Tuesday, August 23, 2011

Briefing: Security fears over laser-enriched uranium

Plain to see (Image: 2010 DigitalGlobe)
Plain to see (Image: 2010 DigitalGlobe)

It's pretty hard to disguise the fact you are enriching uranium, whether for use in nuclear power stations or bombs. Now a method that uses lasers to complete the process could make it more efficient – and easier to hide.
General Electric and Hitachi are joining forces to build a laser facility in Wilmington, North Carolina, powerful enough to produce more than 1000 tonnes of enriched fuel every year.

But could the benefits of laser enrichment – its efficiency and low power requirements – also be its biggest drawbacks?

How does laser enrichment work?

The difference in mass between uranium-235 and the heavier uranium-238 causes small shifts in the wavelengths at which they absorb light. Lasers can be built to emit a narrow range of wavelengths that are absorbed by U-235 but not by U-238. Once the U-235 has become excited, it can be easily separated from the unexcited U-238, typically by a chemical reaction.

What's so good about using lasers?

Conventional enrichment techniques require large amounts of energy to increase the concentration of U-235 from its natural abundance in rock of 0.7 per cent to the roughly 3.6 per cent needed for use in light-water reactors, or the 20 per cent used in fission bombs. Laser techniques promise much better results because they can better select U-235 atoms, meaning far less power is required. However, the details of the process have not been made public.

If it's so good, why is it only being suggested now?

The idea was first mooted as a possibility in the 1960s, and the US began major projects in the 1970s but the technology proved impractical at the time. The current approach was developed only 10 years ago by an Australian company called Silex.General Electric-Hitachi have now licensed Silex's technology. The original process was hampered by inefficient lasers but the fact that GE-Hitachi are prepared to go ahead with a full-scale plant suggests they have developed a more efficient laser.

Why is the idea so controversial?

A key concern is that the high efficiency of a laser enrichment process would reduce energy requirements, allowing a uranium enrichment plant to be smaller and more distant from power sources. That would make it harder to detect using satellite imagery. Such a small plant could also be used to make enriched uranium for atomic bombs – with little chance of being spotted.

What happens next?

The US Nuclear Regulatory Commission is scheduled to review the proposal on 30 June 2012. If the NRC approves the plan, a joint venture called Global Laser Enrichment would build the plant in six stages, eventually reaching a capacity of 6 million work units, a standard measure of enrichment capacity. If the product was standard-grade reactor fuel, the facility could produce more than 1000 tonnes a year.


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