Executive summary
Date(s) of inspection:
Aim of inspection
ONR raised RI-11069, following the July 2022 extreme ambient temperature (EAT) event. The closure strategy for RI-11069 includes undertaking inspection activities to assess the adequacy of EDF NGL’s arrangements for managing risks from EAT. Inspections are an essential element of ONR’s interventions on nuclear licensed sites. The overarching aims of this inspection were to:
evaluate (on a sample basis) whether the systems claimed in EAT safety cases at Sizewell B nuclear power station can deliver the safety functional requirements defined in the safety case.
test the adequate implementation of arrangements made under the Licence Conditions (LC) listed as Inspection Activities.
Subject(s) of inspection
- LC10 - Training - Rating: Green
- LC22 - Modification or experiment on existing plant - Rating: Green
- LC23 - Operating rules - Rating: Green
- LC24 - Operating instructions - Rating: Green
- LC28 - Examination, inspection, maintenance and testing - Rating: Green
- Overall Inspection Rating - Rating: Green
Key findings, inspector's opinions and reasons for judgement made
This was an inspection of EDF Nuclear Generation Limited's arrangements for extreme ambient temperatures at Sizewell B nuclear power station. ONR raised the level 3 regulatory issue, RI-11069, following the July 2022 heat wave. Such events have the potential to challenge nuclear safety. The closure strategy for RI-11069 includes inspection activities to assess the adequacy of EDF NGL’s updated arrangements for managing risks from EAT.
This inspection has assessed EDF NGL's arrangements relevant to extreme ambient temperatures for compliance with the following licence conditions:
- LC10 - Training. A green rating was awarded as EDF NGL has provided adequate training to its operators with respect to temperature forecasting arrangements and how to respond to future extreme ambient temperature events.
- LC22 - Modification of experiment on existing plant. A green rating was awarded as EDF NGL is managing the deployment of portable air conditioning units using an engineering change. This is judged a good practice.
- LC23 - Operating rules. A green rating was awarded as EDF NGL has a clearly defined limit and condition of operation in the non-nuclear emergency handbook.
- LC24 - Operating instructions. A green rating was awarded as EDF NGL has operating instructions relevant to extreme ambient temperatures including for forecasting and to ensure compliance with the non-nuclear emergency handbook.
- LC28 - Examination, inspection, maintenance and testing. A green rating was awarded as EDF NGL was able to demonstrate that it is adequately maintaining its plant claimed against extreme ambient temperatures.
Overall, this inspection was awarded a Green rating. ONR judged that any observed shortfalls were minor, EDF NGL has provided evidence following the inspection that these had been rectified or actions have been raised. On this basis ONR judges that EDF NGL is adequately implementing its compliance arrangements relevant to extreme ambient temperatures.
ONR has provided advice to EDF NGL in relation to observations made during this inspection. This advice is recorded in this record. It will be formally communicated to EDF NGL via letter as part of RI-11069. ONR expects EDF NGL to use this advice to enhance its EAT arrangements as part of its ongoing work to address safety case shortfalls for extreme ambient temperatures and wider meteorological hazards
Conclusion
ONR has inspected EDF NGL’s compliance arrangements relevant to EAT. Overall, this inspection is awarded a Green (No Formal Action) rating. Whilst some shortfalls to good practice have been identified they are either judged to be minor gaps or EDF NGL has subsequently provided evidence that the observed shortfalls have been rectified. EDF NGL is judged to be adequately implementing its arrangements for EAT.
ONR has provided advice to EDF NGL in relation to observations made during this inspection. This advice is recorded in this IR. It will be formally communicated to EDF NGL via letter as part of RI-11069. ONR expects EDF NGL to use this advice to enhance its EAT arrangements as part of its ongoing work to address safety case shortfalls for EAT and wider meteorological hazards.