Office for Nuclear Regulation

Dungeness B - Control and Instrumentation (C&I) Readiness Inspection

Executive summary

Purpose of Intervention

This intervention record covers a readiness inspection performed as part of an ONR Operating Facilities Division (OFD) initiative to inspect EDF Energy Nuclear Generation Ltd’s (NGL) Dungeness B (DNB) nuclear power station reactors’ readiness to return to service following the extended outage as a result of the station’s event recovery due to corrosion. The focus of this inspection was to inspect a sample of activity conducted since the ONR Control and Instrumentation (C&I) inspection of R22 (23-24/10/2018), and to review C&I related commissioning and maintenance activities. I also assessed the impact of the extended outage on C&I activities, SQEP levels and the behaviour of C&I personnel on site.

Interventions Carried Out by ONR

My inspection was undertaken in support of ONR’s overall approach to return to service of the DNB reactors, which is to consider and if appropriate grant a ‘Consent’ to restart.

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 system based inspection was undertaken.

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

In general, there was evidence that the systems sampled during my inspection were being looked after. However, I did observe more debris that I would have expected on the turbine hall floor. This was reported to senior management who informed me that their plan was to address this prior to return to service.

Regarding Licence Condition (LC) 22 - Modification or experiment on existing plant, I inspected arrangements in place for the installation and commissioning of SS5 valve instrumentation and boiler temperature instrumentation. At the time of my inspection the engineering changes, installation and commissioning of these systems were incomplete. Station were not able to say how the multiple channels of thermocouple data would be presented to the operators for recording during their shiftly checks. I advised station that they should consider how thermocouple data will be presented to the operators for recording during surveillance activity and to clarify the methodology for capturing boiler thermocouple data within the station’s arrangements for maintenance and testing. Station management committed to addressing these issues. I considered that the equipment installed at the time of my inspection had been carried out neatly in a difficult working environment. I have commented to station management that the timescales for completion of the work look ambitious. Based on the findings of my inspection, I have assigned an integrated intervention strategy (IIS) rating of ‘Green, no formal action’ to LC22.

Regarding LC28 I consider suitable and sufficient arrangements are in place to manage the examination, inspection, maintenance and testing (EIMT) of C&I aspects of the fuelling machine, gas circulators, post trip interlock system and the reactor protection system at DNB. At the time of my inspection maintenance schedule tests were up to date. However, it is noted that there remains a significant number of C&I related EIMT activities that are not complete due to them requiring particular plant conditions for completion. In addition, there have been a significant number of plant modifications over the extended outage at DNB and, as a result of operator’s relatively lower levels of recent operational experience, I consider there is a risk that operations will be challenged if proactive management arrangements are not put in place to manage this workload during return to service. I consider that suitable and sufficient arrangements are in place to manage the configuration of the post trip interlock system and reactor protection systems. Vulnerabilities have been identified and plans are in place to address these. I consider that more effort is necessary to complete system hand over documents. Based on the findings of our inspection, I have assigned an IIS rating of Green to LC28.

I witnessed a good attitude towards nuclear safety and I did not witness any poor behaviours during this inspection.

On the basis of my sample inspection, I found that relevant good practice was met with only the minor shortfalls identified when compared with relevant guidance.

Conclusion of Intervention

On the basis of my sample inspection of the C&I aspects of this readiness inspection intervention at DNB, no issues were identified that would prevent my support of ONR’s overall approach to Consent to grant return to service of the DNB reactors on C&I grounds.