Office for Nuclear Regulation

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Heysham 2 - System Based Inspection - SBI 04 (Auxiliary Cooling Systems)

Executive summary

Purpose of intervention

The purpose of this intervention was to conduct a system based inspection of EDF Energy Nuclear Generation Ltd's Heysham 2 Power Station in relation to the auxiliary cooling systems. This was undertaken as part of a series of planned interventions that are listed in the Heysham 2 Integrated Intervention Strategy (IIS) 2016/2017. The inspection was undertaken by the ONR Nominated Site Inspector, two Specialist Inspectors (Structural Integrity) and a nuclear graduate (training purposes).

Interventions Carried Out by ONR

We performed a safety case informed system based inspection of the auxiliary cooling systems. Through examination of these systems compliance inspections were performed against Licence Conditions (LC): LC 10 (training), LC23 (operating rules), LC24 (operating instructions), LC27 (safety mechanisms, devices and circuits), LC28 (examination, inspection, maintenance and testing) and LC34 (leakage and escape of radioactive material and radioactive waste). The inspections were based on sampling the implementation of the arrangements in place at the station against each licence condition. The objective of the inspection was to determine whether the Licensee's arrangements for plant operational limits, plant maintenance schedules, staff training requirements and third party inspection plans were in accordance with the system's safety case requirements.

Explanation of Judgement if Safety System Not Judged to be Adequate

From this inspection, we judge that overall the safety provisions applicable to the auxiliary cooling systems inspected meet the requirements of the safety case and are adequate.

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

A system based inspection of the auxiliary cooling systems was carried out to judge the adequacy of the implementation of the station arrangements in place to ensure that relevant equipment can perform its requisite safety function. In deciding whether this safety system has been adequately implemented, We inspected compliance with the licence conditions detailed above. LC34 relating to leakage/escape of radioactive material and waste was deemed to be not applicable to the systems inspected and hence excluded from the scope of the inspection.

During the course of this system based inspection it was found that Heysham 2 Power Station has arrangements to ensure that the Auxiliary Cooling Systems inspected are maintained and, as necessary, operated in accordance with its safety case. The arrangements were deemed to be implemented in an adequate manner, on the basis of those areas sampled during the inspection. The inspection identified potential areas for improvement however none gave rise to significant concern. Due to the limited significance of the observations, We are content that NGL will address these through their own arrangements.

In summary, the outcome from the system based inspection of the Auxiliary Cooling Systems inspected are that the arrangements and their implementation are deemed to be adequate, and therefore we have given an IIS rating of GREEN for LCs 10, 23, 24, 27 and 28.

On the plant walkdown a leak was observed on the -9 m level in 7 B Quadrant. There was already a defect tag in this region relating to a condensate leak, however, a large region of the ceiling was wet and the cause was unknown. The site inspector has raised an ONR issue to monitor the progress of actions raised.

The Heysham 2 site inspector held a routine engagement meeting with INA. The findings of the SBI and the ONR issue with regard to the leak identified at the at -9m level in B Quadrant were discussed.

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 and 28, we concluded that the Auxiliary Cooling Systems inspected met the requirements of the safety case.

An ONR issue (4456) was raised to monitor the progress of the actions raised for the leak on the -9 m level in 7 B Quadrant.

There are no findings from this intervention that could significantly undermine nuclear safety.