CA1117471A - Method for the separation of isotopes by isotope-selective excitation - Google Patents
Method for the separation of isotopes by isotope-selective excitationInfo
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- CA1117471A CA1117471A CA000323342A CA323342A CA1117471A CA 1117471 A CA1117471 A CA 1117471A CA 000323342 A CA000323342 A CA 000323342A CA 323342 A CA323342 A CA 323342A CA 1117471 A CA1117471 A CA 1117471A
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- isotope
- mixture
- vaporous
- irradiation
- flow
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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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- Biophysics (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
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- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Separation of isotopes by pulsed laser beams to selectively excite one isotope and subsequent chemical or physical separation. More complete and effective excitation of the isotope to be excited is obtained by a combination of a) intermittent or periodic flow of the stream of isotope compounds at constant intervals, b) a flow of isotope vapor of short time duration of the order of milliseconds, c) adiabatic cooling to below 100 K, d) flowing the cooled mixture to an irradiation zone in accordance with the intermittent flow, e) subjecting the cooled mixture during the short time duration of flow to consecutive pulses of a number of consecutively fired lasers to effect substantially complete excitation of the isotope compound to be excited.
Separation of isotopes by pulsed laser beams to selectively excite one isotope and subsequent chemical or physical separation. More complete and effective excitation of the isotope to be excited is obtained by a combination of a) intermittent or periodic flow of the stream of isotope compounds at constant intervals, b) a flow of isotope vapor of short time duration of the order of milliseconds, c) adiabatic cooling to below 100 K, d) flowing the cooled mixture to an irradiation zone in accordance with the intermittent flow, e) subjecting the cooled mixture during the short time duration of flow to consecutive pulses of a number of consecutively fired lasers to effect substantially complete excitation of the isotope compound to be excited.
Description
~117471 The present invention relates to a method for the efficient separation of isotopes from a mixture of gaseous isotope compounds by isotope-selective excitation of one of the isotope compounds contained therein and subsequent chemical or physical separation thereof by means of pulsed laser beams.
In all the methods for isotope-selective excitation, separation is achieved by~ exciting only one isotope compound so that the latter preferentially converts by chemical reaction or otherwise into a chemical compound, whereby this new compound 10 can be separated relatiyely readily by normal mechanical and chemical means from the original mixture of sub.stances. This new compound then contains preferentially the desired isotope such as uranium 235. The separation of isc:topes is of technical interest especially for uranium, si.nce the fissionable isotope uranium 235, which alone i.s usable, is present in the natural uranium only in the amount of û.7% and ~ust be enriched in the nuclear fuel for light-water reactors to about 2 to 3%.
Excitation of the one isotope compound, howeyer, can also be used for ionizing the latter and to make it separable 20 thereby electrically, ox to influence its. dipole behayior in such a manner that deflection by the electric field of the laser radiation itself becomes possible. Further details on laser-induced i.s.otope separation methods by means of physical and chemical separati.on can be found in German Published Non-Prosecuted Applications Numbers 2 311 584 and 2 324 797. Further proposals for th.e isotope separation via selective excitation of molecular energy levels can be found in German Published Non-Prosecuted Application Number 2 459 989, where the use of 1117d~71 wa~el.en~ths in the infrared and ultra-Yiolet ran~e is discussed in particular.
Almost all uranium isotope separation methods start out with the compound UF6, which uranium compound exhibits sufficient vapor pressure for e~fecting i.sotope selective excitation. It has been found, however, th.at selective excitation performed at normal temperatures does not permit the attainment of the desired enrichment values because of the over-lap of the absorption bands, resonance exchan~e and thermally acti.vated reactions. It has been proposed as an improvement to expand the ~aseous isotope mixture adiabatically to temperatures below 100 K and to i.rradiate it before it is condensed, with a laser beam o~ s:ultable frequency contai.ned in a resonator; see in this connection German PubIished Non-Prosecuted Application Number 2 447 762. It haa also been proposed to accomplish the cooling-down of the isotope mi-xture by a neutral, heavily undercooled supplemental gas that is to be admitted, instead of the adiabatic expans.ion, as described in German Published Non-Prosecuted Application Number 2 651 306.
This and other i.sotope separation methods are feasible, with the use of so-called continuous lasers, but such equipment has low output power and the operation is not very efficient, however.
Performing the isotope separation processes with pulsed lasers also h.as its problems. Since the laser pulaes, which are in the order of one nanosecond, are very short and the pulse repetition frequency i.s maximally about 100 Hz, only a very small amount of material can be excited by th.e present methods using ~:~1747i such pulsed lasers, so that the use of ~ulsed lasers in the manner described is disadvantageous in thi.s. respect. It should be recalled in this~ connection that the gas mixture put through must be recirculated a~ain and again because as pre~iously stated only a very small amount of material can be excited, so that enormous pump powers are required res.ultin~ in large capital inyestment and high operati.ng cost.
An object of the present inyention is to provide a process for the economical application of pulsed lasers for the separation of isotopes from a mixture of vaporous isotope compounds, ensuring that the entire mixture of substances put through is irradiated in its entirety and the molecules that can be excited are actually excited.
With the foregoing and other objects in view, there is provided in accordance with the invention a method for the separation of isotopes from a mixture of vaporous isotope compounds by the application of pulsed laser beams to effect selective excitation of one of the is:otope compounds contained therein and subsequent chemical or physi.cal separation of the ~ excited isotope compound, the improvement comprising a) flowing a stream of the mixture of vaporous isotope compounds periodically at constant intervals, b) continuing the flow of the mixture of Yaporous isotope compounds. during each period of flow-for a s.hort time in the range of milliseconds, c) adiabatically expanding each.stream of the mixture of vaporous isotope compounds flowing per~odically to cool the mi.xture to a temperature below 100 K, il:l7L~7~L
d) flowing the cooled mixture of yaporous isotope compounds to an irradiation zone at said intervals, and e) flowing the cooled mixture through the irradiation zone ànd subjecting the cooled mixture during the time of flow duration to consecutive pulses of a plurality of consecutively fired lasers to excite substantially all of the one isotope compound to be selecti.vely excited during flow of the mixture of vaporous isotope compounds through the irradiation zone.
In accordance with the invention there is provided apparatus for controlling the ~low of a mixture of vaporous isotope compounds and adiabatically expanding the mixture of vaporous isotope compounds to cool the ~ixture to a temperature below 100 K, for the separation of isotopes from the mixture by the application of pulsed laser beams to effect selective excitation of one of the isotope compounds, contained therein which comprises a) a slot-shaped expansion nozzle, b) a valve whose outlet extends oyer the entire width of the inlet to th.e expansion nozzle, c) sai,d valYe havi.ng a rotor, rotatable at a constant speed, with two di.ametrically opposite lon~i.tudinal slots, d) a housing with a vapor inlet surroundin~ and sealing the rotor, said rotor when aligned with one slot facing the vapor i.nlet and the other s,lot facing the inlet to the expansion nozzle permits the flow of Yapor through sald valYe~
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described 47~
herein as embodied i.n a method for the separation of isotopes by isotope-selective excitation, it is: neverth.eless not intended to be limited to the details shown, s.ince ~arious modifications may be made therein with.out departing from the spirit of the i.nvention and within the scope and range of equivalents of the claims.
The invention, however, toge.ther with addi.tional objects and advantages thereof will ~e best understood from the following description when read in connecti.on with the accompany-ing drawings, in which:
Figure 1 sh.ows a valve with a rotor, an expansion nozzle and an irradiation space and diagrammatically illustrates the relationship between the irradiation s.pace, expansion nozzle and valve in accordance with the invention, Figure 2 shows a timing diagram i:llustrati.ng the switching sequences of the valve as well as the firing sequences of the lasers, Figure 3 diagrammatically illustrates directing radiations from di.fferent lasers into the i.rradiation space by means of mirrors, and Figure 4 illustrates conducti.ng the radiation through a cylinder lens into the irradiation space.
In accordance with the invention, the vaporous mixture of the isotope compounds as well as of supplemental gases known per se and/or reaction partners are adiabatically expanded at constant time interYals, always for a flow duration in the range of milliseconds, via a nozzIe, and is thereby cooled down to below 100 K. The cooled gas mixture fed at interyals to an irradiation space is exposed duri.ng the entire flow duration to consecutive pulses of consecutiYely fired lasers for substan-tially, quantitati.vely complete isotope-specific excitation.
This method is thus based on the combination of at least two characteristi.cs: To send the gas mixture which is to be fed to the isotope separation facilit~ at continuously repeated i.nter~als for a sho~i~t flow duration through the irradiation space, and to cover it in its entirety radiation-wise by a multiplicit~ of consecuti~ely fired laser equipments of the same frequency. This is based on the following considerations:
Our own tests have shown that with dynami.c cooling of a gas mixture, the selective exci.tati.on and s:eparation of the desired isotope compound must take place on a travel distance of about 2 cm. W;th a jet velocity of the materi.al mixture entering the irradiation space of about 500 m~sec, the flight time of a molecule through. this distance is about 40 ~sec. If one now irradi.ates this enti.re zone of 2 cm length with a laser pulse and makes a further laser pulse follow-after another 4Q ~sec, then the irradiated regions of the materi.al mixture jet follow each other without gap. To this end, however, a laser with a pulse repetition frequency o~ 25 kHz would be requi.red, but these likewise do not yet exi.st with the desired : wavelengths and powex ranges. The requi.red pulse energies are about 1 Ws in the W range ~0.3 to 0.4 pm). and about Q.025 ~s in th.e IR range C16 ~m).
Th.is difficult~ is overcome wi.th. the pre~ent inYention in that the required puls:e repetiti:on frequency is formed by 1~1'^~471 the consecutiye firing of a multi,plicity of identical lasers.
Since, however, the number of these lasers is li~ited, not only for economic reasons but also because of the ph~sical arrange-ment (they all must be arranged so that their radiation goes through the irrad;~ati,on space by the same path), provision is now made that the mater~al mi:xture jet tra~els: through the irradiation chamber only during the radiati`on time of these consecutiyely fired lasers. This is accomplished by inserting ahead of the expansi`,on nozzle a val~e, which transports at periodic inte~Yals, which correspond to the pos.sible pulse repetition fre~uenc~ of a laser, a length-limited material mixture jet through the irradiati.on space.
This procedure will now ~e explained, to illustrate the invention in greater detail, with, the aid o~ an example, referring to Figures 1 to 4.
Figure 1 shows diagrammatically the spatial relationship between the irradiation space 3, the nozzIe 2 and the valve 4.
The procedure is now as follows: The material mixture 16, i.e.
the mixture of vaporous isotope compounds together with supplemental gas and reaction partneL, flows through the line 45 into the valYe 4. The latter cons~ists of a tubular housing 41, to which are connected on the one $ide the feed line 45 and on the other side the expansion nozzle 2. Inside this housing rotates, with constant speed of rotation, a rotor 42 proYided w1th slots 43 and 44 whi.ch are likewi,se arranged di.ametrically opposite each other. When these slots. 43 and 44 establish a connection between the feed li.ne 45 and the nozzle 2, a material mixture jet o~ always the same length'will traveI through the 1~17~71 irradiation space 3. The length o~ this i.rradi.ation space is designated with s. With a jet veloci.ty of 500 m/sec, a molecule traverses this distance in 40 ~sec. If now the front of the gas stream leaving the nozzle has arrived in ~ront of the end of the irradiation space 3, the fi.rst laser is fired, and the next one at intervals of 40 ~sec. each. Thus, a division of the material mixture jet into irradiation zones gl to gn is obtained, which follow each other without a gap. In Figure 1 is shown that situation, in which just the last material jet region gn is being irradiated by the last (the nth) laser. The total length of the material mixture jet leaving the nozzle 2 at intervals is then obtained from the number of lasers n times the length of the irradiation space s.
Figure 2 shows in a timing diagram the switching sequences of the valve 4 as well as of the n lasers. The valve 4 opens the flow path at intervals of ~.Tl, where ~Tl will be assumed to be, for instance, 100 milliseconds = 100 msec = 10o.
The open time of the Yalve, on the other hand, is., for instance, 1 msec = 1OOO and i.s designated ~T2. During this time range ~T2, the lasers 1 to n fire consecutiyely~ wh.ere in the numerical example chosen, the firing interval between two lasers is 40 ~sec = 40 microseconds = 1 ooo 0OO, i.e., that time which it takes a molecule for traversing the irradiation space 3.
Introduci.ng the radiations coming from di~ferent lasers into the irradiation space 3 are now shown diagrammatically in Figures 3 and 4. In this connection, it should also be mentioned that the expansion nozzle 2 is designed in the form of a slit.
At its narrowest point, it has a gap of, for instance, 0.1 to '7.L
0.5 mm and e.xtends over a width.of about 1 m. Figures 3 and 4 show this nozzle 2 in a top view, i.e., onto the broad side.
The number of lasers is obtained according to the numerical example given as ~T2 ~ 1 msec. di.vi.ded by 40 ~sec, or n = 25.
For the sake of clarity, only 10 lasers are shown in Figure 3 al.though as many as 4a or more lasers may be employed. The radiation from the lasers is deflected ~ia mirrors 6 onto a rotating mirror 61, ~h~ch rotates synchronously with the switch-ing frequency of the ~ndividual lasers and directs the laser radiation on the same path into the irradiation space 3. In the latter, the radiation is reflected back and forth at the mirrored walls, so that the entire amount of material present in the irradiation space during the lase~ pulse i5 covered by thi.s radiation of one respective laser.
As already indicated at the outset, two frequencies can be used for exciting the material mixture. The introduction of these two different laser radiations is shown in Figure 4.
The latter again shows in a top vie~ the nozzle 2 and the irradiation space 3, which has a length s. The radiation 91 2a of the lasers L known from Figure 3 ;.s conducted into the irradiation space 3 via the cylinder lens 8 and is reflected there back and forth.
This space has, for instance, the dimensions - 100 cm width, 2 cm length and 0.5 cm thi.ckness. Its side walls consist of KCl or NaCl ~indows, which are ~apor-deposited with dielectric multiple layers of 99.7~ reflectivïty at a wavelength of 0.4 ~m and whi.ch pass the light of 16 ~m unimpeded. There are two windows: 71 and 72 with window 72 corresponding to a 47 ~
segment of a cylinder mirror with.100 cm radius of curyature.
By these measures the 16 - ~m light as well as the 0.4 - ~m light is almost completely adsorbed, as the ratio of the abso:rptivities of UF6 to 16 ~m to that at 0.4 ~m corresponds exactly to the ~nverse ratio of the light paths. Contrary to the light of a . 4 pm wavelength, whi`ch is focuss-ed in order to let it be reflected back and forth sufficiently often in the irradiation space, the 16 - ~m li~ght i~ opened out to 2 cm x 0.5 cm i.n order to ~llum~nate the entire irradiation space uniformly.
A facili.ty of th~s form is also su~table, of course, for a process wh~ch requi:res~onl~ one ki.nd of radi.ation or also only one UV quantum for e~citation and separation.
If the valve 4 were always open, a facility with the dimensions and data described, if cooled to 50 K, would have a material mi.xture throughput of 104 m3~h. The power required to pump the throu~hput therefor would be extremely large. With the method described, however, the required poser is reduced to pump lOQ m3/h., i.e., a power uhich can be obtained uithout ~reat e~fort.
To further illustrate this meth.od, some further statements on th.e dimensi~ns of the fafit-closing YalYe 4 uill be gi.ven. In accordance with. a nozzIe wi.dth of 1 m, thi.s valve 4 also has a wi.dth of 1 m. In this manner it is possible to achi.eve a uniform s-upply~of materi.al mi~ture to the nozzle 2 oyer its enti.re width ~i.a the slots 43 and 44 of the rotor 42.
~ith a s-peed of 600 r.p.m. and a rotor circumference of 20 cm, one obtains for th.e open time ~T2 ~ 1 msec. wi.th. a width of th.e inlet and outlet slots 43 and 44 of 2 ~m. The dis.tance between the housing wall and the rotor can be kept relatiYely small because of the low speed, s.o that a good seal during the clos:ing times of the valve 4 is obtained.
The numerical data mentioned should, of ccurse, be cons:idered only as an example; they do not limit the present method, but should be adapted suitably, according to other method parameters such as, for instance, pulse repitition frequencies, numbers of lasers, etc. Nothing was said about the further processi.ng or the separation proper of the desired excited isotope compound or the enriched is:otope compound, because this can be accompli~hed in accordance with known methods, which ha~e partly been described at the outset. Pulsed lasers suitable for use iP accordance with.the in~ention are known in the art. An example of such laser is proposed for IR
by R. ~akobs et al : Applied Physics LetterS Vol. 29(11), page 710 (.1976). A commerciall~ avai.lable laser (.UY) is made by Lambda Physik, Cottin~en or Molectron Corp., 177 N. ~olfe Road, Sunnyvale, CA 94 086.
The frequencies for excitin~ UF6 are 16 ~m in the IR
range and Q.3 - a . 4 ~m in W range.
In all the methods for isotope-selective excitation, separation is achieved by~ exciting only one isotope compound so that the latter preferentially converts by chemical reaction or otherwise into a chemical compound, whereby this new compound 10 can be separated relatiyely readily by normal mechanical and chemical means from the original mixture of sub.stances. This new compound then contains preferentially the desired isotope such as uranium 235. The separation of isc:topes is of technical interest especially for uranium, si.nce the fissionable isotope uranium 235, which alone i.s usable, is present in the natural uranium only in the amount of û.7% and ~ust be enriched in the nuclear fuel for light-water reactors to about 2 to 3%.
Excitation of the one isotope compound, howeyer, can also be used for ionizing the latter and to make it separable 20 thereby electrically, ox to influence its. dipole behayior in such a manner that deflection by the electric field of the laser radiation itself becomes possible. Further details on laser-induced i.s.otope separation methods by means of physical and chemical separati.on can be found in German Published Non-Prosecuted Applications Numbers 2 311 584 and 2 324 797. Further proposals for th.e isotope separation via selective excitation of molecular energy levels can be found in German Published Non-Prosecuted Application Number 2 459 989, where the use of 1117d~71 wa~el.en~ths in the infrared and ultra-Yiolet ran~e is discussed in particular.
Almost all uranium isotope separation methods start out with the compound UF6, which uranium compound exhibits sufficient vapor pressure for e~fecting i.sotope selective excitation. It has been found, however, th.at selective excitation performed at normal temperatures does not permit the attainment of the desired enrichment values because of the over-lap of the absorption bands, resonance exchan~e and thermally acti.vated reactions. It has been proposed as an improvement to expand the ~aseous isotope mixture adiabatically to temperatures below 100 K and to i.rradiate it before it is condensed, with a laser beam o~ s:ultable frequency contai.ned in a resonator; see in this connection German PubIished Non-Prosecuted Application Number 2 447 762. It haa also been proposed to accomplish the cooling-down of the isotope mi-xture by a neutral, heavily undercooled supplemental gas that is to be admitted, instead of the adiabatic expans.ion, as described in German Published Non-Prosecuted Application Number 2 651 306.
This and other i.sotope separation methods are feasible, with the use of so-called continuous lasers, but such equipment has low output power and the operation is not very efficient, however.
Performing the isotope separation processes with pulsed lasers also h.as its problems. Since the laser pulaes, which are in the order of one nanosecond, are very short and the pulse repetition frequency i.s maximally about 100 Hz, only a very small amount of material can be excited by th.e present methods using ~:~1747i such pulsed lasers, so that the use of ~ulsed lasers in the manner described is disadvantageous in thi.s. respect. It should be recalled in this~ connection that the gas mixture put through must be recirculated a~ain and again because as pre~iously stated only a very small amount of material can be excited, so that enormous pump powers are required res.ultin~ in large capital inyestment and high operati.ng cost.
An object of the present inyention is to provide a process for the economical application of pulsed lasers for the separation of isotopes from a mixture of vaporous isotope compounds, ensuring that the entire mixture of substances put through is irradiated in its entirety and the molecules that can be excited are actually excited.
With the foregoing and other objects in view, there is provided in accordance with the invention a method for the separation of isotopes from a mixture of vaporous isotope compounds by the application of pulsed laser beams to effect selective excitation of one of the is:otope compounds contained therein and subsequent chemical or physi.cal separation of the ~ excited isotope compound, the improvement comprising a) flowing a stream of the mixture of vaporous isotope compounds periodically at constant intervals, b) continuing the flow of the mixture of Yaporous isotope compounds. during each period of flow-for a s.hort time in the range of milliseconds, c) adiabatically expanding each.stream of the mixture of vaporous isotope compounds flowing per~odically to cool the mi.xture to a temperature below 100 K, il:l7L~7~L
d) flowing the cooled mixture of yaporous isotope compounds to an irradiation zone at said intervals, and e) flowing the cooled mixture through the irradiation zone ànd subjecting the cooled mixture during the time of flow duration to consecutive pulses of a plurality of consecutively fired lasers to excite substantially all of the one isotope compound to be selecti.vely excited during flow of the mixture of vaporous isotope compounds through the irradiation zone.
In accordance with the invention there is provided apparatus for controlling the ~low of a mixture of vaporous isotope compounds and adiabatically expanding the mixture of vaporous isotope compounds to cool the ~ixture to a temperature below 100 K, for the separation of isotopes from the mixture by the application of pulsed laser beams to effect selective excitation of one of the isotope compounds, contained therein which comprises a) a slot-shaped expansion nozzle, b) a valve whose outlet extends oyer the entire width of the inlet to th.e expansion nozzle, c) sai,d valYe havi.ng a rotor, rotatable at a constant speed, with two di.ametrically opposite lon~i.tudinal slots, d) a housing with a vapor inlet surroundin~ and sealing the rotor, said rotor when aligned with one slot facing the vapor i.nlet and the other s,lot facing the inlet to the expansion nozzle permits the flow of Yapor through sald valYe~
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described 47~
herein as embodied i.n a method for the separation of isotopes by isotope-selective excitation, it is: neverth.eless not intended to be limited to the details shown, s.ince ~arious modifications may be made therein with.out departing from the spirit of the i.nvention and within the scope and range of equivalents of the claims.
The invention, however, toge.ther with addi.tional objects and advantages thereof will ~e best understood from the following description when read in connecti.on with the accompany-ing drawings, in which:
Figure 1 sh.ows a valve with a rotor, an expansion nozzle and an irradiation space and diagrammatically illustrates the relationship between the irradiation s.pace, expansion nozzle and valve in accordance with the invention, Figure 2 shows a timing diagram i:llustrati.ng the switching sequences of the valve as well as the firing sequences of the lasers, Figure 3 diagrammatically illustrates directing radiations from di.fferent lasers into the i.rradiation space by means of mirrors, and Figure 4 illustrates conducti.ng the radiation through a cylinder lens into the irradiation space.
In accordance with the invention, the vaporous mixture of the isotope compounds as well as of supplemental gases known per se and/or reaction partners are adiabatically expanded at constant time interYals, always for a flow duration in the range of milliseconds, via a nozzIe, and is thereby cooled down to below 100 K. The cooled gas mixture fed at interyals to an irradiation space is exposed duri.ng the entire flow duration to consecutive pulses of consecutiYely fired lasers for substan-tially, quantitati.vely complete isotope-specific excitation.
This method is thus based on the combination of at least two characteristi.cs: To send the gas mixture which is to be fed to the isotope separation facilit~ at continuously repeated i.nter~als for a sho~i~t flow duration through the irradiation space, and to cover it in its entirety radiation-wise by a multiplicit~ of consecuti~ely fired laser equipments of the same frequency. This is based on the following considerations:
Our own tests have shown that with dynami.c cooling of a gas mixture, the selective exci.tati.on and s:eparation of the desired isotope compound must take place on a travel distance of about 2 cm. W;th a jet velocity of the materi.al mixture entering the irradiation space of about 500 m~sec, the flight time of a molecule through. this distance is about 40 ~sec. If one now irradi.ates this enti.re zone of 2 cm length with a laser pulse and makes a further laser pulse follow-after another 4Q ~sec, then the irradiated regions of the materi.al mixture jet follow each other without gap. To this end, however, a laser with a pulse repetition frequency o~ 25 kHz would be requi.red, but these likewise do not yet exi.st with the desired : wavelengths and powex ranges. The requi.red pulse energies are about 1 Ws in the W range ~0.3 to 0.4 pm). and about Q.025 ~s in th.e IR range C16 ~m).
Th.is difficult~ is overcome wi.th. the pre~ent inYention in that the required puls:e repetiti:on frequency is formed by 1~1'^~471 the consecutiye firing of a multi,plicity of identical lasers.
Since, however, the number of these lasers is li~ited, not only for economic reasons but also because of the ph~sical arrange-ment (they all must be arranged so that their radiation goes through the irrad;~ati,on space by the same path), provision is now made that the mater~al mi:xture jet tra~els: through the irradiation chamber only during the radiati`on time of these consecutiyely fired lasers. This is accomplished by inserting ahead of the expansi`,on nozzle a val~e, which transports at periodic inte~Yals, which correspond to the pos.sible pulse repetition fre~uenc~ of a laser, a length-limited material mixture jet through the irradiati.on space.
This procedure will now ~e explained, to illustrate the invention in greater detail, with, the aid o~ an example, referring to Figures 1 to 4.
Figure 1 shows diagrammatically the spatial relationship between the irradiation space 3, the nozzIe 2 and the valve 4.
The procedure is now as follows: The material mixture 16, i.e.
the mixture of vaporous isotope compounds together with supplemental gas and reaction partneL, flows through the line 45 into the valYe 4. The latter cons~ists of a tubular housing 41, to which are connected on the one $ide the feed line 45 and on the other side the expansion nozzle 2. Inside this housing rotates, with constant speed of rotation, a rotor 42 proYided w1th slots 43 and 44 whi.ch are likewi,se arranged di.ametrically opposite each other. When these slots. 43 and 44 establish a connection between the feed li.ne 45 and the nozzle 2, a material mixture jet o~ always the same length'will traveI through the 1~17~71 irradiation space 3. The length o~ this i.rradi.ation space is designated with s. With a jet veloci.ty of 500 m/sec, a molecule traverses this distance in 40 ~sec. If now the front of the gas stream leaving the nozzle has arrived in ~ront of the end of the irradiation space 3, the fi.rst laser is fired, and the next one at intervals of 40 ~sec. each. Thus, a division of the material mixture jet into irradiation zones gl to gn is obtained, which follow each other without a gap. In Figure 1 is shown that situation, in which just the last material jet region gn is being irradiated by the last (the nth) laser. The total length of the material mixture jet leaving the nozzle 2 at intervals is then obtained from the number of lasers n times the length of the irradiation space s.
Figure 2 shows in a timing diagram the switching sequences of the valve 4 as well as of the n lasers. The valve 4 opens the flow path at intervals of ~.Tl, where ~Tl will be assumed to be, for instance, 100 milliseconds = 100 msec = 10o.
The open time of the Yalve, on the other hand, is., for instance, 1 msec = 1OOO and i.s designated ~T2. During this time range ~T2, the lasers 1 to n fire consecutiyely~ wh.ere in the numerical example chosen, the firing interval between two lasers is 40 ~sec = 40 microseconds = 1 ooo 0OO, i.e., that time which it takes a molecule for traversing the irradiation space 3.
Introduci.ng the radiations coming from di~ferent lasers into the irradiation space 3 are now shown diagrammatically in Figures 3 and 4. In this connection, it should also be mentioned that the expansion nozzle 2 is designed in the form of a slit.
At its narrowest point, it has a gap of, for instance, 0.1 to '7.L
0.5 mm and e.xtends over a width.of about 1 m. Figures 3 and 4 show this nozzle 2 in a top view, i.e., onto the broad side.
The number of lasers is obtained according to the numerical example given as ~T2 ~ 1 msec. di.vi.ded by 40 ~sec, or n = 25.
For the sake of clarity, only 10 lasers are shown in Figure 3 al.though as many as 4a or more lasers may be employed. The radiation from the lasers is deflected ~ia mirrors 6 onto a rotating mirror 61, ~h~ch rotates synchronously with the switch-ing frequency of the ~ndividual lasers and directs the laser radiation on the same path into the irradiation space 3. In the latter, the radiation is reflected back and forth at the mirrored walls, so that the entire amount of material present in the irradiation space during the lase~ pulse i5 covered by thi.s radiation of one respective laser.
As already indicated at the outset, two frequencies can be used for exciting the material mixture. The introduction of these two different laser radiations is shown in Figure 4.
The latter again shows in a top vie~ the nozzle 2 and the irradiation space 3, which has a length s. The radiation 91 2a of the lasers L known from Figure 3 ;.s conducted into the irradiation space 3 via the cylinder lens 8 and is reflected there back and forth.
This space has, for instance, the dimensions - 100 cm width, 2 cm length and 0.5 cm thi.ckness. Its side walls consist of KCl or NaCl ~indows, which are ~apor-deposited with dielectric multiple layers of 99.7~ reflectivïty at a wavelength of 0.4 ~m and whi.ch pass the light of 16 ~m unimpeded. There are two windows: 71 and 72 with window 72 corresponding to a 47 ~
segment of a cylinder mirror with.100 cm radius of curyature.
By these measures the 16 - ~m light as well as the 0.4 - ~m light is almost completely adsorbed, as the ratio of the abso:rptivities of UF6 to 16 ~m to that at 0.4 ~m corresponds exactly to the ~nverse ratio of the light paths. Contrary to the light of a . 4 pm wavelength, whi`ch is focuss-ed in order to let it be reflected back and forth sufficiently often in the irradiation space, the 16 - ~m li~ght i~ opened out to 2 cm x 0.5 cm i.n order to ~llum~nate the entire irradiation space uniformly.
A facili.ty of th~s form is also su~table, of course, for a process wh~ch requi:res~onl~ one ki.nd of radi.ation or also only one UV quantum for e~citation and separation.
If the valve 4 were always open, a facility with the dimensions and data described, if cooled to 50 K, would have a material mi.xture throughput of 104 m3~h. The power required to pump the throu~hput therefor would be extremely large. With the method described, however, the required poser is reduced to pump lOQ m3/h., i.e., a power uhich can be obtained uithout ~reat e~fort.
To further illustrate this meth.od, some further statements on th.e dimensi~ns of the fafit-closing YalYe 4 uill be gi.ven. In accordance with. a nozzIe wi.dth of 1 m, thi.s valve 4 also has a wi.dth of 1 m. In this manner it is possible to achi.eve a uniform s-upply~of materi.al mi~ture to the nozzle 2 oyer its enti.re width ~i.a the slots 43 and 44 of the rotor 42.
~ith a s-peed of 600 r.p.m. and a rotor circumference of 20 cm, one obtains for th.e open time ~T2 ~ 1 msec. wi.th. a width of th.e inlet and outlet slots 43 and 44 of 2 ~m. The dis.tance between the housing wall and the rotor can be kept relatiYely small because of the low speed, s.o that a good seal during the clos:ing times of the valve 4 is obtained.
The numerical data mentioned should, of ccurse, be cons:idered only as an example; they do not limit the present method, but should be adapted suitably, according to other method parameters such as, for instance, pulse repitition frequencies, numbers of lasers, etc. Nothing was said about the further processi.ng or the separation proper of the desired excited isotope compound or the enriched is:otope compound, because this can be accompli~hed in accordance with known methods, which ha~e partly been described at the outset. Pulsed lasers suitable for use iP accordance with.the in~ention are known in the art. An example of such laser is proposed for IR
by R. ~akobs et al : Applied Physics LetterS Vol. 29(11), page 710 (.1976). A commerciall~ avai.lable laser (.UY) is made by Lambda Physik, Cottin~en or Molectron Corp., 177 N. ~olfe Road, Sunnyvale, CA 94 086.
The frequencies for excitin~ UF6 are 16 ~m in the IR
range and Q.3 - a . 4 ~m in W range.
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a method for the separation of isotopes from a mixture of vaporous isotope compounds by the application of pulsed laser beams to effect selective excitation of one of the isotope compounds contained therein and subsequent chemical or physical separation of the excited isotope compound, the improvement comprising a) flowing a stream of the mixture of vaporous isotope compounds periodically at constant intervals, b) continuing the flow of the mixture of vaporous isotope compound during each period of flow for a short time in the range of milliseconds, c) adiabatically expanding each stream of the mixutre of vaporous isotope compounds flowing periodically to cool the mixture to a temperature below 100 K, d) flowing the cooled mixture of vaporous isotope compounds to an irradiation zone at said intervals, and e) flowing the cooled mixture through. the irradiation zone and subjecting the cooled mixture during the time of flow duration to consecutive pulses of a plurality of consecutively fired lasers to excite substantially all of the one isotope compound to be selectively excited during flow of the mixture of vaporous isotope compounds through the irradiation zone.
2. Method according to claim 1, wherein the stream of the mixture of vaporous isotope compounds to be adiabatically expanded contains a supplemental gas.
3. Method according to claim 1, wherein the stream of the mixture of vaporous isotope compounds to be subjected to laser irradiation contains a reaction partner which reacts with the excited isotope compound.
4. Method according to claim 2, wherein the stream of the mixture of vaporous isotope compounds to be subjected to laser irradiation contains a reaction partner which reacts with the excited isotope compound.
5. Method according to claim 1, wherein the number of lasers is between 10 and 40.
6. Method according to claim 1, wherein more than one irradiation frequencies are used, and wherein the same number of corresponding lasers is used for each frequency.
7. Apparatus for controlling the flow of a mixture of vaporous isotope compounds and adiabatically expanding the mixture of vaporous isotope compounds to cool the mixture to a temperature below 100 K, for the separation of isotopes from the mixture by the application of pulsed laser beams to effect selective excitation of one of the isotope compounds contained therein which comprises a) a slot-shaped expansion nozzle, b) a valve whose outlet extends over the entire width of the inlet to the expansion nozzle, c) said valve having a rotor, rotatable at a constant speed, with two diametrically opposite longitudinal slots, d) a housing with a vapor inlet surrounding and sealing the rotor, said rotor when aligned with one slot facing the vapor inlet and the other slot facing the inlet to the expansion nozzle permits the flow of vapor through said valve.
8. Apparatus according to claim 7, wherein an enclosed area as the irradiation space immediately follows the expansion nozzle, and wherein a plurality of consecutively fired lasers and deflection mirrors are arranged outside the irradiation space in such a manner that the irradiation pulses emitted by the lasers take the same path within the irradiation space.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2810791.7 | 1978-03-13 | ||
| DE19782810791 DE2810791C3 (en) | 1978-03-13 | 1978-03-13 | Method and device for separating a gaseous mixture of isotope compounds |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1117471A true CA1117471A (en) | 1982-02-02 |
Family
ID=6034279
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000323342A Expired CA1117471A (en) | 1978-03-13 | 1979-03-13 | Method for the separation of isotopes by isotope-selective excitation |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS54126895A (en) |
| AU (1) | AU526626B2 (en) |
| CA (1) | CA1117471A (en) |
| DE (1) | DE2810791C3 (en) |
| FR (1) | FR2419753A1 (en) |
| GB (1) | GB2016795B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5579030A (en) * | 1978-12-08 | 1980-06-14 | Rikagaku Kenkyusho | Uranium isotope concentration unit |
| DE3010178C2 (en) * | 1980-03-17 | 1985-10-03 | Kraftwerk Union AG, 4330 Mülheim | Slotted nozzle equipped with a quick-acting valve to induce pulsed gas flows |
| US4401507A (en) * | 1982-07-14 | 1983-08-30 | Advanced Semiconductor Materials/Am. | Method and apparatus for achieving spatially uniform externally excited non-thermal chemical reactions |
| DE3735200A1 (en) * | 1987-10-17 | 1989-05-03 | Siemens Ag | Method of producing laser radiation at a high repetition rate in the infrared band, especially for uranium isotope separation |
| DE3828052A1 (en) * | 1988-08-18 | 1990-02-22 | Siemens Ag | Slot die arrangement and use thereof for the adiabatic expansion of a gas mixture in the separation of uranium isotopes |
| GB2256079B (en) * | 1991-05-24 | 1994-10-05 | Synergetic Resources Ltd | A simple high selectivity, high dissociation system for laser isotope separation |
| DE4331267A1 (en) * | 1993-09-15 | 1995-03-16 | Uranit Gmbh | Multiple-orifice nozzle arrangement |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3924937A (en) * | 1974-01-30 | 1975-12-09 | Jersey Nuclear Avco Isotopes | Method and apparatus for sequentially combining pulsed beams of radiation |
| IL47139A (en) * | 1974-05-13 | 1977-07-31 | Jersey Nuclear Avco Isotopes | Method and apparatus for impact ionization of particles |
| DE2447762C2 (en) * | 1974-10-07 | 1987-10-01 | Kraftwerk Union AG, 4330 Mülheim | Method and device for separating mixtures of substances and application of the same for the production of chemical compounds |
| US4000423A (en) * | 1974-12-05 | 1976-12-28 | Jersey Nuclear-Avco Isotopes, Inc. | Fast response high temperature evaporation control |
| DE2458563A1 (en) * | 1974-12-11 | 1976-06-16 | Uranit Gmbh | PROCESS FOR ISOTOPE SEPARATION BY USING LASER |
| US4734177A (en) * | 1975-11-26 | 1988-03-29 | The United States Of America As Represented By The United States Department Of Energy | Laser isotope separation |
-
1978
- 1978-03-13 DE DE19782810791 patent/DE2810791C3/en not_active Expired
-
1979
- 1979-02-27 FR FR7905076A patent/FR2419753A1/en active Granted
- 1979-03-07 JP JP2660679A patent/JPS54126895A/en active Granted
- 1979-03-12 GB GB7908555A patent/GB2016795B/en not_active Expired
- 1979-03-13 AU AU45030/79A patent/AU526626B2/en not_active Ceased
- 1979-03-13 CA CA000323342A patent/CA1117471A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS54126895A (en) | 1979-10-02 |
| AU4503079A (en) | 1979-09-20 |
| AU526626B2 (en) | 1983-01-20 |
| GB2016795B (en) | 1982-06-03 |
| DE2810791C3 (en) | 1985-06-05 |
| FR2419753B1 (en) | 1983-07-18 |
| GB2016795A (en) | 1979-09-26 |
| DE2810791B2 (en) | 1980-01-31 |
| FR2419753A1 (en) | 1979-10-12 |
| DE2810791A1 (en) | 1979-09-20 |
| JPS62730B2 (en) | 1987-01-09 |
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