Model development of coupled THMC processes for a geological repository at higher temperature region

Takubo, Yusaku*; Takayama, Yusuke; Idiart, A.*; Tanaka, Tatsuya*; Ishida, Keisuke*; Fujisaki, Kiyoshi*

Proceedings of 2022 International High Level Radioactive Waste Management Conference (IHLRWM 2022) (Internet), p.906 - 915, 2022/11

no abstracts in English

Assessment of sorption and diffusion in the rock matrix in the NUMO safety case

Hamamoto, Takafumi*; Shibutani, Sanae*; Ishida, Keisuke*; Fujisaki, Kiyoshi*; Yamada, Motoyuki*; Tachi, Yukio

Proceedings of 6th East Asia Forum on Radwaste Management Conference (EAFORM 2017) (Internet), 6 Pages, 2017/12

http://eaform2017.aesj.or.jp/file/PapersList/Session4/(4A-2)_%20T.Hamamoto(NUMO).pdf

NUMO has developed a generic safety case to demonstrate the feasibility and safety of geological disposal of HLW and TRU in Japan and to provide a basic structure for the safety case which will be applicable to any potential site. In this safety case, the safety assessment was carried out for the repositories tailored to site descriptive models developed for three representative rock groups (plutonic, Neogene sedimentary and Pre-Neogene sedimentary rocks). Radionuclide migration parameters in rocks, i.e. distribution coefficients (Kds) and effective diffusion coefficients (Des), were derived to allow safety analysis for a range of scenarios. In this generic stage, the values of these parameter were given as the statistical values derived from laboratory data for certain rock types. The data were extracted from the latest database, with interpretation based on radionuclide speciation derived from relevant groundwater thermodynamic modelings.

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage, 2; Progress report on NUMO-JAEA collaborative research in FY2012 (Joint research)

Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Hayano, Akira; Makino, Hitoshi; Wakasugi, Keiichiro; Mitsui, Seiichiro; Oda, Chie; Kitamura, Akira; Osawa, Hideaki; et al.

JAEA-Research 2013-037, 455 Pages, 2013/12

JAEA-Research-2013-037.pdf:42.0MB

Following FY2011, JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation stage. With regard to (1) study on rock suitability in terms of hydrology, the tree diagram of methodology of groundwater travel time has been extended for crystalline rock, in addition, tree diagram for sedimentary rock newly has been organized. With regard to (2) study on scenario development, the existing approach has been improved in terms of a practical task, and applied and tested for near field focusing on the buffer. In addition, the uncertainty of some important processes and its impact on safety functions are discussed though analysis. With regard to (3) study on setting radionuclide migration parameters, the approaches for parameter setting have been developed for sorption for rocks and solubility, and applied and tested through parameter setting exercises for key radionuclides.

Surface speciation of Eu adsorbed on kaolinite by time-resolved laser fluorescence spectroscopy (TRLFS) and parallel factor analysis (PARAFAC)

Ishida, Keisuke*; Saito, Takumi*; Aoyagi, Noboru; Kimura, Takaumi; Nagaishi, Ryuji; Nagasaki, Shinya*; Tanaka, Satoru*

Journal of Colloid and Interface Science, 374(1), p.258 - 266, 2012/05

https://doi.org/10.1016/j.jcis.2012.01.060

Adsorption of Eu(III) on a heterogeneous surface studied by Time-Resolved Laser Fluorescence Microscopy (TRLFM)

Ishida, Keisuke*; Kimura, Takaumi; Saito, Takumi*; Tanaka, Satoru*

Environmental Science & Technology, 43(6), p.1744 - 1749, 2009/02

https://doi.org/10.1021/es8024287

Time-Resolved Laser Fluorescence Microscopy (TRLFM) is a useful tool to simultaneously investigate the intensity, location, types and surrounding chemical environment of a fluorophore. In this study, we demonstrated the applicability of TRLFM for the adsorption of Eu(III) on a natural heterogeneous surface. Different chemical species of Eu(III) were observed on the Makabe granite surface and its constituents (biotite, plagioclase, potassium feldspar and quartz). Eu(III) heterogeneously adsorbed on biotite, plagioclase and quartz and homogeneously on potassium feldspar. The histograms of the fluorescence decay rates of adsorbed Eu(III) revealed the presence of single specie of Eu(III) on biotite and two common species on plagioclase and potassium feldspar. The adsorption of Eu(III) on Makabe granite surface was highly heterogeneous. The TRLFM measurements of different regions of the granite surface turned into the finding of Eu(III) with different fluorescence decay rates. Comparing with fluorescence decay histograms of the mineral constituents, Eu(III) clearly adsorbed on the feldspar family, plagioclase and potassium feldspar. It was also found that Eu(III) adsorbed as an outer-sphere complex and on an altered mineral, possibly smectite resulting from the weathering plagioclase.

Fluorescence lifetime imaging microscopy applied for Eu(III) adsorbed on granite

Ishida, Keisuke*; Kimura, Takaumi; Saito, Takumi*; Toraishi, Takashi*; Tanaka, Satoru*

no journal, , 

no abstracts in English

Adsorption of Eu(III) on a heterogeneous surface studied by Time-Resolved Laser Fluorescence Microscopy (TRLFM)

Ishida, Keisuke; Kimura, Takaumi; Saito, Takumi*; Tanaka, Satoru*

no journal, , 

no abstracts in English

Multivariable factor analysis for time-resolved laser fluorescence spectroscopy of the uranyl adsorption on gibbsite

Sao, Hirokazu*; Ishida, Keisuke; Saito, Takumi*; Aoyagi, Noboru; Nagasaki, Shinya*; Tanaka, Satoru*

no journal, , 

Structures of the Ln/An in solution and on mineral surfaces have been assessed by various spectroscopic techniques. In a relatively simple system containing a few species in solution this can be done unequivocally. However, on mineral surfaces at relatively high pH or in the presence of ligand molecules measured spectra are hard to interpret because of the co-existence of many species and/or the heterogeneity of the surfaces. In addition spectroscopic measurements involve several parameters, not only spectroscopic parameters like wavelength and delay time, but also chemical parameters like pH and concentrations of reactants. Therefore, the information on the number and relative amounts of different chemical species formed should be pursued in the entire multi-dimensional parameter space and one needs a systematic approach based on statistical argument for the purpose. The goal of this study is to construct a multivariable analysis method for TRLFS, which can extract the number of components, their pure spectra and the variation of their quantities from a series of spectra measured as a function of wavelength, time and chemical conditions. Uranyl sorption on gibbsite is studied by TRLFS as a test system for this purpose. It has been shown that the spectral shapes of uranyl on gibbsite varies as the delay time of the detector increases and as pH of the solution is changed, suggesting the presence of multiple sorption complexes of uranyl on gibbsite. The obtained TRLFS spectra are processed by the fixed-size window evolving factor analysis to extract the number of statistically meaningful components, followed by nonlinear least square regression for the deconvolution of temporally varying spectra.

Scenario development for the risk-informed safety assessment of geological disposal

Makiuchi, Akie*; Ishida, Keisuke*; Kurosawa, Susumu*; Inagaki, Manabu*; Umeki, Hiroyuki*; Ebashi, Takeshi; Wakasugi, Keiichiro; Makino, Hitoshi; Shibata, Masahiro

no journal, , 

NUMO is developing a safety case for the geological disposal of vitrified high-level radioactive wastes and TRU wastes on the basis of the latest findings. In parallel, JAEA starts to investigate the geological disposal of spent fuel as an alternative disposal option. In such a situation, NUMO and JAEA have jointly established a scenario development method. Since the considerations of both probabilities and influences of scenarios or processes are focused on, the disaggregated approach is adopted. This approach had been recommended by ICRP, and applied to Japanese safety regulations for disposing low-level waste. To efficiently identify processes that may influence geological disposal systems, various supposable processes are analyzed in terms of their probabilities and influences on the safety function by conducting audits using FEP information. One remarkable feature of this method is its demand of high-level traceability of various judgments through analysis and definition of scenarios. Traceability is ensured by various tools and/or products. One such example is a "Safety Function/Variable/Process Diagram", which structurally illustrates interrelations between safety functions, processes and variables of geological disposal systems. This presentation will show the features of the abovementioned method in detail along with some examples of developed scenarios.

Sorption behaviour of lead onto montmorillonite in the presence of carbonate

Sugiura, Yuki; Ishidera, Takamitsu; Suyama, Tadahiro*; Okazaki, Mitsuhiro*; Hamamoto, Takafumi*; Ishida, Keisuke*; Tachi, Yukio

no journal, ,