Design, synthesis and characterisation of ceramic wasteforms for radioactive waste immobilisation.

有大量的放射性废物，作为核活动的产物产生，在英国国内和国际上。其起源有很多，从核武器的生产和维护到商业核反应堆的运行等等。这就产生了大量和各种各样的废物，需要有不同的处置和储存方法，以确保维护环境和公众的安全。一种这样的方法是将高放废物（HLW）固定在陶瓷废物形式中。一种选定的废物形式必须在数千年内保持稳定，同时可能被储存在一个称为地质处置设施的地下设施中。为此，陶瓷是一个有前途的候选人，由于其理想的物理和化学性能，保持了很长一段时间。然而，选择陶瓷的一个重要考虑因素是其抵抗辐射诱导损伤的潜力。这主要是以α反冲损伤的形式出现的，最终会导致陶瓷的结晶相转变为非晶相，从而导致许多问题，如裂纹和膨胀，从而导致地下储存时放射性核素被地下水浸出。决定抗辐射损伤能力的两个重要品质是材料的晶体结构和化学成分。为此，该项目将寻求设计，合成和开发新的陶瓷材料来解决这个问题。A2BO5系列陶瓷允许掺入许多锕系元素废物，并可以根据A和B位阳离子尺寸、制造方法、温度和压力呈现一系列结构。这是一种有前途的废物形式，显示出良好的抗辐射损害潜力。为了快速、系统地研究辐射损伤效应，将采用重离子束注入加速辐射损伤效应。这将允许确定不同的质量，例如非晶化的临界温度，即辐射诱导的非晶化速率与再结晶速率相同的温度。这些陶瓷的特性将通过不同的方法进行，包括扫描电子显微镜和透射电子显微镜，X射线衍射和X射线吸收光谱。

There is a significant amount radioactive waste, generated as a product of nuclear activities, both domestically here in the UK and internationally. The origins are many, ranging from the production and maintenance of nuclear armaments to the operation of commercial nuclear reactors, amongst others. This has created a large volume and variety of waste, which necessitate distinct methods of disposal and storage in order to ensure that the safety of the environment and public are upheld. One such method is to immobilise High Level Waste (HLW) in a ceramic wasteform. A chosen wasteform must be stable for many 10's of thousands of years, whilst likely being stored in an underground facility called a Geological Disposal Facility. To this end, ceramics are a promising candidate for HLW due to their desirable physical and chemical properties that are maintained over long period of times. However, an important consideration for the choice of ceramic is its potential to resist radiation induced damage. This predominantly comes in the form of alpha-recoil damage, which can eventually cause a crystalline to amorphous phase transition of the ceramic leading to many issues such as cracks and swelling, which consequently leads to the leaching of radionuclides by groundwater when stored underground.Two important qualities that determine radiation damage resistance are the crystal structure and chemical composition of a material. To that end, this project will look to design, synthesise and characterise novel ceramic materials to address this issue. The A2BO5 family of ceramics allow for the incorporation of many actinide wastes and can take on a range of structures depending on the A and B-site cation sizes, fabrication methods, temperature and pressure. This is a promising wasteform that shows a good potential for resistance to radiation damage. To rapidly and systematically study the effects of radiation damage Heavy Ion Beam implantation will be used to accelerate the effects of radiation damage. This will allow for different qualities to be determined, such as the Critical Temperature of Amorphisation, the temperature at which the rate of radiation induced amorphisation is the same as the rate of recrystallisation. Characterisation of the these ceramics will be carried out through different methods, including Scanning Electron Microscopy and Transmission Electron Microscopy, X-Ray Diffraction and X-Ray Absorption Spectroscopy.