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Journal Articles

Assessment of the potential for criticality in the far field of a used nuclear fuel repository

Atz, M.*; Salazar, A.*; Hirano, Fumio; Fratoni, M.*; Ahn, J.*

Annals of Nuclear Energy, 124, p.28 - 38, 2019/02

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

The likelihood for criticality in the far field of a repository was evaluated for direct disposal of commercial light water reactor used nuclear fuel. Two models were used in combination for this evaluation: (1) a neutronics model to estimate the minimum critical masses of spherical, water-saturated depositions of fuel material; (2) a transport model to simulate the dissolution of fuel material from multiple canisters and the subsequent transport of the solutes through host rock to a single accumulation location. The results suggest that accumulation of a critical mass is possible under conservative conditions but that these conditions are unlikely to occur, especially in the vicinity of a carefully-arranged repository.

Journal Articles

Hydrogen-based metabolism as an ancestral trait in lineages sibling to the Cyanobacteria

Carnevali, P. B. M.*; Schulz, F.*; Castelle, C. J.*; Kantor, R. S.*; Shih, P. M.*; Sharon, I.*; Santini, J.*; Olm, M. R.*; Amano, Yuki; Thomas, B. C.*; et al.

Nature Communications (Internet), 10, p.463_1 - 463_15, 2019/01

 Times Cited Count:3 Percentile:15.2(Multidisciplinary Sciences)

Journal Articles

Radiocesium interaction with clay minerals; Theory and simulation advances Post-Fukushima

Okumura, Masahiko; Kerisit, S.*; Bourg, I. C.*; Lammers, L. N.*; Ikeda, Takashi*; Sassi, M.*; Rosso, K. M.*; Machida, Masahiko

Journal of Environmental Radioactivity, 189, p.135 - 145, 2018/09

 Times Cited Count:6 Percentile:25.51(Environmental Sciences)

no abstracts in English

Journal Articles

Uncertainty analysis of far-field precipitation from used nuclear fuel

Salazar, A.*; Fratoni, M.*; Ahn, J.*; Hirano, Fumio

Proceedings of 2017 International High-Level Radioactive Waste Management Conference (IHLRWM 2017) (CD-ROM), p.600 - 607, 2017/04

Journal Articles

Material composition effects on far-field deposition minimum critical mass

Atz, M.*; Liu, X.*; Fratoni, M.*; Ahn, J.*; Hirano, Fumio

Proceedings of 2017 International High-Level Radioactive Waste Management Conference (IHLRWM 2017) (CD-ROM), p.608 - 614, 2017/04

Journal Articles

Effects of random geometry on post-closure repository criticality safety

Liu, X.*; Fratoni, M.*; Ahn, J.*; Hirano, Fumio

Proceedings of 2017 International High-Level Radioactive Waste Management Conference (IHLRWM 2017) (CD-ROM), p.595 - 599, 2017/04

Journal Articles

Potential for microbial H$$_{2}$$ and metal transformations associated with novel bacteria and archaea in deep terrestrial subsurface sediments

Hernsdorf, A. W.*; Amano, Yuki; Miyakawa, Kazuya; Ise, Kotaro; Suzuki, Yohei*; Anantharaman, K.*; Probst, A. J.*; Burstein, David*; Thomas, B. C.*; Banfield, J. F.*

ISME Journal, 11, p.1915 - 1929, 2017/03

AA2016-0002.pdf:2.21MB

 Times Cited Count:26 Percentile:2.76(Ecology)

To evaluate the potential for interactions between microbial communities and disposal systems, we explored the structure and metabolic function of a sediment-hosted subsurface ecosystem associated with Horonobe Underground Research Center, Hokkaido, Japan. Overall, the ecosystem is enriched in organisms from diverse lineages and many are from phyla that lack isolated representatives. The majority of organisms can metabolize H$$_{2}$$, often via oxidative [NiFe] hydrogenases or electron-bifurcating [FeFe] hydrogenases that enable ferredoxin-based pathways, including the ion motive Rnf complex. Many organisms implicated in H$$_{2}$$ metabolism are also predicted to catalyze carbon, nitrogen, iron, and sulfur transformations. Notably, iron-based metabolism was predicted in a bacterial lineage where this function has not been predicted previously and in an ANME-2d archaeaon that is implicated in methane oxidation. We infer an ecological model that links microorganisms to sediment-derived resources and predict potential impacts of microbial activity on H$$_{2}$$ accumulation and radionuclide migration.

Journal Articles

A New view of the tree of life

Hug, L. A.*; Baker, B. J.*; Anantharaman, K.*; Brown, C. T.*; Probst, A. J.*; Castelle, C. J.*; Butterfield, C. N.*; Hernsdorf, A. W.*; Amano, Yuki; Ise, Kotaro; et al.

Nature Microbiology (Internet), 1(5), p.16048_1 - 16048_6, 2016/05

 Times Cited Count:473 Percentile:0.02(Microbiology)

The tree of life is one of the most important organizing principles in biology. Gene surveys suggest the existence of an enormous number of branches, but even an approximation of the full scale of The Tree has remained elusive. Here, we use newly available information from genomes of uncultivated organisms, along with other published sequences, to present a new version of the Tree of life, with Bacteria, Archaea and Eukaryotes included. The depiction is both a global overview and a snapshot of the diversity within each major lineage. The results imply the predominance of bacterial diversification and underline the importance of organisms lacking isolated representatives, with substantial evolution concentrated in a major radiation of such organisms.

Journal Articles

Conditions for criticality by uranium deposition in water-saturated geological formations

Liu, X.*; Ahn, J.*; Hirano, Fumio

Journal of Nuclear Science and Technology, 52(3), p.416 - 425, 2015/03

 Times Cited Count:1 Percentile:83.34(Nuclear Science & Technology)

Journal Articles

Repository criticality analysis for damaged fuels; Geometry effect in the modeling of uranium and plutonium deposition in geological formations

Liu, X.*; Ahn, J.*; Hirano, Fumio

Proceedings of 14th International High-Level Radioactive Waste Management Conference (IHLRWMC 2013) (CD-ROM), p.527 - 534, 2013/04

The present study focuses on the criticality safety of geological disposal of molten fuel. The influences of different geometries in the MCNP models for the simulation of heavy metal precipitates in geological formations are discussed. Bounding calculations for criticality based on the molten fuel in Fukushima Daiichi reactors were made by optimization in a large parameter space. Some critical combinations are observed in the numerical results, and in the iron rich rock, the risk of criticality is significantly reduced.

Journal Articles

Development of geologic repository models for design and decision making

Murakami, Haruko*; Ahn, J.*

Proceedings of 16th Pacific Basin Nuclear Conference (PBNC-16) (CD-ROM), 6 Pages, 2008/10

JAEA Reports

Effective application of partitioning and transmutation technologies to geologic disposal

Ikegami, Tetsuo; Ahn, J.*

JAEA-Research 2006-045, 17 Pages, 2006/07

JAEA-Research-2006-045.pdf:1.55MB

Environmental Impact, which is a newly developed measure in stead of the conventional radio-toxicity, has been evaluated for both the PWR cycle and the FBR cycle in order to clarify what kind of radio-nuclides and how much level of partitioning and transmutation are desirable. Bounding analysis for uncertainty of parameters relevant to radionuclide transport in a repository has also been performed. The evaluated results imply that the targets of partitioning and transmutation can be set; (1)In the case of PWR cycle, the release rate of $$^{237}$$Np and $$^{243}$$Am should be controlled under 1 %, in addition to the conventionally assumed release rate of 0.604 % for U and 0.297 % for Pu. (2)In the case of FBR cycle, recovery rate of 99.9 % for all actinide nuclides is appropriate.

Oral presentation

Unconventional critical scaling in uranium ferromagnetic superconductors UGe$$_2$$ and URhGe

Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma*; Yamamoto, Etsuji; Fisk, Z.

no journal, , 

We study the critical phenomena associated with ferromagnetic transitions in the uranium ferromagnetic superconductors UGe$$_2$$ and URhGe. The critical phenomena were found to be of the unconventional type. We will discuss its origin.

Oral presentation

Molecular modeling of adsorption sites in micaceous clay minerals

Okumura, Masahiko; Nakamura, Hiroki; Machida, Masahiko

no journal, , 

no abstracts in English

Oral presentation

Sulfur and hydrogen metabolism linked to CO$$_{2}$$ fixation by abundant Nitrospirae in the deep subsurface

Amano, Yuki; Anantharaman, K.*; Tomas, B. C.*; Olm, M.*; Burstein, David*; Castelle, C. J.*; Beppu, Hikari*; Miyakawa, Kazuya; Iwatsuki, Teruki; Suzuki, Yohei*; et al.

no journal, , 

Oral presentation

Vast metabolic and phylogenetic diversity shared across deep subsurface environments

Amano, Yuki; Diamond, S.*; Lavy, A.*; Anantharaman, K.*; Miyakawa, Kazuya; Iwatsuki, Teruki; Beppu, Hikari*; Suzuki, Yohei*; Thomas, B. C.*; Banfield, J. F.*

no journal, , 

Oral presentation

Existence and the role of subsurface biofilm in the deep sedimentary rock environment of the Horonobe area, Hokkaido, Japan

Amano, Yuki; Beppu, Hikari*; Endo, Takashi*; Nemoto, Kazuaki*; Sato, Tomofumi*; Thomas, B. C.*; Banfield, J. F.*

no journal, , 

17 (Records 1-17 displayed on this page)
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