L’évènement de la centrale nucléaire de Taishan révélé ce jour par CNN permet de mettre un coup de projecteur sur le rejet de gaz rares dans l’environnement. Tout d’abord, concernant l’industrie atomique, considérez la formulation « gaz inertes » comme étant de la désinformation car les gaz rares issus d’une centrale nucléaire sont tout sauf inertes ! Inerte, cela signifie inactif. Or la radioactivité, c’est de l’activité : les rayons projettent des particules et de l’énergie dans leur environnement.
Habituellement, on appelle gaz rares, ou gaz nobles, un ensemble de gaz monoatomiques incolores et inodores, chimiquement très peu réactifs, voire totalement inertes pour les deux plus légers. Ce sont l'hélium (He), le néon (Ne), l'argon (Ar), le krypton (Kr), le xénon (Xe) et le radon (Rn), ce dernier étant radioactif, avec une demi-vie de 3,8 jours pour le radon 222, son isotope le plus stable. Ainsi, quand on parle de gaz rares, on parle généralement d’éléments non radioactifs pour la plupart et inertes chimiquement.
Or, dans l’industrie nucléaire, les gaz rares ne sont pas tout à fait les mêmes ! Par exemple, l’isotope radioactif du Xénon, 133Xe, a une demi-vie de près de 5,25 jours, ce qui fait que l’on peut le détecter durant presque deux mois après son émission. Ce fut le cas quand on détecta le xénon radioactif de Fukushima Daiichi, révélant qu’au moins un réacteur avait un problème d’étanchéité. Le krypton radioactif, 85Kr, quant à lui, a une demi-vie de 10,76 années ; de ce fait, il peut encore être détectable un siècle plus tard. C’est ce qui explique sa concentration au pôle nord car la plupart des réacteurs nucléaires sont dans l’hémisphère nord.
Article tiré du Rapport annuel d’information du public relatif aux installations nucléaires du site de Flamanville (2019). EDF prétend que les gaz rares n’interfèrent pas avec les tissus vivants. C’est évidemment faux puisqu’ils sont radioactifs.
Si ces gaz ne sont pas assimilés par l'organisme, ça ne veut pas dire qu'ils ne sont pas dangereux puisqu'ils sont très radioactifs. Quand ils sont produits en masse, ils peuvent être inhalés et provoquer des irradiations internes et externes. On a l’habitude de ne pas prendre en compte ces polluants radioactifs car ils se diluent dans l’air. Ainsi l'évènement atomique qui avait eu lieu au vieux réacteur de Halden (Norvège) avait provoqué en 2016 le rejet en quelques jours de 8,18 Tbq de gaz rares sans que ça n'émeuve personne. Concernant Taishan, la Chine et la France espèrent que les choses en restent là, c’est-à-dire en minimisent l’évènement jusqu’à extinction de l‘intérêt des médias. Mais CNN évoque une fuite, et pour l’EPR qui n’a pas encore pu démontrer son efficacité, c’est le moins qu’on puisse dire, cela change tout. En outre, comme le remarque Stéphane Lhomme (Observatoire du nucléaire), le coup pourrait être fatal pour ce « fleuron de l’industrie française ».
EDF communique de cette manière : "La présence de certains gaz rares dans le circuit primaire est un phénomène connu, étudié et prévu par les procédures d'exploitation des réacteurs". Je traduis : les procédures d’exploitation des réacteurs prévoient un rejet des gaz rares dans l’atmosphère, car on ne peut pas tout traiter. Chaque centrale a ainsi le droit de polluer l’atmosphère avec des gaz radioactifs. Par exemple, la centrale de Bugey a le droit de rejeter jusqu’à 60 TBq (60 000 milliards de becquerels) de gaz rares par an. Autant dire qu’il ne vaut mieux pas être sous le vent d’une centrale nucléaire. Pire encore, le centre atomique de La Hague qui a le droit de rejeter 470 000 TBq de gaz rares chaque année.
L’IRSN, fidèle à son habitude de minimiser les dangers, s’exprime par l’intermédiaire d’une directrice générale adjointe, Karine Herviou : « Contamination du fluide primaire ne veut pas dire rejet dans l'environnement», « Il n'y a pas plus d'inquiétude à avoir pour l'instant, compte tenu de ce qu'on sait.» (Propos relevés par Le Figaro). Encore une fois, mensonge, car tous les réacteurs nucléaires rejettent de la radioactivité dans l’environnement. Et si Framatome contacte les États-Unis pour signaler un « risque radioactif imminent », pourquoi s’inquiéter en effet ?
Carte du bruit de fond artificiel du Xénon 133 dans le monde (Extrait de G. Le Petit - P. Achim - G. Douysset - P. Gross - M. Monfort - C. Moulin / CEA−DAM Île-de-France, « Accident de la centrale nucléaire de Fukushima Dai-ichi : analyse des rejets de radionucléides dans l’atmosphère », revue du CEA Chocs Avancées, 2012)
Revenons à Taishan. Selon CNN, Framatome aurait alerté le département étatsunien de l'Énergie pour l'avertir de la situation. Cette note stipulerait que l'Autorité de sûreté chinoise aurait relevé les limites de détection de la radioactivité aux alentours du site au-dessus des normes de sécurité afin d'éviter d'avoir à stopper la centrale nucléaire. Cela paraît signifier que l’EPR chinois semble polluer l’atmosphère plus que prévu… Pour l’instant, aucune mesure de l’atmosphère n’est communiquée (secret militaire oblige), mais si un nuage radioactif conséquent arrive aux États-Unis, on en entendra peut-être parler. Celui de Fukushima avait mis 4 jours pour atteindre les côtes américaines.
Alors, fuite du confinement primaire ou rejet volontaire ? L’avenir nous le dira peut-être, mais dans les deux cas, on peut s'inquiéter des doses reçues par la population locale.
Illustration d’entête : Cinq tubes à gaz nobles - Alchemist-hp www.pse-mendelejew.de, CC BY-SA 2.0 DE <https://creativecommons.org/licenses/by-sa/2.0/de/deed.en>, via Wikimedia Commons
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Source : CNN
Exclusive: US assessing reported leak at Chinese nuclear power facility
Updated 0742 GMT (1542 HKT) June 14, 2021
(CNN)The US government has spent the past week assessing a report of a leak at a Chinese nuclear power plant, after a French company that part owns and helps operate it warned of an "imminent radiological threat," according to US officials and documents reviewed by CNN.
The warning included an accusation that the Chinese safety authority was raising the acceptable limits for radiation detection outside the Taishan Nuclear Power Plant in Guangdong province in order to avoid having to shut it down, according to a letter from the French company to the US Department of Energy obtained by CNN.
Despite the alarming notification from Framatome, the French company, the Biden administration believes the facility is not yet at a "crisis level," one of the sources said.
While US officials have deemed the situation does not currently pose a severe safety threat to workers at the plant or Chinese public, it is unusual that a foreign company would unilaterally reach out to the American government for help when its Chinese state-owned partner is yet to acknowledge a problem exists. The scenario could put the US in a complicated situation should the leak continue or become more severe without being fixed.
However, concern was significant enough that the National Security Council held multiple meetings last week as they monitored the situation, including two at the deputy level and another gathering at the assistant secretary level on Friday, which was led by NSC Senior Director for China Laura Rosenberger and Senior Director for Arms Control Mallory Stewart, according to US officials.
The Biden administration has discussed the situation with the French government and their own experts at the Department of Energy, sources said. The US has also been in contact with the Chinese government, US officials said, though the extent of that contact is unclear.
The US government declined to explain the assessment but officials at the NSC, State Department and the Department of Energy insisted that if there were any risk to the Chinese public, the US would be required to make it known under current treaties related to nuclear accidents.
Framatome had reached out to the US in order to obtain a waiver that would allow them to share American technical assistance in order to resolve the issue at the Chinese plant. There are only two reasons why this waiver would be granted, and one is an "imminent radiological threat," the same verbiage used in the June 8 memo.
The memo claims the Chinese limit was increased to exceed French standards, yet it remains unclear how that compares to US limits.
"It is not surprising that the French would reach out," according to Cheryl Rofer, a nuclear scientist who retired from Los Alamos National Laboratory in 2001. "In general, this sort of thing is not extraordinary, particularly if they think the country they are contacting has some special ability to help."
"But China likes to project that everything is just fine, all the time," she added.
The US could give permission for Framatome to provide the technical assistance or support to help resolve the issue, but it is the Chinese government's decision whether the incident requires shutting down the plant completely, the documents obtained by CNN indicate.
Ultimately, the June 8 request for assistance from Framatome is the only reason why the US became involved in the situation at all, multiple sources told CNN.
CNN has reached out to the Chinese authorities in Beijing and Guangdong province, where the plant is located, the Chinese embassy in Washington, DC, as well as the state-owned energy group that operates the plant along with the French company. None have responded directly, though China is amidst a three-day national holiday that runs through the end of Monday.
However, the Taishan Nuclear Power Plant published a statement on its website Sunday night local time, maintaining that environmental readings for both the plant and its surrounding area were "normal."
The two nuclear reactors in Taishan are both operational, the statement said, adding that Unit 2 had recently completed an "overhaul" and "successfully connected to the grid on June 10, 2021." The statement did not define why or how the plant was overhauled.
"Since it was put into commercial operation, the Taishan Nuclear Power Plant has strictly controlled the operation of the units in accordance with operating license documents and technical procedures. All operating indicators of the two units have met the requirements of nuclear safety regulations and power plant technical specifications," the statement noted.
In a separate statement Friday, hours after CNN first reached out for comment, Framatome acknowledged the company "is supporting resolution of a performance issue with the Taishan Nuclear Power Plant in Guangdong Province, China."
"According to the data available, the plant is operating within the safety parameters. Our team is working with relevant experts to assess the situation and propose solutions to address any potential issue," the statement added.
Framatome would not directly address the content of the letter to the Department of Energy when asked by CNN.
The letter comes as tensions between Beijing and Washington remain high and as G7 leaders met this weekend in the United Kingdom with China an important topic of discussion. There are no indications the reports of a leak were discussed at a high level at the summit.
A warning from a French nuclear company
The issue first emerged when Framatome, a French designer and supplier of nuclear equipment and services that was contracted to help construct and operate the Chinese-French plant, reached out to the US Department of Energy late last month informing them of a potential issue at the Chinese nuclear plant.
The company, mainly owned by Électricité de France (EDF), a French utility company, then submitted an operational safety assistance request on June 3, formally asking for a waiver that would allow them to address an urgent safety matter, to the Department of Energy, warning American officials that the nuclear reactor is leaking fission gas.
The company followed up with DOE on June 8 asking for an expedited review of their request, according to a memo obtained by CNN.
"The situation is an imminent radiological threat to the site and to the public and Framatome urgently requests permission to transfer technical data and assistance as may be necessary to return the plant to normal operation," read the June 8 memo from the company's subject matter expert to the Energy Department.
Framatome reached out to the US government for assistance, the document indicates, because a Chinese government agency was continuing to increase its limits on the amount of gas that could safely be released from the facility without shutting it down, according to the documents reviewed by CNN.
When asked by CNN for comment, the Energy Department did not directly address the memo's claim that China was raising the limits.
In the June 8 memo, Framatome informed DOE the Chinese safety authority has continued to raise regulatory "off-site dose limits." It also says the company suspects that limit might be increased again as to keep the leaking reactor running despite safety concerns for the surrounding population.
"To ensure off-site dose limits are maintained within acceptable bounds to not cause undue harm to the surrounding population, TNPJVC (operator of Taishan-1) is required to comply with an regulatory limit and otherwise shut the reactor down if such a limit is exceeded," the June 8 memo reads.
It notes that this limit was established at a level consistent with what is dictated by the French safety authority, but "due to the increasing number of failures," China's safety authority, the National Nuclear Security Administration (NNSA) has since revised the limit to more than double the initial release, "which in turn increases off-site risk to the public and on-site workers."
As of May 30, the Taishan reactor had reached 90% of the allegedly revised limit, the memo adds, noting concerns the plant operator may be "petitioning the NNSA to further increase the shutdown limit on an exigent basis in an effort to keep running which in turn would continue to increase the risk to the off-site population and the workers at the plant site."
The NNSA is a semi-autonomous agency in China responsible for enhancing national security through the military application of nuclear and radiation science.
The US State Department came into possession of the June 8 letter and immediately began engaging with interagency partners and with the French government, State Department officials said.
Over the course of 48-72 hours, the US government has been in repeated contact with French officials and US technical experts at DOE, State Department officials said, noting that this flurry of activity was due to the June 8 letter.
Subsequently, there were several urgent questions for the French government and Framatome, they added. CNN has reached out to the French embassy in Washington for comment.
Still, Rofer, the retired nuclear scientist, warns that a gas leak could indicate bigger problems.
"If they do have a gas leak, that indicates some of their containment is broken," Rofer said. "It also argues that maybe some of the fuel elements could be broken, which would be a more serious problem."
"That would be a reason for shutting down the reactor and would then require the reactor to be refueled," Rofer told CNN, adding that removing the fuel elements must be done carefully.
For now, US officials do not think the leak is at "crisis level," but acknowledge it is increasing and bears monitoring, the source familiar with the situation told CNN.
While there is a chance the situation could become a disaster, US officials currently believe it is more likely that it will not become one, the source added.
China has expanded its use of nuclear energy in recent years, and it represents about 5% of all power generated in the country. According to China Nuclear Energy Association, there were 16 operational nuclear plants with 49 nuclear reactors in China as of March 2021, with the total generation capacity of 51,000 megawatts.
The Taishan plant is a prestige project built after China signed a nuclear electricity generation agreement with Électricité de France, which is mainly owned by the French government. The construction of the plant started in 2009, and the two units started generating electricity in 2018 and 2019, respectively.
The city of Taishan has a population of 950,000 and is situated in the southeast of the country in Guangdong province, which is home to 126 million residents and has a GDP of $1.6 trillion, comparable to that of Russia and South Korea.
CNN's Kylie Atwood, Kristen Holmes, Yong Xiong and Shanshan Wang contributed to this report.
Source : The Australian
French nuclear firm Framatome seeks to fix ‘performance issue’ at Taishan plant in China
- By Afp
- June 14, 2021
A French nuclear firm says it is working to resolve a “performance issue” at a plant it part-owns in China’s southern Guangdong province following a US media report of a potential leak there.
CNN reported earlier that the US government is assessing a report of a leak at the Taishan Nuclear Power Plant after the French company, Framatome, warned of an “imminent radiological threat”.
Framatome — a subsidiary of French energy giant EDF — said in a statement on Monday that it is “supporting resolution of a performance issue” at the plant.
“According to the data available, the plant is operating within the safety parameters,” the company said.
EDF later said that there was an “increase in the concentration of certain noble gases in the primary circuit of reactor no. 1” at Taishan, referring to a part of the reactor’s cooling system.
Noble gases are elements like argon, helium and neon which have low chemical reactivity.
Their presence in the system “is a known phenomenon, studied and provided for in the reactor operating procedures,” EDF said.
The firm added it had requested an extraordinary meeting of the power plant’s board “for management to present all the data and the necessary decisions”.
Citing a letter from Framatome to the US energy department, CNN said the warning included an accusation that the Chinese safety authority was raising the acceptable limits for radiation outside the facility in order to avoid having to shut it down.
But a US official told the broadcaster that “the Biden administration believes the facility is not yet at ‘crisis level’”.
The operator of the power station, state-owned China General Nuclear Power Group, said in a statement on Sunday night that “the environmental indicators of Taishan Nuclear Power Plant and its surroundings are normal”.
It did not reference any leak or incident at the power station, which it said meets “the requirements of nuclear safety regulations and power plant technical specifications.”
The news service Agence France-Presse did not get an immediate response to a request for comment from either the Chinese foreign ministry or the Chinese nuclear power group.
Powered up in 2018, the Taishan plant was the first worldwide to operate a next-generation EPR nuclear reactor, a pressurised water design that has been subject to years of delays in similar European projects in Britain, France and Finland.
There are now two EPR power units at the plant in the city of Taishan, which sits close to the coastline of southern Guangdong — China’s most populous province.
EPR reactors have been touted as promising advances in safety and efficiency over conventional reactors while producing less waste.
French Prime Minister Jean-Marc Ayrault visited the Taishan plant in 2013, on a trip where the French leader shopped his country’s nuclear expertise to the massive China market.
Nuclear plants supplied less than 5 per cent of China’s annual electricity needs in 2019, according to the National Energy Administration, but this share is expected to grow as Beijing attempts to become carbon neutral by 2060.
China has 47 nuclear plants with a total generation capacity of 48.75 million kilowatts — the world’s third-highest after the US and France — and has invested billions of dollars to develop its nuclear energy sector.
Last month Russian President Vladimir Putin and his Chinese counterpart, Xi Jinping, hailed close ties between their countries as they launched work on Russian-built nuclear power plants in China.
And in December state media reported that China had successfully powered up its “artificial sun” nuclear fusion reactor for the first time — the HL-2M Tokamak reactor — which uses a powerful magnetic field to fuse hot plasma and can reach temperatures of over 150 million degrees Celsius.
It is China’s largest and most advanced nuclear fusion experimental research device, and scientists hope that the device can potentially unlock a powerful clean energy source.
Mise à jour : 14/06/2021 23h21