Office for Nuclear Regulation

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System Based Inspection 05 - Auxiliary Systems: Containment Access (KL) and Local Leak Rate Test System(GP)

Executive summary

Purpose of intervention

The purpose of this intervention was to undertake Licence Condition (LC) compliance inspections at EDF Nuclear Generation Limited's (NGL's) Sizewell B power station in line with the planned inspection programme contained in the Sizewell B Integrated Intervention Strategy (IIS). The compliance inspections were carried out by the nominated Site Inspector and a Mechanical Specialist Inspector.

Interventions carried out by ONR

As part of this intervention, we carried out a safety case based system inspection against the Containment Access and Leak Rate Test Systems. Through examination of this system we performed compliance inspections against Licence Conditions:

Our inspections were based on sampling the implementation of the arrangements in place against each licence condition. We held pre- and post- inspection meetings with the site management where the inspection agenda was discussed and contents of this report were communicated.

The opportunity was also taken whilst on site to undertake the following meetings:

Explanation of judgement if safety system not judged to be adequate.

The safety system was judged to be adequate following this inspection.

Key findings, Inspector's opinions and reasons for judgements made

From a LC10 perspective, from the evidence sampled during this inspection, we consider that the operational and maintenance requirements for training have been adequately implemented, warranting an associated IIS rating of 3 (Adequate).

From an LC23 perspective, from the evidence sampled during this inspection we consider the safety case and operating rules for the mechanical systems selected to be both adequate, in terms of content, and adequately implemented, warranting an associated IIS rating of 2 (Good) .

From an LC24 perspective, from the evidence sampled during this inspection we considered the operating instructions for the mechanical systems selected to be both adequate, in terms of content, and adequately implemented, warranting an associated IIS rating of 3 (Adequate).

From an LC28 perspective, we are satisfied that the arrangements sampled for the systems are adequate to ensure that the plant meets its nuclear safety requirements as set out in the plant safety case. During the plant inspection, we considered that the overall condition of the plant was a good indication that the maintenance regimes were being adequately implemented, warranting an associated IIS rating of 3 (Adequate).

Based on the sampling undertaken, we are satisfied that whilst many of the components within system GP and KL have the potential to affect safety, they do not fall into the scope of LC27. This judgement is on the basis that the components are all passive in nature and do not therefore act in response to a fault to prevent or mitigate a radiological consequence. We have therefore not rated LC27.

From an LC34 perspective, from the evidence sampled during this inspection we consider that containment is limited to reactor pressure vessel and the in-containment monitoring equipment and therefore outwith of this inspection. In our judgement, the Access System and Integrated Leak Rate Test System do not form part of the LC34 boundary. I have therefore not rated against LC34.

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

Conclusion of intervention

After considering all the evidence witnessed during each of the sample inspections undertaken against LCs 10, 23, 24, and 28 we consider that the safety case system inspection of the Access System and Integrated Leak Rate Test System confirmed they met the requirements of the safety case and are adequate.

No issues were raised by ONR through this intervention; corrective actions recorded under the Licensee's arrangements will be monitored by ONR on a routine basis.