Japan pictures likely show melted Fukushima fuel for first time — Bloomberg

” New images show what is likely to be melted nuclear fuel hanging from inside one of Japan’s wrecked Fukushima reactors, a potential milestone in the cleanup of one of the worst atomic disasters in history.

Tokyo Electric Power Co. Holdings Inc., Japan’s biggest utility, released images on Friday showing a hardened black, grey and orange substance that dripped from the bottom of the No. 3 reactor pressure vessel at Fukushima, which is likely to contain melted fuel, according to Takahiro Kimoto, an official at the company. The company sent a Toshiba-designed robot, which can swim and resembles a submarine, to explore the inside of the reactor for the first time on July 19.

“Never before have we taken such clear pictures of what could be melted fuel,” Kimoto said at a press briefing that began at 9 p.m. Friday in Tokyo, noting that it would take time to analyze and confirm whether it is actually fuel. “We believe that the fuel melted and mixed with the metal directly underneath it. And it is highly likely that we have filmed that on Friday.”

If confirmed, the substance — which has the appearance of icicles — would be the first discovery of the fuel that melted during the triple reactor accident at Fukushima six years ago. For Tokyo Electric, which bears most of the clean-up costs, the discovery would help the utility design a way to remove the highly-radioactive material.

The robot, which is about 30 centimeters (12 inches) long, will search for melted fuel at the bottom of the reactor on Saturday. It is possible that the company will take more pictures of what could be melted fuel spread across the floor and lower levels, according to Tokyo Electric’s Kimoto. Fuel from a nuclear meltdown is known as corium, which is a mixture of the atomic fuel rods and other structural materials.

Early Signs

“It is important to know the exact locations and the physical, chemical, radiological forms of the corium to develop the necessary engineering defueling plans for the safe removal of the radioactive materials,” said Lake Barrett, a former official at the U.S. Nuclear Regulatory Commission who was involved with the cleanup at the Three Mile Island nuclear power plant in the U.S. “The recent investigation results are significant early signs of progress on the long road ahead.”

Because of the high radioactivity levels inside the reactor, only specially designed robots can probe the unit. And the unprecedented nature of the Fukushima disaster means that Tepco, as the utility is known, is pinning its efforts on technology not yet invented to get the melted fuel out of the reactors.

Removal Plans

The company aims to decide on the procedure to remove the melted fuel from each unit as soon as this summer. And it will confirm the procedure for the first reactor during the fiscal year ending March 2019, with fuel removal slated to begin in 2021.

Decommissioning the reactors will cost 8 trillion yen ($72 billion), according to an estimate in December from the Ministry of Economy, Trade and Industry. Removing the fuel is one of the most important steps in a cleanup that may take as long as 40 years.

Similar to the latest findings on Friday, Tepco took photographs in January of what appeared to be black residue covering a grate under the Fukushima Dai-Ichi No. 2 reactor, which was speculated to have been melted fuel. However, a follow-up survey by another Toshiba-designed robot in February failed to confirm the location of any melted fuel in the reactor after it got stuck in debris.

A robot designed by Hitachi-GE Nuclear Energy Ltd. also failed to find any melted fuel during its probe of the No. 1 reactor in March.

The significance of Friday’s finding “might be evidence that the robots used by Tepco can now deal with the higher radiation levels, at least for periods of time that allow them to search parts of the reactor that are more likely to contain fuel debris,” M.V. Ramana, professor at the Liu Institute for Global Issues at the University of British Columbia, said by email.

“If some of these fragments can be brought out of the reactor and studied, it would allow nuclear engineers and scientists to better model what happened during the accident.” ”

by Stephen Stapczynski, Bloomberg

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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. ”

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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. ”

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Updated 2/9/15: Robotic snake set to examine innards of melted Fukushima reactor — The Japan Times; New ‘transformer’ robot changes shape to access deadly Fukushima nuclear facilities — The Asahi Shimbun

Updated Feb. 9, 2015, The Japan Times: ” A snakelike robot designed to examine the interior of one of the three meltdown-hit reactors at the Fukushima No. 1 nuclear power plant is ready to begin its expedition.

Assessing the damage in the reactors is a crucial step in decommissioning the poorly protected plant, which was crippled by core meltdowns triggered by the Great East Japan Earthquake and tsunami in March 2011.

Remote-controlled robots are essential for the job because the radiation in the reactors chambers is so high it would kill any person who got close.

Using information gathered by the robot, Tokyo Electric Power Co., the plant operator, plans to repair the damaged chambers enough so they can be filled with water in preparation to remove the melted radioactive debris, an operation planned to begin in about a decade.

The 60-cm-long robot, developed by electronics giant Hitachi and its nuclear affiliate Hitachi-GE Nuclear Energy, was demonstrated this week at a Hitachi-GE facility northeast of Tokyo. It is expected to enter the No. 1 reactor as early as April, officials said.

It has a lamp at the front and is designed to crawl like a snake through a 10-cm-wide pipe into the containment vessel. From there it must dangle and descend onto a platform just below the reactor core’s bottom, an area known as the pedestal.

There, the robot is to transform into a U-shaped crawler and capture live images and temperature and radiation levels and transmit them to a control station outside the building.

Expectations for the robot probe are high after earlier efforts at assessment met with limited success.

“Depending on how much data we can collect from this area, I believe (the probe) will give us a clearer vision for future decommissioning,” Hitachi-GE engineer Yoshitomo Takahashi said.

After its exploratory trip, which will make the robot extremely radioactive, technicians plan to store it in a shielded box. They have no plans to reuse it.

Different robots must be designed for each reactor, since each is slightly different.

According to computer simulations, all of the fuel rods in unit 1 probably melted and pooled at the bottom of the containment chamber, but there had been no way of confirming that until now.

A brief fiberscope observation conducted in 2012 produced images that were scratchy and of limited use.

To assess the debris at the bottom of the damaged reactor chambers, which are usually filled with water, an amphibious robot is being developed for deployment next year.

The damage from the melted fuel burned holes in the reactors, thwarting efforts to fill them with cooling water. As a result, water must be pumped into them continuously, producing an endless stream of radiation-contaminated water that is hampering the plant’s cleanup process. ”

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Posted Feb. 6, 2015, The Asahi Shimbun: ” HITACHI, Ibaraki Prefecture–A new shape-changing robot has been rolled out that can chart previously inaccessible areas of the damaged containment vessels at the crippled Fukushima No. 1 nuclear power plant.

The new device was demonstrated Feb. 5 at a plant owned by Hitachi-GE Nuclear Energy Ltd., one of the firms involved in its development. The International Research Institute for Nuclear Decommissioning, an organization made up of electric power companies and nuclear power plant manufacturers, developed it with a government subsidy.

The probe was conceived as a way to examine the containment vessels, which are too radioactive for humans to enter. It is scheduled for deployment at the No. 1 reactor building, which contains melted fuel, this spring.

The tubular-shaped robot, measuring 60 centimeters long in its normal state, can transform itself depending on the space it is trying to enter and the task to perform.

In the demonstration at the factory, the robot, in its tubular form, made its way through a pipe with a diameter of 10 cm. On the other side of the pipe, it changed shape to crawl around and capture images of the area.

The plan is to have the probe access the containment vessels through the holes in the wall through which electrical power lines pass.

Because strong radiation is harmful to electronic machines as well, the robot’s camera is only guaranteed to function for 10 hours. The device can also take radiation and temperature readings. ”

source with short clip of the new robot