Glass-Ceramics: Damaging Bubble Formation

Developing improving methods for the safe immobilisation of radioactive nuclear waste is a challenge the world over. There are many options which have been developed based on both glass and ceramics, each of which has advantages and disadvantages, and behaves differently to the effects of radiation damage from alpha decay. This project combines the expertise and talents within the UK and India to develop the next generation of materials capable of safely storing nuclear waste, using glass-ceramics. Glass-ceramics are defined as ceramic particles distributed within a glass matrix, similar to fruit/nut placed in chocolate.

The project will address both model compositions and the effects of radiation damage, from alpha decay, and the formation of helium bubbles within the material, through to real life systems. For example one key question to answer is whether the interface between a ceramic particle and the glass matrix acts as a location where He bubbles can form and act as a stress point which in turn initiates crack formation. Of equal importance is how the interface behaves over time, does it remain sharp or begin to soften, which in itself will impact the long term stability of the material. Such an effect will have profound effect on the mechanical performance over extended periods of time.

The results from this work will extend the applicability of glass-ceramics and extend their use into other areas, while at the same broaden collaboration between India and the UK in the development of nuclear waste storage for the future.

For all nuclear materials the effect of radiation damage, whether the material is used as a waste form, or within a reactor, needs to be understood as it determines the use of a material. Currently there are many models in the literature outlining the effects of radiation damage, and there are also many outlining the effects of gas bubble evolution. However, there are none that describe the effects of radiation damage, and gas bubble formation together, particularly at an interface between an amorphous and a crystalline phase. In combination these effects have disastrous impact on long-term stability, and greater understanding is demanded if their effects are to be alleviated.

The results from this project will help alleviate this gap, and used to form the next generation of improved materials for waste storage. For example, can we add a component which will reduce the likelihood of crack initiation at an interface? This is an important question and not easily answerable, but is one of the issues that impacts future waste form development, particularly in these new materials being proposed. This work directly addresses this question, as ion irradiation has the ability to irradiate materials under a range of conditions allowing the effect of compositional change, or an interface to be studied directly. The results from this work will be used to drive new, and enhanced models for predicting this behaviour, while at the same time provide a mechanism by which current models can be validated, or improved.

During the course of our research, we will work collectively, with the results from this programme being used to not only develop new models but can also be used to valid existing models.The results from this work will be shared in the traditional manner, that is, though publications and conference presentations, and outreach activities. Enhanced public outreach is a goal of this project, for example highlighting the benefits of glass-ceramics, and the linkage between the UK and India can be key in increasing public acceptance of nuclear power. The UK and India partners have extensive experience in this area, for example the outreach programme conducted by PhD students at Sheffield has worked well and helped to increase public acceptance of nuclear power. When coupled with the experiences in India in public acceptance, this programme is designed with outreach in mind.

In addition to this we will, through our advisory board, highlight the results to interested industrial partners, subject to the limitations defined by the India-UK research agreement, for example enhance waste options are of interest to both Sellafield LtD and NNL. Our outputs will also be shared with government organisations such as NIRO (Nuclear Innovation Research Office), NIRAB (Nuclear Innovation and Research Advisory Board) and CORWM (Committee on Radioactive Waste Management) in the UK, who can then use the information obtained to help define the long-term nuclear strategy within the UK. We will also build upon our collective collaborations with other groups worldwide studying similar effects: e.g. at Idaho National Laboratory (INL), Australian Nuclear Science and Technology Organisation (ANSTO), the Institute for Transuranic research (ITU), the Universities of Tennessee (UT), and the Commissariat à l'énergie atomique et aux énergies alternatives (CEA), again within the limitations allowed by the programme.

Finally one key area that we will use to gain a large body of impact is through the enhanced linkage between the UK and India, and development of new collaborative research programmes, coupled with the development of younger researchers. For example during the programme we will attach wherever possible young researchers, whether they be undergraduate or postgraduate, in parallel research projects which can link. Such an exposure can only enhance the impact of such a research project, and lead to further collaborative opportunities.