DE2525315A1 - METHOD AND DEVICE FOR URANIUM ENrichment - Google Patents

Description

Patent attorneys Dipl.-Ing. R. B E ETZ sen. Dipl.-Ing. K. LAMPRECHT Dr.-Ing. R. B E ETZ jr.

8 Munich 22, steinsdorfstrasse 10 Tel. (088) 227201/227244/295910

Telegr. Allpatent Munich Telex 522O48

310-24.29OP (24.291H)

6. 6. 1975

INSTRUMENTS S.A., Ivry-sur-Seine (France)

Process and device for uranium enrichment

The invention relates to a method for enriching natural uranium by double irradiation or exposure to radiation that causes selective photoionization of certain isotopes, as well as an apparatus for performing this method.

The basic process for isotope separation is generally known, in which one isotope is selectively excited in an isotope mixture, namely under
Exposure to a first narrow radiation that

S09817 / 071B

alone can excite the atoms of this isotope to an energy level that differs from their basic level. at With such a procedure, the excited atoms and only these subsequently are brought to an ionization level excited by a second radiation of a suitably chosen wavelength. The atoms so ionized will be then separated by an electric field.

It is the object of the invention to improve such a method and such a device, to achieve a high degree of enrichment.

A process for the enrichment of natural uranium, which consists of a mixture of several isotopes, in particular the uranium isotopes 235 and 238, in which the uranium in the atomic vapor state is exposed to a first radiation from a very monochromatic dye laser in order to selectively the atoms of a single isotope to a first excitation level, and the uranium in the vapor state is simultaneously acted upon by a second radiation in order to excite those atoms that have been excited by the first radiation to an ionization level above, is characterized according to the invention that for selective ionization of uranium 235 or 238 a continuous laser with rhodamine 6g or B is used for the first radiation and the resonator of the laser is optically tuned to a wavelength that lies in the laser emission spectrum of rhodamine 6g or B, according to an energy level of the uranium, the one sufficient isotope distance that is, one of the following reference wavelengths: 5,500.69, 5,511.49, 5,557.87, 5,564.17, 5,610.89, 5,620.78, 5,621, 51, 5,634.32, 5,634 , 38, 5 780.59, 5 781.95, 5 782.81,

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- "5 -

5,915, ^ 0, 5,971.50, 5,976.32, 5,986.10, 6,077.29 A, and that the exact wavelength for each reference wavelength based on the spectral hyperfine structure is around the reference wavelength is determined by the hyperfine spectral line corresponding to the isotope to be ionized 235 or 2j58 is retained.

The following reference wavelengths are preferably retained:

5 780.59 A or 5 915, ^ 0 A or 5 986.10 A, especially the wavelength 5,915.40 A.

A device for carrying out the method according to the invention is characterized by:

a vacuum melting furnace with a heated crucible containing uranium to be evaporated and enriched,

a continuous laser with rhodamine 6g or B, whose beam penetrates the furnace through two windows in such a way that vapors emanate from the crucible,

a device for subjecting the uranium vapors to a second, ionizing radiation, and

a cathode at negative potential.

The device for subjecting the uranium vapors to a second radiation preferably consists of one another continuous laser whose beam is the same as the first laser beam in the emission zone of uranium vapors Crosses.

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The invention is explained in more detail with reference to the drawing. Show it:

Fig. 1 and 2 very schematically an embodiment the device according to the invention, namely

Fig. 1 is a diametrical section through the furnace for vaporizing the uranium, the section through the axis of the first excitation laser is placed, and

2 shows a plan view of the relative position of the two lasers when for the final ionization a laser is also used for the excited atoms.

According to FIG. 1, the device according to the invention has a vacuum melting furnace, which can be a simple vacuum bell jar 1, the internal volume of which is connected to a vacuum pump 2. A crucible ~ $, e.g. B. made of tungsten, is heated by Joule heat and contains natural uranium to be enriched,

A beam from a continuous ehodamine laser passes through the furnace. In the usual way, the laser has an active medium J, which is formed here by a beam of rhodamine 6g or B, which is excited by an excitation 8. The beam is concentrated by means of an objective 9 between first optics 10 with a mirror, which has a multi-dielectric coating, and a prism dispersion system 12 with likewise multi-dielectric reflective coating on one of the surfaces of the prism.

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In the present embodiment, the furnace is arranged so that the laser beam through the window 14 and 15 is penetrated, so that uranium vapors 17 emanating from the crucible 3 are within the laser resonator are located.

The optical tuning of the laser is made so that in the laser emission spectrum of rhodamine 6g or B a wavelength is obtained which corresponds to a reference spectral line of the uranium spectrum for which the The isotope distance of the hyperfine spectral lines with respect to the isotopes 235 and 238 is large enough. One can too for this purpose use the following wavelengths as reference wavelengths: 5 500.69 X, 5 5U, 49, 5 557.57, 5 564.17, 5 610.89, 5 620.78, 5 621.51, 5 634.32, 5,634.33, 5,780.59, 5,781.95, 5,782.81, 5,915.40, 5,971.50, 5,976.32, 5,986.10, 6,077.29.

If you z. B. as preferred reference wavelengths selects the values 5 780.59 or 5 915.4o or 5 986.10 S, are the corresponding isotope shifts from uranium 23c to uranium 235 corresponding to + 270 mK, - 28o mK and - 360 mK.

If one then looks at the uranium atoms 235 or 238 want to ionize, the wavelength of the laser is set to the exact value that corresponds to the isotope to be ionized is own. These precise values are given by the hyperfine structure of the reference spectral line under consideration;

, ο z. B. for the preferred spectral line 5,915.40 Å the details of its hyperfine structure in "Journal de physique ", Volume 34, October 1973, p. 805.

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In order to then bring the excited atoms and these alone to the ionization potential, one can Use wavelengths from 3100 to 65OO A, and if necessary even lower wavelengths in the ultraviolet range. You will e.g. B. by a helium-neon or krypton laser generated, or a laser with ionized argon or a dye laser, or by an electric one Arc with xenon or spectrally filtered mercury or by any other laser or electric arc that can emit the ionization wavelength.

The rhodamine laser to a first energy level excited atoms, which are then ionized by the second radiation, are then released by a negative potential cathode I9 captured.

As a precaution, it should be noted that various modifications of the specified embodiment are possible are. The uranium vapors can also be exposed to the laser beam outside the actual laser resonator such a procedure still has the advantage of a higher degree of efficiency. It goes without saying that if the ionization radiation is also generated by a laser, its arrangement relative to the vacuum evaporation furnace equal to that of the excitation laser can; Fig. 2 shows such an example of the position of the axes of the two lasers.

It is also possible to evaporate the uranium in atomic form by methods other than vacuum evaporation to win, e.g. B. by chemical transition reactions or by methods such. B. for atomic absorption can be used.

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Claims (9)

Expectations 1. Process for the enrichment of natural uranium, the consists of a mixture of several isotopes, in particular the uranium isotopes 235 and 238, in which the uranium exposed in the atomic vapor state with a first radiation from a very monochromatic dye laser is to selectively excite the atoms of a single isotope to a first excitation level, and where the Uranium in the vapor state is simultaneously exposed to a second radiation to those atoms which have been excited by the first radiation to excite to an ionization level above, thereby characterized in that for selectively ionizing uranium 235 or 238 for the first radiation a continuous laser with rhodamine 6g or B used and optically the resonator of the laser on a Wavelength is tuned, which is in the laser emission spectrum of rhodamine 6g or B, and accordingly an energy level of the uranium that is sufficiently isotopic, d. H. one of the the following reference wavelengths: 5 500.69, 5 511.49, 5 557.87, 5 564.17, 5 610.89, 5 620.78, 5 621.51, 5 63 ^, 32, 5 634.38, 5 780.59, 5 781.95, 5 782.81 , 5,915.40, 5,971.50, 5,976.32, 5,986.10, 6,077.29 A, and that the exact wavelength for each reference wavelength based on the spectral hyperfine structure around the reference wavelength is determined by the hyperfine spectral line corresponding to the isotope 235 or 238 to be ionized is retained. 609817/0718 2. The method according to claim 1, characterized in that the reference wavelength 5 780.59 A is used for the first or excitation radiation. 3. The method according to claim 1, characterized in that the reference wavelength for the first or excitation radiation 5,915.4o A is used. 4. The method according to claim 1, characterized in that for the first or excitation radiation, the reference wavelength 5,986.10 A is used. 5. The method according to any one of the preceding claims, characterized in that the uranium vapors in the resonator of the excitation laser. 6. The method according to any one of the preceding claims, characterized in that the second or ionization radiation by means of a second continuous laser is produced. 7. Device for performing the method according to one of the preceding claims, characterized by: a vacuum melting furnace (1) with a heated crucible (j5), the uranium to be evaporated and enriched contains, a continuous laser (7) with rhodamine 6g or B, the beam of which passes through the furnace through two windows (14, 15) in such a way that vapors (I7) emanate from the crucible (3), 609817/0718 a device for subjecting the uranium vapors to a second, ionizing radiation, and a cathode (19) at negative potential. 8. Apparatus according to claim ¹ J, characterized by a second continuous laser for generating the second or ionization radiation. 9. Apparatus according to claim 7 or 8, characterized in that the vacuum evaporation furnace (1) is located in the resonator of the excitation laser. 609817/0718 Blank page