JPH0570491B2 - - Google Patents

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to an isotope separation method and apparatus using laser light, and in particular to reducing the amount of adhesion of a vapor flow colliding with a vapor recovery plate. The present invention relates to an isotope separation method and apparatus that improves the separation and recovery efficiency of isotopes as products.

(Prior art) Isotope separation devices that use laser light generally heat and melt a metal raw material containing multiple types of isotopes, such as uranium metal raw material, to evaporate it, and irradiate the generated metal vapor flow with laser light. It is configured to selectively cationize a specific isotope, such as U-235, contained in the vapor flow, apply an electric field to the cationized isotope, separate it, and recover it.

Conventionally, this type of isotope separation apparatus is constructed as shown in FIG. 6 and FIG.
An evaporation crucible 2 containing a raw material 1 is installed.
The evaporation crucible 2 has excellent thermochemical resistance, and the raw material 1 is made of uranium metal containing multiple types of isotopes. This raw material 1 is irradiated with an electron beam 4 emitted from an electron gun 3 and bent by a deflecting magnetic field. The raw material 1 is heated to melt and evaporate, producing a vapor stream 5.

This steam flow 5 is enclosed in a fan-shaped steam enclosure (not shown) whose diameter expands upward.
A recovery electrode 6 is disposed in the flow path of the vapor flow 5 in the upper part of the vapor enclosure.

The recovery electrode 6 includes a plurality of positive electrodes 7 to which a positive potential is applied and a plurality of negative electrodes 8 to which a negative potential is applied relative to each other.
and are alternately arranged substantially parallel to the flow direction of the vapor flow 5, and a photoreactive portion 9 is formed between both electrodes. A pulse laser beam 10 that selectively excites and ionizes only a specific isotope (U-235) is irradiated in a direction perpendicular to the vapor flow 5 introduced into the photoreaction section 9 (in the direction perpendicular to the paper in FIG. 7). be done. The pulsed laser beam is oscillated from a laser beam oscillation device 11 disposed in the longitudinal direction of the photoreaction section 9 . The vapor flow 5 causes a photoreaction by the pulsed laser beam 10, and only a specific isotope (U-235) contained in the vapor flow 5 is selectively excited and ionized with a certain probability to become an ionized isotope.

The ionized U-235 isotope is transferred to the positive electrode 7.
It is deflected by an electric field created by applying a predetermined voltage between the negative electrode 8 and the negative electrode 8, and is attracted and collected on the surface of the negative electrode 8.

On the other hand, the vapor flow 5 containing isotopes that have not been ionized by the irradiation with the pulsed laser beam 10, such as U-238 or neutron metal atoms, is not affected by the electric field formed in the recovery electrode 6 and is The vapor recovery plate 12 provided above the recovery electrode 6
It collided with and was recovered.

Here, the steam recovery plate 12 is formed into an upwardly curved arc plate shape, and the steam flow 5 is directed to the steam recovery plate 1.
It adheres to the bottom surface of 2 or is reflected. The adhered metal vapor stream 5 liquefies over time, flows down along the curved inner surface of the vapor recovery plate 12, and is recovered as a waste product.

(Problems to be Solved by the Invention) However, according to the conventional isotope separation method and device, the ionized isotope generated in the photoreaction part in the recovery electrode is transferred to the vicinity of the recovery electrode along with the flow of vapor. There is a problem in that there is a high rate of vapor diffusion and partially escaping from the recovery electrode, and in particular, a large amount of vapor adheres to the vapor recovery plate placed above the recovery electrode, leading to a decrease in product recovery efficiency. Ta.

For this reason, conventional measures have been taken to prevent the vapor flow from escaping by configuring the recovery electrode and the vapor recovery plate closer to each other; however, certain ionized isotopes that are intended for recovery may adhere to the vapor recovery plate. There was also a problem in which the ratio increased on the contrary.

Attempts have also been made to increase the efficiency of recovering ionized isotopes by increasing the voltage applied between the electrodes of the recovery electrode and increasing the electric field strength. However, exposing the vapor flow to a strong electric field causes the so-called Schüttarch effect, which causes the splitting of the excited levels of isotope atoms and a decrease in the excitation rate, resulting in ionized isotopes generated by photoreactions. The opposite effect has also been confirmed, which is a decrease in the number of particles and a decrease in the amount of separation and recovery.

The present invention has been made to solve the above problems, and provides an isotope separation method that can reduce the proportion of vapor flow adhering to the vapor recovery plate and improve the recovery efficiency of isotopes as products. and equipment.

[Structure of the invention]

(Means for solving the problem) The isotope separation method according to the first invention of the present application is as follows:
A vapor stream is generated by heating and evaporating a raw material containing multiple types of isotopes, and this vapor stream is introduced into a recovery electrode formed by alternately arranging a positive electrode and a negative electrode. The ionized isotope is generated by irradiation with a pulsed laser beam that selectively ionizes the isotope, and the ionized isotope is collected by applying a voltage from a pulsed power supply between the electrodes to form an electric field. By applying a voltage equal to or lower than the positive electrode voltage to a vapor recovery plate that separates and recovers a specific isotope by deflecting it in the direction, and recovers the vapor flow that passes through the recovery electrode section without being separated and recovered, Forms electric lines of force that converge from the vapor recovery plate and the positive electrode to the negative electrode, prevents the movement of ionized isotopes that diffuse toward the vapor recovery plate due to the deflection force of the electric force lines, and recovers the ionized isotopes. It is characterized by focusing in the direction of the negative electrode of the electrode.

Further, the isotope separation device according to the second invention of the present application includes a steam generation device that generates a vapor flow by heating and evaporating a raw material containing multiple types of isotopes, and a vapor generation device that irradiates the vapor flow with pulsed laser light. A laser beam oscillation device that selectively ionizes specific isotopes contained in the vapor flow, a recovery electrode formed by alternately arranging positive and negative electrodes parallel to the flow direction of the vapor flow, and an ionization A pulsed power source that applies a predetermined voltage between electrodes in order to separate and recover isotopes by deflecting them by an electric field, and a vapor recovery plate that recovers a vapor flow that has passed through the recovery power source, the pulsed power source being at least pulsed. The present invention is characterized in that a pulsed positive electrode voltage is applied to the positive electrode with a delay of the pulse width of the laser beam, and a pulsed positive voltage that is less than the pulsed positive electrode voltage is applied to the vapor recovery plate.

(Function) According to the present invention, a voltage for isotope separation and recovery is applied to the recovery electrode, and a voltage is also applied to the vapor recovery plate to form electric lines of force that focus the negative electrode from the vapor recovery plate. Therefore, the ionized isotope attempting to diffuse toward the vapor recovery plate is prevented from diffusing by the electric lines of force, and is further deflected toward the cathode.

Therefore, the ionized isotope to be recovered is prevented from adhering to the vapor recovery plate, and the vapor flow containing the ionized isotope is effectively prevented from escaping to the surrounding area, and the isotope is Separation and recovery efficiency is greatly improved.

In addition, since the voltage applied to the vapor recovery plate is set to a low value that is equal to or lower than the voltage applied to the positive electrode, light is generated by the electric lines of force formed by that voltage. Reactions are rarely affected. In other words, the excitation level of the isotope atom does not split or the excitation rate decreases, and the separation and recovery efficiency does not decrease.

(Example) Next, an example of the method and apparatus of the present invention will be described with reference to the drawings, taking as an example an operation for separating uranium isotopes in a uranium enrichment process.

FIG. 1 is a perspective view showing an embodiment of an isotope separation apparatus for carrying out the method of the present invention. Note that the same components and elements as those of the conventional example shown in FIGS. 6 and 7 are designated by the same reference numerals, and their explanations will be omitted.

FIG. 1 shows the overall configuration of an embodiment of the present invention. The isotope separation apparatus of this embodiment includes an evaporation crucible 2 containing a raw material 1 and an electron gun 3 that irradiates the raw material 1 with an electron beam 4. It has a steam generation device 13 consisting of. Further, a pulse power source 1 applies a predetermined potential to the positive electrode 7 and negative electrode 8 of the recovery electrode 6.
4 is attached.

As shown in FIG. 2, the wiring around this pulse power source 14 connects the positive electrode 7 of the recovery electrode 6 to a point at the same potential as the negative electrode 8 (grounded point in the figure) via a voltage adjustment resistor 15. , the vapor recovery plate 12 is configured to be movably brought into contact with any part of the voltage regulating resistor 15. Therefore, the steam recovery plate 1
Pulse positive voltage applied to 2 (vapor recovery plate voltage
Vq) is supplied from the pulse power supply 14 and is synchronized with the pulsed positive electrode voltage Vp. Further, the pulse positive voltage can be freely adjusted by the voltage adjusting resistor 15.

Next, a method of setting the positive electrode voltage Vp applied to the positive electrode 7 and the vapor recovery plate voltage Vq applied to the vapor recovery plate 12 in response to the pulsed laser beam will be explained with reference to FIG.

That is, generally pulsed laser beams L _o , L _o+1 ...
The output P _L of the dye laser serving as the oscillation source is generally oscillated as illustrated in FIG. 3A. That is, a dye laser with a frequency of about 5 KHz (period: 200 μsec) is generally used in consideration of operational efficiency. In addition, the pulse width of the pulsed laser beam 10
T ₁ is about 30 n·sec.

On the other hand, the positive electrode voltage Vp applied to the positive electrode 7 in response to the pulsed laser beams L _o , L _o+1 . . .
Applied with a pulsed positive voltage as illustrated in Figure B,
The rise of the pulsed positive voltage is at least ΔT from the rise of the pulse of the pulsed laser beam L _o , L _o+1 ...
is set later. That is, the delay time ΔT
By providing this, the time period for photoreaction and the time period for electric field recovery are completely separated. The delay time ΔT is generally set to 30 n·sec or more, which is the pulse width of the pulsed laser light.

Further, a pulsed positive voltage adjusted to be equal to or lower than the positive electrode voltage Vp is applied to the vapor recovery plate 12 in synchronization with the positive electrode voltage Vp. This pulsed positive voltage
As shown in the figure, it is branched and supplied from the anode of the pulse power supply 14 that applies the anode voltage Vp, and is applied as a vapor recovery plate voltage Vq that can be freely adjusted. Therefore, as shown in Figure 3C, the vapor recovery plate voltage Vq
is synchronized with the positive electrode voltage Vp.

Note that the pulse width T ₂ of the positive electrode voltage Vp and the pulse width T ₃ of the vapor recovery plate voltage Vq are both generated by a photoreaction and ionized isotope (U-235 ⁺ ) is attracted to the negative electrode 8. is set to be longer than the required time. This required time varies depending on the distance between the electrodes or the level of the applied positive electrode voltage Vp, but
It is approximately 1 to 2 μ·sec.

Next, the effect will be explained.

In the isotope separation method and apparatus of this embodiment, as shown in FIGS.
The raw material 1 heated and evaporated by 3 becomes a vapor stream 5 and is introduced into the photoreaction part 9 of the recovery electrode 6. A laser beam oscillation device 11 is applied to the introduced vapor flow 5.
A pulsed laser beam 10 oscillated from is irradiated,
A specific isotope (U-235) contained in the vapor stream 5 is selectively excited and further ionized to become an ionized isotope.

Next, as shown in FIG.
Since equal pulsed positive voltages are applied to the positive electrode 7 of the recovery electrode 6 and the vapor recovery plate 12 after the rise of An electric field as illustrated is created.

That is, equipotential lines 16 are formed approximately parallel to each other between the electrode plates as shown by solid lines, and lines of electric force 17 are formed perpendicular to the equipotential lines 16 as shown by broken lines. Electric lines of force 17 are formed so as to converge from vapor recovery plate 12 and positive electrode 7 to negative electrode 8 .

Ionized isotope 1 generated in photoreaction part 9
8 is attracted toward the negative electrode 8 of the recovery electrode 6 by the deflection force of the electric force lines 17.

On the other hand, the ionized isotope 18 that is trying to diffuse in the direction of the vapor recovery plate 12 is prevented from moving upward by the electric force lines 17 formed from the vapor recovery plate 12 in the direction of the cathode 8. It is efficiently sucked and collected in the direction.

Therefore, according to this embodiment, the steam recovery plate 1
Since a pulsed positive voltage equal to the positive electrode voltage Vp is also applied to 2 to form electric lines of force 17 converging from the vapor recovery plate 12 to the negative electrode 8, the ionized isotope 18 generated in the photoreaction part 9 is converted into vapor. The ionized isotope 18 is prevented from moving along with the stream 5 in the direction of the vapor recovery plate 12 , and the ionized isotope 18 is further attracted to the negative electrode 8 . Therefore, the ionized isotope 1 that becomes the product
8 from adhering to the vapor recovery plate 12 or escaping to the surrounding area, the separation and recovery efficiency of product isotopes is greatly improved.

Further, the vapor recovery plate voltage Vq applied to the vapor recovery plate 12 is set to a value equal to the positive electrode voltage Vp, and at least the pulse width T ₁ of the pulsed laser beam 10 is set to a value equal to the positive electrode voltage Vp.
Since the voltage is applied with a delay of 100 min, the time period for photoreaction and the time period for separation and collection of ionized isotopes by the electric field are completely separated.

Therefore, the excited level of the isotope atom is less likely to be split due to the electric force lines formed by the applied voltage, and the excitation rate is less likely to be reduced, preventing the smooth progress of the photoreaction. It does not become a factor that reduces separation and recovery efficiency.

The vapor recovery plate voltage Vq applied to the vapor recovery plate 12 may be configured to be adjustable by connecting it to the pulse power source 14 via a voltage adjustment resistor 15, for example, as shown in FIG.

FIG. 5 shows the state of the electric field in the photoreaction section 9 when the vapor recovery plate voltage Vq applied to the vapor recovery plate 12 is set lower than the positive electrode voltage Vp. Compared to the case of FIG. 4 in which the vapor recovery plate voltage Vq and the positive electrode voltage Vp are set equal, the density of the electric lines of force 17, etc. near the vapor recovery plate 12 can be reduced.

By configuring the vapor recovery plate voltage Vq to be adjustable in this way, the optimum potential distribution can be selected according to the operating conditions of the isotope separation apparatus, such as the density of the vapor flow, the operating temperature, and the degree of vacuum.

〔Effect of the invention〕

As explained above, according to the isotope separation method and apparatus according to the present invention, an electrode voltage for isotope separation and recovery is applied to the recovery electrode, and a voltage is also applied to the vapor recovery plate, so that the vapor recovery plate Since electric lines of force are formed that converge on the cathode, ionized isotopes that try to diffuse toward the vapor recovery plate are prevented from dissipating by the electric lines of force, and are further attracted and collected toward the cathode. Ru.

Therefore, the proportion of ionized isotopes that are targeted for recovery adhering to the vapor recovery plate is significantly reduced, and the vapor flow is prevented from escaping to the surrounding area, greatly improving product separation and recovery efficiency. do.

In addition, the voltage applied to the vapor recovery plate is set to a low value that is equal to or lower than the voltage applied to the positive electrode, so the photoreaction is not affected by the applied voltage. .

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an embodiment of an isotope separation apparatus for carrying out the method of the present invention, Fig. 2 is a cross-sectional view taken in the direction of - arrow in Fig. 1, and Fig. 3 A, B, and C are pulse A graph showing the temporal characteristics of the dye laser output, positive electrode voltage, and vapor recovery plate voltage corresponding to laser light. Figure 4 shows a part of the photoreactive part when the positive electrode and vapor recovery plate are set to the same voltage. Figure 5 is an enlarged cross-sectional view of the photoreaction section when the potential of the vapor recovery plate is set lower than the positive electrode potential, and Figure 6 is an example of the configuration of a conventional isotope separation device. The perspective view and FIG. 7 are cross-sectional views taken along the - arrow in FIG. 6. DESCRIPTION OF SYMBOLS 1... Raw material, 2... Evaporation crucible, 3... Electron gun, 4... Electron beam, 5... Vapor flow, 6... Recovery electrode, 7... Positive electrode, 8... Negative electrode, 9... ... Photoreaction section, 10 ... Pulse laser beam, 11 ... Laser beam oscillation device, 12 ... Steam recovery plate, 13 ... Steam generation device, 14 ... Pulse power supply, 15 ... Voltage adjustment resistor, 16 ... ... Equipotential lines, 17 ... Lines of electric force, 18 ... Ionized isotope, P _L ... Dye laser output, Vp ... Positive electrode voltage, Vq ... Vapor recovery plate voltage, T ₁ ... Pulsed laser light Pulse width of T ₂
...Pulse width of positive electrode voltage, T ₃ ...Pulse width of vapor recovery plate voltage, ΔT ... Delay time.

Claims (1)

[Claims] 1 A vapor flow is generated by heating and evaporating a raw material containing multiple types of isotopes, and this vapor flow is introduced into a recovery electrode formed by alternately arranging a positive electrode and a negative electrode. After that, the vapor flow is irradiated with a pulsed laser beam that selectively ionizes a specific isotope to generate ionized isotopes, and a voltage from a pulsed power source is applied between the electrodes to form an electric field. The ionized isotope is deflected toward the recovery electrode to separate and recover a specific isotope, and a voltage lower than the positive electrode voltage is applied to the vapor recovery plate that collects the vapor flow that flows through the recovery electrode without being separated and recovered. By applying this, electric lines of force are formed that converge from the vapor recovery plate and the positive electrode to the negative electrode, and the movement of ionized isotopes that diffuse toward the vapor recovery plate due to the deflection force of the electric lines of force is prevented. An isotope separation method characterized in that the ionized isotope is focused in the direction of a cathode of a recovery electrode. 2 The voltage applied to the positive electrode voltage and the vapor recovery plate is applied as a pulsed positive voltage synchronized with each pulsed laser beam, and the rise of the pulsed positive voltage is at least as long as the pulse width of the pulsed laser beam from the rise of the pulsed laser beam. 2. The isotope separation method according to claim 1, wherein the isotope separation method is set with a delay of . 3. A steam generation device that heats and evaporates raw materials containing multiple types of isotopes to generate a vapor flow, and selectively ionizes specific isotopes contained in the vapor flow by irradiating the vapor flow with pulsed laser light. a recovery electrode formed by alternately arranging positive electrodes and negative electrodes parallel to the flow direction of the vapor flow;
A pulse power source that applies a predetermined voltage between electrodes in order to separate and recover ionized isotopes by deflecting them using an electric field, and a vapor recovery plate that recovers a vapor flow that has passed through the recovery electrode, the pulse power source having at least An isotope separation device characterized in that a pulsed positive electrode voltage is applied to the positive electrode with a delay of the pulse width of the pulsed laser beam, and a pulsed positive voltage lower than the pulsed positive electrode voltage is applied to the vapor recovery plate. Device. 4. The isotope separation device according to claim 3, wherein the pulsed positive voltage applied to the vapor recovery plate is adjustable.