Unit 2 of Genkai NPP will be decommissioned.
Unit 3 and 4 of Genkai are still operating.
Kyushu Electric Power Co. said Wednesday it will scrap No. 2 reactor at its Genkai nuclear power plant in Saga Prefecture, seen in the forefront left of this photo taken in January
Feb 13, 2019
FUKUOKA – Kyushu Electric Power Co. said Wednesday it has decided to scrap its aging No. 2 reactor at its Genkai nuclear plant in Saga Prefecture.
The utility abandoned a plan to restart the unit, which has an output of 559 megawatts, in the face of the huge costs involved in enhancing the safety of the reactor that is already near the end of its 40-year operating life.
The reactor, which started operating in March 1981, has been idled since a routine checkup shortly before the March 2011 earthquake and tsunami disaster that triggered the Fukushima nuclear crisis.
The Genkai plant consists of four units. The utility already decided in 2015 to scrap its aging No. 1 unit, which had the same output capacity as the No. 2 reactor. Decommissioning work at the No. 1 reactor started in July 2017 and is expected to continue through fiscal 2043.
There have been a number of operational problems at the Genkai power plant. In May last year, pumps installed to control the circulation of cooling water at the No. 4 unit suffered malfunctions, following a steam leak from a pipe at the No. 3 reactor just a week after it was reactivated in March.
Some local residents have sought to stop operation of the Nos. 3 and 4 units with a temporary injunction, with doubts about the safety measures taken and citing the risk of volcanic eruptions in the region. Their case is pending at the Fukuoka High Court.
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50% in nuclear industry: Energy plan for 2030 is ‘unrealistic’
Tohoku Electric Power Co. has decided to decommission the No. 1 reactor at the Onagawa nuclear power plant in Miyagi Prefecture.
December 5, 2018
Half of companies in the nuclear industry doubt the government’s goal of having nuclear power account for 20 to 22 percent of Japan’s energy supply by fiscal 2030, according to a survey.
The reasons for their skepticism relate mainly to difficulties restarting or building reactors under stricter safety measures taken after the Fukushima nuclear disaster in 2011.
The survey was conducted in June and July by the Japan Atomic Industrial Forum, whose members include electric power companies that operate nuclear plants.
The forum contacted 365 companies in the nuclear industry, such as equipment manufacturers, and received responses from 254, or 70 percent.
According to the results, 50 percent of the companies said the government’s nuclear energy goal for fiscal 2030 is “unachievable,” compared with only 10 percent that said it is “achievable.” Forty percent said the attainability is “unknown.”
An estimated 30 reactors must be operating to reach the target, but the resumption of reactor operations has been slow since all of them were shut down after the triple meltdown at the Fukushima No. 1 nuclear power plant.
“Only nine reactors were restarted in the more than seven years after the accident in Fukushima,” Akio Takahashi, president of the forum and former senior official at Tokyo Electric Power Co., said at a news conference. “I guess respondents think it’s difficult (to achieve the goal) given the current pace (of the restarts).”
Tougher nuclear safety standards were set after the Fukushima disaster, forcing utilities to spend more on upgrading their reactors or keeping aging units operational.
Asked why they thought the government’s nuclear goal was unrealistic, 48 percent of the companies said, “There are no plans in sight to build or replace nuclear reactors.”
Thirty-three percent cited the delays in restarting idle reactors, while 16 percent said, “No progress can be seen in regaining trust from the public.”
Distrust of TEPCO Hampers Decommissioning
Friday, October 19
A major challenge at the Fukushima Daiichi nuclear power plant is disposing of water containing a large amount of radioactive tritium. The Japanese government proposed diluting and releasing the water into the sea, but many fisheries in Fukushima are voicing strong opposition to the proposal. Disposal of the tainted water is a must for scrapping reactors at the plant. So, what should the government and TEPCO officials do?
Doing away with tritium-tainted water is essential
Every day, more than 100 tons of radioactive water builds up. Despite various measures taken since the 2011 accident at Fukushima Daiichi, groundwater continues to enter the reactor buildings, mixing with water which is being used to cool the reactors.
The Tokyo Electric Power Company uses a system called ALPS to treat the water. Officials have been saying that the system’s high-performance filters can get rid of most radioactive substances, except tritium.
TEPCO is not allowed to dispose of that water because its tritium levels surpass the limit set by the government.
That’s why the utility is storing 920,000 tons of the water in more than 800 tanks. The water is expected to increase by up to about 100,000 tons a year. The government and the firm say that in a matter of years, Fukushima Daiichi will run out of space for tanks.
A government panel of experts has been discussing what to do with the water. The experts concluded that the technology for separating tritium cannot be put into practical use yet. They instead put several options on the table such as:
1) Diluting and releasing the water into the sea
2) Heating and evaporating the water
3) Burying the water deep underground
A report later compiled by the panel said releasing the water into the sea will make the most sense. Experts say this is the cheapest and quickest way among all the options. The question is, is it safe?
Tritium exists in the atmosphere. The government, TEPCO and the Nuclear Regulation Authority say tritium emits a weaker form of radiation than other radioactive substances. They say that even if tritium enters the human body, it will be incorporated into water and quickly released outside. Officials say therefore, tritium is likely to pose few health risks if its concentration is low.
In the past, nuclear power plants across Japan actually released water containing tritium after confirming its readings were below the limit.
NRA Chairman Toyoshi Fuketa has been calling on the government and TEPCO to make a quick decision, saying releasing the water into the sea after its tritium level falls below the limit is the only viable option. He thinks the approval process for the proposal is unlikely to take long, so it will have limited impact on the work to scrap the reactors.
Mounting distrust among fisheries
After the expert panel compiled its report, the government held public hearings to make a final decision. At a hearing held in the town of Tomioka in Fukushima Prefecture on August 30th, the proposal came under fire mainly from people in the fishing industry.
The head of the Fukushima Prefectural Federation of Fisheries Cooperative Associations said the proposed move will be a devastating blow to the local fishing industry. He said its past efforts will go to waste, and it will deprive the industry of its motivation for rebuilding businesses.
Fishermen in Fukushima suspended their operations after radioactive materials exceeding the government-set limits were detected in seafood caught off the prefecture following the 2011 accident. But in recent years, no fish from the area have been found to be highly radioactive. Now, fishermen can catch and ship most kinds of fish.
However, some consumers still hesitate to eat marine products from Fukushima. Fish landings are still about one-tenth of levels before the accident. Local fisheries fear that if TEPCO releases the water into the ocean, they will have to delay their plans to resume operations at full capacity and struggle again to make ends meet — even if the water is deemed safe.
The underlying problem is distrust towards the government and TEPCO. There have been numerous instances in which TEPCO withheld the fact that tainted water had leaked into the sea. Locals saw them as acts of betrayal. They fear that once TEPCO begins dumping the water into the sea, consumers may refrain from purchasing fishery products from Fukushima Prefecture even further.
Public distrust further deepened during the hearings. It came to light that the water stored in some of the tanks contains levels of radioactive substances, such as iodine that exceed the limit. This contradicts the explanation given by the government and TEPCO — that the water treatment system can reduce all radioactive substances to a level below the limit, except for tritium.
My understanding was that tritium was the only radioactive substance in the tanks that exceeds the government-set limits. I was not the only one who was confused. Other participants also expressed concerns that TEPCO may have been concealing the facts.
TEPCO officials explained that levels of some radioactive substances could exceed the limits if the water treatment filters are used continuously. They said that’s not a problem, adding that the goal is to reduce the risk of radiation exposure, and that they have been making the data public on their website.
After hearing this, I checked TEPCO’s website once again. There, I found the iodine levels, but they were buried in a massive amount of data, making it very difficult to find. TEPCO officials didn’t seem eager to provide a full explanation of what has happened so far.
But TEPCO’s claim that this isn’t a problem differs with the public’s view. Its attitude is worsening the problem.
TEPCO officials tend to make decisions based on technical considerations, which often fail to sufficiently acknowledge the concerns of the locals. The officials also appear reluctant to release information that is inconvenient for them. Unless they change their mindset, they will not be able to regain the public’s trust.
Steps TEPCO must take to regain trust
First and foremost, the government and TEPCO must provide thorough explanations and responses to the questions and opinions expressed in the hearings. They need to clarify why they didn’t proactively explain the level of radioactive substances and provide their exact levels and how they will deal with them.
In addition, the government should hold public hearings at various other locations and communicate more with the public. The latest round of public hearings was held only in Fukushima and Tokyo and this didn’t seem sufficient to regain public support.
Decommissioning of the crippled Fukushima Daiichi nuclear plant is a prerequisite for the reconstruction of areas devastated by the nuclear disaster. To this end, treatment of contaminated water is a must, and it needs be done swiftly. However, there will not be progress, no matter which method is taken, without the consent of the people affected by the nuclear disaster.
TEPCO and government officials must offer truthful updates as soon as they happen. While this sounds obvious, it’s the only way to regain people’s trust and resolve the problem of the accumulation of tainted water.
Work starts to decommission problem-plagued Monju reactor
“The Japan Atomic Energy Agency (JAEA) on Aug. 30 started work to decommission the Monju prototype fast-breeder reactor in Fukui Prefecture…
The decommissioning work is scheduled to take 30 years and cost $ 3.33 billion.”
Staff members of the Japan Atomic Energy Agency operate equipment to remove nuclear fuel assemblies from a storage tank at the plant of the Monju prototype fast-breeder reactor in Tsuruga, Fukui Prefecture, on Aug. 30.
August 30, 2018
The Japan Atomic Energy Agency (JAEA) on Aug. 30 started work to decommission the Monju prototype fast-breeder reactor in Fukui Prefecture, a once-promising project that struggled with problems, even in preparations for its dismantlement.
The work started a month later than scheduled because of a series of equipment trouble. The JAEA workers also face an enormous challenge because Japan has no experience in decommissioning a fast-breeder reactor.
The JAEA will use overseas experiences as a reference for the delicate process.
Before the start of the work, JAEA President Toshio Kodama told staff members in a speech at the plant in Tsuruga, “I want you to tackle this work by bracing yourselves.”
Monju had been a key facility in the government’s nuclear fuel recycling program.
Construction of the reactor started in 1985, but a series of accidents, including a sodium coolant leak in 1995, as well as cover-ups kept the reactor offline for most of its life.
In 2016, after 1 trillion yen ($9 billion) had been spent on the project, the government finally decided to abolish Monju.
The decommissioning work is scheduled to take 30 years and cost 375 billion yen.
One of the riskiest parts in the decommissioning process is handling the liquid sodium, which reacts strongly with water and air.
In the first of the four-stage decommissioning project, the JAEA will transfer 530 nuclear fuel assemblies, currently kept in the liquid sodium-filled nuclear reactor and storage tank, to a water-filled pool by fiscal 2022.
In the work that began on Aug. 30, the JAEA will remove 160 nuclear fuel assemblies from the storage tank, wash away the sodium, and place them in the pool.
From 2019, the agency will transfer nuclear fuel assemblies from the reactor to the storage tank and then to the pool.
In December this year, the JAEA will also start to transfer about 760 tons of sodium, which has not been exposed to radioactive substances, to its storage tank. Later, the agency will remove about 910 tons of radioactive sodium from the reactor and other equipment.
In the following stages, the agency will dismantle the nuclear reactor, the turbine and other facilities.
However, no decision has been made on how to dispose of the nuclear fuel removed from the reactor and the storage tank. Monju has used mixed oxide (MOX) fuel, which contains plutonium and currently cannot be reprocessed in Japan.
“It’s realistic to ask an overseas company to reprocess it,” said Toyoshi Fuketa, chairman of the Nuclear Regulation Authority, the government’s nuclear watchdog.
If reprocessing expenses in a foreign country are added, the overall decommissioning costs will sharply increase.
Foreign Trainees for Fukushima Clean-Up
Japanese firms used foreign trainees for Fukushima clean-up
13 July, 2018
Vietnamese in Japan for professional training were among those picking up soil as part of decontamination work at the crippled nuclear power plant
Four Japanese companies made foreign trainees who were in the country to learn professional skills take part in decontamination work after the Fukushima nuclear disaster, the government said on Friday.
The discovery is likely to revive criticism of the Technical Intern Training Programme, which has been accused of placing workers in substandard conditions and jobs that provide few opportunities for learning.
The misconduct was uncovered in a probe by the Justice Ministry conducted after three Vietnamese trainees were found in March to have taken part in clean-up work in Fukushima.
The Vietnamese were supposed to do work using construction machines according to plans submitted by the company.
“But they joined simple clean-up work such as removing soil without machines,” an official said.
A powerful earthquake in March 2011 spawned a huge tsunami that led to meltdowns at the Fukushima nuclear plant, causing the world’s worst such accident since Chernobyl in 1986.
One of the four companies has been slapped with a five-year ban on accepting new foreign trainees as it was found to have paid only 2,000 yen (US$18) per day to the trainees out of the 6,600 yen provided by the state as a special allowance for decontamination work.
The ministry is still investigating how many trainees in the other three firms were involved.
The four companies cited in the interim report no longer send foreign trainees to help with the radiation clean-up. It did not name the four firms.
The ministry has finished its investigation into 182 construction companies that hire foreign trainees, and will look into another 820 firms by the end of September.
Japan has been accepting foreign trainees under the government programme since 1993 and there were just over 250,000 in the country in late 2017.
But critics say the trainees often face poor working conditions including excessive hours and harassment.
The number of foreign trainees who ran away from their employers jumped from 2,005 in 2012 to 7,089 in 2017, according to the ministry’s survey. Many cited low pay as the main reason for running away.
The investigation comes as Japan’s government moves to bring more foreign workers into the country to tackle a labour shortage caused by the country’s ageing, shrinking population.
The government in June said it wanted to create a new visa status to bring in foreign workers, with priority given to those looking for jobs in sectors such as agriculture that have been hardest hit by the labour shortage.
The workers would be able to stay for up to five years, but would not be allowed to bring their family members.
The government put the number of foreign workers in Japan in 2017 at 1.28 million people.
But more than 450,000 of those are foreign spouses of Japanese citizens, ethnic Koreans long settled in Japan, or foreigners of Japanese descent, rather than workers coming to Japan simply for jobs. Another nearly 300,000 are students.
Japan firms used Vietnamese, foreign trainees at Fukushima cleanup
July 14, 2018
Four Japanese companies have been found to made foreign trainees take part in decontamination work after the Fukushima nuclear disaster.
The discovery is likely to revive criticism of the foreign trainee program, which has been accused of placing workers in substandard conditions and jobs that provide few opportunities for learning, the government said Friday.
The misconduct was uncovered in a probe by the Justice Ministry conducted after three Vietnamese trainees, who were in the country to learn professional skills, were found in March to have participated in cleanup work in Fukushima.
The Vietnamese were supposed to do work using construction machines according to plans submitted by the company.
“But they joined simple cleanup work such as removing soil without machines,” an official told AFP.
A powerful earthquake in March 2011 spawned a huge tsunami that led to meltdowns at the Fukushima nuclear plant, causing the world’s worst such accident since Chernobyl in 1986.
The justice ministry said after the discovery this March that decontamination work was not appropriate for foreign trainees.
One of the four companies has been slapped with a five-year ban on accepting new foreign trainees, and the ministry is still investigating how many trainees in the other three firms were involved.
The ministry has finished its investigation into 182 construction companies that hire foreign trainees, and will look into another 820 firms by the end of September.
Japan has been accepting foreign trainees under the government program since 1993 and there were just over 250,000 in the country in late 2017.
But critics say the trainees often face poor work conditions including excessive hours and harassment.
The number of foreign trainees who ran away from their employers jumped from 2,005 in 2012 to 7,089 in 2017, according to the ministry survey. Many cited low pay as the main reason for running away.
The investigation comes as Japan’s government moves to bring more foreign workers into the country to tackle a labor shortage caused by the country’s aging, shrinking population.
The government in June said it wanted to create a new visa status to bring in foreign workers, with priority given to those looking for jobs in sectors such as agriculture that have been hardest hit by the labor shortage.
The workers would be able to stay for up to five years, but would not be allowed to bring their family members.
The government put the number of foreign workers in Japan in 2017 at 1.28 million people.
But more than 450,000 of those are foreign spouses of Japanese citizens, ethnic Koreans long settled in Japan, or foreigners of Japanese descent, rather than workers coming to Japan simply for jobs. Another nearly 300,000 are students.
TEPCO to decommission Fukushima Daini plant
Tokyo Electric Power Company has revealed a plan to consider decommissioning all the reactors at its Fukushima Daini nuclear plant.
It is located about 12 kilometers south of the Fukushima Daiichi plant, which was critically damaged by the March 2011 earthquake and tsunami. All 4 reactors at the Daini plant have been halted since the disaster.
TEPCO President Tomoaki Kobayakawa informed Fukushima Governor Masao Uchibori of the plan at the prefectural government office on Thursday.
Kobayakawa noted that there have been negative rumors about Fukushima, and many evacuees are still unable to return home.
He told Uchibori his company has decided that keeping the Daini plant idle would hamper the reconstruction efforts in the prefecture.
The Fukushima prefectural assembly had adopted a petition to scrap the reactors at the Daini plant.
The municipal assemblies in Tomioka and Naraha, the towns that host the facility, have adopted a similar demand. The governor has repeatedly asked TEPCO and the central government in Tokyo to arrange the early decommissioning of the plant.
The utility, however, had refrained from saying clearly whether it would decommission the plant, citing the need to consider the government’s energy policies and the business environment.
TEPCO is now expected to scrap all 10 reactors in Fukushima Prefecture — 6 at the Daiichi plant and 4 at the Daini plant.
Remediating Fukushima—“When everything goes to hell, you go back to basics”
5/11/2018
It may take 40 years for the site to appear like “a normal reactor at the end of its life.”
A schematic of the Fukushima nuclear power plant hints at the complexity of decontamination and decommissioning operations.
TEPCO workers survey operations at reactor buildings.
Seven years on from the Great East Japan Earthquake of March 2011, Fukushima Daiichi nuclear power plant has come a long way from the state it was reduced to. Once front and center in the global media as a catastrophe on par with Chernobyl, the plant stands today as the site of one of the world’s most complex and expensive engineering projects.
Beyond the earthquake itself, a well understood series of events and external factors contributed to the meltdown of three of Fukushima’s six reactors, an incident that has been characterized by nuclear authorities as the world’s second worst nuclear power accident only after Chernobyl. It’s a label that warrants context, given the scale,
complexity, and expense of the decontamination and decommissioning of the plant.
How does a plant and its engineers move on from such devastation? The recovery initiatives have faced major challenges, constantly being confronted by issues involving radioactive contamination of everything from dust to groundwater. And those smaller issues ultimately complicate the remediation effort’s long-term goal: to locate and remove the nuclear fuel that was in the reactors.
A sense of scale
Jonathan Cobb, spokesperson for the World Nuclear Association, spoke with Ars about the scale of Fukushima, explaining that radioactive releases in Japan were much smaller than at Chernobyl, and the accident resulted in no loss of life from radiation: “Of course, this doesn’t take away from the enormous task currently being faced at Fukushima.”
The UN Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) reported in May 2013 that radiation exposure following the Fukushima accident didn’t cause any immediate health effects and that future health effects attributable to the accident among either the general public or the vast majority of workers are unlikely. A 2017 paper from UNSCEAR reports that these conclusions remain valid in light of continued research since the incident.
Even the most at-risk citizens, those living in Fukushima prefecture, are only expected to be exposed to around 10mSv as a result of the accident over their lifetimes. “For reference, the global average natural background radiation tends to be around 2.4mSv/year, but even 20mSv/year isn’t exceptional,” said Cobb.
Still, the accident was rated a 7 on the International Nuclear and Radiological Event Scale (INES), which is the highest rating possible, and designates it a Major Accident due to high radioactive releases. Estimates vary slightly, but Japan’s Nuclear Safety Commission report puts total releases at 570 petabecquerels (PBq) iodine-131 equivalent. (For comparison, Chernobyl released 5,200PBq iodine-131 equivalent.)
But the severity of the accident is probably most keenly felt in the scale of the cleanup. The incident has necessitated the ongoing cleanup and decommissioning of the plant—something that Tokyo Electric Power Company (TEPCO), the plant’s owner and operator, is responsible for. Even though the plant is seven years into the cleanup and has accomplished a great deal, we won’t see a conclusion for decades yet.
Damage to reactor Units 1-4 in the aftermath of the March 2011 earthquake.
In addition to damage to infrastructure and buildings, a large amount of wreckage was left strewn around the plant complex.
Remotely operated machines were involved in clean-up of the most contaminated areas.
A look inside the Primary Containment Vessel (PCV) of Unit 2.
A composite image of photographs taken inside the Primary Containment Vessel (PCV) of Unit 2.
A look at debris in the spent fuel pool of Unit 3.
Meltdowns and immediate priorities
Remarkably, seismic shocks of the magnitude 9 earthquake didn’t cause any significant damage to the earthquake-proofed reactors; rather, the tsunami knocked out power that precipitated reactor meltdowns in Units 1, 2, and 3. Subsequent explosions caused by hydrogen buildup (from zirconium cladding of fuel assemblies melting and oxidizing) in Units 1, 3, and 4 then expelled radioactive contamination, most of which fell within the confines of the plant.
Cobb explained that in the aftermath of this, the ongoing risk posed by radionuclides (notably, iodine-131 and cesium isotopes 134 and 137) depended on their half-lives. Iodine-131, with a half-life of just eight days, posed virtually no threat at all after just several months. It has been cesium-134, with a two-year half-life, and cesium-137, with a 30-year half-life, that have been the major focus of decontamination efforts. “Radioactive decay means that we’ve seen a reduction in contamination simply through time passing; at the plant, however, my expectation is that the majority of reduction has been due to efforts of TEPCO. Conditions have improved markedly and a sense of normalcy has returned.”
It’s useful to take stock of what TEPCO had to contend with from the outset. Lake Barrett, a veteran of the US nuclear energy industry who spent several years at the helm of decommissioning work at Three Mile Island reactor 2, is currently an independent special advisor to the Japanese Government and TEPCO board of directors. He told Ars, “When everything goes to hell on you, you go back to basics. You’re concerned with accident response and immediate recovery of the situation. Over the longer timeframe, the decontamination & decommissioning (D&D) focus shifts to a more deliberate approach to major technical challenges.”
Barrett explained that reactor stabilization at Fukushima—an imperative of the immediate recovery—has long since been achieved. Temperatures within the Reactor Pressure Vessels (RPVs) and Primary Containment Vessels (PCVs) of Units 1-3 are stable at between 15 to 30ºC, and there have been no significant changes in airborne radioactive materials released from reactor buildings. This qualifies as a ‘comprehensive cold shutdown’ condition.
Barrett explained how the issue of cooling is mostly non-existent at this point: “The three melted reactor cores emit less heat than a small car. Decay heat was a huge issue in the first weeks, but it’s no longer an issue. And while TEPCO still injects water onto the cores, this is more for dust suppression than anything else.”
With the reactors stable, early phases of TEPCO’s work simply involved debris clearing and restorative efforts throughout buildings and across the 3.5 square miles of the plant—both having been ravaged by the earthquake and tsunami. In the most contaminated places, remotely operated machines undertook most of the work. To reduce environmental contamination, they also removed top soils and vegetation, deforested the site, and then applied a polymer resin and concrete across much of the plant complex. This has locked contaminated material in place and limited the flow of groundwater through the site.
Other work has been more substantial. Units 1, 3 and 4 were blown apart and have had to be reinforced and encased, both for safety and to prevent spread of radioactive material. Although Unit 2 retained its roof, TEPCO decided to dismantle the upper building nonetheless, as it will facilitate removal of fuel from the reactor.
At the peak of these operations, some 7,450 persons worked at Fukushima. As operations have evolved, the workforce has declined to a not inconsiderable 5,000 daily personnel. With such levels of permanent staffing, it’s little wonder that a new rest-house, cafeteria, shops, and office building have all been built.
The efforts have, in a practical sense, meant that the majority of the site has transitioned to a stable, relatively risk-free environment. Describing the decommissioning as an “enormous challenge never before undertaken by humanity,” Seto Kohta of TEPCO told Ars: “We have overcome the state of chaos that ensued after the accident and have succeeded in reducing site dose levels to an average of less than 5μSv/h, with the exception of the vicinity of Units 1-4.” (Global background levels are <0.5µSv/h.)
TEPCO reports that the additional effective dose (i.e. additional to natural background radiation) at the plant’s boundary has declined to the target value of less than 1mSv/y.
This is not to say the plant is without signs of past problems—far from it. Felled trees sit waiting for incineration; huge mounds of soil lie under tarps; buildings retain marks of past trauma; and with environmental dosage a perennial concern, close to a hundred dose-rate monitors are positioned around the site.
Kohta also noted that while “95 percent of the site no longer requires the donning of full- or half-face masks or coveralls,” some level of protection is still required for working around the plant according to three levels of contamination. The vast majority of the plant grounds are in what’s termed Zone G, which requires just generic coveralls and disposable medical masks. Zone Y provides a perimeter around the Units 1-4 and necessitates heavier-duty coveralls and either full- or half-face masks. And lastly there is Zone R, closer to and including the reactor buildings, requiring double-layered coveralls and full-face masks.
A steel structure is built around Unit 1 as part of reconstruction works.
An outer shell is constructed around Unit 1.
Reconstruction work at Unit 4.
A labyrinth of subterranean tunnels and access points lie around reactor buildings.
The Little Sunfish submersible used for investigations at Unit 3.
A TEPCO schematic illustrates measures taken to manage groundwater.
An impermeable wall constructed of interlocking columns extends along the seafront to restrict contaminated water reaching the sea.
Above ground apparatus of the frozen wall which descends 30m and surrounds Units 1-4.
A visitor to the plant performs a low-tech check on the frozen wall.
The groundwater bypass pump works to reduce the amount of water leaking into the reactor buildings.
Temporary storage tanks for water pumped up via the groundwater bypass.
Flanged tanks of the sort used for indefinite storage of tritium-laced water arrive at the docks of Fukushima nuclear power plant.
Visitors from IAEA visit the ALPS water treatment facility where radionuclides are removed from contaminated water.
Defueling of the spent fuel pool at Unit 4 was performed in a conventional manner; it won’t be so easy at other Units where radiation and damage is more severe.
The giant fuel handling machine (background) and fuel handling crane (foreground) arrive for installation at Unit 3.
The final segment of the domed containment roof is lifted into place at Unit 3.
Reactor investigations
While they’re now stable in terms of nuclear activity, Units 1-3 remain highly contaminated. As such, while the structural integrity of these buildings has been restored, relatively little work has been undertaken within them. (One notable exception is removal of contaminated water from condensers, completed last year.)
Over recent years, a variety of remotely operated devices and imaging technologies have performed investigations of these units. The intention has been to gather information on internal physical and radiological conditions of the PCVs—the heavily reinforced bell-shaped structures that host reactors. TEPCO wants, and needs, to understand what has happened inside. Some things are known: once melted, fuel mixed with structural materials including steel and concrete to form something known as corium. But precisely where the corium ended up, how much there is, and whether it’s submerged are just some of the questions in play.
The International Research Institute for Nuclear Decommissioning (IRID), which was established in April 2013 to guide R&D of technologies required for reactor defueling and decommissioning, is supporting TEPCO in seeking answers. IRID is composed of multiple stakeholders, including Japanese utilities and the major nuclear vendors Hitachi, Mitsubishi, and Toshiba.
Naoaki Okuzumi, senior manager at IRID, described for Ars the investigative approaches and technologies. Early work utilized Muon tomography, which Okuzumi described as “a kind of standard practice applied to each unit… to locate high density material (fuel) within PCVs.” It yielded low-resolution data on the approximate location of corium. But with pixels representing 25cm-square cross-sections, the information has been useful only in so far as validating computational models and guiding subsequent robotic investigations.
The latter task hasn’t been easy. In addition to the challenge of navigating the dark, cramped labyrinths of tangled wreckage left behind, TEPCO has had to contend with radioactivity—the high levels act something like noise in electronic circuits. The wreckage has made access a challenge, too, although varying points of ingress have been established for each PCV.
The circumstances mean that TEPCO hasn’t been able to simply purchase an off-the-shelf kit for these investigations. ”An adaptive approach is required because the situation of each PCV is different… there is no standard with investigating the PCVs by using robots,” said Okuzumi, describing an approach that has translated into devices being specially developed and built in response to conditions of each PCV.
But they’re making progress. As recently as January 2018, corium was identified for the first time inside Unit 2 using an enhanced 13m-long telescopic probe and a revised approach designed to overcome problems encountered during investigations in 2017. The situation was hardly easier at Unit 3, where the PCV is flooded to a depth of around 6.5m. Here, it took a remotely operated, radiation-shielded submersible called ‘Little Sunfish’ to locate corium in July 2017.
Altogether the investigations—featuring a litany of robotic devices—have revealed that little fuel remains in any of the cores of Units 1-3. In Unit 2, a large amount of corium is present at the bottom of the RPV; in Units 1 and 3, almost all fuel appears to have melted through the RPVs entirely and into the concrete floor of PCVs beneath. The information is crucial, as we’ll come to see, for future deconstruction work at the reactors, but it continues to be extended as investigations continue.
PCV investigations at Unit 2
Pumps, ice-walls, and storage: Water management
One of TEPCO’s major concerns has been groundwater, which runs down from mountains west of the plant and can become contaminated by the low-lying reactors before flowing out to sea. Groundwater management has subsequently become one of TEPCO’s greatest efforts, as well as one of the most challenging of the tasks it has faced.
First off, it ought to be noted that marine environment monitoring for radionuclide concentrations near the plant and as far away as Tokyo indicate that levels are well within WHO standards. “The levels of radioactivity that have been found and can be attributed to Fukushima are absolutely dwarfed by natural levels of radioactivity in the water, or even levels of cesium that came from historic nuclear weapons testing,” noted Cobb.
Still, the effort to limit further contamination—seemingly driven as much by societal-political dynamics as safety considerations—remains paramount. To this end, measures have been deployed along three principles: remove sources of contamination, isolate water from contamination, and prevent leakage of contaminated water.
Some measures have been simple enough in design. Installation of an impermeable, underground wall along the sea front, completed in October 2015, is intended to keep groundwater that passes Units 1-4 from reaching the sea. Waterproofing pavement against rainwater is another widely applied step.
After this, solutions become more sophisticated. A groundwater bypass that intercepts and pumps up water before it reaches the reactors is a key development. This water is inspected for contamination before being discharged into the sea. By November 2017, more than 337,000 cubic meters of water had been released to the ocean in this way; this bypass reduced the amount flowing into the building basements by up to 100 tons per day and successfully reduced groundwater levels around the reactor buildings.
To further limit groundwater flow into reactors buildings, TEPCO actually froze the ground around them, creating a kind of frozen wall down to a depth of about 30 meters. Approximately 1,500 meters long, the wall is kept frozen by pipes filled with an aqueous solution of calcium chloride cooled to -30ºC. Freezing commenced in March 2016 and is now “99 percent complete,” according to Kohta.
On either side of the frozen wall, sub-drains and groundwater drains have been installed; they pump water up to keep it from reactor buildings and reaching the sea, respectively. Pumped water is purified at a purpose-built treatment facility. Barrett commented: “With water released from sub-drains and the bypass, there’s an agreement with the fishing industry that releases must be below 1,500 becquerels per liter. Negotiations took several years to agree that level was ‘clean’.”
All this has come at enormous expense, but according to TEPCO, it has been successful. Before any measures were implemented, inflow was around 400m3/day, Kohta told Ars. “The average amount of water flowing into [Units 1-4] for the period from December 2015 to February 2018, before the closure of the land-side impermeable wall, was 190m3/day, and it has decreased to 90m3/day after the closure for December 2017 to February 2018.”
At face value, it’s a sound outcome. As Kohta noted, the amount of contaminated water now being generated—a mix of groundwater, rainwater and water pumped into reactors for cooling—has decreased from about 520m3/day to about 140m3/day between last December and February. Even so, treating that amount of contaminated water is proving taxing.
Water treatment is happening at large-scale facilities that have been built onsite, including a multi-nuclide removal facility. Here, a so-called Advanced Liquid Processing System (ALPS) reduces concentrations of cesium isotopes, strontium, and other radionuclides to below legal limits for release. But one radionuclide remains: tritium.
Cobb explained: “The difficulty is that tritium is basically an isotope chemically identical to hydrogen, so it’s impractical to remove. Levels of tritium in that water are low, but nevertheless there’s great sensitivity to the suggestion that it be discharged.”
Without a feasible alternative for cleaning up the tritium, the (only) solution for ALPS-treated water has been storage. Well over a thousand tanks, each holding 1,200 cubic meters, now store tritium-laced water at the south end of the plant. Several years ago, these tanks hit the news because several were found to be leaking. Barrett acknowledged it as an unfortunate and avoidable incident resulting from use of flange-tanks. TEPCO has since moved to more sturdy welded-joint water storage tanks.
The ultimate plan for stored water is unknown; tritium has a half life of a dozen years, so physics won’t clean up the water for us. Some kind of controlled, monitored discharge—the likes of which is typical within the nuclear industry—is possible, according to Barrett.
Indeed, the International Atomic Energy Agency has endorsed such a plan, which was proposed by the Atomic Energy Society of Japan in 2013. The plan involved diluting tritiated water with seawater before releasing it at the legal discharge concentration of 0.06MBq/L and monitoring to ensure that normal background tritium levels of 10Bq/L aren’t exceeded.
Discussions at both national and international levels would need to come first. Part of the difficulty here harkens back to societal dynamics surrounding risk and contamination: “In nuclear there is no such thing as absolute zero—sensitivity goes down to the atom. This makes discussion about decontamination or levels of acceptable contamination difficult. There’s tritium in that water that’s traceable to the accident; it’s entirely safe, but for the time being, with the event still in recent memory, it’s not acceptable,” observed Barrett.
Toward permanent solutions
In some sense, much of the restoration of order at Fukushima has been superficial—necessary but concerned with handling consequences more than root causes (see, TEPCO interactive timeline). Ultimately, Fukushima’s reactors must be decommissioned.
Broadly, this work involves three phases: removing used fuel assemblies that are stored within ten-meter-deep spent fuel pools of each reactor building, management of melted-down reactors and removal of corium debris, and deconstruction of reactor buildings and the greater plant.
At Unit 4, spent fuel removal operations took around 13 months and concluded in December 2014. “When we began we didn’t know if fuel assemblies or racks were distorted. It turned out they weren’t, and we were able to remove all fuel conventionally without any issues at all. Actually, it went exceedingly well, concluding ahead of schedule and under cost,” recalled Barrett. In all, 1,533 fuel assemblies were removed and transferred to a common spent fuel pool onsite.
Spent fuel removal at Unit 4 was accomplished with conventional techniques.
Defueling of pools at Units 1 through 3, which suffered meltdowns, isn’t going to be as straightforward. For one, there’s some expectation of debris and circumstances requiring extraordinary removal procedures. “I wouldn’t be surprised if we find some structurally bent fuel assemblies caused by large pieces of concrete or steel,” said Barrett.
Additionally, although radiation in Unit 3 has been reduced sufficiently to allow rotating shifts of workers to install defueling equipment, the already painstaking operations will have to be conducted remotely. The same is likely true for Units 1 and 2.
At Unit 3, the next in line for defueling, preparation is already well underway. In addition to decontamination and installation of shielding plates, TEPCO has removed the original fuel handling crane, which had fallen into the pool seven years ago, and installed a new fuel handling crane and machine. An indication of extraordinary containment methods being used, workers have built a domed containment roof at Unit 3. TEPCO’s Kohta told Ars, “Removal of spent fuel [at Unit 3] is scheduled to begin from around the middle of 2018;” meanwhile, Unit 1 is also in a preparatory stage and Unit 2 will be handled last.
Further down the line still, corium will have to be removed from melted-down reactors. It’s a daunting task, the likes of which has never been undertaken before. The reactors held varying, but known, amounts of uranium oxide fuel, about 150 tonnes each. But how much extra mass the fuel collected as it melted through reactor vessels is uncertain.
“At TMI there was exactly 93 tonnes in the reactor. Once we were done digging out fuel debris, we’d removed 130 tonnes. At Fukushima, I expect maybe a factor of five to ten more mass in core debris. It’s an ugly, ugly mess underneath the PCVs,” suggested Barrett.
High-powered lasers, drills and core boring technologies for cutting, and strong robotic arms for grappling and removing corium are already under development, according to IRID, but precise methodologies remain undecided.
The original plan, Barrett explained, was to flood PCVs and work underwater—a conventional nuclear operations technique that affords protection from contamination. But this requires water-tight PCVs, something that cannot be practically achieved at Fukushima. Discussions also continue over whether a side or top-down entry would be best. “Altogether, we don’t have enough physical data about PCVs to commit to a final decision,” said Barrett, referring back to the need for continued PCV investigations. According to Kohta, fuel debris removal isn’t scheduled to commence before the end of 2021.
Without doubt, the road ahead of TEPCO is a long one, beset with challenges greater than those faced to date. The Mid- and Long-Term Roadmap—the Japanese state-curated document outlining the decommissioning of Fukushima—envisions operations stretching a full 30-40 years into the future. Some have suggested it’s an optimistic target, others say that the plan lacks details on key, long-term issues such as permanent solid-waste storage beyond the onsite repository currently being employed. Certainly it is the case that key decisions remain.
For his part, Barrett concluded: “I believe that the 40-year timeframe is reasonable for a scientifically based decommissioning; that’s to say, to reach a point similar to that of a normal reactor at the end of its life. That’s not reaching the point of a green field where you’d want to put a children’s school. Could it be a brown-field, industrial site, though? Yes it could. That’s a rational, reasonable end point.”
By all accounts, it is hard to gauge the costs for the Fukushima clean-up. Kohta told Ars that works completed to date have cost about 500.2 billion yen, or $4.7 billion—a tremendous sum, to be sure, but fractional compared to the estimate of 8 trillion yen ($74.6 billion) approved by the Japanese state last May for the complete decommissioning of Fukushima Daiichi.
Total tally for Fukushima decommission is $75 billion
April 2, 2018
The decommissioning of the Fukushima nuclear power plant will cost an annual $2 billion (220 billion yen) until 2021, an unnamed source told the Japan Times.
Half of the money will be used to tackle the radioactive water buildup at the site of the plant and for removing radioactive fuel from the fuel pools. A small amount of funds will be used to research ways of retreating melted fuel from the reactors that got damaged during the 2011 tsunami disaster.
The $6 billion for the three years is only part of the total estimated cost for taking Fukushima out of operation.
The total decommissioning tally came in at $75 billion (8 trillion yen), as estimated by the specially set up Nuclear Damage Compensation and Decommissioning Facilitation Corp (NDF). That’s four times more than the initial estimate of the costs around the NPP’s decommissioning.
Now the operator of Fukushima, Tepco, and the NDF are due to submit their financial plan for the facility to the government for approval by the energy industry minister.
In addition to the $6 billion allocated for the cleanup, Tepco will spend another $1.88 billion (200 billion yen) on preparing to start extracting the melted fuel from the three damaged reactors. This seems to be the biggest challenge for the cleanup efforts because of the still high radiation levels as well as technical difficulties.
Tepco is still reeling from the effects of the 2011 tsunami and resulting nuclear meltdown. Around 15,000 people died in March 2011, when a magnitude-9 quake caused a deadly tsunami and erased the coastline in the area of the nuclear power plant.
At the end of 2016, the Japanese government revised upwards the total costs of the disaster to $192 billion (21.5 trillion yen), stepping up pressure on Tepco to clean up its act and implement urgent reforms to its safety procedures.
TEPCO’s priority is, and will be, to decommission crippled reactors
March 14, 2018
Toyoshi Fuketa, chairman of the Nuclear Regulation Authority (NRA), told a news conference last week that the Fukushima nuclear accident is far from over, and that it would be a mistake to think of it solely as something that occurred seven years ago.
On the surface, it appears as if a semblance of order has been restored at the Fukushima No. 1 nuclear power plant, the site of one of the most catastrophic nuclear accidents in history. Except for in and around the crippled reactor buildings, workers can now go almost anywhere on the premises without protective clothing.
Measures have been set in place to cool debris from the reactor cores and spent nuclear fuel in storage pools.
The NRA has considerably downgraded the risk of the plant spewing massive amounts of radioactive substances again.
In reality, however, the road to reactor decommissioning is long and arduous.
“We are still in no state to see the peak of the mountain,” Fuketa said. “We don’t even know what sort of uphill slope awaits us.”
The government last year revised its timetable for reactor decommissioning. The basic target of “decommissioning in 30 to 40 years” has not changed, but the removal of spent fuel from the No. 1 and No. 2 reactor pools will not begin until fiscal 2023, three years later than initially projected.
With the state of the immediate surroundings of the reactor cores still being understood only vaguely, any decision on concrete steps for the removal of debris has been postponed by one year to fiscal 2019.
The volume of water containing radioactive substances, stored in 850 tanks, has reached 1 million tons, and it will only keep growing with the passage of time. The bloating costs of reactor decommissioning will translate into a heavier taxpayer burden. But trying to rush the job will raise the risk of exposing workers to radiation and inviting accidents.
Tokyo Electric Power Co. (TEPCO), the operator of the Fukushima No. 1 plant, started last summer to publicly announce troubles encountered by cleanup crews as “deviations from the norm.”
Such issues include injuries or acute illnesses suffered by workers, vehicular collisions while multiple operations are being simultaneously run, and the deterioration of machinery used in emergencies. While most of these cases do not constitute legal violations, they are being reported almost daily.
Ensuring the safety of workers is TEPCO’s top priority. The utility must also pay close attention to other factors while proceeding steadily with reactor decommissioning, such as reducing the risks of environmental pollution. It is also crucial for the company to explain the situation to local residents as well as the general public and heed their voices.
However, some within the NRA, as well as the Nuclear Reform Monitoring Committee, a group of domestic and overseas experts who advise TEPCO’s board of directors, have frequently expressed concern that TEPCO may start prioritizing its corporate profitability.
For TEPCO, which has been bailed out effectively under government control, decommissioning the reactors at the Fukushima No. 1 plant should be its foremost task. As the very party that allowed the nuclear disaster to occur, it is obviously its responsibility to invest sufficient capital and manpower in this undertaking.
In 2013, when Tokyo was bidding for the 2020 Olympics, Prime Minister Shinzo Abe declared in his speech that the issue of contaminated water at the Fukushima plant was “under control.”
But such optimism was hardly warranted, given the difficulty that became clear in disposing of the radioactive water.
This must be firmly borne in mind by TEPCO, as well as the Ministry of Economy, Trade and Industry, which oversees the utility, and the NRA.
Seven years on, no end in sight for Fukushima’s long recovery
March 11, 2018
Japan faces myriad challenges to decommissioning and decontamination
Removing nuclear fuel from the Fukushima Daiichi power plant will take 30 to 40 years, ‘Tepco says’.
TOKYO — After helping shape nuclear policy in post-Fukushima Japan, Shunichi Tanaka, a former chief of the country’s nuclear watchdog, took on another tough assignment — moving to a village still struggling from the 2011 nuclear disaster to help with its recovery effort.
In February, Tanaka, who chaired the Nuclear Regulation Authority until last September, became a reconstruction adviser in the tiny village of Iitate, Fukushima Prefecture. Like many in surrounding localities, Iitate residents were ordered to evacuate after a powerful earthquake and tsunami on March 11, 2011, led to meltdowns at Tokyo Electric Power Co. Holdings’ Fukushima Daiichi nuclear power plant. To date, only around 10% of residents have returned.
“It won’t be easy to make life like it was before the disaster,” Tanaka said. Nonetheless he will help the village move forward by offering advice on nuclear decontamination and the ongoing dangers of radiation. He also acts as a go-between for the village and the national government.
“I’m a jack of all trades,” he says.
Shunichi Tanaka, former chairman of the Nuclear Regulation Authority.
In his former role at the NRA, Tanaka spearheaded an overhaul of Japan’s nuclear regulatory scheme, setting tough new standards for nuclear power operations intended to prevent another Fukushima-like accident. To date, 12 reactors have cleared the new standards. And yet the public remains largely distrustful of nuclear power — a problem Tanaka believes he can address by building up trust in the areas directly affected by the Fukushima disaster.
Challenges in that region, however, remain immense, none more so than decommissioning the damaged power plant. This involves the unprecedented feat of removing and safely storing the plant’s nuclear fuel, part of which has melted and escaped from the reactors it originally powered.
Back in September, Tepco and the national government reaffirmed their previous timeline for the cleanup, estimating the decommissioning process would take 30 to 40 years to complete. But the herculean nature of this task is becoming increasingly apparent. Nuclear fuel is too radioactive for humans to approach even when wearing protective gear, and must be handled by remotely controlled robots. But precision machinery is sensitive to radiation, and developing technology able to withstand conditions at the Fukushima site has proved intensely challenging.
“I truly cannot say” whether decommissioning can be wrapped up on a 30- to 40-year timeline, and “it is important to be honest,” said Hajimu Yamana, head of the government-backed Nuclear Damage Compensation and Decommissioning Facilitation Corporation.
The process is also extremely costly. The Ministry of Economy, Trade and Industry in 2016 pegged costs such as decommissioning and victims’ compensation related to the disaster at 21.5 trillion yen ($202 billion at current rates), nearly double its initial estimate of 11 trillion yen.
Work to remove and store melted fuel, set to begin as soon as 2021, and assorted other decontamination tasks could pile on additional expenses, depending on how they progress. The Japan Center for Economic Research believes the real cost could be as high as 70 trillion yen. Much of this would be borne by taxpayers, who require a convincing explanation of why costs are so high.
Decontaminating the soil poses another thorny problem. Roughly 640,000 cu. meters of contaminated soil, divided into 1-cu.-meter packages, has been delivered to an interim government storage facility between October and January. Yet up to 22 million cu. meters of contaminated earth remains to be treated in Fukushima Prefecture alone, a far larger amount than can be adequately handled at the current pace of work.
The government has not even locked down the roughly 1,600 hectares of land needed to complete the facility, which is itself only a temporary solution. Tokyo has pledged that Fukushima Prefecture will not be the final resting place for any of this soil, and looks to move it to a more permanent home elsewhere within 30 years. But even initial steps toward choosing such a site remain to be taken.
“It would be difficult and unrealistic to ask other prefectures to shoulder the burden,” Tanaka said. He has proposed decontaminating the soil and using it to fill in wetlands, turning them into farmland or meadowland that would provide a living for residents returning to evacuated areas. An influx of foreign engineers working on decommissioning the Fukushima plant could also give rise to new industry. But whatever plans emerge, the highest and most important hurdle could be simply getting started.
Decommissioning Fukushima reactors will take time but progress continues
In this July 27, 2017 file photo, contaminated water storage tanks are seen on the Fukushima No. 1 nuclear plant grounds, in Okuma, Fukushima Prefecture
March 11, 2018
Over the past year, clumps appearing to be melted fuel debris have been found inside three reactors at Tokyo Electric Power Co. (TEPCO)’s Fukushima No. 1 Nuclear Power Plant — which will soon mark seven years since being struck by disaster, on March 11.
However, the specific properties of the fuel debris remain unclear, and the decision on how to go about extracting the material has been delayed. The mammoth task of decommissioning the nuclear power plant, which is expected to take 40 years, is moving at a sluggish pace.
Removing the debris is the most difficult part of the decommissioning process. During an internal probe of nuclear containment vessels at the site, which involved robots, debris-like clumps were discovered in the No. 2 and No. 3 reactors, and sand-like sediment was found spread across the bottom of the No. 1 reactor. However, the specific properties and distribution of the debris has not yet been ascertained.
In September 2017, the government and TEPCO re-examined its decommissioning operation schedule. Initially, it was planned that the reactor which would undergo decommissioning first, as well as the method, would be decided by the end of the first half of fiscal 2018. However, the decision was delayed until the end of fiscal 2019 due to a lack of information concerning the situation inside the reactors, as well as the debris.
Meanwhile, as part of countermeasures against contaminated water, an ice wall designed to block the flow of underground water has almost been completed. In addition, a sub-drain well that pumps away subterranean water has been reinforced. As a result, the volume of underground water flowing into the buildings housing the reactors has been reduced from roughly 400 metric tons per day, which was the figure immediately after the outbreak of the disaster, to about 80 tons per day — indicating that there has been some progress regarding the “entrance” policy designed to reduce the volume of contaminated water generated at the site.
However, the “exit” policy, designed to dispose of treated water after most of the radioactive materials have been removed from the contaminated water, is still up in the air. The major issue concerning this policy is that the radioactive material tritium (tritiated hydrogen) cannot be removed, in principle, from treated water.
Tritium is something that appears in the natural world. Based on the fact that it has been flowing out into the sea from nuclear facilities across the globe, the Nuclear Regulation Authority stresses that Fukushima’s treated water containing tritium should be diluted and flushed out into the sea. However, due to fears that this could damage the reputation of the local fishing industry, the government and TEPCO continue to keep the treated water stored in tanks.
As a result, the amount of radioactive water stored at the site, including the treated water, has risen to about 1.05 million tons, and the number of tanks has increased to roughly 850. The government has set up a committee looking into how to dispose of the treated water, but consensus has not yet been reached.
Meanwhile, with regard to the extraction of fuel from pools of spent nuclear fuel, removal is planned from the No. 1 and No. 2 reactors in fiscal 2023, three years later than initially scheduled, and from the No. 3 reactor sometime around mid-FY2018. Special cranes are being installed to prepare for the job.
Debris to be removed from side of Fukushima reactors
Workers wearing protective suits and masks work on the No. 2 reactor building at the Fukushima Daiichi nuclear power plant.
TOKYO – A state-backed entity tasked with supporting the decommissioning of the Fukushima nuclear power station proposed Thursday that melted fuel be removed from the side of three of the crippled reactors as part of the process to scrap the complex.
Based on a formal proposal, the government and the plant operator Tokyo Electric Power Company Holdings Inc (TEPCO) will determine specific approaches to carry out the process on each reactor next month and update the plant decommissioning road map.
Under its strategic plan for 2017, the Nuclear Damage Compensation and Decommissioning Facilitation Corp called for the removal of the fuel by partially filling the three reactors with water to cover some of the nuclear debris while allowing access to carry out the work.
The entity also pointed out that the decommissioning work requires phased efforts while maintaining flexibility, as the project still faces many uncertainties.
The extraction work from the Nos. 1-3 reactors at the Fukushima Daiichi nuclear complex, which suffered meltdowns following the massive 2011 earthquake and tsunami disaster, is seen as the most difficult step toward the ultimate goal of decommissioning the entire complex, set to take at least 30 to 40 years to complete.
The government and TEPCO are currently aiming to start the extraction work from 2021.
Under the plan, the Nuclear Damage Compensation and Decommissioning Facilitation body proposed using a remotely controlled apparatus to shave debris from the underside of the lower section of the reactors’ containment vessel while controlling the level of water.
Debris remains not only in the reactors’ pressure vessel but also piled and scattered at the bottom of the containment vessel that houses the reactor vessel.
As for debris left in the reactors’ pressure vessel, the entity will consider removing it from the upper part of the reactors, it said.
The decommissioning body had previously considered a strategy to fill the containment vessel with water as water is effective in containing radiation, but it has shelved the idea as the reactor containers are believed to have been damaged and would leak.
Following a magnitude-9.0 earthquake in March 2011, tsunami inundated the six-reactor plant, located on ground 10 meters above sea level, and flooded power supply facilities.
Reactor cooling systems were crippled and the three reactors suffered fuel meltdowns, while hydrogen explosions damaged the buildings housing the Nos. 1, 3 and 4 reactors.
The Nuclear Damage Compensation and Decommissioning Facilitation entity was established after the Fukushima crisis, the worst nuclear disaster since Chernobyl, to help the utility pay damages. The state-backed entity holds a majority stake in the operator.
https://japantoday.com/category/national/Debris-to-be-removed-from-side-of-Fukushima-reactors
Muscle robots’ being developed to remove debris from Fukushima reactors
Hitachi-GE testing variety of simply structured, radiation-resistant equipment
The Unit 1 reactor building at the Fukushima Dai-ichi nuclear power plant of the Tokyo Electric Power Co. (TEPCO) in Okuma town, Fukushima prefecture, June 21, 2017.
TOKYO — A joint venture between Japanese and American high-technology power houses Hitachi and General Electric is developing special robots for removing nuclear debris from the Fukushima Daiichi nuclear power plant, the most difficult task in decommissioning the plant’s six reactors, three of which suffered core meltdowns in the March 2011 accident.
The machines under development by Hitachi-GE Nuclear Energy are called “muscle robots,” as their hydraulic springs operate like human muscles. The company, based in Hitachi, Ibaraki Prefecture, is stepping up efforts to complete the development project in time for the start of debris removal in 2021.
Hitachi-GE is testing the arms of the robots at a plant of Chugai Technos, a Hiroshima-based engineering service company, located a 30-minute drive from the center of the city. The testing is taking place in a structure with a life-size model of the primary containment vessel of the No. 1 reactor at the Fukushima plant. The robots awkwardly move about, picking up concrete lumps standing in for fuel debris.
“The robots are based on a concept completely different from those of conventional robots,” said Koichi Kurosawa, a senior Hitachi-GE engineer heading the development project. Hydraulics are being used because electronics cannot survive in the extreme environment inside the reactors.
“Asked if the robots are applicable to other nuclear power plants, I would say the possibility is low,” Kurosawa said, noting that the robots are designed to work amid intense radiation.
New challenges
While Hitachi-GE has built many nuclear reactors, it is encountering a variety of new challenges in developing the muscle robots simply because of the tough work required to retrieve fuel debris.
In the nuclear accident caused by the March 2011 earthquake and tsunami, cooling the fuel rods became impossible, and melted uranium fuel dropped from them. Some of the fuel broke through nuclear reactor pressure vessels and solidified as fuel debris containing uranium and plutonium.
The debris is estimated to weigh more than 800 tons in total. The insides of the PCVs at the Fukushima plant are directly exposed to the debris and are emitting radioactivity strong enough to kill a human within a few minutes.
The International Research Institute for Nuclear Decommissioning, a Tokyo-based research institute for decommissioning nuclear plants, and three reactor makers — Hitachi-GE, Toshiba and Mitsubishi Heavy Industries — have been attempting to ascertain conditions inside the reactor buildings at the Fukushima plant by means of camera- and dosimeter-equipped equipment.
Fukushima nuke plant decommissioning still has long way to go
Mainichi Shimbun reporters visited the Fukushima No. 1 Nuclear Power Plant on July 27. While the working environment at the station has improved, plant operator Tokyo Electric Power Co. (TEPCO) still has a mountain of problems to tackle, such as removing melted nuclear fuel from the No. 1 to No. 3 reactors and treating contaminated water.
https://mainichi.jp/english/articles/20170811/p2a/00m/0na/025000c
Japan’s nuclear safety chief raps Tepco’s attitude on Fukushima No. 1 crisis, restarting other reactors
The head of the Nuclear Regulation Authority told Tepco’s top management he questions their attitude toward decommissioning the Fukushima No. 1 nuclear power plant and the company’s ability to resume operating its other reactors.
“I feel a sense of danger,” NRA Chairman Shunichi Tanaka said during a special meeting Monday with the top management of Tokyo Electric Power Company Holdings Inc.
Tanaka also said Tepco does “not seem to have the will to take the initiative” toward decommissioning the crippled nuclear power station that suffered three reactor meltdowns in March 2011.
Tepco Chairman Takashi Kawamura and President Tomoaki Kobayakawa attended the meeting. The authority felt it is necessary to hear from the top executives before it could make a decision on whether to approve Tepco’s plan to resume operation of reactors 6 and 7 at its massive Kashiwazaki-Kariwa plant in Niigata Prefecture.
Tepco filed for a safety assessment of the two reactors in September 2013 to reactivate them, hoping to restore its financial condition as it needed massive funds to pay compensation related to the Fukushima disaster and to scrap the plant.
The NRA’s safety screening found that Tepco failed to report insufficient earthquake resistance for an emergency response center at the Niigata complex even though it knew about the insufficiency for three years.
In June, Tepco submitted to the watchdog its revised safety measures for the Kashiwazaki-Kariwa complex.
“An operator lacking the will to take the initiative does not have the right to resume operation of nuclear reactors,” Tanaka said.
Tepco’s chairman responded by saying: “There are citizens who believe nuclear power is necessary. Operating reactors is our responsibility.”
But Kawamura also admitted there is room for only two more years’ worth of space in the tanks to accommodate the contaminated water building up at Fukushima No. 1.
During the meeting the NRA asked Tepco’s management about the company’s safety measures for the Niigata complex — the biggest nuclear power station in the world — as well as its safety awareness.
Tanaka said the NRA does consider Tepco’s responses at the meeting as sufficient and requested that it submit further explanations on its plan to decommission Fukushima No. 1 and resume operation of the two reactors at Kashiwazaki-Kariwa.
Tanaka plans to conduct on-site checkups at the two reactors, saying, “Tepco, which caused the (Fukushima) accident, is not an ordinary operator.”
The two boiling water reactors at the Niigata plant are the same type that suffered core meltdowns at Fukushima No. 1, and no such reactors have cleared the authority’s safety screening since the 2011 crisis.
http://www.japantimes.co.jp/news/2017/07/10/national/japans-nuclear-safety-chief-raps-tepcos-attitude-fukushima-no-1-crisis-restarting-reactors/
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