Updated 1/30/15, NHK World; Tepco to rely on cosmic beams to glimpse melted fuel inside Fukushima reactors — The Asahi Shimbun

Updated Jan. 30, 2015, NHK World:

Watch this video that explains how operators plan to use muon tomography imaging to figure out where the melted fuel at Fukushima Daiichi is, starting with Unit 1.

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Posted Jan. 25, 2015, The Asahi Shimbun: ” Tokyo Electric Power Co. will use cosmic rays at the crippled reactors at its Fukushima plant to identify sites with melted fuel.

TEPCO will install special equipment to observe muon beams, or particles generated when cosmic radial rays collide with the atmosphere. That will enable it to glimpse inside the reactors, which went into triple meltdown after the March 2011 earthquake and tsunami disaster.

The exercise is intended to generate data that will be useful in deciding how to eventually remove the fuel. Fuel extraction work will be the most difficult phase in decommissioning the beleaguered plant.

While the muons pass through concrete, iron and other construction materials, they become absorbed more easily in high-density materials such as uranium, thereby creating a “shadow.” Based on these shadows, TEPCO expects to be able to identify the location and shape of nuclear fuel.

The industry ministry-backed plan will be led by the International Research Institute for Nuclear Decommissioning, an organization comprising TEPCO and atomic facility manufacturers.

They will first study the No. 1 reactor building and compile results by the end of this fiscal year, estimating how much fuel remains in the reactor.

While some experts argue that almost all of the fuel has melted and dropped to the base of the containment vessel at the No. 1 reactor, others say half of it probably remains in the reactor core.

TEPCO and the central government intend to extract the melted fuel after surrounding it with water to block radiation. To do so, the plant operator will need to repair damaged sections of the containers to prevent water leaks.

An industry ministry official said the survey “will provide important data for deciding how much water to inject into the containers.”

However, as there are also limitations to the method, the study represents just the first step in ascertaining what is happening inside the stricken reactors.

For instance, nuclear fuel at the base of the container cannot be seen using the muon technique, because the particles are not coming from below the reactors. As the system’s resolution is 30 centimeters to 50 cm, small compounds of fuel will also be undetectable.

“Many unknown factors remain, such as what sort of obstacles are at play in the reactor buildings,” said Fumihiko Takasaki, professor emeritus at the High Energy Accelerator Research Organization, which was involved in the development of the observation equipment. “We cannot know whether the efforts will eventually prove successful unless we actually try.” ”



Updated 8/9/14: Fukushima reactor 3 meltdown was worse than estimated: Tepco — The Japan Times; Reactor No. 3 meltdown occurred 4 hours earlier — Yomiuri Shimbun; NHK World

Updated 8/9/14, The Japan Times: ” Tokyo Electric Power Co. said Wednesday that its new estimate shows that all the fuel rods in reactor 3 at the Fukushima No. 1 nuclear power plant apparently melted down and fell onto the bottom of the containment vessel.

In November 2011, the company had said it believed only about 63 percent of reactor 3′s fuel core had melted.

The utility updated its estimate as part of an effort to probe unclear points about the triple meltdown at the Fukushima No. 1 plant caused by a megaquake and monstrous tsunami in March 2011.

The revised estimate is based on the finding that an emergency cooling system, known as HPCI, of reactor 3 stopped working six hour earlier than previously thought, and that the meltdown had also started more than five hours earlier.

Tepco had previously said that the HPCI had shut down at 2:42 a.m. on March 13, 2011. But further investigation over the past year determined that the HPCI appeared to have lost its cooling function about at 8:00 p.m. on March 12.

According to the new estimate, all the melted fuel penetrated the pressure vessel, fell onto the bottom of the containment vessel and melted about 68 cm into the concrete.

The pressure vessel is located inside the massive containment vessel.

The analysis shows that the fuel did not penetrate the containment vessel, according Tepco.

While the new analysis announced on Wednesday, based on temperature, pressure and other data, shows that all the fuel had melted down to the containment vessel, Tepco has a more optimistic view.

“We think some fuel still remains at the core part based on the actual plant data,” said Shinichi Kawamura, a Tepco spokesman, during a news conference.

According to Kawamura, this is because the temperature of the pressure vessel decreased when the water was injected, meaning some warm fuel was still there. ”


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Originally posted 8/7/14, Yomiuri Shimbun: ” A 2011 meltdown inside one of the reactors at the Fukushima No. 1 nuclear plant may have started about four hours earlier than was previously believed, plant operator Tokyo Electric Power Co. said Wednesday.

In its latest findings, TEPCO also said that most of the nuclear fuel in the No. 3 reactor at the plant in Fukushima Prefecture melted through the pressure vessel and continued down to the bottom of the outer containment vessel. The finding may make it even more difficult to decommission the plant.

According to previous findings, including the final report made in July 2012 by the government’s Nuclear Incident Investigation and Verification Committee, TEPCO manually stopped an emergency high-pressure coolant injection apparatus at the No. 3 reactor and tried to switch to another water injection system as operation of the apparatus became unstable before 3 a.m. on March 13, 2011. The attempted switch failed, as TEPCO was unable to secure power source.

Initially, TEPCO had assumed that from that time on, a “hiatus of coolant injection” had started, leading to a fall in the water level inside the pressure vessel and triggering a core meltdown inside the vessel, sometime after 9 a.m. on the same day.

However, a record made by a worker at the plant that details water levels inside the reactor was found in the autumn of 2012. The record suggests it is possible that the coolant apparatus had already ceased functioning nearly seven hours before TEPCO stopped the coolant-injection device.

A new analysis of conditions inside the reactor, made on the basis of the uncovered record, led to the latest finding that the temperature in the reactor core reached the fuel’s melting point of 2,200 C at around 5:30 a.m. on that day.

TEPCO has come to assume that the core meltdown was highly likely to have started in the early morning of March 13.

As the core meltdown is now believed to have started earlier than was previously thought, the amount of melted nuclear fuel that passed into the containment vessel through the pressure vessel is considered to have been greater, making it technically more difficult to extract the melted fuel and dispose of it.

At 9:25 a.m on March 13, 2011, two days after major earthquakes and tsunami hit the area that includes Fukushima Prefecture, TEPCO began injecting water into the No. 3 reactor, with the use of a firefighting vehicle. Shortly after 11 a.m. on March 14, however, a hydrogen explosion occurred in the reactor-housing building, blowing away the upper part of the building. ”


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Read a related NHK World article, “Meltdown at Fukushima reactor 3 worse than thought,” HERE.

Fukushima residents feel torn as Japan prepares for their return to radiated zone near plant — Associated Press via Fox News; Yahoo!7 News videos [updated 5/1/14]

” TOMIOKA, Japan – Whenever Kazuhiro Onuki goes home, to his real home that is, the 66-year-old former librarian dons protective gear from head to toe and hangs a dosimeter around his neck.

Grass grows wild in the backyard. The ceiling leaks. Thieves have ransacked the shelves, leaving papers and clothing all over the floor so there is barely room to walk. Mouse dung is scattered like raisins. There is no running water or electricity.

Above all, radiation is everywhere.

It’s difficult to imagine ever living again in Tomioka, a ghost town about 10 kilometers (6 miles) from the former Fukushima Dai-chi nuclear plant. And yet more than three years after meltdowns at the plant forced this community of 16,000 people to flee, Onuki can’t quite make the psychological break to start anew.

His family lived here for four generations. Every time he goes back, he is overcome by emotion. Especially during that brief time in the spring when the cherry blossoms bloom.

“They flower as though nothing has happened,” he said. “They are weeping because all the people have left.”

The Japanese government is pushing ahead with efforts to decontaminate and reopen as much of a 20-kilometer (12-mile) no-go zone around the plant as it can. Authorities declared a tiny corner of the zone safe for living as of April 1, and hope to lift evacuation orders in more areas in the coming months and years.

Former residents have mixed feelings. In their hearts, many want their old lives back. But distrust about the decontamination program runs deep. Will it really be safe? Others among the more than 100,000 displaced have established new lives elsewhere, in the years since the 2011 earthquake and tsunami sent three of Fukushima’s reactors into meltdown.

If the evacuation order is lifted for their area, they will lose a monthly stipend of 100,000 yen ($1,000) they receive from Tokyo Electric Power Co., the owner of the Fukushima plant.

A survey last year found that 16 percent of Tomioka residents wanted to return, 40 percent had decided never to return, and 43 percent were undecided. Two-thirds said they were working before the disaster, but only one-third had jobs at the time of the survey, underlining the challenges to starting over.

Former resident Shigetoshi Suzuki, a friend of Onuki, is outraged the government would even ask such a question: Do you want to go back?

Of course, we all want to return, he said. People like him were effectively forced into retirement, the 65-year-old land surveyor said. If he hadn’t evacuated to a Tokyo suburb with his wife, he would have continued working for his longtime clients.

“It is a ridiculous question,” Suzuki said. “We could have led normal lives. What we have lost can’t be measured in money.”

In protest, he has refused to sign the forms that would allow his property to undergo decontamination.

The government has divided the no-go zone into three areas by radiation level.

The worst areas are marked in pink on official maps and classified as “difficult to return.” They are still enclosed by a barricade.

Yellow designates a “restricted” area, limiting visits to a few hours. No overnight stays are allowed.

The green zones are “in preparations to lift evacuation orders.” They must be decontaminated, which includes scrubbing building surfaces and scraping off the top layer of soil and is being carried out throughout the zones.

Tomioka has all three zones within its boundaries.

The green zones are those where authorities have confirmed radiation exposure can be brought below 20 millisieverts a year.

The long-term goal is to bring annual exposure down to 1 millisievert, or the equivalent of 10 chest X-rays, which was considered the safe level before the disaster, but the government is lifting evacuation orders at higher levels. It says it will monitor the health and exposure of people who move back to such areas.

In the yellow restricted zone, where Sukuki’s and Onuki’s homes lie, a visitor exceeds 1 millisievert in a matter of a few hours.

During a recent visit, Onuki and his wife Michiko walked beneath the pink petals floating from a tunnel of cherry trees, previously a local tourist attraction.

The streets were abandoned, except for a car passing through now and then. The neighborhood was eerily quiet except for the chirping of the nightingales.

“The prime minister says the accident is under control, but we feel the thing could explode the next minute,” said Michiko Onuki, who ran a ceramic and craft shop out of their Tomioka home. “We would have to live in fear of radiation. This town is dead.”

Both wore oversized white astronaut-like gear, which doesn’t keep out radioactive rays out but helps prevent radioactive material from being brought back, outside the no-go zone. Filtered masks covered half their faces. They discarded the gear when they left, so they wouldn’t bring any radiation back to their Tokyo apartment, which they share with an adult son and daughter.

Junji Oshida, 43, whose family ran an upscale restaurant in Tomioka that specialized in eel, was at first devastated that he lost the traditional sauce for the eel that had been passed down over generations.

He has since opened a new restaurant just outside the zone that caters to nuclear cleanup workers. He recreated the sauce and serves pork, which is cheaper than eel. He lives apart from his wife and sons, who are in a Tokyo suburb.

“There is no sense in looking back,” Oshida said, still wearing the eel restaurant’s emblem on his shirt.

Older residents can’t give up so easily, even those who will never be able to return — like Tomioka city assemblyman Seijun Ando, whose home lies in the most irradiated, pink zone.

Ando, 59, said that dividing Tomioka by radiation levels has pitted one group of residents against another, feeding resentment among some. One idea he has is to bring residents from various towns in the no-go zone together to start a new community in another, less radiated part of Fukushima — a place he described as “for our grandchildren and great-grandchildren.”

“I can survive anywhere, although I had a plan for my life that was destroyed from its very roots,” said Ando, tears welling up in his eyes. “Don’t get me wrong. I’m not suffering. I’m just worried for Tomioka.” ”

article source with photo essay

Updated 5/1/14: View this story via Yahoo!7 News with three excellent short videos that compare radiation levels in Fukushima, Tokyo and Denver; explain the latest water leak at Fukushima No. 1; and describe a community shift toward solar power in Japan.