Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: therodgers21 on 05/10/2008 11:16:45
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therodgers21 asked the Naked Scientists:
Is there any research being done of atomic waste disposal? Why is it waste if it is still radioactive?
What do you think?
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There are grades of waste products from the nuclear industries. Most is called low level waste and is often made up of objects, masks, clothing etc. which may have come into contact with radioactive material. The contaminated material itself is not radioactive but there may be small particles of radioactive material present which would be a hazard to health, especially if ingested.
The main waste from nuclear power stations is the fissionable material used to create the heat to ultimately drive the turbines. It gradually becomes less effective with time as it uses up its nuclear energy. It does not just stop becoming radioactive but just becomes inefficient to use. This material is still highly radioactive and has to be kept, and kept safely, for a long time.
This nuclear fuel can, and is, reprocessed to re-concentrate the most radioactive parts to allow it to be re-used efficiently again. This process does not achieve 100% separation though, so the waste here is still radioactive. This process is also used to separate different elements, such as Plutonium, as by-products.
There are other radioactive waste products from various other industries, including medical, which also need care in disposal.
A simple answer is that the material does not stop being radioactive, it just gets less and less. The amount it gets less is governed by the half-life which is a measure of how long it takes for the radioactivity to halve in strength (actually the time it takes for half the atoms' nuclei in a given sample to decay). Depending on the material this can take from a tiny fraction of a second to many millions of years.
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What graham.d said - in short, it's too radioactive for our health but not radioactive enough for economical energy production.
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Early nuclear power stations were thinly disguised plants for producing Plutonium for bombs!, little regard was paid to the eventual disposal of waste.
Now that Plutonium is considered of little use more care is taken in the design of power reactors to reduce the generation of radioactive waste.
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There's another aspect to this. Many things are radioactive but only a few have the right properties to be used as nuclear fuel. Even uranium comes in 2 (major) types and it's only the rare one that can be used in a reactor.