New proposal suggests removing Fukushima plant’s melted nuclear fuel from side — The Mainichi

” A method to remove melted nuclear fuel debris on the bottom of the containment vessels of Fukushima No. 1 Nuclear Power Plant’s first, second and third reactors from the side was proposed by the Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF) on July 31.

Hajimu Yamana, head of the NDF, which is tasked with considering how to remove fuel debris from the reactors, for the first time explained the organization’s specific method proposal to the heads of local governments at a countermeasures for the decommissioning and handling of the contaminated water council meeting held in Iwaki, Fukushima Prefecture.

The method would focus on prioritizing the removal of debris from the bottom of the vessels from the side, using robotic arms and other remote devices while flushing water over the debris. However, ways to block radiation and countermeasures against the scattering of airborne radioactive dust still remain unsolved. The central government and Tokyo Electric Power Co. (TEPCO) plan to finalize their policy to remove the debris and amend the decommission schedule in September.

In all three of the reactors, contaminated water has collected at the bottom of the containment vessels. The NDF had previously considered a “flooding method” that would fill the containment vessels completely with water to block radiation from leaking. However, measures to repair the containment vessels and prevent leakage of the radioactive water would be difficult, so the plan was put aside for having “too many issues.” “

by The Mainichi

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

Minister opposes releasing treated water from Fukushima plant into sea — The Mainichi

According to The Georgia Straight, plans to dump tritium-contaminated waste water into the Pacific Ocean have been cancelled.

The Mainichi: ” TOKYO (Kyodo) — Japan’s disaster reconstruction minister said Friday he is opposed to treated water from the disaster-struck Fukushima Daiichi nuclear power plant being released into the sea, citing the possible repercussions for local fishermen.

Masayoshi Yoshino’s remarks came shortly after a top official from plant operator Tokyo Electric Power Company Holdings Inc. said he is ready to see the tritium-containing water dumped into the sea.

A government panel is still debating how to deal with the water stored in tanks at the plant where three nuclear reactors melted down in the days after a huge earthquake and then tsunami struck the region in 2011.

Tritium is a radioactive substance considered relatively harmless to humans. It remains in the filtered water as it is difficult to separate even after passing through a treatment process. At other nuclear power plants, tritium-containing water is routinely released into the sea after it is diluted.

Yoshino expressed at a news conference his concerns over the potential ramifications of releasing the treated water into the sea, saying there would “certainly be (perception) damage due to unfounded rumors.”

The minister urged those pushing for the release of the water “not to create fresh concerns for fishermen and those running fishing operations in Fukushima Prefecture.” He also asked them “not to drive (fishermen) further towards the edge.”

He was alluding to concerns among local fishermen about the effects on their livelihood if the public perceives fish and other marine products caught off Fukushima to be contaminated.

Takashi Kawamura, chairman of Tepco, said in a recent interview that the decision to discharge the treated water “has already been made.”

After Kawamura’s remarks were widely reported, the utility was forced to make a clarification through a statement on Friday. Tepco said its chairman meant to say there is “no problem (with releasing water containing tritium) according to state guidelines based on scientific and technological standpoints,” and that the decision to release is not yet final.

While the plant operator and the Ministry of Economy, Trade and Industry want to discharge the water, the local fishermen, backed by the minister, are opposed to it.

At the Fukushima plant, water becomes toxic when it is used to cool the damaged reactors. It is treated through a process said to be capable of removing 62 different types of radioactive material, except tritium.

Yoshino said Friday that while he is aware of some scientists’ opinion that the water should be released after it is diluted to permissible levels, he is not in favor of the idea.

“As I am also a native of Fukushima Prefecture, I fully understand the sentiment of the people,” Yoshino said. However, the minister has no authority to decide how the treated water will be disposed.

An ever-increasing amount of water containing tritium is collecting in tanks at the Fukushima plant. As of July 6, approximately 777,000 tons were stored in about 580 tanks.

On March 11, 2011, water inundated the six-reactor plant, located on ground 10 meters above sea level, and flooded power supply facilities. Reactor cooling systems were crippled and the Nos. 1 to 3 reactors suffered fuel meltdowns in the world’s worst nuclear catastrophe since the 1986 Chernobyl disaster. “

by The Mainichi

source

Fishermen express fury as Fukushima plant set to release radioactive material into ocean — The Telegraph

” Local residents and environmental groups have condemned a plan to release radioactive tritium from the crippled Fukushima nuclear plant into the Pacific Ocean.

Officials of Tokyo Electric Power Co., the operator of the plant, say tritium poses little risk to human health and is quickly diluted by the ocean.

In an interview with local media, Takashi Kawamura, chairman of TEPCO, said: “The decision has already been made.” He added, however, that the utility is waiting for approval from the Japanese government before going ahead with the plan and is seeking the understanding of local residents.

The tritium is building up in water that has been used to cool three reactors that suffered fuel melt-downs after cooling equipment was destroyed in the magnitude 9 earthquake and tsunami that struck north-east Japan in March 2011.

Around 770,000 tons of highly radioactive water is being stored in 580 tanks at the site. Many of the contaminants can be filtered out, but the technology does not presently exist to remove tritium from water.

“This accident happened more than six years ago and the authorities should have been able to devise a way to remove the tritium instead of simply announcing that they are going to dump it into the ocean”, said Aileen Mioko-Smith, an anti-nuclear campaigner with Kyoto-based Green Action Japan.

“They say that it will be safe because the ocean is large so it will be diluted, but that sets a precedent that can be copied, essentially permitting anyone to dump nuclear waste into our seas”, she told The Telegraph.

Fishermen who operate in waters off the plant say any release of radioactive material will devastate an industry that is still struggling to recover from the initial nuclear disaster.

“Releasing [tritium] into the sea will create a new wave of unfounded rumours, making all our efforts for naught”, Kanji Tachiya, head of a local fishing cooperative, told Kyodo News. ”

by Julian Ryall, The Telegraph

source

Nuclear authority chief raps Tepco’s attitude toward Fukushima — The Mainichi

” TOKYO (Kyodo) — The head of Japan’s nuclear safety watchdog on Monday criticized the attitude of Tokyo Electric Power Company Holdings Inc. toward decommissioning of the crisis-hit Fukushima Daiichi nuclear power plant and questioned the company’s ability to resume operation of other reactors.

 “I feel a sense of danger,” Nuclear Regulation Authority Chairman Shunichi Tanaka said during a special meeting with the company’s top management, adding that Tokyo Electric does “not seem to have a will to take initiative” toward decommissioning of the crippled Fukushima Daiichi plant.

Takashi Kawamura, the chairman of the power company known as Tepco, and its president, Tomoaki Kobayakawa, attended the meeting. The authority felt it is necessary to hear from the top executives before it could make a decision on whether to approve Tepco’s plan to resume operation of the Nos. 6 and 7 reactors at its Kashiwazaki-Kariwa plant in Niigata Prefecture.

Tepco filed for state safety assessment of the two reactors in September 2013 to reactivate them, hoping to restore its financial condition as it needed massive funds to pay compensation related to the Fukushima Daiichi disaster, triggered by a huge earthquake and tsunami on March 11, 2011, and to scrap the plant that suffered meltdowns.

The watchdog’s safety screening has found Tepco’s failure to report insufficient earthquake resistance of a facility built to serve as the base to deal with a possible nuclear accident at the Niigata complex although it had acknowledged the insufficiency for three years.

In June, Tepco submitted to the watchdog its revised safety measures for the Kashiwazaki-Kariwa complex.

“An operator lacking will to take initiative does not have the right to resume operation of nuclear reactors,” Tanaka said.

Tepco’s chairman responded by saying, “There are citizens who believe nuclear power is necessary. Operating reactors is our responsibility.”

But he also admitted there is room for only two more years’ worth of space in the tanks to accommodate contaminated water stemming from the Fukushima complex.

At Monday’s meeting, the watchdog asked Tepco’s top management about the company’s safety measures for the Niigata complex on the Sea of Japan coast as well as its safety awareness.

Tanaka said the authority does not view that it received sufficient responses from Tepco at the meeting and requested that the company submit more explanation on its plan to decommission the Fukushima complex and resume operation of the two reactors at the Kashiwazaki-Kariwa plant.

Tanaka plans to conduct on-site checkups at the two reactors of the plant in Niigata, saying, “Tepco, which caused the (Fukushima) accident, is not an ordinary operator.”

The two boiling water reactors at the Niigata plant are the same type as those that suffered core meltdowns at the Fukushima Daiichi complex, and no such reactors have cleared the authority’s safety screening since the Fukushima disaster. “

source

NRA: Ice wall effects ‘limited’ at Fukushima nuclear plant — The Asahi Shimbun

” Citing “limited, if any effects,” the Nuclear Regulation Authority said a highly touted “frozen soil wall” should be relegated to a secondary role in reducing contaminated groundwater at the Fukushima No. 1 nuclear plant.

The government spent 34.5 billion yen ($292 million) to build the underground ice wall to prevent groundwater from mixing with radioactive water in four reactor buildings at the crippled plant.

But the NRA, Japan’s nuclear watchdog, concluded on Dec. 26 that the wall has been ineffective in diverting the water away from the buildings. It said that despite the low rainfall over the past several months, the amount of groundwater pumped up through wells outside the frozen wall on the seaside is still well above the reduction target.

It urged the plant operator, Tokyo Electric Power Co., to tackle the groundwater problem primarily with pumps, not the ice wall.

In response, TEPCO at the meeting said that by next autumn, it will double its capacity to pump up groundwater from the current 800 tons a day.

About 400 tons of groundwater enters the damaged reactor buildings each day and mixes with highly radioactive water used to cool melted nuclear fuel.

The ice wall project, compiled by the industry ministry in May 2013, was seen as a fundamental solution to this problem that has hampered TEPCO’s cleanup efforts since the triple meltdown in March 2011.

Some 1,568 frozen ducts were inserted 30 meters deep into the ground to circulate a liquid at 30 degrees below zero. The freezing process was supposed to have created a solid wall of ice that could block the groundwater.

TEPCO began freezing the wall on the seaside in March. It announced in the middle of October that the temperature at all measuring points in that area was below zero.

Before the frozen wall project, TEPCO had to pump up about 300 tons of contaminated water a day. The daily volume dropped to about 130 tons in recent weeks, but it was still well beyond the target of 70 tons.

Still, TEPCO boasted about the effectiveness of the ice wall at the meeting with the NRA on Dec. 26, saying, “We are seeing certain results.”

The NRA, however, said the results are limited at best.

Toyoshi Fuketa, an NRA commissioner, already warned TEPCO in October that it cannot expect the ice wall to be highly effective in containing the groundwater.

“Pumping up groundwater through wells should be the main player because it can reliably control the groundwater level,” Fuketa said at that time. “The ice wall will play a supporting role.”

That sentiment was echoed at the Dec. 26 meeting.

However, the NRA approved the utility’s plan to begin freezing dirt for a wall on the mountain side of the nuclear plant.

The NRA was previously concerned about risks posed by the new ice wall. If it totally blocked groundwater from the mountain side, the water level within the frozen soil near the reactors could become too low, allowing highly contaminated water inside the reactor buildings to flow out more rapidly.

The NRA urged TEPCO to delay work on the mountain side until the ice wall on the seaside portion proved effective.

But it reversed its stance, saying a sharp drop in the groundwater level is unlikely based on the ineffectiveness of the existing ice wall.

“The frozen wall on the mountain side will not be able to block groundwater because the wall on the seaside was also unable to do so,” Fuketa said. “It will not be very dangerous to freeze the wall on the mountain side as long as the work is carried out carefully.”

TEPCO will start the work to freeze the ducts at five sections as early as next year.

Masashi Kamon, professor emeritus of geotechniques at Kyoto University, expressed skepticism about continuing the ice wall project without a full scrutiny of the underground conditions.

“Soil around the tunnels for underground pipes must be hard to freeze,” he said. “TEPCO should find out the conditions of the very bottom of the ice wall by drilling at least one section. It is questionable to continue with the project without a review.” ”

by Kohei Tomida

source