Laser-Based Uranium Enrichment Work Reaches Milestone, Gains Further Funding

By: Yvonne Carts-Powell

Silex Systems Ltd. (Sidney, Australia) has completed a research milestone in its program to develop a laser-based process for enriching uranium. Under the terms of a 1996 deal with United States Enrichment Corp. (USEC; Bethesda, MD), USEC will pay Silex Systems $2.5 million this month, and another $0.25 million later this spring. USEC has the exclusive rights to the commercial use of the proprietary process.

Nuclear power stations produce 16% to 18% of the world's electricity. Uranium for nuclear power plants must be enriched so that the amount of uranium isotope 235 is increased from less than 0.7% to roughly 3% to 5%. Enrichment costs account for about 30% of the fixed costs for nuclear fuel. Currently, uranium is enriched using either gaseous or a gas centrifuge technique. Both methods, however, are inefficient. Gaseous diffusion, which has been in use since the Manhattan Project, is requires a great deal of power and leaves behind contaminated by-products. Both economic and environmental concerns suggest a need to commercialize a more efficient enrichment technology.

The major player in the industry is USEC, which supplies about two-thirds of the enriched uranium used worldwide. USEC uses gaseous diffusion for commercial purposes, but is funding research into alternative methods as well, including both Silex and centrifuge separation techniques.

The Australian company Silex Systems has been developing a technology for separation of isotopes by laser excitation (Silex) since 1992. In addition to uranium enrichment, the proprietary, laser-based process may be useful for silicon and carbon enrichment, which could be used in making semiconductor materials.

What about AVLIS?
Until last June, the U.S. government supported another laser method, atomic vapor laser isotope separation (AVLIS), until it lost funding. AVLIS is still under development in France.

In the AVLIS technique, a laser is tuned to the specific energy necessary to ionize U235 atoms in a vapor of uranium metal. The positively charged ion is then attracted to a negatively charged collection plate, removing it from the vapor. According to Elizabeth Stuckle of USEC, AVLIS requires harsher environmental conditions—specifically higher temperatures—than Silex.

Another disadvantage of the AVLIS technique is that it starts from metallic uranium, rather than the form in which un-enriched uranium is typically supplied: as uranium hexafluoride (UF6).

THE USEC/Silex deal "Although Silex is still at an early stage of development, the results of the research look promising for an economically attractive future enrichment technology,'' said William Bennett, USEC's vice president of Advanced Technology.

Silex's research program has measured key physics parameters that characterize the enrichment performance of the process. Confirmation of these parameters is one of the steps required in the next phase to demonstrate whether the process could likely be scaled up to create commercial quantities of enriched uranium. The next phase involves an engineering study for a pilot plant that will permit more detailed calculations of the economics of the process. Assuming the next phase goes well, Silex will build a pilot plant.

Other possible uses for Silex
The Silex core technology has other potential applications that may prove to be commercially viable. For microelectronics, silicon-28 shows 60% better thermal transmission than normal silicon, therefore possibly enabling silicon devices to be used in applications that are currently limited by heat: possibly allowing chips to run faster or be further miniaturized.

About the author…
Yvonne Carts-Powell is a freelance science and technology writer based in Belmont, MA.