SILEX process

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The SILEX process (SILEX = Separation of Isotopes by Laser Excitation) is a process for uranium enrichment with the help of laser technology . It is based on the isotope shift of the absorption spectra of atoms and molecules. Are the spectroscopic conditions suitable, i. H. if the absorption lines of the isotopes or isotope compounds overlap sufficiently little and if a laser of suitable wavelength and narrow band is available, an isotope-selective excitation is possible. The excited atoms or molecules can then be physically or chemically separated from the unexcited ones.

development

The process was developed back in the 1970s. The molecules 235 U contained in the gaseous uranium hexafluoride should be selectively excited by a first laser (for example a frequency-stabilized carbon dioxide laser ) before a fluorine atom is split off by a second laser. The resulting solid 235 UF 5 can easily be filtered out of the gas.

After initial euphoria about the advantages of these processes over conventional, established enrichment processes, technical problems arose, e.g. B. Corrosion on the equipment, which seemed insurmountable. Most countries withdrew from further research, mainly because of the high costs.

In Australia , however, the developments for the large-scale application of this process were advanced. The physicists Horst Struve and Michael Goldsworthy founded the company Silex Systems Limited in 1988 .

In November 1996 the license of Silex Systems Limited for the technology was transferred exclusively to the United States Enrichment Company (USEC), so that Australia was no longer affected with regard to the provisions of the Nuclear Non-Proliferation Treaty . The first test runs were carried out in 2005 and 2007.

In September 2010, the authorization granted regulatory authority for nuclear energy in the USA (NRC) the company GE Hitachi Nuclear Energy , born of a consortium of corporations General Electric and Hitachi , permission to build the first plant to enrich uranium using laser isotope separation , near Wilmington , North Carolina. In August 2011 the company Global Laser Enrichment , which was founded by the consortium in 2008, submitted the application for the enrichment of uranium to 8% 235 U.

Process description

At normal pressure and a temperature of 56.5 ° C or more, uranium hexafluoride changes directly from the solid to the gaseous state by sublimation . When cooling below this point, crystals form again. This enables the enrichment process at relatively low temperatures and uses less energy than other uranium enrichment processes. Not all details of the process developed in Australia have been made public. A carrier gas and CO 2 laser are used . CO 2 lasers are relatively efficient and inexpensive. The laser has a wavelength of 10.8 μm and is optically amplified to 16 μm, the pulse frequency is 50 Hz. The laser is therefore in the infrared range . Natural uranium consists of about 99.3% of 238 U and 0.7% of 235 U. There are two fractions, one with uranium, which contains more than 235 U, and one that contains less than 235 U than natural uranium . In one pass, however, only 1% of the uranium is processed accordingly, so that several process cycles are required. The minimum electrical power required to process 1 kg 235 U within 8 days is estimated at 100 kW.

Uranium hexafluoride crystals in a glass ampoule

criticism

Critics such as the German Physical Society (DPG) and the Carnegie Endowment for International Peace warn of the dangers of the new technology, because it makes nuclear weapons production easier and less controllable. With the new technology, which is much smaller than the previous plants and also requires less energy, the probability of a uranium enrichment plant being discovered is also lower.

Individual evidence

  1. ↑ JW Eerkens: Spectral Considerations in the Laser Isotope Separation of Uranium Hexafluoride , in: Applied Physics , 10/1976, pp. 15-31; doi : 10.1007 / BF00929525 .
  2. ^ Cheap fuel for nuclear power plants , Die Zeit , June 13, 1975, No. 25.
  3. ↑ Enriching uranium with lasers - A new system is to supply 42 million households in the USA with more compact, faster and cheaper electricity. In: Welt am Sonntag . dated August 28, 2011.
  4. ↑ PhysikKonkret No. 11, March 2012: SILEX Risk of Uranium Enrichment
  5. ↑ zeit.de. "All alarm bells should ring for arms controllers"
  6. ↑ Silex Systems Ltd: New Laser Technology for Uranium Enrichment ( Memento of May 14, 2007 in the Internet Archive ), (English)
  7. ↑ False Lessons from the Cold War . In: Technology Review of January 4, 2012.
  8. ↑ Report in the New York Times, August 21, 2011
  9. ↑ fas.org: Enrichment Separative Capacity for SILEX (PDF; 423 kB), (English)
  10. ↑ Report on Australian television from August 1, 2013, accessed on August 2, 2013 (English)