Office for Nuclear Regulation

Return to service readiness inspection

Executive summary

Purpose of Intervention

This intervention record covers a readiness inspection performed as part of an ONR Operating Facilities Division (OFD) initiative to inspect EDF Energy Nuclear Generation Ltd’s (NGL) Dungeness B (DNB) nuclear power station’s readiness to return to service as a result of the extended outage. The extended outage of both rectors is as a result of the station’s on-going event recoveries, regarding corrosion, steam main cracking and its boiler tube safety case.

The purpose of this ONR readiness inspection was to build regulatory confidence in the Licensee’s ability to adequately conduct activities which will ensure safe operation of the reactors at power. This is because the reactors have been shutdown for nearly a year and a half, there a significant number of new staff, and there have been a number of significant events eg including INES events, ONR Enforcement letters, as well as the station being in Enhanced Regulatory Attention. The Readiness Inspection will therefore determine, via sampling, the adequacy of the stations return to service preparations, the adequacy of relevant aspects of the Enhanced Regulatory Attention issues to allow return to service, and also include consideration of the INA return to service surveillance inspection findings, from December 2019.

Interventions Carried Out by ONR

Interventions were carried out by Mechanical Engineering, Electrical Engineering, C&I Engineering and Structural Integrity Inspectors, as well as a Project Inspector, over the period 13th to 17th January 2020. The inspections were overseen by the Nominated Site Inspector and by an ONR Regulatory Assurance Inspector.

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, no system based inspection was undertaken.

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

The ONR inspections were designed to complement the INA Readiness Surveillance carried out in December 2019. The INA Readiness Surveillance was considered to be a good inspection, with findings and actions which ONR support. ONR did not plan to repeat the surveillances carried out by INA, nor raise duplicate corrective actions.

Overall, ONR found that Dungeness B have applied an analytical process to determine steps needed to restore operational focus and mindset, as a result of the extended period of shutdown.

Based on ONR sampling, overall, the scope of station’s readiness programme and level of engagement were encouraging, particularly in the Operations Department. However, levels of engagement within the Engineering Department appeared to the inspectors to be less consistent.

Interventions have resulted in green ratings against  LC10 (Training), LC12 (Duly Authorised Personnel), LC17 (Management Arrangements), LC26 (Control and Supervision) and LC28 (Examination, Inspection, Maintenance and Testing). There were a range of minor shortfalls noted against expectations, with three Regulatory Issues raised. Noting the purpose of the inspection was to judge readiness, ONR advise not to read too much into the License Ratings. It is more relevant to consider the cumulative impact of observations.


ONR observed the implementation of  innovative solutions to improve their plant, processes, and engagement of their teams. ONR consider these innovations to be encouraging, but they will require leadership support and reinforcement over a sustained period. ONR’s observations suggest that greater focus may be required in frontline leadership and field supervision e.g. procedural compliance.


Plant conditions need to be in a state which supports excellence in Operations, Maintenance etc. This is not the case currently in all plant areas (for example the Turbine Hall, the 62’ level of the Reactor Controlled Area).


Indicators suggest that the station is behind other stations in implementation of EdF Energy Nuclear Generation Limited fleet initiatives, for example, Site Excellence, defect re-date processes,  laying out “Green Route” safe walkways, However, ONR perceive that  these areas will be progressively adopted as the station moves forwards into routine operations.

Conclusions of Intervention

The interventions carried out assigned ratings of Green, ie meets minimum legal requirements, against LC10, 17, 22, 26 and 28, with three Regulatory Issues being raised.

ONR observed the implementation of innovative solutions to improve plant, processes, and engagement of teams. ONR consider these innovations were encouraging, but they will require station leadership support and reinforcement over a sustained period.

On the basis of the interventions carried out, no significant issues were identified, over and above those found by the INA Readiness Surveillance carried out in December 2019, that would prevent support of ONR’s overall approach in permissioning return to service. The overall ONR readiness inspection is subject to a satisfactory outcome of the planned complementary readiness inspection planned for the week commencing 3rd February.

In addition, a limited joint ONR/INA follow-up inspection, to be planned shortly before a return to service date, will be carried out to ensure inspection actions have been completed, and that circumstances have not significantly changed.