Isotope separation by selective laser‐assisted repression of condensation in supersonic free jets

Abstract

Separation of gaseous molecules in supersonic free jets by laser‐assisted selective condensation repression is reviewed. It is shown to have evolved from Becker's pre‐laser “Nozzle Separator” concept of 1956 by simple addition of a laser. Although useful to separate mixtures of dissimilar gases, the technique has mostly been applied to isotope separation. To enrich iSF6 for example, SF6 mixed with an inert carrier gas G is expanded through a nozzle into a low‐pressure chamber, where it forms a supersonic jet and creates van der Waals hetero‐ or homodimers SF6:G and SF6:SF6 if T < 150 K. By coaxial or cross irradiation of the free jet with a tunable laser, dimerization of selectively excited jSF6 is prevented. As radial out‐of‐the‐jet‐core diffusion depends on molecular mass, nondimerizable laser‐excited jSF6 monomers enrich the background “rim” gases, which are separated by a skimmer from much heavier nonexcited iSF6:G and iSF6:SF6 dimers in the jet's core. © 2010 American Institute of Chemical Engineers AIChE J, 2010

Numerical study of gas mixture separation in curved nozzles

“…However, at very low pressures the Knudsen number approaches unity, invalidating the continuum hypothesis. In this range, particle dynamics methods can be of interest to study the transition to the free molecular regime, and in particular the influence of clusters formations in aerodynamic molecular separation [26].…”

“…Recently, there has been a renewed interest to use the current computational capabilities in gas separation processes of multicomponent flows [13][14][15], including laser assisted aerodynamics [26]. For curved nozzles, the numerical modeling has been proposed in the 80's by Vercelli [7] who used a finite difference scheme to solve the isotopic separation of UF 6 ; but otherwise there are no further reports in the open literature.…”

A Proliferation Assessment of Third Generation Laser Uranium Enrichment Technology

“…9 The general physical concept involves the laser excitation of a vibrational mode in 235 UF 6 molecules diluted in a carrier gas, which results in two forces that cause different migration rates between excited 235 UF 6 ( 235 UF 6 * ) and 238 UF 6 away from the core of an expanding supersonic free jet. 10 This allows the partial separation of 235 UF 6 before the gas condenses.…”

“…A conservative estimate of β = 1.5 to 2.5 for third generation condensation repression laser isotope separation is given by Eerkens and Kim (a similar estimate not taking into account the dynamic of free jet expansion is provided in the online supplement). 42 Values of β ∼ 2 are likely underestimates, as they do not dynamically model the change in 235 UF 6 migration rates to the rim of the free gas jet as its pressure lowers from expanding and cooling, thereby increasing β. Michael Goldsworthy, the CEO of Silex Systems Ltd., has claimed that the enrichment factor for SILEX is between 2 and 20. 43 These enrichment factors are much higher than for typical gas centrifuges and gaseous diffusion systems.…”

Low energy methods of molecular laser isotope separation

“…£ ÖÍÂÊÂÐÐÞØ ÏÇÕÑAEÂØ ËÔÒÑÎßÊÖÇÕÔâ ÐÇÒÑÔÓÇAEÔÕÄÇÐÐÑ ÓÂÊÐËÙ ÏÇÉAEÖ ÏÂÔÔÂÏË ËÊÑÕÑÒÑÄ ÐÇAEÇÎâÜÇÅÑÔâ ÖÓÂÐÂ-238 Ë ÓÂÔÜÇÒÎâÇ-ÏÑÅÑ ÖÓÂÐÂ-235. ÂÊÇÓÐÞÇ ÏÇÕÑAEÞ ÓÂÊAEÇÎÇÐËâ ËÊÑÕÑÒÑÄ ÖÓÂРÑÔÐÑÄÂÐÞ Ð ÓÂÊÎËÚËË Ä ÔÒÇÍÕÓÂØ ÒÑÅÎÑÜÇÐËâ ÎÂÊÇÓÐÑÅÑ ËÊÎÖÚÇÐËâ ÎËÃÑ ËÊÑÕÑÒÂÏË ÂÕÑÏÂÓÐÑÅÑ ÖÓÂР(ÏÇÕÑAE AVLIS ì Atomic Vapor Laser Isotope Separation) [8,9], ÎËÃÑ ËÊÑÕÑÒÑÏÇÓÂÏË ÅÇÍÔÂ×ÕÑÓËAE ÖÓÂР(ÏÇÕÑAEÞ MLIS ì Molecular Laser Isotope Separation Ë SILEX ì Separation of Isotopes by Laser EXcitation) [10,11]. 2.…”