Continued SILEX concerns

Proliferation concerns remain over uranium laser enrichment.  The so-called SILEX process, short for ‘Separation of Isotopes by Laser Excitation’ might be employed in a planned enrichment facility in Wilmington, North Carolina, possibly within the next five years. Projections suggest that the commercial SILEX plant will have a capacity of between 3.5m and 6m separative work units a year.

Little is known about the process itself. It uses uranium hexafluoride gas. The gas is cooled to separate the resonance peaks of uranium-235 and 238. A laser beam then selectively excites and separates the uranium 235. The laser pulses at a specific wavelength and a precise repetition rate.

SILEX may have smaller power, emissions, and land use footprints than a comparable gas-centrifuge process, leading to smaller production costs. However, with the advantages have come concerns about proliferation. James Acton, a physicist at the Carnegie Endowment for International Peace, comments that such an enrichment package, using perhaps a quarter of the land needed for a conventional site, will naturally appeal to other producers of enriched uranium, including those that wish to keep their activities hidden.

With most of the details of the project remaining hidden behind national security and intellectual property barriers, researchers are unsure of the indicators that could help to pinpoint a clandestine SILEX plant. A letter published last autumn by a panel of experts reasons that ‘Given the great difficulty of detecting laser isotope enrichment facilities, their spread could undermine U.S. non-proliferation efforts and the ability of the International Atomic Energy Agency to confirm the absence of undeclared nuclear activities…’. It is even currently unknown whether SILEX can produce highly enriched uranium. ‘We just don’t know’, says Acton.

Tammy Orr, CEO of Global Laser Enrichment, the GE-Hitachi subsidiary that develops the technology, disagrees. ‘…there are’, she says, ‘a number of ‘signatures’ which enable detection of attempts to develop and deploy this technology,’ One such signature, she argues, could be the pattern of electricity use at a suspected site, which may be different from what is expected at a centrifuge facility.

The Nuclear Regulatory Commission, which is responsible for giving final approval to the project, has decided that it will not conduct a review into the risks of proliferation linked to the process. ‘The NRC has no statutory requirement to perform a ‘non-proliferation assessment’ as part of its licensing review for the proposed GE-Hitachi facility.’ commented David McIntyre, an NRC spokesman, insisting that the license-review process ‘effectively protects against the unauthorized spread of the technology.’ However, the agency’s chairman, Gregory Jaczko, expressed more caution, noting that evaluating the plant in terms of a proliferation risk ‘is certainly well within our authority as a regulator.’

Some argue that the biggest challenge facing a proliferator wishing to use the SILEX process will be to get hold of the source material. Since the SILEX process still uses the same feed material as Gas Centrifuge Enrichment Plants, a country will still need conversion capacity. That said, however, making sure that cheaper and possibly harder to detect methods of enrichment do not find their way down to the bottom rung of the ladder, where they may be picked up by state and non-state actors for reasons of their own will be one of the challenges facing early adopters.

Sources: ‘New Enrichment Technology Offers Detectable “Signatures,” Advocate Says‘ NTI, 2nd August 2010; ‘Agency Forgoes Proliferation Review of New Nuclear Technology, Despite Worries‘ NTI, 30th July 2010; M. D. Laughter, ‘Profile of World Uranium Enrichment Programs—2009‘, Oak Ridge National Laboratory, April 2009; John L. Lyman, ‘Enrichment Separative Capacity for SILEX‘, Los Alamos National Laboratories, undated.