Regulator urges Tepco to release treated radioactive water from damaged Fukushima No. 1 nuclear plant into the sea — The Japan Times

” A decision should be made sometime this year over whether to release into the sea water containing radioactive tritium from the crisis-hit Fukushima No. 1 nuclear plant, the chief of Japan’s nuclear regulator said Thursday, emphasizing it would pose no danger to human health.

“We will face a new challenge if a decision (about the release) is not made this year,” Nuclear Regulation Authority Chairman Toyoshi Fuketa told Naraha Mayor Yukiei Matsumoto, referring to the more than 1 million tons of coolant water and groundwater that has accumulated at the crippled facility. Naraha is located close to the Fukushima No.1 plant.

Fuketa said releasing the water into the sea after dilution is the only solution, saying “it is scientifically clear that there will be no impact on marine products or to the environment.”

Currently, Fukushima plant operator Tokyo Electric Power Company Holdings Inc. regularly filters contaminated coolant water and ground water from the damaged plant. The processed water is stored in hundreds of water tanks set up within the plant’s compound.

Dangerous radioactive materials are removed during filtration, but tritium — which is difficult to separate from water but relatively harmless to human health — remains.

“(Tepco) has been building new tanks, but it will eventually run out of land,” an NRA official later told The Japan Times.

With limited storage space for water tanks, observers warn that tritium could start leaking from the Fukushima plant.

The nuclear regulator’s chief underlined the need for the government and Tepco to make a decision quickly, saying, “It will take two or three years to prepare for the water’s release into the sea.”

At other nuclear power plants, water containing tritium is routinely dumped into the sea after it is diluted. The regulator has been calling for the release of the water after diluting it to a density lower than standards set by law.

According to the NRA, an average pressured-water reactor for commercial use in Japan usually dumps 60 trillion becquerels of tritium a year into the sea.

Local fishermen are, however, worried about the negative impact from the water discharge — in particular the effect of groundless rumors regarding the safety of marine life near the Fukushima plant. In the face of their opposition, Tepco has not yet reached a decision on how to deal with the stored water.

At the Fukushima plant contaminated water is building up partly because groundwater is seeping into the reactor buildings and mixing with water that has been made radioactive in the process of cooling the damaged reactors.

According to the NRA, there were 650 water tanks within the compound at the Fukushima No. 1 plant as of last month.

The density of tritium in the water ranges from 1 million to 5 million becquerels per liter. Legal restrictions require a nuclear power plant to dump tritium-tainted water after diluting it to 60,000 becquerels per liter, according to the NRA.

On March 11, 2011, tsunami inundated the six-reactor plant, which is located on ground 10 meters above sea level, and flooded its power supply facilities.

Reactor cooling systems were crippled and the Nos. 1 to 3 reactors suffered fuel meltdowns in the world’s worst nuclear catastrophe since the 1986 Chernobyl disaster. ”

by Kyodo, The Japan Times

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Koizumi’s nuclear power questions – The Japan Times editorial

” While political repercussions continue over former Prime Minister Junichiro Koizumi’s surprise calls for ending nuclear power generation in Japan, what the once popular leader points out are all sensible and legitimate questions about Japan’s energy policy that remain unanswered by members of the Abe administration. Any energy policy that fails to squarely answer the questions posed by Koizumi will not have any credibility.

Koizumi, who kept largely out of the media spotlight after retiring as lawmaker in 2009, has been speaking out in recent months that Japan should end its reliance on nuclear power. He says the Fukushima nuclear disaster changed his perception of nuclear power as a low-cost and safe source of energy and now says, “There is nothing more costly than nuclear power.” He urges the government to divert the massive energy and money needed to maintain nuclear power in Japan into more investments in the development and promotion of renewable energy sources.

Many of his former Liberal Democratic Party colleagues initially tried to dismiss Koizumi as a retired politician who has nothing to do with the party today. Prime Minister Shinzo Abe, who served in key Cabinet and LDP positions during Koizumi’s 2001-2006 rule, said it is “irresponsible” to commit to ending nuclear energy at this point. Meanwhile, hopes have emerged within the opposition camp that an alliance with Koizumi — who drew strong popular support while in office — on the zero nuclear agenda could provide them with ammunition against the LDP’s dominance in the Diet.

The political ripple effects — and some criticism over his flip-flop after promoting nuclear power while in office — aside, what seems missing in the controversy are discussions on the very real and pressing issues highlighted by Koizumi. He points to poor prospects for finding a permanent storage site for highly radioactive waste after spent fuel is reprocessed. This problem — for which Japan’s nuclear power industry has long been likened to a “condominium without a toilet” — has been set aside since well before the Fukushima crisis.

Abe has told the Diet that a technology has been established to store such waste in geological layers deep underground. Koizumi says the problem is that despite the existence of this technology, the government has been unable for more than a decade to find a candidate site anywhere in Japan. And this technology, Koizumi says, might be problematic in this quake-prone country — a point that Abe conveniently neglects to mention. Given the safety concerns over nuclear power following the triple meltdowns at the Fukushima plant, it is even more doubtful that a candidate site will ever be found, Koizumi says. Thus radioactive waste will continue to pile up as long as nuclear power plants are operated.

Japan’s nuclear fuel cycle program is at a standstill. Completion of a fuel reprocessing plant in Rokkasho, Aomori Prefecture, has been delayed for years, and the Monju fast-breeder reactor in Tsuruga, Fukui Prefecture, has been idled for much of the time since a sodium leak and fire in 1995. Meanwhile, storage space for spent nuclear fuel from reactors around the country, and in the Rokkasho complex, is nearly 70 percent full.

As Koizumi points out, the myth that nuclear power is cheaper than other sources of energy is thrown in doubt when the expenses for siting nuclear plants, their future decommissioning and waste disposal are included. And on top of this there is the massive cost of dealing with the aftermath of the Fukushima No. 1 meltdowns, including compensation, which far exceeds the financial capacity of its operator, Tokyo Electric Power Co. This is necessitating the injection of a huge amount of taxpayer money.

Abe’s rebuttal is that increased fossil fuel imports for thermal power generation to make up for the nuclear plant shutdowns is costing the nation trillions of yen a year. But his rhetoric does not answer the question whether nuclear power is really the affordable source of energy — as it has long been touted to be by the government — especially after the costs of compensation and decontamination in the wake of the Fukushima nuclear crisis are taken into account.

Abe has vowed to scrap the nuclear phaseout policy of the Democratic Party of Japan-led administration that his LDP ousted from power last year. But the prime minister has yet to present a new vision for the nation’s energy policy — except to say that he would reduce as much as possible Japan’s reliance on nuclear power while maximizing energy-saving efforts and development of alternative energy.

While the future of Japan’s energy policy remains elusive and the Fukushima nuclear crisis is continuing, Abe has been pushing for the sale of Japanese nuclear power plant technology overseas as part of his bid to boost infrastructure exports. When Mitsubishi Heavy Industries and France’s Areva clinched a joint-venture deal in October to build a nuclear power plant with four advanced reactors in Turkey, Abe said Japan “is responsible for helping improve the safety of atomic power in the world by sharing the experience and lessons” from the disaster at the Fukushima plant — whose situation he has described as “under control.”

At home the Abe administration and the LDP are pushing for the restart of some idled nuclear reactors once they have cleared a new set of safety criteria, even though radiation-contaminated water continues to leak from the Fukushima compound nearly 2½ years after the meltdowns.

Abe should lay out a new energy vision that will fully address the doubts about nuclear power raised by Koizumi. His legitimate concerns are likely shared by a large part of the public — a majority of whom, according to media surveys, oppose restart of the idled nuclear reactors. As Koizumi says, only Japan’s political leaders can set the direction for the nation’s energy policy. The Abe administration has an obligation to choose a path that ensures Japan will not have to contend with another nuclear power plant disaster in the future. ”

by The Japan Times

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*The Fukushima nuclear meltdown continues unabated – Helen Caldicott, Global Research News

Dr. Helen Caldicott really tells it how it is. No sugarcoating in this article, just the cold, hard facts.

” Recent reporting of a huge radiation measurement at Unit 2 in the Fukushima Daichi reactor complex does not signify that there is a peak in radiation in the reactor building.

All that it indicates is that, for the first time, the Japanese have been able to measure the intense radiation given off by the molten fuel, as each previous attempt has led to failure because the radiation is so intense the robotic parts were functionally destroyed.

The radiation measurement was 530 sieverts, or 53,000 rems (Roentgen Equivalent for Man). The dose at which half an exposed population would die is 250 to 500 rems, so this is a massive measurement. It is quite likely had the robot been able to penetrate deeper into the inner cavern containing the molten corium, the measurement would have been much greater.

These facts illustrate why it will be almost impossible to “decommission” units 1, 2 and 3 as no human could ever be exposed to such extreme radiation. This fact means that Fukushima Daichi will remain a diabolical blot upon Japan and the world for the rest of time, sitting as it does on active earthquake zones.

What the photos taken by the robot did reveal was that some of the structural supports of Unit 2 have been damaged. It is also true that all four buildings were structurally damaged by the original earthquake some five years ago and by the subsequent hydrogen explosions so, should there be an earthquake greater than seven on the Richter scale, it is very possible that one or more of these structures could collapse, leading to a massive release of radiation as the building fell on the molten core beneath. But units 1, 2 and 3 also contain cooling pools with very radioactive fuel rods — numbering 392 in Unit 1, 615 in Unit 2, and 566 in Unit 3; if an earthquake were to breach a pool, the gamma rays would be so intense that the site would have to be permanently evacuated. The fuel from Unit 4 and its cooling pool has been removed.

But there is more to fear.

The reactor complex was built adjacent to a mountain range and millions of gallons of water emanate from the mountains daily beneath the reactor complex, causing some of the earth below the reactor buildings to partially liquefy. As the water flows beneath the damaged reactors, it immerses the three molten cores and becomes extremely radioactive as it continues its journey into the adjacent Pacific Ocean.

Every day since the accident began, 300 to 400 tons of water has poured into the Pacific where numerous isotopes – including cesium 137, 134, strontium 90, tritium, plutonium, americium and up to 100 more – enter the ocean and bio-concentrate by orders of magnitude at each step of the food chain — algae, crustaceans, little fish, big fish then us.

Fish swim thousands of miles and tuna, salmon and other species found on the American west coast now contain some of these radioactive elements, which are tasteless, odourless and invisible. Entering the human body by ingestion they concentrate in various organs, irradiating adjacent cells for many years. The cancer cycle is initiated by a single mutation in a single regulatory gene in a single cell and the incubation time for cancer is any time from 2 to 90 years. And no cancer defines its origin.

We could be catching radioactive fish in Australia or the fish that are imported could contain radioactive isotopes, but unless they are consistently tested we will never know.

As well as the mountain water reaching the Pacific Ocean, since the accident, TEPCO has daily pumped over 300 tons of sea water into the damaged reactors to keep them cool. It becomes intensely radioactive and is pumped out again and stored in over 1,200 huge storage tanks scattered over the Daichi site. These tanks could not withstand a large earthquake and could rupture releasing their contents into the ocean.

But even if that does not happen, TEPCO is rapidly running out of storage space and is trying to convince the local fishermen that it would be okay to empty the tanks into the sea. The Bremsstrahlung radiation like x-rays given off by these tanks is quite high – measuring 10 milirems – presenting a danger to the workers. There are over 4,000 workers on site each day, many recruited by the Yakuza (the Japanese Mafia) and include men who are homeless, drug addicts and those who are mentally unstable.

There’s another problem. Because the molten cores are continuously generating hydrogen, which is explosive, TEPCO has been pumping nitrogen into the reactors to dilute the hydrogen dangers.

Vast areas of Japan are now contaminated, including some areas of Tokyo, which are so radioactive that roadside soil measuring 7,000 becquerels (bc) per kilo would qualify to be buried in a radioactive waste facility in the U.S..

As previously explained, these radioactive elements concentrate in the food chain. The Fukushima Prefecture has always been a food bowl for Japan and, although much of the rice, vegetables and fruit now grown here is radioactive, there is a big push to sell this food both in the Japanese market and overseas. Taiwan has banned the sale of Japanese food, but Australia and the U.S. have not.

Prime Minister Abe recently passed a law that any reporter who told the truth about the situation could be goaled for ten years. In addition, doctors who tell their patients their disease could be radiation related will not be paid, so there is an immense cover-up in Japan as well as the global media.

The Prefectural Oversite Committee for Fukushima Health is only looking at thyroid cancer among the population and by June 2016, 172 people who were under the age of 18 at the time of the accident have developed, or have suspected, thyroid cancer; the normal incidence in this population is 1 to 2 per million.

However, other cancers and leukemia that are caused by radiation are not being routinely documented, nor are congenital malformations, which were, and are, still rife among the exposed Chernobyl population.

Bottom line, these reactors will never be cleaned up nor decommissioned because such a task is not humanly possible. Hence, they will continue to pour water into the Pacific for the rest of time and threaten Japan and the northern hemisphere with massive releases of radiation should there be another large earthquake. ”

by Helen Caldicott, Global Research News, originally published in Independent Australia

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What to do with radioactive water from Fukushima — VOA Learning English

” Japanese officials are trying to decide what to do with thousands of tons of radioactive water from the damaged Fukushima nuclear power plant.

More than six years have passed since a powerful earthquake and tsunami severely damaged the power plant.

Some parts of cleanup efforts have gone well. People can now work in the area although they take special measures to avoid overexposure to radioactive substances.

The water remains a big problem however. Currently, the water is being stored in 900 large tanks near the nuclear center.

Conflicting opinions between two groups have kept Japanese officials from doing anything about the water.

Radiation experts advise the government to slowly release the water into the Pacific Ocean. They note that special treatment has removed the radioactivity from the water except for tritium, a radioactive form of hydrogen. The experts say tritium is safe in small amounts.

But local fishermen oppose the release of the water into the sea. They say people will not buy fish from waters near Fukushima if the water is released.

The fishermen lost their livelihoods for a long time after the disaster. Local fisheries are slowly recovering.

Fumio Haga fishes about 50 kilometers from the power plant. He said, “People would shun Fukushima fish again as soon the water is released.”

Fukushima disaster affected land and sea

The disaster was both deadly and had long-lasting environmental and economic effects.

An extremely powerful magnitude 9.0 earthquake struck off the coast of Japan on March 11, 2011. The quake caused deadly tsunami waves on the country’s northeastern coast. More than 18,000 people were killed.

The earthquake and waves caused the electricity to go out in many places including Fukushima. As a result, the cooling system failed in three of the six nuclear reactors which caused the nuclear fuel to overheat and partly melt structures in the power plant.

Radiation entered the air and contaminated water flowed into the sea.

That event hurt the livelihoods of people throughout the area. Although there are about 1,000 fishermen in the area today, only half still fish and they go out only two times a week because demand is low.

To be sold, the fish have to meet, what might be, the world’s most demanding requirements. Laboratory workers at Onahama test the fishermen’s catch, recording who caught the fish and where. And fish from the area is sold with official “safe” stickers.

Fifteen months after the disaster in 2012, only three kinds of fish could pass the safety inspection. Now the number has increased to over 100.

Yoshiharu Nemoto is a researcher at the Onahama test station. He said the fish may contain less than half of the radioactive cesium level permitted under Japan’s national standard and one-twelfth of the U.S. or European Union limit.

But consumers have not heard that message.

Over the years, fewer Japanese consumers avoid fish products from waters near Fukushima. But a study by Japan’s Consumer Agency in October found that 20 percent still do. The study found that consumers were more likely to pay attention to information about possible bad health results than to facts about radiation and safety standards.

Naoya Sekiya is an expert on social research and social psychology. He said the water from the nuclear power center should not be released until the public is well-informed about the facts.

“A release only based on scientific safety, without addressing the public’s concerns, cannot be tolerated in a democratic society,” he said. He said a release when the public is not prepared would only make things worse.

Kikuko Tatsumi is a representative of a consumer group and serves on a government expert panel with Sekiya. The group has been trying to decide what to do with the water for longer than one year.

Tatsumi said the delay in making a decision may be increasing concerns among the public. Many people believe the water is stored because it is dangerous and they think Fukushima fish are not available because they are not safe to eat.

Water from the center is a continuing problem

The Associated Press reports the amount of radioactive water at Fukushima is growing by 150 tons a day. This is because new water is used to cool the damaged reactors and ground water also enters the reactor area through cracks.

The water is a costly problem for the utility company Tokyo Electric Power Co, or TEPCO, which owns Fukushima. Last year, another group of government experts recommended that TEPCO should dilute the water by about 50 times and release it into the sea over time. The process could take 10 years to complete.

The new chairman at TEPCO, Takashi Kawamura, caused a strong reaction in the fishing community in April. He had expressed support for releasing the water.

But after strong opposition, the company withdrew the idea and said it had no plans for an immediate release and can continue storing water until 2020.

So, the problem continues, and the amount of radioactive water at Fukushima is growing.

I’m Mario Ritter. ”

 Mari Yamaguchi reported this story for AP. Mario Ritter adapted it with additional materials for VOA Learning English. Hai Do was the editor. 

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Japan still at a stalemate as Fukushima’s radioactive water grows by 150 tons a day — The Japan Times

” More than six years after a tsunami overwhelmed the Fukushima No. 1 nuclear power plant, Japan has yet to reach consensus on what to do with a million tons of radioactive water, stored on site in around 900 large and densely packed tanks that could spill should another major earthquake or tsunami strike.

The stalemate is rooted in a fundamental conflict between science and human nature.

Experts advising the government have urged a gradual release to the Pacific Ocean. Treatment has removed all the radioactive elements except tritium, which they say is safe in small amounts. Conversely, if the tanks break, their contents could slosh out in an uncontrolled way.

Local fishermen are balking. The water, no matter how clean, has a dirty image for consumers, they say. Despite repeated tests showing most types of fish caught off Fukushima are safe to eat, diners remain hesitant. The fishermen fear any release would sound the death knell for their nascent and still fragile recovery.

“People would shun Fukushima fish again as soon as the water is released,” said Fumio Haga, a drag-net fisherman from Iwaki, a city about 50 kilometers (30 miles) down the coast from the nuclear plant.

And so the tanks remain.

Fall is high season for saury and flounder, among Fukushima’s signature fish. It was once a busy time of year when coastal fishermen were out every morning.

Then came March 11, 2011. A magnitude 9 offshore earthquake triggered a tsunami that killed more than 18,000 people along the coast. The quake and massive flooding knocked out power for the cooling systems at the Fukushima nuclear plant. Three of the six reactors had partial meltdowns. Radiation spewed into the air, and highly contaminated water ran into the Pacific.

Today, only about half of the region’s 1,000 fishermen go out, and just twice a week because of reduced demand. They participate in a fish testing program.

Lab technicians mince fish samples at Onahama port in Iwaki, pack them in a cup for inspection and record details such as who caught the fish and where. Packaged fish sold at supermarkets carry official “safe” stickers.

Only three kinds of fish passed the test when the experiment began in mid-2012, 15 months after the tsunami. Over time, that number has increased to about 100.

The fish meet what is believed to be the world’s most stringent requirement: less than half the radioactive cesium level allowed under Japan’s national standard and one-twelfth of the U.S. or EU limit, said Yoshiharu Nemoto, a senior researcher at the Onahama testing station.

That message isn’t reaching consumers. A survey by the Consumer Affairs Agency in October found that nearly half of Japanese weren’t aware of the tests, and that consumers are more likely to focus on alarming information about possible health impacts in extreme cases, rather than facts about radiation and safety standards.

Fewer Japanese consumers shun fish and other foods from Fukushima than before, but 1 in 5 still do, according to the survey. The coastal catch of 2,000 tons last year was 8 percent of pre-disaster levels. The deep-sea catch was half of what it used to be, though scientists say there is no contamination risk that far out.

Naoya Sekiya, a University of Tokyo expert on disaster information and social psychology, said that the water from the nuclear plant shouldn’t be released until people are well-informed about the basic facts and psychologically ready.

“A release only based on scientific safety, without addressing the public’s concerns, cannot be tolerated in a democratic society,” he said. “A release when people are unprepared would only make things worse.”

He and consumer advocacy group representative Kikuko Tatsumi sit on a government expert panel that has been wrestling with the social impact of a release and what to do with the water for more than a year, with no sign of resolution.

Tatsumi said the stalemate may be further fueling public misconception: Many people believe the water is stored because it’s not safe to release, and they think Fukushima fish is not available because it’s not safe to eat.

The amount of radioactive water at Fukushima is still growing, by 150 tons a day.

The reactors are damaged beyond repair, but cooling water must be constantly pumped in to keep them from overheating. That water picks up radioactivity before leaking out of the damaged containment chambers and collecting in the basements.

There, the volume of contaminated water grows, because it mixes with groundwater that has seeped in through cracks in the reactor buildings. After treatment, 210 tons is reused as cooling water, and the remaining 150 tons is sent to tank storage. During heavy rains, the groundwater inflow increases significantly, adding to the volume.

The water is a costly headache for Tokyo Electric Power Company Holdings Inc., the utility that owns the plant. To reduce the flow, it has dug dozens of wells to pump out groundwater before it reaches the reactor buildings and built an underground “ice wall” of questionable effectiveness by partially freezing the ground around the reactors.

Another government panel recommended last year that the utility, known as Tepco, dilute the water up to about 50 times and release about 400 tons daily to the sea — a process that would take almost a decade to complete. Experts note that the release of tritiated water is allowed at other nuclear plants.

Tritiated water from the 1979 Three Mile Island accident in the United States was evaporated, but the amount was much smaller, and still required 10 years of preparation and three more years to complete.

A new chairman at Tepco, Takashi Kawamura, caused an uproar in the fishing community in April when he expressed support for moving ahead with the release of the water.

The company quickly backpedaled, and now says it has no plans for an immediate release and can keep storing water through 2020. Tepco says the decision should be made by the government, because the public doesn’t trust the utility.

“Our recovery effort up until now would immediately collapse to zero if the water is released,” Iwaki abalone farmer Yuichi Manome said.

Some experts have proposed moving the tanks to an intermediate storage area, or delaying the release until at least 2023, when half the tritium that was present at the time of the disaster will have disappeared naturally. ”

by Mari Yamaguchi, The Japan Times

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

by Martin Fackler, The New York Times

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