Office for Nuclear Regulation

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Dungeness B (DNB) power station, follow-up enquiries of reported events

Executive summary

Purpose of Intervention

The purpose of this intervention was to undertake a reactive Licence Condition (LC) compliance inspection at EDF Energy Nuclear Generation Limited (NGL) Dungeness B (DNB) Power Station in line with the planned inspection programme contained in the DNB Integrated Intervention Strategy (IIS) for 2019/20.

Interventions Carried Out by ONR

I undertook follow-up enquires into reportable events that have taken place at DNB. As part of the follow–up enquiries, I undertook reactive unplanned compliance inspections against LC7, 10, 23, 26, and 28.  The follow-up enquiries were supported by ONR specialist inspectors for human factors and leadership and management for safety.

The reportable events were:

The site inspector also held discussions with the station covering the following reported events regarding:

In addition, the site inspector also undertook routine engagements with the station’s safety representatives and leadership team to discuss ONR regulatory issues.

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

Not applicable: No safety system inspection was undertaken during this intervention.

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

The follow-up of the reported events for Tech Spec breaches of Technical Specification 7.1.1  identified that licence conditions LC7, 10, 23, 26 and 28 were applicable to this intervention and therefore rated then accordingly.

LC7 (Incidents on the site) The reporting of incidents at DNB is actively encouraged and was evident in the reporting of these events to ONR.  My examination of the station’s adverse condition investigations identified that it had undertaken sufficient investigations into the one of the events concerned and that the actions raised were appropriate. In light of these observations I concluded that a rating of Green is warranted.

LC10 (Training) , 23 (Operating rules), 26 (Control and supervision of operations & & 28(Examination, inspection, maintenance and testing) –

From ONR’s follow-up enquiries, I identified:

These all contributed to the entry of Tech Spec breaches for Technical Specification 7.1.1, which is specific to the reactor pressure vessel safety relief valves which are the principal barriers in preventing the reactor pressure vessel from over-pressurising.   I have therefore concluded that there were significant shortfalls within the licensee’s arrangements which in my opinion warrant a rating of Red for license conditions 10, 23, 26 and 28.

In light of the above, I will apply the enforcement management model (EMM) to determine the most appropriate enforcement action; the enforcement decision will be captured in a separate decision record.

My discussions with the station regarding the three other reported events were positive; I will await the station’s follow-up reports, I consider that no further follow-up is required for these particular events.

Nine regulatory issues were discussed that had been raised by the site inspector or previous site inspectors. I identified two regulatory issues that could be closed, one of which was a long standing issue that had a number of regulatory actions which had been completed with only one remaining. In light of this remaining action, I have raised a single regulatory issue to address this action and enable me to track the station’s progress.  For the remaining issues the station provided sufficient updates.

Conclusion of Intervention

I found that in relation to the unplanned LC7 compliance inspection I concluded that a rating of Green is warranted. For LC’s 10, 23, 26 and 28. I have concluded that there were significant shortfalls within the licensee’s arrangements which in my opinion warrant a rating of Red. I will therefore apply ONR’s enforcement management model to determine the most appropriate enforcement action; the enforcement decision will be captured in a separate decision record.