Office for Nuclear Regulation

Dungeness B planned inspection

Executive summary

Purpose of intervention

This was a planned inspection at EDF Energy Nuclear Generation (NGL) 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 auxiliary cooling systems to demonstrate compliance with the safety cases for these systems.  This inspection was performed by the ONR nominated site inspector with technical support provided by a structural integrity specialist.

Interventions Carried Out by ONR

The key interventions during the auxiliary cooling systems system based inspection were for licence compliance covering the following licence conditions (LC):

The main activity for the remainder of the intervention was the station’s annual review of safety.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable as the system was judged to be adequate.

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

For LC 10, based on a sample review of the training documents and work order cards for staff involved in operation and maintenance of the auxiliary cooling systems, we noted that the licensee had an adequate process for ensuring that the staff were suitably trained.  The licensee demonstrated that the majority of staff that we selected who operate, maintain inspect or test plant had suitable training.  However, in one case testing had been signed off by a technician who had not completed training.  This highlighted a shortfall in the site’s arrangements, which it has taken an action to address.  In light of this, we judged compliance with LC10 to be below standard, IIS rating 4.

For LC 23, a sample of the records for compliance with the site’s technical specifications over the previous two months was inspected.  This showed that the site had been compliant and hence we judged compliance with LC 23 to be adequate, IIS rating 3.

For LC 24, the licensee demonstrated that adequate operating instructions were in place to reflect the requirements of the safety.  Two operations were witnessed and we judged that these demonstrated that the plant was operated competently.  In light of this, we judged compliance with LC24 to be adequate, IIS rating 3.

For LC 27, we identified essential cooling water system pumps autostart to be safety mechanisms devices and circuits as required by the licence condition.  Based on the information on operating rule compliance and following discussions with the licensee, the licensee demonstrated that sufficient safety mechanisms, devices and circuits were available. In light of this, we judged compliance with LC27 to be adequate, IIS rating 3.

For LC 28, records for inspections in the maintenance schedule for the auxiliary cooling systems were inspected.  Generally the site provided evidence that plant had been inspected, examined, maintained or tested within the time interval in the maintenance schedule.  Shortfalls were identified in following up on the results of inspections to demonstrate that results that appeared to be anomalous and three actions were placed to address these.  In light of this, we judged compliance with LC28 to be below standard, IIS rating 4. 

We discussed the role of the auxiliary cooling systems and their potential role within LC34. The conclusion was that the systems do not contribute significantly to preventing the leakage and escape of radioactive materials and radioactive waste, therefore LC34 was not considered any further.

Finally, the system based inspection requires an assessment of the plant condition, which was based on discussions with the licensee on its own assessment and a walkdown of the plant.  The licensee had identified a number of areas where the plant needed to be improved.  The systems generally reflected the state of the plant described by the licensee, although some minor areas for improvement were identified.  Overall the plant condition was judged to be acceptable.

During the SBI, we identified four actions where we judged the performance to be below standard.  These have been recorded in an ONR issue to ensure that the actions are suitably discharged.

As noted above, the plant condition was judged to be acceptable and the majority of the compliance inspections showed adequate compliance.  For two licence conditions, however, we judged compliance to be below standard and found four deficiencies for which we placed actions on the site.  We assessed the significance of these shortfalls and judged that they did not significantly undermine the ability of the plant to meet the requirements of the safety case.  Overall, we therefore judged that the cooling systems were adequate.

ONR attended the site’s annual review of safety (ARoS) meeting, where the site presented its intentions for the forthcoming year.  We had no major issues with these.

The site inspector attended a Site Stakeholder Group (SSG) meeting.

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.