Licence Condition 23 (Operating Rules) Discussions with Hartlepool (HRA) on Station Specific Challenges Associated with Carbon Deposition and Inspection under LC 27 (Safety Mechanisms Devices and Circuits) of the Burst Can Detection (BCD) and Gamma Activity Monitoring (GAM) Equipment.

Executive Summary

Purpose of intervention

Two separate Interventions are reported in this Office for Nuclear Regulation (ONR) Intervention Report i.e.

• Discussions with the licensee (conducted under Licence Condition LC 23, Operating Rules) on Hartlepool specific challenges posed by Carbon Deposition (CD).
• Inspection (under LC 27 – Safety Mechanisms, Devices and Circuits) of the station’s Burst Can Detection (BCD) and Gamma Activity Monitoring (GAM) equipment for the detection of failed fuel.

Interventions carried out by ONR

Both Interventions were conducted by face-to-face meetings with key licensee personnel.  In the case of the BCD/GAM equipment, a visual inspection of the equipment was also conducted. 

Key findings, Inspector’s opinions and reasons for judgements made

The key findings from the meeting on station specific challenges caused by CD were:-

• Multiple problems have been emerging over circa the last 10 years, across the station’s fuel route, where CD is extending maintenance times on a number of key systems/pieces of equipment.
• The CD trends observed indicate a worsening picture.
• Engagement with the Fleet Critical CD Programme at Barnwood is good and Barnwood are assisting in taking on the burden of some of the bigger projects, designed to provide improvements in areas where CD is presenting a challenge to ongoing operations.
• Clear links have been forged and are being maintained, with other Stations in the EDF Energy Nuclear Generation Ltd (EDF NGL) fleet, to enable a sharing of knowledge on the challenges posed by CD and solutions/mitigations for some of these challenges.
• Station staff were observed to be being proactive in designing and implementing some of their own solutions to a variety of the observed CD problems on the Station.
• Current maintenance resources are being stretched as a direct result of the challenges posed by CD.

From the inspection of the Station’s BCD/GAM systems the key points were that:-

• The current non-intact fuel in one of the reactor cores has still not been located, although recent BCD survey work has identified a ‘candidate’ channel and further work will be following very shortly to further investigate this fuel channel.
• Work is still ongoing to understand the root cause(s) of the observed low/no gas flow to the BCD equipment in multiple fuel channels.  ONR will continue to monitor progress in this area, with an expectation that the root cause will be identified and a suitable maintenance activity will be specified, to the lower the potential for any future such occurrences.
• The BCD equipment on the Station (BCD trolleys and the sequencers) has recently been upgraded to ‘state of the art’ systems.  Nonetheless the Station appears to be actively seeking to identify potential obsolescence issues, to ensure they can take timely action to secure the ongoing functionality of the BCD equipment for the remaining Station life.
• The Station appears to be in a strong position in terms of the number of personnel trained in the use of the BCD equipment.  Likewise the Nuclear Safety Group (NSG) has at least 4 persons who are Suitably Qualified and Experienced Persons (SQEP) for analysis of BCD data.
• Although the GAM equipment is generally much older and there are potential obsolescence issues with some of this equipment and its software, Station was able to convince me that these have all been considered and viable alternatives are quickly available.
• The lack of fuel bottling for some time now at the Station is starting to present operational challenges to the available Buffer Storage Tube capacity on the Station.  The ONR Site Inspector will follow this up as a part of his routine regulatory business.

Conclusion of intervention

Both Interventions conducted produced a broadly acceptable outcome, although it is important that bottling of failed fuel recommences on the station during this year, to remove mounting challenges to capacity for buffer storage of irradiated fuel.  It is also of importance that the causes of low/no flow of gas to the BCD equipment are identified and remedial measures instigated.

Recommendations

No recommendations were recorded under this intervention