Atomic vapor laser isotope separation

Atomic vapor laser isotope separation, or AVLIS, is a method by which specially tuned lasers are used to separate isotopes of uranium using selective ionization of hyperfine transitions.^[1][2] A similar technology, using molecules instead of atoms, is molecular laser isotope separation (MLIS).

Natural uranium consists of a large mass of ²³⁸U and a much smaller mass of fissile ²³⁵U. Traditionally, the ²³⁵U is separated from the mass by dissolving it in acid to produce uranium hexafluoride and then using gas centrifuges to separate the isotopes. Each trip through the centrifuge "enriches" the amount of ²³⁵U and leaves behind depleted uranium. In contrast, AVLIS produces much higher enrichment in a single step without the need to mix it with acid. The technology could, in principle, also be used for isotope separation of other elements, which is uneconomic outside specialist applications with current non-laser-based technologies for most elements.

As the process does not require the feedstock to be chemically processed before enrichment, it is also suitable for use with used nuclear fuel from light water reactors and other nuclear waste. At present, extracting ²³⁵
U from those sources is only economical up to a degree, leaving tons of ²³⁵
U still contained in waste products. AVLIS may offer an economic way to reprocess even the fuel that has undergone one cycle of reprocessing using existing methods.^[3]

Due to the possibility of achieving much higher enrichment with much lower energy needs than conventional centrifuge based methods of uranium enrichment, AVLIS is a concern for nuclear proliferation. To date, no commercial-scale AVLIS production line is known to be in use.