Office for Nuclear Regulation

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Dungeness B - Planned intervention

Executive summary

Purpose of intervention

This is 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).

Interventions Carried Out by ONR

The intervention included compliance inspection against nuclear site Licence Conditions (LC) 22 - modification or experiment on existing plant. At the time of this intervention, DNB Reactor 21 was on its periodic shutdown (also known as its statutory outage). Because of this, the theme of this inspection was outage modifications.

The intervention included observation of the licensee internal regulator's outage Rapid Trend Review (RTR). The primary aim of the outage RTR is to identify performance shortfalls in the early stages of a periodic shutdown to enable station management to reduce or eliminate undesirable behaviours and conditions that could have an adverse impact on outage success.

The intervention included planned information gathering, part of which was a visit of the ONR Chair and the ONR Chief Executive Officer (CEO) during the ongoing periodic shutdown of Reactor 21.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable.

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

In relation to the LC22 compliance inspection I (the DNB site inspector) inspected outage modifications since the Reactor 21 periodic shutdown had recently started. I sampled fire safety improvements in the Gas Circulator (GC) halls and focussed in particular on the GC Back Up Seal Oil Accumulator (BUSOA) oil flow restriction system. Following on from the Reactor 22 fire on 23 November 2009 I consider that good use has been made of LC22 to manage fire safety improvements. Focusing specifically on the GC BUSOA oil flow restriction system, LC22 has been used during the identification of the need for this fire safety improvement and the establishment of its required safety functions. I am satisfied that an adequate strategy has been put in place to commission each of the Reactor 21 GC BUSOA oil flow restriction systems to ensure that they will fulfil their safety functions and that this strategy is being adequately implemented via LC22 arrangements. Taking all these factors into account I assigned an Integrated Intervention Strategy (IIS) Rating of 2 (good standard) to LC22.

In relation to the licensee internal regulator's outage RTR we (Reactor 21 periodic shutdown project inspector and DNB site inspector) observed various aspects of the process. On the basis of our observations, we considered that the outage RTR met its primary aim of identifying performance shortfalls in the early stages of a periodic shutdown. This should enable station management to reduce or eliminate undesirable behaviours and conditions, which could have an adverse impact on outage success.

In relation to the visit of the ONR Chair and the ONR CEO, their plant tour included parts of the flood wall around the entire site and local flood protection, since completion of this was a prerequisite for depressurising Reactor 21 early in its periodic shutdown. The ONR Chair wrote to the DNB Station Director after the visit thanking him for the opportunity to visit during a very busy period for the station.

The licence conditions were inspected against ONR's published guidance requirements (as described in our technical inspection guides).

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.