Office for Nuclear Regulation

Control & Instrumentation (C&I) Return To Service (RTS) inspections

Executive summary

Purpose of Intervention

The primary purpose of this intervention was to:

In addition to the above, I also inspected the following on behalf other ONR nuclear safety inspectors who were unable to visit DNB due to COVID-19 restrictions:

Interventions Carried Out by ONR

This intervention was undertaken by an ONR C&I specialist nuclear safety inspector and involved undertaking plant walkdowns and holding discussions with relevant stakeholders in accordance ONR’s and EDF NGL’s COVID-19 secure arrangements.

The primary purpose aspects of this intervention were undertaken in relation to the following Licence Conditions (LCs), which are applicable provisions of the Energy Act 2013:

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

Not applicable.

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

During the inspection that I undertook of a sample of C&I equipment cubicles / panels and equipment associated with several R21 and R22 safety circuit systems, I did not identify any significant signs of age-related degradation with respect to the items I examined.

I also met with the relevant system health engineers (SHEs) to discuss the health of the C&I equipment and their RTS preparations.

Based on the findings of this aspect of the intervention I have assigned an integrated intervention strategy (IIS) rating of Green to LC 28 (EIMT) compliance.

I reviewed the new AutoBED valve system control cubicles and associated cabling installation work, I was content that adequate installation activities have been undertaken. I also considered the cubicles to have been well manufactured.

I also met the chairperson of the test and commissioning panel (T&CP) and discussed the oversight that the panel had of the AutoBED valve system installation, test and commissioning work. As a result of this discussion, I am content that the T&CP did have adequate oversight of this work.

Based on the findings of this aspect of the intervention I have assigned an IIS rating of Green to LC 22 (modification or experiment on existing plant) compliance.

During the intervention I reviewed the work that had / was being undertaken in relation to the remediation of station transformer corrosion and ABDS installation. This was undertaken on behalf of other ONR specialist nuclear safety inspectors.

I have raised three regulatory issues during the intervention, which I consider to be minor shortfalls and will monitor them through to resolution as part of normal regulatory business..

Conclusion of Intervention

Based on the sample of safety circuit equipment that I visually inspected, and the information provided to me during this aspect of the intervention, I consider that adequate C&I equipment EMIT activities are being undertaken by DNB. I have therefore assigned an intervention rating of Green to LC 28 (EIMT) compliance.

Based on the sample of the AutoBED valve system equipment that I inspected, and the information provided to me during this aspect of the intervention, it appears that adequate installation activities have been undertaken in relation to this system. I have therefore assigned an IIS rating of Green to LC 22 (modification or experiment on existing plant) compliance.

During this intervention I did not identify any issues that pose an immediate significant threat to nuclear safety. Nor did I identify any C&I equipment related issue that would prevent ONR providing a Consent for DNB to RTS.