Radioactive waste is produced at all stages in the nuclear fuel cycle, requiring the development of technologies for its safe management and disposal at each step. This means isolating or diluting the waste, so that the concentration of any radionuclides, and the rate of their release into the biosphere, is rendered harmless. The safe and effective management of nuclear waste materials is an issue that resonates with the public, and technologies that increase the effectiveness of nuclear waste management will play a key role in winning public support for nuclear to continue its role in the decarbonisation of the European energy system.
Radioactive waste comes in different forms, from exempt and very low level waste (VLLW) to high-level waste (HLW). VLLW waste contains small amounts of mostly short-lived radioactivity, does not require shielding during handling and transport and is suitable for shallow land burial. Intermediate-level waste (ILW) contains higher amounts of radioactivity and requires some shielding. HLW, however, accounts for over 95% of the total radioactivity produced in the process of electricity generation and is highly radioactive and hot, and so requires both cooling and shielding. Each year, nuclear power generation facilities worldwide produce about 200,000 m3 of low- and intermediate-level radioactive waste and about 10,000 m3 of high-level waste, including used fuel designated as waste.1
There is international scientific consensus that the disposal of HLW in deep geological formations is an acceptable and safe method of long-term management. The 2009 report Geological Disposal of Radioactive Waste: Moving towards Implementation produced by the Joint Research Centre, the European Commission’s in-house science service, found that scientific understanding of the processes relevant for geological disposal is sufficiently developed to proceed with step-wise implementation.2 This conclusion was confirmed at a Symposium on the Safety Case for Deep Geological Disposal of Radioactive Waste, organised by the Nuclear Energy Agency in co-operation with the European Commission and the International Atomic Energy Agency, at which it was agreed that a clear understanding of the technical components of a safety case already exist. According to the Symposium report, as the deep geological repository programme evolves in the coming decades, the safety case will undergo a number a iterations during which the “robustness of the disposal solution has to be improved, unexpected findings have to be addressed and the safety case has to be strengthened, leading to increased confidence in the safety of the disposal solution.”3
Photograph by W. Eberhard Falck
Geological disposal involves isolating radioactive waste deep inside a suitable rock volume to ensure that no harmful quantities of radioactivity ever reach the surface. Suitable geological formations include clay, salt, and crystalline rock strata or deposits that have remained geologically stable for millions of years and are likely to remain so for similar periods in the future. The waste is contained inside multiple barriers to provide long-lasting protection. These barriers, both engineered and natural, work together to provide effective containment. The barriers include the form of the radioactive waste itself4, the container in which the waste is packaged, engineered seals such as a buffer of backfill material that fills the space between the container and the rock, and a geology capable of providing a high level of long-term isolation and containment without the need for maintenance.
According to the JRC report, scientific and regulatory cooperation within the EU will ensure a Europe-wide harmonized level of scientific understanding and regulatory oversight of deep geological storage. The report cites the EC’s role in the development of deep storage technology as being to provide a policy framework and supply R&D funding. In terms of policy support - in its Strategic Energy Technology Plan (SET-Plan) the EC identifies maintaining “competitiveness in fission technologies, together with long-term waste management solutions” as key technology challenge.5 During 2006-2007 a feasibility study called Co-ordination Action on Research, Development and Demonstration Priorities and Strategies for Geological Disposal (CARD) was carried out with the financial support of the European Commission. CARD looked into establishing a technology platform for deep geological disposal and led to the Implementing Geological Disposal of Radioactive Waste Technology Platform (IGD-TP) being formally launched on November 12, 2009. According to the IDG-TP vision statement, the first geological disposal facilities for spent fuel, high-level waste, and other long-lived radioactive waste will be operating safely in Europe by 2025. However, Finland plans to start operating its first-of-a-kind deep geological disposal facility for spent fuel in the early 2020s. A European Council Directive6 from 2006 called for emphasis in Euratom research to be placed on R&D for all remaining key aspects of deep geological disposal. Another Directive followed in 2011, establishing a Community framework for the responsible and safe management of spent fuel and radioactive waste. This Directive recognised that deep geological disposal currently represents the safest and most sustainable option for the management of high-level waste and called on Member States to include planning and implementation of disposal options in their national policies.
With respect to the funding of R&D activity, under its Seventh Framework Programme (FP7) the European Commission has financed a number of projects that aim to increase the safety of deep geological storage of nuclear waste. These include the Fate of Repository Gases (FORGE)7 project, which has set itself the task of reducing some of the uncertainties associated with gas migration in a radioactive waste repository context. The project will play a key role in enhancing and developing European expertise in gas migration, ensuring global leadership in this fast developing area of science. The project will generate new high-quality data for future prediction of repository performance and assist in the assessment of the long-term evolution of potential geological barriers. Another FP7-financed project - Full-Scale Demonstration of Plugs and Seals (DOPAS)8 - is involved in the development of technology to test plugging and sealing systems for geological disposal facilities, and addresses the design basis and reference designs for plugs and seals. The project focuses on shaft seals for salt rock and tunnel plugs for clay and crystalline rock, with five different demonstration experiments, at different stages of development, currently underway in Sweden, France, Finland, the Czech Republic and Germany.
This policy support and research funding has established deep geological disposal as a promising solution for the management of HLW from Europe’s nuclear power sector. Ongoing European research in this field will continue to underpin this technology by augmenting the safety and reliability of this disposal solution on one hand, and increasing stakeholder confidence and public acceptance on the other, thereby helping to secure nuclear power’s role in Europe’s future low-carbon energy sector.
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4 For example, HLW that is initially in liquid form is converted into a durable solid before storage.