Office for Nuclear Regulation

Systems Based Inspection (Fuel Assemblies)

Executive summary

Purpose of intervention

The purpose of this intervention was to conduct a systems based inspection (SBI) of EDF Energy Nuclear Generation Ltd's (NGL) Torness Power Station in relation to fuel assemblies. The intervention was undertaken by the Office for Nuclear Regulation (ONR) nominated site inspector and a specialist fuel inspector and was carried out in line with the planned inspection programme for 2014/15 contained in the Torness integrated intervention strategy (IIS).

Interventions Carried Out by ONR

Systems Based Inspections (SBI) involve a 'deep slice' sample into the safety case and its supporting documentation, with a view to ascertaining the adequacy of the implementation of the licensee's arrangements as a part of licence condition (LC) compliance. These inspections are generally undertaken with the support of specialists within ONR and are informed through a review of the safety case (including supporting references and records), discussions with station specialists, plant inspection and the sampling of documents and records.

This intervention considered the arrangements in place for fuel receipt, storage and assembly. Through examination of the fuel assemblies system we performed compliance inspections against LC 10 (training), LC 23 (operating rules), LC 24 (operating instructions), LC 27 (safety mechanisms, devices and circuits), LC 28 (examination, inspection, maintenance and testing) and LC 34 (leakage and escape of radioactive material and radioactive waste).

Explanation of Judgement if Safety System Not Judged to be Adequate


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

LC 10 (Training) - We examined the role profile, training records and accreditation certificates for several Duly Authorised Persons (DAP) on the station fuel route (as well as a random sample of the training records for a number of other relevant personnel). We generally found the training records examined to be in order; although one DAP accreditation certificate was found to be missing from the Training Group files (the licensee has agreed to pursue this). We identified a finding associated with attendance at the advanced criticality safety training course. The licensee has raised a Condition Report (CR) on this finding, which the ONR site inspector will track as a part of his normal regulatory business. We considered that this inspection merited an (IIS) rating of 3 (i.e. Adequate).

LC 23 (Operating Rules) - For the fuel assemblies system, the licensee was able to demonstrate a strong link from the relevant sections of the Station Safety Report (SSR) to the operating rules, as described by the station's Technical Specifications (Tech Specs) and had pre-prepared some helpful flow diagrams illustrating this link. We sampled 3 of the key Tech Specs focusing on the surveillances conducted under the Tech Specs through examination of the documentation contained within two fuel build folders, sampled at random, which were found to be in good order. One minor issue was identified (i.e. we suggested that station should evidence its criticality safety checks, prior to any operations involving fuel, by signing off the relevant check sheet). Station has raised a CR to cover this observation, which will be tracked by the ONR site inspector as a part of his routine regulatory business. Overall, we judged that the inspection under this licence condition merited an IIS rating of 2 (i.e. Good).

LC 24 (Operating Instructions) - Further to the above inspection on LC 23, the licensee was again (via the flow diagrams) able to show how the Tech Specs translate into the lower level work instructions. We sampled compliance with the lower level work instructions across all the relevant Tech Specs, which we found to be satisfactory in all cases. Accordingly, we considered that this part of the inspection merited an IIS rating of 2 (i.e. Good).

LC 27 (Safety Mechanisms, Devices and Circuits) - A common definition of Safety Mechanisms Devices and Circuits (SMDC) is presently still being developed between ONR and the licensee. Consequently, we found little to examine in this area although we did consult the licensee's Central Document Management System (CDMS) to look for reports of interlock defeats on the fuel route (no reports were found). We also examined the maintenance records (under LC 28) of the only safety related interlocks we identified on the fuel assemblies system. Due to the limited nature of our inspection we judged an IIS rating of 3 (i.e. Adequate) to be appropriate.

LC 28 (Examination, Inspection, Maintenance and Testing) - Picking a number of key items of equipment in the new fuel areas of the plant at random, we sampled required maintenance activities and then requested and sampled recent Work Order Cards (WOCs), maintenance inspection test certificates etc. All maintenance records examined were found to be in order. We judged that an ISS rating of 3 (i.e. Adequate) was appropriate.

LC 34 (Leakage and Escape of Radioactive Materials and Radioactive Waste) - For this part of the inspection we concentrated on the detection of failed fuel both in-core and ex-core (i.e. at the Decay Store). Whilst we found the Burst Can Detection System to be in good condition, we identified vulnerability with the station's Gaseous Activity Monitoring (GAM) system. In addition we identified that, in contrast to other stations, Torness has no ability for ex-core detection of failed fuel. The licensee raised CRs against both observations, which will be tracked as a part of routine regulatory business. Accordingly, we judged that an IIS rating of 3 (i.e. Adequate) was appropriate.

The licence conditions were inspected against ONR's published guidance requirements (as described in our technical inspection guides).

Conclusion of Intervention

After consideration of all the evidence witnessed during the sampling inspections undertaken against LCs 10, 23, 24, 27, 28 and 34, we consider that the arrangements and their implementation, associated with fuel assemblies, meet the requirements of the safety case and are deemed adequate.

A number of observations were made as a result of the system based inspection; however, given that they are of minor nuclear safety significance, we are content that they be addressed by NGL in accordance with their own arrangements. NGL has raised Condition Reports (CRs) that capture the observations as a number of actions.

There were no findings from this inspection that could significantly undermine nuclear safety and accordingly no actions were raised during this inspection.