On a Friday afternoon in the spring of 2011, the largest earthquake in Japan’s recorded history triggered a tsunami that crashed through seawalls, flattened coastal communities and pummeled the Fukushima Daiichi nuclear power plant.

More than 19,000 people died and tens of thousands more fled as radiation belched from the world’s worst nuclear accident since Chernobyl.

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On March 11, 2011, Koide Hiroaki was in his laboratory in Kyoto, Japan. It was a gray, wet afternoon, and the 61-year-old nuclear engineer was hard at work when the earthquake hit. Fifteen miles beneath the surface of the sea, one tectonic plate rumbled beneath another. A slippery clay layer helped the great pieces of crust slide, releasing centuries of stress. The seabed rose up 16 stories, and slipped sideways 165 feet.

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Abstract

In the absence of a federal geologic repository or consolidated, interim storage in the United States, commercial spent fuel will remain stranded at some 75 sites across the country. Currently, these include 18 “orphaned sites” where spent fuel has been left at decommissioned reactor sites. In this context, local communities living close to decommissioned nuclear power plants are increasingly concerned about this legacy of nuclear power production and are seeking alternative strategies to move the spent fuel away from those sites. In this paper, we present a framework and method for the socio-technical multi-criteria evaluation (STMCE) of spent fuel management strategies. The STMCE approach consists of (i) a multi-criteria evaluation that provides an ordinal ranking of alternatives based on a list of criterion measurements; and (ii) a social impact analysis that provides an outranking of options based on the assessment of their impact on concerned social actors. STMCE can handle quantitative, qualitative or both types of information. It can also integrate stochastic uncertainty on criteria measurements and fuzzy uncertainty on assessments of social impacts. We conducted an application of the STMCE method using data from the decommissioned San Onofre Nuclear Generating Station (SONGS) in California. This example intends to facilitate the preparation of stakeholder engagement activities on spent fuel management using the STMCE approach. The STMCE method provides an effective way to compare spent fuel management strategies and support the search for compromise solutions. We conclude by discussing the potential impact that such an approach could have on the management of commercial spent fuel in the United States.

Read the rest at Science of The Total Environment

The Fukushima Daiichi Nuclear Power Plant released particles containing radioactive cesium during the 2011 nuclear disaster. New research published in Science of the Total Environment shows that some particles were larger and contained much higher levels of activity than was previously known.

“This paper is part of a series of publications that provide a detailed picture of the material emitted during the Fukushima Daiichi reactor meltdowns,” said CISAC Co-Director Rod Ewing, the Frank Stanton Professor in Nuclear Security who collaborated with scholars from Japan, Finland, France, and the United Kingdom on this research.

“This is exactly the type of work required for remediation and an understanding of long-term health effects,” Ewing said.

The larger particles were found during a survey of surface soils 3.9 km north-northwest of reactor unit 1. Two of the 31 Cs-particles collected during the sampling campaign have given the highest ever particle-associated ^134+137Cs activities for materials emitted from the Fukushima Daiichi Nuclear Power Plant (FDNPP).

The researchers used a combination of advanced analytical techniques (synchrotron-based nano-focus X-ray analysis, secondary ion mass spectrometry, and high-resolution transmission electron microscopy) to fully characterize the particles.

One particle, which was found to be an aggregate of smaller, “flakey” silicate nanoparticles, with a glass-like structure likely came from reactor building materials, which were damaged during the Unit 1 hydrogen explosion; then, as the particle formed, it likely adsorbed Cs that had had been volatized from the hot reactor fuel. The composition of the surface embedded micro-particles likely reflects the composition of airborne particles within the reactor building at the moment of the hydrogen explosion, thus providing a forensic window into the events of March 11, 2011.

Dr. Satoshi Utsunomiya at the University of Kyushu led the study. “The new particles from regions close to the damaged reactor provide valuable forensic clues,” he said. “They give snap-shots of the atmospheric conditions in the reactor building at the time of the hydrogen explosion and of the physio-chemical phenomena that occurred during reactor meltdown.”

“While ten years have passed since the accident, the importance of scientific insights has never been more critical,” Utsunomiya said. “Clean-up and repatriation of residents continues and a thorough understanding of the contamination forms and their distribution is important for risk assessment and public trust.”

Gareth Law at the University of Helsinki who worked on the study, said that ongoing clean-up and decommissioning efforts at the site face difficult challenges, particularly the removal and safe management of accident debris with very high levels of radioactivity. “Prior knowledge of debris composition can help inform safe management approaches,” he said.

Given the high radioactivity associated with the new particles, the project team was also interested in understanding their potential health and dose impacts. “Owing to their large size, the health effects of the new particles are likely limited to external radiation hazards during static contact with skin,” Utsunomiya said. “As such, despite the very high level of activity, we expect that the particles would have negligible health impacts for humans as they would not easily adhere to the skin. However, we do need to consider possible effects on the other living creatures such as filter feeders in habitats surrounding Fukushima Daiichi. Even though ten years have already passed, the half-life of ¹³⁷Cs is ~30 years. So, the activity in the newly found highly radioactive particles has not yet decayed significantly. As such, they will remain in the environment for many decades to come, and this type of particle could occasionally still be found in radiation hot spots.”

Bernd Grambow, Chair of the Nuclear Waste Management at IMT Atlantique, said, “The present work, using cutting-edge analytical tools, gives only a very small insight in the very large diversity of particles released during the nuclear accident, much more work is necessary to get a realistic picture of the highly heterogeneous environmental and health impact.”

In a series of Bulletin articles in June 2019, young American and Russian professionals examined the future of global nuclear power. They made their case for nuclear power, driven by their concern about global climate change, and also identified the principal challenges that must be overcome. Safety of nuclear power was judged to be the major risk, followed by the risks of nuclear proliferation, security, and nuclear waste disposal, and the economic challenges to increased use of nuclear power, especially in the United States.

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Believe it or not, there is an issue on which Donald Trump and Joe Biden agree: Both have announced their opposition to building an underground repository to permanently store nuclear waste at Yucca Mountain in Nevada. With the presidential candidates on record, it is time for everyone else to accept that Yucca Mountain is finally off the table, and for the United States to begin to seriously consider realistic alternatives for safely managing the more than 80,000 tons of spent nuclear fuel currently sitting at 72 operating and shut-down commercial nuclear reactor sites across the country.

Read the rest at Bulletin of Atomic Scientists

On the quiet Friday afternoon of March 11, 2011, Natsuo* was working in Fukushima, the capital city of Fukushima prefecture. At 2:46 p.m., a devastating earthquake of 9.0 magnitude hit the Pacific coast of Japan, where the prefecture of Fukushima is situated. Natsuo recalled to me the sheer power of this earthquake: “The whole office shook like hell, everything began to fall from the walls. I thought to myself ‘That’s it … I’m going to die!’”

Natsuo quickly returned to her hometown of Koriyama City, unaware that the earthquake had triggered a massive tsunami, which inundated an important part of the prefectural shoreline and ultimately claimed the lives of nearly 20,000 people. On top of the initial devastation, the tsunami severely damaged the Fukushima Dai’ichi Nuclear Power Plant, in Ōkuma, Fukushima, located on the east coast of Fukushima prefecture. She later learned on TV that something “seemed wrong” with the nuclear power plant. “During that time,” she said, “I tried to get as much information as I could, but the media weren’t being clear on the situation.”

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Nearly ten years after meltdown at the Fukushima Daiichi Nuclear Power Plant caused a nuclear disaster, researchers have uncovered important new information about the extent and severity of the meltdown and the distribution patterns of the plutonium that have broad implications for understanding the mobility of plutonium during a nuclear accident.

According to a paper published July 8 in Science of the Total Environment, microscopic particles emitted during the disaster contained not only high concentrations of radioactive cesium, as previously reported, but also the toxic metal plutonium. These microscopic radioactive particles formed inside the Fukushima reactors when the melting nuclear fuel interacted with the reactor’s structural concrete.

“The study used an extraordinary array of analytical techniques in order to complete the description of the particles at the atomic-scale,” said Rod Ewing, co-director of the Center for International Security and Cooperation (CISAC) at Stanford University.

Ewing collaborated with researchers from Kyushu University, University of Tsukuba, Tokyo Institute of Technology, National Institute of Polar Research, University of Helsinki, Paul Scherrer Institute, Diamond Light Source and SUBATECH (IMT Atlantique, CNRS, University of Nantes).

The researchers found that, due to loss of containment in the reactors, the particles were released into the atmosphere and many were then deposited many kilometers from the reactor sites. Studies have shown that the cesium-rich microparticles, or CsMPs, are highly radioactive and primarily composed of glass (with silica from concrete) and radio-cesium (a volatile fission product formed in the reactors). But the environmental impact and their distribution is still an active subject of research and debate. The new work offers a much-needed insight into the Fukushima Daiichi Nuclear Power Plant, (FDNPP) meltdowns.

Geochemist Satoshi Utsunomiya and graduate student Eitaro Kurihara of Kyushu University led the team that used a combination of advanced analytical techniques, including synchrotron-based micro-X-ray analysis, secondary ion mass spectrometry, and high-resolution transmission electron microscopy, to find and characterize the plutonium 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 revealed, for the first-time, that plutonium-oxide concentrates were associated with the uranium, and that the isotopic composition of the uranium and plutonium matched that calculated for the FDNPP irradiated fuel inventory.

“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,” said Utsunomiya. “This is important information as it tells us about the extent [and] severity of the meltdown. Further, this is important information for the eventual decommissioning of the damaged reactors and the long-term management of their wastes.”

With regards to environmental impact, Utsunomiya said, “as we already know that the CsMPs were distributed over a wide region in Japan, small amounts of plutonium were likely dispersed in the same way.”

Gareth T. W. Law, a co-author on the paper from the University of Helsinki, said the team “will continue to experiment with the CsMPs, in an effort to better understand their long-term behavior and environmental impact. It is now clear that CsMPs are an important vector of radioactive contamination from nuclear accidents.”

Bernd Grambow, a coauthor from Nantes/France, said, “While the plutonium released from the damaged reactors is low compared to that of cesium; the investigation provides crucial information for studying the associated health impact.”

Utsunomiya emphasized that this is a great achievement of international collaboration. “It’s been almost ten years since the nuclear disaster at Fukushima,” he said, “but research on Fukushima’s environmental impact and its decommissioning are a long way from being over.”

Ewing is also the Frank Stanton Professor in Nuclear Security, a Senior Fellow of the Precourt Institute for Energy, Senior Fellow at the Freeman Spoglie Institute for International Studies and. Professor of Geological Sciences in Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth). Co-authors of the paper include Eitaro Kurihara, Masato Takehara, Mizuki Suetake, Ryohei Ikehara, Tatsuki Komiya, Kazuya Morooka, Ryu Takami, Shinya Yamasaki, Toshihiko Ohnuki, Kenji Horie, Mami Takehara, Gareth T. W. Law, William Bower, J. Frederick. W. Mosselmans, Peter Warnicke, Bernd Grambow, Rodney C. Ewing, and Satoshi Utsunomiya

Integration of analytical techniques was accomplished through an international network that included Kyushu University, University of Tsukuba, Tokyo Institute of Technology, National Institute of Polar Research, University of Helsinki, Paul Scherrer Institute, Diamond Light Source, SUBATECH (IMT Atlantique, CNRS, University of Nantes) and Stanford University.  

This article was adapted from a press release produced by Kyushu University.

Read Particulate plutonium released from the Fukushima Daiichi meltdowns

Media contacts:

Josie Garthwaite

School of Earth, Energy & Environmental Sciences

(650)497-0949, josieg@stanford.edu

Jody Berger

Center for International Security and Cooperation

(303)748-9657, jody.berger@stanford.edu

In the budding days of the COVID-19 pandemic, President Trump idled his days away, launching random tweets about unrelated issues. One such issue was nuclear waste disposal: “Nevada, I hear you on Yucca Mountain…my Administration is committed to exploring innovative approaches – I’m confident we can get it done!”

After this particular proclamation, the nuclear expert community was left scratching its collective head. Does the president support Yucca Mountain as an eventual nuclear waste repository, or does he not? And, more puzzling, what “innovative approaches” for nuclear waste does he have in mind? Maybe he was thinking about the “waste eating” advanced reactors promoted by the US Energy Department and the private sector; maybe he was thinking about reprocessing spent nuclear fuel; or maybe he was thinking about deep boreholes for permanent waste storage.

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