JPS62140630A - Enrichment apparatus for uranium - Google Patents

Abstract

PURPOSE:To produce enriched uranium having many kinds of degrees of enrichment in an atomic method without using a large-scale installation by holding freely movably one part of a recovery electrode recovering ionized <235>U in the direction far off from an atomic beams, stream. CONSTITUTION:The proportion of ionized atom stuck on a cathodic electrode 13 being a recovery electrode for a product (enriched uranium) is changed in such a way that the passage of time of an atomic beam stream passing through the recovery electrode is made variable by making one part of a ground electrode 12 variable in the direction rectangular to the atomic beam and ultimately by making the length of the recovery electrode variable, and a product (enriched uranium) having many kinds of degrees of enrichment is produced by changing the degree of enrichment of the product. As a result, enriched uranium having many kinds of degrees of enrichment can be produced in an atomic method without using a large-scale installation such as a blending apparatus.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a uranium enrichment device using a laser method.

[Technical background of the invention and its problems] Conventionally, gas diffusion methods using uranium hexafluoride gas, nozzle methods, and centrifugal separation methods have been known as techniques for separating and enriching uranium isotopes, and these methods have already been used. It has entered the practical application stage. In particular, the centrifugal separation method has a larger separation coefficient than the other two methods, and it is said that only a few tens of cascade stages are sufficient.

In order to produce products with the various enrichments required by nuclear reactors using these three methods, there is a method of blending the once enriched intermediate product, or a method of handling appropriately enriched uranium gas from the middle of the cascade. I can think of a way to get it out.

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 235U and 236U, into an atomic gas state, and to produce 6,000% of highly monochromatic uranium.
The 235U atoms are selectively exposed to the first excited level by the first visible light laser near the person, and the second and third 6 atoms are exposed to the first excited level.
．． This method irradiates a visible light laser with an intensity of around 1,000 yen to selectively move only the excited atoms to an ionization level or higher. What is the principle of the method using uranium hexafluoride gas?
55UF6 and? Uranium hexafluoride gas consisting of a mixture of 36UF6 is passed through a nozzle at supersonic speed, and a supercooled UFs beam is generated by adiabatic expansion.The beam is first illuminated with an infrared laser (generally 16μm) and 2!5UFs
235Ul:6 is selectively excited and further irradiated with ultraviolet laser or infrared laser beam to dissociate 235Ul:6.

When attempting to produce products with various enrichment levels using a uranium enrichment device using this RaE, we will examine the validity of the three conventional methods: gas diffusion method, nozzle method, and centrifugation method. I'll try it.

First, in the first method of blending intermediate products, when a separation method is performed using metallic uranium, the intermediate product is vapor-deposited on a recovery electrode and recovered as liquefied uranium, so natural metallic uranium for blending is also heated to high temperatures. It will be heated to liquefy and blend. Therefore, a process in which metallic uranium is liquefied and handled at high temperatures requires materials with high heat resistance and corrosion resistance, which results in expensive equipment. In the second separation method using uranium hexafluoride, the dissociated 235UF6 is recovered as UF6 gas through a UFs fluorination device. Therefore, although blending similar to the conventional method is possible, blending itself increases the cost of the entire plant.

In the method of starting from the middle stage of the third cascade, the laser method itself has the ability to separate in one stage, so the cascade itself becomes unnecessary. Therefore, this method is impossible.

[Object of the Invention] The present invention has been made in view of the above circumstances, and is capable of producing enriched uranium ( The purpose is to provide a uranium enrichment device using a laser method that can produce uranium products (products).

[Summary of the invention] That is, the present invention vaporizes metallic uranium to generate an atomic beam, and the atomic beam, which is in an atomic gas state, is exposed to 2
A fulcrum is set on a part of the ground electrode of the recovery electrode that irradiates the first laser for selective excitation of 35U and then irradiates the second laser that ionizes the selectively excited 235U to recover the ionized 235U product. is a uranium enrichment device using a laser method, which is characterized by a ground electrode that is movably held so as to move away from the atomic beam flow in a direction perpendicular to the atomic beam flow.

According to the present invention, the enrichment degree of recovered uranium can be changed by varying the length of the recovery electrode, and a blending device or the like is not required.

[Embodiment of the Invention] An embodiment of the apparatus according to the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 schematically shows an apparatus according to the present invention systemically, and FIG. 3 is an enlarged view of the main part of FIG. 1.

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' K~
It is heated to 3,000' K, becomes a metallic uranium atomic beam 6, and travels upward. In this atomic beam 6, 256 U atoms 7 and 235 U atoms 8 are mixed. 235U in this atomic beam 6
The number of selective excitation lasers corresponding to the absorption lines of
irradiate with the laser 9. Only the 235U 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 235U. The first and second laser beams 9 and 10 cause 235U in the atomic beam 6 to be
8 is ionized and changes to 235U"11. Now, the atomic beam 6 containing this ion is connected to the ground electrode 12 and the negative electrode 1.
3 to create an electric field, the ionized "5tJ"
Only 11 is electrostatically attracted to the negative electrode 13 and finally attracted to the surface of the negative electrode 13.

On the other hand, the unionized 23''U7 moves straight without being affected by this electric field and is collected by the neutral atom collection plate 14. In the figure, the reference numeral 15 indicates a fulcrum; The vicinity of the part is shown enlarged in Fig. 3. This fulcrum 15
is provided to adjust the length of the ground electrode 12,
By opening the angle θ around the fulcrum 15, the length of the ground electrode 12 changes. This angle θ can be arbitrarily selected.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.

teeth? Energy exchange between 3S U and 236U.

■ 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 selectively excited levels? 55U and the base unit 236
Transition due to energy exchange of U.

■, ■' are the intermediate excited level 235U and the ground level 256
Transition due to energy exchange of U.

■ and ■' are transitions caused by energy exchange between 2% U of the ionization level and 2% U of the ground level.

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

, (dN 1/dt)=-(N + -N 2 ) W
+10N2 (1/7:2 +1/rc2)+f'
h (1/ r 3 +i, "rc 3 ) + N4 (
1/ τ, s + 1/rc 4) (dN2/dt) =
(N2 N3) W2+(N I - N2) W
l −N2 (1/τ2+1/τc 2 )(dN 3
/dt)=-N3W3+(N2-N3)W
2 N 3 (1/r 3 +1/τC3) (dN 4
/dj)=N3W3N4(1/τ4+17τC
4) (dN + ' / dt) = (Nz ' / τ2) + (
N3'/τ3) + (N, 4'/τ4) - (N2/τC2) (N3/τC3) (N4/τC4) (dN2'/di) = -(N2' - N3') W2
-(N2'/τC2) +(N2/τ2) (dN3'/dt)=-N3'W30(N
2' - N3' ) Wz (N3'/τC3) + (N3/τ3) (dt'L'/dt) = N3' W3 (N4'/
τC4) + (N4/τ4) However, N+, N2, N3, N4: 21''U atom density (pieces/C) at the ground level, selectively excited level, intermediate excited level, and ionization level.

N+', N2', N3', N4': 23 at ground level, selectively excited level, intermediate excited level, ionization level
6U atomic density (pieces/cm').

W1=(σ+I+/hυ1) Wl2(σ2■2/hυ2) W3=(σ3I3/hυ3) However, W+, W, +, W3: Excitation speed by each laser for selective excitation, intermediate excitation, and ionization (sec −') .

rc2, rc3, τc4: lifetime (sec) of each unit of selective excitation, intermediate excitation, and ionization.

τ2, τ3, τ4: Reciprocals (sec) of the energy exchange frequency between the 235U atom at each level of selective excitation, intermediate excitation, and ionization and the 236U atom at the ground level.

σ1, σ2, σ3: Laser light absorption cross section for selective excitation, intermediate excitation, and ionization (C) 11, h, I3: Power density of each laser for selective excitation, intermediate excitation, and ionization (W/c) υ1 , υ2, υ3: selective excitation, intermediate excitation, and ionization laser light frequencies (Hz).

h blank constant (joule -5ec>.

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

However, Ku:W is the ratio (-) of atoms in a metastable level near the bottom bell, and is a function of temperature Te.

Pe: the above pressure of uranium at the laser irradiation part (Torr),
Te: Above temperature of uranium at laser irradiation part (°K), R
: Gas constant (c&, 1orr/mol:'K).

If the laser beam pulse width is TW, then Wl (t > TW ) = W2 (i > TW) = W
3 (↑>TV)=0, and if Ta is the average time until the ionized atoms adhere to the electrode, then the uranium NGp that adheres to the electrode can be expressed by the following formula.

Gp = (N4 (Ta >10N4' (T
a ) ) a - v 10Kl) GF However, Gp: '1 product uranium deposition amount (toll/5eC)
GF: Raw material uranium generation 5i (tan/5eC)a:
Laser irradiation area bottom area (Ci) V: Laser irradiation area (Uranium vapor velocity (cm/s)
ec) 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=Na (Ta)-a *v+KI) 'XF
”GF/Gp However, XF: raw material uranium concentration, and waste product concentration XT is given by the following formula.

XT = (GT - XT - Gp - Xt)) / (GF
-Gl)) As described above, the present invention determines the proportion of ionized atoms adhering to the cathode 13, which is the product recovery electrode, by determining the passage time of the atomic beam flow passing through the recovery electrode by converting a part of the grounded electrode 12 into an atomic beam. The idea is to make it variable in the right angle direction, that is, by making the length of the collection electrode variable, and to change the product concentration Xp to produce many types of concentration.

That is, the ionized atoms adhering to the negative electrode 13 are expressed by the above formula (%)) In other words, 235U"11 ionized by the laser is
decreases with time, while ``U7 is ionized'' 5
Exchanges energy with U11. Therefore, the proportion of ionized atoms 235 U723a U necessarily increases with the passage of time. Therefore, as the length of the recovery electrode increases, the concentration of the attached uranium product decreases, and conversely, as the length of the recovery electrode decreases, the temperature of the product increases.

In the present invention, as shown in an enlarged view in FIG. 3, a fulcrum is provided in at least one of the recovery electrodes, that is, the ground electrode 12, and is movably held in a direction away from the atomic beam flow, so that when the fulcrum is moved by an angle θ, , the length L of the recovery N pole is t when the angle θ is O.

If the length of the movable part is Ll, then L-(Lo-L+ >+L+ cos θ, and the dispersion of the electrode can be continuously varied.

As a result, the traveling time of the atomic beam adhering to the electrode can also be varied, and the enrichment degree of uranium adhering to the recovery electrode can be changed as described above.

[Effects of the Invention] According to the present invention, in a uranium isotope enrichment device using a laser, special settings can be made by simply changing the opposing angles of a plurality of recovery electrodes for recovering 235U products using an atomic method using metallic uranium. This has the effect of producing a wide variety of product concentrations without adding surfaces.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of a T-clan concentrating device according to the present invention, and Fig. 2 shows 235U and 235U in the first device.
A schematic diagram for explaining each level of 38U, Figure 3 is the first
FIG. 2 is a schematic cross-sectional view showing an enlarged main part of the device shown in the figure. 1...Filament 2...Electron beam 3...Deflection magnetic field 4...Crucible 5... ...Metallic uranium 6... Atomic beam 7...236U atom 8...235U atom 9... ..... Second laser 11 --- 610. -1235U” 12...Ground electrode 13...Cathode electrode 14...Neutral atom collection plate Applicant
Toshiba Corporation Representative Patent Attorney Satoshi Suyama - 1st Self]

Claims (1)

[Claims] (1) Evaporate metallic uranium to generate an atomic beam, and add ^2^3^5U to the atomic beam, which is in an atomic gas state.
Irradiated with the first laser for selective excitation and then excited^2
In a uranium enrichment device using a laser method in which uranium is concentrated by irradiation with a second laser that ionizes ^3^5U, at least one of the opposing electrodes of the recovery electrode that recovers ionized ^2^3^5U is used. 1. A uranium enrichment device characterized in that an electrode is provided with a fulcrum, and a part of the recovery electrode is movably held in a direction away from an atomic beam flow.