Debris to be removed from side of Fukushima reactors

_w850.jpgWorkers wearing protective suits and masks work on the No. 2 reactor building at the Fukushima Daiichi nuclear power plant.

 

TOKYO – A state-backed entity tasked with supporting the decommissioning of the Fukushima nuclear power station proposed Thursday that melted fuel be removed from the side of three of the crippled reactors as part of the process to scrap the complex.

Based on a formal proposal, the government and the plant operator Tokyo Electric Power Company Holdings Inc (TEPCO) will determine specific approaches to carry out the process on each reactor next month and update the plant decommissioning road map.

Under its strategic plan for 2017, the Nuclear Damage Compensation and Decommissioning Facilitation Corp called for the removal of the fuel by partially filling the three reactors with water to cover some of the nuclear debris while allowing access to carry out the work.

The entity also pointed out that the decommissioning work requires phased efforts while maintaining flexibility, as the project still faces many uncertainties.

The extraction work from the Nos. 1-3 reactors at the Fukushima Daiichi nuclear complex, which suffered meltdowns following the massive 2011 earthquake and tsunami disaster, is seen as the most difficult step toward the ultimate goal of decommissioning the entire complex, set to take at least 30 to 40 years to complete.

The government and TEPCO are currently aiming to start the extraction work from 2021.

Under the plan, the Nuclear Damage Compensation and Decommissioning Facilitation body proposed using a remotely controlled apparatus to shave debris from the underside of the lower section of the reactors’ containment vessel while controlling the level of water.

Debris remains not only in the reactors’ pressure vessel but also piled and scattered at the bottom of the containment vessel that houses the reactor vessel.

As for debris left in the reactors’ pressure vessel, the entity will consider removing it from the upper part of the reactors, it said.

The decommissioning body had previously considered a strategy to fill the containment vessel with water as water is effective in containing radiation, but it has shelved the idea as the reactor containers are believed to have been damaged and would leak.

Following a magnitude-9.0 earthquake in March 2011, tsunami inundated the six-reactor plant, located on ground 10 meters above sea level, and flooded power supply facilities.

Reactor cooling systems were crippled and the three reactors suffered fuel meltdowns, while hydrogen explosions damaged the buildings housing the Nos. 1, 3 and 4 reactors.

The Nuclear Damage Compensation and Decommissioning Facilitation entity was established after the Fukushima crisis, the worst nuclear disaster since Chernobyl, to help the utility pay damages. The state-backed entity holds a majority stake in the operator.

https://japantoday.com/category/national/Debris-to-be-removed-from-side-of-Fukushima-reactors

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Muscle robots’ being developed to remove debris from Fukushima reactors

Hitachi-GE testing variety of simply structured, radiation-resistant equipment

20170818_Fukushima-reactor_article_main_image.jpgThe Unit 1 reactor building at the Fukushima Dai-ichi nuclear power plant of the Tokyo Electric Power Co. (TEPCO) in Okuma town, Fukushima prefecture, June 21, 2017.

 

TOKYO — A joint venture between Japanese and American high-technology power houses Hitachi and General Electric is developing special robots for removing nuclear debris from the Fukushima Daiichi nuclear power plant, the most difficult task in decommissioning the plant’s six reactors, three of which suffered core meltdowns in the March 2011 accident.

The machines under development by Hitachi-GE Nuclear Energy are called “muscle robots,” as their hydraulic springs operate like human muscles. The company, based in Hitachi, Ibaraki Prefecture, is stepping up efforts to complete the development project in time for the start of debris removal in 2021.

Hitachi-GE is testing the arms of the robots at a plant of Chugai Technos, a Hiroshima-based engineering service company, located a 30-minute drive from the center of the city. The testing is taking place in a structure with a life-size model of the primary containment vessel of the No. 1 reactor at the Fukushima plant. The robots awkwardly move about, picking up concrete lumps standing in for fuel debris.

“The robots are based on a concept completely different from those of conventional robots,” said Koichi Kurosawa, a senior Hitachi-GE engineer heading the development project. Hydraulics are being used because electronics cannot survive in the extreme environment inside the reactors.

“Asked if the robots are applicable to other nuclear power plants, I would say the possibility is low,” Kurosawa said, noting that the robots are designed to work amid intense radiation.

New challenges

While Hitachi-GE has built many nuclear reactors, it is encountering a variety of new challenges in developing the muscle robots simply because of the tough work required to retrieve fuel debris.

In the nuclear accident caused by the March 2011 earthquake and tsunami, cooling the fuel rods became impossible, and melted uranium fuel dropped from them. Some of the fuel broke through nuclear reactor pressure vessels and solidified as fuel debris containing uranium and plutonium.

The debris is estimated to weigh more than 800 tons in total. The insides of the PCVs at the Fukushima plant are directly exposed to the debris and are emitting radioactivity strong enough to kill a human within a few minutes.

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The International Research Institute for Nuclear Decommissioning, a Tokyo-based research institute for decommissioning nuclear plants, and three reactor makers — Hitachi-GE, Toshiba and Mitsubishi Heavy Industries — have been attempting to ascertain conditions inside the reactor buildings at the Fukushima plant by means of camera- and dosimeter-equipped equipment.

https://asia.nikkei.com/Tech-Science/Science/Muscle-robots-being-developed-to-remove-debris-from-Fukushima-reactors

Fukushima nuke plant decommissioning still has long way to go

 

Mainichi Shimbun reporters visited the Fukushima No. 1 Nuclear Power Plant on July 27. While the working environment at the station has improved, plant operator Tokyo Electric Power Co. (TEPCO) still has a mountain of problems to tackle, such as removing melted nuclear fuel from the No. 1 to No. 3 reactors and treating contaminated water.

https://mainichi.jp/english/articles/20170811/p2a/00m/0na/025000c

Japan’s nuclear safety chief raps Tepco’s attitude on Fukushima No. 1 crisis, restarting other reactors

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The head of the Nuclear Regulation Authority told Tepco’s top management he questions their attitude toward decommissioning the Fukushima No. 1 nuclear power plant and the company’s ability to resume operating its other reactors.

I feel a sense of danger,” NRA Chairman Shunichi Tanaka said during a special meeting Monday with the top management of Tokyo Electric Power Company Holdings Inc.

Tanaka also said Tepco does “not seem to have the will to take the initiative” toward decommissioning the crippled nuclear power station that suffered three reactor meltdowns in March 2011.

Tepco Chairman Takashi Kawamura and President Tomoaki Kobayakawa attended the meeting. The authority felt it is necessary to hear from the top executives before it could make a decision on whether to approve Tepco’s plan to resume operation of reactors 6 and 7 at its massive Kashiwazaki-Kariwa plant in Niigata Prefecture.

Tepco filed for a safety assessment of the two reactors in September 2013 to reactivate them, hoping to restore its financial condition as it needed massive funds to pay compensation related to the Fukushima disaster and to scrap the plant.

The NRA’s safety screening found that Tepco failed to report insufficient earthquake resistance for an emergency response center at the Niigata complex even though it knew about the insufficiency for three years.

In June, Tepco submitted to the watchdog its revised safety measures for the Kashiwazaki-Kariwa complex.

An operator lacking the will to take the initiative does not have the right to resume operation of nuclear reactors,” Tanaka said.

Tepco’s chairman responded by saying: “There are citizens who believe nuclear power is necessary. Operating reactors is our responsibility.”

But Kawamura also admitted there is room for only two more years’ worth of space in the tanks to accommodate the contaminated water building up at Fukushima No. 1.

During the meeting the NRA asked Tepco’s management about the company’s safety measures for the Niigata complex — the biggest nuclear power station in the world — as well as its safety awareness.

Tanaka said the NRA does consider Tepco’s responses at the meeting as sufficient and requested that it submit further explanations on its plan to decommission Fukushima No. 1 and resume operation of the two reactors at Kashiwazaki-Kariwa.

Tanaka plans to conduct on-site checkups at the two reactors, saying, “Tepco, which caused the (Fukushima) accident, is not an ordinary operator.”

The two boiling water reactors at the Niigata plant are the same type that suffered core meltdowns at Fukushima No. 1, and no such reactors have cleared the authority’s safety screening since the 2011 crisis.

http://www.japantimes.co.jp/news/2017/07/10/national/japans-nuclear-safety-chief-raps-tepcos-attitude-fukushima-no-1-crisis-restarting-reactors/

TEPCO vows decommissioning of Fukushima N-plant

A TEPCO logo is pictured on a sign showing the way to the venue of the company's annual shareholders' meeting in Tokyo

FUKUSHIMA (Jiji Press) — The new leaders of Tokyo Electric Power Company Holdings Inc. told Fukushima Gov. Masao Uchibori on Monday of their resolve to promote the decommissioning of the company’s disaster-crippled Fukushima No. 1 nuclear power plant.

There is no change at all that Fukushima is our basic focus,” TEPCO Chairman Takashi Kawamura said to Uchibori at a meeting in the prefectural government office, after explaining that TEPCO’s new management team was launched after approval at a general meeting of its shareholders on Friday.

Kawamura said, “We will proceed safely and steadily with the decommissioning work for the Fukushima No. 1 plant,” where a serious nuclear accident occurred after the March 2011 major earthquake and tsunami in northeastern Japan. The prefecture hosts the plant.

Meanwhile, Uchibori said the people of Fukushima Prefecture strongly want all reactors at TEPCO’s Fukushima No. 2 nuclear power plant, also located in the prefecture, to be decommissioned, the same as they want the decommissioning of the Fukushima No. 1 plant and the implementation of accident compensation plans.

Since the 2011 disaster, TEPCO has halted all four reactors at the No. 2 plant. The Fukushima prefectural assembly and the assemblies of all 59 municipalities in Fukushima have adopted resolutions calling on the company to decommission the No. 2 plant or taken similar steps.

http://the-japan-news.com/news/article/0003784590

Decommissioning of Monju Fast-Breeder Reactor Accepted by Fukui Governor

Capture du 2017-06-07 23-03-30.pngThe Monju prototype fast-breeder reactor in Tsuruga, Fukui Prefecture

 

Fukui governor accepts decision to decommission Monju reactor

Fukui Governor Issei Nishikawa has ditched his opposition to the central government’s plans to decommission the Monju prototype fast-breeder reactor in his prefecture.

Nishikawa had criticized Tokyo for deciding to decommission the reactor in Tsuruga without offering adequate assurances to local residents about such a massive project.

But during a meeting held at the prime minister’s office in Tokyo early June 7, he said, “Decommissioning of the Monju fast-breeder reactor is inevitable.”

At the meeting, attended by relevant Cabinet ministers, the government presented Nishikawa with a basic policy to remove spent nuclear fuel from the reactor in five and a half years and complete decommissioning in 30 years.

Hirokazu Matsuno, the science and technology minister, explained that the basic policy includes a plan to transfer spent nuclear fuel outside the prefecture as demanded by Fukui prefectural authorities.

The government will soon formally adopt the basic policy on decommissioning. The Japan Atomic Energy Agency, which operates the Monju reactor, will then draft its own plan for the project.

The government decided to decommission Monju at the end of last year and was initially expected to present the basic plan in April. However, Nishikawa had been airing concerns about the decommissioning.

http://www.asahi.com/ajw/articles/AJ201706070036.html

Fukui governor approves scrapping of Monju reactor

The governor of Fukui in central Japan has consented to dismantling the prototype fast-breeder nuclear reactor in the prefecture.
The Japanese government decided in December to scrap the Monju reactor over a period of 30 years, following a series of safety management problems. It cited rising costs.
Governor Issei Nishikawa had opposed the plan, expressing concerns about the safety of the dismantling process.
Nishikawa met with Chief Cabinet Secretary Yoshihide Suga and science minister Hirokazu Matsuno on Wednesday in Tokyo.
Matsuno explained the basic plan for scrapping the reactor. The science minister said spent nuclear fuel and sodium coolant would be moved out of the prefecture in future.
He also said the government will come up with a development plan for the host city of Tsuruga by the next fiscal year. He said this would make the city a hub of nuclear research and personnel training.
Governor Nishikawa said he confirmed the government’s basic plan for decommissioning and revitalizing the community. He said he had no choice but to accept the decommissioning. He emphasized that the process be carried out safely.

https://www3.nhk.or.jp/nhkworld/en/news/20170607_15/

Submersible Crawling Robot to Examine Interior of Fukushima Daiichi-3 PCV before Fuel Debris Is Removed

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On May 25, the Tokyo Electric Power Co. (TEPCO) released a status report on the ongoing decommissioning work at the Fukushima Daiichi Nuclear Power Plants, which suffered a tsunami-caused meltdown in March 2011.

Starting two months ago, in March, a self-propelled robot has been used to investigate the interior of the primary containment vessel (PCV) of Unit 1 at Fukushima Daiichi—a necessary step before fuel debris can be removed. As of April 6, the robot had sampled deposits twice.

Fluorescent X-ray spectroscopy has now confirmed the presence of elements that had originally existed in the PCV, such as iron and nickel within the reactor core internals, stainless steel in the heat-insulating materials, zinc in the paint, and lead in the shielding materials.

Although uranium was confirmed as the primary radioactive nuclide within Unit 1, it is not necessarily part of the fuel debris there, given that that element exists naturally. TEPCO said that it would carry out more detailed analyses to confirm the uranium’s source.

As the water level in the PCV of Unit 3 is higher than that in Units 1 and 2, its so-called “X-6 penetration”—which would give easier access to the inside of the pedestal (under the reactor pressure vessel)—is submerged. TEPCO plans to investigate the interior of that unit’s PCV at an undetermined date this summer using a submersible robot that can both crawl and swim. Earlier this month, the power utility began taking measurements using muon observation technology to determine the location of fuel debris.

Under the “Mid-and-Long-Term Roadmap” toward decommissioning, TEPCO will determine policies on fuel debris removal at each Fukushima Daiichi unit this summer. According to its May 22 report to an expert panel of the Nuclear Regulation Authority (NRA), the power company has already made investigations to determine general conditions inside the individual PCVs.

TEPCO will continue to focus on gathering information during the current fiscal year (ended March 31, 2018), including that on the forms and distribution of fuel debris—necessary to determine the means to remove it—and safety measures for the actual removal work.

http://www.jaif.or.jp/en/submersible-crawling-robot-to-examine-interior-of-fukushima-daiichi-3-pcv-before-fuel-debris-is-removed/