Six years after Fukushima, robots finally find reactors’ melted uranium fuel — The New York Times

” FUKUSHIMA DAIICHI NUCLEAR POWER PLANT, Japan — Four engineers hunched before a bank of monitors, one holding what looked like a game controller. They had spent a month training for what they were about to do: pilot a small robot into the contaminated heart of the ruined Fukushima nuclear plant.

Earlier robots had failed, getting caught on debris or suffering circuit malfunctions from excess radiation. But the newer version, called the Mini-Manbo, or “little sunfish,” was made of radiation-hardened materials with a sensor to help it avoid dangerous hot spots in the plant’s flooded reactor buildings.

The size of a shoe box, the Manbo used tiny propellers to hover and glide through water in a manner similar to an aerial drone.

After three days of carefully navigating through a shattered reactor building, the Manbo finally reached the heavily damaged Unit 3 reactor. There, the robot beamed back video of a gaping hole at the bottom of the reactor and, on the floor beneath it, clumps of what looked like solidified lava: the first images ever taken of the plant’s melted uranium fuel.

The discovery in July at Unit 3, and similar successes this year in locating the fuel of the plant’s other two ruined reactors, mark what Japanese officials hope will prove to be a turning point in the worst atomic disaster since Chernobyl.

The fate of the fuel had been one of the most enduring mysteries of the catastrophe, which occurred on March 11, 2011, when an earthquake and 50-foot tsunami knocked out vital cooling systems here at the plant.

Left to overheat, three of the six reactors melted down. Their uranium fuel rods liquefied like candle wax, dripping to the bottom of the reactor vessels in a molten mass hot enough to burn through the steel walls and even penetrate the concrete floors below.

No one knew for sure exactly how far those molten fuel cores had traveled before desperate plant workers — later celebrated as the “Fukushima Fifty” — were able to cool them again by pumping water into the reactor buildings. With radiation levels so high, the fate of the fuel remained unknown.

As officials became more confident about managing the disaster, they began a search for the missing fuel. Scientists and engineers built radiation-resistant robots like the Manbo and a device like a huge X-ray machine that uses exotic space particles called muons to see the reactors’ innards.

Now that engineers say they have found the fuel, officials of the government and the utility that runs the plant hope to sway public opinion. Six and a half years after the accident spewed radiation over northern Japan, and at one point seemed to endanger Tokyo, the officials hope to persuade a skeptical world that the plant has moved out of post-disaster crisis mode and into something much less threatening: cleanup.

“Until now, we didn’t know exactly where the fuel was, or what it looked like,” said Takahiro Kimoto, a general manager in the nuclear power division of the plant’s operator, Tokyo Electric Power Co., or Tepco. “Now that we have seen it, we can make plans to retrieve it.”

Tepco is keen to portray the plant as one big industrial cleanup site. About 7,000 people work here, building new water storage tanks, moving radioactive debris to a new disposal site, and erecting enormous scaffoldings over reactor buildings torn apart by the huge hydrogen explosions that occurred during the accident.

Access to the plant is easier than it was just a year ago, when visitors still had to change into special protective clothing. These days, workers and visitors can move about all but the most dangerous areas in street clothes.

A Tepco guide explained this was because the central plant grounds had been deforested and paved over, sealing in contaminated soil.

During a recent visit, the mood within the plant was noticeably more relaxed, though movements were still tightly controlled and everyone was required to wear radiation-measuring badges. Inside a “resting building,” workers ate in a large cafeteria and bought snacks in a convenience store.

At the plant’s entrance, a sign warned: “Games like Pokemon GO are forbidden within the facility.”

“We have finished the debris cleanup and gotten the plant under control,” said the guide, Daisuke Hirose, a spokesman for Tepco’s subsidiary in charge of decommissioning the plant. “Now, we are finally preparing for decommissioning.”

In September, the prime minister’s office set a target date of 2021 — the 10th anniversary of the disaster — for the next significant stage, when workers begin extracting the melted fuel from at least one of the three destroyed reactors, though they have yet to choose which one.

The government admits that cleaning up the plant will take at least another three to four decades and tens of billions of dollars. A $100 million research center has been built nearby to help scientists and engineers develop a new generation of robots to enter the reactor buildings and scoop up the melted fuel.

At Chernobyl, the Soviets simply entombed the charred reactor in concrete after the deadly 1986 accident. But Japan has pledged to dismantle the Fukushima plant and decontaminate the surrounding countryside, which was home to about 160,000 people who were evacuated after accident.

Many of them have been allowed to return as the rural towns around the plant have been decontaminated. But without at least starting a cleanup of the plant itself, officials admit they will find it difficult to convince the public that the accident is truly over.

They also hope that beginning the cleanup will help them win the public’s consent to restart Japan’s undamaged nuclear plants, most of which remain shut down since the disaster.

Tepco and the government are treading cautiously to avoid further mishaps that could raise doubts that the plant is under control.

“They are being very methodical — too slow, some would say — in making a careful effort to avoid any missteps or nasty surprises,” said David Lochbaum, director of the nuclear safety project at the Union of Concerned Scientists, who was a co-author of a book on the disaster.

“They want to regain trust. They have learned that trust can be lost much quicker than it can be recovered.”

To show the course followed by the Manbo, Tepco’s Mr. Hirose guided me inside the building containing the undamaged Unit 5 reactor, which is structurally the same as two of the destroyed reactors.

Mr. Hirose pointed toward the spot on a narrow access ramp where two robots, including one that looked like a scorpion, got tangled in February by debris inside the ruined Unit 2.

Before engineers could free the scorpion, its monitoring screen faded to black as its electronic components were overcome by radiation, which Tepco said reached levels of 70 sieverts per hour. (A dose of one sievert is enough to cause radiation sickness in a human.)

Mr. Hirose then led me underneath the reactor, onto what is called the pedestal.

The bottom of the reactor looked like a collection of huge bolts — the access points for control rods used to speed up and slow down the nuclear reaction inside a healthy reactor. The pedestal was just a metal grating, with the building’s concrete floor visible below.

“The overheated fuel would have dropped from here, and melted through the grating around here,” Mr. Hirose said, as we squatted to avoid banging our heads on the reactor bottom. The entire area around the reactor was dark, and cluttered with pipes and machinery.

To avoid getting entangled, the Manbo took three days to travel some 20 feet to the bottom of Unit 3.

To examine the other two reactors, engineers built a “snake” robot that could thread its way through wreckage, and the imaging device using muons, which can pass through most matter. The muon device has produced crude, ghostly images of the reactors’ interiors.

Extracting the melted fuel will present its own set of technical challenges, and risks.

Engineers are developing the new radiation-resistant robots at the Naraha Remote Technology Development Center. It includes a hangar-sized building to hold full-scale mock-ups of the plant and a virtual-reality room that simulates the interiors of the reactor buildings, including locations of known debris.

“I’ve been a robotic engineer for 30 years, and we’ve never faced anything as hard as this,” said Shinji Kawatsuma, director of research and development at the center. “This is a divine mission for Japan’s robot engineers.” “

by Martin Fackler, The New York Times

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Fukushima debris heading to intermediate storage facility — The Asahi Shimbun

” The Environment Ministry on Oct. 28 will start bringing radiation-contaminated soil to an intermediate storage site in Fukushima Prefecture, despite having acquired less than half of the land needed for the overall project.

The ministry’s announcement on Oct. 24 marks a long-delayed step toward clearing temporary sites that were set up around the prefecture to store countless bags of radioactive debris gathered after the triple meltdown at the Fukushima No. 1 nuclear power plant in March 2011.

The entire intermediate storage project will cover a 16-square-kilometer area spanning the towns of Futaba and Okuma around the nuclear plant. It is designed to hold up to 22 million cubic meters of contaminated debris for a maximum period of 30 years.

However, the ministry is still negotiating with landowners on buying parcels of land within the area. As of the end of September, the ministry had reached acquisition agreements for only about 40 percent of the land for the project.

The soil storage facility that will open on Oct. 28 is located on the Okuma side. It has a capacity of about 50,000 cubic meters.

Bags of contaminated soil stored in Okuma will be transferred to the facility, where the debris will be separated based on radiation dosages.

A similar storage facility is being constructed on the Futaba side.

The ministry initially planned to start full-scale operations of the entire storage facility in January 2015. However, it took longer than expected to gain a consensus from local residents and acquire land at the proposed site.

In March 2015, a portion of the contaminated soil was brought to the Okuma facility for temporary storage. ”

by The Asahi Shimbun

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Tepco to delay emptying fuel storage pools at Fukushima plant — The Asahi Shimbun

” Plans to remove fuel rods from two spent fuel pools at the Fukushima No. 1 nuclear plant will be delayed by up to three years because of difficulties in clearing debris and reducing radiation levels.

The government and plant operator Tokyo Electric Power Co. originally expected to start emptying the storage pools at the No. 1 and No. 2 reactor buildings in fiscal 2020.

But they plan to move the starting time to fiscal 2023 in their first review in two years of the roadmap for decommissioning the stricken nuclear plant, sources said Sept. 20.

They are expected to announce the revised roadmap later this month.

A survey of the upper levels of the two reactor buildings, where the storage pools are located, found debris piled up in a much more complicated way than initially envisaged.

That will lengthen the time needed to clear the debris, thus delaying the removal of the fuel rods, the sources said.

In addition, radiation levels remain extremely high inside the buildings.

The No. 1 reactor’s storage pool holds 392 nuclear fuel assemblies, while the No. 2 reactor’s pool has 615 assemblies.

Work to remove the 566 assemblies from the No. 3 reactor’s pool is scheduled to begin in the middle of fiscal 2018 as originally planned.

The three reactors melted down in the 2011 disaster, triggered by the magnitude-9.0 Great East Japan Earthquake and tsunami.

The review of the decommissioning roadmap is also expected to revise the target of “starting the removal” of melted nuclear fuel and debris in the three reactors in 2021 to “aiming to start the removal” in 2021.

But the government and TEPCO will maintain the goal of completing the decommissioning in “30 to 40 years,” the sources said. ”

by Chikako Kawahara, The Asahi Shimbun

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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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Fuel removal at Fukushima reactor again faces delay — The Asahi Shimbun

” Work to retrieve spent nuclear fuel in the No. 3 reactor building storage pool of the crippled Fukushima No. 1 nuclear power plant will again be postponed due to a delay in clearing radioactive debris at the site.

TEPCO planned to begin removing 566 spent nuclear fuel assemblies in the storage pool in January 2018. However, the government and the plant operator, Tokyo Electric Power Co., decided on the postponement, sources said on Dec. 22. They will decide on a new timetable in a few weeks.

The work was initially scheduled for fiscal 2015, but had been pushed back because of high radiation readings in and around the No. 3 reactor building. The building was heavily damaged by a hydrogen explosion in the days following the disaster, triggered by the 2011 Great East Japan Earthquake and tsunami.

TEPCO had attempted to lower radiation levels by clearing the radioactive debris remaining at the site.

But the clearing work took longer than expected due to contamination being more widespread than previously thought, forcing TEPCO and the government to again put off the retrieval.

Radiation levels have now dropped as almost all of wreckage at the site has been cleared, TEPCO said. The government and TEPCO have said fuel retrieval at the No. 1 and No. 2 reactor buildings will start in fiscal 2020 or later. ”

by The Asahi Shimbun

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Work starts in Fukushima on intermediate waste facility — The Asahi Shimbun

” The Environment Ministry on Nov. 15 started building a facility in Fukushima Prefecture that will store radiation-contaminated debris for up to 30 years, despite obtaining permission for only 11 percent of the site.

The 16-square-kilometer storage facility is expected to hold up to 22 million cubic meters of materials contaminated by radioactive fallout from the disaster at the Fukushima No. 1 nuclear power plant in March 2011.

“I hope that you take pride in this project and cooperate to construct the facility,” Tadahiko Ito, a vice environment minister, told workers.

The facility, which will span the towns of Futaba and Okuma, is expected to start accepting, sorting and storing the debris in autumn 2017 at the earliest, more than two-and-a-half years later than the initial schedule of January 2015.

The project has been delayed because the ministry has faced difficulties buying or borrowing land for the project.

In fact, only 445 of the 2,360 landowners of plots at the site have agreed to sell or lend their properties to the ministry for the storage facility as of the end of October.

Many of the reluctant landowners, who possess 89 percent of the land, fear the contaminated waste will remain at the facility well beyond 30 years.

The government has worked out a bill stipulating that contaminated materials kept in the intermediate storage facility will be moved out of Fukushima Prefecture in 2045. However, the government has yet to decide on the location of the final disposal site.

A huge cleanup operation after the triple meltdown at the Fukushima nuclear plant collected tons of radioactive soil and debris.

In March 2015, the ministry borrowed land and created a “temporary storage place” within a 16-square-km site on an experimental basis.

However, only about 70,000 cubic meters of the waste has been taken to the temporary storage site as of the end of October. The remaining waste, exceeding 10 million cubic meters, is being tentatively stored at about 150,000 locations in the prefecture.

“If the transportation of contaminated materials to the intermediate storage facility proceeds, the waste currently stored in residential areas and at company compounds will be transported there,” said an official of the Fukushima prefectural government’s section in charge of decontamination. ”

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