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RADIOACTIVE WASTE DISPOSAL |
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One consequence of the generation of electricity through nuclear power, and various other uses of nuclear materials (e.g. medical uses) is the need to dispose of the associated radioactive wastes. This is a very involved process, and in this series of articles we will discuss some of the issues associated with the safe disposal of radioactive wastes. |
Introduction
The disposal of radioactive wastes is a very controversial subject. The controversy arises in part from the fact that some of the wastes will remain radioactive for very long periods of time. For example, the radionuclide U-238 has a half life of 4.5 billion years, and will remain radioactive on timescales of this length and longer. Radioactive wastes generally contain large amounts of U-238, along with numerous other radionuclides with shorter - or even longer - half lives. The question then is how to ensure that such wastes are safely disposed - and remain safe on timescales of hundreds, thousand, millions or even billions of years.
Current consensus around the world is that the most effective way to dispose of the most radioactive of wastes is in purpose-built waste repositories many hundreds of metres below the ground surface. The aim of any radioactive waste disposal repository is to provide the greatest protection to present and future populations from the deleterious effects of the wastes, and deep repositories are seen as the most promising means for achieving this. Such repositories are considered to provide a degree of isolation of the wastes such that they will not pose a radiation hazard at any time in the future.
For wastes that are towards the lower end of the radioactivity scale, simpler concepts can be employed. The Low level Waste Repository (LLWR) in the UK is a "near-surface" repository, and it is used for the disposal of radioactive wastes that are not sufficiently radioactive to require deep disposal. Instead, the wastes at the LLWR are disposed in trenches and vaults that lie a few metres below the ground surface.
In the following articles we will not be discussing near-surface repositories, though many of the ideas apply equally to near-surface repositories.
Disposing of radioactive waste in purpose-built repositories involves much more than just digging a big hole and burying the wastes. For example, the UK company Nirex (now a division of the Nuclear Decommissioning Authority) has been investigating the deep disposal of UK wastes for 30 years now, and has spent billions of pounds in the course of that research. The safe disposal of radioactive wastes is a serious business, and one that is not taken lightly by the nuclear industry.
In the first article we will look at some deep waste repository designs, typical of those that are considered in the UK and overseas. In the second article we will look at what happens to the wastes and associated radionuclides once a repository has ceased operation, and the possible hazards to human populations is discussed in the third article. The fourth article looks at the regulatory and legal requirements, and the final article looks at some features of the performance assessments that are used to assess safety.
I should note that the I work in the radioactive waste industry, and much of my work is done in support of radioactive waste disposal. I accept that many folk have problems with the current ideas on disposal, and I have tried to write an impartial account of the process here. This is in keeping with the ideals of the company I work for, Serco TAS, which stresses the need for its consultants to provide independent and unbiased advice.
Radionuclide Return to the Accessible Environment
Doses and Risks to Future Populations