Separation of isotopes by laser excitation

The SILEX process ( SILEX = Separation of Isotopes by Laser Excitation ) is a process for uranium enrichment using the laser technology. It is based on the isotope shift of the absorption spectra of atoms or molecules. Are the spectroscopic conditions suitable, that is, overlap the absorption lines of the isotopes or isotopic compounds sufficiently small and also is a laser of appropriate wavelength and narrow bandwidth available, an isotope- selective excitation is possible.

Development

The method was developed in the 1970s. The uranium hexafluoride containing the gaseous molecules to be selectively excited by a first 235U laser ( for example, a frequency stabilized laser carbon dioxide ) before a fluorine atom is cleaved by a second laser. The resulting solid 235UF5 can be easily filtered from the gas.

After the initial euphoria about the advantages of this method over conventional, established enrichment method, but technical problems, such as presented Corrosion of the equipment out that seemed insurmountable. Most countries withdrew, mainly because of the high costs of further research back.

In Australia, the developments for the industrial application of this method, however, were promoted. The physicist Horst Struve and Michael Goldsworthy founded in 1988 the company Silex Systems Limited.

In November 1996, the license of Silex Systems Limited for the technology exclusively to the United States Enrichment Company ( USEC ) went over so that Australia was not affected in terms of the provisions of the NPT. First test runs were performed in the years 2005 and 2007.

In September 2010, the Authority issued for nuclear energy in the U.S. ( NRC) the company GE Hitachi Nuclear Energy, created from a consortium of corporations General Electric and Hitachi, the approval to build the first plant to enrich uranium using laser isotope separation, in the vicinity of Wilmington, North Carolina. In August 2011, the company Global Laser Enrichment, which had been founded in 2008 by the consortium, the application for the enrichment of uranium to 8% 235U.

Process Description

At atmospheric pressure and a temperature from 56.5 ° C uranium hexafluoride goes by sublimation directly from solid to gaseous state. When cooled below this point again form crystals. Wherein the enrichment procedure is possible at relatively low temperatures, and consumes less energy than other processes for uranium enrichment. However, so far not all the details of the developed method were published in Australia. Used a carrier gas and CO2 laser. CO2 lasers are relatively efficient and inexpensive. The laser has a wavelength of 10.8 microns and is optically enhanced to 16 microns, is the pulse frequency of 50 Hz Thus the laser is in the infrared range. Natural uranium consists of approximately 99.3 % of 238U and 0.7% of 235U. This results in two fractions, one with uranium containing more 235U, and one which contains less 235U than natural uranium. In a single pass, however, only 1 % of the uranium to be processed appropriately so that a plurality of process cycles are required. The minimum electric power for a plant that processes 1 kg 235U is estimated to be 100 kW.

Criticism

Critics such as the German Physical Society (DPG ) and the Carnegie Endowment for International Peace warn of the dangers of new technology, as this allows the production of nuclear weapons would be facilitated and less controllable. Thus, the probability of discovering a uranium enrichment plant is equipped with the new technology, which requires much smaller than the previous systems and also use less energy, less.