- Site: Dungeness B
- IR number: 20-067
- Date: October 2020
- LC numbers: 22, 28
Executive summary
Purpose of Intervention
The primary purpose of this intervention was to:
- Undertake a sampled inspection of a safety circuit related control and instrumentation (C&I) equipment in support of an Office for Nuclear Regulation (ONR) Operating Facilities Division (OFD) initiative to assess EDF Energy Nuclear Generation Limited (EDF NGL) Dungeness B (DNB) nuclear power station’s readiness to return to service (RTS) following a prolonged outage;
- Undertake an inspection of the new automatic boiler emergency depressurisation (AutoBED) valve system equipment in support of ONR’s C&I assessment of the associated engineering change (EC).
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:
- The general physical condition of station transformers 21, 22 and 23 on behalf of ONR Operating Reactors (OR) Electrical Engineering specialist nuclear safety inspectors who were undertaking associated reactor (R) 21 statutory outage deferral and boiler tube leak (BTL) EC assessment work;
- Automatic boiler depressurisation system (ABDS) installation work in support of ONR’s C&I assessment of the associated EC.
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:
- LC 22 – Modifications or experiment on existing plant;
- LC 28 – Examination, inspection, maintenance and testing (EIMT).
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.