JPS63134038A - Device for concentrating uranium - Google Patents

Abstract

PURPOSE:To arbitrarily adjust the concn. of recovered uranium by varying the part of the flying direction of atomic beams at the specified angle from the position of the longitudinal direction of plural cathodes recovering ionized U-235 and making the residual cathode part to a fixed type. CONSTITUTION:Ionization laser for ionizing excited U-235, namely a second laser beam 10 is projected. U-235 atoms 8 incorporated in atomic beams 6 are ionized with a first and second laser beams 9, 10 and changed into U-235<+> atoms 11. When an electric field is formed in the atomic beams 6 contg. these ions by using a grounded electrode 12 and a cathode 13, only ionized U-235<+> atoms are electrostatically attracted to the cathode 13 and finally adsorbed on the surface of the cathode 13. On the other hand, nonionized U-235 atoms 7 are straightly advanced without receiving the effect of this electric field and absorbed on a collection plate 14 of neutral atoms.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a uranium a-condensation apparatus for separating and concentrating uranium isotopes by a laser method.

(Prior Art) Conventionally, the gas diffusion method using uranium hexafluoride gas, the nozzle method, and the centrifugal separation method are known as uranium isotope separation and enrichment technologies, and these have already entered the stage of practical use. especially,
The centrifugation method also has a larger separation coefficient than the other two methods.
It is said that the number of stages of the cascade may be several tens.

Among these three methods, in order to produce various degrees of 'a' required by the nuclear reactor, it is possible to consider a method of blending a once concentrated intermediate product or a method of extracting gas from the middle of the cascade.

On the other hand, methods using uranium metal and uranium hexafluoride gas are known as methods for separating and enriching uranium isotopes using a laser. The principle of the method using metallic uranium is to convert metallic uranium, which is a mixture of U-235 and U-238, into an atomic gas state, and to generate highly monochromatic e and o
U- exposed by the first visible light laser near the oo person
235 atoms are selectively placed in the first excited order, and the second,
The third 6,000 people were irradiated with a visible light laser,
It selectively moves only excited atoms to an ionization level or higher. The principle of the method using uranium hexafluoride gas is that uranium hexafluoride gas consisting of a mixture of U-235F6 and tJ-238F6 is passed through a nozzle at supersonic speed, and a supercooled UF6 beam is generated by adiabatic expansion. First, an infrared laser (generally 16 μm) is irradiated to selectively excite only U-235Fg, and then an ultraviolet laser or an infrared laser is irradiated to excite U-235F.
6 is difficult to solve.

(Problem to be solved by the invention) When trying to produce products with various enrichment levels using a uranium isotope separation and enrichment device using this laser, conventional gas diffusion methods, nozzle methods, and centrifugal separation methods are required. Let's examine the validity of the three methods used.

First, in the method of blending the first intermediate product, in the separation method using metallic uranium, the intermediate product is vapor-deposited on a recovery electrode and recovered as liquefied uranium, so the natural metallic uranium for blending is also heated to a high temperature. However, the process of liquefying uranium metal at high temperatures and handling it requires materials with high heat resistance and corrosion resistance, which is expensive in terms of equipment. In addition, in the separation method using uranium hexafluoride gas, the dissociated U-235F
Since 6 is recovered as UF6 gas through a UF5 fluorination device, blending similar to the conventional method is possible, but the blending itself increases the cost of the entire plant.

Next, this method is impossible because the laser method itself has the ability to perform separation in one stage, making the cascade itself unnecessary.

The present invention has been made in view of the above circumstances, and is an apparatus for separating and enriching uranium isotopes using a laser method. The purpose is to provide a concentrator.

[Structure of the Invention] (Means for Solving the Problems) That is, the present invention evaporates metallic uranium to generate an atomic beam and injects U into the atomic beam which is in an atomic gas state.
- Irradiate the first laser for selective excitation of 235, then ionize the excited U-235, irradiate the second laser to recover the ionized U-235, and collect the ionized U-235 at any point in the longitudinal direction of the plurality of recovery electrodes. This is a uranium enrichment device characterized in that the part of the direction in which the atomic beam flies from the position can be changed by the angle θ, and the remaining part of the recovery electrode is configured as a fixed type that does not change the angle.

(Function) With the above configuration, the neutral atomic weight of non-ionized uranium adhering to the recovery electrode can be varied by changing the angle θ, so the enrichment degree of uranium recovered to the product recovery electrode can be varied. Can be produced arbitrarily.

(Embodiment) An embodiment of the apparatus according to the present invention will be described below with reference to FIG.

FIG. 1 is a diagram of an apparatus for schematically explaining the apparatus according to the present invention.

That is, in FIG. 1, an electron beam 2 is irradiated from a filament 1 via a deflecting magnetic field 3 onto a metal uranium 5 placed on a crucible 4. The metallic uranium 5 bombarded by the electron beam 2 is heated to 2,000″~3
The atomic beam 6 is heated to ,000″K and travels upward as a metallic uranium atomic beam 6, in which U-238 atoms 7 and U-235 atoms 8 are mixed. U-23 in this atomic beam 6
A selective excitation laser, that is, a first laser beam 9 having a frequency corresponding to the absorption line of No. 5 is irradiated. A second laser beam 10 is irradiated with an ionizing laser beam for ionizing U-235, which is not excited to the zeroth order, in which only tJ-235 to be concentrated is excited by the first laser beam 9.

The tT-235 atoms 8 in the atomic beam 6 are ionized by the first and second laser beams 9 and 10 and changed into U-235+ atoms 11. Now, the atomic beam 6 containing this ion
When an electric field is created using the ground electrode 12 and the cathode 13, only the ionized U-235+ atoms 11 are electrostatically attracted to the cathode 13, and finally the removal electrode 13? :,
It is adsorbed to the surface. On the other hand, the U-238 atoms 7 that have not been ionized travel straight without being affected by this electric field and are collected by the neutral atom collection plate 14.

Next, the separation performance of the apparatus according to the above configuration will be explained using the three-step method as an example and the energy levels of the uranium atom and the transitions between the levels shown in FIG. 2. The symbols and symbols in FIG. 2 are as follows.

- is the transition between each unit → is the energy exchange between U-235 and U-238.

■ Transition due to absorption of selective excitation laser.

■, ■′ are deviations due to absorption of intermediate excitation laser light.

■,■′ are f, deviations due to absorption of separated laser light.

■, ■′ are deviations due to stimulated emission and spontaneous emission caused by selective excitation laser light.

■, ■′ are deviations due to stimulated emission and spontaneous emission by intermediate excitation laser light.

■, ■' are selectively excited level U-235 and base unit U-
238 deviation due to energy exchange.

■, ■' are the intermediate excited level U-235 and the ground level U-
238 transition due to energy exchange.

■, ■′ are U-235 at ionization level and U-2 at ground level
This is a transition due to 38 energy exchanges.

The ionization characteristics of uranium at the laser irradiation area can be determined by solving the rate equation below.

(dN+ /dt)= (Nl N2)W++N
2 (1/τz + 1/z” C2)+N1 (t
/τ3+1/τC3) +N4(1/τ4+1/τC4) (dN2/dt) =-(N2-Nz) W2+(
Nl N2) W+ -N2 (1/τ2+1/τc2) (d N 1 / d j ) = -N 3 W 3
+ (N2-N3) 't'12 N3 (1/τ3+1/τC3) (dN+ /dt)= N5WI N4 (1/τ4+1/τC4) (dN+ '/dt) = (N2'/τ2)+
(Ngo'/τ3) + (N4'/τ4) - (N2/τC2) - (N2/τC2) - (N4/τC4) (dN2'/dt) = (N2' - Nl
)W2- (N2'/τ2) +(N2/τC2) (dN3'/dt)=-N3' Wt+ (N2
'-N,)W2-(Nx'/τ3) +(N3/τCx) (dN4'/dt)=-N3'W3-(N
4/τ4) +(N4/τC4) However, Nl, N2, N3, N4: U-235 atomic density (pieces/c) at the ground level, selectively excited level, intermediate excited level, and ionization level.

N+', N2', Nl', N4': U-235 atomic density (pieces/d) at the ground level, selectively excited level, intermediate excited level, and ionization level.

W1=〈δ113/hυ3) W2=(δ113/hυ3) W3=(δ113/hυ3) However, w, , w2, wgo: Excitation rate (sec-1) by each laser for selective excitation, intermediate excitation, and ionization.

τC2, τC1, τC4: lifetime (sec) of each level of selective excitation, intermediate excitation, and ionization.

τ2, τ3, τ4: Reciprocals (sec) of the energy exchange frequency between the U-235 atom at each level of selective excitation, intermediate excitation, and ionization and the U-238 atom at the ground level.

δ1, δ2, σ3: Laser light absorption cross section (cd) for selective excitation, intermediate excitation, and ionization.

IT, I2, I3: 5! ! Power density (W/alI) of each laser for selective excitation, intermediate excitation, and ionization.

δ1, δ2, υ3:! ! Selective excitation, intermediate excitation, and ionization laser light frequencies ()tz).

h blank constant (jouie-sec).

Here, if the value of Nx at time t is expressed as Nx(t), then N2 (0) = N3 (0) = N4 (0)
=N2' (0) =N3' (0)-N4
' (0) =O N+ (0)/ [Nl (0)+N+'
(0)] = XF Nl (0) +N+ ' (0) =
Pe/(R-Te).(1-Ku).

However, Ku: the ratio (-) of atoms in a metastable level near the ground level, which is a function of the temperature Te.

Pe: Uranium vapor pressure (Torr) T at the laser irradiation part
e: uranium vapor temperature (°K) at the laser irradiation part, R: gas constant (d, Torr/nol; 'K).

If the laser beam pulse width is TW, then W 1 (t >T't4 ) = W2 (t > TW
)=W3 (t>TW)=0, and if Ta is the average time until the electric atoms attach to the electrode, then the uranium iGp attached to the electrode can be expressed by the following formula.

Qp= (Nl (Ta)+N4' (Ta)l
a″V+Kp GF However, Gp: Product uranium adhesion amount (ton/5ec) GF
: JjXfl Uranium generation amount (ton/5ec) a: Bottom area of laser irradiation part (-)
a) Kp: Rate (-) of non-electrified atoms adhering to the product collection electrode
It is determined by the electrode shape, arrangement, etc.

Therefore, the product concentration xp is X+1=N4 (Ta)-a・v+KO-XF-GF
/Gp However, XF: raw material uranium concentration, and waste product concentration XT is given by the following formula.

XT = (GF - XF - Gp - Xp) / (
GF-GP) The present invention provides a negative electrode 13 in which non-ionized atoms are a product recovery electrode.
By adjusting the facing angle of the ground electrode 12 and the negative electrode 13, the product concentration xp can be changed to produce a wide variety of concentrations.

That is, as shown in an enlarged view of only the main part in FIG.
1 of the cathode 13 so that the positional relationship is parallel to
If the angle θ of the 3b part is θ=O, then the non-ionized U
-2387 travels straight without being adsorbed to the surface of the cathode 13, and theoretically Kp becomes 0, and the product concentration becomes 100%. On the other hand, when the part 13b of the cathode 13 is tilted at an angle θ1〉0 with respect to the atomic beam, the unionized U −23
8 atoms 7 are also adsorbed on the surface of the cathode 13b, and k! 1>O, and the product concentration is theoretically 100% or less. Also, the angle θ2<
When tilted at O, the amount of uranium atomic beam passing between the cathode and the ground electrode is reduced, so the amount of U recovered by the cathode is reduced.
Since the amounts of -235+ and U-238 atoms 7 are also reduced, the amount of separation work can also be changed. Therefore, 13b of the cathode 13
By arbitrarily changing the inclination angle θ of the portion, it is possible to adjust the product concentration to a desired concentration using the formula for determining the product concentration, and it is possible to produce a wide variety of concentrations.

[Effects of the Invention] According to the present invention, in the uranium isotope enrichment device using a laser, U-2
By making the angle of the longitudinal part of the plurality of collection electrodes for collecting 35 products in the direction in which the atomic beams fly, variable, it is possible to produce a wide variety of product concentrations.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a uranium enrichment device using a laser method according to the present invention, and FIG. 2 is a diagram illustrating each level of U-235 and U-238 in the device shown in FIG. The schematic diagram, FIG. 3, is a schematic sectional view showing an enlarged main part of the device in FIG. 1. 5・・・・・・・・・・・・Uranium metal 6・・・・・・
・・・・・・Atomic beam 7・・・・・・・・・・・・U
−235 atoms 8・・・・・・・・・U −23
8 atoms 9......Selective excitation laser beam 1
0...Ionizing laser beam 11...
・・・・・・・・・tJ −235+12・・・・・・・
・・・・・・Ground T, poles 13, 13a, 13b ・・・・・・・・・Cathode electrode Applicant Toshiba Corporation Representative Patent attorney Satoshi Suyama - Figure 3

Claims (1)

[Claims] (1) Metallic uranium is evaporated to generate an atomic beam, and the atomic beam, which is in an atomic gas state, is irradiated with a first laser beam for selective excitation of U-235, and then the excited U-2
In a uranium enrichment device using a laser method that condenses uranium by irradiating a second laser beam that ionizes U-235, an atomic beam is emitted from any position in the longitudinal direction of a plurality of cathodes that collect the ionized U-235. A uranium enrichment device characterized in that a portion of the incoming direction can be changed by an angle θ, and the remaining cathode portion is configured as a fixed type that does not change the angle.