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. “

Nuclear fuel debris removal at Fukushima plant could start with No. 2 reactor — The Japan Times

” A government-backed organization in charge of supporting the decommissioning of nuclear plants is considering proposing the removal of melted nuclear fuel debris beginning with the No. 2 reactor at Tokyo Electric Power Company Holdings Inc.’s Fukushima No. 1 nuclear plant, officials said Thursday.

Nuclear Damage Compensation and Decommissioning Facilitation Corp. (NDF) believes that the No. 2 unit is the most suitable for melted fuel removal work among the three crippled reactors based on the results of its investigation into radiation levels at the reactors and the conditions inside them.

In January 2018, Tepco confirmed the presence of deposits of melted nuclear fuel debris inside the No. 2 reactor containment vessel of the plant in Fukushima that was damaged in the March 2011 earthquake and tsunami.

In February this year, the company made physical contact with the deposits, making much more progress in investigating the No. 2 reactor than the No. 1 and No. 3 reactors.

Tepco plans to further investigate the inside of the No. 2 reactor by the end of March next year and aims to collect sample debris.

According to a summary of a strategic plan on decommissioning that was released by NDF, a robot arm is expected to be inserted into the reactor containment vessel in order to remove melted fuel little by little.

Removed debris is due to be placed in a special container and transferred to a storage facility within the plant.

NDF plans to submit its proposals, including the strategic decommissioning plan, to the government around autumn this year.

After receiving the proposals, the government plans to determine the method of debris removal by the end of March next year. It aims to start debris removal in 2021. ”

by The Japan Times, Jiji

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Remote-controlled probe picks up radioactive debris at Fukushima for the first time — Gizmodo

” Tepco, the state-owned operator of the badly damaged Fukushima nuclear plant, has conducted an important test in which a remote-controlled probe managed to grasp several small grains of radioactive debris, AFP reports. The successful operation marked an important achievement for the company as it prepares for a cleanup operation that could take decades.

In March 2011, the devastating Tōhoku earthquake and tsunami triggered the core meltdown of three reactors at the Fukushima Daiichi nuclear power plant. Eight years later, the plant’s operator, Tokyo Electric Power Company Holdings (Tepco), is still in the formative stages of devising a clean-up plan.

The primary challenge, of course, is dealing with the intense radiation emanating from the melted fuel. Two years ago, for example, a robot became unresponsive after just two hours in reactor No. 2; there’s enough radiation down there—approximately 650 sieverts per hour—to fry a person within a few seconds. The episode showed that technical advancements will be required to make robots more resilient to radiation near the core, and that the cleanup will likely take longer than expected.

Early last year, a camera attached to a remote-controlled probe was sent into reactor No. 2. Images confirmed that fuel debris had melted through the reactor pressure vessel (RPV), also known as the reactor core, dripping down into a collection chamber known as the primary containment vessel (PCV). Images of the chamber showed pebble- and clay-like deposits covering the entire bottom of the PCV pedestal. This accumulated waste, along with similar piles at reactors No. 1 and 3, needs to be cleaned up, and Tepco is currently trying to determine the best way of doing so.

To that end, the state-owned company devised an operation to see what that material is like and determine if it can be moved. On Wednesday February 13, Tepco sent a probe equipped with a remotely operated robotic hand down into the No. 2 lower chamber, Japan Times reports. Using its tong-like fingers, the probe picked up five grain-sized pieces of radioactive melted fuel. AFP reported that the pieces were moved to a maximum height of 2 inches (5 centimeters) above the bottom of the chamber. In addition to taking images with a camera, the probe measured radiation and temperature during the investigation, according to a Tepco release.

No radioactive debris was removed from the chamber, but the eight-hour-long operation showed that some of the melted fuel can be moved—an important bit of evidence that will inform future plans to clean up the plant. But as the Japan Times noted, one of the six areas explored by the probe contained debris that had solidified into a clay-like substance, which the robotic hand was unable to grasp. Future robots will need to slice or saw through this material such that it can be removed. That won’t be easy.

A future test, planned for April, will see some debris removed from the chamber, according to the Japan Times. Tepco has yet to disclose how and where this radioactive waste will be stored.

The company is hoping to start removing radioactive fuel in earnest by 2021, but the clean-up is expected to take decades, with some estimates suggesting it won’t be done until the 2050s. Many other technological hurdles still exist, such as determining the full extent of structural damage at the Fukushima plant, locating all the melted fuel in the three damaged reactors, and figuring out a way to remove the large quantities of contaminated water stored at the site.

If that all sounds overwhelming, well, it is. As we’ve said before, when nuclear power goes wrong, it really goes wrong. ”

by George Dvorsky, Gizmodo

source with images and internal links

Here is a related article by Bloomberg.

Fukushima nuclear plant: Tsunami wall could have avoided disaster but boss scrapped the plan, employee testifies — Newsweek

” A worker for the plant involved the 2011 Fukushima nuclear disaster said in a Japanese court Wednesday that his former boss was warned that a massive tsunami could strike the site, but delayed measures to build a protective wall to prevent it.

An unnamed employee of the Tokyo Electric Power Company (TEPCO) that owns the ruined Fukushima Daiichi or No.1, Nuclear Power Plant testified during a trial this week that a 2008 safety test showed an earthquake could cause a tsunami as high as 52 feet capable of pounding the coastal facility, according to The Asahi Shimbun. The company was initially set to build a seawall, but the employee told the court that former TEPCO Vice President Sakae Muto suddenly dismissed the idea.

The potentially catastrophic scenario was brought up again during a meeting on March 7, 2011, compelling shocked regulators to again recommend a wall to shield the facility, The Japan Times reported. But it was too late already: A magnitude 9.0 earthquake and tsunami struck only four days later on March 11, 2011, leaving up to 18,500 people dead or missing and destroying the facility.

Three out of the six nuclear reactors at the Fukushima No.1 plant suffered devastating meltdowns. Muto, along with former TEPCO Chairman Tsunehisa Katsumata and former TEPCO Vice President Ichiro Takekuro were indicted in February 2016 and are facing trial for suspected professional negligence resulting in death or injury after the worst nuclear disaster since the Chernobyl incident in 1986.

The multi-billion dollar effort to recover the site is far past schedule and over budget, but the TEPCO has claimed some recent successes. Six years after the disaster, the melted nuclear fuel was finally founded at the bottom of the partially submerged reactors. The site was so radioactive, even the robots previously sent it could not traverse the deadly core.

Efforts to retrieve the fuel, however, have been hampered as the $324 million ice wall that penetrated 100 feet into the earth failed to stop groundwater from leaking into the site, as Reuters reported last month. In fact, the amount of groundwater seeping into the facility may have increased since the highly-anticipated ice wall was installed last August, amounting to the latest setback in a cleanup process already beset by seemingly endless complications and miscalculations.

Removing this water adds to an already growing storage crisis on the site. TEPCO deliberately added water to cool off the plant’s damaged reactors. After coming in contact with the plant, the coolant water and groundwater became tainted with a substance known as tritium, a byproduct of the nuclear process notoriously difficult to filter out of water. TEPCO has accumulated over 1 million tons of this tritium-laced water in 650 giant tanks, according to The Japan Times, and is urging the government to let the company begin dumping it into the ocean.

Some locals have protested this, however. While tritium was a natural byproduct of the nuclear process that experts have described as harmless in smaller doses and was dumped into oceans worldwide, Fukushima activists and fishermen have argued that dumping tritium, even in small quantities, would further hurt the reputation of the region, still synonymous with nuclear disaster. Nearby China and South Korea are among the nations that still restrict the import of certain products from Japan.

Lingering concerns about radiation have also reportedly kept many of the 160,000 residents that fled Fukushima from returning. Life, nevertheless, has begun to return to some parts of the crisis-stricken prefecture. The town of Okuma announced Wednesday that some citizens would be allowed to stay overnight starting next week for the first time since the March 2011 disaster, Japanese daily The Mainichi Shimbun said. ”

by Tom O’Connor, Newsweek

source with image and internal links

Clearing the radioactive rubble heap that was Fukushima Daiichi, 7 years on — Scientific American

” Seven years after one of the largest earthquakes on record unleashed a massive tsunami and triggered a meltdown at Japan’s Fukushima Daiichi nuclear power plant, officials say they are at last getting a handle on the mammoth task of cleaning the site before it is ultimately dismantled. But the process is still expected to be a long, expensive slog, requiring as-yet untried feats of engineering—and not all the details have yet been worked out.

When the disaster knocked out off- and on-site power supplies on March 11, 2011, three of the cooling systems for the plant’s four reactor units were disabled. This caused the nuclear fuel inside to overheat, leading to a meltdown and hydrogen explosions that spewed out radiation. The plant’s operator, Tokyo Electric Power Co. (TEPCO), responded by cooling the reactors with water, which continues today. Meanwhile thousands of people living in the surrounding area were evacuated and Japan’s other nuclear plants were temporarily shut down.

In the years since the disaster and the immediate effort to stanch the release of radioactive material, officials have been working out how to decontaminate the site without unleashing more radiation into the environment. It will take a complex engineering effort to deal with thousands of fuel rods, along with the mangled debris of the reactors and the water used to cool them. Despite setbacks, that effort is now moving forward in earnest, officials say. “We are still conducting studies on the location of the molten fuel, but despite this we have made the judgment that the units are stable,” says Naohiro Masuda, TEPCO’s chief decommissioning officer for Daiichi.

Completely cleaning up and taking apart the plant could take a generation or more, and comes with a hefty price tag. In 2016 the government increased its cost estimate to about $75.7 billion, part of the overall Fukushima disaster price tag of $202.5 billion. The Japan Center for Economic Research, a private think tank, said the cleanup costs could mount to some $470 billion to $660 billion, however.

Under a government roadmap, TEPCO hopes to finish the job in 30 to 40 years. But some experts say even that could be an underestimate. “In general, estimates of work involving decontamination and disposal of nuclear materials are underestimated by decades,” says Rod Ewing, a professor of nuclear security and geological sciences at Stanford University. “I think that we have to expect that the job will extend beyond the estimated time.”

The considerable time and expense are due to the cleanup being a veritable hydra that involves unprecedented engineering. TEPCO and its many contractors will be focusing on several battlefronts.

Water is being deliberately circulated through each reactor every day to cool the fuel within—but the plant lies on a slope, and water from precipitation keeps flowing into the buildings as well. Workers built an elaborate scrubbing system that removes cesium, strontium and dozens of other radioactive particles from the water; some of it is recirculated into the reactors, and some goes into row upon row of giant tanks at the site. There’s about one million tons of water kept in 1,000 tanks and the volume grows by 100 tons a day, down from 400 tons four years ago.

To keep more water from seeping into the ground and being tainted, more than 90 percent of the site has been paved. A series of drains and underground barriers—including a $325-million* supposedly impermeable “wall” of frozen soil—was also constructed to keep water from flowing into the reactors and the ocean. These have not worked as well as expected, though, especially during typhoons when precipitation spikes, so groundwater continues to be contaminated.

Despite the fact contaminated water was dumped into the sea after the disaster, studies by Japanese and foreign labs have shown radioactive cesium in fish caught in the region has fallen and is now within Japan’s food safety limits. TEPCO will not say when it will decide what to do with all the stored water, because dumping it in the ocean again would invite censure at home and abroad—but there are worries that another powerful quake could cause it to slosh out of the tanks.

Fuel Mop-up

A second major issue at Fukushima is how to handle the fuel¾the melted uranium cores as well as spent and unused fuel rods stored at the reactors. Using robotic probes and 3-D imaging with muons (a type of subatomic particle), workers have found pebbly deposits and debris at various areas inside the primary containment vessels in the three of the plant’s reactor units. These highly radioactive remains are thought to be melted fuel as well as supporting structures. TEPCO has not yet worked out how it can remove the remains, but it wants to start the job in 2021. There are few precedents for the task. Lake Barrett—director of the Three Mile Island nuclear plant during its decommissioning after a partial meltdown at the Middletown, Pa., facility in 1979—says TEPCO will use robots to remotely dig out the melted fuel and store it in canisters on-site before shipping to its final disposal spot. “This is similar to what we did at Three Mile Island, just much larger and with much more sophisticated engineering because their damage is greater than ours was,” Barrett says. “So although the work is technically much more challenging than ours was, Japan has excellent technological capabilities, and worldwide robotic technology has advanced tremendously in the last 30-plus years.”

Shaun Burnie, senior nuclear specialist with Greenpeace Germany, doubts the ambitious cleanup effort can be completed in the time cited, and questions whether the radioactivity can be completely contained. Until TEPCO can verify the conditions of the molten fuel, he says, “there can be no confirmation of what impact and damage the material has had” on the various components of the reactors—and therefore how radiation might leak into the environment in the future.

Although the utility managed to safely remove all 1,533 fuel bundles from the plant’s unit No. 4 reactor by December 2014, it still has to do the same for the hundreds of rods stored at the other three units. This involves clearing rubble, installing shields, dismantling the building roofs, and setting up platforms and special rooftop equipment to remove the rods. Last month a 55-ton dome roof was installed on unit No. 3 to facilitate the safe removal of the 533 fuel bundles that remain in a storage pool there. Whereas removal should begin at No. 3 sometime before April 2019, the fuel at units No. 1 and 2 will not be ready for transfer before 2023, according to TEPCO. And just where all the fuel and other radioactive solid debris on the site will be stored or disposed of long-term has yet to be decided; last month the site’s ninth solid waste storage building, with a capacity of about 61,000 cubic meters, went into operation.

As for what the site itself might look like decades from now, cleanup officials refuse to say. But they are quick to differentiate it from the sarcophagus-style containment of the 1986 Chernobyl catastrophe in the Soviet Union, in what is now Ukraine. Whereas the Chernobyl plant is sealed off and the surrounding area remains off-limits except for brief visits—leaving behind several ghost towns—Japanese officials want as many areas as possible around the Daiichi site to eventually be habitable again.

“To accelerate reconstruction and rebuilding of Fukushima as a region, and the lives of locals, the key is to reduce the mid- and long-term risk,” says Satoru Toyomoto, director for international issues at the Ministry of Economy, Trade and Industry’s Nuclear Accident Response Office. “In that regard, keeping debris on the premises without approval is not an option.” ”

by Tim Hornyak, Scientific American

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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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