Office for Nuclear Regulation

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Planned intervention including system based inspection

Executive summary

Purpose of intervention

This was a planned inspection at EDF Energy Nuclear Generation Ltd’s (NGL’s) Dungeness B (DNB) power station, undertaken as part of the planned intervention strategy for the Civil Nuclear Reactor Programme (CNRP) of the Office for Nuclear Regulation (ONR).

The intervention included a system based inspection of the heating and ventilation systems (H&V) to demonstrate compliance with the safety case for these systems.  This inspection was performed by the ONR nominated site inspector with technical support provided by an H&V specialist.

Interventions Carried Out by ONR

The key interventions during the H&V system based inspection were for licence compliance covering the following licence conditions (LC):

System based interventions usually include compliance with LC 27 (safety mechanisms, devices and circuits).  I judged that as the hazards associated with failure of the systems are relatively low, this should not be included in this intervention.  Hence the intervention only considers the five licence conditions above.

The interventions for other parts of the inspections were for licence compliance covering the following licence conditions:

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable as the H&V systems were found to be adequate.

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

For LC 10, I inspected the training for operation of the H&V systems and its implementation. I found that whilst the operating technicians had completed the required training, the on-the job training did not explicitly cover all of the operations for the system. I placed an action on the site to review and revise it’s on the job training and therefore judged this element of my inspection to be below standard and rated it through the Integrated Intervention Strategy (IIS) as 4.

For LC 23, I inspected the content and implementation of the technical specifications for H&V systems and concluded that they were adequate for compliance against LC 23.  I have therefore rated this element of my inspection through the IIS as 3.

For LC 24, I inspected the content and implementation of operating instructions and judged that there were adequate operating instructions in place and that the staff demonstrated an adequate knowledge of the plant operating requirements.  I found a discrepancy with instructions known as AORAs for the system and placed an action on the site to review this. I judged that this discrepancy was not significant and hence concluded that compliance with LC 24 for the H&V systems was adequate.  I have therefore rated this element of my inspection through the IIS as 3.

For LC 28, I inspected a sample of maintenance records for the H&V systems.  I found that the maintenance instructions referred to the appropriate procedures for the task and recorded historical data which in combination showed the plant items were appropriately maintained meeting the requirements of the safety case. Although I found that the filters in place were beyond their likely recommended service life in one system, this was a shortfall of recommended good practice and will be resolved before the system is next used. I therefore judged that maintenance was in accordance with the safety case and that compliance with LC 28 was adequate.  I have therefore rated this element of my inspection through the IIS as 3.

For LC 34, I judged that it was not credible for radioactive leakage from the H&V systems to occur and the site demonstrated adequate arrangements for waste routes in the event of contaminated filters. I judged that compliance against LC 34 for the H&V systems was adequate.  I have therefore rated this element of my inspection through the IIS as 3.

I judged that most of the H&V systems that I saw appeared to be in good condition, with the exception of some minor issues and the condition of the extract fan belts; which I judged needed replacing.  I placed an action on the site to replace belts that were not adequate and it agreed to do this on a short timescale.  I therefore judged the condition of the H&V systems to be adequate.  I have therefore rated this element of my inspection through the IIS as 3.

For the system based inspection of the H&V systems I had found that the overall condition of the plant was adequate and that with the exception of the licence compliance inspection for LC 10, compliance was adequate.  Balancing the results of the licence condition inspections, I judged that overall the inspections had demonstrated that the safety case had been implemented adequately.  I concluded that the system as a whole met the requirements of the safety case and was adequate.  I have raised an ONR Issue to address the minor shortfalls identified during the system based inspection, which identifies a number of actions for NGL to address.

For LC 11, the annual Emergency Arrangements Review Meeting was held during the intervention.  The meeting was a useful exchange of information and clearly identified the way forward on issues raised.  I have therefore rated the compliance with LC 11 as adequate.  I have therefore rated this element of my inspection through the IIS as 3.

For LC 30, the Outage Intentions Meeting was held to allow the site to present its intent for work during the Reactor 22 outage scheduled during 2015.  No significant issues arose during the meeting and I therefore assessed this as adequate for compliance with LC 30.  I have therefore rated this element of my inspection through the IIS as 3.

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

Conclusion of Intervention

From the evidence obtained during this intervention, no matters have been identified that are likely to have a significant impact on nuclear safety on the station at this time.  Therefore, no additional regulatory action arising from this visit is considered necessary at this time.