Wide angle isotope separator

Abstract

Abstract For particle separation, a method and apparatus for using a wide angle radially expanding vapor of a particle mixture. In particular, selective ionization of one isotope type in the particle mixture is produced in a multichamber separator and the ionized isotope type is accelerated out of the path of the vapor expansion for separate collection. FIELD OF THE INVENTION This invention relates to isotope separation by selective ionization and in particular to a separation system making efficient use of an isotope source. BACKGROUND OF THE INVENTION Nearly all fission reactions utilizing the uranium isotope, U 235 , require a concentration of the U 235 isotope greater than in the naturally occurring state. The process of enrichment whereby the concentration of U 235 in natural or depleted uranium is raised to a desired level has been achieved in the past by many techniques which generally operate to separate U 235 from the other uranium isotopes, chiefly U 238 , on the basis of its slight chemical or mass difference. Enrichment according to these techniques often requires cascaded processing using a sequence of repeated applications of the same steps, each step providing a slight increase in the concentration of the desired U 235 isotope. A promising technique for more efficiently separating the U 235 isotope operates by selectively ionizing this isotope in a vapor of uranium without correspondingly ionizing the U 238 isotope in the vapor. The ionization gives to the desired U 235 isotope an electrical characteristic which permits it to be separated from the rest of the components of the uranium vapor. The uranium is converted to a vapor state to facilitate the application of ionizing energy in the form of laser radiation to the uranium and to provide a volume of relatively mobile particles from which the ionized uranium atoms may be separated using crossed-field MHD accelerator techniques. The process of enrichment is typically continuous by providing repeated application of laser radiation and acceleration forces in sequence so that it is desirable to continuously generate the vapor as by heating the uranium to provide a vapor flow. As is known, evaporation of a material to the gas or vapor state produces a generally expanding volume of the gas in all directions. Nevertheless, the physics of crossed-field MHD acceleration of ionized particles in a vapor or plasma generally increase in efficiency with decreasing dimensions of the separation region. This is, at least in part, due to limitations of the mean free path of accelerated particles, it being desirable to collect the accelerated particles in distances where there is little probability of diverting particle collisions with other constituents to occur. Thus while it is desirable to accept the large angle of vapor flow which is generally created, theory advocates relatively small areas for the crossed-field separation process. Additionally, separation of the ionized particles from the vapor is efficiently achieved where a well defined vapor flow having a uniform local particle direction can be maintained such that ionized particles may be accelerated in an orthogonal direction and both the ionized particles and the remaining vapor constituents separately collected for removal from the system as uranium enriched in the respective isotope concentrations. This desirable separation condition is typically facilitated by confining the area and angle of the vapor flow. BRIEF SUMMARY OF THE INVENTION In accordance with the teaching of the present invention an enrichment system using selective ionization is shown wherein a vapor of uranium produced as a radially expanding vapor drift over a substantial angle is directed toward a surrounding multichambered crossed-field MHD accelerator placed to receive the radially expanding vapor over a corresponding angle and provide, after selective ionization, separation of ionized and non-ionized vapor particles into two orthogonal motions. System efficiency is thereby improved by adapting the ion separator to accept the wide angle expansion of the uranium vapor. Moreover, the need for periodic cleaning of the vapor generating apparatus from recycling of unused vapor is reduced. In particular implementation, an electron beam is focused to strike the surface of uranium metal over a long thin line and to create local vaporization at the points of impact along the line. Vaporized uranium expands radially away from the impact line into a region where application of laser energy produces a plasma containing selectively ionized atoms of the desired U 235 isotope without correspondingly ionized atoms of the other components of the vapor. A plurality of ion separating and collecting chambers enclose the ionization region and operate to impart to the ions of the plasma a velocity substantially perpendicular to the radial velocity of the plasma as a whole. It is thereby possible to collect the separately directed particles of the U 235 isotope apart from the rest of the vapor which is permitted to continue on its radial path for collection and removal from the system. As a result of this technique, it is possible to provide an increased efficiency in the generation and utilization of the uranium vapor. Moreover, the system can operate without cleaning for greater periods of time and a greater enrichment yield is possible without increased system and operating cost.

Inventors

• 👤 Arthur Kantrowitz

Bibliographic Details