New research reveals further insight into Fukushima Daiichi material release

New paper reveals further insight into Fukushima Daiichi material release through analogues to volcanic processes.

A new paper, published today in Nature Scientific Reports, provides further insights into the particulate material released into the environment following the accident at Japan’s Fukushima Daiichi Nuclear Power Plant (FDNPP) in 2011.

This new research builds upon that performed by the multi-national research team reported in the 2019 Nature Communications publication that used cutting-edge analytical techniques to identify microscopic inclusions of reactor-derived fuel particulates contained within the silicate-based sub-millimetre sized material. The work helped to determine the likely chain of events that occurred as well as the probable reactor conditions at the time of the accident that resulted in the production of the highly porous fallout particle released from reactor Unit 1 of the FDNNP.

Schematic chronology of reactor Unit 1 (‘Type B’) and Unit 3 (‘Type C’) particulate formation chronologies, alongside each suites resultant structural (internal and external) characteristics, and as observed as part of this study, the invoked conditions of formation.                                                      

Since the accident, numerous works have studied the microscopic material released from reactor Unit 2 (‘Type A’) and Unit 1 (‘Type B’), however, this work studied a new type of fallout particulate invoked to have been derived from reactor Unit 3 which had been recently isolated by the Japanese collaborators from sediments within the contaminated land surrounding the site.

Through the use of both laboratory and national facilities (principally Diamond Light Source), by applying an understanding of volcanic processes, the authors were able to define a reactor-specific chronology for Unit 3; supporting those formerly derived for Unit 1 (the other reactor on the FDNPP to suffer a large hydrogen explosion). The work has crucial implications for underpinning the methodologies of how planned decommissioning activities at each of the reactor Units are to be imminently undertaken by the plant’s operator, TEPCO.

In this work, the authors attributed the near-spherical shape of Unit 1 ejecta and their internal voids to their existing sufficient time for surface tension to round these objects before the hot (and consequently relatively low viscosity) silicate melt cooled to form glass. In contrast, the more complex internal form associated with the sub-mm particulates invoked to originate from Unit 3 (a newly identified ‘Type C’) suggested a lower peak temperature, over a longer duration.

Using expertise on volcanic analogues from the University of Bristol’s School of Earth Sciences, the team considered the structural form of this material and how it consequently related to its environmental particulate stability and the bulk removal of residual materials from the damaged reactors. The team concluded in the work that the brittle and angular Unit 3 (or ‘Type C’) particulate are more susceptible to further fragmentation and particulate generation hazard than the round, higher-strength, more homogenous Unit 1 (‘Type B’) material.

Credit: courtesy of the U.S. Geological Survey

 

Dr Alison Rust, Reader in Physical Volcanology at the University of Bristol, explained:

“I started comparing images of bubble-bearing glassy particles from the 2011 Fukushima disaster to what I’ve seen in glassy volcanic particles. The power of this cross-disciplinary approach became clear when I reported how the shapes of the particles and their internal bubbles indicated that some of the particles started hotter - this turned out to be consistent with independent evidence.”

This research highlights Bristol’s role in the Met Office Academic Partnership (MOAP), which brings together the UK’s leading experts on hazardous events, extreme weather and environmental protection.

 

International collaboration

Japanese collaborators are also involved in this research, from the Japan Atomic Energy Agency (JAEA) Collaborative Laboratories for Advanced Decommissioning Science (CLADS) facility, plus the Universities of Tsukuba and Osaka.

Professor Atsushi Shinohara from Osaka University commented: “It was great to work on this collaborative project involving experts from the UK to investigate this new form of radiative particulate derived from the Fukushima Daiichi Nuclear Power Plant. The facilities and expertise at the University of Bristol are ideally suited to this scientific study”.

Paper details

‘Structural and compositional characteristics of Fukushima release particulate material from Units 1 and 3 elucidates release mechanisms, accident chronology and future decommissioning strategy’ by P.G. Martin et al in Nature Scientific Reports

View paper

Authors: Peter Martin, Chris Jones, Stuart Bartlett, Konstantin Ignatyev, Dave Megson-Smith, Yukihiko Satou, Silvia Cipiccia, Darren Batey, Christoph Rau, Keisuke Sueki, Tatsuya Ishii, Junya Igarashi, Kazuhiko Ninomiya, Atsushi Shinohara, Alison Rust, Tom Scott

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