Office for Nuclear Regulation

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Oldbury nuclear licensed site planned system inspections and meetings

Executive summary

Purpose of intervention

I undertook a system inspection of Oldbury's pond ventilation system. The information gained will be of value for future regulation of the pond's post defuelling clean-up work that will: retrieve the intermediate level waste (ILW) stored in the pond and place it in a passively safe form using self-shielding containers; removal and disposal of low-level waste; and drain-down of the water.

I was updated on progress with ILW decommissioning programmes on the site.

Part of the inspection was undertaken as a joint inspection with the Environment Agency site regulator.

Interventions Carried Out by ONR

Oldbury provided a pond building ventilation plant description. The plant provides clean air to the pond building and removes airborne particulate if present before the air is recirculated or exhausted to atmosphere. There was a safety case requirement that the building environment was to be maintained at a negative pressure to ensure air did not leave the building unless it had been filtered. I visited the pond area and saw the ventilation ducts and the equipment used to ventilate the pond area and the changing rooms.

I discussed with Oldbury its plans for undertaking a periodic safety review and noted suitably qualified and experienced persons on the topics addressed (including knowing the particular circumstances on the site) needed to have their input into the review.

Oldbury brought me up to date on progress with the plans to remove waste items from the pond and other plans to make mobile intermediate level waste on the site passively safe.

Explanation of Judgement if Safety System Not Judged to be Adequate

The ventilation systems in the pond complex did not conform to the 1991 safety documentation I was given. In particular the inlet vent was not drawing air into the system and the change area was not at a higher pressure than the pond area. However, measurements undertaken by a ventilation expert the previous week demonstrated that air being drawn from the pond complex was passing through the high efficiency particulate air filter system before going up the stack. Also the work in the ponds did not involve moving higher activity waste from under the pond water. As a result I concluded that currently, there wasn't a threat to nuclear safety. However, I sought and received adequate assurance that the suitability of the ventilation for future waste management activities was being addressed and an adequate safety case will be in place before intermediate level waste is removed from the ponds.

Key Findings, Inspector's Opinions and Reasons for Judgements Made

I found no evidence that the safety case pressure drop operating rule for the change area and the pond area was verified. However, Oldbury had had the system pressure characteristics measured which showed that there was an adequate air flow towards the filters before the air was discharged to atmosphere via the stack. Oldbury will be making a new safety case for the ventilation plant in the pond complex before bulk intermediate level waste is removed from the building.

The health of the filters in the ventilation systems was checked regularly and the site was able to confirm that there was sufficient qualified staff to undertake operation, inspection and maintenance of the ventilation system and its filters. Magnox Ltd acknowledged a need to replace the expertise being lost as a result of the local ventilation expert resignation and was implementing actions to correct the situation.

I confirmed that the pond programme managers and the health physics experts were going to work together to provide a demonstration that the method used to remove the disused low level waste fuel skips from the pond, package them and transfer them out of the pond area, would balance the need to contain any airborne radioactivity within the ventilation system, minimise the radiation dose to workers, minimise the generation of secondary waste, and at the same time allow for egress from the pond building to move the skips to temporary storage elsewhere on site. As part of this process it would seem appropriate to enhance the monitoring process looking for radioactive contamination in and outside the egress routes for waste.

Conclusion of Intervention

Oldbury demonstrated to me that they would minimise the risks to the public, workers and the environment when working in the pond complex.

I was also satisfied that the waste management programmes were working closely with Oldbury staff to ensure the techniques applied to make the wastes passively safe met the specific circumstances present at the Oldbury site.