Aug. 14, 2003 http://www.newscientist.com/news/news.jsp?id=ns99994056
Giant laser transmutes nuclear waste
A giant laser has cut the lifetime of a speck of radioactive waste from millions of years to just minutes. The feat raises hopes that a solution to nuclear power's biggest drawback - its waste - might one day be possible.
"It is not going to solve the waste problem completely, but it reduces toxicity by a factor of 100. That's an attractive proposition," says Ken Ledingham, at the University of Strathclyde in Glasgow, who led the British and German research team.
The transmutation was performed using the Vulcan laser, which is the size of a small hotel and housed at the Rutherford Appleton Laboratory in Oxfordshire. About a million atoms of iodine-129 were transformed into iodine-128. The half-life of iodine-129 is 15.7 million years, meaning it remains radioactive for an extremely long time. In contrast, the half-life of iodine-128 is just 25 minutes.
Iodine-129 is one of the many radioactive isotopes created when uranium is burnt in a reactor. Currently they all have to be discharged, stored or disposed of by the nuclear industry.
Million billion watts
The Vulcan laser can produce short pulses of enormous power - a million billion watts. Pulses were fired at a small lump of gold, which produced enough gamma radiation to knock out single neutrons from iodine-129, converting it to iodine-128. The results of the experiment will be published by the Journal of Physics D: Applied Physics.
Ledingham says that the same technique could be applied to other radioactive wastes like technetium-99, strontium-90 and isotopes of caesium. But a different process would be required for other long-lived wastes like plutonium and americium.
Nuclear waste can also be transmuted by reactors or particle accelerators. For laser transmutation to challenge these methods, Ledingham says that suitable "tabletop" lasers will have to be developed, which could take 30 years.
But all the approaches use vast amounts of energy. At present, the Vulcan laser would have to be fired 1017 times at the original 46-gram block of iodine-129 to transmute all of the atoms. "You would need to build a number of power stations to transmute the waste from another power station," warns Karl Krushelnick, a laser physicist at Imperial College in London and part of the team.
Even if this major problem could be overcome, other obstacles could block the laser technology from entering commercial use. According to Ian McKinley from the Swiss nuclear waste company, Nagra, the approach assumes that reactor spent fuel will be reprocessed, which separates the waste. But reprocessing is "extremely expensive and increasingly unpopular", he says.
He also points out that dramatic reductions in the half-lives of isotopes inevitably lead to huge immediate increases in the levels of radiation being emitted per second. Initial missions from iodine-128 would be hundreds of billions of times higher than from iodine-129, causing handling problems for nuclear operators.
"It's a nice idea," McKinley told New Scientist, "but I wouldn't buy shares in a company selling this process quite yet."