Fusion researcher Robbie Scott claims that waste from nuclear fission plants lasts "for hundreds of thousands of years" (Letters, 20 August).
If he refers to the fission products that result from reprocessing "used" fuel, he ought to know that most of the radioactivity comes from strontium-90 and caesium-137, which have half lives of only 28 and 30 years, respectively. Consequently, the activity dies away after only a few hundred years and after 500 years is only 0.012 per cent of what it was after four years. Although there are some very long-lived elements involved, for that reason they are not very radioactive and it is irresponsible not to point that out.
Marianne Birkby (Letters, 21 August) seems to be confused. Like all thermal generation plants, nuclear plants use, but don't consume, a large quantity of water for cooling purposes. In the UK, they use seawater. But how would a plant continue to "consume" fresh (sic) water after the plant has been decommissioned? Nuclear power plants could play a part in distilling fresh water from seawater in parts of the world short of water.
