Platform for Long-term Experimental Investigation of Alteration in Disposal Environments and Storage - PLEIADES

PLEIADES will establish essential research infrastructure to underpin the development of decommissioning, interim storage and disposal safety cases for radio-materials arising from legacy, new build and future nuclear fuel cycles. It will enable research in 3 key areas of government policy relating to nuclear energy:

1. Geological disposal: The success of HM Government's nuclear decommissioning responsibilities and its future new build ambitions rests upon the successful implementation of policy to deliver a geological disposal facility (GDF) for radioactive waste. It is necessary to demonstrate that post-closure safety of a GDF will be maintained before it can be built. This requires an understanding of long-term corrosion rates and degradation mechanisms of waste, under GDF conditions, which PLEIADES will be uniquely placed to provide.

2. Reduce hazard of legacy nuclear sites: The risks and hazards of decommissioning the UK's nuclear legacy are the most challenging in the world. During decommissioning, radioactive wastes are converted into a form that can be safely stored for many decades. During storage, the waste materials should not change or degrade, however, there are many that are subject to corrosion. The equipment within PLEIADES will have the capability to determine the corrosion processes and rates of such radio-materials, informing safety cases for interim storage and subsequent decisions about future management practice.

3. Accelerate nuclear decommissioning: It was recently announced that the preferred solution to deliver savings of 20% in the £120 billion cost of nuclear decommissioning to the UK taxpayer, by 2030, is the development of at least one Near Surface Disposal (NSD) facility. Disposal of waste in NSD could dramatically reduce decommissioning timescales. Pivotal to its success of this new approach is an appraisal of NSD safety, including models of radioactive waste degradation over the 100s of years of disposal. PLEIADES has the capability to address critical knowledge gaps in corrosion and radionuclide release rates from waste in such facilities and, therefore, to support accelerated implementation of NSD.

PLEIADES will be a unique facility in the UK, enabling research that addresses key gaps in capability that were identified by the academic community and radioactive waste management industry:

> Corrosion in sub-surface disposal conditions: Because radio-materials are highly sensitive to atmospheric conditions it is essential that sub-surface disposal environments are replicated in the laboratory. Only if the correct conditions are maintained during corrosion experiments will meaningful data be obtained. The PLEIADES equipment will enable such research on a wide range of radio-materials, for which is there is no current UK capability.
> Long-term corrosion: A unique aspect of PLEIADES is the capability to establish long-term (decades) corrosion experiments under stable conditions representative of sub-surface environments, giving detailed insight to slow degradation processes. With less than 20y remaining until a GDF will be constructed, the establishment of long-term experiments is essential now, if we are to understand the science behind radioactive waste corrosion.
> Corrosion within a radiation field: Corrosion processes of radio-materials can be significantly influenced by the effects of radiation. These effects are currently poorly understood because there is a paucity of facilities that enable their investigation. PLEIADES will constitute the only UK university facility with capability for analysing highly radioactive materials that create their own radiation field, and the PLEIADES equipment is compatible other user facilities that will enable corrosion experiments to be performed within an external radiation field.