METI eyes 2031 end to Fukushima No. 1 cleanup — The Japan Times via Nuclear News

This article was taken off The Japan Times website, but was reblogged on Nuclear News here. It was written by Mari Yamaguchi and published on Dec. 2, 2019.

The industry ministry on Monday unveiled a revised plan to remove molten nuclear fuel debris from the meltdown-hit Fukushima No. 1 power plant in 2021 — a process said to be the biggest hurdle to decommissioning the six-reactor facility.

Work to remove the debris should start with the No. 2 reactor, according to the mid- to long-term road map released by the government.
Designating a specific time frame for the first time, the plan also calls for completing the removal of 4,741 fuel rods left inside the cooling pools for reactor Nos. 1 to 6 by 2031.
“As more people return and rebuilding progresses in the areas around the No. 1 plant, we will take measures based on the basic principle of balancing rebuilding and decommissioning,” said Minister of Economy, Trade and Industry Hiroshi Kajiyama, who heads the state team tasked with decommissioning the heavily damaged plant.
The plan, revised for the fifth time, maintains the general outlook for finishing the cleanup within 30 to 40 years of the triple meltdown, which was triggered by the mega-quake and tsunami on March 11, 2011. But, given issues that have halted work and caused delays so far, it remains uncertain whether the plan will proceed as scheduled.
Here is a look at some of the challenges facing Fukushima No. 1:
Melted fuel debris
By far the toughest challenge is removing the 800 tons of nuclear fuel that melted in the three reactors before dropping from their cores and hardening at the bottom of the primary containment vessels.
Over the past two years, Tepco has made progress gathering details mainly from two of the reactors. In February, a small telescopic robot sent inside the No. 2 reactor showed that small pieces of debris can come off and be lifted out. Thus debris removal is scheduled to begin there by the end of 2021.
Earlier, assessments of the No. 3 reactor were hampered by high radiation and water levels in the PCVs. A robot survey at the No. 1 reactor also failed from extremely high radiation.
Experts say a 30- to 40-year completion decommissioning target is too optimistic. Some doubt that removing all of the fuel is even doable and suggest an approach like Chernobyl — contain the reactors and wait until radioactivity naturally fades.
Fuel rods
Together, the three reactors have more than 1,500 units of mostly spent nuclear fuel rods inside that must be kept cool in pools of water. They’re among the highest risks at the plant because the pools are uncovered, and loss of water from structural damage or sloshing in the event of another major quake could cause them to melt and release massive radiation.
The manager of the plant, Tokyo Electric Power Company Holdings Inc., started removing rods from the No. 3 reactor pool in April and aims to get all 566 out by March 2021. Removal of rods from units 1 and 2 is to begin in 2023.
By 2031, Tepco plans to remove thousands of rods at the two units that survived the tsunami and store them in dry casks on the compound. Over 6,300 fuel rods were in the six reactor cooling pools at the time, and only the pool at No. 4 has been emptied.
Tainted water
The government and Tepco have been unable to get rid of the more than 1 million tons of radioactive water that has been treated and stored on site, fearing public repercussions. The utility has managed to cut the volume by pumping up and diverting groundwater upstream, as well as by installing a costly underground “ice wall” around the reactor buildings to keep water from entering.
Tepco says it only has space for up to 1.37 million tons until summer 2022, raising speculation it might release the tainted water after the 2020 Olympics. Tepco and experts say that the tanks are hampering decommissioning work and that the space they occupy must be freed up to build storage for the debris and other radioactive materials to be removed. There is also the risk that the tanks might fail and release their contents in the event of another quake, tsunami or flood.
Experts say a controlled release of the water into the ocean is the only realistic option, one that will take decades. For years, a government panel has been discussing methods amid opposition from fishermen and residents who fear it will damage their products and their health.
Radioactive waste
Japan has yet to develop a plan to dispose of the highly radioactive waste that will come out of the reactors. Under the road map, the government and Tepco will compile a plan sometime after the first decade of removal work ends in 2031.
Managing the waste will require new technologies to compact it and reduce its toxicity. Tepco and the government say they plan to build a temporary storage site for the waste. But finding a site and getting public consent to store it there will be nearly impossible, raising doubts the cleanup can be finished within 40 years.
Manpower concerns
Securing a workforce for the decades-long project is yet another challenge, especially in a country with a rapidly aging and declining population. Tepco announced plans to hire foreign workers for the decommissioning process under Japan’s new visa program to attract unskilled foreign labor, but put it on hold after receiving government instructions on careful planning to address concerns about language problems and safety. Universities are also struggling to attract students in nuclear science, a formerly elite major that has become unpopular since the Fukushima crisis. “

Image shows extent of damage to reactor at Fukushima plant — The Asahi Shimbun

” An image taken by an underwater robot shows corroded tubes stuck in a hole created by melted fuel in the pressure vessel of the No. 3 reactor at the Fukushima No. 1 nuclear plant.

The image offers clues on the extent of the damage caused when fuel rods in the reactor melted through the bottom of the pressure vessel after the disaster at the nuclear plant unfolded in March 2011.

Tokyo Electric Power Co., operator of the plant, sent the specially designed robot into the reactor in July. The company earlier released images taken by the robot that showed what is believed to be melted nuclear fuel debris.

In the image released on Nov. 30, TEPCO identified the severely corroded and damaged tubes as parts of a device used to move control rods. Normally, that device is located inside the pressure vessel.

TEPCO on Nov. 30 also said it would conduct another study inside of the containment vessel of the No. 2 reactor at the plant in January. The containment vessel surrounds the pressure vessel.

A telescopic stick more than 10 meters long and equipped with a camera will be used for the survey. ”

by The Asahi Shimbun

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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

source with photos, video and internal links

Muons suggest location of fuel in unit 3 — World Nuclear News

” Some of the fuel in the damaged unit 3 of the Fukushima Daiichi plant has melted and dropped into the primary containment vessel, initial results from using a muon detection system indicate. Part of the fuel, however, is believed to remain in the reactor pressure vessel.

Muons are high-energy subatomic particles that are created when cosmic rays enter Earth’s upper atmosphere. These particles naturally and harmlessly strike the Earth’s surface at a rate of some 10,000 muons per square meter per minute. Muon tracking devices detect and track these particles as they pass through objects. Subtle changes in the trajectory of the muons as they penetrate materials and change in direction correlate with material density. Nuclear materials such as uranium and plutonium are very dense and are therefore relatively easy to identify. The muon detection system uses the so-called permeation method to measure the muon data.

Tokyo Electric Power Company (Tepco) installed a muon detection system on the first floor of unit 3’s turbine building. Measurements were taken between May and September this year.

Tepco said analysis of muon examinations of the fuel debris shows that most of the fuel has melted and dropped from its original position within the core.

Prior to the 2011 accident, some 160 tonnes of fuel rods and about 15 tonnes of control rods were located within the reactor core of unit 3. The upper and lower parts of the reactor vessel contains about 35 tonnes and 80 tonnes of structures, respectively.

The muon examination indicates that most of the debris – some 160 tonnes – had fallen to the bottom of the reactor pressure vessel and resolidified, with only about 30 tonnes remaining in the reactor core. Tepco said another 90 tonnes of debris remains in the upper part of the vessel.

The bulk of the fuel and structures in the core area dropped to the bottom of the reactor pressure vessel (RPV), Tepco believes. While part of the molten fuel is understood to have then fallen into the primary containment vessel (PCV), “there is a possibility that some fuel debris remains in the bottom of the RPV, though this is uncertain”, the company noted.

Similar muon measurements have already been conducted at units 1 and 2 at Fukushima Daiichi. Measurements taken at unit 1 between February and September 2015 indicated most of the fuel was no longer in the reactor’s core area. Measurements taken between March and July 2016 at unit 2 showed high-density materials, considered to be fuel debris, in the lower area of the RPV. Tepco said that more fuel debris may have fallen into the PCV in unit 3 than in unit 2.

Tepco said the results obtained from the muon measurements together with knowledge obtained from internal investigations of the primary containment vessels using remote-controlled robots will help it plan the future removal of fuel debris from the damaged units. ”

by World Nuclear News

source with illustration of Unit 1-3

Fukushima cleanup chief urges better use of probe robot — The Seattle Times

” TOKYO (AP) — The head of decommissioning for the damaged Fukushima nuclear plant said Thursday that more creativity is needed in developing robots to locate and assess the condition of melted fuel rods.

A robot sent inside the Unit 2 containment vessel last month could not reach as close to the core area as was hoped for because it was blocked by deposits, believed to be a mixture of melted fuel and broken pieces of structures inside. Naohiro Masuda, president of Fukushima Dai-ichi Decommissioning, said he wants another probe sent in before deciding on methods to remove the reactor’s debris.

Unit 2 is one of the Fukushima reactors that melted down following the 2011 earthquake and tsunami.

The plant’s operator, Tokyo Electric Power Co., needs to know the melted fuel’s exact location as well as structural damage in each of the three wrecked reactors to figure out the best and safest ways to remove the fuel. Probes must rely on remote-controlled robots because radiation levels are too high for humans to survive.

Despite the incomplete probe missions, officials have said they want to stick to their schedule to determine the removal methods this summer and start work in 2021.

Earlier probes have suggested worse-than-anticipated challenges for the plant’s cleanup, which is expected to take decades. During the Unit 2 probe in early February, the “scorpion” robot crawler stalled after its total radiation exposure reached its limit in two hours, one-fifth of what was anticipated.

“We should think out of the box so we can examine the bottom of the core and how melted fuel debris spread out,” Masuda told reporters.

Probes are also being planned for the other two reactors. A tiny waterproof robot will be sent into Unit 1 in coming weeks, while experts are still trying to figure out a way to access the badly damaged Unit 3.

TEPCO is struggling with the plant’s decommissioning. The 2011 meltdown forced tens of thousands of nearby residents to evacuate their homes, and many have still not been able to return home due to high radiation levels.

Cleanup of communities outside of the plant is also a challenge. The cost has reportedly almost doubled to 4 trillion yen ($35 billion) from an earlier estimate. On Thursday, police arrested an Environment Ministry employee for allegedly taking bribes from a local construction firm president, media reports said. ”

by Mari Yamaguchi, The Associated Press

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Lost in translation: Fukushima readings are not new spikes, just the same “hot mess” that’s always been there — Beyond Nuclear

” The ongoing Fukushima nuclear catastrophe has been back in the news lately following record high readings at the reactor site. Radiation levels were estimated to be 530 sieverts per hour, the highest recorded since the triple core meltdown in March 2011.

But upon further examination, the story has been misreported, in part due to mistranslation. In fact, according to Nancy Foust of SimplyInfo.org, interviewed on Nuclear Hotseat, there was no spike. High readings were in expected locations that TEPCO was only able to access recently. Therefore, the reading became evident because workers were getting closer to the melted fuel in more dangerous parts of the facility. In other words, it’s not a new hot mess, just the same hot mess it’s always been, pretty much from the beginning. The good news is nothing has changed. The bad news is – nothing has changed.

The confusion was initially caused by a translation error that SimplyInfo.org thinks occurred between the Kyoto News and Japan Times. Since this happened, Foust and her group have been trying to get news sources to correct the stories, with limited success.

The elevated radiation levels are inside containment (good news) in ruined unit 2 and were discovered using a camera, not proper radiation monitors. Therefore, the high reading may not be reliable since it is an estimate based on interference data with the camera. (It has been reported that the 530 Sievert/hour figure could be 30% too low, or 30% too high. 530 Sieverts/hour equates with 53,000 Rems/hour, a dose rate that would deliver a fatal dose of radiation to a person a short distance away, with no radiation shielding, in a minute or less exposure time.) TEPCO is planning on sending in a robot properly equipped with radiation detectors to take a reliable reading. Although no date has been given, TEPCO indicates it expects to deploy the robot within 30 days or so.

Foust theorizes that the bulk of the melted irradiated nuclear fuel is probably right below the reactor vessel burned into the concrete below. No one knows if melted irradiated nuclear fuel has gone into the ground water below that. ”

by Beyond Nuclear

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