Atomic vapor laser isotope separation

Atomic vapor laser isotope separation (AVLIS) is a method by which specially tuned lasers are used to separate isotopes of uranium using selective ionization of hyperfine transitions.

In the largest technology transfer in U.S. government history, in 1994 the AVLIS process was transferred to the United States Enrichment Corporation for commercialization. However, on June 9, 1999 after a $100 million investment, USEC cancelled its AVLIS program.

The AVLIS process provides high energy efficiency comparable with gas centrifuges, high separation factor, and low volume of radioactive waste.

AVLIS continues to be developed by some countries and it presents some specific challenges to international monitoring. Iran is now known to have had a secret AVLIS program. However, since it was uncovered in 2003, Iran has claimed to have dismantled it.

A similar technology, using molecules instead of atoms, is molecular laser isotope separation (MLIS).

The absorption lines of ²³⁵U and ²³⁸U differ slightly due to hyperfine structure; for example, the ²³⁸U absorption peak shifts from 502.74 nanometers to 502.73 nm in ²³⁵U. AVLIS uses tunable dye lasers, which can be precisely tuned, so that only ²³⁵U absorbs the photons and selectively undergoes excitation and then photoionization. The ions are then electrostatically deflected to a collector, while the neutral unwanted uranium-238 passes through.

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