JPH0218328A - Method and device for continuous chemical activation of uranium trioxide powder - Google Patents

Abstract

PURPOSE:To continuously and efficiently activate UO3 by hydration by supplying the UO3 powder to a device which has many pieces of revolving shafts parallel with a progressing direction and agitating vanes, etc., arrayed and provided on said shafts and is provided with a water supplying device. CONSTITUTION:The UO3 powder supplied 3 at a constant rate to the above- mentioned device is oscillated and agitated randomly longitudinally (in the shaft 15 direction) and vertically and transversely (in the direction perpendicular to the shaft 15) together with the supplied water by means of the many agitating vanes 19. The powder is moved from an inlet 3 to an outlet 99 while making hydration reaction in this way and is activated. The activated powder is dis charged as the product UO3.2H2O. The shafts 15 provided with usually 4-10 pieces, more particularly 4-9 pieces are effective. The supply rate of the water necessary for the hydration is 1-1.5 times the necessary equiv. and the pure water refined by ion exchange or distillation, etc., is usually used. The above- mentioned hydration reaction is exothermic reaction and the powder is required to be treated under the conditions of 30-55 deg.C and 1-5 hours in order to obtain the product of >=93%, more preferably >=95% dihydride.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus and method for chemically activating powdered uranium oxide such as reprocessed recovered uranium (slightly enriched UO5). More specifically, the present invention relates to an apparatus and method for chemically activating the same substance through hydration.

[Prior Art and Problems to be Solved by the Invention] When chemically treating a powdery substance in an industrial setting, it is sometimes preferable to carry out an appropriate pretreatment so that the chemical treatment can be carried out satisfactorily. One of these is pretreatment by hydration when denitrified uranium trioxide is subjected to fluoridation treatment to produce uranium hexafluoride. For example, in the case of reprocessed recovered uranium (slightly enriched UO3), this is heated to 300°C. However, when it is added to water, the specific surface area increases, but the HP fluorination reactivity is rather low (and it requires time and effort such as re-drying). - It has been confirmed that the method of spraying water onto uranium dioxide being fluidized in a force-driven bed destroys the normal fluidization state due to powder agglomeration and does not allow hydration to proceed.

As a result of our investigation, we found that if we mechanically stirred uranium trioxide while keeping it in powder form and then added water dropwise from the top to perform the hydration process in batches, the hydration yield increased, but the HP fluorination It was confirmed that the reactivity was also high.

However, with this batch method, it is difficult to make it continuous, and if more than a certain amount of nuclear fission occurs, chain fission reactions will occur, which is extremely undesirable. Particularly in the case of chemical substances, it is necessary to increase the capacity of batch-type processing equipment when it is desired to process large quantities commercially, which is not practical. This is also not realistic from an economic standpoint.

The present invention aims to solve the problems of the above-mentioned conventional techniques.

[Means and effects for solving the problems] The present invention was finally achieved after the inventor conducted intensive studies to overcome the above problems.

That is, the present invention is: An apparatus for continuously processing and chemically activating uranium trioxide powder. It has a shaft; it has stirring blades arranged side by side on each axis; the range covered by the rotation of the stirring blades on adjacent shafts partially overlaps each other when viewed from the axial direction. However, each stirring blade has a stirring blade arrangement that does not come into contact with adjacent shafts and stirring blades on the shaft; a bottom, side wall, and top wall parallel to the rotation axis, and end walls located at both ends of these. Consisting of The container has an inlet for the material to be processed at one end and an outlet for the material to be processed at the other end. It has a weir lower than the inner surface; the inner surface of the bottom has a cross section that is perpendicular to the axis of rotation and is lined with arcs that have a radius slightly larger than the circle formed by the outermost rotational circumference of each stirring blade and are concentric with this circle. The powder to be treated is extracted from the apparatuses each having one or more water supply apparatuses and one or more exhaust ports, and the above apparatuses in which each rotating shaft rotates and the stirring blades are operated, and from the water supply apparatus. The present invention provides a method for chemically activating powder to be treated by hydration, in which water is supplied quantitatively to each of the two, and the powder to be treated that has crossed the weir and reached the outlet is taken out from the outlet.

Substances such as uranium trioxide, whose chemical reactivity improves through hydration, undergo a hydration reaction with water in a solid-liquid heterophasic system, but if they are reacted in a slurry or paste form containing a lot of water, they will dry out afterward and become powdery. Therefore, it is desirable that the powder to be treated is mixed with the required amount of water as a powder to achieve the desired hydration. It has been found that the above-described apparatus and method are suitable for meeting this condition and solving the above-mentioned problems. The device of the present invention can be said to be a type of mixer or feeder used for mixing or feeding powder or granular materials, and it has the above-mentioned configuration with a water supply device and an exhaust port, so that chemical It was not until the present inventor discovered that desirable results can be obtained by continuously treating uranium trioxide, which improves 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: schematic perspective view, b: conceptual sectional view).

C: Conceptual side view), and the third detailed explanation of the present invention.
To begin with, a conceptual side view of the figure shows the rotation axis 15.
are rotated and the stirring blades (paddles) 19 are operated, so that at least 1 per 2 rotating shafts is generated in the container 100.
The powder to be processed, which is evenly distributed and quantitatively supplied from the supply ports (not shown), is hit by the stirring blades, and does not accumulate or agglomerate unnecessarily on the bottom. ) It is shaken and stirred at random along with water in the vertical and horizontal directions (direction perpendicular to the axis), and moves from the population 3 to the exit 99 and is discharged while performing a hydration reaction.

It can be said that the purpose of continuous rotation can be achieved if there are two rotation axes, but since there is a limit to the practical axis length, the processing capacity is not sufficient for practical purposes, so it is necessary to have two rotation axes. The present inventor has discovered that it is necessary to synergistically improve processing capacity not only in terms of throughput but also in terms of product quality by providing an axis.

The term "multi-axis" in the present invention refers to three or more rotation axes, but usually preferably 4 to 10, more preferably 4 to 10.
The one provided with 8 pieces is easy to put into practice and effective.

In general, it is preferable to use an even number of rotating shafts in order to prevent vibrations during operation.

The stirring blade usually has a fan-shaped or arcuate main plane (blade plane), and is fixed to a shaft so that the curved part rotates slightly away from the curved surface of the bottom of the container. The object to be processed is pushed by rotation not parallel to the perpendicular plane (plane of rotation) but at an angle of more than 0 degrees and less than 180 degrees. For convenience, when this side of the rotating blade faces the population end, it is 0 degrees, and when it faces the outlet end, it is 1 degree.
Set it to 80 degrees.

The inclination of the individual stirring blades may be determined by the direction in which the workpiece is pushed in the direction of the rotating shaft by the movement of the stirring blades (and also between the individual stirring blades or between groups of stirring blades on the rotating shaft). Rather than keeping the inclinations or their directions fixedly the same or fixedly different, it is preferable to be able to select and change any combination depending on the required degree of reaction and residence time of the object to be treated.

In order to facilitate such changes, the stirring blade may be fixed to the rotating shaft by means of screws or the like via a suitable arm, typically a round bar. The plane of the blade may not be a perfect plane, but may be a convex or concave surface, but from the same point of view, it is better to be able to arbitrarily change the angle with respect to the rotating surface.

It is preferable that the rotational directions of the respective rotational axes do not necessarily have to be the same between the axes, and can be arbitrarily changed according to processing needs. If the inclination and direction of rotation of the stirring blades are made variable as described above, it is more convenient to adjust the degree of stirring and feed speed in a more diverse manner than by simply changing the number of rotations. By appropriately selecting the degree of stirring and feeding speed, processing can be completed in the shortest time depending on the object to be processed.

In addition, in the apparatus of the present invention, even if the stirring blades are all rotated to push the object to be processed from the outlet toward the surface of the blade, the powder of the object to be processed is fluidized by stirring, so The amount corresponding to the supply is hydrated and sent to the weir, crossed the weir, and taken out from the outlet.

The water supply device is used in an amount necessary for hydrating the material to be treated, or slightly in excess, that is, 1 to 1.5 times the required equivalent amount, preferably 1.1 to 1
．． Three times the amount of water is supplied to the object to be treated from one place on the upper wall or from a plurality of appropriately divided points by an appropriate method such as spraying or a dripping ring according to the supply of the object to be treated.

The supply from the inlet of the material to be treated is preferably and generally carried out quantitatively, and the same applies to the supply of water. The water used is usually pure water purified by ion exchange or distillation.

It is preferable that the water vapor that may be generated as a result of stirring and mixing the material to be treated and water is led out of the apparatus from the exhaust port and released through a suitable filter to remove particles of the material to be treated. It is also possible to collect water using a condenser, mist separator, etc. before releasing it and use it again as supply water.

For example, in ordinary slightly enriched uranium trioxide, the target hydration reaction (UO1→U03・2H20) is an exothermic reaction, and to obtain a product with a desired dihydrate content of 93% or more, more preferably 95% or more, the temperature is 30%. to 55°C, preferably 40°C
to 50°C for 1 to 5 hours, preferably 1 to 2 hours.
In order to carry out the reaction for a suitable time at such a suitable processing temperature, the apparatus of the present invention has a structure in which the bottom, side walls, and end walls are partially covered. It is preferable to have a jacket through which a heat transfer fluid for heating or cooling is passed.

In addition, the temperature of the heating medium to maintain the appropriate temperature often varies in the direction of the rotational axis depending on the degree of progress of the reaction and the degree of water addition, so in such cases, an appropriate number of two or more heat mediums are used in this direction. It is preferable to divide the jacket over the area and flow a heating medium at an appropriate temperature to each zone to individually adjust the temperature of the object to be treated in each zone.

The heating medium is normally flowed in a direction perpendicular to the direction in which the uranium trioxide to be treated is sent, as shown in FIG. For example, with slightly enriched uranium trioxide, typified by reprocessed recovered uranium trioxide, good results can be obtained when the particle size of the material supplied as a raw material is less than 500 μm (micrometer), preferably 100 to 200 μm. Preferable results can be obtained by supplying raw material for the object to be processed with an appropriate particle size depending on the object to be processed.

FIG. 3 is a conceptual explanatory diagram of one example of the device according to the present invention, in which a is a plan view, b is a side view, and C is a cross-sectional view. In this example of a 4-shaft type, there are two raw material supply ducts (1), through two inlets 3 located exactly between the two shafts on both the left and right sides, and evenly distributed to both end walls 5, both side walls 7, and the top which is the lid. The powder to be treated is continuously and quantitatively introduced into the vicinity of the inlet end of the container 100, which is composed of the wall 11 and the bottom 65, from a water supply device (not shown) provided on the lid. The rotating shaft 15 along with the water being sprayed
The mixture is stirred by the rotation of the stirring blade 19 as the stirring blade 19 rotates to 0, gradually moves toward the outlet 99 while undergoing a hydration reaction, crosses the weir 97, and is discharged from the outlet 99.

The stirring blade 19 is fixed to the shaft 15 by an arm 17 so that its angle can be changed by rotating around the arm. For the sake of simplicity, only one stirring blade is shown in Figure C, but a plurality of stirring blades with the same shape are usually arranged spirally at the same pitch along each axis, but not necessarily at the same angle.

The outermost circles 21 drawn by the rotation of the stirring blades attached to adjacent shafts overlap each other as shown in Figure C, so the stirring blades on adjacent shafts are arranged so that their positions do not normally coincide in the axial direction. be done.

Even if they match, it is possible to prevent them from coming into contact by synchronizing the rotations of adjacent shafts and adjusting the phases of stirring blades on adjacent shafts.

Each stirring blade draws an annular space 23 shown in figure b. The distance between the outermost circumference 21 drawn by the rotation of the stirring blade and the bottom 65 forming a wave-shaped cross section is usually 0.3 mm to 5.0 mm.
, preferably a clearance of 1.5 to 3.5 mm to prevent the powder to be treated from accumulating on the bottom.

The overlap of the outermost circles above is 10 to 50 times the radius of the adjacent circles.
%, preferably 15-45%. Typically it is 20-40%. Such overlap effectively acts on the above-mentioned oscillating stirring.

The lid 11 is divided into an appropriate number of sections for ease of manufacture, assembly, maintenance, etc., and is constructed by placing one set on top of the sectioned upper wall 9. Conveniently, a portion of the compartment lid 9 has a window 13 made of a transparent material such as vinyl chloride resin or wire mesh glass.

A jacket 25 is provided to cover the entire surface of the bottom 65, almost the entire surface of both side walls 7 and the end wall on the entrance side. Further, in order to further improve the heat transfer effect, the upper wall portion can be made in the same shape as the bottom 65 which has a wave-shaped cross section, and a jacket can be provided on this (
Figure 3 d). The jacket is divided as necessary in the direction of the rotation axis and is configured as a set of sections 27. Section 27
The axial length of can be set arbitrarily as required. A baffle 63 is provided in the jacket as necessary to enhance heat transfer.

Note that both end walls 5, both side walls 7, and top wall 1 that constitute the container 100
1, the bottom 65, etc., are not necessarily independent members, and two or more of them may of course be integrated at least partially. Also, parts other than the upper wall may be divided into an appropriate number of parts and combined as required.

The upper limit for the number of rotating shafts in a normal device is 8 to 10, but there is no particular restriction. Rather than increasing the processing capacity simply by increasing the number of axes per unit, it may be more convenient to arrange devices with an appropriate number of axes in parallel, since the processing capacity can be adjusted depending on the number of operating units.

When arranging this device in a stepwise manner and connecting them in series because it takes a long time to complete the desired hydration, the containers 200 in the second and subsequent stages, some of which are indicated by broken lines in Figure b, Entrance 10
3 has the same shape as the outlet 99 of the previous container (typically rectangular) from the viewpoint of design, manufacture, connection, etc.

FIG. 4 shows a conceptual diagram when a large number of devices are arranged in series 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 criticality control, if the distance from the top of the inside of the lid to the bottom of the inside of the bottom is a maximum of 276 mm, even if the equipment stops operating. It is also preferable because there is no risk of reaching a critical state. The upper limit of this distance is similarly determined depending on the uranium trioxide powder to be processed which requires criticality control.

If a horizontal arrangement is preferred instead of the stepped arrangement from the viewpoint of criticality control to keep the distance at 276 mm or less,
For example, the space (exit chamber) 101 between the weir 97 and the outlet side end wall
Provide a bottom that is not lower than the inner surface of the bottom 65, and provide an outlet on the side wall of the lower end with a horizontal slope from the inlet toward the outlet, or a screw in addition to the bottom of the outlet chamber. An outlet may be provided on at least one of the side walls of the outlet chamber and connected to the inlet of the next stage apparatus, with or without an appropriate withdrawal means such as a conveyor, fluidization means using air or suitable vibration.

When a large number of devices of the present invention, usually of the same size, are connected and arranged in series at the same height, the arrangement of the individual device units of the present invention is shown in FIG. 7a (rectangular wave type). ),
b (oblique type) or a combination of these. Arrows indicate the flow of objects to be processed.

An example of such a connection will be explained in FIG. For the sake of simplicity, the bottoms of the first container 100 and the second container 200 are drawn flat, and the lids, rotating shafts, stirring blades, etc. are removed. The material to be processed is sent to the weir 97 in the direction of the arrow in the container 100, crosses the weir, enters the outlet chamber 101, moves in the direction of the arrow B along the slope of the bottom 102 by gravity, and reaches the outlet 99 of the container 100.
It enters the container 200 from the entrance 103 of the container 200, which coincides with the direction of the arrow C, and moves in the direction of the arrow C.

The weir 97 and the end wall 205 of the container 200 do not need to be integral, but are substantially aligned. Further, 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-shaft type, in which a is a cross-sectional view and b is a conceptual side sectional view mainly explaining the blade arrangement in the axial direction.

This device has eight rotating shafts 15 each having a variable angle attached to each rotating shaft 15 by an arm 17 and having a large number of stirring blades 19 each having an outermost rotation radius of 62.5 mm.

The clearance between the corrugated bottom 65 and the outermost rotational circumference is 'l, 4
It is mm.

Stirring blades are placed at 70mm intervals on each axis, with an angular deviation of 90 degrees.
4 pieces can be installed.

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

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

In Figure b, the workpiece that entered the apparatus from the inlet 3 was initially sent to the left by the screw feeder 300 and then transferred to the rotating shaft 1 via the arm 17.
The liquid is oscillated and stirred by the stirring blade 19 attached to the wall 5, moves to the left while reacting, crosses the weir 97 whose upper end is 50 mm lower than the upper end of the side wall, and is discharged from the outlet 99.

FIG. 6 is a schematic diagram 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.

The raw powder to be processed enters the container 100 from the same number of inlets via a large number of lines 1 via a quantitative supply device 31 such as a snake pump or a rotary valve from a hopper 29, and an equal distribution device (not shown). In this figure, the spray 37 provided at four locations on the upper wall in the direction of movement of the powder to be treated, at least near the population 3, passes through a constant pot supply device 36 such as a control valve or a metering pump, and is supplied to the container via a line 35. For example, the motor and transmission or reducer, together with the pure water sprayed inside.
The water is stirred by a stirring blade 19 fixed to a shaft 15 driven by a power source 43 which is a combination of a coupling and a power source 43, and reaches the outlet 99 while being hydrated.

The product exiting the outlet 99 may pass through an intermediate tank or hopper with or without an agitator, a classifier, a crusher, etc., as required, before being sent to the product tank.

An equal amount of pure water is normally sprayed from each spray 37, but the amount may be different for each spray if necessary. The individual sprays shown in the figure are branched or expanded as necessary in the depth direction of FIG. 2, so that the water is evenly distributed in the same direction.

Cooling water 39 or hot water 41 is appropriately passed through the jacket (not shown) as a heating medium in a direction perpendicular to the object to be treated to maintain the temperature of the object to be treated within an appropriate range. Since hydration of uranium trioxide is an exothermic reaction, if the reaction is initiated by appropriate heating at the beginning of the process, the heat generation/heat release will be balanced and subsequent heating or addition/removal may be unnecessary. .

One exhaust port 45 is provided in the vicinity of the inlet and the outlet, and the exhaust gas exiting the outlet is collected from line 47 to line 49, passes through filter 51 or bypass filter 53, and is connected to condenser 55 with mist separator 57 and II3PA (not shown).
Released via filter. Water condensed in the condenser 55 can be stored in a tank 61 and reused as an auxiliary raw material.

The objective is achieved if a dihydrate containing 93% by weight or more, preferably 95% by weight or more of the raw material uranium trioxide is obtained. Since the dihydrate is dehydrated to some extent during processing, the remaining uranium trioxide has an average composition of about 0.8 hydrate.

The general design specifications of the apparatus of the present invention suitable for processing slightly enriched uranium dioxide are shown in Nα2 in Table 1. Nα1 is a comparative example.

The results shown in Table 2 were obtained when slightly enriched uranium trioxide was treated in the 8-shaft reactor No. 2 in Table 1. Furthermore, Table 2
For No. 1, the product obtained by operating the twin-screw reactor with Nα1 in Table 1 corresponding to N052 in Table 2 using the same raw materials, the amount obtained per hour was only 3740 times. The yield of Ro03-2H20 was 94% and the yield of fluorination was 96%. In addition, for No. 1 in Table 2, UO, -2 when treated with the same raw materials at the same temperature for 1.5 hours by batch method.
) 1.0 yield is about 90%.

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

The powder to be treated can be continuously hydrated.

High reactivity during fluorination treatment of target product.

High yield of target product.

Easy to adjust reaction time.

Processing capacity can be easily scaled up by arranging multiple devices in parallel or in series.

Temperature control is easy with a suitable jacket.

Since the layer thickness of the material to be processed within the apparatus can be reliably kept below a certain value, criticality control of radioactive substances that require criticality control can be easily carried out in the material to be processed.

When dealing with radioactive materials that require criticality control, scale-up with consideration to criticality control can be easily achieved by simply combining a plurality of equipment units. For example, the length, width, and height are respectively 795mm, 1255mm, and 276mm in the inner measurement.
By combining about 10 eight-shaft devices of the present invention, which require a certain amount of space, it is possible to perform hydration treatment of uranium trioxide on a commercial scale of 400 kg-U/H or more.

[Brief explanation of drawings]

Figures 1, 3, and 5 are explanatory diagrams of examples of the apparatus according to the present invention, Figure 2 is an explanatory diagram of temperature control in the apparatus according to the present invention, and Figure 6 is an illustration of the apparatus according to the present invention. FIG. 4, FIG. 7, and FIG. 8 are explanatory diagrams of an example of a system using the system, and FIGS. 4, 7, and 8 are explanatory diagrams of a series arrangement of devices according to the present invention.

Claims (1)

[Claims] 1. An apparatus for continuously processing and chemically activating uranium trioxide powder: A number of central axes are arranged on substantially the same horizontal plane parallel to the direction of movement of the object to be processed. It has a rotating shaft; It has stirring blades arranged in parallel on each axis along each axis; The range covered by the rotation of the stirring blades on adjacent shafts partially overlaps each other when viewed from the axial direction. However, each stirring blade has a stirring blade arrangement that does not come into contact with adjacent shafts and stirring blades on that shaft, and has a bottom, side wall, and top wall parallel to the rotation axis, and ends located at both ends of these. a container having a wall having an inlet for a material to be treated at one end and an outlet for a material to be treated at the other end; has a lower weir than the inner surface of the top wall; the inner surface of the bottom has a radius slightly larger than the circle formed by the outermost rotational periphery of each stirring blade, and an arc perpendicular to the rotational axis that is concentric with this circle is arranged. A device having a cross-section by a plane; each having one or more water supply devices and one or more exhaust ports. 2. A jacket according to claim 1, which has a jacket that covers at least a portion of the bottom, side walls, end walls, and top wall and allows the passage of a heating medium fluid for heating or cooling, so that the temperature can be controlled by heating and cooling. Device. 3. The device according to claim 1 or 2, wherein a plurality of devices are connected in series. 4. Apparatus according to claim 3, wherein the connection is made horizontally. 5. The device according to claim 1, 2, 3 or 4, which takes into consideration the criticality control of nuclear fuel material, and the distance from the top of the inner surface of the lid to the lowest part of the inner surface of the bottom is at most 276 mm. 6. The apparatus according to claim 1, 2, 3, 4 or 5, wherein each rotating shaft rotates and the stirring blade operates, quantitatively supplies the powder to be treated from the inlet and water from the water supply device. A method of chemically activating the powder to be treated by hydration, in which the powder to be treated is supplied and taken out from the outlet after crossing the weir and reaching 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.