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Grande Bretagne : Hunterston : découverte de nouvelles fissures sur les deux réacteurs




9 janvier 2019


Suite à sa découverte de nouvelles fissures sur ses réacteurs écossais, EDF Energy a déclaré avoir reporté à nouveau leurs redémarrages.
Pour le réacteur B3, fermé depuis le 9 mars 2018, l’électricien estime qu’il existe 370 fissures majeures dans son cœur en graphite (nombre extrapolé à partir d’une exploration d’un quart du cœur)
Ce nombre violerait les limites de sécurité.
Pour le réacteur B4, fermé pour sa part le 2 octobre 2018, ce sont encore 200 fissures qui ont été estimées par EDF.
Les autorités locales organisent des réunions d’information avec des scientifiques comme le docteur Ian Fairlie. Les experts ont demandé que les réacteurs restent fermés plutôt que de risquer la survenue d’un accident et qu’un travail soit porté sur de nouveaux emplois dans le comté de Ayrshire ou se trouve la centrale.
Pour I. Fairlie, les autorités doivent fermer les réacteurs qui ne peuvent pas être réparés. Pour lui, même avec un risque faible, il faut tenir compte du pire des scénarios possible avec la contamination radioactive et l’évacuation de Glasgow et d’Édimbourg.
EDF pense toujours pouvoir redémarrer le réacteur B4 à la fin du mois de mars 2019 et le réacteur B3 à la fin du mois d’avril.
Tout en regrettant de n’avoir pas pu prendre la parole lors de la réunion d’échanges qui s’est tenue à Holyrood au sujet des problèmes des réacteurs, le porte parole d’EDF Energy a affirmé qu’il n’était pas question pour sa société de faire fonctionner Hunterston B ni aucune des centrales nucléaires d’EDF dans des conditions dangereuses.

La porte-parole a également souligné qu’EDF devait encore exploiter les réacteurs de Hunterston jusqu’en 2023 (soit 17 ans de plus que prévu). Le 2 novembre, EDF a soumis à l’Office de la réglementation nucléaire (ONR) un dossier de sûreté demandant l’autorisation de remettre en service le réacteur quatre et l’électricien prépare également le dossier de sûreté du réacteur trois.
Le représentant de l’Office de la réglementation nucléaire a confirmé avoir reçu une demande pour le réacteur 4 et précise qu’une équipe d’inspecteurs est en train d’évaluer le dossier de sécurité. Le représentant indique également qu’il n’autorisera la remise en service du réacteur que si l’office est convaincu qu’il est sûr. Pour ce qui concerne le réacteur B3, l’ONR n’a pas reçu le dossier de sûreté, mais continue de surveiller son évolution.

Type : GCR - Puissance : 1 540 MWth - Première divergence : B1 : 01 /1976 - B2 : 03 / 1977

Avalaible in english only


More cracks found in Hunterston nuclear power reactors

Rob Edwards on January 9, 2019

Pressure is mounting to keep two nuclear power reactors at Hunterston in North Ayrshire closed after the company that runs them, EDF Energy, said it had found more cracks and was again postponing plans to restart.

The French company now estimates that there are 370 major cracks in the graphite core of reactor three and 200 cracks in the core of reactor four. Reactor three has been closed down since 9 March 2018, and reactor four since 2 October.

The day after The Ferret revealed in November that 350 cracks had been discovered in reactor three in breach of an operating safety limit, EDF postponed restarting both reactors to January and February.
The ferret subscribe narrow

But there’s been a further delay, with the company now hoping to restart reactor four at the end of March and reactor three at the end of April.

On 9 January the group of nuclear-free local authorities held a safety briefing on Hunterston for MSPs in the Scottish Parliament. Experts called for the reactors to stay closed rather than risking a nuclear accident, and for new jobs to be created in Ayrshire.

Nuclear policy consultant, Dr Ian Fairlie, argued that the increasing number of cracks in the ageing reactors spelled their end. “There is only one thing you can do and that is close them, as they cannot be repaired,” he told The Ferret.

“Although the risks of a major adverse event at Hunterston are relatively small, one has to take into account what the worst case scenario could be, and that is pretty serious indeed – the radioactive contamination and evacuation of both Glasgow and Edinburgh.”

Fairlie urged the Scottish Government to take a more pro-active stance. “It needs to take a good look at the risks here and to decide whether it is really worthwhile running them,” he said. “After all we don’t need their electricity, though we need to ensure that jobs are safeguarded.”

The two reactors at Hunterston B nuclear power station started generating electricity in 1976 and can provide up to 20 per cent of Scotland’s electricity. They were originally due to close in 2006, but EDF wants to keep them going until at least 2023.

But the prolonged closures caused by the discovery of more cracks than expected have cast doubt over the reactors’ future. The cracks in the base of key slots in core graphite blocks are caused by intense radiation bombardment over decades.

One has to take into account what the worst case scenario could be, and that is pretty serious indeed - the radioactive contamination and evacuation of both Glasgow and Edinburgh.
Dr Ian Fairlie, nuclear consultant

Fairlie has warned that the blocks could split and, in some circumstances, cause meltdown and a major release of radioactivity. But this claim has been denied by EDF, which insisted the reactors were safe to operate.

The company is requesting permission from the UK government safety watchdog, the Office for Nuclear Regulation, to start up the reactors again. The regulator says it will only authorise further operation of the reactors if they are “demonstrably safe”.

In its latest update, EDF disclosed that it had inspected a quarter of the core of reactor three and found 100 cracks. “Using modelling to project the number of cracks across the whole reactor our best estimate of the current number of cracks is around 370,” it said.

“This takes the core over the operational limit of 350 contained in the existing safety case for that period of operation – although it’s important to remember that we always set conservative operational limits which are well below what would be considered safe.”

The company also said it had inspected 10 per cent of the core of reactor four and found 30 cracks. When modelled across the core, this meant that “our best estimate of the current number of cracks is around 200.”

EDF added : “The principal safety consequence is how the core responds to a highly unlikely extreme earthquake scenario. Crack opening and core distortion are more relevant to every day operation and in both reactors all these are within existing limits.”

In another update the company confirmed that it was again delaying planned restart dates for both reactors. “Our current estimate is that reactor four will now return at the end of March 2019 and reactor three will be back online at the end of April,” it said.

The vice-convener of the nuclear-free local authorities’ Scotland forum, SNP Renfrewshire councillor Audrey Doig, was concerned that proliferating cracks could compromise reactor safety. “This makes it clear that it is difficult for the nuclear regulator to approve a safety case for the resumption of the reactors,” she said.

The parliamentary briefing on Hunterston was chaired by the Green MSP, Ross Greer. “Long running safety and job concerns from the community around Hunterston have increased quite significantly in recent months, as news from the site only gets worse,” he said.

“We will discuss how to ensure a just transition, protecting and indeed growing the number of local jobs.”

The Edinburgh-based nuclear consultant, Peter Roche, argued that Ayrshire could learn from job-creation projects in Caithness where the Dounreay nuclear complex is being decommissioned. “Whatever happens a host of social interventions will be essential to create new jobs in Ayrshire,” he said.

EDF Energy complained that it had not been invited to speak at the meeting in Holyrood. “It’s unfortunate that we received no response to our offer to speak at this meeting,” said a company spokeswoman.

There is no question of Hunterston B or any of our nuclear stations ever operating in an unsafe condition.
Spokeswoman, EDF Energy

“If we had been able to provide some balance to the discussion, we would have emphasised that there is no question of Hunterston B or any of our nuclear stations ever operating in an unsafe condition. Our strategy is progressing well and we are engaging positively with the Office for Nuclear Regulation (ONR) throughout this complex programme of work.”

The spokeswoman stressed that EDF still expected to operate the Hunterston reactors until 2023. “On 2 November we submitted a safety case to the ONR seeking approval for return to service of reactor four and are also preparing to submit the safety case for reactor three,” she added.

“These must demonstrate that, for the next period of operation, the reactor will operate and shutdown safely during normal operation and during a highly unlikely earthquake scenario.”

ONR confirmed that it had received a bid for a return to service of reactor four. “This safety case is being fully assessed by a team of inspectors and permission will only be granted for the reactor to return to service if we are satisfied that it is safe to do so,” said a spokesperson.

“We will publish our assessment in due course. We have not received the safety case for reactor three, but we continue to monitor its development.”

The ONR spokesperson added : “Re-start will only occur once we have assessed the appropriate safety cases and are satisfied that, from a public and worker perspective, further operation of the reactors is demonstrably safe.

“Whilst ONR is not involved in the meeting being held at the Scottish Parliament, we do engage with a wide range of stakeholders including the Scottish Government and the nuclear-free local authorities.”

This story was updated at 16.00 on 9 January 2019 after the meeting at the Scottish Parliament had taken place. On the same day the Scottish Government also answered a parliamentary question on meetings with the Office for Nuclear Regulation about Hunterston, saying that the minister, Paul Wheelhouse, will meet again with the regulator on 21 February 2019. Photo thanks to Scotia, CC BY-SA 3.0.

De : https://theferret.scot/cracks-hunterston-reactors/


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