Executive summary
Date(s) of inspection:
- March 2023
Aim of inspection
The aim of this inspection was to verify that relevant work activities have been carried out in relation to C&I equipment and systems important to safety in order to confirm that it remains fit for its intended purpose at SZB.
The inspection will also provide a contribution towards ONR’s regulatory decision as to whether a Consent, in accordance with LC 30 (periodic shutdown), should be issued to allow SZB to return to normal operating service.
Subject(s) of inspection
- LC 28 – Examination, inspection, maintenance and testing – Rating: Green
Key findings, inspector’s opinions and reasons for judgement made
Our inspection found that the commitments made in the SZB RO18 outage intentions document (OID) for C&I equipment and systems important to nuclear safety have been satisfied for those elements of work complete at the time of the inspection. Our inspection of the work activities covered during this intervention has generally found that the workmanship applied was adequate and consistent with the standards expected from C&I suitably qualified and experienced persons (SQEP).
Prior to the outage, while SZB was in the process of reducing power in preparation for shutting down, they experienced a problem with the movement of control rods. However, SZB provided assurance that this did not affect the capability for a rod drop to shut down the reactor, if necessary. SZB carried out investigations into the cause of the event. We reviewed these, as did other specialists within ONR, and had discussions with the responsible engineers at SZB. We were satisfied that SZB has identified a plausible cause for the event and identified suitable procedural mitigations to reduce the risk of this reoccurring. Nevertheless, we have identified some areas for improvement of the control rod drive system to be considered post restart. These actions will be tracked under ONR Regulatory Issue RI 11336.
We reviewed many of the reactor safety systems and found these to be in good order, well maintained with good tracking of any failures and well supported by the original equipment manufacturer. We did identify some areas for improvement in regard plant maintenance instructions to provide greater clarity of requirements and / or data recording but were minor in nature. We raised 3 actions which will be tracked under RI 11337.
Our inspection also reviewed polar crane and refuelling machine maintenance activities. There were shortfalls regarding procedural use and adherence, control of test equipment and clarity of plant maintenance instructions. It should be noted that we did not consider that these shortfalls posed an immediate or significant risk to nuclear safety or needed to be addressed before SZB returns to normal operating service. We raised five actions which will be tracked under RI 11337.
In our opinion, the polar crane, and potentially the wider fuel route equipment, C&I management remains one of the more challenging aspects in relation to examination, maintenance, inspection, and testing. We will follow this up as a separate activity in conjunction with the ONR SZB Nominated Site Inspector.
Conclusion
From the evidence gathered during this C&I-based intervention, we consider that there are no significant matters that may impact on nuclear safety. We have not identified any significant issues in relation to the C&I equipment and systems that should prevent ONR from issuing a Consent to allow SZB to return to normal operating service.
We raised 2 RI (11336&11337) to address shortfalls identified during the inspection. We did not consider that these shortfalls posed an immediate or significant risk to nuclear safety or needed to be addressed before SZB returns to normal operating service. The RIs will be followed up as part of normal regulatory business.
Based on our inspection of C&I aspects of the SZB RO18 it is recommended that support be given for a Consent to allow SZB to return to normal operating service following successful completion of the planned maintenance activities in accordance with LC 30.