Laser Isotope Separation

Laser isotope separation (LIS) deserves global attention and further research must be done. This is because laser techniques have a number of distinct advantages over traditional ones - such as having a highly selective elementary separation event, low energy consumption, short startup time, and practically a single-stage production (which may economize fuel processing). It is well understood that the energy consumption for many traditional techniques is higher than those for laser methods. The non-laser methods for uranium enrichment, like electromagnetic separation, gaseous diffusion, gas centrifuge, etc., consume energy approximately one or two orders of magnitude higher than the laser methods, which are based on the dissociation by infrared lasers or ionization by coherent (phase difference of successive waves is constant) beams of light in either the ultraviolet or visible spectra Another practical advantage of LIS is that these techniques are carried out with the least amount of environmental contamination, which is particularly important for the separation of radioactive isotopes. The absence of traditional separating elements, such as membranes and plates, increases the potential of laser techniques to such an extent as to minimize the amount of physical contact between an enriched stream and apparatus surfaces. Additionally, the efficiency of traditional methods is usually dependent on particle mass; however, laser techniques can be used for both light and heavy elements. LIS essentially involves two subsequent basic stages.

The first stage is isotope selective excitation, a common element of all laser separation schemes. The second, responsible for the separation process, could be a pure photon interaction or an associated mechanical or chemical contribution.

Today, experts face an important question: which LIS techniques are more likely to convert the expensive multi-stage methods into a low-cost single-stage process? Accordingly, LIS has evolved into a two main branches, namely the MLIS and AVLIS. If you want to learn more, just google it ;)

But I will briefly discuss SILEX - separation of isotopes by laser excitation.

SILEX Technology claims to be “the only third generation laser-based uranium enrichment technology under development in the world,” on the front page of their website. This highly confidential subset of MLIS operates at lower laser energy (<4 eV). The specifications of this laser are not known by the public, however, advancements in diode lasers may point the direction in which GLE (consortium of GE, Hitachi, and Cameco) is going. Analysts indicate that a SILEX system is portable enough to be easily sited in a building the size of a school gymnasium, with power coming from a single diesel generator. Another key strategic advantage of SILEX is the characteristic of having no isolated, revealing thermal or chemical signatures, which would provide intel to outsiders.

“The basis for our approach is laser activation of the magnetic state of an atom, requiring a relatively simple atomic structure. Uranium has a very complex structure, which may not be amenable to this new process. It is perhaps tempting to say that a method for enriching one isotope could also be applied to another. However, each element is unique in its atomic and chemical properties. For example, the starting point for most atomic laser separation projects is to heat the solid material and vaporize it, forming an atomic beam.” According to declassified documents on the laser uranium separation project, it took several years to isolate materials that will not react chemically with hot, metallic uranium. By contrast, many elements, such as calcium or ytterbium, are routinely used in ionic and atomic beams in research laboratories and do not have those problems. Similarly, the atomic structure and required lasers are unique to every atom(hence, laser ‘tuning').

"Lasering the Fuel." The Economist. The Economist Newspaper, 5 Sept. 2015.
References:
"Laser Isotope Separation." Lawrence Livermore National Laboratory. <https://str.llnl.gov/str/Hargrove.html>
Vasaru, Gheorghe. "Avlis-U." <http://www.slideshare.net/gheorghevasaru1/avlis-u>
"Laser Enrichment Methods (MLIS and AVLIS)." Nuclear Regulatory Commission. <http://pbadupws.nrc.gov/docs/ML1204/ML12045A051.pdf>
Rousseau, Denys. "Isotopic Separation by Laser Based Technologies." International Atomic Energy Agency. <https://www.iaea.org/safeguards/symposium/2010/Documents/ PapersRepository/262.pdf>
"Silex Systems Third Generation Laser-Based Uranium Enrichment Technology."
"Safeguards to Prevent Nuclear Proliferation." World Nuclear Association
Serrato, Ruben M. Laser Isotope Separation and the Future of Nuclear Proliferation.