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Particulate plutonium released from the Fukushima Daiichi meltdowns

 New research strongly suggests that the nano-scale heterogeneity that is common in normal nuclear fuels is still present in the fuel debris that remains inside the Fukushima’s damaged reactors.
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(a)Electron imaging of a CsMP with elemental maps. (b) Synchrotron micro-focus X-ray fluorescence (μXRF) elemental maps. (c) Image of uranium dioxide inclusion in the CsMP. (d) Uranium L3-edge X-ray absorption near-edge structure (XANES) of a discrete point, indicated by the red arrow in (b). The spectrum is plotted alongside U(IV) and U(VI) oxide standards. (e) Discrete-area Pu L3-edge XANES collected from the point indicated by the red arrow.
 
July 14, 2020 University of Helsinki
 
 
Small amounts of plutonium (Pu) were released from the damaged Fukushima Daiichi Nuclear Power Plant (FDNPP) reactors into the environment during the site’s 2011 nuclear disaster. However, the physical, chemical, and isotopic form of the released Pu has remained unknown. Now, recent work has shown that Pu was included inside cesium-rich microparticles (CsMPs) that were emitted from the site.
 
Now, recent work published in the journal Science of the Total Environment has shown that Pu was included inside cesium-rich microparticles (CsMPs) that were emitted from the site. CsMPs are microscopic radioactive particles that formed inside the Fukushima reactors when the melting nuclear fuel interacted with the reactor’s structural concrete. Due to loss of containment in the reactors, the particles were released into the atmosphere; many were then deposited across Japan.
 
Studies have shown that the CsMPs are incredibly radioactive and that they are primarily composed of glass (with silica from the concrete) and radio-cesium (a volatile fission product formed in the reactors). Whilst the environmental impact and distribution of the CsMPs is still an active subject of debate, learning about the chemical composition of the CsMPs has been shown to offer a much-needed insight into the nature and extent of the FDNPP meltdowns.
 
The study published in Science of the Total Environment, involving scientists from Japan, Finland, France, Switzerland, the UK, and USA, was led by Dr. Satoshi Utsunomiya and graduate student Eitaro Kurihara (Department of Chemistry, Kyushu University). The team used a combination of advanced analytical techniques (synchrotron-based micro-X-ray analysis, secondary ion mass spectrometry, and high-resolution transmission electron microscopy) to find and characterize the Pu that was present in the CsMP samples.
 
The researchers initially discovered incredibly small uranium-dioxide inclusions, of less than 10 nanometers in diameter, inside the CsMPs; this indicated possible inclusion of nuclear fuel inside the particles. Detailed analysis then revealed, for the first-time, that Pu-oxide concentrates were associated with the uranium, and that the isotopic composition of the U and Pu matched that calculated for the FDNPP irradiated fuel inventory.
 
Dr Utsunomiya stated “these results strongly suggest that the nano-scale heterogeneity that is common in normal nuclear fuels is still present in the fuel debris that remains inside the site’s damaged reactors. This is important information as it tells us about the extent / severity of the melt-down. Further, this is important information for the eventual decommissioning of the damaged reactors and the long-term management of their wastes.”
 
With regards environmental impact, Dr Utsunomiya states “that as we already know that the CsMPs were distributed over a wide region in Japan (up to 230 km from the FDNPP), small amounts of Pu were likely dispersed in the same way.”
 
Professor Gareth Law, a co-author on the paper from the University of Helsinki, indicated that the team “will continue to characterize and experiment with the CsMPs, in an effort to better understand their long-term behavior and environmental impact. It is clear that CsMPs are an important vector of radioactive contamination from nuclear accidents.”
 
Professor Bernd Grambow, a co-author from Nantes/France, states that “while the Pu released from the damaged reactors is low compared to that of Cs; the investigation provides crucial information for studying the associated health impact.”
 
Professor Rod Ewing at Stanford University emphasized that “the study used an extraordinary array of analytical techniques in order to complete the description of the particles at the atomic-scale. This is the type of information required to describe the mobility of plutonium in the environment.”
 
Utsunomiya concluded “It took a long time to publish results on particulate Pu from Fukushima. I would like to emphasize that this is a great achievement of international collaboration. It’s been almost ten years since the nuclear disaster at Fukushima,” he continued “but research on Fukushima’s environmental impact and its decommissioning are a long way from being over.”
 

July 16, 2020 Posted by | Fukushima 2020 | , , , | Leave a comment

High levels of radioactive material migrating down into soil around Fukushima

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High levels of radioactive cesium remain in the soil near the Fukushima Daiichi nuclear power plant and these radionuclides have migrated at least 5 centimeters down into the ground at several areas since the nuclear accident five years ago, according to preliminary results of a massive sampling project being presented at the JpGU-AGU joint meeting in Chiba, Japan.

In 2016, a team of more than 170 researchers from the Japanese Geoscience Union and the Japan Society of Nuclear and Radiochemical Sciences conducted a large-scale soil sampling project to determine the contamination status and transition process of radioactive cesium five years after a major earthquake and tsunami caused a nuclear accident at the Fukushima Daiichi plant.  

The team collected soil samples at 105 locations up to 40 kilometers (25 miles) northwest of the Fukushima Daiichi nuclear power plant in the “difficult-to-return” zone where entry is prohibited. The project seeks to understand the chemical and physical forms of radionuclides in the soil and their horizontal and vertical distribution.

The Japanese government has monitored the state of radioactive contamination in the area near the plant since the 2011 accident by measuring the air dose rate, but scientists can only determine the actual state of contamination in the soil and its chemical and physical forms by direct soil sampling, said Kazuyuki Kita, a professor at Ibaraki University in Japan, who is one of the leaders of the soil sampling effort.

Understanding the radionuclides’ chemical and physical forms helps scientists understand how long they could stay in the soil and the risk they pose to humans, plants and animals, Kita said. The new information could help in assessing the long-term risk of the radionuclides in the soil, and inform decontamination efforts in heavily contaminated areas, according to Kita, one of several researchers will present the team’s preliminary results at the JpGU-AGU joint meeting next week.

Preliminary results show high levels radioactive cesium are still present in the soil near the plant. The levels of radiation are more than 90 percent, on average, of what was found immediately following the accident, according to Kita.

Most of the radiocesium in the soil was found near the surface, down to about 2 centimeters, immediately following the 2011 accident. Five years later, at several sampling points, one-third to one-half of the radiocesium has migrated deeper into the soil, according to Kita. Preliminary results show the radiocesium moved about 0.3 centimeters per year, on average, deeper into the soil and soil samples show the radiocesium has penetrated at least 5 centimeters into the ground at several areas, according to Kita.

The team plans to analyze samples taken at greater depths to see if the radiocesium has migrated even further, he said.  

Most of the radioactive cesium remains after five years, but some parts of the radioactive cesium went from the surface to deeper soil,” he said.

Knowing how much radioactive contamination has stayed on the surface and how deep it has penetrated into the soil helps estimate the risk of the contaminants and determine how much soil should be removed for decontamination. The preliminary results suggest decontamination efforts should remove at least the top 6 to 8 centimeters of soil, Kita said.  

The preliminary data also show there are insoluble particles with very high levels of radioactivity on the surface of the soil. Debris from the explosion fused with radiocesium to form small glass particles a few microns to 100 microns in diameter that remain on the ground, according to Kita. The team is currently trying to determine how many of these radiocesium glass particles exist in areas near the nuclear plant, he said.

We are afraid that if such high radioactive balls remain on the surface, that could be a risk for the environment,” Kita said. “If the radioactivity goes deep into the soil, the risk for people in the area decreases but we are afraid the high radioactive balls remain on the surface.”

Nanci Bompey is the manager of AGU’s public information office. This research is being presented Thursday, May 25 at the JpGU-AGU joint meeting in Chiba, Japan. 

http://blogs.agu.org/geospace/2017/05/19/high-levels-radioactive-material-migrating-soil-around-fukushima/

May 22, 2017 Posted by | Fukushima 2017 | , , , | Leave a comment

Testimony from Disaster

MINES Paris Tech is the leading institution, at the heart of the french nuclear lobby, a state within the State.

Crisis management students in France are hoping to learn from a first-hand account of the Fukushima nuclear disaster.

Franck Guarnieri, a researcher in risk and crisis management at one of France’s leading institutions, MINES ParisTech, has been studying the accident.

Guarnieri and his team have interviewed nearly 30 government officials, experts, and employees at Tokyo Electric Power Company who were active during the aftermath of the 2011 disaster.

He is particularly interested in the actions of the late Masao Yoshida, the plant manager at the time.

Some months after the disaster, Yoshida told the government about what he did. The transcript, titled the Yoshida Testimony, was released in 2014.

When Guarnieri saw it, he decided to publish it in French.

The job of rendering Yoshida’s entire 28-hour testimony into French was recently completed. The translation takes up 3 volumes, 2 of which are now in print.

“This is the first time the testimony of a plant manager has been made public. In the Three Mile Island and Chernobyl accidents, the plant managers did not give testimonies,” says Guarnieri.

Rather than simply focusing on the events and facts of the disaster, Guarnieri and his team are especially interested in Yoshida’s emotional and psychological state, as the person in charge of the accident response.

These are some of his statements:

“There was no manual for this situation. To put it bluntly, I realized I’d have to rely on my intuition and judgment.”

“If we had stopped injecting water into the reactors it would have been catastrophic, so I decided to continue.”

Guarnieri’s team says those words indicate that Yoshida had to make decisions based on information that was potentially incorrect. They say the Yoshida Testimony is quite different from other official accounts, which tend to include little regarding the human element.

France now operates more than 50 nuclear power plants, which supply 70% of the nation’s electricity. To date, there haven’t been any major nuclear accidents.

But Guarnieri believes the officials at these French nuclear power plants need to read Yoshida’s testimony.

Recently, he met with Jean-Marc Cavedon, the director of the French Alternative Energies and Atomic Energy Commission on the outskirts of Paris.

Guarnieri stressed the unique importance of the Yoshida document, and urged them to devise safety measures for extreme situations.

“There will be no progress in risk management unless we learn from other people’s experience and improve as human beings,” says Cavedon.

“Nuclear power plants need to improve their risk management, by facing up to the disastrous events in Fukushima,” says Guarnieri.

Two years after the nuclear accident, Yoshida died of cancer.

Guarnieri is now intent on spreading the lessons of Yoshida’s testimony, to make sure such a tragedy never happens again.

https://www3.nhk.or.jp/nhkworld/en/news/editors/5/20170403/

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April 4, 2017 Posted by | Fukushima 2017 | , , , | Leave a comment

Study: S. Korean nuclear disaster would hit Japan the hardest

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The projected spread of radioactive cesium-137 from a disaster at the No. 3 reactor’s spent fuel pool of the Kori nuclear plant in Busan, South Korea (Provided by Kang Jung-min)

A serious nuclear accident in South Korea could force the evacuation of more than 28 million people in Japan, compared with around 24 million in the home country of the disaster.

Japan would also be hit harder by radioactive fallout than South Korea in such a disaster, particularly if it occurred in winter, when strong westerly winds would blow radioactive substances across the Sea of Japan, according to a simulation by the Natural Resources Defense Council, a Washington-based think tank.

The simulation, based on a scenario of an unfolding crisis at the Kori nuclear power plant in Busan, South Korea, was led by Kang Jung-min, a South Korean senior researcher of nuclear physics, and his colleagues.

At events in Japan and South Korea, Kang, 51, has repeatedly warned about East Asia’s vulnerability to a severe nuclear accident, saying the region shares the “same destiny” regardless of the location of such a disaster.

The Kori nuclear complex is home to seven of the country’s 25 commercial reactors, making it one of the largest in South Korea. Its oldest reactor–and the first in the country–went online in 1978.

Spent nuclear fuel at the Kori plant is cooled in on-site storage pools next to reactors.

But the operator of the plant has ended up storing spent fuel in more cramped conditions than in the past because waste keeps accumulating from the many years of operations.

An estimated 818 tons of spent fuel was being stored at the pool of the Kori No. 3 reactor as of the end of 2015, the most at any reactor in the country.

That is because the No. 3 pool has also been holding spent fuel from the No. 1 and No. 2 reactors since their fuel pools became too crowded.

Storing spent fuel in such a manner greatly increases the risk of a nuclear accident, Kang warned.

Kang’s team simulated the series of likely events that would follow if the No. 3 reactor lost power in a natural disaster or an act of terrorism.

With no power, the spent fuel at the No. 3 reactor could not be cooled. The cooling water would evaporate, exposing the fuel rods to air, generating intensive heat and causing a fire.

Hydrogen gas would then fill up the fuel storage building, leading to an explosion that would result in the release of a large amount of vaporized cesium-137 from the spent fuel.

Assuming that the catastrophe occurred on Jan. 1, 2015, the researchers determined how highly radioactive cesium-137 would spread and fall to the ground based on the actual weather conditions over the following week, as well as the direction and velocity of winds.

To gauge the size of the area and population that would be forced to evacuate in such a disaster, the team took into account recommendations by the International Commission on Radiological Protection, a private entity, and other organizations.

The results showed that up to 67,000 square kilometers of land in Japan–or much of the western part of the country–would fall under the evacuation zone, displacing a maximum of 28.3 million people.

In South Korea, up to 54,000 square kilometers would need to be vacated, affecting up to 24.3 million people.

The simulation also found that 18.4 million Japanese and 19 million Koreans would remain displaced for even after 30 years, the half-life of cesium-137, in a worst-case scenario.

Radioactive materials from South Korea would also pollute North Korea and China, according to the study.

Nineteen reactors in South Korea are located in the coastal area facing the Sea of Japan, including those at the Kori nuclear power plant.

Kang said the public should be alerted to the dangers of highly toxic spent fuel, an inevitable byproduct of nuclear power generation.

One ton of spent fuel contains 100,000 curies of cesium-137, meaning that 20 tons of spent fuel would be enough to match the estimated 2 million curies of cesium-137 released in the 1986 Chernobyl disaster.

An average-size light-water reactor produces about 20 tons of spent fuel in one year of operation.

East Asia is home to one of the world’s largest congestions of nuclear facilities, Kang said.

Japan, China and South Korea, which have all promoted nuclear energy as state policy for decades, together host about 100 commercial reactors.

A number of nuclear-related facilities are also concentrated in North Korea, particularly in Yongbyon, north of Pyongyang.

If a severe accident were to occur in China, the pollution would inevitably spill over to South Korea and then to Japan.

That is why people should take serious interest in not just their own country’s nuclear issues, but also in neighboring countries,” Kang said. “Japan, China and South Korea should cooperate with each other to ensure the safety and security of spent fuel and nuclear facilities.”

He said the risks of a fire would be reduced if spent fuel were placed at greater intervals in storage pools.

Ideally, spent fuel should be moved to sealed dry casks and cooled with air after it is cooled in a pool for about five years,” he said.

http://www.asahi.com/ajw/articles/AJ201703300001.html

March 31, 2017 Posted by | South Korea | , , | Leave a comment

Cows in Fukushima Radiation Zone Find New Purpose: Science

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NAMIE, Japan — In an abandoned Japanese village, cows grazing in lush green plains begin to gather when they hear the familiar rumble of the ranch owner’s mini-pickup. This isn’t feeding time, though.

Instead, the animals are about to be measured for how they’re affected by living in radiation — radioactivity that is 15 times the safe benchmark. For these cows’ pasture sits near Fukushima, a name now synonymous with nuclear disaster.

The area was once a haven for agriculture with more than 3,500 cattle and other livestock. Ranchers who refused a government order to kill their cows continue to feed and tend about 200 of them. The herds won’t be used as food; now science is their mission.

Researchers visit every three months to test livestock living within a 20-kilometer (12-mile) radius of the Fukushima plant, where three reactors had core meltdowns after the facility was swamped by a tsunami in 2011. It is the first-ever study of the impact on large mammals of extended exposure to low-level radiation.

The ranchers are breeders, as opposed to those raising cattle to sell for beef, and tend to be attached to their animals. They treat them almost as if they were children, even giving them names. The research gives them a reason to keep their beloved cows alive, and to hope that someday ranching might safely return here.

Under a drizzling rain, doctors and volunteers wearing blue Tyvek protective suits draw the cows into a handmade pen of aluminum pipes. Five to six cows line up in the cage and are tied with a rope around their head and through their nose ring for solid support, so they won’t be hurt when the needle draws blood from their neck.

The gentle beasts moo from discomfort. The doctors work swiftly, drawing blood, collecting urine and checking for lumps or swollen lymph nodes. The check-up takes five minutes or less per cow.

Namie, 11 kilometers (7 miles) northwest of the plant, is a ghost town with no prospect of being habitable for years. But 57-year-old Fumikazu Watanabe comes every day to a ranch to feed 30 to 40 cows owned by seven farmers.

“What is the meaning of slaughtering the cows?” Watanabe said at a worn-out barn where healthy cows used to spend the night tending to their calves. The bones of animals that have died litter the ground outside.

“Keeping the cows alive for research purposes means that we can pass on the study to our next generation instead of simply leaving a negative legacy,” he said.

The research team, made up of veterinary and radiation experts from Iwate University, Tokai University and Kitasato University, was established a year after the meltdowns. They formed a nonprofit group called Society for Animal Refugee & Environment post Nuclear Disaster. Members volunteer to take the blood and urine samples and test them.

In 2012, the Japanese government ordered all livestock in the restricted area killed for fear that the breeding cows would continue to reproduce, and that cows exposed to radiation would have no sale value.

Keiji Okada, associate professor of veterinary medicine and agriculture at Iwate University, said the government considered it pointless to study the animals, since it couldn’t determine how much radiation they were exposed to immediately after the disaster.

Okada disagrees. He said the data will help researchers learn whether farmers can eventually work in affected zones.

“There are no precedent studies of animals being exposed to low-dose radiation, and we have no idea what results we are going to get,” he said. “That is exactly why it needs to be monitored.”

So far, the animals’ internal organs and reproductive functions have shown no significant abnormality particularly linked to radiation exposure, Okada said, but it’s too early to draw conclusions about thyroid cancer and leukemia.

Radiation could cause leukemia, but so could mosquitoes, which have infected cattle around the world with bovine leukemia virus.

“Even if we detect leukemia in the cows, we don’t know whether it’s caused by radiation or if it’s a bovine leukemia from a virus,” Okada said. “It is this year’s objective to be able to differentiate the two.”

Many cows have died during the study period, but food shortages have played a role, making it all the more difficult the doctors to determine causes. The dead cows are dissected and the radiation dosage in their organs is measured.

Is radiation killing the cows, or making them sick? Okada said the research team is working toward reaching a conclusion by March. The team worries that the study results could spark overly broad fears that the region will no longer be habitable or fit for agriculture.

Ultimately, Okada said, the team believes that further monitoring of the animals will show under what conditions it is safe to raise livestock exposed to low-level radiation, and how best to deal with such a leak should it happen again.

Yukio Yamamoto, owner of the large Yamamoto Ranch surrounded by a mountain, a river and a vast plain, travels three hours roundtrip from his temporary home to feed his remaining cows.

Yamamoto initially followed government orders to kill his cattle. He watched a mother cow being killed while a calf was still suckling on its milk, and then the calf following that.

“The cows are my family. How do I dare kill them?” Yamamoto said. “If there is a God, I’m sure some day we would be rewarded for the sacrifice we are making.”

He hopes one day to see his barn come to life again, filled with a hundred cows and calves cared for by his children and grandchildren.

http://www.nytimes.com/aponline/2016/09/22/world/asia/ap-as-japan-fukushima-cows.html?_r=0

September 23, 2016 Posted by | Fukushima 2016 | , , , | 3 Comments