Finding and removing melted fuel rods at Fukushima No. 1 — Nikkei Asian Review, The Japan Times

Nikkei Asian Review, “Survey fails to find melted rods at Fukushima reactors”:

” TOKYO — A remote survey of the Fukushima Daiichi nuclear plant’s No. 1 reactor was unable to locate and photograph melted nuclear fuel, Tokyo Electric Power Co. Holdings said Thursday, complicating efforts to remove that material as part of an extensive cleanup.

Tepco on Saturday sent a robot equipped with a camera into the containment vessel for the No. 1 unit. The majority of fuel rods have melted through the unit’s pressure vessel since the plant was struck by the March 11, 2011, earthquake and tsunami. The prevailing view has been that those melted fuel rods are now sitting under 2.5m of water at the bottom of the containment vessel.

The plan was to explore the bottom section by dipping a camera into the pool of water for the first time. But unexpected barriers such as pipes kept the camera around 1 meter from the bottom in most of the 10 positions surveyed instead of the intended depth of about 40cm from the bottom. While the camera was able to capture sand-like sediment, there was no trace of the melted fuel rods. Adding a fifth day to the investigation turned up no further evidence.

Yuichi Okamura, acting general manager of Tepco’s onsite nuclear power division, offered few comments at the utility’s Thursday news conference, saying only that “photographs and radiation data will need to be evaluated in conjunction with one another.”

The timeline set by Tepco and the government for decommissioning the Fukushima plant aims to begin extraction of melted-down material from the No. 1, No. 2 or No. 3 reactor in 2021 or earlier. An extraction plan is to be decided this summer. But the fact that the status of the melted rods still remains unknown underscores the seriousness of the accident.

The results of the robot survey were “limited,” according to Masanori Naitoh, director of nuclear safety analysis at the Institute of Applied Energy’s Nuclear Power Engineering Center. “It would be difficult to set a plan for extraction based on the information from this survey alone.”

An investigation of the No. 2 reactor also fell short, with the survey robot unable to reach the targeted spot right under the unit’s pressure vessel. ”

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The Japan Times, “Tepco’s biggest hurdle: How to remove melted fuel from crippled Fukushima reactors”:

” Six years after the triple meltdown at the Fukushima No. 1 nuclear power plant, recent investigations underneath the damaged reactor 2 using cameras and robots came close to identifying melted fuel rods for the first time.

Experts say getting a peek inside the containment vessel of reactor 2 was an accomplishment. But it also highlighted how tough it will be to further pinpoint the exact location of the melted fuel, let alone remove it some time in the future.

The biggest hurdle is the extremely lethal levels of radiation inside the containment vessel that not only prevent humans from getting near but have also crippled robots and other mechanical devices.

Safely removing the melted fuel would be a best-case scenario but the risks and costs should be weighed against the option of leaving the melted fuel in the crippled reactors, some experts said.

“The work to probe inside the containment vessels and remove the fuel debris will be extremely tough because of the high radiation levels,” said Hiroshi Miyano, who heads a panel of the Atomic Energy Society of Japan, which is discussing ways to decommission the Fukushima plant and making recommendations to the government.

The government and Tokyo Electric Power Company Holdings Inc. are trying to find a way to remedy the situation but existing methods and technologies may not be sufficient, Miyano said.

In search of melted fuel

The world’s attention turned to the melted fuel rods in late January when Tepco inserted a 10-meter-plus tube equipped with a camera into the containment vessel of reactor 2 to capture images under the pressure vessel that housed the fuel rods.

The images showed black lumps scattered beneath the pressure vessel.

When the March 11, 2011, Great East Japan Earthquake and monstrous tsunami hit, the plant suffered a blackout and lost its key cooling system, triggering meltdowns in reactors 1, 2 and 3. The melted nuclear fuel rods penetrated the pressure vessels and fell into the containment vessels.

Tepco had put cameras inside the containment vessels several times in the past six years but January’s probe was the first to apparently find melted fuel debris.

“We understand that this is a big milestone. We could finally get to see what it was like underneath the pressure vessel,” said Yuichi Okamura, general manager of Tepco’s nuclear power and plant siting division.

“This is critical information in order to remove the fuel debris.”

Radiation barrier

But Tepco hasn’t confirmed that the black lumps are melted fuel, saying they could be paint or cable wrappings, and further investigation is needed.

Capturing the images may be progress but the robot and camera forays have not provided enough information about how to deal with the melted fuel.

Last month, Tepco sent a remote-controlled, scorpion-shaped robot in to further probe inside the reactor 2 containment vessel. But the robot failed before it reached under the pressure vessel after a tire became stuck.

The robot’s dosimeter measured radiation levels of 210 sieverts per hour — enough to kill humans instantly.

While 210 sieverts per hour indicate the melted fuel was nearby, the radiation crippled the robot’s electronics, including its semiconductors and cameras, indicating that the further use of robots to pinpoint the melted fuel will be difficult, robotics experts said.

There are computer chips “designed to withstand a certain level of radiation, but the level inside the containment vessel is totally different,” said Satoshi Tadokoro, a professor at Tohoku University who is an expert on disasters and rescue robots.

The radiation can damage a robot’s chips that serve as their brains, causing the devices to lose control, said Tadokoro, whose robots have also been used at the Fukushima plant.

“On top of the high level of radiation, the entrance (to the containment vessel) for the robot is very small,” restricting what types of robots can be used to hunt for the melted fuel, he said.

Tepco said the opening it created on the side of the reactor 2 containment vessel is about 11 cm in diameter.

Fuel removal strategy

Tepco is set to conduct internal probes of the reactor 1 containment vessel this month and is preparing similar missions for reactor 3.

The government and utility then plan to adopt a basic fuel removal strategy this summer and fine-tune the plan next year, with the actual fuel removal taking place in or after 2021.

There are essentially three options for the strategy, according to the Tokyo-based International Research Institute for Nuclear Decommissioning (IRID), which is developing technologies for the Fukushima plant decommission.

One option is to flood the containment vessels with water and use a crane above the reactors to hoist up the melted fuel. The second option is to carry out the same process but without water. The third is to install removal equipment through the side of the containment vessel.

There are merits and drawbacks to each option, said Shoji Yamamoto, who heads the team developing technologies to create the fuel removal devices at IRID.

The flooding option can block radiation using water, but if the fuel melts into the water, it could pose a risk of recriticality. The debris may need to be cut into pieces for removal, but this process would enable water to get between multiple pieces, creating the condition for recriticality. For nuclear chain reactions to happen there needs to be a certain distance between nuclear fuel and water.

If there is no water, the recriticality risk is minimal but the massive radiation levels cannot be blocked, Yamamoto said.

Tepco’s Okamura said being able to block radiation with water is a huge plus, but noted the reactor 2 containment vessel had cracks and holes that could let injected coolant water escape.

With the Three Mile Island nuclear accident in the U.S., the flooding option was used to retrieve the melted fuel in the 1980s. But the key difference was that all of the melted fuel stayed inside the pressure vessel, so it was easier to flood the reactor.

Because the melted fuel in reactors 1, 2 and 3 at the Fukushima plant all penetrated the pressure vessels and fell into the containment vessels, extracting it from the top or the side was a tough call, Yamamoto said, noting it was important to know the exact location of the melted fuel.

The distance between the top of the pressure vessel and the bottom of the containment vessel is about 45 meters and some parts inside the pressure vessels will need to be removed if Tepco tries to remove the debris inside the containment vessels from the top.

“If we know that the melted fuel is concentrated in the containment vessels, it will be more efficient to remove it from the side” because the entry point is closer, Yamamoto said.

Whatever option is decided, Yamamoto stressed that maintaining the fuel removal device will be difficult because the radiation will probably cripple it.

“The fuel removal device will be controlled remotely … it will be broken somewhere down the line and the parts will have to be replaced, considering its (ability to withstand) radiation,” he said.

“Given that, maintenance will have to be done remotely, too, and that will be a big challenge.”

To remove or not

Another option altogether is for Tepco to leave the melted fuel where it is.

During a media tour of the Fukushima No. 1 plant last month, Okamura of Tepco said the utility intended to collect the melted fuel because leaving it was “not an appropriate way” to manage nuclear fuel.

Miyano of the Atomic Energy Society of Japan said the debris must be removed because radioactive materials, including nuclear fuel, must be strictly controlled under international rules requiring strict monitoring.

Domestic nuclear power plant operators have to report the amount of nuclear fuel they have to the Nuclear Regulation Authority, which then reports to the International Atomic Energy Agency.

“There is the question of whether the government and Tepco decide not to remove the fuel debris. That would be an international issue,” said Miyano, adding that a consensus from the international community would be needed.

At the same time, Miyano said debate and analysis will be required to decide which choice would be best by looking at various factors, including how much it will cost to pick up all the melted fuel and where to store it. ”

by Kazuaki Nagata

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Six years after Fukushima, much of Japan has lost faith in nuclear power — The Conversation

” Six years have passed since the Fukushima nuclear disaster on March 11, 2011, but Japan is still dealing with its impacts. Decommissioning the damaged Fukushima Daiichi nuclear plant poses unprecedented technical challenges. More than 100,000 people were evacuated but only about 13 percent have returned home, although the government has announced that it is safe to return to some evacuation zones.

In late 2016 the government estimated total costs from the nuclear accident at about 22 trillion yen, or about US$188 billion – approximately twice as high as its previous estimate. The government is developing a plan under which consumers and citizens will bear some of those costs through higher electric rates, taxes or both.

The Japanese public has lost faith in nuclear safety regulation, and a majority favors phasing out nuclear power. However, Japan’s current energy policy assumes nuclear power will play a role. To move forward, Japan needs to find a new way of making decisions about its energy future.

Uncertainty over nuclear power

When the earthquake and tsunami struck in 2011, Japan had 54 operating nuclear reactors which produced about one-third of its electricity supply. After the meltdowns at Fukushima, Japanese utilities shut down their 50 intact reactors one by one. In 2012 then-Prime Minister Yoshihiko Noda’s government announced that it would try to phase out all nuclear power by 2040, after existing plants reached the end of their 40-year licensed operating lives.

Now, however, Prime Minister Shinzo Abe, who took office at the end of 2012, says that Japan “cannot do without” nuclear power. Three reactors have started back up under new standards issued by Japan’s Nuclear Regulation Authority, which was created in 2012 to regulate nuclear safety. One was shut down again due to legal challenges by citizens groups. Another 21 restart applications are under review.

In April 2014 the government released its first post-Fukushima strategic energy plan, which called for keeping some nuclear plants as baseload power sources – stations that run consistently around the clock. The plan did not rule out building new nuclear plants. The Ministry of Economy, Trade and Industry (METI), which is responsible for national energy policy, published a long-term plan in 2015 which suggested that nuclear power should produce 20 to 22 percent of Japan’s electricity by 2030.

Meanwhile, thanks mainly to strong energy conservation efforts and increased energy efficiency, total electricity demand has been falling since 2011. There has been no power shortage even without nuclear power plants. The price of electricity rose by more than 20 percent in 2012 and 2013, but then stabilized and even declined slightly as consumers reduced fossil fuel use.

Japan’s Basic Energy Law requires the government to release a strategic energy plan every three years, so debate over the new plan is expected to start sometime this year.

Public mistrust

The most serious challenge that policymakers and the nuclear industry face in Japan is a loss of public trust, which remains low six years after the meltdowns. In a 2015 poll by the pro-nuclear Japan Atomic Energy Relations Organization, 47.9 percent of respondents said that nuclear energy should be abolished gradually and 14.8 percent said that it should be abolished immediately. Only 10.1 percent said that the use of nuclear energy should be maintained, and a mere 1.7 percent said that it should be increased.

Another survey by the newspaper Asahi Shimbun in 2016 was even more negative. Fifty-seven percent of the public opposed restarting existing nuclear power plants even if they satisfied new regulatory standards, and 73 percent supported a phaseout of nuclear power, with 14 percent advocating an immediate shutdown of all nuclear plants.

Who should pay to clean up Fukushima?

METI’s 22 trillion yen estimate for total damages from the Fukushima meltdowns is equivalent to about one-fifth of Japan’s annual general accounting budget. About 40 percent of this sum will cover decommissioning the crippled nuclear reactors. Compensation expenses account for another 40 percent, and the remainder will pay for decontaminating affected areas for residents.

Under a special financing scheme enacted after the Fukushima disaster, Tepco, the utility responsible for the accident, is expected to pay cleanup costs, aided by favorable government-backed financing. However, with cost estimates rising, the government has proposed to have Tepco bear roughly 70 percent of the cost, with other electricity companies contributing about 20 percent and the government – that is, taxpayers – paying about 10 percent.

This decision has generated criticism both from experts and consumers. In a December 2016 poll by the business newspaper Nihon Keizai Shimbun, one-third of respondents (the largest group) said that Tepco should bear all costs and no additional charges should be added to electricity rates. Without greater transparency and accountability, the government will have trouble convincing the public to share in cleanup costs.

Other nuclear burdens: Spent fuel and separated plutonium

Japanese nuclear operators and governments also must find safe and secure ways to manage growing stockpiles of irradiated nuclear fuel and weapon-usable separated plutonium.

At the end of 2016 Japan had 14,000 tons of spent nuclear fuel stored at nuclear power plants, filling about 70 percent of its onsite storage capacity. Government policy calls for reprocessing spent fuel to recover its plutonium and uranium content. But the fuel storage pool at Rokkasho, Japan’s only commercial reprocessing plant, is nearly full, and a planned interim storage facility at Mutsu has not started up yet.

The best option would be to move spent fuel to dry cask storage, which withstood the earthquake and tsunami at the Fukushima Daiichi nuclear plant. Dry cask storage is widely used in many countries, but Japan currently has it at only a few nuclear sites. In my view, increasing this capacity and finding a candidate site for final disposal of spent fuel are urgent priorities.

Japan also has nearly 48 tons of separated plutonium, of which 10.8 tons are stored in Japan and 37.1 tons are in France and the United Kingdom. Just one ton of separated plutonium is enough material to make more than 120 crude nuclear weapons.

Many countries have expressed concerns about Japan’s plans to store plutonium and use it in nuclear fuel. Some, such as China, worry that Japan could use the material to quickly produce nuclear weapons.

Now, when Japan has only two reactors operating and its future nuclear capacity is uncertain, there is less rationale than ever to continue separating plutonium. Maintaining this policy could increase security concerns and regional tensions, and might spur a “plutonium race” in the region.

As a close observer of Japanese nuclear policy decisions from both inside and outside of the government, I know that change in this sector does not happen quickly. But in my view, the Abe government should consider fundamental shifts in nuclear energy policy to recover public trust. Staying on the current path may undermine Japan’s economic and political security. The top priority should be to initiate a national debate and a comprehensive assessment of Japan’s nuclear policy. ”

by The Conversation

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NRA slows plan to reuse contaminated soil — SimplyInfo.org

” Japan’s Environment Ministry had a plan. They were going to solve the problem of the massive piles of radioactive soil but reusing it. One plan they described was using it as the base in roads. They didn’t provide much detail on how this would work or how it would not end up leaching contamination to the wider environment.

Japan’s nuclear regulator (NRA) is required to review any act by another agency that involves radiation exposures to the public. Now the NRA has requested a detailed plan before any review would begin. They want details about how this soil would be prevented from being used in residential areas or where children would be exposed.

This may have effectively put a stop to the Environment Ministry plan. Their goal appeared to be to declassify large amounts of contaminated soil and just make it go away however possible. NRA’s requirements may be too inconvenient to continue with that plan. ”

by SimplyInfo.org

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NRA puts stop to plan to reuse contaminated soil — SimplyInfo.org

” Japan’s Environment Ministry had a plan. They were going to solve the problem of the massive piles of radioactive soil but reusing it. One plan they described was using it as the base in roads. They didn’t provide much detail on how this would work or how it would not end up leaching contamination to the wider environment.

Japan’s nuclear regulator (NRA) is required to review any act by another agency that involves radiation exposures to the public. Now the NRA has requested a detailed plan before any review would begin. They want details about how this soil would be prevented from being used in residential areas or where children would be exposed.

This may have effectively put a stop to the Environment Ministry plan. Their goal appeared to be to declassify large amounts of contaminated soil and just make it go away however possible. NRA’s requirements may be too inconvenient to continue with that plan. ”

by Nancy Foust, SimplyInfo.org

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NRA: Ice wall effects ‘limited’ at Fukushima nuclear plant — The Asahi Shimbun

” Citing “limited, if any effects,” the Nuclear Regulation Authority said a highly touted “frozen soil wall” should be relegated to a secondary role in reducing contaminated groundwater at the Fukushima No. 1 nuclear plant.

The government spent 34.5 billion yen ($292 million) to build the underground ice wall to prevent groundwater from mixing with radioactive water in four reactor buildings at the crippled plant.

But the NRA, Japan’s nuclear watchdog, concluded on Dec. 26 that the wall has been ineffective in diverting the water away from the buildings. It said that despite the low rainfall over the past several months, the amount of groundwater pumped up through wells outside the frozen wall on the seaside is still well above the reduction target.

It urged the plant operator, Tokyo Electric Power Co., to tackle the groundwater problem primarily with pumps, not the ice wall.

In response, TEPCO at the meeting said that by next autumn, it will double its capacity to pump up groundwater from the current 800 tons a day.

About 400 tons of groundwater enters the damaged reactor buildings each day and mixes with highly radioactive water used to cool melted nuclear fuel.

The ice wall project, compiled by the industry ministry in May 2013, was seen as a fundamental solution to this problem that has hampered TEPCO’s cleanup efforts since the triple meltdown in March 2011.

Some 1,568 frozen ducts were inserted 30 meters deep into the ground to circulate a liquid at 30 degrees below zero. The freezing process was supposed to have created a solid wall of ice that could block the groundwater.

TEPCO began freezing the wall on the seaside in March. It announced in the middle of October that the temperature at all measuring points in that area was below zero.

Before the frozen wall project, TEPCO had to pump up about 300 tons of contaminated water a day. The daily volume dropped to about 130 tons in recent weeks, but it was still well beyond the target of 70 tons.

Still, TEPCO boasted about the effectiveness of the ice wall at the meeting with the NRA on Dec. 26, saying, “We are seeing certain results.”

The NRA, however, said the results are limited at best.

Toyoshi Fuketa, an NRA commissioner, already warned TEPCO in October that it cannot expect the ice wall to be highly effective in containing the groundwater.

“Pumping up groundwater through wells should be the main player because it can reliably control the groundwater level,” Fuketa said at that time. “The ice wall will play a supporting role.”

That sentiment was echoed at the Dec. 26 meeting.

However, the NRA approved the utility’s plan to begin freezing dirt for a wall on the mountain side of the nuclear plant.

The NRA was previously concerned about risks posed by the new ice wall. If it totally blocked groundwater from the mountain side, the water level within the frozen soil near the reactors could become too low, allowing highly contaminated water inside the reactor buildings to flow out more rapidly.

The NRA urged TEPCO to delay work on the mountain side until the ice wall on the seaside portion proved effective.

But it reversed its stance, saying a sharp drop in the groundwater level is unlikely based on the ineffectiveness of the existing ice wall.

“The frozen wall on the mountain side will not be able to block groundwater because the wall on the seaside was also unable to do so,” Fuketa said. “It will not be very dangerous to freeze the wall on the mountain side as long as the work is carried out carefully.”

TEPCO will start the work to freeze the ducts at five sections as early as next year.

Masashi Kamon, professor emeritus of geotechniques at Kyoto University, expressed skepticism about continuing the ice wall project without a full scrutiny of the underground conditions.

“Soil around the tunnels for underground pipes must be hard to freeze,” he said. “TEPCO should find out the conditions of the very bottom of the ice wall by drilling at least one section. It is questionable to continue with the project without a review.” ”

by Kohei Tomida

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Fukushima aftershock renews public concern about restarting Kansai’s aging nuclear reactors — The Japan Times

” KYOTO – The magnitude-7.4 aftershock that rocked Fukushima Prefecture and its vicinity last week, more than five years after the mega-quake and tsunami of March 2011, triggered fresh nuclear concerns in the Kansai region, which hosts Kansai Electric Power Co.’s Mihama plant in Fukui Prefecture.

The aftershock came as the Nuclear Regulation Authority approved a two-decade extension for Mihama’s No. 3 reactor on Nov. 16, allowing it and two others that have already been approved to run for as long as 60 years to provide electricity to the Kansai region.

Residents need to live with the fact that they are close to the Fukui reactors, which are at least 40 years old. Despite reassurances by Kepco, its operator, and the nuclear watchdog, worries remain over what would happen if an earthquake similar to the one in 2011, or even last week, hit the Kansai region.

Kyoto lies about 60 km and Osaka about 110 km from the old Fukui plants. Lake Biwa, which provides water to about 13 million people, is less than 60 km away.

In addition to Kepco’s 40-year-old Mihama No. 3, reactors 1 and 2 at the Takahama nuclear power plant in Fukui are 42 and 41 years old, respectively.

In the event of an accident, evacuation procedures for about 253,000 residents of Fukui, Shiga, and Kyoto prefectures who are within 30 km of the plants would go into effect.

But how effective might they be?

The majority does not live in Fukui. Just over half, or 128,500, live in neighboring Kyoto, especially in and around the port city of Maizuru, home to a Self-Defense Forces base. Another 67,000 live in four towns in Fukui and about 58,000 live in northern Shiga Prefecture.

Plans call for Fukui and Kyoto prefecture residents to evacuate to 29 cities and 12 towns in Hyogo Prefecture and, if facilities there are overwhelmed, to Tokushima Prefecture in Shikoku. Those in Shiga are supposed to evacuate to cities and towns in Osaka Prefecture.

In a scenario put together by Kyoto Prefecture three years ago, it was predicted that tens of thousands of people would take to available roads in the event of an nuclear accident. A 100 percent evacuation of everyone within 30 km of a stricken Fukui plant was estimated to take between 15 and 29 hours, depending on how much damage there was to the transportation infrastructure.

But Kansai-based anti-nuclear activists have criticized local evacuation plans as being unrealistic for several reasons.

First, they note that the region around the plants gets a lot of snow in the winter, which could render roads, even if still intact after a quake or other disaster, much more difficult to navigate, slowing evacuations even further.

Second is the radiation screening process that has been announced in official local plans drawn up by Kyoto and Hyogo prefectures.

While automobiles would be stopped at various checkpoints along the roads leading out of Fukui and given radiation tests, those inside would not be tested if the vehicle itself has radiation levels below the standard.

If the radiation is above standard, one person, a “representative” of everyone in the car, would be checked and, if approved, the car would be allowed to continue on its way under the assumption that the others had also been exposed to levels below standard. This policy stands even if those levels might be more dangerous to children than adults.

Finally, there is the question of whether bus drivers would cooperate by going in and out of radioactive zones to help those who lack quick access to a car, especially senior citizens in need of assistance.

None of the concerns about the evacuation plans is new, and most have been pointed out by safety experts, medical professionals and anti-nuclear groups.

But with the NRA having approved restarts for three Kansai-area reactors that are over 40 years old, Kansai leaders are responding more cautiously to efforts to restart Mihama No. 3 in particular.

“It is absolutely crucial that local understanding for Mihama’s restart be obtained,” said pro-nuclear Fukui Gov. Issei Nishikawa in July, after a local newspaper survey showed that only about 37 percent of Fukui residents agree with the decision to restart old reactors.

Shiga Gov. Taizo Mikazuki, who is generally against nuclear power, was even more critical of the NRA’s decision to restart Mihama.

“There are major doubts about the law that regulates the use of nuclear reactors more than 40 years old. The central government and Kepco need to explain safety countermeasures to residents who are uneasy. People are extremely uneasy about continuing to run old reactors,” the governor said earlier this month. ”

by Eric Johnston

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