Development of evaluation for swelling and sealing characteristics of heated bentonite based buffer in high-temperature conditions.

高温条件下加热膨润土基缓冲剂的膨胀和密封特性评估的开发。

• 批准号: 17360220
• 负责人: KOMINE Hideo
• 金额: $ 10.17万
• 依托单位: Ibaraki University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2005
• 资助国家: 日本
• 起止时间: 2005 至 2007
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-17360220/
• 关键词: Bentonite; High-level radioactive waste; Geological disposal; Swelling; Thermal history; Clay mineral; Montmorillonite; Cation; モンモリトナイト

High-level radioactive waste (HLW) exhausted from the nuclear plant has very high radioactivity level, so it will be required the very long term of years to become no influence to human's living environment. Therefore, it is very difficult to keep storing and to manage high activity waste for a long term safely. In the international society, it is considered that the geological disposal is the best. The high activity waste also in Japan is stored for about 30-50 years, and it is scheduled to dispose to geologic layer deeper than 300m in the underground. It is thought that the high activity waste can be safely isolated for a long term by adopting the multibarrier system that consists of the engineered barrier and the natural barrier when geological disposal. The engineered barrier is composed of the vitrified waste, overpack, and buffer material. The use of the bentonite that has the self sealing by the swelling for the material of the buffer material is promising. On the other hand, th … More e high activity waste evolves a large amount of radioactive decay heat by decay of the radioactivity. The inside of the buffer material becomes a high temperature by the radioactive decay heat. The temperature in the buffer material becomes the highest in tens of years after disposing the high activity waster in underground. It decreases gradually with the passage of time. However, the state of the high temperature has expected to continue for at least many hundreds of year. The-self-sealing expected of a bentonite-based buffer material is demonstrated by swelling However, the decrease in the self-sealing is afraid by the radioactive decay heat before the swelling.To solve the problem mentioned above, this study investigated the influence of some thermal histories to swelling of bentonite materials by experimental works. This study used four kinds of bentonite named A, B, C, and E. The thermal temperatures were 60, and 90, 110, 130℃. This study conducted the swelling pressure experiment and the swelling deformation experiment. From the results, the influence of the thermal history of bentonite A, B, and E, was a little in the swelling pressure characteristics. In addition, the influence of the thermal history was a little in the swelling deformation property in case of confining stress 1000kPa. The influence of the thermal history of bentonite C was a little in the swelling deformation property in case of cofining stress 1000kPa. The influence of the thermal history of bentonite C was a little in the swelling pressure characteristics of condition with a high initial dry density. Moreover, the influence of the thermal history was a little in the swelling deformation property in case of cofining stress 1000kPa of the heating temperature 60℃.To discuss the mechanism on influences of thermal history to swelling characteristics of the bentonite, this study conducted the X-ray diffraction analysis, surround water chemical analysis after experiment, and the methylene blue absorption tests and the cation exchange capacity of bentonite before and after experiments. From the above experimental results, the decrease in the swelling characteristics of bentonite A was considered as the decrease in the adsorption ability of the cation of montmorillonite. The decrease in the swelling characteristics of bentonite C was considered as the decrease of content of montmorillonite. Furthermore, this study proposed "Equations for evaluating the swelling behavior that considered the influence of the thermal history" on the basis of the above experimental results and discussions of mechanism. In this proposed equations, it was considered that the cation adsorption ability of montmorillonite decreased by the thermal history. The exchangeable cation amount and the cation exchange capacity were calculated based on the measurement result of the amount of the methylene blue adsorption. The calculated results by the above proposed equations were compared with the experimental results. From the results, the validity of proposed equations was clarified. Less

核电站排放的高放废物具有很高的放射性水平，需要很长的时间才能使其对人类生存环境无影响。因此，很难长期安全地保存和管理高活性废物。在国际上，地质处理被认为是最好的处理方法。日本的高放射性废物也储存约30-50年，并计划将其处理到地下300米以上的地质层。认为在地质处置时，采用工程屏障和天然屏障相结合的多屏障系统，可以长期安全隔离高放射性废物。工程屏障由玻璃化废物、外包装和缓冲材料组成。膨润土具有膨胀自密封性，作为缓冲材料的应用前景广阔。另一方面， ...更多信息 高放射性废物通过放射性衰变放出大量放射性衰变热。缓冲材料的内部由于放射性衰变热而变成高温。高放射性废物地下处理后，缓冲材料中的温度达到几十年来的最高值。它随着时间的推移而逐渐减少。然而，高温状态预计将持续至少数百年。膨润土缓冲材料的自密封性是通过膨胀来实现的，但膨胀前的放射性衰变热会使自密封性降低，为了解决上述问题，本研究通过实验研究了一些热历史对膨润土材料膨胀的影响。本研究选用了A、B、C、E四种膨润土。热处理温度分别为60、90、110、130℃。进行了膨胀压力实验和膨胀变形实验。结果表明，膨润土A、B和E的热历史对膨润土的膨胀压力特性影响较小。在围压为1000 kPa时，热历史对膨胀变形性能的影响较小。膨润土C在1000 kPa的压缩应力下的膨胀变形性能受热历史的影响较小。在初始干密度较高的条件下，膨润土C的膨胀压力特性受热历史的影响较小。此外，在加热温度为60℃、压缩应力为1000 kPa的情况下，热历史对膨润土的膨胀变形性能影响较小。为了探讨热历史对膨润土膨胀特性的影响机理，本研究在实验后进行了X射线衍射分析、周围水化学分析、实验前后膨润土的亚甲基蓝吸附试验和阳离子交换容量。从上述实验结果可以看出，膨润土A的膨胀特性的降低被认为是蒙脱石阳离子吸附能力的降低。膨润土C的膨胀特性降低，可认为是蒙脱石含量的降低。此外，本研究根据上述实验结果和机理讨论，提出了“考虑热历史影响的膨胀行为评价方程”。该方程考虑了蒙脱石对阳离子的吸附能力随热历史的变化而降低。基于亚甲基蓝吸附量的测量结果计算可交换阳离子量和阳离子交换容量。将计算结果与实验结果进行了比较。结果表明，所提出的方程是正确的。少

项目成果

Applicability of theoretical evaluations on swelling behaviors of bentonite buffer

膨润土缓冲液膨胀行为理论评价的适用性

• 发表时间: 2007
• 作者: 大森浩司;小峯秀雄;安原一哉;村上哲;小峯秀雄・安原一哉・村上 哲・佛田理恵・山口憲治・竹内靖典;小峯秀雄・安原一哉・村上 哲・佛田理恵・山口憲治・竹内靖典;Hideo KOMINE
• 通讯作者: Hideo KOMINE

Dynamic compaction properties of bentonite-based materials

• DOI: 10.1016/j.enggeo.2008.01.005
• 发表时间: 2008-05
• 期刊: Engineering Geology
• 影响因子: 7.4
• 作者: Hiroshi Ito;H. Komine

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• 发表时间: 2006
• 期刊: 土木学会第61回年次学術講演会講演概要集 (CD-ROM)
• 作者: 大森浩司;小峯秀雄;安原一哉;村上哲
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• 发表时间: 2006
• 期刊: 土木学会第61回年次学術講演会講演概要集 (CD-ROM)
• 作者: 小峯秀雄;安原一哉;村上哲;百瀬和夫;坂上武晴
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