JP2545583B2 - Apparatus and method for continuous chemical activation of uranium trioxide powder - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus and method for chemically activating powdered uranium oxide such as reprocessed recovered uranium (finely concentrated UO ₃ ). Specifically, it relates to an apparatus and method for chemically activating the same substance by hydration.

[Problems to be Solved by Prior Art and Invention]

In the case of chemically treating a powdery substance industrially, it may be preferable to perform an appropriate pretreatment because the chemical treatment is sufficiently performed. As one of them, there is a pretreatment by hydration when denitrifying uranium trioxide is fluorinated into uranium hexafluoride. For example, reprocessed recovered uranium (finely concentrated UO ₃ ) is heated to 300 ° C. The specific surface area increases when it is poured into sushi water, but the HF fluorination reactivity is rather low (and re-drying etc. are required). On the other hand, it was confirmed that the method of spraying water on uranium trioxide which is fluidized in the fluidized bed destroys the normal fluidized state due to the agglomeration of the powder and the hydration does not proceed.

Therefore, as a result of examination, when uranium trioxide was mechanically stirred while maintaining the powder state, water was added dropwise from the upper part, and batch hydration treatment was performed. It was confirmed that the reactivity was also high.

However, in this batch system, it is difficult to make it continuous, and if a certain amount of cohesion is created, a chain fission reaction occurs and it is extremely unfavorable, so-called critical control is necessary,
For fissile materials such as micro-enriched uranium trioxide, it is necessary to increase the capacity of the batch type processing equipment especially when it is desired to process a large amount on a commercial scale. It is also economically impractical to provide such a commercial process.

The present invention intends to solve such a problem of the above-mentioned conventional technique.

[Means and Actions for Solving the Problems]

The present invention was finally obtained by the inventors after earnest studies to overcome the above problems.

That is, the present invention is: an apparatus for continuously activating and chemically activating uranium trioxide powder: a plurality of rotations having a central axis on substantially the same horizontal plane parallel to the traveling direction of the object to be treated. Having a shaft; having stirring blades arranged along each axis along each axis; ranges covered by rotation of the stirring blades on adjacent shafts partially overlap each other when viewed from the axial direction But each stirring blade has an adjacent shaft and a stirring blade arrangement that does not come into contact with the stirring blades on that shaft; bottom, side wall and top wall parallel to the rotation axis, and end walls located at both ends thereof A container having an inlet for the object to be treated at one end and an outlet for the object to be treated at the other end; this container is located near the outlet end and is farther from the outlet end side end wall than the outlet, and has an upper end. Has a weir lower than the inner surface of the upper wall; the inner surface of the bottom is slightly larger than the circle formed by the outermost circumference of rotation of each stirring blade A cross-section of a plane perpendicular to the axis of rotation on which arcs of different radii and concentric with this circle are lined up; a device with at least one water supply device and an exhaust port, and The object powder is quantitatively supplied from the inlet of the above-mentioned device in which the stirring blade is operating, and water is quantitatively supplied from the water supply device, and the object powder that has passed through the weir to the outlet is taken out from the outlet. The present invention provides a method for chemically activating a powder to be treated by hydration.

Substances such as uranium trioxide, whose chemical reactivity is improved by hydration, cause a hydration reaction with water in a solid-liquid heterophasic system, but when reacted in the form of a slurry or paste containing a lot of water, it will be dried or powdered afterwards. However, it is desirable that the powder to be treated be mixed with the required amount of water as it is to achieve the desired hydration. It was found that it is better to use the above-mentioned apparatus and method to meet this condition and solve the above problems. The apparatus according to the present invention can be said to be one of mixers or feeders used for mixing or supplying powder or granular substances. The above-mentioned configuration is provided with a water supply device and an exhaust port, and chemicals are obtained by hydration. It has to be awaited by the present inventor that the desired result can be obtained by continuously treating uranium trioxide having an improved reactivity with an appropriate amount of water and mechanical stirring.

FIG. 1 shows an example of a six-axis type device according to the present invention (a: perspective view showing an outline, b: conceptual sectional view, c: conceptual side view), and another example of the present invention. In the conceptual side view of FIG. 3b, which will be described below, first, the rotating shafts 15 are rotated and the stirring blades (paddles) 19 are operated, so that at least about one per two rotating shafts in the container 100. The powder of the object to be treated, which is evenly divided and is supplied quantitatively from the non-illustrated supply port, is hit by the agitating blades and does not accumulate on the bottom or agglomerate at the bottom and moves up and down (axial direction). The water is randomly shaken and stirred with water to the left and right (in the direction perpendicular to the axis) to move from the inlet 3 to the outlet 99 while being hydrated and discharged.

It can be said that the purpose of continuation can be achieved if there are two rotary shafts, but since there is a limit to the practical shaft length, the processing capacity is not sufficient for the practical purpose. The present inventor has determined that it is necessary to provide a shaft to synergistically improve not only the throughput but also the product quality.

The term "multi-axis" as used in the present invention means that the number of rotary shafts is three or more. Usually, it is preferably 4 to 10, more preferably 4 to 10.
The one provided with eight is easy to put into practical use and is effective.

Further, it is generally preferable to configure the rotary shaft with an even number in terms of preventing vibration during operation.

The stirring blade is usually shaped to have a fan-shaped or arcuate main plane (blade plane), and the curved portion is fixed to the shaft so as to rotate slightly away from the curved surface of the bottom of the container. Not parallel to the vertical plane (rotation plane)
The unprocessed object is pushed by the rotation at an angle of more than 180 degrees and less than 180 degrees. For convenience, this face of the rotary vane is 0 degrees when facing the inlet end and 180 degrees when facing the outlet end.
Degree.

This inclination of the individual stirring blades may be in any direction in which the object to be processed is pushed by the operation of the stirring blades in the direction of the rotation axis, and also between the individual stirring blades and between the groups of stirring blades on the individual rotation axes. Alternatively, it is preferable to select and change any combination depending on the required degree of reaction of the object to be treated and residence time, rather than keeping the directions fixedly matched or fixedly different.

In order to facilitate such a change, the stirring blade may be fixed to the rotating shaft by means of screwing or the like via a suitable arm which is typically a round bar. The blade plane may be a convex or concave surface instead of a perfect plane, but in that case, it is preferable that the angle can be arbitrarily changed with respect to the rotation surface from the same viewpoint.

The rotation direction of each rotation shaft does not necessarily have to be the same between the rotation shafts, and it is preferable that the rotation direction can be arbitrarily changed according to the processing needs. If the inclination of the stirring blade makes the rotation direction variable as described above, it is convenient because the degree of stirring and the feed rate can be adjusted more than just changing the rotation speed. By appropriately selecting the stirring degree and the feeding speed, the processing can be completed in the shortest time according to the object to be processed.

In the apparatus according to the present invention, even if the stirring blades are all rotated to push the object to be processed from the outlet toward the inlet in the plane of the blade, the object powder is fluidized by stirring, so Is sent to the weir while being hydrated and is taken out from the outlet after passing over the weir.

The water supply device divides 1-1.5 times, preferably 1.1-1.3 times, the amount of water necessary for the hydration of the material to be treated or a slight excess, that is, 1.1-1.3 times the equivalent amount, from one location on the upper wall or appropriately dividing it. It is supplied to the object from a plurality of locations according to the supply of the object by an appropriate method such as spraying or dropping.

The supply of the material to be treated from the inlet is preferably quantitative, and is generally the same, but the supply of water is also the same. As water, pure water purified by ion exchange or distillation is usually used.

Water vapor that may be generated by stirring and mixing the object to be treated and water is guided to the outside of the apparatus from the exhaust port, and is preferably discharged through a filter suitable for removing the particles of the object to be treated, Before discharging, it can be recovered as water by using a condenser, a mist separator or the like and reused as supply water.

For example hydration reaction of interest in a normal fine enriched uranium trioxide _{(UO 3 → UO 3 · 2H} 2 O) is the exothermic reaction desired dihydrate 93% or more, more preferably obtain a product of more than 95% It is preferable that the temperature is 30 to 55 ° C., preferably 40 to 50 ° C. for 1 to 5 hours, preferably 1 to 2 hours. In order to carry out the reaction at such an appropriate processing temperature for an appropriate time, the present invention is used. The device preferably has a jacket covering at least part of its bottom, side walls and end walls, in particular the bottom and side walls, for passing a heat transfer fluid for heating or cooling.

In addition, the temperature of the heat medium for maintaining an appropriate temperature often varies depending on the degree of progress of the reaction and the degree of addition of water over the direction of the rotation axis. It is preferable that the jacket is divided over the sections and a heating medium having an appropriate temperature is flown into each section to individually control the temperature of the object to be treated in each section.

As shown in FIG. 2, the heat medium is usually flown in the direction orthogonal to the direction in which the uranium trioxide to be processed is sent. Further, for example, in the case of slightly enriched uranium trioxide represented by reprocessing and recovered uranium trioxide, good results are obtained when the particle size of the material supplied as a raw material is less than 500 μm (micrometer), preferably 100 to 200 μm. It is preferable to supply a raw material for an object to be treated having an appropriate particle size according to the object to be treated.

FIG. 3 is a conceptual explanatory view of an example of the apparatus according to the present invention.
Is a plan view, b is a side view, and c is a cross-sectional view. In this example of the 4-axis type, two raw material supply ducts 1 to 2 on each of the left and right sides are provided.
Through two inlets 3 located exactly in the middle of the shaft, evenly and continuously near the inlet side end of the container 100 composed of both end walls 5, both end walls 7, an upper wall 11 as a lid, and a bottom 65. The to-be-processed powder that has been quantitatively charged is continuously stirred from a water supply device (not shown) provided on the lid and is stirred by the rotation of the stirring blade 19 along with the rotation of the rotating shaft 15 together with the water that is sprayed quantitatively. While hydrating, it gradually moves toward the outlet 99, passes through the weir 97, and is discharged from the outlet 99.

The stirring blade 19 is fixed to the shaft 15 by the arm 17 so that its angle can be changed by rotating the arm about the arm. Although only one stirring blade is shown in the figure c for the sake of simplicity, a plurality of stirring blades having the same shape are usually arranged spirally along each axis at the same pitch, and the angles are not necessarily the same.

The outermost circumferences 21 drawn by the rotation of the stirring blades attached to the adjacent shafts overlap each other as shown in Fig. C, so that the positions of the stirring blades on the adjacent shafts do not normally match in the axial direction. Arranged. Even if they coincide with each other, it is possible to prevent them from contacting each other by synchronizing the rotations of the adjacent shafts and adjusting the phases of the stirring blades on the adjacent shafts.

Each stirring blade draws the annular space 23 shown in FIG. Between the outermost circumference 21 drawn by the rotation of the stirring blade and the bottom 65 having a corrugated cross section is usually 0.3 mm to 5.0 mm, preferably 1.
The clearance of 5 to 3.5 mm prevents the powder to be treated from depositing on the bottom.

The outermost circle overlaps 10 to 50 of the radius of the adjacent circles.
%, Preferably 15-45% overlap. It is typically 20-40%. Such an overlap effectively acts on the above-described swinging stirring.

The lid 11 is divided into an appropriate number for the convenience of production, assembly, maintenance, etc., and is configured as one set of the division upper wall 9. It is convenient to have a window 13 made of a transparent material such as vinyl chloride resin or glass with a wire mesh in a part of the section lid 9.

A jacket 25 is provided so as to cover the entire surface of the bottom 65, both side walls 7 and almost the entire end wall on the inlet side. In order to further enhance the heat transfer effect, the upper wall portion may have the same shape as the bottom 65 having a corrugated cross section, and a jacket may be provided on the bottom wall 65 (third portion).
Figure d). The jacket is divided along the axis of rotation as required and is constructed as a set of compartments 27. The axial length of the compartment 27 may be arbitrary as required. A baffle 63 is provided on the jacket as needed to enhance heat transfer.

Both end walls 5, both side walls 7, and upper wall 1 which constitute the container 100
It is needless to say that the 1 and the bottom 65 and the like are not necessarily mutually independent members, and any two or more of them may be at least partially combined and integrated. Items other than the upper wall may be divided and combined in an appropriate number as required.

The number of rotating shafts is 8 to 10 in an ordinary device, but there is no particular limitation. Rather than increasing the processing capacity only by increasing the number of axes per unit, it may be convenient to parallelize the devices with an appropriate number of axes because the processing capacity can be adjusted depending on the number of operating units.

When this device is arranged in a stepwise manner and is connected in series because the time required for completion of the desired hydration is long, etc., the container 200 of the second and subsequent stages, part of which is indicated by a broken line in FIG. The inlet 103 has the same shape as the outlet 99 of the container in the previous stage (a rectangular shape is typical), which is convenient in terms of design, manufacture, connection, and the like.

FIG. 4 shows a conceptual diagram in the case where a large number of cells are connected in a stepwise manner. The arrow indicates the direction in which the object to be processed is sent.

For example, in the case of slightly enriched uranium trioxide with a uranium enrichment of less than 1.6%, considering the criticality control, if the maximum distance from the top of the inner surface of the lid to the bottom of the inner surface of the bottom is 276 mm, the criticality will be achieved even if the operation of the equipment is stopped. It is preferable because there is no fear of reaching a state. Similarly, the upper limit of this distance is determined according to the uranium trioxide powder to be processed that requires criticality control.

When it is preferable to use a horizontal arrangement instead of the stepwise arrangement in view of criticality control for keeping the distance below 276 mm, for example, the inner surface of the bottom 65 in the space (outlet chamber) 101 between the weir 97 and the outlet side end wall 101 Provide a bottom not lower than this, and provide an outlet on the side wall on the lower end side by sloping in the left and right direction from the inlet to the outlet direction, or in addition to the bottom of the outlet chamber, a screw conveyor, air or other suitable An outlet may be provided on at least one of the side walls of the outlet chamber by attaching or not attaching an appropriate conveying means such as fluidizing means due to various vibrations, and may be connected to the inlet of the next-stage device.

FIG. 7a (rectangular wave type) shows the arrangement of the individual device units in the present invention when a large number of devices of the present invention of the same size are connected and arranged in series at the same height. ), B (oblique type) or a combination thereof. The arrow indicates the flow of the object to be processed.

An example of such a connection will be described with reference to FIG. For the sake of simplicity, the bottoms of the container 100 at the front stage and the container 200 at the rear stage are drawn in a plane shape and shown without the lid, the rotary shaft, the stirring blade, and the like. Container 10
The object to be processed, which has been sent to the weir 97 in the direction of arrow A in 0, enters the exit chamber 101 over the weir, moves in the direction of arrow B by gravity along the inclination of the bottom 102, and coincides with the exit 99 of the container 100. Container 200
It enters the container 200 through the inlet 103 and moves in the direction of arrow C.

The weir 97 and the end wall 205 of the container 200 do not need to be integrated, but are substantially aligned and continuous. The end wall 105 of the container 100 has a shape in which a portion of the weir 97 above the bottom 102 is extended to the same height as both side walls.

FIG. 5 shows an example of an 8-axis type, a is a lateral cross-sectional view, and b is a conceptual side cross-sectional view mainly explaining the axial blade arrangement. This device has eight rotating shafts 15 which are attached to respective rotating shafts 15 by arms 17 in a variable angle and which have a large number of stirring blades 19 having a rotating outermost radius of 62.5 mm.

The clearance between the corrugated bottom 65 and the outermost circumference of rotation is 2.4 mm.

On each shaft, 14 stirring blades are installed at 70 mm intervals and 90 degree angle deviation.

The height of the upright side wall 7 is 160 mm, the distance between the central axes of adjacent shafts is 95 mm, and the distance between the axial center of both ends and the inner surface of the end wall is 64.9.
mm.

Corresponding stirring blades on adjacent shafts have the same axial position, but do not come into contact during operation because the rotation of each shaft is synchronized and the phases of the blades are different.

In FIG. 2B, the object to be processed entered from the inlet 3 is initially sent to the left by the screw feeder 300, is swung by the stirring blade 19 attached to the rotary shaft 15 via the arm 17, and is moved to the left while reacting. The upper end passes over the weir 97, which is 50 mm lower than the upper end of the side wall, and is discharged from the outlet 99.

FIG. 6 is a schematic view of an example of a system using the device according to the present invention. Reference numerals common to those in FIG. 1 indicate the same things.

From the hopper 29, a fixed amount supply device 31 such as a snake pump and a rotary valve 31 and then through a number of lines 1 via a uniform distribution device (not shown) and the same number of inlets into the container 100. In this figure, through a line 35 through a constant amount supply device 36 such as a control valve or a constant amount pump, a spray 37 provided at four places on the upper wall in the moving direction of the powder to be treated, at least in the vicinity of the inlet 3 into the container. While being hydrated, it is agitated by the agitating blades 19 fixed to the shaft 15 driven by the power source 43 which is a combination of, for example, a motor, a transmission or a speed reducer, and a coupling together with the pure water sprayed on. Take Exit 99.

The product exiting the outlet 99 may be sent to the product tank after optionally passing through an intermediate tank with or without a stirring device, a hopper, a classifier, a crusher, or the like.

Although an equal amount of pure water is usually sprayed from each spray 37, a different spray amount may be used for each spray if necessary. The individual sprays on the drawing are appropriately branched or expanded in the depth direction of FIG. 2 as needed, so that water is evenly distributed in the same direction.

Cooling water 39 or warm water 41 is appropriately flowed in a jacket (not shown) as a heat medium in a direction orthogonal to the object to be processed to keep the temperature of the object to be processed within an appropriate range. Since the hydration of uranium trioxide is an exothermic reaction, if heating is appropriately started at the start of the treatment to start the reaction, heat generation / heat radiation is balanced, and subsequent heating or cooling may not be necessary. is there.

One exhaust port 45 is provided near the inlet and one at the outlet, and the exhaust gas that exits here is collected from line 47 to line 49, and is filtered.
51 or bypass filter 53 and then mist separator 57
It is discharged through the attached condenser 55 and the HEPA filter (not shown). The water condensed by the condenser 55 can be stored in the tank 61 and reused as an auxiliary material.

The purpose is achieved if 93% by weight or more, preferably 95% by weight or more of the starting uranium trioxide is obtained. Since the dihydrate is dehydrated to some extent during the treatment, the balance of uranium trioxide has an average composition of about 0.8 hydrate.

No. 2 of Table 1 shows the general design specifications of the apparatus of the present invention suitable for treating slightly enriched uranium trioxide. No. 1 is a comparative example.

When the slightly concentrated uranium trioxide was treated in the No. 2 8-axis reactor of Table 1, the results of Table 2 were obtained. Note that N in Table 2
The product obtained by operating the No. 1 twin-screw reactor of Table 1 corresponding to No. 2 of Table 2 with the same raw material for o. In addition to doubling the yield of UO ₃ −2H ₂ O 9
The yield was 4% and the fluorination yield was 96%. Moreover, the yield of UO ₃ −2H ₂ O is about 90% when the same raw material is used for the No. 1 in Table 2 at the same temperature for 1.5 hours by the batch method.

[Effects of the Invention] As is apparent from the above, the following effects can be obtained by the present invention.

・ Continuous hydration of powder to be treated is possible.

・ High reactivity during fluorination of the target product.

-High yield of desired product.

・ Easy to adjust the reaction time.

-It is easy to scale up the processing capacity by arranging multiple devices in parallel or in series.

・ Temperature control is easy if a proper jacket is provided.

-Because the layer thickness of the substance to be treated in the equipment can be reliably kept to a certain value or less, radioactive substances that require criticality control can be easily critically controlled even for the object to be treated.

・ Scaling up considering criticality control when handling radioactive objects requiring criticality control can be easily done by simply combining multiple equipment units. For example, if about 10 8-axis type devices of the present invention that require spaces of 795 mm, 1255 mm, and 276 mm in length, width, and height, respectively, are combined, 400 kg-U / H
The above uranium trioxide hydration treatment on a commercial scale is possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1, FIG. 3, and FIG. 5 are explanatory views of an example of the apparatus according to the present invention, and FIG. 2 is an explanatory view of temperature control in the apparatus of the present invention, and FIG. Is an explanatory view of an example of a system using the device according to the present invention, and FIGS. 4, 7, and 8 are explanatory views of the serial arrangement of the devices according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Matsushima 4-10-25 Shinmori, Asahi-ku, Osaka-shi, Osaka (72) Inventor Nobuhisa Okuyama 7-13-29 Katsutadai, Yachiyo-shi, Chiba (72) Inventor Katsumi Hoshi 5-15-1-502 Isobe, Chiba City, Chiba Prefecture (72) Inventor Tasuke Fujisawa 2-7-9-301 Takasu, Chiba City Chiba Prefecture (56) Reference Japanese Patent Laid-Open No. 1-246147 (JP, A) Kaihei 1-160831 (JP, A)

Claims (7)

(57) [Claims] 1. An apparatus for continuously activating and chemically activating uranium trioxide powder: having three or more central axes on substantially the same horizontal plane parallel to the traveling direction of the object to be treated. It has a rotation axis; agitation provided along each axis so that its main plane (blade plane) rotates at an inclination with respect to a plane (rotation plane) perpendicular to the rotation axis. Has blades; the areas covered by the rotation of the stirring blades on adjacent shafts partially overlap each other when viewed from the axial direction, but each stirring blade contacts the adjacent shaft and the stirring blades on that shaft. A non-stirring blade arrangement; a bottom parallel to the axis of rotation, a side wall, and an upper wall, and end walls located at both ends thereof, one end of an object to be treated and the other end an outlet of an object to be treated This container has a container having an inner end near the outlet end, which is farther from the outlet end wall than the outlet and has an upper end. It has a weir that is lower than the inner surface of the wall; the inner surface of the bottom is a cross section of a surface perpendicular to the axis of rotation with a radius slightly larger than the circle formed by the outermost circumference of rotation of each stirring blade and with arcs concentric with this circle. A device having at least one water supply device and an exhaust port, respectively. 2. A temperature control is provided by covering at least a part of the bottom, the side wall, the end wall, and the upper wall, and having a jacket through which a heating medium fluid for heating or cooling is passed to perform heating and cooling. The apparatus according to item 1. 3. The device according to claim 1, wherein a plurality of units are connected in series. 4. A device according to claim 3, wherein the connection is made horizontally. 5. The apparatus according to claim 1, 2, 3 or 4, wherein the distance from the uppermost portion of the inner surface of the lid to the lowermost portion of the inner surface of the bottom is 276 mm at maximum, in consideration of criticality control of nuclear fuel material. 6. The object powder is fed from the inlet of the apparatus according to claim 1, 2, 3, 4, or 5, and the water is fed from the water supply apparatus, wherein each rotating shaft is rotated and the stirring blade is operated. A method of chemically activating the powder to be treated by hydrating the powder to be treated, which is supplied quantitatively, and the powder of the substance to be processed which has passed through the weir and reaches the outlet is taken out from the outlet. 7. The method according to claim 6, wherein the object to be treated is treated at a temperature of 30 to 55 ° C. for 1 to 5 hours.