Office for Nuclear Regulation

Graphite Mechanical Engineering compliance intervention

Executive summary

Purpose of Intervention

This intervention was carried out to gather evidence to support Office for Nuclear Regulation (ONR) permissioning decision under Licence Condition (LC) 30: Periodic Shutdown, regarding start-up of EDF Energy Nuclear Generation Limited (NGL) Torness Power Station Reactor 1 (R1) following its 2021 periodic shutdown.

Interventions Carried Out by ONR

LC 30, paragraph (1) states that for the purposes of enabling Examination, Inspection, Maintenance and Testing (EIMT) work, Nuclear Site licensee shall shutdown plant in accordance with requirements set out in the plant Maintenance Schedule (MS) established under LC 28: EIMT.

The scope and regulatory objectives of this mechanical engineering intervention were:

Explanation of Judgement if Safety System Not Judged to be Adequate

No system-based intervention was undertaken, this section is not applicable.

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

From evidence gathered, focused on Station’s MS arrangements for periodic shutdown work for mechanical aspects of the following safety systems:

Only minor compliance issues were identified in procedures and paperwork records for Gas Circulator refurbishment.  These matters were brought to the attention of the Torness Power Station’s Reactor Systems Group Head.  Station confirmed updates to Rotor Balance procedure and coaching of maintenance personnel would be undertaken.

Whilst carrying out this intervention Station reported that Gas Circulator (GC) machine 23, located in R1 position 1CX1, had experienced a high temperature excursion on the non-drive end bearing.  Station replaced this GC with a refurbished spare machine, given potential damage to white metal bearing.

This matter was discussed with the ONR Project Inspector coordinating the Torness R1 2021 periodic shutdown.  The Mechanical Engineering Inspector didn’t consider this matter was a start-up issue, given Station had replaced GC machine 23.  However, considered NGL needed to establish the cause of this event and present its findings at the ONR and NGL R1 start-up meeting.

Conclusion of Intervention

Based on intervention findings, the Inspector considers Torness Power Station has complied with its periodic shutdown MS requirements.  Specified work being undertaken by SQEP with an appropriate level of supervision and quality requirements.  No matters were identified which were considered to challenge start-up of R1 or impacting on its safe operation until its next periodic shutdown in January 2024.

From a Mechanical Engineering perspective, the Inspector recommends ONR give its consent to allow Torness R1 to be started up following its 2021 periodic shutdown.