Oxygen isotope concentration method

Abstract

A method of concentrating the stable oxygen isotopes of 17 O and 18 O by irradiating ozone with light, selectively dissociating an isotopologue of ozone containing an oxygen isotope in its molecule into oxygen, followed by dissociating the ozone and separating the formed oxygen from the non-dissociated ozone. In the ozone photodissociation step, light is radiated onto a rare gas-ozone mixed gas containing ozone and at least one rare gas selected from krypton, xenon and radon is used to selectively dissociate ozone containing a specific oxygen isotope in its molecule into oxygen then the oxygen isotope is separated from non-dissociated ozone and rare gas to concentrate the oxygen isotope present in the separated oxygen.

1 . (canceled) 
     
     
         2 . An oxygen isotope concentration method comprising:
 (A) an ozone formation step, in which ozone is produced from raw material oxygen, thereby forming a mixture of the produced ozone and the raw material oxygen;   (B) an ozone separation step, in which the produced ozone is separated from the mixture;   (C) an ozone photodissociation step, in which ozone molecules containing oxygen isotopes,  17 O and/or  18 O, are selectively photodissociated to oxygen molecules; thereby generating a mixture of the oxygen molecules and non-dissociated ozone molecules; and   (D) an oxygen isotope concentration step, in which the oxygen molecules are separated from the mixture obtained in the step (C), thereby concentrating the oxygen isotope.   
     
     
         3 . An oxygen isotope concentration method according to  claim 2  further comprising:
 (E) a second ozone photodissociation step, in which the non-dissociated ozone molecules containing an oxygen isotope that is different from one separated in the step (D) are photodissociated to oxygen molecules, thereby generating a mixture of the oxygen molecules and non-dissociated ozone molecules; and 
 (F) a second oxygen isotope concentration step, in which the oxygen molecules are separated from the mixture obtained in the step (E), thereby concentrating the oxygen isotope that is different from one separated in the step (D). 
 
     
     
         4 . (canceled) 
     
     
         5 . An oxygen isotope concentration method according to  claim 2 , wherein at least one type of rare gas selected from krypton, xenon and radon is added in the step (B). 
     
     
         6 . (canceled) 
     
     
         7 . An oxygen isotope concentration method according to  claim 2 , wherein at least one type of rare gas selected from helium, neon, argon, and krypton is added to the raw material oxygen in the step (A). 
     
     
         8 . An oxygen isotope concentration method according to  claim 7 , further comprising:
 (G) an ozone abatement step, in which the non-dissociated ozone molecules remaining after the step (D) are decomposed into oxygen molecules, thereby forming a mixture of the oxygen molecules and the rare gas; and   (H) a rare gas separation step, in which the rare gas is separated from the mixture obtained in the step (G);   wherein the rare gas separated in the step (H) is recycled for use in the step (A).   
     
     
         9 . An oxygen isotope concentration method according to  claim 8 , further comprising, between the step (D) and (G), the following steps:
 (E′) a second ozone photodissociation step, in which molecules of an isotopologue of ozone that are different from those of the isotopologue of ozone dissociated in the step (C) are photodissociated to oxygen molecules, thereby generating a mixture of the oxygen molecules and non-dissociated ozone molecules; and   (F′) a second oxygen isotope concentration step, in which the oxygen molecules obtained in the step (E′) are separated from the mixture generated in the step (E′), thereby concentrating the second oxygen isotope in the separated oxygen molecules.   
     
     
         10 .- 21 . (canceled) 
     
     
         22 . An oxygen isotope concentration method according to  claim 2 , wherein the oxygen isotope concentration step (D) is a distillation carried out by adding at least one type of rare gas selected from helium, neon and argon. 
     
     
         23 . An oxygen isotope concentration method according to  claim 2 , wherein the light used in the ozone photodissociation step (C) is either near-infrared light within the range of 700-1000 nm, or visible light within the range of 450-850 nm. 
     
     
         24 . An oxygen isotope concentration method according to  claim 23 , wherein the wavelength of the light used in the ozone photodissociation step (C) is within the range of 991.965-992.457 nm. 
     
     
         25 . An oxygen isotope concentration method according to  claim 2 , wherein the absorption wavelength of ozone is adjusted by applying an electric field in the ozone photodissociation step (C). 
     
     
         26 . An oxygen isotope concentration method according to  claim 2 , wherein the ozone photodissociation step (C) is carried out at low temperature and at low pressure.