Tag Archives: decommissioning Fukushima

A Never-Ending Disaster: radioactive water at Fukushima

A Greenpeace report details how plans to discharge over 1 million tonnes of highly contaminated water into the Pacific Ocean was proposed by a Japanese government task force.  According to Greenpeace.

“The decision not to develop water processing technology that could remove radioactive tritium was motivated by short term cost cutting not protection of the Pacific ocean environment or the health and livelihoods of communities along the Fukushima coast,” said Kazue Suzuki, Energy Campaigner at Greenpeace Japan. “  The report concludes that the water crisis remains unresolved, and will be for the foreseeable future. The only viable option to protect the environment and the communities along the Fukushima coast being long term storage for the contaminated water.

The discharge option for water containing high levels of radioactive tritium was recommended as least cost by the Government’s Tritiated Water Task Force and promoted by Japan’s Nuclear Regulation Authority (NRA). The Task Force concluded in 2016 that “sea discharge would cost 3.4 billion yen (US$30 million) and take seven years and four months to complete. It concluded that this was cheapest and quickest of the five methods.” However, technical proposals for removing tritium were submitted to the same Government Task Force by multiple nuclear companies with estimated costs ranging from US$2-US$20 billion to US$50-US$180 billion depending on the technology used. These were dismissed as not viable but without detailed technical consideration.

TEPCO has claimed since 2013 that its ALPS technology would reduce radioactivity levels “to lower than the permissible level for discharge.” However, in September 2018 TEPCO admitted that the processing of over 800,000 tons of contaminated water in 1000 storage tanks, including strontium, had failed to remove radioactivity to below regulatory limits, including for strontium-90, a bone seeking radionuclide that causes cancer. TEPCO knew of the failure of the technology from 2013. The Greenpeace report details technical problems with the ALPS system.

The Fukushima Daiichi site, due its location, is subject to massive groundwater contamination which TEPCO has also failed to stop. Each week an additional 2-4000 tonnes of contaminated water is added to the storage tanks.

Excerpts from Technical failures increase risk of contaminated Fukushima water discharge into Pacific, Greenpeace Press Release,  Jan. 22, 2019

Nuclear Robots

Robots have been used in nuclear facilities for a long time.Scenarios such as maintenance tasks in nuclear facilities or even disasters like radioactive leaks or search and rescue operations have proven to be quite successful. We are talking about robotic  arms or remote operated vehicles with some end effectors built in to handle dangerous situations.”

1986: Chernobyl’s robot trouble–During the Chernobyl nuclear incident, the Soviet authorities in charge of cleaning up nuclear waste developed around 60 unique remote-controlled robots to spare human workers from radioactive exposure. The total cost of the clean-up operation was $2bn.  Designs included the STR-1 robot, which resembles a moon buggy. It was placed on the roof of the nuclear plant and used to clean upparts of the destroyed reactor. Another design for the purpose of debris cleaning was the Mobot, developed by Moscow State University. It was a smaller version of a loader used in construction, with a front-end bucket used to  scoop up debris.

The problem was that cleaning up nuclear waste required more skills than the robots could provide, eventually resulting in the authorities sending in soldiers to perform most of the decontamination works. Radiation was so high that each worker could only spend 40 seconds inside or near the facility; 31 died from exposure, while 237 suffered from acute radiation sickness.

2008: Cleaning up nuclear waste at Hanford Nuclear Reservation. The Hanford Nuclear Reservation in the US has been somewhat of a hub for nuclear waste innovation. This is because scientists, and their robot friends, are faced with the task of emptying nuclear and chemical waste tanks the size of around 150 basketball courts before the waste reaches the Columbia River. Exposure to the material would kill a human instantly.

Luckily, Hanford has developed a few automated machines thatare specifically designed for different parts of the job. Take Foldtrack, for example, which can access the tanks through one-foot-wide pipes in the roof bysplitting into a string of pieces, and then rebuilding itself like a Transformer once inside. The remote-controlled robot uses a 3,000psi water cannon to blast nuclear sludge off the walls of the tank and pump it out. Upon completion, scientists are forced to leave the $500,000 robot in the tank due to the high levels of contamination.

Another robot, the Sand Mantis, looks like a fire hose on wheels. However, it comes packed with power, with the ability to blast tough toxic salts that build up in waste tanks with its 35,000psi water cannon. For comparison, a regular firehose has around 300psi of pressure. In order to support the huge power, the orifice of the hose is made of gems, such as sapphires, which can withstand the pressure….Finally, the Tandem Synthetic Aperture Focusing Technique,or Tank Crawler, locates cracks or corrosion in Hanford’s waste storage tanks using ultrasonic and electrical conductivity sensors.

2011: Fukushima—Previously designed robots failed to visually inspect the reactor, either breaking due to high radiation or by getting stuck in the confined spaces. That was until Toshiba’s senior scientist in its technology division, Kenji Matsuzaki, developed the Little Sunfish – an amphibious bread loaf-sized robot that could slip into the 5.5-inch reactor pipelines.

In 2017,  the Sellafield nuclear site in the UK, scientists have been working on methods to clean up the vast amounts of nuclear sludge from its First-Generation Magnox Storage Pond, as part of decommissioning efforts said to cost around £1.9bn each year. The size of two Olympic swimming pools, the storage pond contains large amounts of nuclear sludge from decaying fuel rods stored below the surface.  While robots have been designed to reach the depths of the pond and remove nuclear waste, none proved to be very successful, until Cthulhu– Collaborative Technology Hardened for Underwater and Littoral Hazardous Environment.  Cthulhu is a tracked robot that can move along the bottom ofthe storage pond, using whisker-like sensors and sonar to identify and retrieve the nuclear rods.

2018:  The South West Nuclear Hub at the University of Bristol inthe UK is collaborating with Sellafield to develop a nuclear waste robotic suit for humans, taking inspiration from the comic book hero Iron Man.

Excepts from Cherno-bots to Iron Man suits: the development of nuclear waste robotics,, Power-Technology. com, Dec. 4, 2018

Dismantling Nuclear Reactors at Fukushima

In the aftermath of the Fukushima nuclear disaster in 2011, Naraha decided to oppose nuclear energy and call for the closure of the Fukushima No. 2 nuclear power plant that it co-hosts on the coast of the prefecture.  Since the 1970s, the town has been home to the No. 2 plant, which first went into service in 1982.  For decades, Naraha has received central government grants and subsidies for hosting the No. 2 plant, as well as tax revenues from TEPCO and its affiliates operating in the town.The plant also employed 860 people, many of them from Naraha and its surrounding communities.

Naraha had a population of about 8,000 before the Great East Japan Earthquake and tsunami caused the triple meltdown at TEPCO’s Fukushima No. 1 nuclear plant in March 2011. The crippled plant is located within 20 kilometers from Nahara.  The quake and tsunami also created a scare at the No. 2 plant by leaving the facility with only a limited power supply from external sources and emergency diesel generators to cool the reactors. But the plant brought the situation under control.

After long remaining silent about the fate of the No. 2 plant, TEPCO decided to retire all of its four reactors, which were approaching their legal operating limit of 40 years. If the power company wanted to continue operations at the plant, it would have to spend hundreds of billions of yen on upgrades to meet the more stringent safety standards that were set after the accident at the No. 1 plant…

Although Naraha and Tomioka officials share concerns about their municipalities’ financial futures, they see a silver lining in the situation at the Fukushima No. 1 nuclear plant.  Both towns have served as front-line bases for workers involved in decommissioning of the stricken plant.  About 5,000 workers a day who are involved in the decommissioning effort provide steady business for convenience stores and other shops in the two towns. Business hotels, dorms and apartment buildings have been built in the towns and neighboring communities to accommodate the workers. Work to dismantle the No. 1 plant is expected to take decades to complete. Local officials said the closure of the No. 2 plant could bring about a similar economic boon. “Decommissioning can become a major industry,” Naraha Mayor Matsumoto said.

Excerpts from  Nuclear plant closure brings hope, despair to Fukushima town
THE ASAHI SHIMBUN, October 18, 2018

Melted Nuclear Fuel at Fukushima

jA robot operating deep inside a failed reactor at the stricken Fukushima nuclear plant north of Tokyo has revealed what appears to be stalactites of melted nuclear fuel, the plant’s operator has said.  The discovery is considered a key development in the decommissioning process of the plant, which suffered a catastrophic meltdown in 2011 after a huge tsunami swamped the facility.

Operating remotely within submerged parts of the Fukushima Daiichi plant’s Unit 3 reactor, the robot sent back 16 hours worth of images of massive, lava-like fuel deposits on the floor of the pedestal, a part of the reactor that sits underneath and supports the core….The discovery is key to determining how to further advance the cleanup of the plant, a process that is expected to take decades.  “This was the first time that we could confirm the status inside the pedestal,” TEPCO spokesperson Maki Murayama said. “This is a big step towards the decommission process.”..

Having entered the stricken Pressure Containment Vessel (PCV) through a pipe designed to prevent the escape of radioactive gas, the robot descended into the cooling water which accumulated following the accident.  The device was equipped with thrusters to navigate through the water, and featured front and rear cameras.  The small “radiation-hardened, screw-driven” submersible robot was designed to fit through the narrow, 14-centimeter (5.5-inch) diameter entrance of the pipe, according to the Tokyo-based International Research Institute for Nuclear Decommissioning (IRID), which developed the device alongside technology company Toshiba.

As the robot navigates through the ruined reactor, melted equipment and the fuel deposits can be seen.

The mission was launched after previous photographic inspection of the Unit 3 reactor suggested that, “during the accident, fuel assemblies melted from the excess heat, dropping from their original position down to the pedestal area,” according to a statement released by TEPCO.

Excerpt from Euan McKirdy and Yoko Wakatsuki, Fukushima robot reveals first sign of melted fuel in submerged reactor, CNN, July 24, 2017

Japan’s Nuclear Waste

Japan seeks final resting place for highly radioactive nuclear waste…[W]ith a number of Japan’s nuclear reactors closed down for good in the wake of the Fukushima accident, the need for a permanent storage site is more pressing than ever.

The disaster, in which a 13-meter tsunami triggered by an off-shore earthquake crippled four reactors at the plant and caused massive amounts of radioactivity to escape into the atmosphere, also underlined just how seismically unstable the Japanese archipelago is and the need for the repository to be completely safe for 100,000 years.

“They have been trying to get this plan of the ground for years and one thing they tried was to offer money to any town or village that agreed to even undergo a survey to see if their location was suitable,” she said.  “There were a number of mayors who accepted the proposal because they wanted the money – even though they had no intention of ever agreeing to host the storage site – but the backlash from their constituents was fast and it was furious,” Smith added.  “In every case, those mayors reversed their decisions and the government has got nowhere,” she said. “But I fear that means that sooner or later they are just going to make a decision on a site and order the community to accept it.”

The security requirements of the facility will be exacting, the government has stated, and the site will need to be at least 300 meters beneath the surface in a part of the country that is not subject to seismic activity from active faults or volcanoes. It must also be safe from the effects of erosion and away from oil and coal fields. Another consideration is access and sites within 20 km of the coast are preferred.

The facility will need to be able to hold 25,000 canisters of vitrified high-level waste, while more waste will be produced as the nation’s nuclear reactors are slowly brought back online after being mothballed since 2011 for extensive assessments of their safety and ability to withstand a natural disaster on the same scale as the magnitude-9 earthquake that struck Fukushima.

When it is released, the government’s list is likely to include places in Tohoku and Hokkaido as among the most suitable sites, because both are relatively less populated than central areas of the country and are in need of revitalization efforts. Parts of Tohoku close to the Fukushima plant may eventually be chosen because they are still heavily contaminated with radiation from the accident.

Excerpts from Japan seeks final resting place for highly radioactive nuclear waste, Deutsche Welle, May 4, 2017

Nuclear Waste at Fukushima: total amount

Each form of waste at the Fukushima Daiichi Nuclear Power Station, where three reactors melted down after an earthquake and a tsunami on March 11, 2011, presents its own challenges.

400 Tons of Contaminated Water Per Day
The Tokyo Electric Power Company is pumping water nonstop through the three reactors to cool melted fuel that remains too hot and radioactive to remove. About 400 tons of water pass through the reactors every day, including groundwater that seeps in. The water picks up radiation in the reactors and then is diverted into a decontamination facility.  But the decontamination filters cannot remove all the radioactive material. So for now, all this water is being stored in 1,000 gray, blue and white tanks on the grounds. The tanks already hold 962,000 tons of contaminated water, and Tokyo Electric is installing more tanks. It is also trying to slow the flow of groundwater through the reactors by building an underground ice wall.

Within a few years, though, and no one is sure exactly when, the plant may run out of room to store the contaminated water. “We cannot continue to build tanks forever,” said Shigenori Hata, an official at the Ministry of Economy, Trade and Industry.  The authorities are debating whether it might be acceptable, given the relatively low radioactive levels in the water, to dilute the contaminated water and then dump it into the ocean. But local fishermen are vehemently opposed. Many people still do not trust Tokyo Electric because of its bungled response to the disaster, the worst nuclear accident since Chernobyl.

3,519 Containers of Radioactive Sludge
The process of decontaminating the water leaves radioactive sludge trapped in filters, which are being held in thousands of containers of different sizes.Tokyo Electric says it cannot quantify the amount of radioactive sludge being generated. But it says it is experimenting with what to do with it, including mixing it with cement or iron. Then it will have to decide how to store it.

64,700 Cubic Meters of Discarded Protective Clothing
The estimated 6,000 cleanup workers at the site put on new protective gear every day. These hazmat suits, face masks, rubber gloves and shoe coverings are thrown out at the end of each shift. The clothing is compressed and stored in 1,000 steel boxes stacked around the site.To date, more than 64,700 cubic meters of gear has been discarded, the equivalent of 17 million one-gallon containers. Tokyo Electric says it will eventually incinerate all this contaminated clothing to reduce the space needed to store it.

Branches and Logs From 220 Acres of Deforested Land
The plant’s grounds were once dotted with trees, and a portion was even designated as a bird sanctuary. But workers have cleared about 220 acres of trees since the meltdown spewed radiation over them.Now, piles of branches and tree trunks are stacked all over the site. Officials say there are about 80,000 cubic meters of this waste, and all of it will have to be incinerated and stored someday.

200,400 Cubic Meters of Radioactive Rubble
Explosions during the meltdown filled the reactors with rubble. Workers and robots are slowly and carefully trying to remove this tangled mass of crushed concrete, pipes, hoses and metal.  Tokyo Electric estimates that more than 200,400 cubic meters of rubble — all of it radioactive — have been removed so far and stored in custom-made steel boxes. That is the equivalent of about 3,000 standard 40-foot shipping containers.

3.5 Billion Gallons of Soil

Thousands of plastic garbage bags sit in neat rows in the fields and abandoned towns surrounding the Fukushima plant. They contain soil that was scraped from land that was exposed to radiation in the days after the accident.  Japan’s Ministry of the Environment estimates that it has bagged 3.5 billion gallons of soil, and plans to collect much more. It will eventually incinerate some of the soil, but that will only reduce the volume of the radioactive waste, not eliminate it.  The ministry has already begun building a massive, interim storage facility in Fukushima prefecture and negotiating with 2,360 landowners for the thousands of acres needed to complete it. And that is not even a long-term solution: The government says that after 30 years it will need another site — or sites — to store radioactive waste.

1,573 Nuclear Fuel Rods
The ultimate goal of the cleanup is to cool and, if possible, remove the uranium and plutonium fuel that was inside the three reactors at the time of the disaster.  Hundreds of spent fuel rods are in cooling pools inside the reactors, and the company hopes to have cleared away enough rubble to begin removing them next year. The much bigger challenge will be removing the fuel that was in use in the reactor core at the time of the meltdown.

The condition and location of this molten fuel debris are still largely unknown. In one reactor where a robot was sent in January, much of the melted fuel is believed to have burned through the bottom of the inner reactor vessel and burrowed into the thick concrete foundation of the containment structure.  The plan is to completely seal the containment vessels, fill them with water and use robots to find and remove the molten fuel debris. But the rubble, the lethal levels of radiation and the risk of letting radiation escape make this an exceedingly difficult task.

In January 2017, the robot sent into one of the reactors discovered radiation levels high enough to kill a person in less than a minute. Another had to be abandoned last month after debris blocked its path and radiation disabled it.

Tokyo Electric hopes to begin removing fuel debris from the reactor cores in 2021. The entire effort could take decades. Some say the radioactive material may prove impossible to remove safely and have suggested leaving it and entombing Fukushima under a concrete and steel sarcophagus like the one used at Chernobyl.

But the Japanese government and Tokyo Electric say they are committed to removing all the waste and cleaning the site, estimated at a cost of $188.6 billion.

Excerpts from MOTOKO RICH, Struggling With Japan’s Nuclear Waste, Six Years After Disaster, Mar. 11, 2017

Scorpion Robots at Fukushima

Hopes have been raised for a breakthrough in the decommissioning of the wrecked Fukushima Daiichi nuclear plant after its operator said it may have discovered melted fuel beneath a reactor, almost six years after the plant suffered a triple meltdown.  Tokyo Electric Power (Tepco) said on January 30, 2017 that a remote camera appeared to have found the debris beneath the badly damaged No 2 reactor, where radiation levels remain dangerously high. Locating the fuel is the first step towards removing it.  If Tepco can confirm that the black mass comprises melted fuel, it would represent a significant breakthrough in a recovery effort that has been hit by mishaps, the buildup of huge quantities of contaminated water, and soaring costs….Using a remotely controlled camera attached to the end of a 10.5-metre-long telescopic arm, Tepco technicians located black lumps on wire-mesh grating just below the reactor’s pressure vessel, local media reported.

The company plans to send a scorpion-like robot equipped with cameras, radiation measuring equipment and a temperature gauge into the No 2 reactor containment vessel….Three previous attempts to use robots to locate melted fuel inside the same reactor ended in failure when the devices were rendered useless by radiation.

The delicate, potentially dangerous task of decommissioning the plant has barely begun, however.Japanese media said that plans to remove spent fuel from the No 3 reactor building had been delayed, while decommissioning the entire plant was expected to take at least 40 years.  In December 2016, the government said the estimated cost of decommissioning the plant and decontaminating the surrounding area, as well as paying compensation and storing radioactive waste, had risen to 21.5 trillion yen ($187bn), nearly double an estimate released in 2013.

Excerpts Possible nuclear fuel find raises hopes of Fukushima plant breakthrough, Guardian, Jan. 30, 2017