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Jaquet O.,In2Earth Modelling Ltd. | Lantuejoul C.,MINES ParisTech | Goto J.,Nuclear Waste Management Organization of Japan
Journal of Volcanology and Geothermal Research | Year: 2012

Risk assessments in relation to the siting of potential geological repositories require the estimation of long-term volcanic hazard. Owing to their tectonic situation, many industrial regions around the world are concerned by such evaluation. For sites near volcanically active regions, the prevailing source of uncertainty is long-term volcanic hazard. The complexity and non-linearity of volcanic processes, the space-time variability in terms of distribution and intensity for volcanic events and the limited amount of information make probabilistic estimation of volcanic hazard ineluctable. The needs for reliable methodologies for volcanic and tectonic hazard assessments in Japan have stimulated the development of specific stochastic models for improving uncertainty characterization. A conditional Cox process with a multivariate potential was developed for the assimilation of geophysics and tectonic data (gravity data, GPS strain rate data and active faults). The theoretical basis and concepts of the proposed model are given and a methodological illustration is provided using data from the island of Kyushu. © 2012 Elsevier B.V. Source

Karasaki K.,Lawrence Berkeley National Laboratory | Onishi C.T.,U.S. Geological Survey | Goto J.,Nuclear Waste Management Organization of Japan
47th US Rock Mechanics / Geomechanics Symposium 2013 | Year: 2013

A study was conducted on the Wildcat Fault in Berkeley, CA to develop a methodology for characterizing the hydrologic properties of a fault. The rocks are extensively sheared and fractured. The Wildcat, a strike-slip fault, appears to consist of multiple fault planes. That the exact location of the main fault is still at dispute among participating researchers highlights the fact that it is very difficult to uniquely characterize such a complex fault zone. The hydrologic characteristics of the Wildcat Fault zone suggest a dual nature - with high permeability along the direction of the fault zone and low permeability across it. Data from pumping tests conducted in the high permeability zone along the fault plane exhibit 10:1 near-horizontal anisotropy. The main philosophy behind our overall approach to the hydrologic characterization of such a complex fractured system is to let the system take its own average by conducting large scale tests and conducting long term monitoring instead of collecting a multitude of data at small length and time scales, or at a discrete fracture scale and to "up-scale," which is extremely tenuous at best. Copyright 2013 ARMA, American Rock Mechanics Association. Source

Ishida K.,Nuclear Waste Management Organization of Japan | Saito T.,University of Tokyo | Aoyagi N.,Japan Atomic Energy Agency | Kimura T.,Japan Atomic Energy Agency | And 3 more authors.
Journal of Colloid and Interface Science | Year: 2012

Time-resolved laser fluorescence spectroscopy (TRLFS) is an effective speciation technique for fluorescent metal ions and can be further extended by the parallel factor analysis (PARAFAC). The adsorption of Eu 3+ on kaolinite as well as gibbsite as a reference mineral was investigated by TRLFS together with batch adsorption measurements. The PAFAFAC modeling provided the fluorescence spectra, decay lifetimes, and relative intensity profiles of three Eu 3+ surface complexes with kaolinite; an outer-sphere (factor A) complex and two inner-sphere (factors B and C) complexes. Their intensity profiles qualitatively explained the measured adsorption of Eu 3+. Based on the TRLFS results in varied H 2O/D 2O media, it was shown that the outer-sphere complex exhibited more rapid fluorescence decay than Eu 3+ aquo ion, because of the energy transfer to the surface. Factor B was an inner-sphere complex, which became dominant at relatively high pH, high salt concentration and low Eu 3+ concentration. Its spectrum and lifetime were similar to those of Eu 3+ adsorbed on gibbsite, suggesting its occurrence on the edge face of the gibbsite layer of kaolinite. From the comparison with the spectra and lifetimes of crystalline or aqueous Eu(OH) 3, factor C was considered as a poly-nuclear surface complex of Eu 3+ formed at relatively high Eu 3+ concentration. © 2012 Elsevier Inc. Source

Miyahara K.,Japan Atomic Energy Agency | Kawamura M.,Chiyoda Corporation | McKinley I.G.,McKinley Consulting | Inagaki M.,Japan Atomic Energy Agency | And 2 more authors.
Journal of Nuclear Science and Technology | Year: 2011

In Japan, uplift/erosion scenarios must be analysed even if they occur far in the future, as no assessment cut-off times have yet been defined. For this purpose, the geological record of river terrace formation and their long-term evolution have been studied further, with the aim of constructing a better defined fluvial erosion model than the original, rather simple cyclic fluvial erosion model developed in a previous study. The developed conceptual model, based on a generalization of field observations in relevant settings, allows the consequences of erosion of the repository to be assessed just as before, using comparisons with natural radionuclide fluxes. Results illustrate the effectiveness and robustness of the H12 HLW disposal system and indicate that erosion scenarios are unlikely to be critical for distinguishing between different sites that lie in similar mid-range river settings. © 2011 Atomic Energy Society of Japan, All Rights Reserved. Source

Karasaki K.,Lawrence Berkeley National Laboratory | Doughty C.,Lawrence Berkeley National Laboratory | Onishi C.T.,U.S. Geological Survey | Goto J.,Nuclear Waste Management Organization of Japan
Transport in Porous Media | Year: 2015

We have conducted field investigations of the Wildcat fault in Strawberry Canyon in the East Bay Hills of Berkeley, California, including a literature survey, aerial-photographic—based geomorphological study, geologic mapping, geophysical surveys, trenching, and borehole drilling and hydraulic testing. A geologic model was constructed, which became the basis of the hydrologic model. We outline the effort of constructing the geohydrologic model of the Strawberry Canyon area. We also created an East Canyon sub-model, which is a part of the Strawberry Canyon area. These models were constructed using Petrasim commercial software, which is a pre- and post- processor for TOUGH2, a non-isothermal multiphase flow and transport simulator. One of our goals is to understand the role of the Wildcat fault in controlling the natural-state groundwater flow. Another goal is that with limited data in numbers and areal extent, we evaluate the viability of modeling a relatively complex geologic area in hopes of to building a model that is valid for a scale larger than the observation. We performed both manual and automated inversion analyses and produced reasonable matches between the observed head data and model predictions. By varying the structure of the Wildcat fault, the base-case representation, which includes a high permeability damage zone and a low permeability fault core, best matches the observed head data. Using the sub-model, we conducted two-phase non-isothermal simulations utilizing the pressure and temperature data from the boreholes. We also used the information obtained from pump tests including permeability anisotropy of the fault plane. After parameter searches, we were able to match the head and temperature profiles along boreholes relatively well. We then used the best matching models to predict the observed rate of head decline during a dry period and found that anisotropic fault zone with 5 % porosity predicts the rate of decline reasonably well. There is a potential that the rate of decline may be useful to estimate the parameters downstream where there are no boreholes for observation/testing. © 2014, Springer Science+Business Media Dordrecht (outside the USA). Source

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