Executive summary
Date(s) of inspection:
- March 2023
Aim of inspection
The purpose of this inspection was to enable ONR to form a view on the claims made within the safety cases associated with the electrical and back-up systems under the control of the High Level Waste Plants (HLWP) and verify that the key equipment is available and adequately maintained.
Subject(s) of inspection
- LC 10 - Training - Rating: Green
- LC 23 - Operating rules - Rating: Green
- LC 24 - Operating instructions - Rating: Green
- LC 27 - Safety mechanisms, devices and circuits - Rating: Green
- LC 28 - Examination, inspection, maintenance and testing - Rating: Green
- LC 34 - Leakage and escape of radioactive material and radioactive waste - Rating: Not rated
Key findings, inspector's opinions and reasons for judgement made
For Licence Condition 10, I targeted the training of the Senior Authorised Person (Electrical), an Authorised Person (Electrical), and two Electrical Maintainers who were carrying out maintenance on the electrical systems that the Inspection team talked to during the walk round. Overall, I judged that the required standard was met and an inspection rating of Green (no formal action) is appropriate against LC10.
For Licence Condition 23 and 24, the safety case makes no direct safety claims for the provision of electrical power to the plant but the HLWP recognises that the loss of electrical power is an initiating event for several faults. Although there is no safety designation, the HLWP electrical systems have been identified as requiring a System Engineer, safety controls, back-up, and emergency arrangements. I targeted my inspection on a sample of the electrical boards, diesel generators and Uninterrupted Power Supply (UPS) batteries associated with the electrical supply to the safety function of the vessel ventilation system including the relevant emergency instructions for the loss of power and the maintenance instructions associated with the electrical boards. I was satisfied that the instructions followed a detailed step wise format containing the relevant steps to meet the safety requirements. Based on the evidence sampled I judge that an inspection rating of Green (no formal action required) is appropriate against Licence Conditions 23 and 24.
For Licence Condition 27 and 28, I targeted my inspection on a sample of the electrical boards, diesel generators and UPS batteries associated with the electrical supply and undertook a review of the maintenance records and system health reports. On the basis of the maintenance records sampled, I was satisfied that the electrical system is being adequately maintained. From the system health reports sampled, I was satisfied that the condition of the plant was known, and appropriate measures are in place to repair the known defects. Overall, I judge that the required standard is met and an inspection rating of Green (no formal action) is appropriate against Licence Condition 27 and 28.
For Licence Condition 34, I reviewed the potential for leakage and escape of radioactive material in connection with the electrical and back up system and judged that the electrical systems within HLWP are not sufficiently relevant to the licence condition under consideration. I have therefore not assigned any rating for Licence Condition 34 as a result of this inspection.
From the areas sampled, I provided some minor regulatory advice but did not identify any shortfalls in the implementation of the licensee’s arrangements which would necessitate a further inspection of the electrical systems earlier than currently planned.
Based upon the areas sampled I judge that the safety functions associated with the electrical and back-up systems (which support the relevant claims in the safety case) under the control of the HLWP have been adequately implemented.
Conclusion
From the evidence sampled during the inspection, I judge that Sellafield Ltd has adequately implemented the safety function of the electrical and back-up system (which support the relevant claims in the safety case) and that the formal arrangements for LCs 10, 23, 24, 27 and 28 are being adequately implemented. For LCs 10, 23, 24, 27 and 28 an inspection rating of Green (no formal action) is appropriate.
I have not assigned any rating for LC34 as a result of this inspection, since I judged this licence condition was not sufficiently relevant to the system under consideration.