Office for Nuclear Regulation

Torness Power Station – Licence Condition Compliance Inspections covering LC 9, 23, 24, 25 (external flood theme)

Executive summary

Purpose of intervention

The purpose of this intervention was to conduct Licence Condition (LC) compliance inspections at EDF Energy Nuclear Generation Limited’s (NGL’s) Torness (TOR) Power Station in line with the planned inspection programme contained in the Torness Integrated Intervention Strategy (IIS) for 2015/16.

This intervention was undertaken by the nominated site inspector for Torness, in conjunction with two ONR External Hazards specialist inspectors.

Interventions carried out by ONR

This intervention included compliance inspections against the following Licence Conditions (LCs):

The areas of the station sampled for the purposes of this compliance inspection were selected to focus on external flood protection and recent flood resilience enhancements. This inspection was the first of a series of planned fleet-wide external flood based inspections following resilience improvements and lessons learnt from the Fukushima accident in Japan in March 2011, which resulted from an earthquake and subsequent Tsunami.

Explanation of Judgement if Safety System Not Judged to be Adequate

No safety system inspection was undertaken, hence this is not applicable.

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

The LC9 (Instructions to persons on site) inspection focussed on the implementation of arrangements resulting from the recent installation of Japanese Earthquake Response (JER) equipment. We observed a number of recently installed resilience equipment, and noted the work ongoing to fully commission this equipment and train personnel concerned, and on that basis have given this inspection an IIS rating of 2 (good standard).

The LC23 and LC24 inspections covered station Operating Rules (ORs), Operating Instructions and sampled sections of the safety case related to external flooding, from which any flood related operating rules should be derived. We noted that the claims, arguments and evidence were not always clearly articulated in the safety case, and that various sections of the safety case lacked consistency.

Our findings have been accepted by the station, which has raised actions within their arrangements to undertake corrective action. In addition, the requirements for Torness to clarify the safety case and to confirm the one in 10,000 years design basis still water level for external flooding have been entered on ONR’s issues database, to capture and monitor progress. The shortfalls identified in the external flooding hazard safety case, from which any flood related operating rules should be derived, have resulted in an IIS rating of 4 (below standard) against LC 23 for this intervention. Compliance with LC24 was judged to be adequate, and was therefore rated 3.

The LC25 inspection examined operational records related to sea defences, groundwater borehole measurements and reactor power reduction or trip due to seaweed ingress. We noted that good local weather information is available at Torness, and suggested that Torness should consider trending these data to improve the accuracy of the design basis for external hazards. On the basis of the records sampled, we considered an IIS rating of 3 (adequate) against LC25 to be appropriate.

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

On the basis of our sample, we judged that the arrangements and their implementation at Torness for LC24 and LC25 were adequate (rating 3), of good standard for LC9 (rating 2), but below standard for LC23 (rating 4) where we found that various sections of the safety case were not clearly articulated and lacked consistency.

There were no findings from this inspection that could significantly undermine nuclear safety or which would result in changes to the planned interventions and inspections of Torness Power Station.