Swelling characteristics of bentonites in artificial seawater

2009 ◽  
Vol 46 (2) ◽  
pp. 177-189 ◽  
Author(s):  
Hideo Komine ◽  
Kazuya Yasuhara ◽  
Satoshi Murakami
Keyword(s):  
Radioactive Waste ◽  
Swelling Pressure ◽  
Radioactive Waste Disposal ◽  
Exchangeable Cation ◽  
Deformation Characteristics ◽  
High Level Radioactive Waste ◽  
Disposal Facility ◽  
Buffer Material ◽  
Swelling Characteristics ◽  
High Level

Bentonite is currently designated for use as a buffer material for the repository of high-level radioactive waste because such a material requires swelling characteristics to seal the waste. A high-level radioactive waste disposal facility may be built in a coastal area of Japan because transportation of this waste by ships is feasible. Therefore, it is important to investigate the effects of seawater on a bentonite-based buffer. This study is intended to investigate the influence of seawater on the swelling pressure and swelling deformation characteristics of five common types of bentonite. The experiments described herein clarify the relations between the influence of seawater grade and compaction density, type of exchangeable cation, montmorillonite content of the bentonite, and vertical pressure condition. Based on experimental results, suitable specifications have been defined for a bentonite-based buffer that can withstand the effects of seawater.

scholarly journals Thermal Conductivity of Compacted GO-GMZ Bentonite Used as Buffer Material for a High-Level Radioactive Waste Repository

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Yong-Gui Chen ◽  
Xue-Min Liu ◽  
Xiang Mu ◽  
Wei-Min Ye ◽  
Yu-Jun Cui ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Radioactive Waste ◽  
Water Content ◽  
Radioactive Waste Disposal ◽  
Dry Density ◽  
Gmz Bentonite ◽  
High Level Radioactive Waste ◽  
Buffer Material ◽  
High Level ◽  
Crucial Parameter

In China, Gaomiaozi (GMZ) bentonite serves as a feasible buffer material in the high-level radioactive waste (HLW) repository, while its thermal conductivity is seen as a crucial parameter for the safety running of the HLW disposal. Due to the tremendous amount of heat released by such waste, the thermal conductivity of the buffer material is a crucial parameter for the safety running of the high-level radioactive waste disposal. For the purpose of improving its thermal conductivity, this research used the graphene oxide (GO) to modify the pure bentonite and then the nanocarbon-based bentonite (GO-GMZ) was obtained chemically. The thermal conductivity of this modified soil has been measured and investigated under various conditions in this study: the GO content, dry density, and water content. Researches confirm that the thermal conductivity of the modified bentonite is codetermined by the three conditions mentioned above, namely, the value of GO content, dry density, and water content. Besides, the study proposes an improved geometric mean model based on the special condition to predict the thermal conductivity of the compacted specimen; moreover, the calculated values are also compared with the experimental data.

scholarly journals Alteration of compacted GMZ bentonite by infiltration of alkaline solution

Clay Minerals ◽  
2016 ◽  
Vol 51 (2) ◽  
pp. 237-247 ◽  
Author(s):  
Chen Bao ◽  
Guo Jiaxing ◽  
Zhang Huixin
Keyword(s):  
Radioactive Waste ◽  
Alkaline Solution ◽  
Chemical Properties ◽  
Swelling Pressure ◽  
Cementitious Materials ◽  
Gmz Bentonite ◽  
High Level Radioactive Waste ◽  
Buffer Material ◽  
Porosity And Permeability ◽  
High Level

AbstractConcepts for geological disposal of high-level radioactive waste usually include bentonite buffer materials. Numerous studies have been performed with most usingWyoming bentonite. Gaomiaozi (GMZ) bentonite has been selected as a potential buffer/backfill material for the deep geological repository of high-level radioactive waste in China. In this context, the highly alkaline environment induced by cementitious materials in the repository is likely to alter montmorillonite, the main clay mineral in GMZ bentonite. This alteration may result in deterioration of the physical and/or chemical properties of the buffer material. To acquire quantitative data which would allow us to assess the dissolution of montmorillonite and changes in the diffusivity of hydroxide ions as well as their effects on the swelling pressure and permeability of the compacted GMZ bentonite, an experimental study was conducted under highly alkaline (NaOH solutions with various pH values were used), simulated groundwater conditions. The GMZ bentonite also contains cristobalite which may also have been dissolved. The microstructure of the compacted bentonite samples after the experiments was determined by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDX) was carried out to identify mineralogical changes. At pH >13, the permeability of specimens increased significantly; the swelling potential decreased with increasing pH. Furthermore, the pore volume and pore size of GMZ bentonite changed when exposed to alkaline solution, resulting in an increase in porosity and permeability. The main alteration mechanisms of compacted GMZ bentonite undergoing infiltration by highly alkaline solution are likely to be dissolution and modifications in terms of the microstructure and mineralogy.

Fundamental Properties of Monolithic Bentonite Buffer Material Formed by Cold Isostatic Pressing for High-Level Radioactive Waste Repository

1999 ◽  
Vol 556 ◽  
Author(s):  
S. Kawakami ◽  
Y Yamanaka ◽  
K. Kato ◽  
H. Asano ◽  
H. Ueda
Keyword(s):  
Hydraulic Conductivity ◽  
Radioactive Waste ◽  
Swelling Pressure ◽  
Cold Isostatic Pressing ◽  
Small Samples ◽  
Isostatic Pressing ◽  
High Level Radioactive Waste ◽  
Compacted Bentonite ◽  
Buffer Material ◽  
High Level

AbstractThe methods of fabrication, handling, and emplacement of engineered barriers used in a deep geological repository for high level radioactive waste should be planned as simply as possible from the engineering and economic viewpoints. Therefore, a new concept of a monolithic buffer material around a waste package have been proposed instead of the conventional concept with the use of small blocks, which would decrease the cost for buffer material. The monolithic buffer material is composed of two parts of highly compacted bentonite, a cup type body and a cover. As the forming method of the monolithic buffer material, compaction by the cold isostatic pressing process (CIP) has been employed.In this study, monolithic bentonite bodies with the diameter of about 333 mm and the height of about 455 mm (corresponding to the approx. 1/5 scale for the Japanese reference concept) were made by the CIP of bentonite powder. The dry densities: pd of the bodies as a whole were measured and the small samples were cut from several locations to investigate the density distribution. The swelling pressure and hydraulic conductivity as function of the monolithic body density for CIP-formed specimens were also measured.High density ( ρd: 1.4–2.0 Mg/m3) and homogeneous monolithic bodies were formed by the CIP. The measured results of the swelling pressure (3–15 MPa) and hydraulic conductivity (0.5–1.4×10−3 m/s) of the specimens were almost the same as those for the uniaxial compacted bentonite in the literature. It is shown that the vacuum hoist system is an applicable the handling method for emplacement of the monolithic bentonite.

scholarly journals EXPERIMENTAL STUDY ON MANUFACTURE OF BLOCK-TYPE BUFFER FOR HIGH-LEVEL RADIOACTIVE WASTE DISPOSAL

2003 ◽  
pp. 203-208
Author(s):  
Hideo KOMINE ◽  
Nobuhide OGATA ◽  
Akira NAKASHIMA ◽  
Hajime TAKAO ◽  
Hiroyoshi UEDA ◽  
...  
Keyword(s):  
Experimental Study ◽  
Radioactive Waste ◽  
Waste Disposal ◽  
Radioactive Waste Disposal ◽  
Block Type ◽  
High Level Radioactive Waste ◽  
High Level
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