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Swelling characteristics of bentonite buffers under high

高温下膨润土缓冲液的溶胀特性

基本信息

批准号：
1855518
负责人：
金额：
--
依托单位：
Imperial College London
依托单位国家：
英国
项目类别：
Studentship
财政年份：
2016
资助国家：
英国
起止时间：
2016 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=studentship-1855518
关键词：
Swelling characteristics bentonite buffers under

项目摘要

Although nuclear waste exists in significant quantities and is continuously produced worldwide, waste management represents a great challenge which has yet to be resolved, but which is becoming pressing under the interest that energy and sustainability-related issues attract. Deep geological repositories are scientifically considered to be the only feasible way to dispose of nuclear waste. Although different countries have developed different geological disposal concepts, depending on regional geology, most concepts share the idea of engineering a barrier (buffer) of a compacted, highly expansive clay (e.g. MX80 bentonite) between the canister containing the waste and the host formation. As no appropriate site for a repository has been selected in the UK, research on the topic remains generic, with the thermo-hydro-mechanical behaviour of bentonite buffers being a major area of investigation. Issues of concern identified by UK policy makers RWM Ltd include temperature effects on strength and stiffness (shear and bulk), swelling potential, homogenisation, permeability, water retention capability and resaturation bentonite buffers. Being unsaturated at the time of placement, the buffer is expected to absorb ground water from the host formation and in doing so, to swell into gaps left open during placement, providing sealing and protection to the canisters bearing nuclear waste. This renders the swelling potential of the clay one of the key parameters in assessing its suitability as a buffer material in nuclear waste disposal. Nonetheless, the high temperatures generated by the waste may alter the swelling its characteristics, compromising its ability to perform its designated function, rendering it vulnerable to cracking, thus compromising the safety of the nuclear waste repository, which typically is expected to have a design life of over 10000 years.The aim of the project is to characterise the effect of temperature on the swelling behaviour of compacted MX80 bentonite, proposed to be used as buffer in the SKB concept for deep geological disposal, due to its swelling and self-healing capability. The scope of the proposed PhD project is: (a) to measure the swelling potential of MX80 at ambient temperature and at temperatures up to 85oC; (b) to provide experimental insight as to how the as-compacted properties of MX80 may affect its swelling potential at high temperatures; (c) to optimise the initial properties of MX80 in order to improve its performance. This is associated with optimising both the as-compacted state of the buffer and the gaps left during its placement in deposition holes. To this end, a newly designed oedometer cell will be commissioned and utilised. The equipment was funded by EPSRC (EP/J021199/1) and forms part of a series of equipment which includes the following cells: (a) temperature-controlled oedometer; (b) suction-controlled oedometer; (c) temperature-controlled triaxial; (d) temperature-controlled isotropic cell; and (e) set of four desiccators with RH control. The project forms part of coordinated efforts within the Geotechnics section to tackle challenging topics related to Energy Geotechnics.

虽然核废料数量巨大，而且在世界各地不断产生，但废料管理是一个尚待解决的巨大挑战，但由于能源和可持续性相关问题引起的关注，这一挑战正变得越来越紧迫。从科学上讲，深层地质处置库被认为是处置核废料的唯一可行办法。虽然不同国家根据区域地质情况制定了不同的地质处置概念，但大多数概念都有一个共同的想法，即在含有废物的罐和主地层之间设计一个压实的高膨胀性粘土（如MX 80膨润土）屏障（缓冲区）。由于在联合王国没有选定适当的处置库地点，因此关于这一专题的研究仍然是一般性的，膨润土缓冲层的热-水-力学行为是一个主要的调查领域。英国决策者RWM Ltd确定的关注问题包括温度对强度和刚度（剪切和体积）的影响、膨胀潜力、均质化、渗透性、保水能力和再饱和膨润土缓冲剂。由于在放置时是不饱和的，预计缓冲层将从主地层吸收地下水，并在这样做时膨胀到放置期间留下的空隙中，为载有核废料的罐提供密封和保护。这使得粘土的膨胀潜力成为评估其作为核废料处置缓冲材料的适用性的关键参数之一。尽管如此，废物产生的高温可能会改变其膨胀特性，损害其执行指定功能的能力，使其容易破裂，从而损害核废物处置库的安全，该项目的目的是研究温度对压实的膨胀行为的影响，MX80膨润土，由于其膨胀和自我修复能力，建议在SKB概念中用作深层地质处置的缓冲剂。拟议的博士项目的范围是：（a）测量MX 80在环境温度和高达85摄氏度的温度下的膨胀潜力;（B）提供关于MX 80的压实特性如何影响其在高温下的膨胀潜力的实验见解;（c）优化MX 80的初始特性以改善其性能。这与优化缓冲器的压实状态和在其放置在沉积孔中期间留下的间隙两者相关联。为此，一个新设计的测土池将投入使用。该设备由EPSRC（EP/J021199/1）提供资金，是一系列设备的一部分，其中包括以下单元：（a）温度控制的固结计;（B）吸力控制的固结计;（c）温度控制的三轴;（d）温度控制的各向同性单元;和（e）一套四个带相对湿度控制的干燥器。该项目是岩土工程部分协调工作的一部分，旨在解决与能源岩土工程相关的具有挑战性的主题。