Office for Nuclear Regulation

Inspections during reactor No. R2 outage related to fuel matters

Executive summary

Purpose of intervention

My intervention, which was conducted at EdF Nuclear Generation Ltd’s (EdF NGL i.e. the licensee) Torness power station, was undertaken as a part of the Office for Nuclear Regulation’s (ONR) Civil Nuclear Reactor Programme (CNRP) - Operating Reactors Sub-Programme - annual plan for regulating Licence Condition 28 Examination, insoection, maintenance and testing of periodic shut-downs/statutory outages on EdF NGL’s operating reactor fleet.  In this case the intervention was conducted for the statutory outage of Torness Reactor R2.

Interventions Carried Out by ONR

I conducted my intervention, under Licence Condition (LC) 28 to inspect a number of fuel related matters pertinent to the outage.  Specifically, as per my “Outage Inspection Plan”, I inspected:-

Criticality safety awareness training for contract staff involved in the outage and the role of the station “Criticality Specialist” during outages.

Any work planned during the outage to remediate reactor fuel channels, where the gas flow to the Burst Can Detection (BCD) equipment has been found to be inadequate to assure failed fuel detection by the BCD equipment and/or any general remedial or enhancement work to be conducted in the outage on the BCD system or the Gaseous Activity Monitoring (GAM) system for Reactor R2.

The procedures, roles and responsibilities, compliance route etc. to invoke the station’s permanent ‘failed fuel in air’ safety case, should failed fuel have been present in the core prior to going into outage, or if fuel failures had occurred during reactor blow-down.

The station’s arrangements for interrogating coolant activity data during reactor blow-down to air (to look for the possible presence of fuel failures).

Progress with pressurised inspections of the station’s fuel Buffer Storage Tubes (BST) – not strictly an activity planned for the outage, but a project ONR wishes to influence the licensee to make progress on (as the station has to certify at least 2x BSTs as being free from radiolytic deposition (RaDep) i.e. to accommodate potential failed fuel, going into an outage).

Station progress with export of reject unirradiated fuel and fuel components.

Explanation of Judgement if Safety System Not Judged to be Adequate

I did not conduct a Systems Based Inspection (SBI) under this intervention and hence this heading is not applicable.

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

My key findings and opinions, against each of the inspection areas described above, are described below:

Criticality Awareness Training – I am broadly content that all staff working on station have some criticality awareness training and that during an outage, the very small number of specialists, coming to the station to potentially work in areas controlled by criticality safety certificates, are provided with an enhanced level of training on the risks posed by criticality.

I was pleased to see that the role of the ‘Criticality Specialist’ is bedding in well at Torness, with good evidence being provided that the trained specialists are delivering the full scope of the role as originally defined by the licensee.  Several examples of good practice were observed, although the licensee conceded that it accepted my challenge that more ad-hoc walk-downs (in addition to the planned 6 monthly criticality walk-downs) may be appropriate during outages.  The licensee also accepted that arrangements, for periods when both appointed Specialists were off station, need to be formalised and disseminated.

BCD/GAM – The BCD system is functioning well and good control appears to be being exercised by the station on control of so called ‘Dark Channels,’ i.e. fuel channels where the flow of reactor gas to the BCD detection/measurement trolley is too low to enable potential failed fuel to be detected in the channel.  Currently Torness report only one low flow channel on Reactor No. 1 (where readings are still possible).  The GAM system continues to suffer from a number of minor problems (probably associated with the age of the system) but overall is delivering an acceptable service and the station staff seem adept at resolving any GAM system problems encountered.  I was hence broadly content with the licensee’s performance in this area.

Failed Fuel in Air Safety Case – The outage commenced with no revealed failed fuel in core and no fuel failures occurred during reactor blow-down.  Accordingly, the station “failed fuel in air” safety case did not have to be invoked on this occasion.  However, the licensee presented its procedure for invoking the case when required and explained the close links it has with the key Nuclear Technology Branch (NTB) personnel at Barnwood during such periods.  I considered the licensee’s arrangements in this area to be adequately robust.

Blow-Down Coolant Activity Monitoring – The licensee presented their arrangements for analysing GAM data during reactor blow-down and presented data from a number of recent blow-downs, which highlighted the licensee’s competence in this area.  I also questioned the licensee regarding resilience, in terms of staff trained to execute this required analysis and was content that the licensee has adequate ‘defence in depth’ for the work.  Accordingly, I was satisfied by this part of my inspection.

BST Inspections – Whilst it is perhaps disappointing that the porthole closure project for pressurised BST inspections has not proceeded on the station as quickly as ONR would have liked, I held useful discussions with both station personnel and the key project officer at Barnwood (by phone link) to understand the delays and to obtain indications as to the forward trajectory of the project.  I also took the opportunity to view the equipment that has been delivered to station to date.  Since the project is likely to deliver the first active inspections in late 2015/early 2016, then I will maintain over-sight of the project via my routine level 4 interactions with the Barnwood team over-seeing the project.

Reject Fuel and Fuel Components – I provided information (copies of e-mail correspondence from Nuclear Fuels Liabilities at Barnwood) explaining the current position with respect to contracts to allow reject fuel (and energy bearing fuel components) to be returned to Springfields Ltd for recycle.  Currently Torness is not yet permitted to return any of its fuel/energy bearing fuel components, but the position is likely to change soon.  I stressed the station could, however, dispose of clearance monitored non-energy bearing fuel components to local recycling routes.  The station challenged that there could be public relations issues associated with the export of nuclear components from the station but it wished to consider perhaps pre-treating the components, so that they were not obviously fuel related.  I accepted this position.

Conclusion of Intervention

 From the totality of my inspection (which included a plant visit, discussions with key licensee personnel and sampling of station documentation) it is my opinion that the inspection indicated no nuclear safety issues requiring further ONR intervention and that no reactor re-start issues were flagged from my inspection.