Office for Nuclear Regulation

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Torness - System Based Inspection - SBI 18 - Instrument Air and Turbine Overspeed Protection System

Executive summary

Purpose of intervention

The purpose of this intervention was to undertake a system based inspection of the Instrument Air and Turbine Overspeed Protection Systems at EDF Nuclear Generation Limited’s (NGL’s) Torness Power Station in line with the planned inspection programme contained in the Torness Integrated Intervention Strategy (IIS) for 2015/16.

Interventions Carried Out by ONR

As part of this intervention, the ONR Nominated Site Inspector and Electrical Specialist Inspector performed a System Based Inspection (SBI) of the Instrument Air and Turbine Overspeed Protection Systems to judge each system’s performance against its safety function.  Through examination of the systems and their associated sub-systems, we performed compliance inspections against Licence Conditions LC10 (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 against each licence condition.

We also held routine update meetings with the licensee’s internal regulator, with the quality management group for the review of progress on issues identified during previous inspections, and with the Torness site safety representatives.

Explanation of Judgement if Safety System Not Judged to be Adequate

From the inspection, we judge that overall the Instrument Air and Turbine Overspeed Protection Systems meet the requirements of the safety case and are adequate.

Key Findings, Inspectors' Opinions and Reasons for Judgements Made

Based on the areas sampled during the course of the SBI, it was found that Torness has adequate arrangements to ensure that the Instrument Air and Turbine Overspeed Protection Systems meet the requirements of the safety case.   

In summary, the outcome from the System Based Inspection of the Instrument Air and Turbine Overspeed Protection Systems is that the arrangements and the implementation for LC 10, 23, 24, 27 and 28 were deemed to be adequate and therefore we have given an inspection rating of 3 (adequate) for each of these LCs.  LC 34 was not applicable to the systems under inspection, so no rating has been given.

There were no ONR Issues raised during this inspection.  A number of areas for potential improvement have also been identified and, although none gave rise to significant concern, EDF-NGL has agreed to follow them up in accordance with their own arrangements.

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 (LC 34 was not applicable), we considered that the Instrument Air and Turbine Overspeed Protection Systems 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 of Torness power station as set out in the Integrated Intervention Strategy, which will continue as planned.