Magnox Ltd had added more engineered safety measures to the design, thus reducing the reliance on procedural control. The process, improved in this way, has been assessed by ONR’s specialist in human factors, who concludes that it is now satisfactory. In addition, ONR has required Magnox Ltd to ensure that operators are fully trained in the new process.

Conclusions

ONR judges that LLW skips can now be safely retrieved from the pond and stored in the manner proposed.

Recommendation

Agreement to the retrieval should be given by issuing Licence Instrument 527.