More and more new uses are being discovered and present uses are being rapidly expanded for materials which are enriched in one or more specific isotopes in such fields as medicine, nuclear energy production and use, and the like. It is desirable because of this increased demand for isotopic enrichment that processes be developed which produce relatively large quantities of materials enriched in certain isotopes and at a relatively low cost. The complexity and cost aspects of isotope separation and enrichment is further complicated by the fact that it is generally more difficult to separate isotopic species of heavier or high atomic weight elements than it is for lower atomic weight elements.
Apparatus and process which is capable of producing relatively large quantities of materials enriched in one or more isotopes for relatively low cost is described in copending application Ser. No. 443,169, entitled "Apparatus and Method for Laser Induced Isotope Separation" by C. Paul Robinson, Reed J. Jensen, Theodore P. Cotter, Keith Boyer and Norman R. Greiner, and filed Feb. 20, 1974 which is a continuation in part of application Ser. No. 387,859, filed Aug. 14, 1973 for "Isotope Separation by Laser Means" by the same inventors. In the described apparatus and process, the raw material to be enriched is adiabatically expanded through a nozzle to a reduced temperature and high flow rate in a gaseous stream. The cooling of the gas in the rapid manner provided by the nozzle provides a unique means of unequivocally making available the discrete vibrational level shift of the isotopes by suppressing all other interfering states. The cooled gas is irradiated by an infrared laser to selectively excite a vibrational state of an isotope in the gas mixture. The gas stream which now includes the excited isotope is then irradiated by an ultraviolet beam to increase the energy of the excited isotope to a level where it may photo-decompose, photo-ionize or otherwise photo-dissociate in a manner allowing separation from other isotopes.
It has been found that this apparatus and process will be particularly useful in separation or enrichment of isotopes of such as uranium and plutonium, and particularly uranium-235 and uranium-238. In order to provide maximum rates of isotopic enrichment at minimum costs for these isotopes, it is desirable that the infrared radiation be produced with an infrared laser which produces an output laser beam at wavelengths near 7.75, 8.62, 12.2 or 16 microns. In addition, it is desirable that the laser beam be in a pulse mode of operation having up to 10,000 laser pulses per second of about 0.2 microseconds in duration and with a pulse energy of about 0.05 joule and an average beam power of about 100 watts. There are no laser systems or arrangements in the prior art which are capable of operating at these wavelengths and under these restrictions.