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UK Inspector General’s report on Nuclear Safety and Radiation Protection 2017

The Inspector General’s report on Nuclear Safety and Radiation Protection 2017 NuClear News April 18 Published on 2nd March 2018, a report written by François de Lastic, EDF Group Inspector General for Nuclear Safety and Radiation Protection, for the Chairman of EDF is available in French and English on the EDF – French website here:

It aims, amongst other things, to identify any early warning signs and recommend areas for improvement. It therefore focuses on difficulties and weaknesses rather than strengths and progress.

The Inspector’s view of 2017 starts with the headline “a global nuclear industry adapting to the development of renewables”. He says there was a much higher global investment in renewable energy than in new nuclear build, as indicated in the 2017 World nuclear industry status report.

He says recent developments indicate a search for a new balance based on a synergy between nuclear energy and other low-carbon energies in the fight against global warming. The fact that low-carbon nuclear electricity has both a high level of safety and the ability to compensate for daily – and above all seasonal – variations in electricity demand gets little coverage.

EPRs In 2017, as in 2016, EDF SA experienced considerable technical problems, in particular the series of carbon segregation issues, the examination of the unmarked files (see insets) and some new hazards. Correcting defects and improving nuclear safety has led to a heavy workload for the operator and the engineering division. The Inspector remains concerned by the excessive workload which has gone on for at least two years now and is affecting the morale of some staff.

The Hinkley Point C construction site is well under way with strong logistical and organisational support, and industrial safety is one of the main priorities. The current reorganisation of the project’s governance will improve relations with the Office for nuclear regulation (ONR) and should improve the interface with engineering.

EPR milestones reached in 2017

 Taishan: the hot functional tests were started in April 2017 and the first fuel element was introduced into the fuel building’s storage pond in October.

 Flamanville 3: the cold functional tests ended in December 2017, followed by the successful completion of the hydrostatic test on the primary system in January 2018.

Hinkley Point C: the first nuclear safety concrete for the galleries was poured in March 2017.  EPR 2: the configuration for the next design phase was selected in October 2017.

Hinkley Point C

The Inspector General says over the last decade, its nuclear generation fleet and the ONR have successfully rebuilt relationships based on trust. But as far as Hinkley Point C is concerned there is still an unsatisfactory level of trust. (This sounds a problem for Hinkley Point C.)

The Inspector says the fact that skills were lost due to the lack of orders for new reactors in France partly explains the problems at Flamanville. Can these same problems be avoided at Hinkley?

Learning lessons from Flamanville 3, EDF is continuing to reorganise engineering, which has included setting up EDVANCE in 2017, a joint subsidiary of EDF SA and AREVA NP. Its first challenges will be its contribution to the project for the two Hinkley Point C EPRs in the UK and the design studies for a new reactor, destined for the renewal of the French fleet and for export.

The Inspector General says new project governance has been put in place at Hinkley Point C taking into account findings from a number of reviews and audits. This should help to optimise roles, clarify responsibilities and reinforce confidence in the relationship with the ONR.

“When I visited the construction site where some 2,500 people work, including several from CGN, I was struck by the extent to which the organisation, safety culture and quality controls were already in place and aligned with WANO’s ten traits. [Ten traits of a healthy nuclear safety culture developed by WANO] All of this goes a long way towards instilling confidence in the project’s future success.”

AGR Graphite Cracks

The Inspector notes the higher frequency of inspections of the graphite in those AGRs most affected by cracks. These inspections are becoming increasingly important as the reactors approach the end of their service life.

(Hinkley Point B reactor 3 was taken offline on 2nd February for its planned interim maintenance and graphite inspection. During the 16 day programme, 26 channels were successfully inspected in the reactor core to confirm its expected safe condition. The unit was successfully returned to service on 19th February. EDF said the findings underlined that the graphite is behaving as predicted, and we therefore remain confident in our plant lifetime forecasts. [Each reactor core is made up of around 6,000 blocks – 3,000 of these are graphite bricks containing fuel channels] which are all connected together. At Hunterston B Reactor 3 was taken offline on 9 March for a graphite inspection outage as agreed with the ONR and will involve inspection of the reactor core as well as a range of other maintenance and inspection work which can be carried out while the unit is offline. The reactor is expected back online on 30th March.)

The Inspector says characterisation of cracks in the graphite bricks of AGR cores is the key factor in determining their length of service life (the oldest reactors – Hunterston B and Hinkley Point B – came online in 1976). Regular inspections tailored to each reactor remain an essential means of ensuring there are no fast-developing cracks and of re-evaluating methods of control. In 2017, three new keyway root cracks were reported in two of the three reactors inspected. The total number of cracks remains well below the limits specified in the safety case for each reactor. He welcomes the increased frequency of inspections for the lead reactors

In the UK, EDF Energy will soon have to make some key decisions regarding the life extension and subsequent final shutdown of the AGRs in its fleet.

AGR Fuel Elements

8 elements were found to have leaks out a total of about 40,000 used in the reactors. Most of these failures were discovered in the same reactor. (Which one?) This led to the operator taking specific measures, including reducing the reactor power, lowering the rates of power increase, and increasing the cooling of the most highly irradiated fuel assemblies. The total number of leaks in this reactor fell from 16 in 2016 to 6 in 2017. The cause of these failures seems to be associated with carbon deposition on the fuel elements. This physical-chemical phenomenon is a highly complex issue to resolve. Solutions are currently being studied and I will monitor their effectiveness.

Other AGR notes

In the UK, post-Fukushima modifications consistent with AGR characteristics have been completed and operator training programmes now include beyond-design-basis accidents.

Collective exposure on AGRs is limited due to their design, and the collective doses measured are among the lowest in the world (0.02 man-Sv/unit). The annual collective dose for the Sizewell B PWR remained low (0.3 man-Sv), which places it in the top quartile worldwide. The maximum individual exposure for all reactors was 5.54 mSv.

Spent Fuel Transport

Transport of spent fuel: de-tensioned flask lid bolts It was reported in the UK that several bolts used to secure the lid of a transport flask containing spent fuel were found to be loose on arrival at the storage facility. This INES Level 1 event had no impact on safety but could have caused a contaminated water leak outside the flask had it endured a major accident. This event highlighted not only the inadequate incorporation of OPEX (Operational Experience) gained from a similar event that occurred 15 years earlier, but more importantly, a lack of compliance with procedures. (Where did this happen?)

Loss-of-grid events in the UK

The energy transition in the UK has led to the closure of coal-fired power stations in favour of renewables, which has reduced the national grid’s capability to come back online quickly following a blackout. A review of the safety studies for all nuclear plants was undertaken to demonstrate their ability to operate without the grid for longer periods of time. This necessitates larger on-site stocks of fuel oil so standby diesel generators can be used for longer periods. Blackout operating procedures have been reviewed and corresponding training actions have been instigated. The problem is limited in France because of the high levels of inter-grid connection across Europe and the different reactor technology to the UK.

Nuclear Skills

Managing the transition from AGRs to EPRs is a key issue for the future of EDF Energy. The end of the service life of the AGRs will lead to a reduction in the number of staff operating the sites concerned between 2023 and 2030. At the same time, the need for skills to implement new projects and operate future nuclear units will increase. New skills will also be needed for decommissioning activities

In the UK AGRs have not had any problems retaining staff. This, however, is not the case at Sizewell B where a number of operators were recruited by another PWR operator – a newcomer to the nuclear industry working in English. Action was quickly taken to deal with this situation, which could happen again


April 6, 2018 - Posted by | safety, UK

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