Finding and removing melted fuel rods at Fukushima No. 1 — Nikkei Asian Review, The Japan Times

Nikkei Asian Review, “Survey fails to find melted rods at Fukushima reactors”:

” TOKYO — A remote survey of the Fukushima Daiichi nuclear plant’s No. 1 reactor was unable to locate and photograph melted nuclear fuel, Tokyo Electric Power Co. Holdings said Thursday, complicating efforts to remove that material as part of an extensive cleanup.

Tepco on Saturday sent a robot equipped with a camera into the containment vessel for the No. 1 unit. The majority of fuel rods have melted through the unit’s pressure vessel since the plant was struck by the March 11, 2011, earthquake and tsunami. The prevailing view has been that those melted fuel rods are now sitting under 2.5m of water at the bottom of the containment vessel.

The plan was to explore the bottom section by dipping a camera into the pool of water for the first time. But unexpected barriers such as pipes kept the camera around 1 meter from the bottom in most of the 10 positions surveyed instead of the intended depth of about 40cm from the bottom. While the camera was able to capture sand-like sediment, there was no trace of the melted fuel rods. Adding a fifth day to the investigation turned up no further evidence.

Yuichi Okamura, acting general manager of Tepco’s onsite nuclear power division, offered few comments at the utility’s Thursday news conference, saying only that “photographs and radiation data will need to be evaluated in conjunction with one another.”

The timeline set by Tepco and the government for decommissioning the Fukushima plant aims to begin extraction of melted-down material from the No. 1, No. 2 or No. 3 reactor in 2021 or earlier. An extraction plan is to be decided this summer. But the fact that the status of the melted rods still remains unknown underscores the seriousness of the accident.

The results of the robot survey were “limited,” according to Masanori Naitoh, director of nuclear safety analysis at the Institute of Applied Energy’s Nuclear Power Engineering Center. “It would be difficult to set a plan for extraction based on the information from this survey alone.”

An investigation of the No. 2 reactor also fell short, with the survey robot unable to reach the targeted spot right under the unit’s pressure vessel. ”

source

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The Japan Times, “Tepco’s biggest hurdle: How to remove melted fuel from crippled Fukushima reactors”:

” Six years after the triple meltdown at the Fukushima No. 1 nuclear power plant, recent investigations underneath the damaged reactor 2 using cameras and robots came close to identifying melted fuel rods for the first time.

Experts say getting a peek inside the containment vessel of reactor 2 was an accomplishment. But it also highlighted how tough it will be to further pinpoint the exact location of the melted fuel, let alone remove it some time in the future.

The biggest hurdle is the extremely lethal levels of radiation inside the containment vessel that not only prevent humans from getting near but have also crippled robots and other mechanical devices.

Safely removing the melted fuel would be a best-case scenario but the risks and costs should be weighed against the option of leaving the melted fuel in the crippled reactors, some experts said.

“The work to probe inside the containment vessels and remove the fuel debris will be extremely tough because of the high radiation levels,” said Hiroshi Miyano, who heads a panel of the Atomic Energy Society of Japan, which is discussing ways to decommission the Fukushima plant and making recommendations to the government.

The government and Tokyo Electric Power Company Holdings Inc. are trying to find a way to remedy the situation but existing methods and technologies may not be sufficient, Miyano said.

In search of melted fuel

The world’s attention turned to the melted fuel rods in late January when Tepco inserted a 10-meter-plus tube equipped with a camera into the containment vessel of reactor 2 to capture images under the pressure vessel that housed the fuel rods.

The images showed black lumps scattered beneath the pressure vessel.

When the March 11, 2011, Great East Japan Earthquake and monstrous tsunami hit, the plant suffered a blackout and lost its key cooling system, triggering meltdowns in reactors 1, 2 and 3. The melted nuclear fuel rods penetrated the pressure vessels and fell into the containment vessels.

Tepco had put cameras inside the containment vessels several times in the past six years but January’s probe was the first to apparently find melted fuel debris.

“We understand that this is a big milestone. We could finally get to see what it was like underneath the pressure vessel,” said Yuichi Okamura, general manager of Tepco’s nuclear power and plant siting division.

“This is critical information in order to remove the fuel debris.”

Radiation barrier

But Tepco hasn’t confirmed that the black lumps are melted fuel, saying they could be paint or cable wrappings, and further investigation is needed.

Capturing the images may be progress but the robot and camera forays have not provided enough information about how to deal with the melted fuel.

Last month, Tepco sent a remote-controlled, scorpion-shaped robot in to further probe inside the reactor 2 containment vessel. But the robot failed before it reached under the pressure vessel after a tire became stuck.

The robot’s dosimeter measured radiation levels of 210 sieverts per hour — enough to kill humans instantly.

While 210 sieverts per hour indicate the melted fuel was nearby, the radiation crippled the robot’s electronics, including its semiconductors and cameras, indicating that the further use of robots to pinpoint the melted fuel will be difficult, robotics experts said.

There are computer chips “designed to withstand a certain level of radiation, but the level inside the containment vessel is totally different,” said Satoshi Tadokoro, a professor at Tohoku University who is an expert on disasters and rescue robots.

The radiation can damage a robot’s chips that serve as their brains, causing the devices to lose control, said Tadokoro, whose robots have also been used at the Fukushima plant.

“On top of the high level of radiation, the entrance (to the containment vessel) for the robot is very small,” restricting what types of robots can be used to hunt for the melted fuel, he said.

Tepco said the opening it created on the side of the reactor 2 containment vessel is about 11 cm in diameter.

Fuel removal strategy

Tepco is set to conduct internal probes of the reactor 1 containment vessel this month and is preparing similar missions for reactor 3.

The government and utility then plan to adopt a basic fuel removal strategy this summer and fine-tune the plan next year, with the actual fuel removal taking place in or after 2021.

There are essentially three options for the strategy, according to the Tokyo-based International Research Institute for Nuclear Decommissioning (IRID), which is developing technologies for the Fukushima plant decommission.

One option is to flood the containment vessels with water and use a crane above the reactors to hoist up the melted fuel. The second option is to carry out the same process but without water. The third is to install removal equipment through the side of the containment vessel.

There are merits and drawbacks to each option, said Shoji Yamamoto, who heads the team developing technologies to create the fuel removal devices at IRID.

The flooding option can block radiation using water, but if the fuel melts into the water, it could pose a risk of recriticality. The debris may need to be cut into pieces for removal, but this process would enable water to get between multiple pieces, creating the condition for recriticality. For nuclear chain reactions to happen there needs to be a certain distance between nuclear fuel and water.

If there is no water, the recriticality risk is minimal but the massive radiation levels cannot be blocked, Yamamoto said.

Tepco’s Okamura said being able to block radiation with water is a huge plus, but noted the reactor 2 containment vessel had cracks and holes that could let injected coolant water escape.

With the Three Mile Island nuclear accident in the U.S., the flooding option was used to retrieve the melted fuel in the 1980s. But the key difference was that all of the melted fuel stayed inside the pressure vessel, so it was easier to flood the reactor.

Because the melted fuel in reactors 1, 2 and 3 at the Fukushima plant all penetrated the pressure vessels and fell into the containment vessels, extracting it from the top or the side was a tough call, Yamamoto said, noting it was important to know the exact location of the melted fuel.

The distance between the top of the pressure vessel and the bottom of the containment vessel is about 45 meters and some parts inside the pressure vessels will need to be removed if Tepco tries to remove the debris inside the containment vessels from the top.

“If we know that the melted fuel is concentrated in the containment vessels, it will be more efficient to remove it from the side” because the entry point is closer, Yamamoto said.

Whatever option is decided, Yamamoto stressed that maintaining the fuel removal device will be difficult because the radiation will probably cripple it.

“The fuel removal device will be controlled remotely … it will be broken somewhere down the line and the parts will have to be replaced, considering its (ability to withstand) radiation,” he said.

“Given that, maintenance will have to be done remotely, too, and that will be a big challenge.”

To remove or not

Another option altogether is for Tepco to leave the melted fuel where it is.

During a media tour of the Fukushima No. 1 plant last month, Okamura of Tepco said the utility intended to collect the melted fuel because leaving it was “not an appropriate way” to manage nuclear fuel.

Miyano of the Atomic Energy Society of Japan said the debris must be removed because radioactive materials, including nuclear fuel, must be strictly controlled under international rules requiring strict monitoring.

Domestic nuclear power plant operators have to report the amount of nuclear fuel they have to the Nuclear Regulation Authority, which then reports to the International Atomic Energy Agency.

“There is the question of whether the government and Tepco decide not to remove the fuel debris. That would be an international issue,” said Miyano, adding that a consensus from the international community would be needed.

At the same time, Miyano said debate and analysis will be required to decide which choice would be best by looking at various factors, including how much it will cost to pick up all the melted fuel and where to store it. ”

by Kazuaki Nagata

source

Bulk of melted fuel in No. 2 reactor at damaged Fukushima plant at bottom of pressure vessel: Tepco — The Japan Times

” Most of the melted nuclear fuel inside the No. 2 reactor at the disaster-hit Fukushima No. 1 power plant is likely located at the bottom of its pressure vessel, Tokyo Electric Power Company Holdings Inc. has revealed.

According to a study that used a cosmic ray imaging system, an estimated 130 tons of the so-called fuel debris remains at the bottom of the vessel, the first time the location and amount of the melted fuel have been estimated.

The finding, announced on Thursday, is important as the data could help the operator to narrow down methods to remove the fuel debris, the most challenging task in decommissioning the plant’s Nos. 1 to 3 reactors that experienced meltdowns in the nuclear crisis that began in March 2011.

Tepco plans to decide how to start removing the debris in two years, with work to start in 2021.

The cosmic-ray study was carried out by a team involving Tokyo Electric and the High Energy Accelerator Research Organization in Ibaraki Prefecture.

As high radiation levels are continuing to hamper direct access to the reactors, researchers have tracked muon elementary particles, which are produced as cosmic rays collide with atmospheric particles and change course when coming into contact with nuclear fuel.

The No. 2 reactor was in operation when the nuclear crisis was triggered by a powerful earthquake and subsequent tsunami that devastated Japan’s northeast.

About 160 tons of fuel assemblies are estimated to have been present inside the reactor vessel prior to the crisis. Most of the fuel is believed to have fallen to the bottom of the pressure vessel and mixed with nearby structures to form the debris.

In the nuclear crisis, massive amounts of radioactive substances were released into the environment, with the Nos. 1, 3 and 4 reactor buildings damaged by hydrogen explosions.

The No. 4 reactor was offline for routine maintenance work and all of its fuel was stored in the spent fuel pool, avoiding a meltdown. The utility removed all fuel rod assemblies from the pool and transported them to a more stable building in 2014.

Also on Thursday, Tepco said it plans to seek additional financial support from the government to cover soaring costs for dealing with the disaster.

Tepco specifically asked the government to clarify its views on how the costs for providing compensation to affected residents and the decommissioning of the plant should be shouldered.

Each request for additional aid will be carefully scrutinized by the government out of concern it could come under fire from taxpayers, sources said.

The government has already agreed to provide up to ¥9 trillion in loans to Tepco to cover ¥5.4 trillion in compensation to be paid to affected residents and ¥2.5 trillion in decontamination costs that were projected in January 2014.

But Tepco said compensation payments have already topped ¥6 trillion and that decontamination costs are increasingly likely to exceed estimates.

The utility also said it is concerned about massive costs to be incurred when it starts full-fledged decommissioning work at the damaged nuclear plant.

If the situation is left unaddressed, Tepco’s market value will suffer, Executive Officer Keita Nishiyama said.

Tepco President Naomi Hirose said that although overall compensation costs have not been fixed, his company will consult with the government on how those costs will be funded. ”

by Kyodo, Jiji

source

Tepco admits molten nuclear fuel is transferred in multiple places of Reactor 2 — Fukushima Diary

” Tepco admitted the molten fuel is transferred to multiple places in Reactor 2 by 6/30/2016.

Tepco had been implementing the muon scanning investigation with KEK (High Energy Accelerator Research Organization).

Tepco describes the research result as it is highly likely that major part of the molten nuclear fuel remains in the bottom of the reactor with structures of the inside of the reactor. They also detected a part of the molten fuel on the wall of the reactor. This means the molten fuel was separated and remaining in different locations. Tepco did not mention the percentage of the detected fuel.

Tepco did not identify the location either so it is not clear if the fuel remains inside of the Reactor Pressure Vessel or its outer structure, Primary Containment Vessel. ”

by Iori Mochizuki

source with French translation

Updated 7/7/2015: ‘Scorpion’ robot hopes to succeed where the snake-bots failed — News.com.au; New ‘scorpion’ robot will inspect Fukushima reactor this summer — Paleofuture

July 7, 2015, News.com.au:

” A NEW robot that raises its tail like a scorpion is scheduled to look at melted nuclear fuel inside one of the three wrecked Fukushima reactors in Japan.

Toshiba Corp., co-developer of the “scorpion” crawler that was demonstrated today, said the robot will venture into the Unit 2 reactor’s primary containment vessel in August after a month of training for its handlers.

But even metal and silicon cannot hold up to the intensity of radiation within a nuclear reactor for long.

The robot has enough radiation tolerance to allowing it to stay about 10 hours inside the Unit 2 reactor.

Toshiba officials say they hope the robot can capture images of deeper areas of the vessel, though the primary focus is the platform area, so they can design a more suitable robot that can go deeper into the vessel.

Insider View

Officials hope the robot can see the fuel in the pressure vessel in the middle of the reactor. The position of the toppled fuel rods hasn’t been located exactly and studied because of the high radiation levels.

The scorpion robot is the second to enter a primary containment vessel, after “snake” robots were sent in April inside the worst-hit Unit 1. One of the two robots used in that reactor became stuck and had to be left behind, and neither was able to spot the melted fuel debris.

This time, the scorpion crawler, which is 54 centimetres long when extended, will enter through a duct designed as a passageway for fuel rods. Toshiba has no back up machine.

The robot’s entry is just the beginning of the reactor investigation required before the most challenging task of removing the melted fuel.

The difficult work of decommissioning the Fukushima plant damaged by the 2011 earthquake and tsunami will take decades.

High Hopes

During the demonstration at a Toshiba lab near Tokyo, the robot slid down a railing as it stretched out like a bar, with a head-mounted LED showing its way. After crawling over a slight gap and landing on a metal platform, the robot lifted its tail, as if looking up at the bottom of the control rod drive, a structure above the platform where some melted nuclear fuel might be left.

The scorpion also demonstrated it can roll back upright if it hits an obstacle and rolls over. The ability comes from a tail joint in the middle that bends.

One operator controls the robot with a joystick, and another monitors a video feed from the robot and other data. At the Fukushima plant, the robot will be operated remotely from a command centre in a separate building.

The work is planned for a full day. ”

source with video and photos

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Posted July 2, 2015, Paleofuture:

” When the 2011 earthquake in Japan damaged the Fukushima nuclear power plant, teams scrambled to find a robot that could go where humans couldn’t. In many ways those robots failed, and ever since, there has been a focus on creating robots that can get the job done. Enter Toshiba’s “Scorpion” robot, which will make its way inside the power plant this August.

The Scorpion is just 21 inches long and is operated by remote control. The robot has cameras on both front and back, as well as LED lights to help light the way. What is Scorpion looking for? Fuel amongst the debris, which will give teams a better sense of how the decades-long clean-up at the reactors should proceed.

Back in April, teams sent a snake-like robot inside one of the nuclear reactors but didn’t find what they were looking for. That robot stopped working after just three hours in one of the reactors. A second snake-bot was sent in a few days later but that one stopped working in short order as well.

The Scorpion is said to be specially designed to operate in the highly radioactive environment. Teams expect the robot to be able to function for 10 hours inside the plant. But we’ll have to wait and see.

The main focus of last month’s DARPA Robotics Challenge was to develop robots for emergency scenarios. And that competition, along with the relatively primitive capabilities of a robot like Scorpion show that we have quite a long ways to go before robots are performing the human-like tasks that we’d like them to in disaster scenarios. ”

source with photos

Also read about the DARPA Robotics Challenge in this Japan Times article, “Robots compete in Fukushia-inspired U.S. challenge

Updated 4/13/15: Survey robot breaks down inside Fukushima No. 1 reactor in under three hours — The Japan Times

Updated April 13, 2015, The Japan Times: ” A remote-controlled robot inserted to survey the inside of the No. 1 reactor at the damaged Fukushima No. 1 nuclear power plant has stopped functioning, Tokyo Electric Power Co. said.

As a first step in the utility’s effort to remove melted nuclear fuel from the bottom of the unit’s primary containment vessel, the shape-shifting robot was sent in Friday morning to find the exact location of the highly radioactive debris.

Set to cover some 20 meters of the first floor on the first day, the robot began its trip at around 11:20 a.m. but halted at around 2:10 p.m. after completing two-thirds of the route, Tepco said.

The utility said footage from the robot’s camera shows it passed an opening leading to the vessel’s basement, where the molten fuel is believed to have ended up after the core meltdowns occurred after the March 2011 quake and tsunami. ”

source

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Posted April 10, 2015, The Japan Times, “Robot enters primary containment vessel of reactor 1 in Fukushima”:

” A robot on Friday crept into the deadly primary containment vessel of reactor 1 of the Fukushima No. 1 power plant to surveil its damaged interior, Tokyo Electric Power Co. said.

It is the first time a robot has entered the PCV of any of the three stricken reactors at the meltdown-hit plant, and the snake-like contraption might give the utility a better idea of what happened to the pressure vessel and its core in the disaster.

Tepco plans to have the robot check half of the first floor of the bulbous PCV on Friday and examine the other half on Monday.

Ultimately, the utility plans to explore the underground portion of the vessel, where the melted fuel rods are believed to have puddled. But that is not yet feasible because the robot isn’t waterproof. A waterproof version is expected to be developed by the end of next March.

The snake-like robot, about 9.5 cm high and 60 cm long, entered the vessel through a pipe 10 cm in diameter. After going down to the first floor, it was to assume a U shape and measure temperature and radiation levels. It was also to photograph the interior and check for obstacles in the area leading to the underground portion.

When a measuring device was snaked into the same vessel in October 2012, the radiation peaked at a deadly 11 sieverts per hour.

The fuel in reactor Nos. 1 to 3 is believed to have melted through their reactor pressure vessels and spread to the primary or other containment vessels. But the exact details are still a mystery more than four years after the crisis began because the site is too hostile to explore.

Developed by Hitachi-GE Nuclear Energy Ltd. and the International Research Institute for Nuclear Decommissioning, the robot is equipped with a camera, a thermometer and dosimeter.

Given the high radiation, it can only function for about 10 hours before the electronics fail, the institute said.

The robot will be remotely guided from a plant building where radiation is lower. About 40 workers will be involved and radiation exposure will be limited to 2.5 millisieverts or lower per person per day. ”

source

Updated 10/1/14: Continuing to piece together March 2011 — The Japan Times

The Japan Times continues to piece together the March 2011 nuclear catastrophe based on recently released transcripts, including the accounts of Tepco management and workers at the Fukushima site during the early stages of the disaster. For more articles based on the transcripts, view an earlier blog post HERE.

Updated Oct. 1, 2014:

1) As radiation levels soared at Fukushima No. 1, plant chief Yoshida rescinded evacuation order

2) Tears, hopeful promises of reunion as Tepco workers evacuated Fukushima No. 1

3) Four days later: ‘Fukushima 50′ recount start of nuclear crisis

Posted Sept. 26, 2014:

Helplessness as reactor 2 lost cooling

source

” While reactors 1 and 3 at the Fukushima No. 1 nuclear complex suffered core meltdowns, the cooling system for reactor 2 continued to work for three days despite the loss of power following the earthquake and tsunami of March 11, 2011.

The fact that the reactor 2 core isolation cooling system lasted much longer than expected was a “blessed relief,” Fukushima No. 1 chief Masao Yoshida would later say. If it hadn’t been for that, all three units could have spun out of control simultaneously.

Reactor 2′s cooling system finally stopped functioning at 1:25 p.m. on March 14. With no electricity to reactivate it, workers had to depressurize the reactor pressure vessel housing the nuclear fuel so that firetrucks could pump in seawater.

Using car batteries to manipulate valves and release steam from the vessel, the depressurization process finally started at 6:02 p.m. About 20 minutes later, however, the central control room for reactors 1 and 2 reported that the water level had drained to 3.7 meters below the top of the nuclear fuel in reactor 2, leaving it fully exposed. There was also no sign the seawater was entering the reactor.

Just then, a member of Tokyo Electric Power Co.’s firefighting unit returned to the emergency response office and said the firetrucks that were supposed to be injecting water into the reactor had run out of fuel. Yoshida, 56, had already issued instructions that the trucks be kept refueled on a continuous basis.

“Didn’t I tell you?” Yoshida asked, looking up helplessly from his desk at the center of the emergency response office.

Yoshida would later recall that this felt like a “turning point,” beyond which “we had run out of all options and I thought I might really die.”

With no time to lose, the firefighting team immediately rushed back to the firetrucks, having to carry the fuel containers themselves because the tanker had a flat tire after driving over rubble scattered by the hydrogen explosion that had ripped through the reactor 3 building earlier that day.

In the emergency response office, Toshiko Kogusuri, 55, of Tepco’s management team, had been secretly ordered by the head of the team to secure as many buses at the plant as possible. Kogusuri felt Yoshida was starting to consider an evacuation. She asked officials of partner companies in the office building to lend their buses, saying she needed them for on-site transportation of workers.

That was a lie, but the companies did not ask questions and agreed to cooperate.

Just before 8 p.m., about 700 Tepco employees and 150 other workers from other companies, including plant manufacturers and Tepco-affiliated firms, were inside the building. More than 90 minutes had passed since the firetrucks had stopped injecting water into the reactor.

Yoshida felt he should no longer keep contract workers, who had worked day and night from the beginning of the crisis on March 11, on-site.

Many workers were sitting in a corridor on the second floor and on the stairs of the office building. Yoshida went up to them and said: “Thank you for dealing with the situation until now. It is OK to go home. Please evacuate carefully as roads on the way may have caved in.”

He spoke in such a calm tone that the workers did not realize the gravity of the situation.

The contract workers all departed, some in their cars, by roughly 8:30 p.m., leaving only Tepco employees at the plant. By that time, Kogusuri had managed to secure six buses. Yoshida then asked the head of Tepco’s management team whether there was any place people could evacuate to.

Tepco’s local thermal power station and the Fukushima No. 2 nuclear plant were nominated. The team head told Yoshida that the No. 2 plant was ready, having prepared a facility for the injured and a gymnasium to house the others.

At about 8 p.m., the injection of seawater into reactor 2 started after the firetrucks had been refueled, to the relief of the emergency response office. Even so, the situation remained tense because radioactive steam still had to be vented from the reactor to prevent the containment vessel from rupturing, which would expose the nuclear fuel to the external environment.

With workers unable to operate the venting valves, the pressure continued to build, to the point that the water injection had to be halted again.

Shiro Hikita, at 56 an experienced leader of one of the equipment restoration teams, felt that the reactor’s containment vessel could break at any time. “If there was a switch somewhere to end this situation, I would go out there to push it. I wouldn’t even mind dying in order to do it,” he thought to himself.

Early on March 15, silence engulfed the emergency response office as the point of no return neared. Yoshida stood up and started staggering around, mumbling to himself, “It’s all over.”

As he returned to his seat, he leaned back in his chair, crossed his arms and closed his eyes.

He was later quoted by aides as saying that he was thinking about what might happen if the reactor 2 containment vessel failed, discharging a catastrophic amount of radioactive materials: Tepco would have to abandon any pretense of controlling the situation inside the No. 1 plant and might even have to abandon the No. 2 facility. People from Fukushima to Tokyo, about 220 km away, might have to evacuate.

He could not think of a way to avoid such a scenario.

Hikita, the equipment team leader, saw Yoshida’s body slide from the chair onto the floor. At first he thought Yoshida had collapsed but then realized he was sitting cross-legged as if meditating. With his eyes closed, Yoshida did not move for several minutes.

Yoshida later said he was calling to mind the faces of his longest-serving colleagues: “There were about 10 or so. I thought those guys might be willing to die with me.”

At that point, the building housing the emergency response office was still the safest place at the plant, but there was the risk of contamination if the reactor 2 containment vessel ruptured.

Yoshida was searching for the right time to allow Tepco employees to leave the plant, except for a skeleton crew to keep watch over the reactors’ condition and to continue the water injection process. But even if all of his crew stayed on-site, there was only so much they could do, Yoshida thought to himself. ”

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Tepco plea to evacuate enraged Kan

source

” FUKUSHIMA — A senior Tokyo Electric Power Co. official broke down and wept in the prime minister’s office when the utility felt it had exhausted all options to prevent an utter catastrophe at the Fukushima No. 1 plant.

“I’m sorry. We’ve tried many things, but we are in a situation beyond our control,” Susumu Kawamata, 54, head of Tepco’s Nuclear Quality and Safety Management Department, told Minister of Economy, Trade and Industry Banri Kaieda in March 2011 before bursting into tears.

A member of the government’s nuclear safety panel who witnessed the scene thought it spelled the end for one of Japan’s biggest companies.

Shortly after 4 a.m. on March 15, Prime Minister Naoto Kan was sitting face to face with Tepco President Masataka Shimizu, telling him that withdrawing workers from the No. 1 plant was not an option. By that stage, the ravaged complex had experienced hydrogen explosions in the buildings housing reactors 1 and 3 and was facing a potential rupture of the reactor 2 containment vessel.

About 8½ hours prior to that meeting, Tepco’s top-level officials had started to consider evacuating employees from the plant. At around 7:30 p.m. on March 14, Tepco Managing Director Akio Komori, who was at an emergency response center set up 5 km from the plant, suggested the idea during a teleconference with officials at the utility’s Tokyo head office.

“If we don’t make a decision at some point, things could get crazy. Please start setting the criteria for evacuation,” Komori, 58, requested.

Tepco Executive Vice President Sakae Muto, 60, ordered his subordinates at the head office to craft an evacuation plan, while Fukushima No. 1 chief Masao Yoshida started to secure enough buses. Procedures to send employees to Tepco’s Fukushima No. 2 nuclear plant were also being decided.

Shimizu, Tepco’s 66-year-old president, phoned Kaieda, who had been placed in charge of dealing with the unfolding disaster, and Chief Cabinet Secretary Yukio Edano, 46, repeatedly to seek approval for the “evacuation” of workers.

But Shimizu did not communicate clearly that Tepco would maintain a minimum core of employees to monitor the situation and continue to oversee water injection into the three reactors that had suffered core meltdowns.

Kaieda, 62, said he thought Tepco was seeking approval for a “complete withdrawal” from the plant and turned down Shimizu’s request. But at 3 a.m. on March 15, as the condition of reactor 2 worsened, Kaieda decided to ask Kan, 64, to make a decision. He woke up Kan and briefed him on the situation.

“If people withdraw, the eastern part of Japan will be destroyed,” Kan replied, and immediately summoned Shimizu to his office. As soon as Shimizu set foot inside the reception room, Kan lashed into him, saying, “I heard that you are thinking about a withdrawal, but that’s impossible.”

The Tepco president’s response — “we do not have in mind such a thing as withdrawal” — was stunning to Haruki Madarame, 62, the head of the government’s nuclear safety panel who was present for the talks. Madarame later recalled wondering, “What happened to all those talks” about getting the Tepco workers out?

While officials in the prime minister’s office had misunderstood Tepco’s intentions, Shimizu was also at fault for a lack of clarity in his statements.

Kan then told Shimizu he would launch a joint accident response task force. Based in Tepco’s head office, the unprecedented task force saw the government and Tepco jointly deal with the escalating crisis.

Kan announced he was leaving for Tepco’s head office right away, but Shimizu pleaded for two hours to make the necessary preparations. Kan turned and ordered Shimizu to have everything ready within an hour.

The prime minister was still in a white-hot rage when he arrived at Tepco headquarters, unable to hide his distrust and fury toward the company.

“Tepco will go 100 percent bust if it withdraws. You won’t be able to escape even if you try!” he screamed at Tepco Chairman Tsunehisa Katsumata, 70, Shimizu and other senior executives before 200 other Tepco employees present. “It doesn’t matter if senior (Tepco) officials in their 60s go to the site and die! I will also go. President, chairman — make up your minds!”

Kan’s diatribe, which continued more than 10 minutes, was relayed live to employees in the emergency response office at the Fukushima No. 1 plant via a teleconference system.

Kan later said he was totally unaware that he had been “yelling at everyone,” explaining, “I might have used strong words to tell them to somehow hang on until the last minute, but I didn’t mean to scold them.”

Kan was one of many senior politicians who, up until that point, were unaware Tepco had set up a teleconference system connecting its head office with Fukushima No. 1.

“I was really surprised,” said Kan, who had learned of the March 12 hydrogen explosion in the reactor 1 building from the TV news rather than Tepco. “There was this huge screen connected to the No. 1 plant. I wondered why information was coming so slowly to the prime minister’s office given the existence of this system.”

Although the joint task force was meant to improve communications, Kan soon realized it was too late to rein in the crisis.

Up at Fukushima No. 1, Takeyuki Inagaki, 47, head of one of the plant’s equipment restoration teams, was among the hundreds of employees in the emergency response office who witnessed Kan’s tirade via the teleconference system. “Even though we were doing our best, we felt like we had been shot in the back with a machine gun,” he later recalled.

Yoshida, 56, the plant chief, was about to answer a call from the Tokyo office when a chilling sound swept through the response office at 6:14 a.m, albeit duller than that of the two previous hydrogens blasts.

Those present felt their blood freeze as they were told by reactor operators that the pressure inside the reactor 2 suppression chamber, connected to the containment vessel, had dropped to zero.

If the chamber did not remain airtight, radioactive steam could pour out into the external environment, leaving no safe place inside the plant or in the surrounding area.

“The suppression chamber might have a gapping hole. A hell of a lot of radioactive substances could come out,” Inagaki informed Yoshida, who instantly decided it was time to evacuate the site. “