Plasma Separation Uranium Enrichment
The plasma separation process (PSP) has been studied as a potentially more efficient uranium-enrichment technique that makes use of the advancing technologies in superconducting magnets and plasma physics. In this process, the principle of ion cyclotron resonance is used to selectively energize the 235 U isotope in a plasma containing 235 U and 238 U ions. A feed plate of solid uranium serves as the source of neutral uranium atoms. These atoms are vaporized by bombarding the plate with energetic ions in a process called sputtering. A microwave antenna located in front of the plate energizes free electrons which collide with neutral uranium atoms in the vapor sputtering off the plate. This in turn displaces electrons from the uranium atoms and produces a plasma of 235 U and 238 U ions.
The plasma is subjected to a uniform magnetic field along the axis of a cylindrical vacuum chamber as the plasma flows from source to collector. The magnetic field is produced by a superconducting magnet located around the outside of the chamber. The high-strength magnetic field produces helical motions of the ions, with the lighter 235 U ions spiraling faster and having a higher ion cyclotron frequency than the heavier 238 U ions. As the ions move toward the collector, they pass through an electric field produced by an excitation coil oscillating at the same frequency as the ion cyclotron frequency of the 235 U ions. This causes the helical orbit of the 235 U ions to increase in radius while having minimal effect on the orbit of the heavier 238 U ions. The plasma flows through a collector of closely spaced, parallel slats, the physical appearance of which roughly resembles a venetian blind. The large-orbit 235 U ions are more likely to deposit on the slats, while the remaining plasma, depleted in 235 U, accumulates on an end plate of the collector. PSP is a batch process that would require several stages to produce HEU from natural feed.
The only countries known to have had serious PSP experimental programs are the United States and France. PSP became a part of DOE's Advanced Isotope Separation research and development program in 1976, but development was dropped in 1982 when AVLIS was chosen as the advanced technology of choice. The French developed their own version of PSP, which they called RCI. Funding for RCI was drastically
reduced in 1986, and the program was suspended around 1990, although RCI is still used for stable isotope separation.
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