Office for Nuclear Regulation

SBI02 Inspection

Executive summary

Purpose of Intervention

The purpose of this intervention was to undertake a system based inspection (SBI) at EdF Energy Nuclear Generation Ltd.’s (EdF NGL) Sizewell B (SZB) power station.  The inspection was conducted in line with Sizewell B inspection plan.

Interventions Carried Out by ONR

We performed a system based inspection (SBI) to confirm the implementation of safety claims made on the Auxiliary Feedwater System (AFWS).  This inspection was undertaken by the ONR site inspector and two specialist inspectors.  During this intervention we examined EDF NGL’s compliance with the following nuclear site licence conditions (LCs), which are applicable provisions of the Energy Act 2013:

The inspections were based on sampling the implementation of the licensee’s arrangements at SZB against the LCs. The objective of the inspection was to determine whether the licensee’s arrangements were adequately implemented and in accordance with the systems’ safety case requirements.

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

Following an SBI of the Auxiliary Feedwater System, we judge that overall this system fulfils the requirements of the safety case and is adequate.

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

LC 10 (Training) - For this part of the inspection we chose to sample a range of employee training records for individuals who carried out visual and instrumented examinations, calibration tests and other checks on the AFWS system components, Condensate Storage Tank (CST) and related pipework.  From the evidence gathered during the SBI, we judged that the Plant System Training is comprehensive and that the personnel were adequately trained to perform the tasks indicated in the work orders at the time the tasks were carried out.  Overall, we consider that an ONR inspection rating of GREEN is appropriate for LC10.

LC 23 (Operating Rules) & LC 24 (Operating Instructions)  - With regards to LC 23, we sampled the licensee’s compliance with a number of surveillance requirements identified under the site Technical Specifications (TS). We examined the TS basis and other documents and we found a clear link with the safety case.  The inspection confirmed that the station has made and implemented adequate arrangements to ensure that the system is operable when required.  We judged LC 23 aspects of the SBI to be adequate, with the licensee having identified, implemented and demonstrated compliance with operating rules derived from the safety case.

In relation to LC 24 we verified the station’s arrangements to ensure that personnel are provided with instructions to ensure that plant operations remains within limits and conditions identified in the safety case and the station’s technical specifications.  We sampled operating instructions (SOI) provided to staff to operate the equipment in the event of a loss of off-site power.  We found that clear instructions are provided to Main Control Room (MCR) staff on their expected actions in respect to monitoring of steam generator level and the status of the auxiliary feed system following a loss of off-site power.  Overall, we judged that these arrangements were consistent with relevant benchmarks for LC23 and LC24.  One minor compliance shortfall was noted regarding errors noted in an instruction provided to align the auxiliary feed system following maintenance.  EDF NGL has committed to address the issue and an entry has been made on the ONR issues database to monitor resolution.  Overall, we consider that an ONR inspection rating of GREEN is appropriate for LC23 and LC24.

LC 27 (Safety Mechanisms, Devices and Circuits) - LC 27 requires that the plant is not operated, inspected, maintained or tested without suitable and sufficient safety mechanisms, devices and circuits (SMDCs) being properly connected and in good working order.  This was confirmed during a plant walkdown.  A visit to the main control room (MCR) was carried out to evaluate compliance with this licence condition. The Duly Authorised Person (DAP) and the Work Execution Centre (WEC) supervisor demonstrated their sound knowledge of the system.  We sampled several plant parameters confirming that instruments were operating and indicated readings were within technical specification requirements.  Based on the evidence sampled, we judge that EDF NGL was compliant with its legal requirements under LC27 and therefore we judge that an inspection rating of GREEN is appropriate.

LC 28 (Examination, Inspection, Maintenance and Testing) - LC 28 requires the licensee to make and implement adequate arrangements for examination, inspection, maintenance and testing (EIMT) of all plant which may affect safety.  We sampled records which demonstrated completion of the system’s preventative EIMT regime as described in the plant maintenance schedule.  We drew our sample for examination from three broad areas the condensate storage tank, associated pipework and turbine-driven auxiliary feedwater pumps.  We also examined EDF NGL’s maintenance strategy review reports for the auxiliary turbine system and similarly for the feedwater system.  We considered these reports to be comprehensive, providing an evaluation the adequacy of the system’s preventative EIMT regime.

Overall, we consider that an ONR inspection rating of GREEN is appropriate for LC28. One minor administrative non-compliance was identified in relation to signoff of maintenance records via a supervisor in accordance with LC28(9). EDF NGL committed to address the issue, which will be monitored via an entry on the ONR issues database.

Conclusion of Intervention

From the evidence sampled during this SBI inspection, we consider that the Auxiliary Feedwater system met the requirements of the safety case.

There are no findings from this inspection that could significantly undermine nuclear safety.  At present, no additional regulatory action is needed over and above the planned interventions at Sizewell B Power Station.

Overall we judged that the arrangements for the inspection, maintenance and monitoring of the AFWS met relevant good practice and therefore we have given an intervention rating of GREEN in relation to compliance with LCs 10, 23, 24, 27, and 28.