6 Years after Fukushima disaster, robots continue search for radioactive fuel — Bloomberg, Insurance Journal; The Japan Times

” The latest robot seeking to find the 600 tons of nuclear fuel and debris that melted down six years ago in Japan’s wrecked Fukushima Dai-Ichi power plant met its end in less than a day.

The scorpion-shaped machine, built by Toshiba Corp., entered the No. 2 reactor core [on Thursday, Feb. 16] and stopped 3 meters (9.8 feet) short of a grate that would have provided a view of where fuel residue is suspected to have gathered. Two previous robots aborted similar missions after one got stuck in a gap and another was abandoned after finding no fuel in six days.

After spending most of the time since the 2011 disaster containing radiation and limiting ground water contamination, scientists still don’t have all the information they need for a cleanup that the Japanese government estimates will take four decades and cost 8 trillion yen ($70.6 billion). It’s not yet known if the fuel melted into or through the containment vessel’s concrete floor, and determining the fuel’s radioactivity and location is crucial to inventing the technology needed to remove it.

“The roadmap for removing the fuel is going to be long, 2020 and beyond,” Jacopo Buongiorno, a professor of nuclear science and engineering at the Massachusetts Institute of Technology, said in an e-mail. “The re-solidified fuel is likely stuck to the vessel wall and vessel internal structures. So the debris have to be cut, scooped, put into a sealed and shielded container and then extracted from the containment vessel. All done by robots.” … ”

Continue reading about the fuel-removal status of Fukushima No. 1’s Units 1 through 3.

by Emi Urabe and Stephen Stapczynski, Bloomerg via Insurance Journal

source

* * *

Read a similar article by The Japan Times

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

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.

* * *

” 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. ”

source

New robot to map Fukushima reactors — BBC News

” A new robot designed to help decommission reactors at the Fukushima nuclear plant is to undergo tests before entering the harsh radioactive environment, it’s been reported.

Developed by the Universities of Tokyo and Tsukuba, and the International Research Institute for Nuclear Decommissioning (IRID), the remotely-controlled robot will use 360-degree cameras and lasers to create a three-dimensional map of the inside of the reactor buildings. It will help plant operator Tepco to know how much wreckage needs to be cleared before decontamination work can begin, Japanese newspaper The Mainichi reports.

The cameras, which are mounted on top of the robot, will give a panoramic view to scientists who have so far been hampered by a lack of clear information. “We’ve expanded the field of vision, so it should give the workers operating the robot a bird’s-eye view of what they’re doing,” an unnamed project official tells The Mainichi.

The Fukushima plant suffered a meltdown after a massive earthquake and subsequent tsunami in March 2011. Efforts to clean up the site have been repeatedly held up by obstacles blocking remotely-controlled devices, as well as high levels of radiation inside the power plant. In April, a robot failed after three hours inside the reactor building, and while a flying drone has been tested for use at the site, it has not entered the most badly damaged buildings. It’s estimated that decontaminating the Fukushima site will take up to 40 years and cost tens of billions of dollars. ”

source

Japan to start Fukushima fuel debris retrieval in 2021 — World Nuclear News

” Japan expects to start the retrieval of fuel debris from the Fukushima Daiichi nuclear power plant in 2021, the executive director of the Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF) said yesterday. Three of the plant’s six reactors suffered core meltdowns in the March 2011 accident, leaving melted nuclear fuel debris on the floor of their containment vessels.

NDF was established in September 2011 by the Japanese government and the country’s nuclear power plant operators to manage a fund to support operators in providing compensation to victims of nuclear accidents. Although established following the Fukushima Daiichi accident, NDF will continue to be maintained in the future as part of the Japanese nuclear liability regime.

“We expect to select the retrieval method within the next few years, after which detailed design and mock-up tests will follow,” NDF executive director Yasuharu Igarashi told delegates at the VII Atomexpo conference in Moscow. The event was hosted by Russian state nuclear corporation Rosatom. “For the start of retrieval of fuel debris, we are now thinking 2021,” Igarashi said.

NDF has identified three “priority methods” for retrieving highly radioactive nuclear fuel debris in three reactors at Tokyo Electric Power Company’s (Tepco’s) Fukushima Daiichi plant. They are: submersion; partial submersion top access; and partial submersion side access. The first two rely on the removal first of core internals above fuel debris, while the third requires that the reactor pressure vessel pedestal exterior component inside the primary containment vessel (PCV) and interference have first been removed.

The submersion method would remove the debris in a submerged condition, with the containment vessel filled with water to shield against radiation and prevent the spread of radioactive materials during the retrieval process. The reactor damage would need to be accurately identified and repaired before water is poured in. Partial submersion means that water would only be used when the debris has been separated from the vessel floor. The debris would be removed from either the top or the side of the vessel. This method would require continuous cooling of the retrieved debris and measures to prevent radioactive materials from scattering.

Tepco started inspections of unit 1 of the plant in April using robots mounted with cameras and radiation-measuring equipment. The shape-changing robot began surveying conditions within the PCV of the damaged unit on 10 April. However, the robot stopped working before completing its mission. The robot was developed by the International Research Institute for Nuclear Decommissioning and Hitachi-GE Nuclear Energy to investigate hard-to-access areas of the plant. Tepco later sent in a second robot On April 20. The company said that it had decided not to try to retrieve a second robot dispatched inside the unit to avoid it becoming blocked and impeding future missions.

Igarashi said that NDF is following five “guiding principles” for risk reduction in its strategic plan for decommissioning the Fukushima Daiichi plant. They are that the plan is safe, proven, efficient, timely and “field-oriented”, meaning it is based on the actual conditions of the site and structures.

“The decommissioning of the Fukushima Daiichi nuclear power plant is a continuous risk reduction activity to protect people and the environment from the risk of radioactive materials resulting from the severe accident,” he said. “A risk reduction strategy along a mid- to long-term timeline will be designed in NDF’s strategic plan.”

The structure of NDF’s risk management strategy is to be completed by 2017, he said.

In addition to fuel debris retrieval, the strategic plan will also include a policy for waste management involving storage, processing and disposal methods, he said.

NDF has reviewed international standards for waste management, he said, and the International Atomic Energy Agency’s General Safety Requirements Part 5 and Specific Safety Requirements-5 are “important references”. ”

source

*Lowball nuclear pitch is fooling no one — The Japan Times

” Earlier this month, the Ministry of Economy, Trade and Industry (METI) announced the results of a review of energy production costs, which concluded that nuclear will remain the cheapest alternative for Japan over the next 15 years while pointing out that the calculations took into consideration the government’s new safety measures. By 2030, the cost of producing a kilowatt hour of electricity in a nuclear plant is expected to increase from ¥8.9 to ¥10.1. This estimate also incorporates the presumed savings resulting from those new safety measures, which, METI assumes, will reduce the “frequency” of reactor accidents.

In comparison, energy derived from coal will cost ¥12.9 per kilowatt hour and from LNG ¥13.4, though these figures are based on price increases predicted in 2011. More significantly, the cost of solar will rise from ¥12.4 to ¥16, and wind from ¥13.9 to ¥33.1. Geothermal comes in at ¥19.2. METI said these high costs will “affect development” of renewables, implying that there isn’t much of a future for them.

A few days later, Shukan Asahi ran an article assessing these calculations, pointing out that the figure of ¥10.1 per kW/hour for nuclear is, in the ministry’s statement, followed by the word ijō, meaning “at least,” while figures for other energy sources are not. The Asahi suggests that METI is trying to assure deniability because it’s almost certain that nuclear-related costs will increase in the future. According to Kenichi Oshima, professor of environmental economics at Ritsumeikan University, the ¥9.1 trillion needed to clean up the crippled Fukushima No. 1 nuclear plant and pay compensation to locals affected by the accident was not factored into the estimate; nor was the cost of decommissioning not only Fukushima No. 1 but other reactors scheduled to go out of service in the next 15 years, and Tokyo Electric Power Co. hasn’t even set a budget for decommissioning Fukushima, a separate procedure from the cleanup. To put matters into perspective, the estimated amount of radioactive material at Fukushima that needs to be processed is equivalent to the amount of radioactive material that would need to be processed from the normal decommissioning of 54 nuclear reactors.

Decommissioning involves removing the spent fuel from the reactor and then disassembling the containment vessel and tearing down the facility. Tepco maintains it has expertise in this area, based on its decommissioning of a test reactor in Tokaimura, Ibaraki Prefecture. The group that carried out that work says 99 percent of the radiation in the plant was in the fuel rods, so that was the only waste that required special handling.

But Japan still lacks facilities for storing high-level radioactive waste. At present, spent fuel rods are kept on-site at the nuclear plants from which they’re removed, whether these plants are in operation or not, and high-level waste stays radioactive for hundreds of years. Even low-level irradiated waste, such as the discarded containment vessel, has to be isolated for 30 to 50 years. Tokaimura’s decommissioning was supposed to be completed by 2017, but there is still no solution to the waste problem, so the timetable has been extended to 2025.

But this “easy” scenario for decommissioning doesn’t apply to Fukushima, because Tepco doesn’t know exactly how much high-level radioactive material has to be removed — or even where it is. NHK World elicited a frank evaluation of the situation from Naohiro Masuda, the man in charge of decommissioning Fukushima No. 1, on “Newsline,” its English-language news program. Masuda doesn’t believe decommissioning can start before 2020, and betrays doubt as to whether a proper cleanup of the plant “is even possible.”

The public broadcaster went further last week with a documentary in its series “Decommissioning Fukushima,” a process that, under the most favorable circumstances, won’t be completed until 2051.

There are few examples to follow for the people trying to clean up the crippled reactors. It took workers at Pennsylvania’s Three Mile Island nuclear plant three years to find the radioactive debris after the 1979 meltdown, and another 11 years to remove it, and that was only one reactor. Fukushima has three damaged reactors, within which the radiation is lethal, so Tepco and its affiliates designed a ¥1.5 billion robot to enter the reactor and look around. It got stuck mid-inspection.

NHK shows how Tepco has sought advice from experts in France and South Korea to facilitate the cleanup, and while these consultations yield useful ideas, as the program points out, all accidents are unique, which means cleaning up after them is invariably complicated.

Meanwhile, expenses are accumulating at a rate that makes them difficult to project, but according to a different Shukan Asahi article, Japan’s nuclear industry has set the cost of decommissioning at between ¥55 billion and ¥70 billion per reactor. Germany and the U.K., which have each decommissioned a number of reactors, spent the equivalent of between ¥250 billion and ¥300 billion.

The online magazine Business Journal recently explained the matter in bookkeeping terms. Kansai Electric and other power companies plan to decommission at least five superannuated reactors rather than apply for extensions because their respective output isn’t enough to pay for the government’s new safety measures, which cost about ¥10 billion per reactor. The problem is that once a reactor is shut down permanently, in addition to the cost of decommissioning, the company’s revenue for that plant drops to zero, thus hurting its bottom line even more and making it difficult to borrow money or issue bonds. Consequently, METI is thinking of changing the accounting system so that companies can spread this loss over 10 years, during which they can add a surcharge to every customer’s bill for decommissioning.

Obviously, when METI says nuclear is the cheapest form of energy, they’re not thinking about the user. ”

source