Remote-controlled probe picks up radioactive debris at Fukushima for the first time — Gizmodo

” Tepco, the state-owned operator of the badly damaged Fukushima nuclear plant, has conducted an important test in which a remote-controlled probe managed to grasp several small grains of radioactive debris, AFP reports. The successful operation marked an important achievement for the company as it prepares for a cleanup operation that could take decades.

In March 2011, the devastating Tōhoku earthquake and tsunami triggered the core meltdown of three reactors at the Fukushima Daiichi nuclear power plant. Eight years later, the plant’s operator, Tokyo Electric Power Company Holdings (Tepco), is still in the formative stages of devising a clean-up plan.

The primary challenge, of course, is dealing with the intense radiation emanating from the melted fuel. Two years ago, for example, a robot became unresponsive after just two hours in reactor No. 2; there’s enough radiation down there—approximately 650 sieverts per hour—to fry a person within a few seconds. The episode showed that technical advancements will be required to make robots more resilient to radiation near the core, and that the cleanup will likely take longer than expected.

Early last year, a camera attached to a remote-controlled probe was sent into reactor No. 2. Images confirmed that fuel debris had melted through the reactor pressure vessel (RPV), also known as the reactor core, dripping down into a collection chamber known as the primary containment vessel (PCV). Images of the chamber showed pebble- and clay-like deposits covering the entire bottom of the PCV pedestal. This accumulated waste, along with similar piles at reactors No. 1 and 3, needs to be cleaned up, and Tepco is currently trying to determine the best way of doing so.

To that end, the state-owned company devised an operation to see what that material is like and determine if it can be moved. On Wednesday February 13, Tepco sent a probe equipped with a remotely operated robotic hand down into the No. 2 lower chamber, Japan Times reports. Using its tong-like fingers, the probe picked up five grain-sized pieces of radioactive melted fuel. AFP reported that the pieces were moved to a maximum height of 2 inches (5 centimeters) above the bottom of the chamber. In addition to taking images with a camera, the probe measured radiation and temperature during the investigation, according to a Tepco release.

No radioactive debris was removed from the chamber, but the eight-hour-long operation showed that some of the melted fuel can be moved—an important bit of evidence that will inform future plans to clean up the plant. But as the Japan Times noted, one of the six areas explored by the probe contained debris that had solidified into a clay-like substance, which the robotic hand was unable to grasp. Future robots will need to slice or saw through this material such that it can be removed. That won’t be easy.

A future test, planned for April, will see some debris removed from the chamber, according to the Japan Times. Tepco has yet to disclose how and where this radioactive waste will be stored.

The company is hoping to start removing radioactive fuel in earnest by 2021, but the clean-up is expected to take decades, with some estimates suggesting it won’t be done until the 2050s. Many other technological hurdles still exist, such as determining the full extent of structural damage at the Fukushima plant, locating all the melted fuel in the three damaged reactors, and figuring out a way to remove the large quantities of contaminated water stored at the site.

If that all sounds overwhelming, well, it is. As we’ve said before, when nuclear power goes wrong, it really goes wrong. ”

by George Dvorsky, Gizmodo

source with images and internal links

Here is a related article by Bloomberg.

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Challenges ahead for debris removal at Fukushima — NHK World

” This year will mark the 7th anniversary of the nuclear accident at the Fukushima Daiichi plant that occurred in March, 2011. The plant’s operator is hoping to eventually remove fuel debris from the damaged reactors.

Fuel debris is a mixture of melted nuclear fuel and broken reactor parts. Removing the debris is considered to be the biggest hurdle to the decommissioning of the reactors.

Last year, Tokyo Electric Power Company, or TEPCO, investigated the inside of the containment vessels of 3 reactors and confirmed, for the first time, the existence of lumps that are believed to be fuel debris in the No.3 reactor.

TEPCO plans to conduct a fresh probe of the No.2 reactor this month to confirm whether a mass on the floor under the reactor, observed last year, is actually fuel debris.

The government and TEPCO aim to begin removing debris in 2021. They are planning to determine which reactor to start with, and how to conduct the procedure, during fiscal 2019.

Workers will try this year to figure out which details need to be considered in order to make the decision.

Removing the debris requires thorough safety measures. For example, radioactive materials must be prevented from spreading and workers must be protected from exposure to radiation.

This autumn, the operator also plans to start removing spent nuclear fuel rods from the storage pool of the No.3 reactor building. ”

by NHK World

source

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

Tepco mandated to create fund for scrapping Fukushima plant — The Japan Times

” The Diet passed a bill Wednesday requiring Tokyo Electric Power Company Holdings Inc. to put aside extra funds to decommission its crisis-hit Fukushima nuclear power plant, as the state seeks to gain more financial control over the utility.

Under the revised law, the state-backed Nuclear Damage Compensation and Decommissioning Facilitation Corp. will also be involved in the decommissioning process.

Currently, Tepco has been using profits to pay for scrapping the Fukushima No. 1 plant, which was destroyed after a 2011 earthquake and tsunami triggered a triple meltdown.

The revised law is expected to take effect later this year. With the estimated cost of the decommissioning work already surging to ¥8 trillion from the previously forecast ¥2 trillion, a government panel has called for setting up a funding system that is not dependent on the company’s financial health.

The government projects the total cost to deal with the Fukushima nuclear disaster will reach ¥21.5 trillion, including decommissioning costs, compensation and decontamination work.

Under the new program, the state-backed organization will decide on the amount Tepco should store away each business year and the industry minister must approve it.

The utility must also formulate a financial plan and obtain the minister’s approval when it uses the reserve fund for its decommissioning work.

The new law will strengthen the monitoring power of authorities as well, enabling the industry ministry and the organization to conduct on-site inspections to check whether Tepco is putting aside the money.

The government has a major say in the utility’s operations after acquiring 50.1 percent of the company’s voting rights. Tepco faces huge compensation payments and decommissioning costs among other problems due to the 2011 disaster.

The industry ministry has projected roughly ¥300 billion will be needed annually for the next 30 years to complete the scrapping of the power plant, which involves the difficult procedure of extracting nuclear debris.

The costs could grow further. A study by a Tokyo-based private think tank has shown the bill for the decommissioning could balloon to between ¥11 trillion and ¥32 trillion assuming materials from the No. 1 to 3 reactors, which suffered core meltdowns, need to be specially treated for radioactive waste.

The Japan Center for Economic Research estimated the total cost of managing the disaster could reach ¥70 trillion, more than three times the government calculation. ”

by Kyodo, The Japan Times

source

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

source

Last cover removed from crippled reactor in Fukushima — The Asahi Shimbun; Crippled Fukushima reactor fully exposed for first time since meltdown — RT

The Asahi Shimbun:

” The No. 1 reactor at the Fukushima No. 1 nuclear power plant is completely exposed for the first time in five years after the last of the temporary protective covers for the crippled structure was removed Nov. 10.

The next step will be to extract nuclear fuel inside the reactor building, which was wrecked by a hydrogen explosion in the early stages of the March 2011 nuclear disaster.

The covers were installed the following October as a temporary measure against the spread of radioactive substances after the triple meltdown triggered by the Great East Japan Earthquake and tsunami.

A large crane lifted off the 20-ton cover, the last of the 18 panels installed, around 6 a.m. on Nov. 10.

Plant operator Tokyo Electric Power Co. began removing the covers one by one in September.

The 392 fuel assemblies are stored in the spent nuclear fuel pool inside the building. Melted fuel also remains inside the reactor.

TEPCO will assess the state of the reactor building’s interior in efforts to remove debris from the collapse of a roof over the spent nuclear fuel pool.

It will take precautions to prevent dust containing radioactive substances from being stirred up by shrouding the reactor building with tarpaulins. ”

by Kohei Tomida

source with aerial view video of uncovered Unit 1 reactor

* * *

RT:

” Fukushima’s Nuclear Plant reactor No. 1 has been fully exposed for the first time since the March 2011 tragedy, after the utility company safely removed the last cover sheet of the temporary protective construction.

Tokyo Electric Power Co. (TEPCO) used an industrial crane to lift the last of its 18 protective panels Thursday. Each of the panels weighs around 20 tons and measure 23 by 17 meters.

The protective cover was erected in October 2011 as a temporary measure to halt a radiation leak following a meltdown caused by a powerful earthquake and tsunami in March 2011. The dismantling of the panels started in July 2015 and was concluded on Thursday.

At Unit 1, rubble from the damaged building caused by the hydrogen explosion remains scattered and needs to be removed. The entire site is highly contaminated and will now be covered with tarpaulins to avoid the spread of radioactive waste. TEPCO is using anti-scattering agents to keep the dust down. Small pieces of rubble that can create dust are being vacuumed up while mist sprinklers are being used inside the building to keep radiation under control.

TEPCO next plans to remove 392 fuel assemblies from the spent pool and clean out the melted nuclear fuel from inside the building, NHK news reported. The utility company is assessing the level of radiation before continuing the cleanup process.

Scientists are also installing the necessary equipment to complete fuel extraction which will only start in four years. Fuel removal from Unit 1’s depleted fuel pool is scheduled to begin around March 2021, according to TEPCO’s Mid- and Long-Term Roadmap that was revised in June 2015.

In March 2011, a tsunami destroyed emergency generators at the plant. They had been cooling the reactors. The tsunami led to three nuclear meltdowns and the release of radioactive material. In Reactor 1, overheating caused the creation of hydrogen gas. On March 12, an explosion in Unit 1 destroyed the upper part of the building.

TEPCO’s decommission plan for the Fukushima nuclear power plant implies at least a 30-40 year period before the consequences of the meltdown are fully eliminated. So far the clean-up efforts have already cost Japan in excess of $21 billion. According to the latest estimates from the Ministry of Economy, Trade and Industry, the decommissioning costs will top $105 billion. ”

source