Office for Nuclear Regulation

Dungeness B Planned Intervention

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 Integrated Intervention Strategy (IIS) for the Civil Nuclear Reactor Programme (CNRP) of the Office for Nuclear Regulation (ONR).

The intervention included a system based inspection (SBI) of emergency equipment 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 control and instrumentation specialist.

Interventions Carried Out by ONR

The key interventions during the emergency equipment system based inspection were for licence compliance covering the following licence conditions (LC):

In addition an inspection was completed that was started during the site inspector’s previous intervention at the site, covering:

Explanation of Judgement if Safety System Not Judged to be Adequate

During the inspection we found that the majority of the implementation of the safety case was adequate.  However, we have placed a number of actions on the Station to resolve shortfalls.  The most significant of these, in terms of determining the adequacy, were those associated with the condition of the Emergency Plume Gamma Monitoring System (EPGMS) and faulty equipment in the Alternative Indications Centre (AIC).  Parts of the EPGMS would be rendered inoperable in some fault conditions, especially those leading to a loss of power supply to the system, and hence it would not meet its design requirements. For the AIC, the staff within it would not be able to contact staff on the site directly and plant faults might not be detected when operating from it.  We therefore judged that the ability to respond to emergencies may be impaired by the condition of these two systems and hence that the systems were not adequate.

The systems are of a relatively low safety significance and are only required in an emergency.  Furthermore, the site has accepted actions to put forward its plans for restoring the functionality of the systems and hence we do not propose to take any regulatory action at this stage.  The site inspector will follow these up at his next visit to site and will consider the adequacy of the site’s proposals.

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

For LC 10, we inspected the training of staff involved in operating or maintaining emergency equipment.  We judged that the training was appropriate.  We found that all had their training marked as up to date, although we noted that some of this was through an assimilation process rather than completing explicit training.  Whilst we were uneasy about how often this was used, we had no evidence that it was not acceptable.  Overall, we judged the training to be adequate and hence assigned an IIS rating of 3.

For LC 23, we inspected compliance with the technical specifications relevant to the emergency equipment.  We did not find any evidence of non-compliance, but did note that the Licensee was unable to demonstrate positive compliance in a limited number of areas.  We agreed actions to improve this.  Since we did not identify any areas where the Licensee was not compliant, we judged that compliance with LC 23 was adequate and hence assigned an IIS rating of 3.

For LC 24, we reviewed the content of two operating instructions for emergency equipment and witnessed a walkthrough of one of them. We judged these to be adequate and hence assigned an IIS rating of 3.

No safety mechanisms, devices or circuits were identified within the systems included in the SBI.  Whilst the systems inspected did have safety related functionality their safety significance was low and there were alternative arrangements to maintain the necessary monitoring functionality.  We therefore judged that LC 27 was not applicable to these systems.

For LC 28, we inspected 4 items within the maintenance schedule to ensure that they had been completed within the maintenance interval and 5 further items where we inspected the detailed records of completion of the maintenance.  Whilst we found that all of the maintenance had been completed within the required intervals we identified shortfalls with the records and inconsistencies in the instructions for some of them.  These are known problems at Dungeness B and work is in hand to improve the position.  We judged that there would be no benefit in placing additional actions on the Station.  We judged that maintenance of these systems was below standard and hence assigned an IIS rating of 4.

The EPGMS provides functionality to detect the release of radioactive material at the site boundary. This system was not considered to provide functionality with regards to LC34 as it was not associated with the local detection of leakage or escape of radioactive material. The other systems included in the SBI do not contain radioactive material or radioactive waste so LC34 is not applicable to these systems.

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.  For the majority of the systems covered by the SBI, we found the plant condition to be acceptable.  However, as noted above, we found that faults in the EPGMS and AIC impacted on their functionality.

During the SBI, we identified five 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 for most systems, but not for two of them.  The majority of the compliance inspections showed adequate compliance.  For maintenance, however, we judged compliance to be below standard.  Overall, we judged that the emergency equipment was not adequate, mainly due to the equipment faults.

For LC 2, I, the site inspector, completed an inspection of marking of the site boundary that had been started during my previous visit with a security inspector.  Whilst the majority of the marking was consistent with the site’s arrangements, I found a number of shortfalls in the arrangements themselves and their implementation.  I therefore agreed actions with the Station to resolve these.  I judged that compliance was below standard and assigned an IIS rating of 4.

In relation to the other activities undertaken in this intervention, no key findings arose.

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.