Treatment Method and Treatment Apparatus for Uranium Hexaflouride Residue Within Cylinder, Using Gas Phase Reaction

Abstract

Embodiments of the disclosure relate to a treatment method and a treatment apparatus for a UF.sub.6 heel, using a gas phase reaction. A specific treatment method includes (1) vaporizing the UF.sub.6 heel, (2) manufacturing solid phase UO.sub.2F.sub.2 by using UF.sub.6 gas vaporized at step (1), (3) separating the solid phase UO.sub.2F.sub.2 and by-product gas from each other, and (4) separating hydrogen fluoride from the by-product gas. According to the disclosure, stabilization of a reconversion process and the quality of UO.sub.2 powder may be improved by manufacturing the solid phase UO.sub.2F.sub.2, which is an intermediate of the UO.sub.2 powder, through the UF.sub.6 heel treatment, and the high cost of radioactive waste disposal is reduced by minimizing the UF.sub.6 heel to be less than 0.5 kg.

Claims

1. A treatment method for a UF.sub.6 heel, the treatment method comprising: (1) vaporizing the UF.sub.6 heel; (2) manufacturing solid phase UO.sub.2F.sub.2 using UF.sub.6 gas vaporized at step (1); (3) separating the solid phase UO.sub.2F.sub.2 and by-product gas from each other; and (4) separating hydrogen fluoride from the by-product gas at step (4).

2. The treatment method of claim 1, wherein the vaporizing the UF.sub.6 heel at step (1) further comprises supplying an inert gas to vaporize the UF.sub.6 and raises the temperature to no less than a triple point of the UF.sub.6.

3. The treatment method of claim 1, wherein the separating hydrogen fluoride from the by-product gas at step (4) further comprises separating aqueous solution of hydrogen fluoride at a lower portion of a liquid/gas separator.

4. A treatment apparatus for a UF.sub.6 heel, the treatment apparatus comprising: a vaporizer for vaporizing the UF.sub.6 heel; a reactor connected to the vaporizer so as to manufacture the solid phase UO.sub.2F.sub.2 by using the UF.sub.6 gas generated at the vaporizer; a solid/gas separator connected to the reactor so as to separate the solid phase UO.sub.2F.sub.2, manufactured in the reactor, from by-product gas; a heat exchanger connected to the solid/gas separator so as to allow the by-product gas, supplied from the solid/gas separator, to pass therethrough and be condensed into liquid; and a liquid/gas separator configured to separate the hydrogen fluoride liquid, condensed at the heat exchanger, from the gas.

5. The treatment apparatus of claim 4, further comprising at least one gas phase distributor provided at the inside of the reactor for uniformly supplying the gas.

6. The treatment apparatus of claim 4, wherein, at least one of an inert gas and superheated steam is supplied in order to manufacture the solid phase UO.sub.2F.sub.2 in the reactor.

7. The treatment apparatus of claim 4, further comprising a fan provided by being connected to a side above the liquid/gas separator and configured to discharge at least a portion of the gas generated inside the liquid/gas separator.

8. The treatment apparatus of claim 4, wherein flow velocity inside the reactor is controlled to be higher than minimum fluidization velocity of UO.sub.2F.sub.2 powder.

9. The treatment apparatus of claim 4, wherein flow velocity inside the solid/gas separator is controlled to be lower than minimum fluidization velocity of UO.sub.2F.sub.2 powder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 shows a treatment method for a UF.sub.6 heel using a conventional cold trap;

[0020] FIG. 2 shows a reconversion process of the present invention;

[0021] FIG. 3 shows a method and a treatment apparatus for the UF.sub.6 heel of the present invention; and

[0022] FIG. 4 shows a UO.sub.2F.sub.2 reactor of the present invention.

DETAILED DESCRIPTION

[0023] Hereinbelow, exemplary embodiments of the present invention will be described in detail.

[0024] There is provided a treatment method for a UF.sub.6heel according to an embodiment of the present invention, the method including: (1) vaporizing the UF.sub.6 heel; (2) manufacturing solid phase UO.sub.2F.sub.2 using UF.sub.6 gas vaporized at step 1; (3) separating the solid phase UO.sub.2F.sub.2 and by-product gas from each other; and (4) separating hydrogen fluoride from the by-product gas above.

[0025] First, after vaporization of the UF.sub.6 inside a cylinder, to extract the UF.sub.6 heel, the temperature may be raised to no less than a triple point of the UF.sub.6 or, in some cases, pressure may be boosted by supplying an inert gas. Here, the inert gas includes, but is not limited to, nitrogen gas. In addition, extraction of the UF.sub.6 heel may be repeated according to an operation method for process of the UF.sub.6 heel treatment.

[0026] In a process of supplying the UF.sub.6 gas obtained by the above method to the reactor 72 manufacturing the UO.sub.2F.sub.2, depending on an amount of the UF.sub.6 gas, the inert gas and superheated steam are supplied at an appropriate ratio. Thus, the solid phase UO.sub.2F.sub.2 may be obtained using the gases supplied together as raw material according to reaction formula 1 below. Some of the solid phase UO.sub.2F.sub.2 manufactured at this time may be discharged to a side below the reactor 72.

UF.sub.6(g)+(2+)H.sub.2O(g)+N.sub.2(g).fwdarw.UO.sub.2F.sub.2 (s)+4HF(g)+xH.sub.2O(g)+N.sub.2(g)<Reaction formula 1>

[0027] The solid phase UO.sub.2F.sub.2 and the by-product gas, obtained from the UO.sub.2F.sub.2 reactor 72, are supplied to the solid/gas separator 73 so as to be separated from each other. Most of the solid phase UO.sub.2F.sub.2 is discharged to a side below the solid/gas separator 73, and the discharged UO.sub.2F.sub.2 is supplied to the UO.sub.2 conversion furnace 2 together with some of the solid phase UO.sub.2F.sub.2 having been manufactured in and discharged from the UO.sub.2F.sub.2 reactor 72.

[0028] While passing through a heat exchanger 741, a portion of the by-product gas separated from the solid/gas separator 73 may be condensed. Then the separated by-product gas is supplied to the liquid/gas separator 74, whereby gas, mostly nitrogen gas, in an upper portion may be discharged by a fan 742, and the aqueous solution of hydrogen fluoride separated in a lower portion may be transferred by a pump 743.

[0029] A treatment apparatus for the UF.sub.6 heel may include a vaporizer 71 used only for the UF.sub.6 heel for vaporizing the UF.sub.6 heel, a reactor 72 connected to the vaporizer 71 so as to manufacture the solid phase UO.sub.2F.sub.2 by using the UF.sub.6 gas generated at the vaporizer 71, a solid/gas separator 73 connected to the reactor 72 so as to separate the solid phase UO.sub.2 F.sub.2which is manufactured in the reactor 72, from by-product gas, a heat exchanger 741 connected to the solid/gas separator 73 so as to allow the by-product gas, which is supplied from the solid/gas separator 73, to pass therethrough and be condensed into liquid, and a liquid/gas separator 74 configured to separate the hydrogen fluoride liquid, which is condensed at the heat exchanger 741, from the gas.

[0030] As shown in FIG. 3, in the treatment apparatus for the UF.sub.6 heel, which is independent of the reconversion process, the pressure inside the UF.sub.6 cylinder may be boosted by supplying the inert gas to the inside of the UF.sub.6 cylinder according to the above-mentioned treatment method by using the vaporizer 71 used only for the UF.sub.6 heel. Alternatively, a separate device may be provided to vaporize the UF.sub.6 heel by raising the temperature of the UF.sub.6 heel to no less than the triple point.

[0031] The UF.sub.6 gas generated in the vaporizer 71 used only for the UF.sub.6 heel is supplied, together with the superheated steam and the inert gas containing a desired ratio of nitrogen, to the UO.sub.2F.sub.2 reactor 72 that manufactures the solid phase UO.sub.2F.sub.2. In this case, the UO.sub.2F.sub.2 reactor 72 may include a measuring instrument 721 and control valves 722A, 722B, and 722C as necessary, and a supply amount of the UF.sub.6gas may be adjusted by the provided measuring instrument 721 and control valve 722A. In addition, the superheated steam is controlled by the superheated steam control valve 722B, and the nitrogen gas is controlled by the nitrogen gas control valve 722C.

[0032] In the UO.sub.2F.sub.2 reactor 72, shown in detail in FIG. 4, by a gas phase distributor 723A of the UF.sub.6 gas for uniformly supplying the UF.sub.6 gas and a distributor 723B of the nitrogen gas or the superheated vapor, the solid phase UO.sub.2F.sub.2 is manufactured according to reaction formula 1. Some of the resulting solid phase UO.sub.2F.sub.2 may be discharged to a side below the UO.sub.2F.sub.2 reactor 72, but flow velocity inside the UO.sub.2F.sub.2 reactor 72 may be controlled to be higher than minimum fluidization velocity of the UO.sub.2F.sub.2 powder in order to allow the solid phase UO.sub.2F.sub.2 to be discharged to a side above the UO.sub.2F.sub.2 reactor 72.

[0033] The solid phase UO.sub.2F.sub.2 and by-product gas discharged from the upper portion of the UO.sub.2F.sub.2 reactor 72 are supplied to the solid/gas separator 73 so as to be respectively separated from each other. Here, most of the solid phase UO.sub.2F.sub.2 is discharged to the side below the solid/gas separator 73. In order to facilitate the solid phase UO.sub.2F.sub.2 to be discharged as above, flow velocity inside the solid/gas separator 73 is controlled to be lower than the minimum fluidization velocity of the UO.sub.2F.sub.2 powder. The solid phase UO.sub.2F.sub.2 thus separated is supplied to the UO.sub.2 conversion furnace 2 together with the solid phase UO.sub.2F.sub.2 discharged from the side below the previous UO.sub.2F.sub.2 reactor 72. In this case, a shape of the solid/gas separator 73 is not limited, and apparatus conditions are to be set so that the by-product gas does not condense inside the solid/gas separator 73.

[0034] The liquid/gas separator 74 may include a heat exchanger 741 at a front end, a fan 742 at a rear end thereabove, and a pump 743 at a rear end therebelow, wherein the by-product gas discharged from the solid/gas separator 73 may pass through the heat exchanger 741 and condense into an aqueous solution of low concentration hydrogen fluoride. Then condensed aqueous solution and the by-product gas are supplied to the liquid/gas separator 74 so as to be separated from each other. Subsequently, the aqueous solution of low concentration hydrogen fluoride may be separated at the lower portion of the liquid/gas separator 74, and the aqueous solution of low concentration hydrogen fluoride thus separated is processed by the pump 743 connected to the liquid/gas separator 74. The by-product gas from which hydrogen fluoride has been removed may be composed of mostly nitrogen gas and is discharged by the fan 742 connected to the side above the liquid/gas separator 74. The fan 742 connected to the side above the liquid/gas separator 74 may contribute to play a role in maintaining most of the process of the present invention at an appropriate negative pressure and preventing the radioactive material from leaking to the outside.

[0035] The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and those skilled in the art will appreciate that various substitutions, alterations, and modifications are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

[0036] All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0037] The use of the terms a and an and the and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms comprising, having, including, and containing are to be construed as open-ended terms (i.e., meaning including, but not limited to,) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., such as) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0038] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.