| 3 |
|
-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undisturbed for the few thousand years needed for their levels of radioactivity to decline to the point where they no longer represent a danger to present or future generations.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 background radiation. |