Atomistic modelling and experimental verification of vitrified matrices for waste encapsulation

The encapsulation of spent nuclear waste and its storage over many years is a crucial aspect of nuclear energy technology. It is vital that this process is reliable and scientifically proven to be stable over the expected lifetime in which the waste remains active. Public confidence in nuclear energy will only be enhanced if this process can be proved to be safe and environmentally sound. However the required storage times for many spent fuel waste forms is so much longer than the 60 years or so that waste has so far been produced by nuclear power that it is not possible to verify this by direct experimental observation.

This proposal is based on developing computer models of the radiation induced structural changes in the encapsulation materials over long time scales. The main materials to be investigated are borosilicate and iron phosphate glasses and there will also be experimental verification of the models for these materials. Borosilicate glasses are typically used but iron phosphate may be a new candidate waste form that could enhance high level waste loading.

Using a combination of computer models and experiments to investigate these encapsulation materials, we will be able to make predictions that will enable engineers to choose the most appropriate materials for long time structural integrity and help boost public confidence in this vital part of nuclear technology.

The project will have two main outcomes: (1) a method for the prediction of how glass materials, used for encapsulation, behave when subjected to radiation damage over long time scales and (2) an assessment of iron phosphate as a potential new material for high level waste storage. In both cases computer modelling and experiment will be closely integrated. The economic impact will be as a result of the project delivering a system for a more efficient use of existing borosilicate glass materials for waste storage, e.g. optimisation of the actinide loading and also the use of a new material which may have a improved loading capability. This might lead to a new industrial manufacturing process for these encapsulation materials.

In terms of impact on Society, the project will stimulate good relations between the UK and India and help develop scientific collaboration with potential outside the nuclear area since many of the techniques have a wider application. In addition by using predictive models we should be able to demonstrate more clearly to a sceptical public, the reliability and safety of nuclear waste storage methods. This should increase the public's support for nuclear energy and make it easier for the UK to meet its carbon emission reduction targets.

In terms of people, we will not only develop the skills of two young researchers (PDRAs) in nuclear technology but there is also an added bonus as two of the sites have agreed to commit PhD studentships on the same topic. Scientists trained in nuclear science and engineering will be increasingly required as nuclear energy expands to reduce the UK's dependence on fossil fuels.

Finally in terms of the advances in scientific knowledge, there will be impact through new computational and numerical methods which will have broad application in materials science as well as an increase in the fundamental understanding of the structure of amorphous glasses and their behaviour after irradiation.