Office for Nuclear Regulation

LC34 inspection of the Spent Fuel Pond

Executive summary

Purpose of Intervention

The purpose of this intervention was to undertake a planned licence condition (LC) compliance inspection at EDF Nuclear Generation Limited’s (NGL’s) Dungeness B power station in line with the relevant site inspection plan. The inspection was undertaken remotely by a project inspector due to constraints imposed by the ongoing Covid-19 pandemic. The focus of this inspection was the fuel pond; to confirm, on a sampling basis, the licensee was implementing its compliance arrangements for LC34 (Leakage and escape of radioactive material and radioactive waste). 

Interventions carried out by ONR

The compliance inspection of the fuel pond was conducted against the following LC:

LC34: Leakage and escape of radioactive material and radioactive waste

The fuel pond contains radioactive material.  On a sampling basis I examined how the licensee implemented its arrangements to identify barriers to leakage and escape of radioactive material, how it assured itself of the integrity of these barriers, and how leakage and escape would be detected.  The scope of the inspection included the fuel pond structure, and excluded the in-pond mechanical handling equipment and pond water treatment plant (PWTP).  No plant walk-down of the fuel pond was conducted as this inspection was undertaken remotely. 

The intervention was performed in line with ONR's guidance requirements (as described in our technical inspection guides) in the areas inspected.

Explanation of judgement if safety system not judged to be adequate

This was not a system based inspection.

Key findings, inspector's opinions and reasons for judgements made

I am satisfied the licensee is  complying with its LC34 arrangements which require barriers to leakage and escape to be identified and their integrity assessed, based on sampling inspection.  I am satisfied the level detectors which play an important role in detecting failure of these barriers are in place and in working order, based on sampling a range of inspection and maintenance records.  I sampled the most recent report of the Dungeness B ground water monitoring programme, and am satisfied any significant radioactive leak from the fuel pond would be detected by the station. 

I judged that maintenance requirements for the means of detecting leaks from the fuel pond are not derived from the safety case via appropriate safety classification schemes and I identified some weaknesses in the maintenance being undertaken.  However, the licensee has a comprehensive inspection and monitoring programme in place for the fuel pond, which together with operating limits and conditions that prevent temperature transients within the concrete structure builds confidence in the integrity of the fuel pond.  Based on my sampling inspection, I consider the Dungeness B fuel pond to be well designed, well constructed and well maintained, and subject to a more onerous surveillance regime than other similar fuel ponds. 

Taking this into account, I do not consider it proportionate to require the licensee to update its safety case to include safety classification that can be used to derive maintenance requirements for the means of leak detection from the fuel pond. 

I found it difficult to establish whether the licensee is identifying, reporting and repairing radioactive leaks in a timely manner, in accordance with its LC34 arrangements.  I brought my inspection findings and advice to the attention of the licensee’s LC34 arrangements owner’s attention as some of the difficulties stem from the tools available to the licensee to comply with the arrangements, rather than that the arrangements are not being complied with. 

During the inspection I provided advice to the licensee to help it to address the weaknesses I identified, which were relatively minor.  This was positively received.  I raised two regulatory issues to follow up minor compliance shortfalls.

I raised a number of observations with the licensee during the inspection, which the licensee received positively and will action.  I will share these with the site inspectors to ensure ONR oversight through the site inspector’s routine interactions with the station.

Conclusion of intervention

Based on my sample, in my opinion the licensee is meeting its legal requirements under LC34 and therefore assigned a rating of green (no formal action) in accordance with the ONR inspection rating guide.  I raised two regulatory issues to address minor compliance shortfalls.

In my opinion, conducting this inspection of the fuel pond remotely did not limit the scope or depth of sampling, and I was able to engage with the licensee and view evidence such as work instructions and inspection findings remotely (over Skype).  The only impact was that I could not undertake a plant walk down; this was not considered a significant issue.