JPH0638893B2 - Isotope separation by laser light and gas phase substance synthesis method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is a compound having an arbitrary isotopic composition obtained by combining an isotope separation method using laser light and a gas phase substance synthesis method using laser light as a heat or energy source. Related to the process that enables continuous production of high purity and controllability by laser light, which is widely applicable to nuclear fuel production / processing, superconducting material production, uranium enrichment, ceramics production, reactor materials, material optics, etc. The present invention relates to body separation and gas phase substance synthesis methods.

[Conventional technology]

Conventionally, a gas diffusion method, a gas centrifugation method, a chemical exchange method and the like have been used as the isotope separation method.

In the gas diffusion method, for example, when a mixed gas of ²³⁵ UF and ²³⁸ UF is put in a container and a pressure difference is applied to the container with a porous diaphragm as a boundary and the gas is moved from the high pressure side to the low pressure side through the diaphragm, the average freeness of gas molecules is increased. Since the process is proportional to the pressure difference, if the pressure is sufficiently low when passing through the pores, the individual molecules move independently while moving without colliding with each other. In that case, if the system is in thermal equilibrium, the lighter molecules are faster than the heavier ones when the system is in thermal equilibrium, so the migration velocity of the lighter molecule is larger and the lighter molecule concentration is higher on the low pressure side, thus separating the isotopes. be able to.

In the gas centrifugation method, a mixed gas is put into a cylindrical container, and when it is rotated, the gas also rotates at the same angular velocity due to viscosity. In this case, centrifugal force acts on the gas molecules, and light molecules are concentrated more near the midpoint of rotation and heavier molecules near the periphery. That is, a pressure gradient that balances the centrifugal force is created in the inside of the rotary cylinder, and the molecules move due to pressure diffusion. When the concentration change in the radial direction thus generated progresses to some extent, on the contrary, mass diffusion based on the concentration gradient occurs, and an equilibrium concentration distribution is created at some point. Utilizing this concentration distribution, a concentrated flow near the center of rotation and a depleted flow near the periphery can be extracted for isotope separation.

In the chemical exchange method, although chemical properties do not change between isotopes, strictly speaking, the chemical equilibrium and reaction rate are slightly different due to the difference in nuclear structure and mass number. The product can be obtained from the top of the column and the waste material can be obtained from the bottom of the column by refluxing through a packed column packed with an ion exchange resin having a very high ion exchange rate.

Further, in the gas phase substance synthesis method, synthesis is mainly performed by sealing a raw material substance in a reaction vessel and heating and pressurizing it.

[Problems to be Solved by the Invention]

However, the conventional isotope separation method, gas diffusion method,
Both the gas centrifugal separation method and the chemical exchange method have a small separation coefficient per one stage, so that it is necessary to form a cascade to obtain the required enrichment, and there is a problem that a large-scale separation process is required for production. there were.

In addition, the conventional substance synthesis method mainly focuses on the process of synthesizing by heating and pressurizing in the reaction vessel,
There are drawbacks such that it takes a long time to start and stop the reaction and impurities are mixed in from the inner wall of the reaction vessel.

In contrast to these conventional methods, the isotope separation method using laser light has a high isotope selectivity and a high separation coefficient can be obtained by one irradiation, and the isotopic composition of the raw material can be varied widely and arbitrarily. it can.

In addition, the gas-phase synthesis method that uses a laser as an energy or excitation source is a non-contact process in which only laser light is used in space, so high-purity products can be obtained, and the reaction start-up and stop times are extremely short. In addition, since the intensity of laser light can be controlled arbitrarily and in a short time, it is a method of synthesizing substances with good controllability of reaction, and it is a substance synthesizing method in the industrial field that utilizes the characteristics of substances with changed natural isotope composition. It was very promising as a law, and its realization was strongly desired.

The present invention has been made in view of the above circumstances, and combines a laser isotope separation method with high isotope selectivity and a large separation coefficient and a material synthesis method using laser light as a heat or energy source, each independently. By providing the advantages of the existing process, it is possible to provide a compound having an arbitrary isotopic composition with high purity, good controllability, and continuous production of isotope separation by laser light and gas-phase substance synthesis method. The purpose is to do.

[Means for Solving the Problems]

Therefore, in the method of isotope separation and gas phase substance synthesis by laser light of the present invention, a step of selectively exciting a specific molecule of a gaseous compound containing a specific isotope by the first laser light irradiation, selective excitation The method is characterized by comprising the steps of post-purification to obtain an intermediate product, mixing the intermediate product with a reaction gas, and irradiating the mixed gas with a second laser beam to cause a chemical reaction. When selectively exciting a specific molecule by irradiating the laser beam, the raw material gas is mixed with a reaction auxiliary gas, and the first laser beam is a pulsed carbon dioxide gas laser or a Raman laser beam,
The second laser light is CW carbon dioxide laser light.

[Action]

INDUSTRIAL APPLICABILITY The present invention combines the laser isotope separation method with high isotope selectivity and a large separation coefficient and the material synthesis method using laser light as a heat or energy source, and has the advantages of independent processes. By extracting the compound, it is possible to produce a compound with an arbitrary isotopic composition with high purity and good controllability and continuously, and a small-scale process is possible, which makes the process scale small and economical. It enables various isotope synthesis processes.

〔Example〕

 Embodiments will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the process configuration of the present invention. In the figure, is the source gas, is the scavenger gas,
Is a gas mixing tank, is a separation irradiation cell, is a gas purifier,
Is a waste gas, is a gas mixing tank, is a reaction gas, is a reaction cell, is a product recovery tank, is a vacuum pump, is waste gas, isotope separation laser, and is a chemical reaction laser.

In the figure, the raw material gas and the scavenger gas are mixed in a gas mixing tank and transferred to a separation irradiation cell. The scavenger gas is added as a reaction auxiliary gas for promoting the selective chemical reaction of the isotope, and is for increasing the yield of the reaction. It may be added as necessary and may be omitted in some cases. A target compound is excited by irradiating a gaseous compound containing a specific isotope as a raw material, which is placed in a good cell, with a first laser light whose oscillation wavelength is tuned to a gaseous compound by a laser. , Promotes isotope-selective dissociation or chemical reaction. By adjusting the wavelength, fluence, and irradiation time of the first laser light, it is possible to control the composition ratio of the specific isotope in the raw material or the product of dissociation and chemical reaction. At the stage of irradiating with the first laser light, the raw material is adjusted to have a specific isotope and changes into a chemical form different from that of the raw material. Next, the gas is refined by a gas purifier to separate the waste gas and become an intermediate product. The reaction gas is added to the intermediate product thus obtained, mixed in a gas mixing tank, and transferred to a reaction cell. The second laser beam is irradiated by the chemical reaction laser in the state of being housed in the reaction cell, and the energy is used to cause the reaction between the intermediate product and the reaction gas. The product obtained as a result of the reaction is transferred to a product recovery tank, and the target product can be obtained by discharging waste gas with a pump. It is possible to easily control the particle size, density, compound composition, etc. of the solid compound obtained by changing the flow rate, mixing ratio, etc. of the mixed gas that receives laser light irradiation.

Next, a specific application example of the present invention will be described below.

FIG. 2 is a diagram showing a B ₄ C production process enriched in ¹⁰ B isotopic composition.

Boron isotope (natural abundance ¹¹ B: 19.8)
%, ¹⁰ B: 80. %), ¹⁰ B has a large neutron absorption cross section, and is therefore used as a reactor control material in the form of ceramics (boron carbide B ₄ C) with excellent heat and corrosion resistance. BCl ₃ (boron trichloride) as a raw material, F ₂ (fluorine) as a scavenger gas, and C ₂ H ₄ as a reaction gas.
(Ethylene) and B ₂ H ₆ (diborane) are used, a pulsed carbon dioxide laser is used for the isotope separation laser, and a CW carbon dioxide laser is used for the chemical reaction laser.

First, BCl ₃ having a natural abundance ratio and fluorine gas are introduced into a gas mixing tank and mixed, and the mixed gas is supplied to an irradiation cell for separation. Next, the laser light of the laser for isotope separation
By irradiating the separation cell in accordance with the absorption lines of ¹¹ BCl _3, selectively energizing from a mixed gas only ¹¹ BCl _3. As a result, ¹¹ BCl ₃ causes the following reaction and is combined with fluorine to become ¹¹ BCl ₃ F. ¹¹ BCl ₃ + hν + F ₂ → ¹¹ BCl ₃ F + 1 / 2F ₂ (1) At this time, the composition ratio of ¹⁰ BCl ₃ can be relatively adjusted by adjusting the reaction rate of ¹¹ BCl ₃ .

Then, to purify the BCl ₃ by utilizing the difference of the physical properties of vapor pressure and the like of BCl ₃ and BCl ₃ F. The purified BCl ₃ is introduced into the gas mixing tank, B ₂ H ₆ , C ₂ H ₄ and Ar are mixed, and then supplied to the reaction cell.

By irradiating the reaction cell with the laser for chemical reaction, boron carbide is produced from the following reaction.

2BCl ₃ + 3B ₂ H ₆ + C ₂ H ₄ → 2B ₄ C + 6HCl + 8H ₂ (2) Of the reaction products, HCl and H ₂ are gases,
Separate and remove with a filter or the like. In this way, B ₄ C can be easily manufactured.

Figure 3 shows UO ₂ (solid) enriched with ²³⁵ U isotopic composition.
It is a figure which shows the process of manufacturing.

Uranium isotope (natural abundance ²³⁵ U: 0.7%, ²³⁸
U: 99.3%), ²³⁵ U, which is enriched to about 3% as a fission nuclide, is used as a fuel for a nuclear reactor in the form of UO ₂ (uranium dioxide).

Uranium hexafluoride UF ₆ as a raw material, hydrogen chloride HCl as a scavenger gas, and carbon dioxide CO as a reaction gas.
₂ , a pulsed carbon dioxide laser and a Raman laser are used as the isotope separation laser, and a CW carbon dioxide laser is used as the laser for chemical reaction.

First, UF ₆ having a natural abundance ratio and hydrogen chloride gas are introduced into a gas mixing tank and mixed, and the mixed gas is supplied to an irradiation cell for separation.

Next, the laser beam of the laser for isotope separation is set to ²³⁵ UF ₆
The separation irradiation cell is irradiated according to the absorption line of No. _{3, and} only ²³⁵ UF ₆ is selectively excited from the mixed gas. As a result, ²³⁵ UF ₆ undergoes the following reaction to combine with hydrogen chloride to form ²³⁵ UF ₅ Cl. ²³⁵ UF ₆ + hν + HCl → ²³⁵ UF ₅ Cl + HC (3) At this time, by adjusting the reaction rate of ²³⁵ UF ₆ , U
It is possible to adjust the composition ratio of ²³⁵ U in F ₅ Cl.

Next, UF ₅ Cl is purified by utilizing the difference in physical properties such as vapor pressure of UF ₆ and UF ₅ Cl.

UF ₅ Cl is introduced into the purified gas mixing tank, mixed with CO ₂ and Ar, and then supplied to the reaction cell.

By irradiating the reaction cell with the laser for chemical reaction, uranium dioxide is produced from the following reaction.

UF ₅ Cl + 2CO ₂ → UC ₂ + C ₂ F ₅ Cl + O ₂ (4) Of the reaction products, C ₂ F ₅ Cl (chlorofluoroethane) and O ₂ are gases and thus separated and removed, and UO ₂ Can be obtained.

〔The invention's effect〕

As described above, according to the present invention, the following effects can be achieved.

(1) A compound having an arbitrary isotope composition and powder properties can be obtained as a product.

(2) Since it is a non-contact process, a high-purity product can be obtained.

(3) Since it is a continuous process, the manufacturing cost can be reduced.

(4) Compact manufacturing equipment is possible.

(5) It is possible to improve safety, efficiency, maintainability, accuracy, certainty, etc., and also to improve simplification, labor saving, and large (small) size.

[Brief description of drawings]

FIG. 1 is a block diagram showing the process structure of the present invention, and FIG.
The figure shows the production process of B ₄ C enriched with ¹⁰ B isotopic composition, and FIG. 3 shows the UO ₂ enriched with isotopic composition of ²³⁵ U.
It is a figure which shows the process of manufacturing (solid). ...... Raw material gas …… Scavenger gas …… Gas mixing tank …… Separation irradiation cell …… Gas purifier
…… Waste gas, …… Gas mixing tank, …… Reaction gas,
...... Reaction cell, ・ ・ ・ Product recovery tank, ・ ・ ・ Vacuum pump, ・ ・ ・ Waste gas, ・ ・ ・ Isotope separation laser, ・ ・ ・
… A laser for chemical reactions.

Claims (4)

[Claims] 1. A step of selectively exciting a specific molecule of a gaseous compound containing a specific isotope by irradiation with a first laser beam, a step of selectively exciting and then purifying to obtain an intermediate product, and reacting the intermediate product. A method of isotope separation and gas phase substance synthesis by laser light, which comprises the steps of mixing with a gas and irradiating the mixed gas with a second laser light to cause a chemical reaction. 2. The isotope separation and gas phase substance synthesis method by laser light according to claim 1, wherein a reaction auxiliary gas is mixed with a raw material gas when the specific molecule is selectively excited by the first laser light irradiation. 3. The isotope separation and gas phase substance synthesis method using laser light according to claim 1, wherein the first laser light is pulsed carbon dioxide laser light or Raman laser light. 4. The method for isotope separation and gas phase substance synthesis by laser light according to claim 1, wherein the second laser light is CW carbon dioxide laser light.