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The UK/Ireland Nuclear Free Local Authorities are concerned that EDF Energy, the arm of French state-owned Électricité de France which operates the UK nuclear fleet, has just announced its intention to further extend operations at its four remaining aging Advanced Gas-Cooled Reactor plants.
Hartlepool, Heysham-1, Heysham-2, and Torness first began generating in either 1983 or 1988, with an estimated operational life of 30 years. In 2023, the operating lives of Hartlepool and Heysham-1 were extended by two years from 2024 to March 2026, however the closure of Heysham-2 and Torness had previously been brought forward from 2030 to March 2028 because of ‘impacts on the graphite cores’.
The aging AGR plants will have been operating for at least 40 years by 2028, and the NFLAs’ core concerns revolve around the safety risk posed by the degradation of the graphite neutron moderators in each reactor.
NFLA Scotland Policy Advisor Pete Roche finds the rethink of the situation at Torness and Heysham 2 totally inexplicable: “In May 2020 we learnt that the cores of the four reactors at Torness and Heysham 2 were predicted to start cracking in 2022, six years earlier than previously thought. These last two AGRs have a significant design difference, compared to other AGRs which could make the cracking problem worse. Several commentators, at the time, questioned whether the two stations would make it even as far as 2028.
In 2020 the Office for Nuclear Regulation said the design difference at Torness and Heysham 2 could lead to graphite debris challenging the reactors’ ability to move or adequately cool fuel. And if the Regulators modelling predictions on the graphite core cracking were realised, then the reactors would not be safe to operate for another ten years. Heysham-1 and Hartlepool face similar operational challenges.
Yet in the ‘UK Nuclear Free Stakeholder Update’ published earlier this month, EDF company bosses state: ‘The prospect of further AGR lifetime extensions ([of] four power stations) will be reviewed again by the end [of] 2024 and the ambition is to generate beyond these dates, subject to plant inspections and regulatory approvals.’[1]
To support this ‘ambition’, EDF Energy also pledges to: ‘invest a further £1.3 billion over the next three years (2024-26) to help sustain current levels of generation’ within the company’s Nuclear Operations Division.
The function of the graphite core and the impact of aging is detailed by the Office of Nuclear Regulation (ONR) on its website:
https://www.onr.org.uk/civil-nuclear-reactors/graphite-core-ageing.htm
‘As well as moderation, the fundamental safety requirements of an AGR core include allowing free movement of control rods, free movement of fuel and directing the flow of coolant gas to ensure adequate cooling of the fuel and core structure. Essentially, significant weight-loss and cracking may compromise these safety requirements.
‘During operation, the graphite slowly loses weight due to oxidation caused by the reactor’s carbon dioxide coolant gas. Loss of weight affects both the mechanical properties of the graphite brick, and reduces its effectiveness as a moderator.’
We raised our concerns that graphite core cracking could over time seriously compromise safety as far back as 2014 and most recently in correspondence, and in meetings, with officials from the ONR.
Our concerns and activities on this issue were outlined in our briefing No 250 ‘Update on the AGR closure programme’, dated 17 October 2022:
The ONR is itself concerned at the impact of the deterioration of the graphite cores over time:
‘[Graphite] weight-loss is potentially a life limiting condition for the reactors, although we believe that most of the AGRs will have their life limited by the progression of cracking.’
It commissioned a Dutch institution to carry out accelerated modelling of the deterioration and in July 2022 also awarded a £2 million contract to the University of Manchester for the ‘Provision of Independent Research and Advice on Nuclear Graphite’. The ONR records there were three graphite-related inspections by its inspection team in the last twelve months, and the findings appear at the end of this report.
EDF Energy is also required to carry out, and report on, testing of the graphite cores for cracking during periods when nuclear reactors are in statutory outages (those required by regulators for inspections). Most of the AGRs have such outages scheduled between 2024 to 2026. The NFLA Secretary saw reactor operatives carrying out such a test when he visited Heysham on 29 November 2022.
Three AGRs at Dungeness-B, Hinkley Point-B and Hunterston-B have already closed, and are in the process of defueling, but those that remain continue to experience defects during their end-of-life cycle in addition to any cracking of the graphite core moderator.
Dr Paul Dorfman, Chair of the Nuclear Consulting Group, who is often called upon to comment on nuclear power and renewable energy issues by media outlets worldwide, is clear that closure of the AGRs is long overdue:
“All the UK nuclear reactors that EDF want to ‘life extend’ have histories of technical problems – by far the most significant is the cracking of the graphite bricks in the core moderator. The role of the graphite moderator is to slow down the fast neutrons to allow the chain reaction.
“Due to irradiation damage over time, the bricks crack and reactor core distorts. Channels run through the bricks, allowing control rods to shut-down the reactor in an emergency. Because the graphite core can’t be repaired or replaced, this means that core damage is a life-limiting condition.
This is why these reactor’s original operating design life was just 30 years.
“All things considered, much better to be safe than sorry. Shut them down.”
The status and operating history of the AGRs does indeed belie the claim of government ministers and industry supremos that nuclear is a reliable source of electricity generation; indeed, generation at the plants can best be described as ‘intermittent’, a term commonly used by detractors of renewable energy technologies. For interrogation of the EDF Energy website reveals that four of the eight AGRs are currently off-line for unplanned maintenance checks or repairs because of a malfunctioning steam valve at Heysham-1, whilst two more are down for scheduled outages.
In 2022, figures supplied by EDF Energy to the International Atomic Energy Agency show that the AGRs had significant non-availability with lengthy periods of planned or unplanned outages, ranging in total from 1,313 hours at Hartlepool A-2 to 3,967 hours at Heysham A-2. In addition, plant was operating in some instances at a significantly reduced load capacity, indeed down almost to 50% in the cases of Heysham A-2 and Torness-2.
There will doubtless be a point where it will simply be uneconomic for EDF Energy to continue generating electricity at these elderly plants, but Councillor Lawrence O’Neill, Chair of the NFLAs, wonders if EDF Energy’s motivation is in part driven by the need to generate extra income in the medium term given the significant delays in delivering Hinkley Point C:
“Frankly EDF Energy could do with the money from continuing operations at the four AGR plants. Hinkley Point C is being built at EDF’s risk and EDF’s cost. It is massively over budget and hugely behind schedule. It may well not be generating by 2028 or even by 2030, and broadsheet newspapers like The Telegraph and Guardian have recently speculated that the plant may even not be online before 2032. In the meantime, EDF Energy will be haemorrhaging cash”.
The NFLAs would like to acknowledge with thanks the assistance of Professor Stephen Thomas, University of Greenwich, Dr Paul Dorfman, University of Sussex and Mr Pete Roche, NFLA Scotland Policy Advisor in writing this article.
Ends://… For more information please contact NFLA Secretary Richard Outram by email to richard.outram@manchester.gov.uk
Notes for Editors
Current and projected future status of AGR stations
| Start of Construction/
Generation / Estimated Closure Date |
Current Operational Status | Next Statutory Outage | |
| Hartlepool | 1968 /
1983 / March 2026 |
Reactor A-1 – Unplanned shutdown to 31 Jan 2024. Steam valve inspections. | Reactor A-1 – April 2025 |
| Reactor A-2 – Unplanned shutdown to 2 Feb 2024. Steam valve inspections. | Reactor A-2 – None scheduled | ||
| Heysham-1 | 1970 /
1983 / March 2026 |
Reactor A-1 – Unplanned shutdown to 9 Feb 2024. Failure of a steam valve. | Reactor A-1 – None scheduled |
| Reactor A-2 – Unplanned shutdown to 2 Feb 2024. Steam valve inspections. | Reactor A-2 – Sept 2025 | ||
| Heysham-2 | 1980 /
1988 / March 2028 |
Reactor B-1 (also known as Reactor 7) – Planned shutdown to 23 Jan 2024. Engaged in offload refuelling. | Reactor B-1 (7) –
Jan 2025 |
| Reactor B-2 (also known as Reactor 8) – Operational. | Reactor B-2 (8) – April 2026 | ||
| Torness | 1980 /
1988 / March 2028 |
Reactor 1–Planned shutdown to 28 Jan 2024. | Reactor 1 – April 2024 |
| Reactor 2 – Operational. | Reactor 2 – Jan 2026 |
Sources:
https://www.edfenergy.com/about/nuclear/power-stations
https://www.edfenergy.com/energy/power-station/daily-statuses 16 Jan 2024
IAEA Operating Experience with Nuclear Power Stations in Member States, 2023 Edition
| Load Factor | Operating Factor | Planned Outages | Unplanned Outages | |||||
| 2022 | Historical | 2022 | Historical | 2022 | Historical | 2022 | Historical | |
| Hartlepool A-1 | 69.16 | 68.37 | 73.48 | 73.12 | 694 | 1620 | 1628 | 1387 |
| Hartlepool A-2 | 79.28 | 70.27 | 85.01 | 74.97 | 718 | 1484 | 595 | 1130 |
| Heysham A-1 | 83.98 | 67.23 | 84.05 | 73.49 | 669 | 1519 | 728 | 1298 |
| Heysham A-2 | 54.85 | 65.97 | 66.5 | 73.16 | 2461 | 634 | 1506 | 1448 |
| Heysham B-1 | 68.05 | 77.84 | 72.37 | 82.95 | 2056 | 929 | 366 | 422 |
| Heysham B-2 | 77.58 | 77.37 | 82.75 | 82.55 | 1496 | 902 | 16 | 560 |
| Torness-1 | 78.27 | 74.91 | 78.5 | 82.69 | 1810 | 901 | 0 | 315 |
| Torness-2 | 58.05 | 74.15 | 69.04 | 82.60 | 2445 | 831 | 267 | 454 |
LOAD FACTOR is the %-age of electricity generated against the theoretical generating capacity of the reactor.
OPERATING FACTOR is the %-age of time the reactor is generating against the theoretical amount of time it could be generating each year.
PLANNED AND UNPLANNED OUTAGES. The figures for 2022 were the number of hours the reactor was offline that year, and the Historical figure is the average number of hours the reactor was offline in each year of its operation between 1989 and 2022.
Source: www-pub.iaea.org/MTCD/Publications/PDF/OPEX_2023_web.pdf
The three graphite-related ONR inspections that are recorded as having taken place in the last 12-months:
Heysham 1 – Inspection ID: 52880
Executive summary
Date(s) of inspection
- October 2023
Aim of inspection
The objectives of this intervention were:
- To examine the adequacy of the licensee’s arrangements with regards to graphite core inspection during this outage;
- To establish confidence that the various safety case commitments for core inspection and trepanning would be met;
- To consider the quality of the examinations performed, both in terms of data quality and the adequacy of the training and understanding of those involved in the work being carried out.
Subject(s) of inspection
- LC28 – Examination, inspection, maintenance and testing – Rating: Green
Key findings, inspector’s opinions and reasons for judgement made:
The purpose of this intervention was to undertake a Licence Condition (LC) 28 compliance inspection at EDF Energy Nuclear Generation Ltd’s (NGL’s) Heysham 1 (HYA) power station. The intervention took place on 17th October 2023, several weeks after the start of its 2023 periodic shutdown of reactor 1 (R1). The outage was scheduled to complete in early December. The purpose of the intervention was to inspect the adequacy of the licensee’s examinations and inspections of the graphite core and determine compliance with LC 28(1).
This intervention is one of a number of LC28 compliance inspections performed by ONR during the periodic shutdown of HYA R1. These inspections inform the ONR’s decision on whether to issue a licence instrument granting consent for the return to service of HYA R1 following its 2023 statutory outage.
This intervention specifically focused on the arrangements for graphite core examination, inspection and testing and the observations made by ONR specialist graphite inspectors during these periodic shutdown activities. My judgement is based on the findings of the intervention, the quality of the data I observed and the knowledge and experience of the licensee’s staff.
Conclusion
Following my intervention, I consider that the licensee’s arrangements with regards to graphite core inspection during this outage are suitable and adequate. In my opinion, the visual records and the data that I sampled were of adequate quality for NGL to form an accurate judgement.
At the time of my intervention, there was no reason to believe that the safety case requirements would not be met. A forthcoming assessment report will consider whether the results of the graphite core inspections are consistent with the graphite safety case, once the inspection schedule has been completed.
I have allocated an ONR IIS rating of ‘green’ – no formal action.
Heysham 2 – Inspection ID: 52729
Executive summary
Date(s) of inspection:
- June 2023
Aim of inspection
The objectives of this intervention were:
- To examine the adequacy of the licensee’s arrangements with regards to graphite core inspection during this outage;
- To establish confidence that the various safety case commitments for core inspection and trepanning would be met;
- To consider the quality of the examinations performed, both in terms of data quality and the adequacy of the training and understanding of those involved in the work being carried out.
Subject(s) of inspection
- LC28 – Examination, inspection, maintenance and testing – Rating: Green
Key findings, inspector’s opinions and reasons for judgement made
The purpose of this intervention was to undertake a Licence Condition (LC) 28 compliance inspection at EDF Energy Nuclear Generation Ltd’s (NGL’s) Heysham 2 (HYB) power station.
This intervention is one of a number of LC28 compliance inspections performed by ONR during the periodic shutdown of HYB Reactor 8 (R8). These inspections inform the ONR’s decision on whether to issue a licence instrument granting Consent for the return to service of HYB R8 following its 2023 periodic shutdown, as required by LC30(1).
This intervention specifically focused on arrangements for the graphite core examination, inspection and testing. I judged this intervention based on the findings of the intervention, the quality of the data I observed and the knowledge and experience of the licensee’s staff.
Conclusion
Following my intervention, I consider that the licensee’s arrangements with regards to graphite core inspection activities during this outage are suitable and adequate. In my opinion, the visual records and the data that I sampled were of adequate quality for NGL to form an accurate judgement and enable sentencing of the cracks.
At the time of my intervention, there was no reason to believe that the safety case requirements would not be met. A forthcoming assessment report will consider whether the results of the graphite core inspections are consistent with the graphite safety case, once the inspection schedule has been completed.
I have allocated an ONR IIS rating of ‘Green’ – no formal action.
Heysham 2 – Inspection ID: 52664
Executive summary
Date(s) of inspection:
- April 2023
Aim of inspection
The objectives of this intervention were:
- To examine the adequacy of the licensee’s arrangements with regards to the maintenance and calibration of graphite inspection arrangements;
- To establish confidence that the quality and capability to meet various safety case commitments for core inspection and trepanning would be satisfied.
Subject(s) of inspection
- LC28 – Examination, inspection, maintenance and testing – Rating: GREEN
Key findings, inspector’s opinions and reasons for judgement made
The purpose of this intervention was to undertake a Licence Condition (LC) 28 compliance inspection at EDF Energy Nuclear Generation Ltd’s (NGL’s) Heysham 2 (HYB) power station.
This intervention is one of a number of LC28 compliance inspections performed by ONR during the periodic shutdown of HYB Reactor 8 (R8). These inspections inform the ONR’s decision on whether to issue a licence instrument granting Consent for the return to service of HYB R8 following its 2023 periodic shutdown, as required by LC30(1).
This intervention specifically focused on arrangements for the maintenance and calibration of graphite inspection equipment. I judged this intervention based on the findings of the intervention, the quality of the data I observed and the knowledge and experience of the licensee’s staff.
Conclusion
Following my intervention, I consider that the licensee’s arrangements with regards to the maintenance and calibration of graphite inspection equipment during this outage are suitable and adequate.
At the time of my intervention, there was no reason to believe that the safety case requirements would not be met. A forthcoming assessment report will consider whether the results of the graphite core inspections are consistent with the graphite safety case, once the inspection schedule has been completed.
I have allocated an ONR IIS rating of ‘GREEN’ – no formal action.
Source: https://news.onr.org.uk/inspection-records/
1. EDF Energy, UK Nuclear Fleet Stakeholder Update, January 2024
