Office for Nuclear Regulation

Heysham 1 - SBI07 - No-Break Electrical System

Executive summary

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:

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.