Office for Nuclear Regulation

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Readiness inspection of the new nitrogen storage and distribution system as part of the planned permissioning activity for the diverse hold-down project

Executive summary

Purpose of intervention

The primary purpose of the intervention was to conduct a readiness inspection of the new diverse hold-down (DHD) system at EDF Energy Nuclear Generation Limited’s (NGL’s) Hunterston B (HNB) power station. The aim of the inspection was to obtain evidence to inform the permissioning process that will consider the forthcoming request from the licensee of HNB to put the new DHD system into service. The work was carried out in line with the planned intervention programme contained in the Office for Nuclear Regulation (ONR) diverse shutdown system intervention project record.

Interventions Carried Out by ONR

The ONR HNB nominated site inspector and I, the DHD project inspector, carried out an inspection of the new DHD system at HNB and held meetings with appropriate members of the project team; commissioning team; and engineering team. The inspections were based on sampling the arrangements that are in place associated with the LC22 “modification or experiment on existing plant” and considered safety case requirements, commissioning, operating rules, operating instructions, plant component maintenance and examination, and staff training.

The ONR HNB nominated site inspector and a specialist inspector attended an information exchange meeting with the Principal Contractors of Western Link project. This was an introductory engagement to strengthen ONR’s confidence that NGL is exerting adequate control over contractor activities that have a direct interface and impact on the nuclear licensed site.

Explanation of Judgement if Safety System Not Judged to be Adequate

No system inspection was undertaken during this intervention.

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

We judged that from the evidence obtained during the meeting held with commissioning team members and the documents sampled the licensee has adequate oversight and control of the commissioning process; has an adequate process to identify and control novel or complex components or operations on the new DHD and has demonstrated links between the commissioning process and the nuclear safety case.

We judged that from the evidence obtained during the meeting held with project team members and the documents sampled the licensee has adequate control and oversight of the system handover process to station, and has an adequate process for safely putting the new DHD into service. We noted that the operating instructions sampled had benefited from specialist human factors input to strengthen configuration control.

We judged that from the evidence obtained during the meeting with engineering function members and the documents sampled the licensee has adequate control and oversight of technical queries, non-conformances and change requests associated with this project.

We judged that from the evidence obtained during the meeting with the training department and documents sampled that the licensee has adequate arrangements to train staff who will work on the DHD.

We are content that sufficient progress is being made in relation to the implementation of the modification under LC 22(1) for the introduction of the DHD system and have assigned an Integrated Intervention Strategy (IIS) rating of 3 (adequate) to this intervention.

The Western Link principal contractors – Scottish Power Transmission (SPT) provided useful background information in relation to the commercial and political motivation for the Western Link transmission connection between Hunterston and Deeside in North Wales. The new Hunterston East 400kV station will provide enhanced calculated reliability of Hunterston B’s grid connection. The project requires a temporary incursion onto the nuclear licensed site to enable connectivity with the existing 400kV station.  A small section of the outer boundary fencing will be replaced. This will involve several hundred contractors periodically operating on the licensed site over several months. NGL has committed to review the tenability of existing onsite and offsite emergency arrangements for contractor personnel operating in this manner.

SPT articulated the schedule of commissioning and load testing with commissioning of the Converter station currently due to commence in September 2016. I advised SPT and NGL that ONR do not currently intend to undertake any formal regulatory permissioning of the project.

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

Two topics were identified that we consider require further clarification and consider appropriate to be included within Independent Nuclear Assurance (the licensee’s internal regulator) concurrence inspection planned for January 2015. These are the audit trail for implementation of Licence Condition 28 arrangements and the basis of three safety function requirement parameters described in the safety case. I will follow up these topics as part of my routine interactions with members of the licensee’s DHD project team.

From the evidence obtained during our inspection, we are content that sufficient progress is being made in relation to the implementation of the modification under LC22(1) for the introduction of the DHD system and have not identified any shortfalls currently that would prevent ONR issuing an Agreement.

We judged that NGL has a mature and rigorous level of control and oversight of SPT activities in relation to the Western Link interface with the nuclear licensed site.