AVLIS process

The exact status of the development of the AVLIS process is subject to security classification. It is beHeved that the process is ready for transition to an industrial operator for commercial development. 

Atomic- Vapor Laser Isotope-Separation. Although the technology has been around since the 1970s, laser isotope separation has only recently matured to the point of industrialization. In particular, laser isotope separation for the production of fuel and moderators for nuclear power generation is on the threshold of pilot-plant demonstrations in several countries. In the atomic vapor laser isotope-separation (AVLIS) process, vibrationaHy cooled U metal atoms are selectively ionized by means of a high power (1—2 kW) tunable copper vapor or dye laser operated at high (kHz) repetition rates (51,59,60). 

Atomic systems, in lasers, 74 666-669 Atomic Vapor Laser Isotope Separation (AVLIS) process, 25 416 Atomic weight, 75 748 Atomization, 77 774-775 in spray coating, 7 69-74 technology of, 23 175 Atomizer operation, concerns related to, 23 195... 

Developmenf work continued to further increase the output and reduce the cost of fhe machines while consfruction of the plant proceeded. However, in June 1985, the Department of Energy (DOE) made the decision (after an expenditure of nearly 3 billion) to shut down the centrifuge plant and concentrate on the development of the AVLIS process for uranium enrichment at LLNL. 

The Energy Research and Development Agency (ERDA), the forerunner to the DOE, through the late 1970s to 1981 supported the study of three new experimental processes for uranium enrichment. Two were based upon laser separation, and one on plasma separation. Jersey Nuclear-Avco Isotopes Incorporated (subsidiary of Exxon) and the LLNL worked on atomic uranium vapor. LLNL referred to it as AVUS. The LANL and a group at Exxon Research Laboratories (not connected with Jersey-Avco) worked on molecular UFg. TRW Incorporated pursued research work on a plasma separation process. Union Carbide Nuclear Division (UCC-ND) supported each in their efforts. In 1981, the AVLIS process at LLNL was selected as the process to be developed further and the other processes were subsequently phased out. 

The AVLIS process consists of a laser system and a separator system. The latter contains a vaporizer and a collector. The working medium is metallic uranium that is melted and vaporized to form an atomic vapor stream. The vapor stream flows through the collector where it is illuminated by precisely tuned laser light. The selected atoms become charged by photoionization and are removed from the vapor stream by an electronic field. 

Uranium isotope enrichment by LIS has been exhaustively studied and the conceptual outlines of two separate programs have made their way into the open literature. These methods are multiphoton dissociation of UFe and LIS of monatomic uranium vapor (atomic vapor laser isotope separation, or AVLIS). AVLIS was selected by the United States DOE as the process to be used in its separation plants during the 1980s and 1990s, but, once again due to the present oversupply of separated uranium, the plant has recently been closed. 

Upon the closure of AVLIS, the only remaining laser process on the world stage was (separation of isotopes by laser excitation [SILEX]), a molecular separation process developed by the Australian company Silex Systems Limited. The French had ceased work on their laser program, SILVA, in 2003. 

MLIS uses UFg as its feedstock, thereby fitting more readily into the conventional fuel cycle than AVLIS. There are two steps involved in the MLIS process excitation with infrared lasers and then dissociation with an ultraviolet laser. Gaseous UF mixed with a carrier gas (argon) is expanded through a nozzle that cools the gas to low temperatures. The UF is irradiated by infrared lasers, which selectively excite the LP Fg, leaving the U F unexcited. Photons from an ultraviolet laser then preferentially disassociate the excited U F to form and free fluorine atoms. The U Fj formed in this manner precipitates from the gas as a solid powder which can be filtered from the gas stream. 

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