CA1137442A - Isotope separation process - Google Patents
Isotope separation processInfo
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- CA1137442A CA1137442A CA000340714A CA340714A CA1137442A CA 1137442 A CA1137442 A CA 1137442A CA 000340714 A CA000340714 A CA 000340714A CA 340714 A CA340714 A CA 340714A CA 1137442 A CA1137442 A CA 1137442A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D59/00—Separation of different isotopes of the same chemical element
- B01D59/34—Separation by photochemical methods
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Abstract
(U.S. 37,877) ABSTRACT OF THE DISCLOSURE
A method for the separation of isotopes is disclosed including providing a vapor of a compound of the element whose isotopes are to be separated, the compound having an isotopically shifted but overlapping infrared absorption spectrum associated with the isotopes of that element within a predetermined temperature range, irradiating the vapor with a predetermined fluence of infrared radiation which is preferentially absorbed by a molecular vibration of the molecules of the compound containing a predetermined isotope of the element, thereby providing excited molecules enriched in the predetermined isotope, while maintaining the vapor at a temperature within the predetermined temperature range which, at thermal equilibrium, provides sufficient molecules requiring more than a single photon to promote dissociation so that upon dissociation the isotopic selectivity is at least ten percent above the maximum selectivity which can be achieved with an ensemble of molecules, each of which can dissociate by absorbing a single photon.
In a preferred embodiment, the isotopes of uranium are separated utilizing uranyl compounds having the formula UO2A2.L where A is a mono-valent anion and L is a neutral ligand having a basicity towards the uranyl ion equal to or stronger than that of tetrahydrofuran (THF).
A method for the separation of isotopes is disclosed including providing a vapor of a compound of the element whose isotopes are to be separated, the compound having an isotopically shifted but overlapping infrared absorption spectrum associated with the isotopes of that element within a predetermined temperature range, irradiating the vapor with a predetermined fluence of infrared radiation which is preferentially absorbed by a molecular vibration of the molecules of the compound containing a predetermined isotope of the element, thereby providing excited molecules enriched in the predetermined isotope, while maintaining the vapor at a temperature within the predetermined temperature range which, at thermal equilibrium, provides sufficient molecules requiring more than a single photon to promote dissociation so that upon dissociation the isotopic selectivity is at least ten percent above the maximum selectivity which can be achieved with an ensemble of molecules, each of which can dissociate by absorbing a single photon.
In a preferred embodiment, the isotopes of uranium are separated utilizing uranyl compounds having the formula UO2A2.L where A is a mono-valent anion and L is a neutral ligand having a basicity towards the uranyl ion equal to or stronger than that of tetrahydrofuran (THF).
Description
1 The present invention relates to a method for the
2 separation of isotopes and more partlcularly, the present
3 invention relates to a method for the separation of isotopes
4 employing infrared radiation.
In accordance with the teachings of this invention, it . has been discovered that when separating isotopes of an 7 element by selective photodissociation of a mixture of 8 molecules containing isotopes of the element where the g absorption spectra of the molecules are shifted but overlap-10 ping, the compounding effect of multiple photon selectivity 11 is related to the number of photons which must be absorbed to 12 produce dissociation by those molecules with the largest 13 amount of thermal energy in the mixture, as well as the 14 number of such molecules having such thermal energy. In 15 accordance with the teachings of this invention, 2 method of 16 separating isotopes of an element is taught which includes 17 the steps of:
18 (1) providing a vapor of a compound of the element 19 having an isotopically shifted but overlapping infrared absorption spectrum associated with the 21 isotopes of the element which does not change 22 appreciably upon the absorption of photons when the 23 compound is maintained within a predetermined 24 temperature range; and (2) irradiating the vapor with a predetermined fluence 26 of infrared radiation which is preferentially 27 absorbed by an infrared-active molecular vibration 28 of molecuies of the compound containing a predeter-29 mined isotope of the element, thereby providing excited molecules of the compound, enriched in the 31 predetermined isotope; while maintaining the vapor 32 of the compound at a temperature within the 33 predetermined temperature range which provides 34 sufficient molecules at thermal equilibrium that require more than one photon to promote dissocia-36 ~ion so that upon dissocia~ion ~he isotope ,' ~
`~ ~137442 1 selectivity is at least ten percent above the 2 maximum selectivity which can be achieved with an 3 ensemble of molecules of the compound each of which 4 can dissociate by absorbing a single photon, thereby enabling separation of the excited 6 molecules.
7 In the preferred embodiment of this invention, isotopes 8 Of uranium are separated using a CO2 laser to provide the g aforesaid infrared radiation, and molecules of a uranyl 10 compound having a formula UO2AA'.L are employed, where A and J
11 A' are monovalent anions, and L is a neutral ligand. In a 12 most preferred embodiment, the anionic ligand would be 13 1,1,1,5,5,5-hexafluoracetylacetonate (hfacac), and the 14 neutral ligand utilized would be tetrahydrofuran (THF) or 15 another base of similar or greater strength. In another 16 preferred embodiment of the present invention, irradiation of 17 the vapor is conducied with a fluence of infrared radiation 18 such that less than about seventy percent of all of the 19 ensemble of molecules dissociate, preferably less than about 20 fifty percent.
21 As a result of experimental work involving the selective 22 dissociation of UO2(hfacac)2.THF as disclosed in Belgian -23 patent No. 846,225, it was discovered that the selectivity 24 achieved was less than one would have expected theoretically 25 if on the average more than one photon is absorbed by 26 UO2(hfacac)2.THF when selective photodissociation occurs.
27 In accordance with the present invention, it has now 28 been discovered that if a vapor of a compound containing 29 isotopes of an element has an over]apping infrared absorption 30 spectrum associated with the isotopes of that element, the 31 maximum separation factor which can be achieved with 32 molecules starting at thermal equilibrium is a function of 33 the number of and the selectivity of the molecules which 34 require the least number of photons to dissociate from thermal 35 equilibrium. The minimum number of photons necessary to 36 produce dissociation depends on the energy gap between the 1 highest thermally populated state and the lowest 2 dissociative state. If the energy gap is equal to or less 3 than one photons' energy, the selectivity will approach 4 the single photon selectivity ~, where c~ is defined as the ratio of the small signal absorption cross sections of the 6 isotopic species at a given wavelength. This occurs because 7 the molecules have energy contents defined by a thermal 8 ~istribution. The selectivity for those molecules which g require n photons to dissociate iso~n. The overall selectiv-ity is reduced because, under conditions such tnat a 11 significant fraction of molecules requiring n photons has 12 dissociated, nearly all those molecules of both isotopic 13 species which require fewer than n photons have also 14 dissociated. These latter molecules comprise the high energy tail of the thermal distribution. Since they serve 16 only to reduce the overall selectivity, one way to com-17 pensate for this loss is to increase the energy gap between 18 the highest thermally populated state and the lowest dis-19 sociative state. If the energy gap is equal to the energy of n photons, the selectivity will approachcCn, provided 21 certain conditions are met. For example, the irradiation 22 of the vapor has to be conducted such that less than about 23 70% of all the ensemble of molecules dissociate, preferably 24 less than about 50%.
In accordance with this invention, it has thus been 26 recognized that in order to increase selectivity employins 27 compounds under conditions herein under discussion, it is 28 desirable to maintain the temperature cf _he compound 29 curing irradiation at a temperature ~nich provides ~he over-~helming majority of the moiecules at thermal equil brium 31 in states such that .hey require more than one photon to 32 promote dissociation therein. It should be understood 33 that a de ~inimis number of molecules can be in a state tnat 34 requires only one pho.cn ~o dissociate, but in crder to 35 practically practice 'his ;nven~ion, the number should be 36 limi~ed to one in .~hich some compounding effect is observable.
1137~4Z
1 For some chemical compounds a lower temperature 2 limit exists below which the advantages of this invention 3 are lost. Thus, if the temperature is lowered such that the 4 infrared absorption spectrum of these species changes
In accordance with the teachings of this invention, it . has been discovered that when separating isotopes of an 7 element by selective photodissociation of a mixture of 8 molecules containing isotopes of the element where the g absorption spectra of the molecules are shifted but overlap-10 ping, the compounding effect of multiple photon selectivity 11 is related to the number of photons which must be absorbed to 12 produce dissociation by those molecules with the largest 13 amount of thermal energy in the mixture, as well as the 14 number of such molecules having such thermal energy. In 15 accordance with the teachings of this invention, 2 method of 16 separating isotopes of an element is taught which includes 17 the steps of:
18 (1) providing a vapor of a compound of the element 19 having an isotopically shifted but overlapping infrared absorption spectrum associated with the 21 isotopes of the element which does not change 22 appreciably upon the absorption of photons when the 23 compound is maintained within a predetermined 24 temperature range; and (2) irradiating the vapor with a predetermined fluence 26 of infrared radiation which is preferentially 27 absorbed by an infrared-active molecular vibration 28 of molecuies of the compound containing a predeter-29 mined isotope of the element, thereby providing excited molecules of the compound, enriched in the 31 predetermined isotope; while maintaining the vapor 32 of the compound at a temperature within the 33 predetermined temperature range which provides 34 sufficient molecules at thermal equilibrium that require more than one photon to promote dissocia-36 ~ion so that upon dissocia~ion ~he isotope ,' ~
`~ ~137442 1 selectivity is at least ten percent above the 2 maximum selectivity which can be achieved with an 3 ensemble of molecules of the compound each of which 4 can dissociate by absorbing a single photon, thereby enabling separation of the excited 6 molecules.
7 In the preferred embodiment of this invention, isotopes 8 Of uranium are separated using a CO2 laser to provide the g aforesaid infrared radiation, and molecules of a uranyl 10 compound having a formula UO2AA'.L are employed, where A and J
11 A' are monovalent anions, and L is a neutral ligand. In a 12 most preferred embodiment, the anionic ligand would be 13 1,1,1,5,5,5-hexafluoracetylacetonate (hfacac), and the 14 neutral ligand utilized would be tetrahydrofuran (THF) or 15 another base of similar or greater strength. In another 16 preferred embodiment of the present invention, irradiation of 17 the vapor is conducied with a fluence of infrared radiation 18 such that less than about seventy percent of all of the 19 ensemble of molecules dissociate, preferably less than about 20 fifty percent.
21 As a result of experimental work involving the selective 22 dissociation of UO2(hfacac)2.THF as disclosed in Belgian -23 patent No. 846,225, it was discovered that the selectivity 24 achieved was less than one would have expected theoretically 25 if on the average more than one photon is absorbed by 26 UO2(hfacac)2.THF when selective photodissociation occurs.
27 In accordance with the present invention, it has now 28 been discovered that if a vapor of a compound containing 29 isotopes of an element has an over]apping infrared absorption 30 spectrum associated with the isotopes of that element, the 31 maximum separation factor which can be achieved with 32 molecules starting at thermal equilibrium is a function of 33 the number of and the selectivity of the molecules which 34 require the least number of photons to dissociate from thermal 35 equilibrium. The minimum number of photons necessary to 36 produce dissociation depends on the energy gap between the 1 highest thermally populated state and the lowest 2 dissociative state. If the energy gap is equal to or less 3 than one photons' energy, the selectivity will approach 4 the single photon selectivity ~, where c~ is defined as the ratio of the small signal absorption cross sections of the 6 isotopic species at a given wavelength. This occurs because 7 the molecules have energy contents defined by a thermal 8 ~istribution. The selectivity for those molecules which g require n photons to dissociate iso~n. The overall selectiv-ity is reduced because, under conditions such tnat a 11 significant fraction of molecules requiring n photons has 12 dissociated, nearly all those molecules of both isotopic 13 species which require fewer than n photons have also 14 dissociated. These latter molecules comprise the high energy tail of the thermal distribution. Since they serve 16 only to reduce the overall selectivity, one way to com-17 pensate for this loss is to increase the energy gap between 18 the highest thermally populated state and the lowest dis-19 sociative state. If the energy gap is equal to the energy of n photons, the selectivity will approachcCn, provided 21 certain conditions are met. For example, the irradiation 22 of the vapor has to be conducted such that less than about 23 70% of all the ensemble of molecules dissociate, preferably 24 less than about 50%.
In accordance with this invention, it has thus been 26 recognized that in order to increase selectivity employins 27 compounds under conditions herein under discussion, it is 28 desirable to maintain the temperature cf _he compound 29 curing irradiation at a temperature ~nich provides ~he over-~helming majority of the moiecules at thermal equil brium 31 in states such that .hey require more than one photon to 32 promote dissociation therein. It should be understood 33 that a de ~inimis number of molecules can be in a state tnat 34 requires only one pho.cn ~o dissociate, but in crder to 35 practically practice 'his ;nven~ion, the number should be 36 limi~ed to one in .~hich some compounding effect is observable.
1137~4Z
1 For some chemical compounds a lower temperature 2 limit exists below which the advantages of this invention 3 are lost. Thus, if the temperature is lowered such that the 4 infrared absorption spectrum of these species changes
5 appreciably upon absorption of photons, compounding o. the
6 selectivity may not be observed.
7 In accordance with this invention, when compounds having
8 a formula of ~O2AA'.L are employed, where A and A' are
9 monovalent anions and L is a neutral ligand, it is preferred
10 that the neutral ligand L be a base stronger than T~F, toward
11 the uranyl ion, that is, L should have an equilibrium
12 constant for exchange with tetrahydrofuran of greater than 1.
13 The reason for this is that the base strength of the neutral
14 ligand is one of the determining factors in the bond strength
15 between that ligand and the uranyl moiety, and this in turn
16 is a factor in the thermal stability of the molecule, and,
17 therefore, the energy required for dissociation. Irrespec-
18 tive of a compound's dissociation energy, when the average
19 thermal energy content of the compound approaches its
20 dissociation energy a significant number of molecules
21 require only one photon to dlssociate and the selectivity of
22 an isotope separation process performed under such conditions
23 is limited.
24 In accordance with this invention, it has been recog-
25 nized that, all other things being equal, greater base
26 strength is desirable, and furthermore that it is most
27 preferred to operate the process while maintaining the
28 temperature of the compound towards the lower end of its
29 temperature range of volatility.
In particular, the vaporizable compounds used in this 31 invention, and which have an isotopically shifted but 32 overlapping infrared absorption spectrum as discussed above, 33 w111 preferably have the general formula UO2AA'.L, where A
34 and A' represent monovalent anions and L a neutral ligand as 35 discussed above. The anions A and A' which can be employed 36 in this process will generally have conjugate acids which ' .
l have boiling points of less than about 200C. ald PKa valUes 2 of 4.8 or less. These anions ma~ be monodentate or polyden-3 tate, and preferably both A and A' will be the same anion.
4 Pre~erable anions for use in connection with the compounds of the present invention include, in addition to 6 the 1,1,1,5,5,~-hexafluoroacetylacetonate anion discussed 7 above, anions such as l,l,l-trifluoroacety' - acetonate 8 (CF30CHCOCH3), 3-trifluoromethyl-1,1,1,5,5,5-hexa-9 f uoroacetylacetonate ((CF3CO)2CCF3), 1,l,1,3,5,5,5,-hepta-10 fluoroacetylacetonate, ((CF3CO)2CF)1,1,1,2,2,3,3,7,7,7-deca-11 fluoro-4,6-heptanedionate (CF3COCHCOC3F7), fluorinated 12 tropolonates, and others.
13 As for the neutral ligand L which is employed in 14 accordance with the above formula, reference is again made to 15 the preferable minimum basicity requirements discussed above.
16 As noted, it is preferred that L have a base strength 17 greater than that of tetrahydrofuran towards the uranyl ion, 18 or more particularly a basicity measured by the equilibrium 19 constant for the following reaction:
K
21 Uo2(hfacac)2.THF + L = UO2~hfacac)2.'~ + THF
23 ln which K will be greater than l. .~ in this case is measured 24 in an anhydrous nor.-coordinating solvent such as benzene, 25 methylene chloride or chloroform.
26 Preferable neutral ligands which meet these pre-2, requisites for use in the process of this invention include 28 trimethylphosPhate (TMP, (CH30)3P-O);triethylphosphineoxide 29 ((C2H5)3P=O); and hexamethylphos- ~horamide ((CH_)"-N)3P=o);
dimethylsulfoxide ((CH3)2S=O; pyridine (C~H_N), etc.
31 Still another advantage which can be realized by 32 utilizing uranyl compounds containing these neutral ligands 33 in this process arises from the fact that these ligands tend 34 to shift the frequency at which these molecules absorb as 35 compared to UO2(hfacac)2.THF, for example. This shift 36 results from an increase in the strength of the bond between ` ~137442 1 these ligands and the U02 moiety, and it is particularly 2 preferred to use such ligands which shift the position 3 of the absorption band of the uranyl asymmetric stretch 4 into correspondence with C02 laser transitions more favorable 5 with respect to isotopic selectivity and laser efficiency.
6 P~EFE~RED EMBODIMEN~
7 Irradiation of a uranium-containing compound in 8 accordance with the present invention was carried out in a 9 molecular beam such as that disclosed in Belgian Patent ~o.
lO 867,647. The uranium-containing compound which was employed .
11 in that patent was U02(hfacac)2.(THF). It was found that when 12 this compound's photodissociation and IR absorption spectrum 13 were observed in the gaseous state, each exhibited a maximum 14 at 956 cm (nearly resonant with the P(6) transi~ion of 10.6 15 ~.m C02 laser) and a full width at half maximum intensity of 16 about 7.8 cm l.
17 Specifically, the U02(hfacac)2.THF compound was placed 18 in a heated oven having a .005 inch orifice and heated to 19 about 115C. The molten material exhibited a vapor pressure of about 0.2 torr at this temperature, and a molecular beam 2L was produced at the oven orifice. This molecular beam was 22 crossed by a CW 10.6 ~m C02 laser, and a selectivity for 23 preferential dissociation of the uranium 235 containing 24 species of 1.28 + 0.14 was achieved during operation on the P(4) transition at a laser energy fluence of 5.l mJ/cm2 with 26 the contact time of the laser with the molecules being about 27 5 lls. A depletion of l.9 percent of the U-235 containing 28 species was observed. The photodissociation products of this 29 process were found to be U02(hfacac)2 and THF.
Further tests demonstrated that significantly increased 31 selectivities can be obtained if the temperature is lowered.
32 In these experiments, the isotope selective dissociation of 33 U02L2.THF was measured for the P(lO), 10.6 ~m C02 laser 34 transition. Irradiation on this transition selectively dissociates the uranium 2,8 containing molecule. In the 36 results summarized in Table A the molecular beam was crossec ` 1~37442 1 by a pulsed C02 TEA laser with a pulse width of about 400 2 nanoseconds (FWHM). The results in Table A demonstrate that 3 the isotope selectivity increased dramatically as tne 4 temperature was reduced.
Table A
6 Oven No. of Laser ~luence Isotope Dissociation 7 TemO- Laser Pulses (mJ/cm ) Selectivity Fraction 8 C (D8/D5)* ( 8) 9 12020,480 48 1.17 + 0.15 .7 11020,480 120 1.22 + 0.11 .9 ll 84 24,576 48 1.25 + 0.22 .5 12 75 14,336 52 1.o7 + 0.22 .4 13 65 9,216 48 1.91 + 0.37 .3 14 *D8 is dissociation fraction for U238 bearing species.
D5 is dissociation fraction for u235 bearing species.
1~ Additional experiments have been performed using U02 17 (hfacac)2.trimethylphosphate (TMP). The TMP has a base 18 strength stronger than THF with respect to the U02(hfacac)2 l9 complex. The oven was heated to about 100C to produce a molecular beam of U02(hfacac)2.TMP which was then irradiated 21 with a pulsed C02 TEA laser operating on the P(4), 10.6 ~ m 22 transition, a transition which preferentially dissociated the 23 uranium 235 containing species. The selectivity under these 24 conditions was measured to be 1.7 + 0.2. Thus, the selec-tivity achieved with this compound is considerably higher 26 than that achieved with the U02(hfacac)2.THF compound at an 27 equivalent temperature. The value of the single photon 28 selectivity is found to be about 1.4 for U02(hfacac)2.TMP.
29 Thus, the selectivity achieved experimentally is higher for compound of the class U02(hfacac)2.THF with a more 31 strongly bound base, L.
In particular, the vaporizable compounds used in this 31 invention, and which have an isotopically shifted but 32 overlapping infrared absorption spectrum as discussed above, 33 w111 preferably have the general formula UO2AA'.L, where A
34 and A' represent monovalent anions and L a neutral ligand as 35 discussed above. The anions A and A' which can be employed 36 in this process will generally have conjugate acids which ' .
l have boiling points of less than about 200C. ald PKa valUes 2 of 4.8 or less. These anions ma~ be monodentate or polyden-3 tate, and preferably both A and A' will be the same anion.
4 Pre~erable anions for use in connection with the compounds of the present invention include, in addition to 6 the 1,1,1,5,5,~-hexafluoroacetylacetonate anion discussed 7 above, anions such as l,l,l-trifluoroacety' - acetonate 8 (CF30CHCOCH3), 3-trifluoromethyl-1,1,1,5,5,5-hexa-9 f uoroacetylacetonate ((CF3CO)2CCF3), 1,l,1,3,5,5,5,-hepta-10 fluoroacetylacetonate, ((CF3CO)2CF)1,1,1,2,2,3,3,7,7,7-deca-11 fluoro-4,6-heptanedionate (CF3COCHCOC3F7), fluorinated 12 tropolonates, and others.
13 As for the neutral ligand L which is employed in 14 accordance with the above formula, reference is again made to 15 the preferable minimum basicity requirements discussed above.
16 As noted, it is preferred that L have a base strength 17 greater than that of tetrahydrofuran towards the uranyl ion, 18 or more particularly a basicity measured by the equilibrium 19 constant for the following reaction:
K
21 Uo2(hfacac)2.THF + L = UO2~hfacac)2.'~ + THF
23 ln which K will be greater than l. .~ in this case is measured 24 in an anhydrous nor.-coordinating solvent such as benzene, 25 methylene chloride or chloroform.
26 Preferable neutral ligands which meet these pre-2, requisites for use in the process of this invention include 28 trimethylphosPhate (TMP, (CH30)3P-O);triethylphosphineoxide 29 ((C2H5)3P=O); and hexamethylphos- ~horamide ((CH_)"-N)3P=o);
dimethylsulfoxide ((CH3)2S=O; pyridine (C~H_N), etc.
31 Still another advantage which can be realized by 32 utilizing uranyl compounds containing these neutral ligands 33 in this process arises from the fact that these ligands tend 34 to shift the frequency at which these molecules absorb as 35 compared to UO2(hfacac)2.THF, for example. This shift 36 results from an increase in the strength of the bond between ` ~137442 1 these ligands and the U02 moiety, and it is particularly 2 preferred to use such ligands which shift the position 3 of the absorption band of the uranyl asymmetric stretch 4 into correspondence with C02 laser transitions more favorable 5 with respect to isotopic selectivity and laser efficiency.
6 P~EFE~RED EMBODIMEN~
7 Irradiation of a uranium-containing compound in 8 accordance with the present invention was carried out in a 9 molecular beam such as that disclosed in Belgian Patent ~o.
lO 867,647. The uranium-containing compound which was employed .
11 in that patent was U02(hfacac)2.(THF). It was found that when 12 this compound's photodissociation and IR absorption spectrum 13 were observed in the gaseous state, each exhibited a maximum 14 at 956 cm (nearly resonant with the P(6) transi~ion of 10.6 15 ~.m C02 laser) and a full width at half maximum intensity of 16 about 7.8 cm l.
17 Specifically, the U02(hfacac)2.THF compound was placed 18 in a heated oven having a .005 inch orifice and heated to 19 about 115C. The molten material exhibited a vapor pressure of about 0.2 torr at this temperature, and a molecular beam 2L was produced at the oven orifice. This molecular beam was 22 crossed by a CW 10.6 ~m C02 laser, and a selectivity for 23 preferential dissociation of the uranium 235 containing 24 species of 1.28 + 0.14 was achieved during operation on the P(4) transition at a laser energy fluence of 5.l mJ/cm2 with 26 the contact time of the laser with the molecules being about 27 5 lls. A depletion of l.9 percent of the U-235 containing 28 species was observed. The photodissociation products of this 29 process were found to be U02(hfacac)2 and THF.
Further tests demonstrated that significantly increased 31 selectivities can be obtained if the temperature is lowered.
32 In these experiments, the isotope selective dissociation of 33 U02L2.THF was measured for the P(lO), 10.6 ~m C02 laser 34 transition. Irradiation on this transition selectively dissociates the uranium 2,8 containing molecule. In the 36 results summarized in Table A the molecular beam was crossec ` 1~37442 1 by a pulsed C02 TEA laser with a pulse width of about 400 2 nanoseconds (FWHM). The results in Table A demonstrate that 3 the isotope selectivity increased dramatically as tne 4 temperature was reduced.
Table A
6 Oven No. of Laser ~luence Isotope Dissociation 7 TemO- Laser Pulses (mJ/cm ) Selectivity Fraction 8 C (D8/D5)* ( 8) 9 12020,480 48 1.17 + 0.15 .7 11020,480 120 1.22 + 0.11 .9 ll 84 24,576 48 1.25 + 0.22 .5 12 75 14,336 52 1.o7 + 0.22 .4 13 65 9,216 48 1.91 + 0.37 .3 14 *D8 is dissociation fraction for U238 bearing species.
D5 is dissociation fraction for u235 bearing species.
1~ Additional experiments have been performed using U02 17 (hfacac)2.trimethylphosphate (TMP). The TMP has a base 18 strength stronger than THF with respect to the U02(hfacac)2 l9 complex. The oven was heated to about 100C to produce a molecular beam of U02(hfacac)2.TMP which was then irradiated 21 with a pulsed C02 TEA laser operating on the P(4), 10.6 ~ m 22 transition, a transition which preferentially dissociated the 23 uranium 235 containing species. The selectivity under these 24 conditions was measured to be 1.7 + 0.2. Thus, the selec-tivity achieved with this compound is considerably higher 26 than that achieved with the U02(hfacac)2.THF compound at an 27 equivalent temperature. The value of the single photon 28 selectivity is found to be about 1.4 for U02(hfacac)2.TMP.
29 Thus, the selectivity achieved experimentally is higher for compound of the class U02(hfacac)2.THF with a more 31 strongly bound base, L.
Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of separating isotopes of an element comprising providing a vapor of a compound of said element having an isotopically shifted but overlapping infrared absorption spectrum associated with the isotopes of said element which does not change appreciably upon the absorption of photons when said compound is initially in a predetermined temperature range; and irradiating said vapor with a predetermined fluence of infrared radiation which is preferentially absorbed by a molecular vibration of the molecules of said compound containing a predetermined isotope of said element thereby providing excited molecules of said compound enriched in said predetermined isotope, while maintaining said vapor of said compound at a temperature within said predetermined temperature range which provides sufficient molecules at thermal equilibrium that require more than one photon to promote dissociation so that upon dissociation the isotopic selectivity is at least 10% above the maximum selectivity which can be achieved with an ensemble of molecules of said compound each of which can dissociate by absorbing a single photon, enabling separation of said excited molecules.
2. The method of Claim 1 wherein said predeter-mined fluence of infrared radiation is provided by a CO2 laser.
3. The method of Claim 1 wherein said element comprises uranium.
4. The method of Claim 3 wherein said compound comprises a uranyl compound.
5. The method of Claim 4 wherein said uranyl compound has the general formula UO2AA'.L where A and A' are monovalent anions having conjugate acids which have boiling points of less than about 200°C. and pKa values of about 4.8 or less, and L is a neutral ligand.
6. The method of Claim 5 wherein said neutral ligand (L) has an equilibrium constant for exchange with tetrahydrofuran on the uranyl ion of greater than about 1.
7. The method of Claim 6 wherein said neutral ligand (L) is selected from the group consisting of trimethyl-phosphate, triethylphosphine oxide and hexamethylphosphora-mide.
8. The method of Claim 5 wherein A and A' comprise the same anion.
9. The method of Claim 8 wherein said anion comprises 1,1,1,5,5,5-hexafluoroacetylacetonate.
10. The method of Claim 1 wherein said predeter-mined fluence of infrared radiation is such that less than about 70% of said ensemble of molecules dissociates.
11. The method of Claim 1 wherein said predeter-mined fluence of infrared radiation is such that less than about 50% of said ensemble of molecules dissociates.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US3787779A | 1979-05-10 | 1979-05-10 | |
| US37,877 | 1979-05-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1137442A true CA1137442A (en) | 1982-12-14 |
Family
ID=21896843
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000340714A Expired CA1137442A (en) | 1979-05-10 | 1979-11-27 | Isotope separation process |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS55149635A (en) |
| AU (1) | AU5331179A (en) |
| BE (1) | BE880703A (en) |
| CA (1) | CA1137442A (en) |
| DE (1) | DE2949117A1 (en) |
| FR (1) | FR2455918A1 (en) |
| GB (1) | GB2048553A (en) |
| IL (1) | IL58854A (en) |
| NL (1) | NL7909093A (en) |
| SE (1) | SE7909873L (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2542733C1 (en) * | 2013-08-30 | 2015-02-27 | Федеральное государственное бюджетное учреждение "Национальный исследовательский центр "Курчатовский институт" | Method of producing lutetium-177 radioisotope |
-
1979
- 1979-11-27 CA CA000340714A patent/CA1137442A/en not_active Expired
- 1979-11-29 AU AU53311/79A patent/AU5331179A/en not_active Abandoned
- 1979-11-29 SE SE7909873A patent/SE7909873L/en not_active Application Discontinuation
- 1979-12-03 IL IL5885479A patent/IL58854A/en unknown
- 1979-12-03 GB GB7941700A patent/GB2048553A/en not_active Withdrawn
- 1979-12-06 DE DE19792949117 patent/DE2949117A1/en not_active Withdrawn
- 1979-12-06 JP JP15867879A patent/JPS55149635A/en active Pending
- 1979-12-17 NL NL7909093A patent/NL7909093A/en not_active Application Discontinuation
- 1979-12-19 BE BE2/58280A patent/BE880703A/en unknown
- 1979-12-27 FR FR7931787A patent/FR2455918A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| DE2949117A1 (en) | 1980-11-20 |
| GB2048553A (en) | 1980-12-10 |
| SE7909873L (en) | 1980-11-11 |
| NL7909093A (en) | 1980-11-12 |
| BE880703A (en) | 1980-06-19 |
| IL58854A (en) | 1983-03-31 |
| JPS55149635A (en) | 1980-11-21 |
| FR2455918A1 (en) | 1980-12-05 |
| AU5331179A (en) | 1980-11-13 |
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