Challenges ahead for debris removal at Fukushima — NHK World

” This year will mark the 7th anniversary of the nuclear accident at the Fukushima Daiichi plant that occurred in March, 2011. The plant’s operator is hoping to eventually remove fuel debris from the damaged reactors.

Fuel debris is a mixture of melted nuclear fuel and broken reactor parts. Removing the debris is considered to be the biggest hurdle to the decommissioning of the reactors.

Last year, Tokyo Electric Power Company, or TEPCO, investigated the inside of the containment vessels of 3 reactors and confirmed, for the first time, the existence of lumps that are believed to be fuel debris in the No.3 reactor.

TEPCO plans to conduct a fresh probe of the No.2 reactor this month to confirm whether a mass on the floor under the reactor, observed last year, is actually fuel debris.

The government and TEPCO aim to begin removing debris in 2021. They are planning to determine which reactor to start with, and how to conduct the procedure, during fiscal 2019.

Workers will try this year to figure out which details need to be considered in order to make the decision.

Removing the debris requires thorough safety measures. For example, radioactive materials must be prevented from spreading and workers must be protected from exposure to radiation.

This autumn, the operator also plans to start removing spent nuclear fuel rods from the storage pool of the No.3 reactor building. ”

by NHK World

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Fears of another Fukushima as Tepco plans to restart world’s biggest nuclear plant — The Guardian

” If a single structure can define a community, for the 90,000 residents of Kashiwazaki town and the neighbouring village of Kariwa, it is the sprawling nuclear power plant that has dominated the coastal landscape for more than 40 years.

When all seven of its reactors are in operation, Kashiwazaki-kariwa generates 8.2m kilowatts of electricity – enough to power 16m households. Occupying 4.2 sq km of land along the Japan Sea coast, it is the biggest nuclear power plant in the world.

But today, the reactors at Kashiwazaki-kariwa are idle. The plant in Niigata prefecture, about 140 miles (225km) north-west of the capital, is the nuclear industry’s highest-profile casualty of the nationwide atomic shutdown that followed the March 2011 triple meltdown at Fukushima Daiichi.

The company at the centre of the disaster has encountered anger over its failure to prevent the catastrophe, its treatment of tens of thousands of evacuated residents and its haphazard attempts to clean up its atomic mess.

Now, the same utility, Tokyo Electric Power [Tepco], is attempting to banish its Fukushima demons with a push to restart two reactors at Kashiwazaki-kariwa, one of its three nuclear plants. Only then, it says, can it generate the profits it needs to fund the decommissioning of Fukushima Daiichi and win back the public trust it lost in the wake of the meltdown.

This week, Japan’s nuclear regulation authority gave its formal approval for Tepco to restart the Kashiwazaki-kariwa’s No. 6 and 7 reactors – the same type of boiling-water reactors that suffered meltdowns at Fukushima Daiichi.

After a month of public hearings, the nuclear regulation authority concluded that Tepco was fit to run a nuclear power plant and said the two reactors met the stricter safety standards introduced after the 2011 disaster.

Just before that decision, Tepco gave the Guardian an exclusive tour of what it claims will be the safest nuclear plant in the world.

Now, as on the day of the triple disaster that brought widespread destruction to Japan’s northeast coast, Kashiwazaki-kariwa has the look of a working nuclear plant. Just over 1,000 Tepco staff and 5,000-6,000 contract workers provide the manpower behind a post-Fukushima safety retrofit that is projected to cost 680 billion yen ($6.1bn).

They have built a 15-metre-high seawall that, according to Tepco, can withstand the biggest tsunami waves. In the event of a meltdown, special vents would keep 99.9% of released radioactive particles out of the atmosphere, and corium shields would block molten fuel from breaching the reactors’ primary containment vessels. Autocatalytic recombiners have been installed to prevent a repeat of the hydrogen explosions that rocked four of Fukushima Daiichi’s reactors.

Other parts of the sprawling complex are home to fleets of emergency vehicles, water cannon, back-up power generators, and a hilltop reservoir whose 20,000 tonnes of water will be drawn to cool reactors in the event of a catastrophic meltdown.

“As the operator responsible for the Fukushima accident, we’re committed to learning lessons, revisiting what went wrong and implementing what we learned here at Kashiwazaki-kariwa, says the plant’s chief, Chikashi Shitara. “We are always looking at ways to improve safety.

“Because of our experience at Fukushima, we’re committed to not making the same mistakes again – to make the safety regime even stronger. That’s what we have to explain to members of the public.”

‘This is no place for a nuclear power plant’

The public, however, is far from convinced. Last year, the people of Niigata prefecture registered their opposition to the utility’s plans by electing Ryuichi Yoneyama, an anti-nuclear candidate, as governor. Exit polls showed that 73% of voters opposed restarting the plant, with just 27% in favor.

Yoneyama has said that he won’t make a decision on the restarts, scheduled for spring 2019, until a newly formed committee has completed its report into the causes and consequences of the Fukushima disaster – a process that could take at least three years.

For many residents, the plant’s location renders expensive safety improvements irrelevant. “Geologically speaking, this is no place for a nuclear power plant,” says Kazuyuki Takemoto, a retired local councillor and a lifelong anti-nuclear activist.

Takemoto cites instability caused by the presence of underground oil and gas deposits in the area, and evidence that the ground on which Tepco’s seawall stands is prone to liquefaction in the event of a major earthquake.

Local critics have pointed to the chaos that could result from attempting to evacuate the 420,000 people who live within a 30km radius of Kashiwazaki-kariwa. “That’s more people than lived near Fukushima, plus we get very heavy snowfall here, which would make evacuating everyone impossible,” Takemoto adds. “The situation would be far worse than it was in Fukushima.”

Adding to their concerns are the presence of seismic faults in and around the site, which sustained minor damage during a magnitude-6.6 offshore earthquake in 2007. Two active faults – defined by nuclear regulators as one that has moved any time within the last 400,000 years – run beneath reactor No. 1.

But for Tepco, a return to nuclear power generation is a matter of financial necessity, with the utility standing to gain up to ¥200 billion in annual profits by restarting the two reactors at Kashiwazaki-Kariwa.

The bill for decommissioning Fukushima Daiichi, decontaminating neighbourhoods and compensating residents affected by the meltdown could reach 21.5tr yen [$191bn], according to government estimates. That is on top of the money the firm is spending on importing expensive fossil fuels to fill the vacuum left by the nuclear shutdown.

Earlier this year, the Japan Centre for Economic Research said the total cost of the four-decade Fukushima cleanup – including the disposal of radioactive waste from the plant’s three damaged reactors – could soar to between 50-70tr yen.

“As Tepco’s president and our general business plan have made clear, restarting the reactors here is very important to us as a company,” says Shitara.

Much is at stake, too, for Japan’s prime minister, Shinzo Abe, who has put an ambitious return to nuclear power generation at the centre of his energy policy. His government wants nuclear to provide about 20 percent Japan’s electricity by 2030 – a move that would require the restart of about 30 reactors.

Of the country’s 48 operable reactors, only four are currently online. Several others have passed stringent new safety tests introduced in the wake of Fukushima, but restarts have encountered strong local opposition.

As part of the restart process, people across Japan were recently invited to submit their opinions on the Kashiwazaki-kariwa restart and Tepco’s suitability as a nuclear operator.

Kiyoto Ishikawa, from the plant’s public relations department, insists Tepco has learned the lessons of Fukushima. “Before 3-11 we were arrogant and had stopped improving safety,” he said. “The earthquake was a wake-up call. We now know that improving safety is a continuous process.”

The firm’s assurances were dismissed by Yukiko Kondo, a Kariwa resident, who said the loss of state subsidies if the plant were to remain permanently idle was a sacrifice worth making if it meant giving local people peace of mind.

“Tepco caused the 2011 accident, so there is no way I would ever support restarting nuclear reactors here,” she said. “They kept telling us that Fukushima Daiichi was perfectly safe – and look what happened.” ”

by Justin McCurry, The Guardian

source with internal links

Kansai Electric to scrap two reactors in latest blow for Japan’s nuclear sector — Intelligencer

” TOKYO (Reuters) – Kansai Electric Power Co said on Friday it will decommission two 38-year-old reactors at its Ohi nuclear plant as Japan’s electricity industry struggles to cope with new safety standards imposed after the 2011 Fukushima disaster.

The widely expected announcement brings to 14 the number of reactors being scrapped since the meltdowns at the Fukushima Daiichi plant. More than six years on, Japan is still turning away from nuclear power in the face of technical problems, public opposition, court challenges and unfavorable economics.

Most of Japan’s reactors remain shut, with only four operating, while they undergo relicensing processes in a bit to meet new standards set after the Fukushima crisis highlighted shortcomings in regulation.

Kansai Electric will now scrap the No. 1 and No. 2 reactors at the Ohi plant, some 86 kilometers (53 miles) from Osaka, western Japan, where the utility is based. Shut since 2011, the reactors have capacity of 1,175 megawatts each, began operations in 1979 and were near the end of their standard operating life of 40 years.

A Kansai Electric spokeswoman said that costs in meeting the new safety standards were not a factor behind the decision, but technical difficulties were.

“The containment vessels of these reactors are smaller than other reactors in Japan, and a need to beef up the walls to meet the standards would make the work zones even more cramped, making it difficult for prompt repairs in case of troubles,” the spokeswoman said.

The move means Japan is likely to soon be eclipsed by China as the third biggest nuclear power sector in the world – by reactor numbers – after the United States and France.

Japan now has 42 reactors, including the two to be decommissioned at Ohi, compared with 38 in China, which has nearly 20 more under construction, while the U.S. and France have 99 and 58 respectively, according to the International Energy Agency.

Kansai Electric was the most reliant on nuclear energy among Japan’s atomic operators, using reactors for nearly half of its electricity generation before the disaster at the Fukushima nuclear plant in 2011, when reactors melted down following a giant earthquake and tsunami. Two other reactors at the Ohi site remain closed.

While Prime Minister Shinzo Abe’s government is keen to restore a power source that provided about a third of electricity supply before the Fukushima crisis, Japan’s public remains deeply skeptical over industry assurances on safety.

Anti-nuclear campaigners and residents are increasingly using courts to block restarts and push for plants to close.

A Japanese court last week ordered Shikoku Electric Power Co not to restart one of its reactors, overturning a lower court decision in the first instance of a higher court blocking the operation of nuclear plant.

Residents have lodged injunctions against most nuclear plants across Japan. ”

Reporting by Aaron Sheldrick and Osamu Tsukimori; Writing by Aaron Sheldrick; Editing by Kenneth Maxwell

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New proposal suggests removing Fukushima plant’s melted nuclear fuel from side — The Mainichi

” A method to remove melted nuclear fuel debris on the bottom of the containment vessels of Fukushima No. 1 Nuclear Power Plant’s first, second and third reactors from the side was proposed by the Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF) on July 31.

Hajimu Yamana, head of the NDF, which is tasked with considering how to remove fuel debris from the reactors, for the first time explained the organization’s specific method proposal to the heads of local governments at a countermeasures for the decommissioning and handling of the contaminated water council meeting held in Iwaki, Fukushima Prefecture.

The method would focus on prioritizing the removal of debris from the bottom of the vessels from the side, using robotic arms and other remote devices while flushing water over the debris. However, ways to block radiation and countermeasures against the scattering of airborne radioactive dust still remain unsolved. The central government and Tokyo Electric Power Co. (TEPCO) plan to finalize their policy to remove the debris and amend the decommission schedule in September.

In all three of the reactors, contaminated water has collected at the bottom of the containment vessels. The NDF had previously considered a “flooding method” that would fill the containment vessels completely with water to block radiation from leaking. However, measures to repair the containment vessels and prevent leakage of the radioactive water would be difficult, so the plan was put aside for having “too many issues.” “

by The Mainichi

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Japanese robot probes the radioactive water at Fukushima’s nuclear reactor to find melted fuel — Daily Mail

” A Japanese robot has begun probing the radioactive water at Fukushima’s nuclear reactor.

The marine robot, nicknamed the ‘little sunfish’, is on a mission to study structural damage and find fuel inside the three reactors of the devastated plant.

Experts said remote-controlled bots are key to finding fuel at the dangerous site, which has likely melted and been submerged by highly radioactive water.

The probe – about the size of a loaf of bread – is equipped with lights, manoeuvres using tail propellers and collects data using two cameras and a dosimeter radiation detector.

Plant operators chose to send the robot inside the containment vessel of the No. 3 reactor because it has highest known water levels out of the the three reactors.

The robot entered the structure at 6.30am JST (10.30 BST, 5.30 ET) through a pipe connected to the containment vessel.

The marine machine, which was attached to cables, then swam to the area just below the reactor pressure vessel inside to take images.

New images taken by the robot show how parts of the system, including the control rod, have been damaged by radiation.

On Friday, the robot will continue its travels to the bottom of the containment vessels, where melted fuel deposits are believed to have accumulated.

In 2011, a 10-metre-high tsunami that killed nearly 19,000 people crashed into Japan’s Fukushima nuclear power plant, leading to several meltdowns.

Five years after the disaster, researchers are still struggling to clean up the highly dangerous radioactive materials in water of the wasting reactors.

It’s estimated that plant officials have only located 10 per cent of the waste fuel left behind after the nuclear meltdowns.

And the damaged plant is believed to be leaking small amounts of the radioactive waste into the Pacific Ocean, which could be travelling as far as the west cost of the US.

Researchers are now pinning their hopes on the remote-controlled sunfish robot to locate the lost fuel in order to work out the safest way to remove it.

During a demonstration of the device at a test facility near Tokyo last month, the probe slowly slid down from a rail and moved across the water.

A team operated it remotely, with one guiding the robot while another adjusted a cable that transmits data and serves as its lifeline.

Japan hopes to locate and start removing fuel from the reactors after Tokyo’s 2020 Olympics.

In earlier operations, snake and scorpion-shaped robots became stuck inside two reactors.

The scorpion robot’s crawling function failed and it was left inside the plant’s Unit 2 containment vessel.

The other, designed for cleaning debris for the ‘scorpion’ probe, was called back after two hours when two of its cameras stopped working after its total radiation exposure reached 1,000 Sievert – a level that would kill a human within seconds.

The plan had been to use the robot for 10 hours at an exposure level of 100 Sievert per hour.

The swimming robot shown was co-developed by electronics and energy giant Toshiba and the government’s International Research Institute for Nuclear Decommissioning. “

by Daisy Dunne, Mail Online and Associated Press

source with photos and video

Tepco delays robotic surveys at Fukushima nuclear reactors — The Asahi Shimbun

” Tokyo Electric Power Co. has postponed inspections by robots to finally confirm the location and state of melted fuel at two damaged reactors of the Fukushima No. 1 nuclear plant.

The camera-equipped robots were scheduled to enter the containment vessels of the No. 1 and No. 2 reactors within fiscal 2015, which ends in March. But TEPCO said Jan. 28 that a series of unexpected circumstances, such as poor visibility caused by murky radioactive water, have ruined that plan.

The robot for the No. 1 containment vessel will be redesigned, and the remote-controlled survey will be conducted in fiscal 2016, the utility said, without offering a more specific timetable.

Nuclear fuel assemblies in the No. 1 to No. 3 reactors are believed to have melted and fallen to the bottom of the containment vessels following the March 2011 earthquake and tsunami.

Radiation levels inside the containment vessels remain extremely high, making them too dangerous to be approached by workers.

The remote-controlled robotic probe was seen as crucial in determining conditions inside the containment vessels for the eventual decommissioning of the nuclear plant.

TEPCO conducted a preliminary survey using an industrial endoscope in the containment vessel of the No. 1 reactor. It found accumulated waste turned the water murky and blocked the view.

For the No. 2 reactor, TEPCO had planned to locate the melted nuclear fuel using a robot last summer. But decontamination and cleanup work near the entrance to the containment vessel proved difficult. That prevented TEPCO from carrying out robotic survey as planned. ”

by Hiromi Kumai

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