Heysham 1 - SBI07 - No-Break Electrical System
- Site: Heysham 1
- IR number: 15-113
- Date: November 2015
- LC numbers: 10, 23, 24, 27, 28, 34
Purpose of intervention
This was a planned inspection of EDF Energy Nuclear Generation Ltd’s (NGL’s) Heysham 1 power station, undertaken as part of the planned intervention strategy for the Civil Nuclear Reactor Programme (CNRP) of the Office for Nuclear Regulation (ONR).
The work was carried out in line with the planned inspection programme contained in the Heysham 1 Integrated Intervention Strategy (IIS).
Interventions Carried Out by ONR
I (ONR Electrical Specialist Inspector) with an Electrical Technical Specialist from AMEC Foster Wheeler carried out a System Based Inspection (SBI) on the 415V ac/ 440V dc No-Break Electrical System.
Explanation of Judgement if Safety System Not Judged to be Adequate
This system based inspection judged that the arrangements and their implementation, associated with the No-Break Electrical System, met the requirements of the safety case and are adequate.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
From the system based inspection on the No-Break Electrical System we concluded that:
- LC 10 (Training) – We examined the role profile and training records for a sample of the personnel involved in the maintenance of the No-Break System. The evidence identified the essential training requirements for each role profile and we found that all essential training was in date. We therefore assigned an IIS rating of 3 (adequate) to this inspection.
- LC 23 (Operating Rules) – The licensee’s operating rules were contained within its technical specifications and were well defined for the No-Break System we sampled. We found that technical specification compliance was well controlled and monitored. We therefore assigned an IIS rating of 3 (adequate) to this inspection.
- LC 24 (Operating Instructions) – We asked the licensee for the operating procedures for normal & emergency operation of the motor alternator sets as well as the maintenance schedules, procedures and selected records for the 440V dc batteries. The supplied documentation was of a good quality and followed the standard formatting and layout. The station personnel demonstrated a sound understanding of the equipment and the operational and maintenance requirements. We assigned an IIS rating of 2 (good) to this inspection.
- LC 27 (Safety Mechanisms, Devices and Circuits) – We judged that the No‑Break System was properly connected and in good working order. We considered that the documentation accurately reflected the as-built plant and that the plant was being regularly monitored, inspected and maintained. We noted that the No-break System performance statistics indicated a reliable system and following discussions with plant personnel it was clear that obsolescence was being adequately managed. We therefore assigned an IIS rating of 3 (adequate) to this inspection.
- LC 28 (Examination, Inspection, Maintenance and Testing) – We sampled maintenance work instructions and work orders for a sample 440V dc battery discharge and found the documents and associated records to be of good quality. Electrical protection testing and calibration is well controlled. We noted the information technology systems that are used to plan, track, execute, record the results and derive trends and system health statistics. Whilst the general quality of the LC 28 process management was considered adequate, the status of a couple of key components of the no-break system were considered below the expected standard for compliance with LC28, hence an IIS rating of 4 has been assigned.
- LC 34 (Leakage and Escape of Radioactive Material and Radioactive Waste) – We established that LC34 was not applicable to the No-Break System, and therefore no assessment was made against this LC.
The intervention was performed in line with ONR’s guidance requirements (as described in our technical inspection guides) in the areas inspected.
Conclusion of Intervention
After considering all the evidence examined during the sample inspections undertaken against LCs 10, 23, 24, 27 and 28, we considered that the No-Break Electrical System met the requirements of the safety case.
ONR Issue Numbers 3957, 3958 and 3959 were raised to address concerns over the condition of a specific item of Central Control Room equipment, substantiation of seismic qualification for part of the No-Break system and maintenance of fire barriers associated with cables between the turbine hall and the battery rooms. These will be monitored as part of normal regulatory business.
Notwithstanding the above, there are no findings from this inspection that could significantly undermine nuclear safety.