Japanese robot probes the radioactive water at Fukushima’s nuclear reactor to find melted fuel — Daily Mail

” A Japanese robot has begun probing the radioactive water at Fukushima’s nuclear reactor.

The marine robot, nicknamed the ‘little sunfish’, is on a mission to study structural damage and find fuel inside the three reactors of the devastated plant.

Experts said remote-controlled bots are key to finding fuel at the dangerous site, which has likely melted and been submerged by highly radioactive water.

The probe – about the size of a loaf of bread – is equipped with lights, manoeuvres using tail propellers and collects data using two cameras and a dosimeter radiation detector.

Plant operators chose to send the robot inside the containment vessel of the No. 3 reactor because it has highest known water levels out of the the three reactors.

The robot entered the structure at 6.30am JST (10.30 BST, 5.30 ET) through a pipe connected to the containment vessel.

The marine machine, which was attached to cables, then swam to the area just below the reactor pressure vessel inside to take images.

New images taken by the robot show how parts of the system, including the control rod, have been damaged by radiation.

On Friday, the robot will continue its travels to the bottom of the containment vessels, where melted fuel deposits are believed to have accumulated.

In 2011, a 10-metre-high tsunami that killed nearly 19,000 people crashed into Japan’s Fukushima nuclear power plant, leading to several meltdowns.

Five years after the disaster, researchers are still struggling to clean up the highly dangerous radioactive materials in water of the wasting reactors.

It’s estimated that plant officials have only located 10 per cent of the waste fuel left behind after the nuclear meltdowns.

And the damaged plant is believed to be leaking small amounts of the radioactive waste into the Pacific Ocean, which could be travelling as far as the west cost of the US.

Researchers are now pinning their hopes on the remote-controlled sunfish robot to locate the lost fuel in order to work out the safest way to remove it.

During a demonstration of the device at a test facility near Tokyo last month, the probe slowly slid down from a rail and moved across the water.

A team operated it remotely, with one guiding the robot while another adjusted a cable that transmits data and serves as its lifeline.

Japan hopes to locate and start removing fuel from the reactors after Tokyo’s 2020 Olympics.

In earlier operations, snake and scorpion-shaped robots became stuck inside two reactors.

The scorpion robot’s crawling function failed and it was left inside the plant’s Unit 2 containment vessel.

The other, designed for cleaning debris for the ‘scorpion’ probe, was called back after two hours when two of its cameras stopped working after its total radiation exposure reached 1,000 Sievert – a level that would kill a human within seconds.

The plan had been to use the robot for 10 hours at an exposure level of 100 Sievert per hour.

The swimming robot shown was co-developed by electronics and energy giant Toshiba and the government’s International Research Institute for Nuclear Decommissioning. “

by Daisy Dunne, Mail Online and Associated Press

source with photos and video

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Cleaner robot pulled from Fukushima reactor due to radiation — Beloit Daily News

” TOKYO (AP) — A remote-controlled cleaning robot sent into a damaged reactor at Japan’s Fukushima nuclear plant had to be removed Thursday before it completed its work because of camera problems most likely caused by high radiation levels.

It was the first time a robot has entered the chamber inside the Unit 2 reactor since a March 2011 earthquake and tsunami critically damaged the Fukushima Da-ichi nuclear plant.

Tokyo Electric Power Co. said it was trying to inspect and clean a passage before another robot does a fuller examination to assess damage to the structure and its fuel. The second robot, known as the “scorpion,” will also measure radiation and temperatures.

Thursday’s problem underscores the challenges in decommissioning the wrecked nuclear plant. Inadequate cleaning, high radiation and structural damage could limit subsequent probes, and may require more radiation-resistant cameras and other equipment, TEPCO spokesman Takahiro Kimoto said.

“We will further study (Thursday’s) outcome before deciding on the deployment of the scorpion,” he said.

TEPCO needs to know the melted fuel’s exact location and condition and other structural damage in each of the three wrecked reactors to figure out the best and safest ways to remove the fuel. It is part of the decommissioning work, which is expected to take decades.

During Thursday’s cleaning mission, the robot went only part way into a space under the core that TEPCO wants to inspect closely. It crawled down the passage while peeling debris with a scraper and using water spray to blow some debris away. The dark brown deposits grew thicker and harder to remove as the robot went further.

After about two hours, the two cameras on the robot suddenly developed a lot of noise and their images quickly darkened — a sign of a problem caused by high radiation. Operators of the robot pulled it out of the chamber before completely losing control of it.

The outcome means the second robot will encounter more obstacles and have less time than expected for examination on its mission, currently planned for later this month, though Thursday’s results may cause a delay.

Both of the robots are designed to withstand up to 1,000 Sieverts of radiation. The cleaner’s two-hour endurance roughly matches an estimated radiation of 650 Sieverts per hour based on noise analysis of the images transmitted by the robot-mounted cameras. That’s less than one-tenth of the radiation levels inside a running reactor, but still would kill a person almost instantly.

Kimoto said the noise-based radiation analysis of the Unit 2’s condition showed a spike in radioactivity along a connecting bridge used to slide control rods in and out, a sign of a nearby source of high radioactivity, while levels were much lower in areas underneath the core, the opposite of what would normally be the case. He said the results are puzzling and require further analysis.

TEPCO officials said that despite the dangerously high figures, radiation is not leaking outside of the reactor.

Images recently captured from inside the chamber showed damage and structures coated with molten material, possibly mixed with melted nuclear fuel, and part of a disc platform hanging below the core that had been melted through. ”

by Mari Yamaguchi

source with photos