Wednesday, May 27, 1998 Published at 05:09 GMT 06:09 UK
Britain's nuclear legacy buried
Servicemen watched the nuclear tests in the 1950s
By BBC Australia correspondent Michael Peschardt:
An unprecedented attempt is being to lock up Britain's nuclear past. In the deserts of South Australia, scientists are reaching the critical stage in their attempt to make safe plutonium left littering the ground after a series of nuclear tests in the 1950s.
A huge network of trenches has been dug to accommodate the contaminated topsoil. But the greatest danger comes from fragments of raw plutonium which are like fine particles of dust. Each one is potentially lethal.
Dr Keith Lokan of the Australian Radiation Laboratory said: "Because plutonium is a lot more radioactive per unit mass - you only need to breath in a microgram, one millionth of a gram of plutonium, to produce a significant dose of radiation."
The test site
The Ministry of Defence planned to use the site for 100 years, but by the mid 1960s it no longer had any use for it.
Ironically the tests posing the gravest risk of contamination now were a series of so-called minor trials during which the plutonium core never fully exploded.
Scientists estimate that if the plutonium was left in its current form it would be potentially deadly for a quarter of a million years.
The clean-up operation
Those involved in the project are confident that the raw plutonium can be made safe once it is buried and specially treated.
Des Davy, a clean-up co-ordinator, said: "The final stage is to pass large amounts of electricity, or electrical energy, into those pits, with a series of graphite electrodes so as to heat it up and finally melt that soil into a molten rock."
This is not the first time a clean up has been attempted - and it is proving more complicated than first anticipated. But the authorities have said that they are not going over budget and will not be asking Britain for any more money. The whole process is due to be completed within the next two years.