JPH07170B2 - Isotope separation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of use) The present invention is directed to ionization by selectively exciting only a specific isotope in a metal raw material containing plural kinds of isotopes by laser light. The present invention relates to an isotope separation device that electrically separates and collects selected isotopes.

(Prior Art) A metal atom isotope separation apparatus using a laser beam is used, for example, in a uranium enrichment process for producing a fuel for a nuclear reactor.

FIG. 6 is a block diagram conceptually showing a conventional isotope separation device by the laser method. The isotope separation device 1 is composed of a vacuum container 2 that hermetically houses a main body in a substantially vacuum state and each device that constitutes the main body, and a metal raw material 3 containing a plurality of types of isotopes.
Are housed in a thermochemically resistant evaporation crucible 4.

On the other hand, the electron beam 6 emitted from the linear electron gun 5
The metal raw material 3 which is deflected by the deflection magnetic field and accommodated in the evaporation crucible 4 is irradiated. The metal raw material 3 that has been irradiated with the electron beam 6 is heated to about 2700 ° K, evaporates through a molten state, and forms a vapor stream 7 of isotope metal. The vapor stream 7 is guided by a collimator 8 so as to flow in a predetermined direction.

In the vapor stream 7, a specific isotope for the purpose of separation and recovery,
Other isotopes not intended for recovery and metal atoms are mixed. Next, the vapor stream 7 is irradiated with a laser beam 9 that selectively excites only a specific isotope. here,
The laser light 9 is a laser light having a wavelength equal to the resonance excitation energy of a specific isotope. The excited specific isotope receives laser light in a stepwise manner, and electrons in the outer shell of the atom are expelled to become an ionized isotope having a positive charge.

A product recovery electrode 10 formed by alternately arranging positive electrodes and negative electrodes is provided in the passage of the vapor flow 7, and the vapor flow 7 containing an ionized isotope is formed between the product recovery electrodes 10. When passing through the electric field space, only specific ionized isotopes having a positive charge are attracted to the surface of the negative electrode and collected as a product.

On the other hand, the vapor flow containing non-ionized isotopes and neutral metal atoms passes between the product recovery electrodes 10 without being affected by the electric field, and is attached and recovered to the waste product recovery electrode 11 arranged on the secondary side. Is configured to.

(Problems to be Solved by the Invention) In order to improve the separation coefficient in the isotope separation device having the above configuration, it is important to selectively excite only a specific isotope for recovery. Therefore, it is necessary to accurately match the wavelength of the laser light to be irradiated with the resonance wavelength of a specific isotope.

For example, as a laser light source used in the uranium concentration process,
Dye lasers with a wavelength range of 4000-6000Å have been adopted. Since the uranium atom has a large number of resonance absorption lines in the above wavelength range, it is possible to obtain a laser beam that selectively excites the target U-235 by tuning the wavelength of the dye laser.

However, in order to confirm whether or not the actual device is operating under the optimum operating conditions, it is difficult to always accurately calibrate the wavelength of the laser beam applied to the vapor flow.
That is, the shift of the resonance wavelength of the isotope is generally about 0.1 Å, but considering the splitting of the absorption line due to the hyperfine structure of the isotope nucleus, a finer 0.01% is needed to set the wavelength of the laser light to an appropriate value. Å Fine adjustment accuracy is required.

However, it is difficult to equip the isotope separation device with a wavelength meter having a measurement accuracy of up to 0.01 Å by the conventional technology.
Therefore, the suitability of the wavelength of the laser light is judged by the amount of the target isotope recovered per unit time or the content ratio of the specific isotope in the recovered product. That is, it takes a long time to understand the effect of adjusting the wavelength of the laser light, and there is a problem that the operation management of the isotope separation device becomes complicated.

The present invention was devised in order to solve the above problems, a mechanism for measuring fluorescence generated when a specific isotope excited by irradiation of laser light returns to the ground state again, and its ratio It is configured so that the suitability of the wavelength of the laser light during irradiation can be grasped depending on the size of, and it is possible to appropriately judge and adjust the suitability of the wavelength of the laser light during operation
It is an object of the present invention to provide an isotope separation device which has easy operation management and high separation efficiency.

[Structure of Invention]

(Means for Solving Problems) An isotope separation device according to the present invention heat-evaporates a metal raw material containing a plurality of types of isotopes to generate a vapor flow, and a laser beam having a predetermined wavelength is generated in the vapor flow. Is irradiated to selectively excite a specific isotope in the vapor flow, further ionize through an ionization process, and in the isotope separation device that separates this ionized isotope by an electric field, the excited isotope atom is It is characterized in that a fluorescence measuring device for detecting fluorescence generated when transitioning to a ground state is provided.

(Operation) In the isotope separation device having the above-described configuration, the isotope atom selectively excited by the laser light is further stepwise absorbed by the laser light having the predetermined wavelength and ionized to become the ionized isotope. Some of the excited atoms return to the ground state again over time. At this time, the atoms generate fluorescence having a wavelength equal to the wavelength of the absorbed laser light.

Since the amount of this fluorescence generated is proportional to the number of excited atoms that are generated, it is possible to judge whether the wavelength of the laser light being irradiated is appropriate or not based on the magnitude of this measured value.
Further, if the wavelength is appropriately adjusted so that the ratio of ionized isotopes in the entire vapor flow is maximized, the separation efficiency in the isotope separation device can be constantly maintained high.

Note that the amount of generated fluorescence is relatively small means that the number of isotope atoms in the excited state in the vapor flow is relatively small, and the wavelength of the irradiating laser beam is that of the isotope for the purpose of recovery. It is judged that the wavelength deviates from the wavelength of the resonance absorption line. In this case, the optimum operating state can be maintained by adjusting the wavelength of the laser light in the direction in which the amount of fluorescence generated is increased. Incidentally, the wavelength of the laser light can be adjusted with minute precision of about 0.001 Å according to the sensitivity of the amount of fluorescence generated.

That is, since the amount of fluorescence measured by the fluorescence measurement device is used as a criterion, the wavelength of the laser light can be adjusted and maintained at an appropriate value as appropriate, resulting in high isotope separation efficiency and during operation. Since the excited state of a specific isotope can be directly monitored in, the operation management becomes extremely easy.

(Embodiment) Next, an embodiment of the present invention will be described with reference to the accompanying drawings.

The isotope separation device according to the present invention is characterized in that it is provided in a fluorescence measurement device for measuring fluorescence generated when an excited isotope transits to a ground state, and FIG. 1 and FIG. It is configured as shown in.

That is, a vaporizing crucible 4 containing a metal raw material 3 containing a plurality of isotopes, and a linear electron gun that irradiates the metal raw material 3 with an electron beam 6 to heat and vaporize the metal raw material 3 to generate a vapor stream 7. And 5 are arranged at the bottom of the vacuum container 2. Above the evaporation crucible 4, a collimator 8 for guiding the flow of the vapor stream 7 in a predetermined direction is provided. The passage of the vapor flow 7 on the secondary side of the collimator 8 is irradiated with the laser beam 9 and only specific isotopes are selectively excited to be ionized isotopes.

A product recovery electrode 10 and a waste product recovery electrode 11 are provided along the flow of the vapor stream 7 above the irradiation region of the laser light 9. The product recovery electrode 10 is formed by alternately arranging a plurality of positive electrodes and negative electrodes in parallel. A vapor hole 13 for introducing a part of the vapor flow 7 into the fluorescence measuring device 12 is formed in the center of the waste product collecting electrode 11 arranged on the secondary side of the product collecting electrode 10.

A specific configuration of the fluorescence measuring device 12 is illustrated in FIG. That is, the fluorescence measuring device 12 includes a fluorescence concentrator 14 that detects and collects the fluorescence generated in the vapor flow, and a photomultiplier tube 15 that converts the fluorescence collected by the fluorescence concentrator 14 into an electric signal. And an integrator 16 that analyzes the waveform of the fluorescence generation signal output from the photomultiplier tube 15, and calculates the deviation from the standard value of the fluorescence generation amount at the wavelength of the laser light that is being radiated according to the waveform analysis result. The wavelength controller 18 outputs a wavelength control signal to the optical oscillator 17. The fluorescence condenser 14 and the photomultiplier tube 15 are connected by an optical fiber 19.

In the isotope separation device having the above-mentioned configuration, the metal raw material 3 containing a plurality of isotopes is heated and evaporated to form a vapor stream, and then the vapor stream 7 is irradiated with the laser beam 9 so that only specific isotopes are produced. It is selectively excited to become an ionized isotope. The ionized isotope is separated and recovered in a predetermined direction by the electric field formed on the product recovery electrode 10.

On the other hand, the vapor stream 7 containing non-ionized neutral atoms passes through the product recovery electrode 10 and is mostly collected by the waste product recovery electrode 11. Part of the steam flow 7 reaching the waste collection electrode 11 is a steam hole
It passes through 13 and is introduced to the front surface of the fluorescence collector 14 of the fluorescence measuring device 12. The branched laser light 20 is irradiated from a direction perpendicular to the vapor flow 7 introduced to the front surface of the fluorescent light concentrator 14. The branched laser light 20 is obtained by branching from the laser light 9 by a partial reflection mirror 21 and a total reflection mirror 22 provided in the course of the laser light 9 as shown in FIG.

The specific isotope in the vapor stream 7 is selectively excited by the irradiation of the branched laser beam 20, and reaches an excited state Ei having a high energy level as shown in FIG. Further, some of the excited isotope atoms transit to the original ground state E ₀ after a certain lifetime. At this time, the isotope atom emits fluorescence corresponding to the wavelength of the absorbed laser light.

The generated fluorescence is detected and collected by a fluorescent light concentrator 14 provided so as to face in the direction perpendicular to the vapor flow 7. The detected fluorescence is transmitted by the optical fiber 19 to, for example, a photomultiplier tube 15 of the Photomal type, and is converted into an electric signal there.
The fluorescence generation signal 23 output from the photomultiplier tube 15 is subjected to waveform analysis by, for example, a boxcar type integrator 16, the analysis result is transmitted to the wavelength controller 18, and the wavelength controller 18 irradiates the laser. A deviation from the standard value of the fluorescence generation amount at the wavelength of light is calculated, and a wavelength control signal 24 for adjusting the wavelength in the direction of eliminating the deviation is output to the laser light oscillation device 17.

The photodiode 25 is connected to the integrator 16 in order to reduce a measurement error caused by the scattered light of the irradiated laser light 9 being detected by the fluorescence condenser 14 together with the fluorescence.
When the timing of the pulse of the laser light 9 is input as a trigger signal of the integrator 16 by the photodiode 25, only fluorescence outside the irradiation time of the laser light 9 can be detected.

That is, according to the isotope separation device 1 of the present embodiment, the excited state of a specific isotope for the purpose of recovery is determined by the fluorescence measuring device 12
It can be confirmed by the amount of fluorescence detected in. Therefore, it is possible to appropriately judge the wavelength of the radiated laser light and adjust the wavelength even during operation, in an appropriate short time, and it is possible to always operate the device under optimum operating conditions. Therefore, the isotope separation efficiency is high and the operation management is extremely simplified.

Next, another embodiment will be described with reference to FIG.

The embodiment shown in FIG. 5 includes, in addition to the laser light oscillator 17 provided in the embodiment shown in FIG. 3, a laser light oscillator 17a for secondary excitation and a laser light oscillator for ionization ionization. It is equipped with 17b. The isotope atom is excited stepwise by being irradiated with laser light having different wavelengths in three steps, and is further ionized and ionized. Further, the laser light oscillators 17 and 17a for the primary excitation and the secondary excitation are individually provided with the fluorescence measuring device 12
Will be equipped one by one. And two fluorescence measuring devices 12
The amount of fluorescence of each isotope atom in the excited state is estimated by independently measuring the amount of fluorescence generated in each stage of the primary excitation stage and the secondary excitation stage, and the laser used in each stage. Whether or not the wavelength of light is appropriate can be determined individually, and if there is a deviation, it can be adjusted to an appropriate value.

According to this example, it is possible to set the wavelength of the laser light substantially accurately with a precision of up to about 0.001 Å based on the amount of fluorescence generated, and to greatly improve the isotope separation efficiency. can do.

〔The invention's effect〕

The isotope separation device of the present invention is equipped with a fluorescence measuring device for measuring the amount of fluorescence generated corresponding to the excitation state of a specific isotope for the purpose of recovery, and operates the isotope excitation state. You can check inside. Therefore, it is possible to appropriately adjust the wavelength of the laser light being used, and it is possible to always operate the device under optimum operating conditions. Therefore, the isotope separation efficiency is high and the operation management is easy.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing one embodiment of the isotope separation device according to the present invention, FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1, and FIG. System diagram showing an example,
FIG. 4 is an explanatory view showing a state in which isotope atoms generate fluorescence, FIG. 5 is a system diagram showing another embodiment, and FIG. 6 is a cross section schematically showing the constitution of a conventional isotope separation device. It is a side view. 1 ... Isotope separation device, 2 ... Vacuum vessel, 3 ... Metal raw material, 4 ... Evaporating crucible, 5 ... Linear electron gun, 6 ...
Electron beam, 7 ... Vapor flow, 8 ... Collimator, 9 ...
Laser light, 10 …… Product recovery electrode, 11 …… Waste product recovery electrode,
12 …… Fluorescence measuring device, 13 …… Vapor hole, 14 …… Fluorescent concentrator, 15 …… Photomultiplier tube, 16 …… Integrator, 17,17a, 17b…
… Laser light oscillator, 18 …… Wavelength controller, 19 …… Optical fiber, 20 …… Branch laser light, 21 …… Partial reflection mirror, 22
...... Total reflection mirror, 23 ...... Fluorescence generation signal, 24 ...... Wavelength control signal, 25 …… Photodiode, Ei …… Excited state, E ₀
…… Ground state.

Claims (3)

[Claims] 1. A metal raw material containing a plurality of isotopes is heated and evaporated to generate a vapor stream, and the vapor stream is irradiated with laser light having a predetermined wavelength to selectively select a particular isotope in the vapor stream. Fluorescence measurement to detect the fluorescence generated when the excited isotope atom makes a transition to the ground state in an isotope separation device that excites to ionization, ionizes it through an ionization process, and separates this ionized isotope by an electric field An isotope separation device characterized by comprising a device. 2. A fluorescence measuring device comprising: a fluorescence concentrator for detecting and condensing fluorescence generated in a vapor stream; and a photomultiplier tube for converting the fluorescence condensed by the fluorescence concentrator into an electric signal. , The integrator that analyzes the waveform of the fluorescence emission signal output from the photomultiplier tube, and the deviation from the standard value of the fluorescence emission amount at the wavelength of the laser light that is being irradiated is calculated based on the waveform analysis result, and the deviation is eliminated. The isotope separation device according to claim 1, further comprising a wavelength controller that outputs a wavelength control signal for adjusting a wavelength in a direction to a laser light oscillation device. 3. The isotope separation device according to claim 1 or 2, wherein the fluorescence measuring device is individually provided in a plurality of laser light oscillating devices that oscillate laser lights having different wavelengths.