Developing technology and specifications for metakaolin-based geopolymers as robust and promising stabilisers for fuel debris removal

东京电力公司福岛第一核电站和塞拉菲尔德核电站过去和正在进行的退役和清理作业产生了大量复杂的放射性废物流。这包括固体燃料碎片废物碎片，其主要包括熔融堆芯混凝土相互作用产物，其包括各种材料，例如金属合金、氧化物和硅酸盐，以及含有细颗粒或胶体的浆料和沉积物，其以各种方式富含金属碳酸盐、氧化铁和/或硫酸钡。因此，迫切需要新的固化和稳定方法来安全处置这些废物流。该项目将使用煅烧粘土作为天然资源，设计地质聚合物粘合剂，含硼和不含硼作为中子吸收剂，为日本和英国的长期管理和处置降解燃料和污染废物提供强大且面向未来的废物胶结基质。这将扩大配方范围，以增加废物装载量，并与传统水泥无法有效处理的废物兼容。地质聚合物水泥是通过碱源（“活化剂”）与“前体”粉末之间的化学反应生产的，碱源通常以水溶液形式提供，前体粉末为反应过程提供硅酸盐和铝酸盐。英国和日本的技术和路线图出版物都强调地质聚合物水泥在处理和处置各种有问题的废物方面具有很高的潜力。特别地，使用煅烧粘土作为主要前体的地质聚合物生产已经被确定为提供了作为废物调理基质的优异技术性能的可能性，在新鲜和硬化状态下可控，同时消除核工业对传统水泥粉的依赖，这种传统水泥粉在未来几十年将变得越来越稀缺。我们将确定和优化地质聚合物粘结剂配方，粘土衍生的和其它前体的性质和特性的变化，包括容易制造（包括所需的流动特性，例如粘度、屈服应力、受控的触变性和流动保持性）、放射性核素包封（阳离子和阴离子放射性核素）和复杂废物流（例如固体废物碎片和浆料/沉积物）的包封。这将支持使用地质聚合物作为水泥工具包的关键部分，以满足英国，日本和全球其他国家的修复和退役需求。该项目与英国和日本有着密切的双边联系，结合了两所大学、日本原子能机构（日本）和塞拉菲尔德有限公司（英国）的专业知识。

Past and ongoing decommissioning and cleanup operations at both the TEPCO Fukushima Daiichi Nuclear Power Plant and Sellafield site has generated significant quantities of complex radioactive waste streams. This includes solid fuel debris waste fragments comprising mainly molten core concrete interaction products, which include a variety of materials such as metallic alloys, oxides, and silicates, and slurries and sediments containing fine particles or colloids, which are variously rich in metal carbonates, ferric oxide, and/or barium sulphate. New solidification and stabilisation methods are therefore urgently required to enable safe disposal of these waste streams.This project will use calcined clays as natural resources to engineer geopolymer binders, with and without boron as a neutron absorbent, to provide a robust and future-proof waste cementation matrix for long-term management and disposal of degraded fuels and contaminated wastes in Japan and the UK. This will broaden the formulation envelopes to increase waste loading and compatibility with wastes that cannot be effectively treated by conventional cementation.Geopolymer cements are produced via the chemical reaction between a source of alkalis (the "activator"), which is usually supplied as an aqueous solution, and a "precursor" powder that supplies silicate and aluminate for the reaction process. Geopolymer cements have been highlighted in technical and road-mapping publications in both the UK and Japan as offering very high potential for use in the treatment and disposal of diverse and problematic wastes. In particular, geopolymer production using calcined clays as the main precursor has been identified as offering the possibility for excellent technical performance as a waste conditioning matrix, controllable in the fresh and hardened states, while removing the reliance of the nuclear sector on conventional cementitious powders that will become increasingly scarce in the coming decades.We will identify and optimise geopolymer binder formulations that are robust to variations in the nature and characteristics of clay-derived and other precursors, including in terms of easy manufacturing (including desirable flow characteristics such as viscosity, yield stress, controlled thixotropy, and flow retention), radionuclide encapsulation (both cationic and anionic radionuclides), and encapsulation of complex waste streams such as solid waste fragments and slurries/sediments. This will underpin the use of geopolymers as a key part of the toolkit of cements that are needed to meet the remediation and decommissioning needs of the UK, Japan, and other countries worldwide. The project has strong bilateral UK and Japan links, incorporating expertise from both universities and the Japan Atomic Energy Agency (Japan) and Sellafield Ltd. (UK).