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

无论是在英国国内还是在国际上，由于核活动产生了大量的放射性废物。原因有很多，从核军备的生产和维护到商业核反应堆的运行等等。这造成了大量和各种各样的废物，需要不同的处置和储存方法，以确保环境和公众的安全。其中一种方法是将高放废物（HLW）固定在陶瓷废物中。选定的废物形式必须在几万年的时间里保持稳定，同时很可能被储存在一个叫做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者，因为它们具有理想的物理和化学性质，可以在很长一段时间内保持。然而，选择陶瓷的一个重要考虑因素是其抵抗辐射引起的损伤的潜力。这主要以α -反冲损伤的形式出现，这最终会导致陶瓷的结晶到非晶态相变，从而导致许多问题，如裂缝和膨胀，从而导致放射性核素在地下储存时被地下水浸出。决定材料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、合成和表征新型陶瓷材料来解决这一问题。A2BO5系列陶瓷允许加入许多锕系元素废料，并且可以根据a和b位阳离子的大小，制造方法，温度和压力采取一系列结构。这是一种很有前途的废物形式，显示出良好的抗辐射损伤潜力。为了快速、系统地研究辐射损伤效应，将采用重离子束注入来加速辐射损伤效应。这将允许确定不同的质量，例如非晶化的临界温度，在该温度下辐射诱导的非晶化速率与再结晶速率相同。这些陶瓷的表征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.