Office for Nuclear Regulation

Planned inspection, SBI 60Hz Nuclear System

Executive summary

Purpose of Intervention

The Office for Nuclear Regulation (ONR) undertakes all interactions at the Devonport Licensed Site (operated by Devonport Royal Dockyard Limited (DRDL)), in accordance with ONR’s integrated intervention strategy (IIS).

The purpose of this intervention was for ONR to conduct a system based inspection, to examine whether the Licensee’s safety case claims, relating to the 60Hz Nuclear System have been adequately implemented.

This intervention was undertaken remotely, by ONR electrical specialist inspectors.  A member of the Licensee’s Independent Nuclear Oversight team supported the intervention and conducted certain site-based activities as required.  The Defence Nuclear Safety Regulator (DNSR) also participated in the intervention.

Interventions Carried Out by ONR

For this intervention, ONR performed a planned safety case informed system based inspection of the safety systems and circuits associated with the 60Hz Nuclear System, to judge performance against the safety functional requirements and examine the adequacy of implementation of the safety case.  The following systems and components were sampled by this intervention:

Through sampled examination of the arrangements made for the 60Hz Nuclear System safety systems and components, ONR performed compliance inspections against the following licence conditions (LCs) where applicable:

The intervention was performed in line with ONR's guidance requirements (as described in our technical inspection guides) in the areas inspected.

Explanation of Judgement if Safety System Not Judged to be Adequate

The Licensee has demonstrated that the safety systems and circuits sampled in relation to the 60Hz Nuclear System are able to fulfil their safety functional requirements adequately, in line with the safety case.

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

Based on the specific areas sampled during the course of the inspection, I found that overall, the Licensee has adequate arrangements in place to ensure that the safety systems and circuits associated with the 60Hz Nuclear System are operated and maintained in accordance with the appropriate safety cases and safety functional requirements.  Ratings for each of the LCs are as follows:

Conclusion of Intervention

From the evidence sampled during the inspection, I consider that overall, the safety systems and circuits associated with the 60Hz Nuclear System meet the claims in the relevant safety cases and that there are no findings from this inspection that could significantly undermine nuclear safety.

Specific shortfalls against ONR technical inspection guide NS-INSP-GD-027 expectations were recorded in relation to ensuring that equipment performing a safety function is in good working order.  I judged, that although specific shortfalls have been identified with respect to LC 27, within the context of the overall system based inspection, no significant shortfalls in the delivery of nuclear safety were identified that would prevent the 60Hz Nuclear System from providing its’ safety function if called upon.

A specific shortfall against ONR technical inspection guide NS-INSP-GD-028 expectations was recorded in relation to ensuring that plant and equipment is maintained in accordance with a maintenance schedule.  I judged that although a specific shortfall has been identified with respect to LC28, within the context of the overall system based inspection, no significant shortfalls in the delivery of nuclear safety were identified that would prevent the 60Hz Nuclear System from providing its’ safety function if called upon.

An ONR Regulatory Issue has been raised to track progress of the identified shortfalls.  ONR inspectors will conduct further engagements with the Licensee during the progression of the regulatory issue.  No additional regulatory action is needed over and above ONR’s planned interventions as set out in the ONR integrated intervention strategy plan.