Nuclear power does not produce polluting combustion gases. So, like renewable energy sources, it could play a key role in helping to reduce global greenhouse gas emissions and in tackling global warming, especially as electricity demand rises in the years ahead. Public faith in nuclear energy took a knock from the accidents at Chernobyl and Three Mile Island, but as plant safety has improved such risks have greatly diminished. Currently, the perceived problem with nuclear energy from an environmental point of view is how to manage its radioactive waste. Solutions do exist, in particular the technique of burying the waste deep below the ground in engineered facilities, known as geological disposal. The challenge is to convince the public of its safety and reliability.
Radioactive waste is an inevitable by-product of the application of ionising radiation, whether it be in nuclear medicine (for diagnosis and treatment), industrial applications (for example, for finding new sources of petroleum or producing plastics), agricultural applications (notably for the conservation of foodstuffs), or of course the production of electricity. The radioactive waste produced by the latter represents less than 1% of the total toxic wastes generated in those countries that use nuclear energy to generate electricity, but at the same time this waste has the highest levels of radioactivity.
In most OECD countries, all short-lived, low- and intermediate-level nuclear wastes, whatever their source, are disposed of using surface or under-ground repositories that are safe for people and the environment during the time that these wastes maintain their radioactivity. These wastes, representing some 90% of total radio-active waste, are conditioned and stored in facilities isolated from the environment by specially engineered barriers. Long-lived and high-level waste, on the other hand, is first deposited in temporary storage facilities, under strict safety conditions, for several decades. It is then usually envisaged that the waste will be placed in a final disposal facility. There is no immediate economic, technical or environmental need to speed up the construction of final disposal facilities for radioactive waste. But from a sustainable development perspective – and if we do not want to pass the burden of finding a permanent solution on to future generations – temporary storage is clearly not a satisfactory solution.
The long-term solution currently preferred by specialists consists of placing the waste in a deep (500 metres below the surface) and stable geological setting, such as granite, clay, tuff and salt formations that have remained virtually unchanged for millions of years. The aim is to ensure that such wastes will remain undisturbed for the few thousand years needed for their levels of radioactivity to decline to the point where they no longer represent a danger to present or future generations. The concept of deep geological disposal is more than 40 years old, and the technology for building and operating such repositories is now mature enough for deployment. As a general rule, the natural security afforded by the chosen geological formation is enhanced by additional precautionary measures. The wastes are immobilised in an insoluble form, in blocks of glass for example, and then placed inside corrosion-resistant containers; spaces between waste packages are filled with highly pure, impermeable clay; and the repository may be strengthened by means of concrete structures. These successive barriers are mutually reinforcing and together ensure that wastes can be contained over the very long term. The waste can be recovered during the initial phase of the repository, and also during subsequent phases, albeit at increased cost. This provides freedom of choice to future generations to change waste management strategies if they wish.
Repositories are designed so that no radioactivity reaches the Earth's surface. Following the precautionary principle, environmental impact assessments spanning 10,000 years analyse worst-case scenarios, including geological and climate changes and inadvertent human intrusion. The assessments maintain that even under those conditions, the impact on the environment and mankind would be less than current regulatory limits, which in turn are lower than natural
The safety of geological disposal has been demonstrated in nature. Until about two thousand million years ago a natural reactor moderated by natural currents of water operated inter-mittently for millions of years at a uranium ore deposit beneath Gabon in Africa. Throughout that time the material produced during the nuclear fission reaction hardly moved from its original location. The first man-made geological disposal facility for long-lived waste started operation in New Mexico, USA in March 1999 and will provide industrial experience. Another partial solution is to reduce the mass of long-lived, high-level waste using a technique known as partitioning and transmutation (P&T). This involves isolating the transuranic elements and long-lived radionuclides in the waste and aims at transforming most of them by neutron bombardment into other non-radioactive elements or into elements with shorter half-lives. Some countries are investigating this option but it has not yet been fully developed and it is not clear whether it will become available on an industrial scale. This is because in addition to being very costly, P&T makes fuel handling and reprocessing more difficult, with potential implications for safety.
Cost is an important issue in radioactive waste management as related to sustainable development. If the nuclear industry did not set aside adequate funds, a large financial burden associated with plant dismantling and radioactive waste disposal would be passed on. In OECD countries, the costs of dismantling nuclear power plants and of managing long-lived wastes are already included in electricity generating costs and billed to end consumers; in other words, they are internalised. Although quite high in absolute terms, these costs represent a small proportion – less than 5% – of the total cost of nuclear power generation.
Deep geological disposal allows present generations to progress without leaving burdens for those of the future, but a main weakness is that although the concept is technically sound, it is rarely socially or politically accepted. The issue is not so much about information provision as understanding the mechanisms that govern the social perceptions of risk. There are many factors that affect such perceptions, such as familiarity with the technology, the degree of uncertainty, the level of control, concern for the consequences, the degree of credibility of the institutions, the decision-making process and the ideas and values of the community in which people live.
Addressing the public's concerns and negotiating acceptable solutions is an important challenge. A decision-making process should be set up step by step, and all the affected groups should be allowed to participate. The role of governments will be crucial in defining this process, and they should act as a source of objective information. They also need to dedicate adequate resources for this purpose, so that public confidence may be won in the scientific solutions being proposed.
• Geologic Disposal of Radioactive Waste in Perspective, OECD, Paris, 2000.
• Stakeholder Confidence and Radioactive Waste Disposal – Workshop Proceedings, Paris, France, 28-31 August 2000, OECD/NEA, Paris, 2000.
• Progress Towards Geologic Disposal of Radioactive Waste: Where Do We Stand?, OECD/NEA, Paris, 2000.
• Confidence in the Long-term Safety of Deep Geological Repositories – Its Development and Communication, OECD/NEA, Paris, 1999.
• Visit the NEA website at http://www.nea.fr
*Jorge Lang-Lenton León is Director of Communication, ENRESA (Spain), Cynthia Picot and Hans Riotte are in the Nuclear Energy Agency (NEA)