Atomic vapor laser isotope separation
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 of 502.74 nanometers shifts 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.
The AVLIS system consists of a vaporizer and a collector, forming the separation system, and the laser system. The vaporizer produces a stream of pure gaseous uranium.
The laser commonly used is a two-stage tunable pulsed dye laser usually pumped by a copper vapor laser; the master oscillator is tunable, narrow-linewidth, low noise, and highly precise. Its power is significantly increased by a dye laser amplifier acting as optical amplifier. Three frequencies ("colors") of lasers are used for full ionization of uranium-235.
Commercialization and international significance
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.
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.
The history of AVLIS, as recorded in the open refereed literature, began in the early-mid 1970s in the former Soviet Union and the United States. In the US, AVLIS research was mainly carried out at the Lawrence Livermore National Laboratory although some industrial laboratories were early players. Tunable laser development for AVLIS, applicable to uranium, has also been reported from several countries including Australia (1982-1984), France (1984), India (1994), and Japan (1996).
- Australian Atomic Energy Commission
- Chemical reaction by isotope selective laser (CRISLA)
- Gaseous diffusion
- List of laser articles
- Separation of isotopes by laser excitation (SILEX)
- Nuclear fuel cycle
- Nuclear power
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- USEC News Release Cancelling AVLIS
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- Laser isotope separation uranium enrichment
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- Laser Isotope Separation page at LLNL