Performance of aged cement grouts for encapsulating radioactive wastes

该博士项目的总体目标是深入了解在与储存库相关的条件下，由于NRVB和废旧灌浆之间的长期相互作用而发生的化学、微观结构和物理变化。我们将通过一种新的方法来实现这一点，该方法将热力学建模与定量微结构分析和质量传输表征相结合。这将产生丰富的数据集，补充和扩展先前研究的工作。最终，产生的新知识将为英国地质处置设施关闭后的安全案例提供信息和加强。研究将在帝国基础设施材料中心内进行，并由EPSRC核能未来CDT提供博士培训。这项研究包括三个相互关联的技术工作包，这些工作包将应用一系列先进的建模和实验表征技术。我们将使用热力学模型[2，3]来获得对NRVB-灌浆系统长达10年的老化的完整化学了解，并确定它们在100多年或更长时间老化时的长期化学和指示性物理特性(例如孔隙率)。我们还将在块体和界面区域进行定量显微镜[4]、孔结构/溶液表征和微观力学研究。这将提供对微观结构梯度(孔结构、微裂纹)、固相组合、微观机械性能和孔溶液化学的全面了解。最后，我们将通过测量水泥浆液在完全饱和和部分饱和条件下的质量传输阻力(渗透、扩散、吸收、传导性)来评估其完整性[5]。微观结构数据将用于补充热力学模型和质量传输特性，以形成预测关系。这将使我们能够评估长期热液储存对废旧灌浆回填系统屏障性能的影响。

The overarching aim of this PhD project is to develop a deep understanding of the chemical, microstructural and physical changes that occur due to long-term interactions between NRVB and wasteform grouts under repository relevant conditions. We will achieve this via a novel approach that combines thermodynamic modelling with quantitative microstructural analysis and mass transport characterisation. This will produce a rich dataset that will complement and extend the work from previous studies. Ultimately, the new knowledge generated will inform and strengthen the post-closure safety case of the UK Geological Disposal Facility.The research will be carried out within the Imperial Centre for Infrastructure Materials with PhD training provided by the EPSRC CDT in Nuclear Energy Futures. The research consists of three interconnected technical work packages that will apply a range of advanced modelling and experimental characterisation techniques. We will use thermodynamic modelling [2, 3] to obtain a complete chemical understanding of the NRVB-grout systems up to ten years of ageing, and determine their long-term chemistry and indicative physical properties (e.g. porosity) at ageing times of 100s years and beyond. We will also perform quantitative microscopy [4], pore structure/solution characterisation and micromechanical studies at the bulk and interface regions. This will provide comprehensive understanding of microstructural gradients (pore structure, microcracking), solid phase assemblage, micromechanical properties and pore solution chemistry. Finally, we will evaluate the integrity of the cement grouts by measuring their resistance to mass transport (permeation, diffusion, absorption, conductivity) in fully saturated and partially saturated conditions [5]. The microstructural data will be used to complement thermodynamic modelling and mass transport properties to form predictive relationships. This will allow us to assess the effects of long-term hydrothermal storage on the barrier performance of wasteform grout-backfill systems.