The Effect of alkaline alteration on sorption properties of sedimentary rock

Shimoda, Satoko*; Nakazawa, Toshiyuki*; Kato, Hiroyasu*; Tachi, Yukio; Seida, Yoshimi*

Materials Research Society Symposium Proceedings, Vol.1665, p.179 - 184, 2014/09

https://doi.org/10.1557/opl.2014.644

The potential effect of alkaline perturbation caused by the cementitious materials must be evaluated in the performance assessment for HLW geological disposal. In this study, sorption of Cs, Ni and Th was investigated using the altered and unaltered samples of sedimentary rock from Horonobe underground research laboratory. The K values of Cs, Ni and Th measured by batch method using synthetic groundwater changed as a function of degrees of alteration. The K values of Cs increased with increasing degrees of alteration, indicating secondary minerals contributes to the increase in Cs sorption by ion exchange mechanism. On the other hand, the K values of Ni and Th decreased with the increase of degrees of alteration. This change may be caused by dissolution of clay minerals controlling Ni and Th sorption by surface complexation. These results imply that the effect of alkaline perturbation on K values of rocks depend on the surface property of the altered rock and sorption mechanism.

Study of "Likely Scenarios" and "Less-likely Scenarios" for sub-surface disposal of radioactive waste

Sugaya, Toshikatsu; Sone, Tomoyuki; Nakatani, Takayoshi; Ishitoya, Kimihide; Funabashi, Hideyuki; Sasaki, Ryoichi*; Shimoda, Satoko*; Kurosawa, Mitsuru*

JAEA-Research 2009-063, 80 Pages, 2010/03

JAEA-Research-2009-063.pdf:8.35MB

The purpose of this study was to assess exposure dose of "Likely Scenarios" and "Less-likely Scenarios" on sub-surface disposal. They were two of "Classification of three types scenarios" in "Basic Policy for Safety Regulation Concerning Land Disposal of Low-Level Radioactive Waste (Interim Report)" formulated by the Nuclear Safety Commission of Japan. Selection of the assessed scenarios, development of the assessment tool and preliminary exposure dose assessment were conducted. Maximum exposure doses for "Likely Scenarios" and "Less-likely Scenarios" were less than each standard dose value in the Interim Report (Likely Scenarios: 10Sv/y, Less-likely Scenarios: 300Sv/y).

Dose assessment for sub-surface disposal of radioactive waste, 1; Study of "Likely Scenarios" and "Less-likely Scenarios"

Nakatani, Takayoshi; Sugaya, Toshikatsu; Sone, Tomoyuki; Ishitoya, Kimihide; Funabashi, Hideyuki; Sasaki, Ryoichi*; Shimoda, Satoko*; Kurosawa, Mitsuru*

no journal, , 

The propose of study was safety assessment of "Likely scenarios" and "Less-likely scenarios" on sub-surface disposal. They were two of "Classification of three types scenarios" in "Basic Policy for Safety Regulation Concerning Land Disposal of Low-Level Radioactive Waste (Interim Report)" formulated by the NSC. Selection of the assessed scenarios, development of the assessment tool and preliminary exposure dose assessment were conducted according to the standard of the AESJ. As the results, Maximum exposure doses for "Likely Scenarios" and "Less-Likely Scenarios" were less than each standard dose value in the Interim Report (Likely Scenarios: 10Sv/y, Less-Likely Scenarios: 300Sv/y).

Assessment method development for radionuclide migration in compacted bentonite, 1; Development of sorption/diffusion data acquisition method in compacted system

Nakazawa, Toshiyuki*; Shimoda, Satoko*; Yamada, Norikazu*; Tachi, Yukio; Seida, Yoshimi*; Yui, Mikazu

no journal, , 

To set reliable parameters for the performance assessment (PA) of geological disposal, it is necessary to establish a reliable method for experimental evaluation and model prediction of sorption and diffusion in compacted bentonites. The through-diffusion and reservoir depletion experiments coupled with multiple curve analyses, including tracer depletion, breakthrough, and depth concentration curves were developed and applied for some systems including key radionuclides and geochemical conditions.

Development of multiple scenarios for mineralogical evolution of the host rocks affected by cement leachate solution, 2; Effect of representative secondary minerals in multiple scenarios

Yamaguchi, Kohei*; Shimoda, Satoko*; Akagi, Yosuke; Oda, Chie; Honda, Akira

no journal, , 

no abstracts in English

Development of sorption and diffusion data acquisition method in compacted bentonite, 1; Sorption and diffusion of Ni as functions of pH and salinity of porewater

Tachi, Yukio; Shimoda, Satoko*; Nakazawa, Toshiyuki*; Suyama, Tadahiro*; Yotsuji, Kenji

no journal, , 

Sorption and diffusion behaviors of Ni in compacted montmorillonite were investigated under different pH and salinity conditions by batch sorption and diffusion experiments. The Ni sorption was measured under four conditions with different pH (6, 8) and salinities (0.05, 0.5 M NaCl), and as functions of Ni concentration and reaction time. The tracer-depletion curves and depth profiles obtained for compacted montmorillonite with dry density of 800 kg/m were interpreted by first-order kinetics sorption based on batch sorption results. The Kd increased with increasing pH and with decreasing salinity of porewater, which are consistent between batch and diffusion tests. Sorption and diffusion behaviors were interpreted by coupling the thermodynamic sorption model, and the diffusion model based on EDL theory in narrow pores.

Solubility of amorphous UO and NpO in nitrate media containing platinum catalyst

Kitamura, Akira; Shimoda, Satoko*

no journal, , 

Solubility of amorphous uranium and neptunium dioxides was determined by undersaturation method under anoxic conditions in nitrate media. Effect of platinum catalysis was investigated to the experimental system whether the redox reaction between nitrate and reduced uranium/neptunium was promoted. No particular dependence of solubility values on nitrate concentration was observed. The obtained solubility values with containing platinum catalyst showed higher than those without containing platinum catalyst, which implied that the platinum catalyst contained oxygen gas or some oxidants even after blowing with hydrogen gas. Thermodynamic calculation was applied to the experimental values; most of data were well interpreted, and solubility-limiting solid phase and dominant aqueous species were estimated.

Evaluation of concrete waste generated by Fukushima Dai-ichi Nuclear accident, 1; Diffusion and sorption behavior of radionuclides in concrete

Akagi, Yosuke*; Shimoda, Satoko*; Kato, Hiroyasu*; Tachi, Yukio; Sakamoto, Hiroyuki*

no journal, , 

The Fukushima Dai-ichi Nuclear Power Plant accident has resulted in a large amount of radioactively contaminated concrete. As fundamental basis for developing the treatment and disposal concept for these wastes, migration behavior of radionuclides in concrete was investigated. Sorption and diffusion characteristics of tritiated water, cesium, iodine and uranium were measured at various conditions (concrete types, salinity, etc.).