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JAEA Reports

An Estimation of the Effecticve Diffusion Coefficients and Distribution Coefficients of Iodine in Granodiorite and Sandstone Saturated by Synthetic Cement Pore Water and Synthetic Groundwater

Honda, Akira; Mihara, Morihiro; Kato, Hiroshige*

JNC TN8400 2004-020, 69 Pages, 2004/11

JNC-TN8400-2004-020.pdf:3.09MB

Cementitious materials will be used expensively in the TRU waste repository. The cementitious materials will keep the high pH condition (pH$$<$$12) in the pore water of repository and the surrounding environment for long period. Thus it is necessary to obtain the data measured under the high pH conditions for the performance assessment of the TRU waste repository. However the uumber of the available data are limited. On the other hand, iodine-129 is an important nuclide because of its long half-time and poorly-sorbing nature. Therefore the effective diffusion coefficients De and distribution coefficients Kd of iodine in both crystalline rock and sedimentary rock were estimated in this study. Granodiorite and sandstone were selected as an example of crystalline rock and that of sedimentary rock respectively. Through diffusion experiment were carried out in an argon atmosphere.The diffusivity of iodine in both type rocks saturated by synthetic cement pore water was reduced with increasing experimental period. The analysis of experimental results suggested that this phenomenon was caused by decrease of De values. For granodiorite, the De values obtained in this study using synthetic cement pore water were 2 orders of magnitude smaller than literature values which obtained at neutral pH. For sandstone, the De values using synthetic cement pore water were 1 - 2 orders smaller than literature values, however those using synthetic groundwater were consistent with literature values. SEM observation of sandstone after the diffusion experiment showed that the secondary mineral coated the surface of sandstone. These observation results suggested that decrease of De value in case of synthetic cement pore water was ascribed to the precipitation of secondary mineral.In this study, Kd values of iodine on sandstone were 1.7x10$$^{-3}$$- 3.0x10$$^{-3}$$m$$^{3}$$/kg in synthetic groundwater. However Kd values of other cases could not be estimated.

JAEA Reports

An Estimation of Applicable Thermodynamic Data of C-S-H Gel for PHREEQC

Kato, Hiroshige*; Honda, Akira

JNC TN8400 2004-015, 282 Pages, 2004/07

JNC-TN8400-2004-015.pdf:1.83MB

Cementitious materials will be used extensively in the TRU waste repository. The dissolution/precipitation of cementitious materials will affect the chemical condition of pore water of TRU waste repository. Thus, it is important for estimation of chemical condition of pore water to apply the dissolution/precipitation of cementitious materials appropriately. A C-S-H gel (poorly crystallized calcium silicate hydrate) is a major component in cementitious materials which determined the mechanical characteristics of cementitious materials. The hydraulic condition of cementitious materials is strongly affected by the dissolution/precipitation of C-S-H gel due to the change of porosity accompanied with the dissolution/precipitation processes. Further, the chemical condition of pore water will be dominated by the dissolution/precipitation of C-S-H gel for a long period. Therefore, an importance of the dissolution/precipitation of C-S-H gel has been recognized internationally, and several dissolution/precipitation models of C-S-H gel have been proposed. The principal scopes of the C-S-H gel models are description of an incongruent dissolution/precipitation behavior of C-S-H gel. On the other hand, PHREEQC is a computer program, which has been used generally for the geochemical calculation. PHREEQC can provide the state of chemical equilibrium of system defined by chemical equations and equilibrium constants (log K). In JNC, reference model groundwater determined by calculation using PHREEQC in HLW study will be also used in TRU waste study. In addition, PHREEQC will be used for calculation of the cement-water reaction. Therefore, applicability of the presented dissolution/precipitation models of C-S-H gel to PHREEQC was estimated. As a result of estimation of the applicability, Atkinson model and Reardon model were selected as suitable models to the PHREEQC. The chemical equations and log K values of C-S-H gel were derived from these models and tested using PHREEQC

JAEA Reports

The Sorption database of radionuclides for cementitious materials

Kato, Hiroshige*; Mine, Tatsuya*; Mihara, Morihiro; Oi, Takao; Honda, Akira

JNC TN8400 2001-029, 63 Pages, 2002/01

JNC-TN8400-2001-029.pdf:1.81MB

Cementitious materials will be used for the TRU waste repository as a component of engineered barrier system. The distribution coefficients which represent the retardation of radionuclides migration for the cementitious materials would be one of the important parameter for the safety assessment. The much information of radionuclide sorption onto the cementitious materials has been accumulated through the study in the world. Therefore it is necessary to compile the information and Kd of the radionuclides reported in previous studies. In this report, the Kd of the important radionuclides, such as C, Ni, Se, Sr, Zr, Nb, Mo, Tc, Sn, I, Cs, Sm, Pb, Ra, Ac, Th, Pa, U, Np, Pu, Am, Cm, for the cementitious materials were compiled as the Sorption Database (SDB). For radionuclides to be sensitive to the redox potential, e.g. Se, Tc, Pa, U, Pu and Np, some Kds measured under the controlled atmosphere had been reported, and few Kds measured under the controlled redox potential had been reported. For Se, Mo, Sm, Cm and Ac, the distribution coefficients had not been reported, therefore distribution coefficients of Se and Mo for OPC (Ordinary Portland Cement) pastes were measured by batch sorption experiments and these data were added into the SDB.

JAEA Reports

Effect of leachate of cementitious materials on the geological media; Experimental study of the influence of high pH plume on rock

Kato, Hiroshige*; Sato, Mitsuyoshi*; Owada, Hitoshi*; Mihara, Morihiro;

JNC TN8430 2000-008, 53 Pages, 2000/05

JNC-TN8430-2000-008.pdf:4.8MB

Cementitious materials will be used in TRU waste disposal repository. In such cases, it is considered that the migration of alkaline leachates from cementitious materials, so called high pH plume, will cause dissolution of rock and precipitation of secondary minerals. In addition, the high pH plume will move along the flow of groundwater, so it is predicted that rock formation and components of high pH groundwater vary with time and space. However, time and spatial dependence of the variations of secondary minerals and groundwater components has not been clarified. In order to acquire the data of variations of secondary minerals and groundwater components, we carried out the rock alteration experiments with column method. The crushed granodiorite was filled into 4 meters length column ($$phi$$3.7 cm) and artificial cement leachate (pH=13.3; Na=0,1 mol/l, K=0.1 mol/l, Ca=0.002 mol/l) was streamed at flow rates of 0.1 ml/min for 7 months at 80$$^{circ}$$C. As the result, secondary minerals confirmed on the rock were calcite and C-S-H at upstream of column and C-S-H at mid-downstream. The pH value of the fluid dominated by Na and K did not be decreased by reaction with the rock. In this study, the data relating to the effect of high pH plume on rock over the long term was acquired.

Journal Articles

Development of 46-kA Nb$$_{3}$$Sn conductor joint for ITER model coils

Takahashi, Yoshikazu; Nunoya, Yoshihiko; Nishijima, Gen; Koizumi, Norikiyo; Matsui, Kunihiro; Ando, Toshinari; Hiyama, Tadao; Nakajima, Hideo; Kato, Takashi; Isono, Takaaki; et al.

IEEE Transactions on Applied Superconductivity, 10(1), p.580 - 583, 2000/03

 Times Cited Count:20 Percentile:68.92(Engineering, Electrical & Electronic)

no abstracts in English

JAEA Reports

Distribution coefficients of radio-elements on compacted bentonite under cementitious conditions

Mine, Tatsuya*; Mihara, Morihiro; Kato, Hiroshige*

JNC TN8430 99-012, 166 Pages, 1999/11

JNC-TN8430-99-012.pdf:4.31MB

It is important to obtain the distribution coefficients of radio-elements on the bentonite under cementitious conditions in the geological disposal system of radioactive wastes. In-Diffusion experiments of Cs, Sr, Zr, Nb, Ni, Sn, Am, U, Np in Na-bentonite, Ca-bentonite, bentonite analcite mixture were carried out and the distribution coefficients were calculated. The experimental parameters were dry density (1200kg/m$$^{3}$$, 1600kg/m$$^{3}$$, 1800kg/m$^${3}$) and synthetic solution type (distilled water, cementitous solution, cementitious solution+sea water, cementitous solution+sea water+nitrate). It was shown that the effects of the experimental parameters on the distribution coefficients on the most part of radio-elements used in this study were relatively small.

JAEA Reports

None

Mine, Tatsuya*; Mihara, Morihiro; Ito, Masaru; Kato, Hiroshige*

PNC TN8410 97-258, 57 Pages, 1997/06

PNC-TN8410-97-258.pdf:2.81MB

None

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