JPS6197022A - Uranium enriching device by laser method - Google Patents

Abstract

PURPOSE:To obtain many kinds of uranium at various degrees of enrichment by maintaining plural recovery electrodes so that the opposing angle theta of the electrode to the straight flow of an atomic beam may be changed in the range 0 deg.<theta<90 deg.C. CONSTITUTION:The ratio of nonionized atoms to be deposited on a product recovery electrode is changed to alter the concn. of the product by regulating the opposing angle theta between a grounding electrode 12 and a cathode 13 and the straight flow of an atomic beam in the range 0 deg.<theta<90 deg.C, and many kinds of uranium at various enrichment are produced. Consequently, in an atomic method using metallic uranium, many kinds of products at various concncs. can be produced only by changing the opposing angle of plural recovery electrodes for recovering a <235>U produced without adding any special equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a technology for separating and enriching uranium isotopes using a laser method.

[Technical background of the invention and its problems 1 Conventionally, the gas diffusion method using uranium hexafluoride gas, the nozzle method, and the centrifugation method are known as uranium isotope separation and enrichment technologies, and these have already entered the stage of practical use. ing. 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 about several tens.

Among these three methods, in order to produce the various enrichments required by the nuclear reactor, conceivable methods include blending the once concentrated intermediate product and 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 reducing uranium isotopes using a laser. The principle of the method using metallic uranium is that metallic uranium, which is a mixture of 211U and 236U, is converted into an atomic gas state, and 6,000%, which is highly monochromatic, is
23S after being exposed to the first visible light laser near 0
Selectively make the U atom the first excited unit, and then irradiate the second and third visible light lasers of around 6,000 to selectively transfer only the excited atoms to more than the ionized unit. It is something.

The principle of the method using uranium hexafluoride gas is '! 5UF
6 and UFs" is passed through a nozzle at supersonic speed to generate a supercooled UFs beam by adiabatic expansion, and the beam is first injected with an infrared laser (
In general, 16 μIn) is irradiated to selectively excite only 23S U F6, and furthermore, ultraviolet laser or infrared laser is irradiated to dissociate ns (J l:6).

When trying to produce products with various enrichment levels using this laser-based uranium isotope separation and enrichment device, the validity of the three conventional methods: gas diffusion method, nozzle method, and centrifugation method. Let's consider.

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, 2! S jl l
: Since 6 is recovered as UF6 gas through a UFs 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.

[Object of the Invention] The present invention has been made in view of the above circumstances, and provides a uranium isotope separation and enrichment apparatus using a laser method that can produce various enrichment levels compared to the atomic method using metallic uranium. The purpose is to provide a uranium enrichment device using a laser method.

[Summary of the Invention] That is, the present invention evaporates a metal Vran to generate an atomic beam, and the atomic beam, which is in an atomic gas state, is given two
The opposing angle θ of the plurality of recovery electrodes that irradiate the first laser for selective excitation of 35U, and then recover the ionized 235U product by irradiation with the second laser that ionizes the selectively excited 215U is determined by the atomic angle θ. Q"< θ at - with respect to the straight direction of the beam
This is a uranium enrichment device using a laser method, which is characterized in that it can be held at an angle of 90 degrees.

[Embodiment of the Invention] 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
,000' K, becomes a metallic uranium atomic beam 6, and travels upward. In this atomic beam 6, 238U atoms 7 and 2''U atoms 8 are mixed.

2 out of 6 atomic beams! A selective excitation laser, that is, a first laser 9 having a frequency corresponding to the absorption line of sU is irradiated.

Only the 23 sU to be concentrated is excited by the beam of the first laser 9. Next, an ionizing laser, that is, a second laser 10, is irradiated to ionize the excited nsU. The first and second laser beams 9 and 10 ionize 75U8 in the atomic beam 6, t3su+1
Changes to 1. Now, when an electric field is created in the atomic beam 6 containing this ion using the ground electrode 12 and the negative electrode 13,
Only the ionized "U+11" is electrostatically attracted to the negative electrode 13 and finally adsorbed to the surface of the negative electrode 13.

On the other hand, unionized sU7 travels straight without being affected by this electric field and is collected by the neutral atom collection plate 14.

Next, the separation performance of the apparatus according to the above configuration will be explained using a three-step method as an example, using one unit of energy of a uranium atom and the transition between each level in FIG. 2. The symbols and symbols in FIG. 2 are as follows.

← is the transition between each unit.

Yang is the energy exchange between 2”U and 231U.

■ Transition due to absorption of selective excitation laser.

■, ■′ are transitions due to absorption of intermediate pumping laser.

■, ■′ are transitions due to absorption of ionizing laser.

■,■′ are transitions caused by stimulated emission and spontaneous emission by selective excitation laser.

■,■′ are transitions caused by stimulated emission and spontaneous emission by intermediate pumping laser.

■, ■' are the selective excitation unit 23S U and the base unit 2''
Transition due to energy exchange of U.

■,■' are intermediate excitation units 2! S U and base unit 2W
Transition due to energy exchange of U.

■, ■' are ionization units of 2! S U and base unit 738
This is a transition due to energy exchange of U.

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

(dN+/dt) = −(Nl −N2)W++
N2 (1/τ2+1/τ(2) +N3 (1/r3+ 1/Z:e3) ten N4 (1/
τ4+1/τc4) (d N2 /dt) = −(N2-N3)N2+
(Nl-N2)W+ -N2 (1/rz + 1/rc2)(d N 3
/dt) --N a N3+(N2 N5)N
2 - N3 (1/τ3 + 1/τσ3) (d N 4
/dt) =-N 3 N3N < (1/
r 4 + 1/'l:c< )(d Nl
−/dt)=(N2 −/τ2 )+(N3−/τ
3) + (Nl-/τ4) = (N2/τ2) (N3/τc3) (N4/τe<) (d N2-/dt) = -(N2--N3-)N
2− (Nz −/τ2 ) +(N2/τc2 ) (d N3−/dt)−−N3 −Ws+ (N2
--N3-)N2-(N3-/τ3) +(N3/τex) (dNl-/dt)=-N3-N3(Nl-
/τ4) +(N4/τ(4) where Nl, N2.N3, Nl: 2% U atom density (pieces/c/) at ground level, selective excitation unit, intermediate excitation unit, and ionization unit.

N1', N2', N3°', N4': 238U atomic density (pieces/cil') at ground level, selective excitation unit, intermediate excitation unit ionization unit.

N1=(δ+I+/hυ1) N2=(δ212/hυ2) N3−(δz13/hυ3) However, W+, N2, N3: Excitation rate (sec −') by each laser for selective excitation, intermediate excitation, and ionization.

τ(2, τC3, τC4: lifetime of each unit of selective excitation, intermediate excitation, and ionization <sec>).

τ2, τ3, τ4: Reciprocal of energy exchange frequency (sec) between 2J5 U atoms in each unit of selective excitation, intermediate excitation, and ionization and 2NU atoms in the base unit.

σ1, σ2, σ3: Laser light absorption cross sections (Cze) for selective excitation, intermediate excitation, and ionization.

II, +2.13: Power density (W/d) of each laser for selective excitation, intermediate excitation, and ionization.

ν1, ν2, C3: Laser light frequencies (Hz) for selective excitation, intermediate excitation, and ionization.

h blank constant (joule-sec).

Here, if the value of NX at time t is expressed as NX(t), then N2 (0) = N3 (0) = N4 (0) = N
z'(0)=Ns'(0)=N4' (0)
=O Nl (0)/ [Nl (0) +N+' (
0)]=XF Nl (0)+Nt' (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 at the laser irradiation part (°K), R: gas constant (cIillTorr/mol; 'K
) T: Al.

If the laser beam pulse width is TV, then W+ (t > 7-w) = W2 (t > T
V ) = Wa (t > TW ) = 0, and the average time it takes for ionized atoms to attach to the electrode is Ta
Then, the uranium ff1Gp attached to the electrode can be expressed by the following formula.

Gl) = (N4 (Ta) + N4' (Ta
) ) a −V+Kl) Gp However, Gp: With product uranium @ffi (ton /se
c) GF: Raw material uranium generation amount (ton/sea)
a: Bottom area of the laser irradiation part (Cze) ■: Uranium vapor velocity in the laser irradiation part (cm/se
c) Kp: Rate of non-ionized atoms adhering to the product recovery electrode (-)
It is determined by the electrode shape, arrangement, etc.

Therefore, the product concentration Xp is Xp=N4 (Ta)・a−v+Kp−xF−GE/G
p However, xF: Raw material uranium angle In addition, the waste product concentration XT is given by the following formula.

XT = (GF-XF-Gll-Xp)/(
Gp-GO) The present invention provides a cathode 13 in which non-ionized atoms are a product recovery electrode.
By adjusting the opposing angle of the ground electrode 12 and the cathode 13, the product concentration Xp can be changed by changing the ratio Kp of adhesion to the ground electrode 12 and the negative electrode 13, thereby producing various concentrations.

That is, as shown in FIG. 3, if the ground electrode 12 and the cathode 13, which is a collection electrode, are in a positional relationship parallel to the atomic beam, the atomic beam is not ionized."U7 is the cathode 1.
Theoretically, Kl)
= 0, and the product concentration is also 100%, but the negative electrode 13
When the cathode 13 is tilted at an angle θ with respect to the atomic beam, the unionized “U7” is also adsorbed to the surface of the cathode 13, so that Kl)>Q, and the product concentration is theoretically less than 100%. Therefore, the inclination angle θ of the cathode 13 can be adjusted to a desired concentration using the formula for determining the product concentration shown in (Equation 1) within the range of 0° <θ to 90°, and many types of concentrations can be produced. Therefore, in the above embodiment, it is possible to produce a wide variety of product concentrations by simply adjusting the facing angle of the 23s (J product recovery electrodes).

[Effects of the Invention] According to the present invention, 235
By simply changing the opposing angles of the plurality of recovery electrodes for U product recovery, it is possible to produce a wide variety of product concentrations without adding any special equipment.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of a uranium enrichment device using a laser method according to the present invention, FIG. 2 is a schematic diagram for explaining each level of 2355 U and 236 U in the device of FIG. 1, FIG. 3 is a schematic cross-sectional view showing an enlarged main part of the device in FIG. 1.

Claims (1)

[Claims] (1) Evaporate metallic uranium to generate an atomic beam, and inject U^2^3^5 into the atomic beam, which is in an atomic gas state.
U^ which was irradiated with the first laser for selective excitation and then excited
In a uranium enrichment device using a laser method that condenses uranium by irradiating a second laser that ionizes 2^3^5, the opposing angle θ of multiple collection electrodes that collect ionized ^2^3^5U is expressed as atomic 0°<θ<90 with respect to the straight direction of the beam
A device for concentrating uranium using a laser method, characterized in that uranium can be converted into °.