Office for Nuclear Regulation

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PSR2 External & Internal Hazards

Executive summary

Purpose of intervention

The purpose of this site visit was to carry out a plant walkdown to become more familiar with Sizewell B (SZB) site for the purpose of the SZB periodic safety review 2 (PSR2) assessment being carried out by ONR and to look at areas of interest following the Level 4 External Hazards meeting on the 4th June 2014. It also provided an opportunity to look at the observations raised by EDF Nuclear Generation Limited (EDF-NGL) during their PSR2 along with further discussions on technical areas.

In 2012 issue 997 was raised following an internal flooding event at SZB, (Report ONR-SZB-IR-12-025 TRIM Ref: 2012/342040). This issue (997) remains open and will be addressed by this PSR2. This intervention provided a follow up on this event to ensure that actions are being implemented as part of this PSR2.

Interventions Carried Out by ONR

This intervention at SZB covered the following matters:

A Site Walkdown for familiarisation and to look at areas specific to Internal and External Hazards.

Provision of an update by EDF-NGL on the SZB PSR2 relating specifically to External & Internal Hazards.

Facilitate discussions on technical areas pertaining to External Hazards & Internal Hazards along with any comments following the walkdown.

Follow up on the 2012 internal flooding event and the progress on actions relating to this and PSR2.

Explanation of Judgement if Safety System Not Judged to be Adequate


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

The walkdown focused on internal and external hazard issues. There were no issues of significant regulatory concern raised during this walkdown. Some minor safety issues will be passed to the ONR site inspector. Overall the state of the plant observed was adequate.

One existing issue (997) relating to Fukushima work is relevant to this intervention and will be addressed by ONR's assessment of the SZB PSR2 work. The licensee is going to update their previous response to the 2012 ONR letter also providing responses to the queries discussed in this intervention. Issue 997 will be updated to capture this action and subsequent information received.

The licensee agreed to provide information and clarification on the flood protection classification of doors along with cable and pipe penetrations. Information will also be provided on how the safety case deals with category 2 plant positioned over other category 2 plant. Issue 2616 has been raised to record these actions.

Conclusion of Intervention

The site visit enabled a familiarisation for ONR inspectors with the site and also facilitated some good technical discussions. Overall the state of the plant observed was satisfactory.