The dissolution of vitrified nuclear wasteforms as a function of groundwater composition

In the UK, vitrified high level radioactive waste (HLW) will be disposed of in a geological disposal facility (GDF), several hundreds of meters below the ground. Ongoing studies are also evaluating the possibility for vitrification of intermediate, and even low-level wastes. While vitrified intermediate level waste glass will also be disposed of in the GDF, low level waste glass may be suitable for disposal at LLWR. In the safety case for both the GDF and LLWR, the release of radioactivity to the geo- and bio-spheres is controlled by the dissolution of glass in groundwater. Therefore, it necessary to assess the dissolution kinetics and mechanisms of relevant glass compositions in a range of ground water solutions.
This project aims to quantify the dissolution kinetics and mechanisms of simulant UK nuclear waste glasses as a function of varying groundwater composition, across the three key stages of glass dissolution. A key advance of this research will be examination of the role of corrosion products in the onset of the so-called "rate resumption", considered to be highly detrimental to the long-term stability of nuclear waste glass under disposal conditions. State-of-the-art flow-through techniques developed at UoS will be used to rapidly (within days to months), and precisely, quantify the effect of pH, Eh and ionic strength on the forward and residual dissolution rates. Dissolution in synthetic groundwater solutions, backfill pore water, under anoxic conditions, will also be investigated using these techniques.

In GREEN we envisage there are potentially Impacts in several domains: the nuclear Sector; the wider Clean Growth Agenda; Government Policy & Strategy; and the Wider Public.

The two major outputs from Green will be Human Capital and Knowledge:

Human Capital: The GREEN CDT will deliver a pipeline of approximately 90 highly skilled entrants to the nuclear sector, with a broad understanding of wider sector challenges (formed through the training element of the programme) and deep subject matter expertise (developed through their research project). As evidenced by our letters of support, our CDT graduates are in high demand by the sector. Indeed, our technical and skills development programme has been co-created with key sector employers, to ensure that it delivers graduates who will meet their future requirements, with the creativity, ambition, and relational skills to think critically & independently and grow as subject matter experts. Our graduates are therefore a primary conduit to delivering impact via outcomes of research projects (generally co-created and co-produced with end users); as intelligent and effective agents of change, through employment in the sector; and strong professional networks.

Knowledge: The research outcomes from GREEN will be disseminated by students as open access peer reviewed publications in appropriate quality titles (with a target of 2 per student, 180 in total) and at respected conferences. Data & codes will be managed & archived for open access in accordance with institutional policies, consistent with UKRI guidelines. We will collaborate with our counterpart CDTs in fission and fusion to deliver a national student conference as a focus for dissemination of research, professional networking, and development of wider peer networks.

There are three major areas where GREEN will provide impact: the nuclear sector; clean growth; Policy and Strategy and Outreach.

the nuclear sector: One of our most significant impacts will be to create the next generation of nuclear research leaders. We will achieve this by carefully matching student experience with user needs.

clean growth - The proposed GREEN CDT, as a provider of highly skilled entrants to the profession, is therefore a critical enabler in supporting delivery of both the Clean Growth agenda, Nuclear Industry Strategy, and Nuclear Sector Deal, as evidenced by the employment rate of our graduates (85% into the sector industry) and the attached letters of support.

Policy and Strategy: The GREEN leadership and supervisory team provide input and expert advice across all UK Governments, and also to the key actors in the nuclear industry (see Track Records, Sections 3.3 & 5.1, CfS). Thus, we are well positioned to inculcate an understanding of the rapidly changing nuclear strategy and policy landscape which will shape their future careers.

Outreach to the wider public: Building on our track record of high quality, and acclaimed activities, delivered in NGN, GREEN will deliver an active programme of public engagement which we will coordinate with activities of other nuclear CDTs. Our training programme provides skills based training in public and media communication, enabling our students to act as effective and authoritative communicators and ambassadors. Examples of such activities delivered during NGN include: The Big Bang Fair, Birmingham 2014 - 2017; British Science Week, 2013 - 2017; ScienceX, Manchester; 2016 - 2018; and The Infinity Festival, Cumbria, 2017.