2006 Fiscal Year Final Research Report Summary
Potential performance of clay buffer material as artificial barrier in geological disposal of radioactive waste
| Project/Area Number |
16360465
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Nuclear engineering
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
KOZAKI Tamotsu Hokkaido Univ., Grad.School of Eng., Assoc.Prof., 大学院工学研究科, 助教授 (60234746)
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| Co-Investigator(Kenkyū-buntansha) |
SATO Seichi Hokkaido Univ., Grad.School of Eng., Prof., 大学院工学研究科, 教授 (40117122)
KOZAI Naofumi Japan Atomic Energy Agency, Senior Researcher, 環境放射線工学ユニット, 研究副主幹 (80354877)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Radioactive waste / Geological disposal / Bentonite / Iron corrosion products / Diffusion |
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| Research Abstract |
In the geological disposal of high-level radioactive waste, an overpack(made of carbon steel) would gradually corrode in a clay buffer material(Na-bentonite) and release iron corrosion products(mainly Fe^<2+> ions) into the clay buffer. Thus the Fe^<2+> ions could be replaced with original exchangeable cations of bentonite such as Na^+ and Ca^+, and form Fe(II)-bentonite, resulting in alteration of the performance of clay buffer materials. A decrease in swelling of bentonite buffer caused by the alteration is one of negative effects to deteriorate the performance. Contrarily, there would be potential positive effects to improve the performance by the alteration ; e.g. the altered bentonite including Fe(II)-bentonite could adsorb or stabilize some kind of radionuclides, resulting in the retardation of the radionuclides.
In this study, therefore, preparation and characterization of Fe(II)-bentonite were carried out. Fe(II)-bentonite was obtained by the conventional cation-exchange method in which Na-bentonite is contacted with FeCl_2 solution in an inert-gas glove box. On the other hand, a new preparation method using Fe(II)-nitrilotriacetate complex (Fe(II)-NTA solution) was developed in this study.
Both Fe(II)-bentonite and the oxidized Fe(II)-bentonite were characterized by several methods, such as SEM-EDX, FT-IR, Mossbauer spectroscopy, micro-PIXE analysis, and chemical analysis. The results of the sample characterization suggest that Fe^<2+> ions existing in the bentonite as exchangeable cations are relatively stable. In addition, the new preparation method for Fe(II)-bentonite was found to be advantageous; it enabled preparation of Fe(II)-bentonite without the use of an inert-gas glove-box and avoided sample exposure to unfavorable counterions, like Cl^- ions.
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Research Products
(5 results)
