Atomic and Macro-scale Studies of Surface Processes: Towards a Mechanistic Understanding of Surface Reactivity and Radionuclide Binding Mechanisms

In this programme we seek to develop a mechanistic understanding of radionuclide (RN) interactions with mineral surfaces, under conditions likely to exist in a geological disposal facility (GDF).

This proposal describes integrated experimental and multi-scale modelling studies on selected key surfaces which are designed to address fundamental questions on: (i) how the surfaces of candidate materials in an engineered barrier system (EBS) behave in a typical disposal environment; and (ii) the effect of any alteration processes on RN/surface interactions. Crucially, our approach represents fundamental, underpinning scientific research that will provide mechanistic understanding of key RN retardation processes, simulating a range of post-closure RN retardation scenarios on to candidate EBS and natural surfaces. This approach seeks to develop a methodology that is transferrable to other materials and systems. Such a transferrable, approach supports the current generic stage of the UK disposal programme so that methods developed can be used to perform experiments on other materials using other RNs of interest as the UK geological concept progresses. It allows us to perform key experiments and underpin these with mechanistic prediction approaches. By quantifying the energetic and kinetics of reactions we will create a predictive tool for use in developing and revising more accurate field-scale computational models.

The proposal brings together a new, interdisciplinary collaborative team with a range of complementary expertise capable of taking a holistic approach to this complex and challenging issue. Advanced, in-situ surface sensitive experimental techniques will be applied, and developed for hyper-alkaline and radioactive applicability. A key component is to work on real RN materials to provide accurate and unambiguous data for model development.

This work will inform regulatory bodies, have a profound impact on the development of the new GDF safety case, and has implications in a wider scientific context.

This 4 year research project is a collaboration between several universities and national and international laboratories. The overall aim is to develop a mechanistic understanding of radionuclide interactions with mineral surfaces in aqueous alkaline environments. Key outputs will be the development of techniques and methodology for application to radioactive materials; new multi-scale modelling approach to provide predictive capability. The major impacts will be:

i) Economic: the translation of this research from university to government and industry partners will have enormous economic impact. Current studies of the economics of nuclear power have been severely criticised and their findings disputed. Thomas (2005) analyzed a number of studies and concluded that one key difficulty stems from the fact that: "Several of the (input) variables relate to processes which have not been proven on a commercial scale, such as decommissioning, and waste disposal.... all experience of nuclear power suggests that unproven processes could easily cost significantly more than expected. There is therefore a strong risk that forecasts of these costs could be significantly too low." Disposal costs will be high, that much is known with certainty. Our direct work with key radionuclides will have an important economic impact by improving the predictive capabilities of both risk and cost models.

(ii) People: the researchers employed on the project will benefit considerably from the consortium- collaborations, learning new skills and experiencing a range of different research cultures at world leading international institutions. They will be trained in a range of advanced experimental techniques applied to radioactive materials. They will learn project management within a large consortium and have to develop interdisciplinary approaches to complex problems. Through interaction with the NDA and other waste management organisations they will gain an insight into radioactive waste management, risk assessment and the development of safety cases; directly putting their work into a wider context. It will help address the skills gap in the UK nuclear science base.

(iii) Society: this work has the potential to enable accurate development of a safety case for geological disposal; a problem faced in the UK and around the world (as evidenced by our international collaborations). It addresses key issues related to the safe disposal of nuclear waste and the protection of the environment (see below). The safe and transparent disposal of the waste legacy is imperative if public opinion is going to support new build nuclear reactors and so this work has an indirect impact on energy security and reducing CO2 emissions.

(iv) Knowledge: the scientific outputs from this project will be of interest to a large number of stakeholders across the international nuclear sector. In particular in the UK:
-The NDA-RWMD, the organisation tasked with implementing geological disposal of the UK radioactive waste legacy. The RWMD will be responsible for making the safety case for geological disposal. This case will be developed using multiple lines of technical argument to demonstrate that the proposed disposal concept will not carry unacceptable levels of risk, now or in the future. This research will contribute significantly to this objective, in providing high-quality data sets and modelling tools to support engineering and future waste treatment routes.
-The Health and Safety Executive and the Environment Agency, the two government bodies which will regulate the development and operation of the geological disposal facility. These regulators will be responsible to Government for assessing RWMD's disposal safety case. This research will provide new fundamental science and understanding of RN retardation processes in the GDF, to underpin decision-making.

S. Thomas, The Economics of Nuclear Power: Analysis of Recent Studies, (PSIRU), U. Greenwich 2005