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

Lost in translation: Fukushima readings are not new spikes, just the same “hot mess” that’s always been there — Beyond Nuclear

” The ongoing Fukushima nuclear catastrophe has been back in the news lately following record high readings at the reactor site. Radiation levels were estimated to be 530 sieverts per hour, the highest recorded since the triple core meltdown in March 2011.

But upon further examination, the story has been misreported, in part due to mistranslation. In fact, according to Nancy Foust of SimplyInfo.org, interviewed on Nuclear Hotseat, there was no spike. High readings were in expected locations that TEPCO was only able to access recently. Therefore, the reading became evident because workers were getting closer to the melted fuel in more dangerous parts of the facility. In other words, it’s not a new hot mess, just the same hot mess it’s always been, pretty much from the beginning. The good news is nothing has changed. The bad news is – nothing has changed.

The confusion was initially caused by a translation error that SimplyInfo.org thinks occurred between the Kyoto News and Japan Times. Since this happened, Foust and her group have been trying to get news sources to correct the stories, with limited success.

The elevated radiation levels are inside containment (good news) in ruined unit 2 and were discovered using a camera, not proper radiation monitors. Therefore, the high reading may not be reliable since it is an estimate based on interference data with the camera. (It has been reported that the 530 Sievert/hour figure could be 30% too low, or 30% too high. 530 Sieverts/hour equates with 53,000 Rems/hour, a dose rate that would deliver a fatal dose of radiation to a person a short distance away, with no radiation shielding, in a minute or less exposure time.) TEPCO is planning on sending in a robot properly equipped with radiation detectors to take a reliable reading. Although no date has been given, TEPCO indicates it expects to deploy the robot within 30 days or so.

Foust theorizes that the bulk of the melted irradiated nuclear fuel is probably right below the reactor vessel burned into the concrete below. No one knows if melted irradiated nuclear fuel has gone into the ground water below that. ”

by Beyond Nuclear

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Plans to remove nuclear fuel at Fukushima delayed again — Reuters via Channel NewsAsia

” A plan to remove spent nuclear fuel from Tokyo Electric Power Co Holdings Inc’s Fukushima Daiichi nuclear plant hit by the March 2011 tsunami has been postponed again due to delays in preparation, the Nikkei business daily reported on Thursday.

Work is now set to begin in fiscal 2018 at the earliest, the Nikkei said.

Removal of the spent fuel from the No. 3 reactor was originally scheduled in the first half of fiscal 2015, and later revised to fiscal 2017 due to high levels of radioactivity around the facilities, the Japanese business daily reported.

The timeline has been changed again as it was taking longer than expected to decontaminate buildings and clean up debris, the news agency reported.

The report comes a few months after the Japanese government said in October the cost of cleaning up the Fukushima plant may rise to several billion dollars a year, adding that it would look into a possible separation of the nuclear business from the utility. ”

Reporting by Krishna V Kurup in Bengaluru, editing by Shounak Dasgupta, REUTERS

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Small robot to probe Fukushima Daiichi — NHK World

Read the latest technical updates on the robot’s ability to probe Unit 2 for a estimated limit of 2 hours, down from its originally estimated 10-hour lifespan.

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” Engineers at Tokyo Electric Power Company decommissioning the Fukushima Daiichi nuclear plant are hoping a tiny camera will show them where melted fuel is located inside the crippled No. 2 reactor.

The camera is the latest bit of technology TEPCO engineers are pinning their hopes on. They want to insert it inside Fukushima Daiichi’s No.2 reactor containment vessel for the first time, and they can finally learn whether the fuel is inside, or whether it has penetrated through.

It’s a question they’ve been asking since 2011. Three of the plant’s reactors melted down that March, following a powerful earthquake and tsunami. High radiation levels have prevented anyone from going inside to find the molten fuel.

Experts believe it may have mixed with structures at the bottom of the containment vessels and formed “fuel debris” and on Tuesday, they hoped to catch a glimpse inside. But early on, they ran into trouble and had to reschedule.

Over the years, various remote-controlled robots have been sent inside the 3 reactors, but they haven’t gotten any clear pictures yet of fuel debris.

TEPCO plans to send in another robot to Reactor 2 next month. The utility hopes to be able to analyze results from this research, and create a plan for removing debris by summer.

But it will be a long road — they’ve estimated it will take as long as 4 decades to dismantle the plant, and this first step is the most difficult. ”

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Fukushima frozen wall status 2017; Unit 3 cover building installation — SimplyInfo.org

SimlyInfo.org shows a map of the current status of the frozen ice wall at Fukushima No. 1.

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Read SimplyInfo.org’s article on the current construction of a cover building for Fukushima Daiichi’s Unit 3, which will hopefully allow for robotic removal of spent fuel.

 

NRA puts stop to plan to reuse contaminated soil — SimplyInfo.org

” Japan’s Environment Ministry had a plan. They were going to solve the problem of the massive piles of radioactive soil but reusing it. One plan they described was using it as the base in roads. They didn’t provide much detail on how this would work or how it would not end up leaching contamination to the wider environment.

Japan’s nuclear regulator (NRA) is required to review any act by another agency that involves radiation exposures to the public. Now the NRA has requested a detailed plan before any review would begin. They want details about how this soil would be prevented from being used in residential areas or where children would be exposed.

This may have effectively put a stop to the Environment Ministry plan. Their goal appeared to be to declassify large amounts of contaminated soil and just make it go away however possible. NRA’s requirements may be too inconvenient to continue with that plan. ”

by Nancy Foust, SimplyInfo.org

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