JPS6238001B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a centrifugal liquid/liquid extractor, particularly to a centrifugal extractor used in a nuclear fuel reprocessing process.

The extraction process in nuclear fuel reprocessing employs the Purex method, which involves bringing a fuel solution dissolved in nitric acid into countercurrent contact with an organic solvent to extract U and Pu, followed by washing and back extraction. In this nuclear fuel reprocessing process, conventional pulse columns and gravity separation type mixers/settlers are often used. However, if the amount of radiation is higher than before, such as spent fuel from fast reactors, when processed using the conventional extractor described above, the extraction solvent will be severely damaged by the radiation, and the quality of the extraction solvent will change, resulting in Various problems may occur, including a decrease in efficiency in the process. For this reason, centrifugal extractors, which have a short contact time between the spent fuel solution and the extraction solvent and are less susceptible to solvent damage, are being used in reprocessing processes with high radiation doses, such as fast reactor fuel reprocessing processes. There is.

As a conventional centrifugal extractor for nuclear fuel reprocessing, there is one having a structure shown in FIG. 1, for example. In the figure, reference numeral 1 denotes a rotating body attached to a rotating shaft 3 that is rotated by a drive source (not shown) inside a casing 2. This rotating body 1 is attached to the rotating shaft 3 at an upper end plate 4, and at a lower end plate 5. It has a central opening 6. The rotating shaft 3 passes through the rotating body 1, passes through the central opening 6 of the lower end plate 5, and has rotating blades 7 fixed to the lower end. The rotary vane 7 is housed in a pump chamber 11 formed by providing a partition plate 10 having an opening 9 on the outer periphery on the lower surface side of the bottom plate 8 of the casing 2, and a feed of processing liquid is provided in the lower part of the pump chamber 11. A pipe 12 is connected to the feed pipe 12, and a fuel solution supply pipe 13 and a solvent supply pipe 14 are further connected to the feed pipe 12. In the casing 2, a cylinder 15 and a bottom plate 8 are fastened together by bolts 16, and a flange 17 at the top of the cylinder 15 is fastened to a base 18 together with a shielding plate 19 by bolts 20. In addition, a stirring plate 21 is attached to the upper surface side of the bottom plate 8 in the rotating body 1, and a baffle plate 22 is fixed to the rotating shaft 3 so as to be disposed at a position opposite to this stirring plate 21. Further, a funnel-shaped dispersion plate 23 is provided on the lower surface side of the upper end plate 4, with the lower large-diameter end having a predetermined gap between it and the inner surface of the cylindrical part of the rotating body 1, and the upper small-diameter side having a light dispersion plate 23. A liquid phase weir 24 is formed and a light liquid discharge port 25 is provided. Further, a heavy liquid phase weir 26 and a heavy liquid discharge port 27 are provided on the inner surface of the cylindrical portion of the rotating body 1 between the dispersion plate 23 and the dispersion plate 23 . Furthermore, annular light and heavy liquid collection chambers 28 and 29 are provided on the inner surface of the cylinder 15 of the casing 2 facing the light and heavy liquid discharge ports 25 and 27.

In the centrifugal extractor formed in this way, a fuel solution of U or Pu nuclear fuel dissolved in nitric acid and an organic solvent are supplied from the respective supply pipes 13 and 14 to the pump chamber 11 via the feed pipe 12, and the rotating shaft 3 By rotating them, they are mixed by the rotating blade 7 and U or Pu is extracted. The mixed treatment liquid of fuel solution and solvent passes through the opening 9 of the partition plate 10 and reaches the rotating body 1.
It is supplied into the rotating body 1 from the central opening 6 of the lower end plate 5, and is further agitated between the buffer plate 22 and the lower end plate 5 to extract U or Pu. It is separated into a heavy liquid with a heavy density and a light liquid with a low specific gravity. The separated heavy liquid and light liquid are separated by a dispersion plate 23 and pass through a light liquid phase weir 24 for light liquid, and then from a light liquid outlet 25 to a light liquid collection chamber 28, and the heavy liquid passes through a heavy liquid phase weir 26. After that, the heavy liquid is collected from the heavy liquid outlet 27 into the heavy liquid collection chamber 29 . Next, collection room 2
The light and heavy liquids collected at 8 and 29 are sent to the next stage (not shown), respectively. However, in the centrifugal extractor formed in this way, the rotary blade 7 is larger than the opening in the bottom plate 8 of the casing 2 that concentrically surrounds it, and the center hole of the partition plate 10 of the pump chamber 11, so that it is larger than the stationary part. If the rotating part, which has a high chance of failure due to its structure, breaks down, the centrifugal extractor can be disassembled by removing the bolts 16 and disassembling it from the bottom of the centrifugal extractor. Because the entire centrifugal extractor is isolated by a shield and has a high radiation dose, it is impossible for humans to enter and disassemble it, so it is controlled remotely using a manipulator. In such cases, the inside of the centrifugal extractor is extremely complex, and not only does it take a considerable amount of time to disassemble and assemble, but if the centrifugal extractor is disassembled from the bottom, the nuclear fuel solution remaining inside the centrifugal extractor may flow out onto the floor. Of course, work procedures have been established to prevent this from happening, but when handling nuclear fuel, it is necessary to ensure that the above does not occur under any circumstances.

As described above, conventional centrifugal extractors have poor workability during disassembly and assembly, and lack maintainability. The present invention focuses on this point and provides a centrifugal extractor for nuclear fuel reprocessing that can be easily disassembled and assembled.

Hereinafter, a centrifugal extractor according to the present invention will be explained using the drawings.

FIG. 2 is a sectional view showing a longitudinal section of the centrifugal extractor, and FIG. 3 is an enlarged sectional view showing the main part of FIG. 2.

In the figure, reference numeral 30 denotes a base, and a base 31 is installed on this base 30, and a drive unit 32 is further provided on the base 31. In the drive unit 32, an electric motor 34 having a rotating shaft 33 extending vertically downward is attached to a support base 36 having bearings 35a and 35b, and the support base 36 is installed on the base base 31 by tightening bolts 36a. It is being A casing 38 is provided inside the base 31 and is fixed to the base 30 with a dish-shaped bottom plate 37. It is provided. casing 38
A hollow cylindrical rotating body 40 whose enlarged cross section is shown in FIG. 3 is attached to the lower end of the inner rotating shaft 33 with a lower end plate 41. 38, it can be extracted through the upper opening of the base 31. A central shaft 42 passes through the center of the interior of the rotating body 40, a light liquid side weir 43 and a heavy liquid side weir 44 are arranged at the inner upper part of the rotating body 40, and a baffle plate 45 is attached to the central axis 42. 40 inner wall surface and light, light liquid side weir 43, 4
4 at a predetermined interval, and an impeller 49 is fixed to the lower end thereof so as to pass through the partition plate 46 and the central opening 48 of the lower end plate 47 of the rotating body 40. .

The impeller 49 has a shaft portion 49a whose upper end is fixed to the partition plate 46 and a smaller outer diameter than the shaft portion 49a which is planted at the lower end of the shaft portion 49a, as shown in FIG. 4 when viewed in the direction of arrow A. The blades 49b are formed by the blades 49b. Bottom plate 3
A partition cylinder 51 forming a liquid reservoir 50 is provided at a position facing the lower end plate 47 of the rotating body 40 on the upper surface of the rotating body 7 .
1 is attached to the inner surface. At the center of the partition plate 52, an impeller 49 inserted from the upper part of the partition tube 51 and a funnel-shaped cylinder 54 with a small diameter opening at the lower end forming the pump 53 are fixed. A minute gap is provided between the portion 49a and the portion 49a. The upper part of the cylindrical body 54 is disposed to pass through the gap between the inner end surface of the opening 48 of the lower end plate 47 and the impeller 49. Further, a fuel solution supply pipe 55 and a solvent supply pipe 56 that open to the liquid reservoir 50 are connected to the bottom plate 37 . Furthermore, a nozzle 57 for spouting cleaning liquid inward is attached to the upper part of the casing 38, and an annular cleaning liquid receiving container 58, a light liquid receiving container 59, and a heavy liquid receiving container are provided on the inner surface of the casing 38 below the nozzle 57. 60 is disposed with its inner end having a minute gap with the rotating body 40. In addition, light and heavy container 59,
60 is a light hole drilled in the wall surface of the rotating body 40 near the attachment portions of the light and heavy liquid side weirs 43 and 44 of the rotating body 40;
It is arranged to face the heavy liquid extraction holes 61 and 62, and collects the light and heavy liquid discharged from the respective extraction holes 61 and 62, respectively. Furthermore, the liquid received in the receiving containers 58, 59, 60 is sent out to the next stage through respective discharge pipes 63, 64, 65 attached to the casing 38.

Since the substance handled by the rotating body 40 is nuclear fuel, criticality safety must naturally be considered. For this reason, the inner diameter of the rotating body 40 is formed to be 15.7 cm or less. This is because the reprocessing solution contains uranium, plutonium, etc.
Focusing on plutonium-239, the subcritical limit of the diameter of its cylindrical liquid is 15.7 cm, and to maintain criticality safety due to the shape of the device, the diameter of the rotating body used in the centrifugal extractor must be at least less than this. Because it has to be.

Next, the operation of the present invention configured as described above will be explained. The rotating body 40 is rotated in the direction of the arrow B in FIG. 4 by the electric motor 34 serving as a rotational power source, and is increased to a predetermined rotational speed. On the other hand, a fuel solution in which nuclear fuel as a raw material is dissolved in nitric acid and an extraction solvent are supplied to the liquid reservoir 50 through respective supply pipes 55 and 56.
A pump 53 having a small diameter opening at the lower end at 0, that is, a rotating body 4
The rotating body is driven by a centrifugal pump formed by an impeller 49 concentrically fixed to the central shaft 42 at the bottom of the casing 38, and a cylinder 54 concentrically fixed to the rotating body 40 on the partition plate 52 of the casing 38. 40 through a central opening 48 in the lower end plate 47. Another function of this pump 53 is to mix and stir the fuel solution sucked into the liquid reservoir 50 and the extraction solvent, thereby promoting the extraction of uranium and plutonium, which are the target substances. Rotating body 40
supply within. Note that since the diameter of the shaft portion 49a of the impeller 49 is made larger than the diameter of the blades 49b, a pumping action equivalent to that of the conventional pump can be obtained. As described above, the mixed liquid that has been mixed and stirred and supplied to the rotating body 40 by the pump 53 is lighter due to the difference in specific gravity in the rotating body 40 due to the centrifugal effect determined by the diameter and rotational speed of the rotating body 40 and the properties of the liquid. Separated into liquid and heavy liquid. That is, in the rotating body 40, a heavy liquid having a high specific gravity is separated to the outside within the rotating body 40, and a light liquid having a low specific gravity containing extracted uranium or plutonium is separated to the inside within the rotating body 40. .

The liquid separated in this way passes through the heavy liquid side weir 44 and flows into the heavy liquid receiving container 60 fixed to the casing 38 through the heavy liquid extraction hole 62 formed on the side surface of the rotating body 40. It passes through the discharge pipe 65 and is collected outside. On the other hand, the light liquid is extracted from a light liquid receiving container 59 fixed to the casing 38 through a light liquid extraction hole 61 formed on the side surface of the rotating body 40 beyond the light liquid side weir 43.
and is collected outside through the discharge pipe 64.

Here, the heights of the heavy liquid side weir 44 and the light liquid side weir 43 are determined by the following formula.

r _a : Height radius of heavy liquid weir r _p : Height radius of light liquid weir R : Inner radius of rotating body λ : Density ratio of light liquid to heavy liquid Va : Flow rate of heavy liquid Vo : Flow rate of light liquid Next For example, when the centrifugal extractor according to the present invention is operated for a predetermined period of time or malfunctions, it is necessary to disassemble it. When disassembling it, first, the cleaning liquid is poured into the casing 38 from the nozzle 57 fixed to the casing 38. The inside is thoroughly cleaned and the radiation dose is sufficiently reduced. Most of this cleaning liquid remains in the cleaning liquid receiving container 58 and is recovered to the outside through the discharge pipe 63.

After thoroughly cleaning with a cleaning liquid, by removing the bolts 36a that fasten the support base 36,
The support stand 36 and the base stand 31 can be disassembled into upper and lower parts. Of course, the hole diameters of the upper opening of the base 31 and the upper opening of the casing 38 are larger than the outer diameter of the rotating body 40, the inner diameter of the cylinder 54 is larger than the outer diameter of the impeller 49, and furthermore Since the opening diameter of the central opening 48 of the lower end plate 47 of the rotating body 40 is large, the casing 38 and the base 31 of the rotating body 40
The rotary body 40 can be pulled out for predetermined inspection and maintenance or for repair in the event of a failure.

As described above, the centrifugal extractor of the present invention is easier to disassemble than conventional centrifugal extractors, and is advantageous in maintainability such as replacement of the rotating body. For this reason, there is no need for long periods of disassembly and assembly, reducing the chance of exposure to radiation for the handler, and furthermore, there is no risk of the nuclear fuel solution remaining in the centrifugal extractor leaking outside during disassembly, resulting in safety. This will make a significant contribution to the

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a conventional centrifugal extractor, FIG. 2 is a longitudinal sectional view showing a centrifugal extractor according to the present invention,
3 is a longitudinal cross-sectional view showing an enlarged view of the essential parts of the present invention shown in FIG. 2, and FIG. 4 is a plan view taken in the direction of arrow A in FIG. 3. 32... Drive unit, 33... Rotating shaft, 38... Casing, 40... Rotating body, 42... Center shaft, 4
7... Lower end plate, 48... Center opening, 49... Impeller, 50... Liquid reservoir, 54... Cylindrical body.

Claims (1)

[Claims of Claims] 1. A casing having a drive unit disposed in the upper part with a rotating shaft hanging therein, and a lower end plate provided in the casing and having an opening in the center, which is attached to the lower part of the rotating shaft. a hollow cylindrical rotating body, a central shaft coaxially extending through the rotating body, and an impeller attached to the lower end of the central axis and extending through the central opening of the lower end plate; a liquid reservoir provided in the casing, facing the lower part of the impeller and partially built therein; and a liquid reservoir fixed to the upper part of the liquid reservoir and having an open upper end inside the rotating body, and the impeller and the lower end plate A centrifugal extractor comprising: a cylindrical body provided with a predetermined gap between the inner end surface of a central opening and a cylindrical body with a predetermined gap therebetween. 2. The centrifugal extractor according to claim 1, wherein the inner diameter of the rotating body is 15.7 cm or less.