JPH02257099A - Device for kneading cement for solidification treatment of radioactive waste - Google Patents

Abstract

PURPOSE:To allow the continuous kneading of water and cement for a solidifying material by continuously kneading the cement for a solidification treatment and the water and providing a discharge means which can change an effective opening rate at one end of a kneading tank. CONSTITUTION:A prescribed amt. of the cement for the solidifying material is charged from a cement silo 1 into a measuring tank 3. The charged cement for the solidifying material is sent to a cement feeder 6. This cement feeder 6 supplies the cement for the solidifying material at a prescribed rate per unit time to the kneading device 9 by a controller 7 for the rotating speed of the cement feeder. The deviation signal based on the difference between the prescribed supply rate and the actual supply rate determined by the computation of a change rate in the weight is impressed to the controller 7 to change the rotating speed of the cement feeder by the controller 7 when the supply rate is not within the prescribed range. The supply rate is thereby so controlled as to attain the prescribed value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a part of an apparatus for solidifying radioactive waste, and more particularly to a cement kneading apparatus for solidifying treatment.

[Prior art]

Generally, radioactive waste generated at nuclear power generation facilities and the like is put into a drum can together with a solidification tank and solidified, and stored for a predetermined period of time. Cement may be used as this solidifying material. In this case, conventionally, a predetermined amount of cement powder for solidification treatment and a predetermined amount of water are kneaded, and after the kneading, the radioactive waste is poured into a drum can for assimilation treatment. In other words, batch processing is being performed.

FIG. 6 shows a schematic configuration of a kneading apparatus employing such a batch processing method.

The conventional batch processing method will be explained using FIG. 6.

The kneading machine 2o shown in FIG. 3 is connected to an input port 1a for a cement slurry 1 of cement for solidification treatment and an input port 2a for a water tank 2. This kneader 20 is provided with stirring blades 20a and a discharge valve 21. A radioactive waste processing container 1 is placed under the discharge port of this kneading machine 20.
0 is placed. In this kneading apparatus, predetermined amounts of cement and water are first introduced into the kneader 20 from the cement silo and the water tank 2, respectively. Then, the stirring blade 20a is operated for a predetermined period of time to perform kneading. The discharge valve 21 is closed when cement and water are introduced into the kneader 20 and during stirring. After the kneading is completed, the discharge valve 21 is opened and the cement slurry that has been kneaded and formed in the radioactive waste treatment container]0 is injected into the radioactive waste treatment container 10 into which the radioactive waste has been placed. In this way, radioactive waste was assimilated.

[Problem to be solved by the invention]

Although the above-mentioned conventional batch processing type kneading equipment has a comparative structure (11), since cement and water for solidification processing must be kneaded at the same time, the kneading container becomes large and radioactive waste is disposed of. The entire assimilation treatment device becomes large, and it is not preferable to use it within the limited premises of a nuclear power generation facility.

By increasing the size of the kneading container in this way,
The amount of cleaning water used to clean the cement that has hardened and adhered to the inner surface increases. This washing water is water used to remove cement slurry formed by kneading that has solidified and adhered to the inner surface of the kneading container due to a hydration reaction at room temperature, and must be treated as secondary waste. As a result, the amount of secondary waste generated also increases, and from this point of view as well, the batch processing method is not preferable.

Furthermore, as the kneading container becomes larger, if the amount of kneading is small, especially if the amount of cement slurry to be kneaded and formed is less than 1/2 of the kneading capacity of the kneading container, centrifugal force will cause the kneading container to There is a risk that the level of the cement slurry at the center of the kneading will drop and the stirring blades will be exposed from the cement slurry, resulting in insufficient kneading. In order to prevent this insufficient mixing, the amount of cement and water charged into the kneading container must always be 1/2 or more of the container capacity.

Therefore, it is not possible to increase the range of variation in the amount of kneading. On the other hand, when assimilating radioactive waste, the amount of solidifying material, such as cement slurry, to be introduced into the radioactive waste treatment container is not constant. This is because the amount of assimilation that should be put into the radioactive waste treatment container depends on the amount of radioactive waste put into the radioactive waste container and its porosity, especially after the radioactive waste has been compressed and reduced in volume. The porosity is significantly different compared to that which is not compressed and reduced in volume. As a result, even if the same radioactive waste is compressed and reduced in volume, the amount of solidification site will be significantly smaller, and in some cases is about 115 compared to the case without compression volume reduction. Therefore, the batch processing method with a small variation range as described above has a problem in that it is difficult to deal with such various cases.

In addition, as mentioned above, the fluctuation range of the capacity of the kneading container is small, so if the amount of solidification material injected into the radioactive waste container is small, the cement paste will be hydrated in the kneading container after the injection process. The reaction starts and the viscosity of the cement slurry in the kneading vessel increases. With this highly viscous cement slurry remaining in the kneading container, when the next batch of cement and water is added, either the cement paste with increased viscosity or the newly added cement and water are added. This will hinder kneading. If this batch mixing process is repeated, the remaining cement paste will continue to remain, and the hydration time (solidification time) will be different from the newly created cement slurry, making it impossible to form a uniform cement solidification in the radioactive waste container. A problem arises.

In this way, when conventional batch processing kneading equipment is used, the area occupied, the amount of radioactive waste generated, the quality of solidification processing,
There are also problems in terms of work efficiency.

Therefore, the present invention solves the above-mentioned problems, and provides a solidification process for radioactive waste that is efficient, can easily accommodate various variations in mixing capacity, and can obtain high-quality cement slurry for solidification process. The purpose of the present invention is to provide a continuous cement mixing device for use in cement production.

[Means to solve the problem]

In order to achieve the above-mentioned problems, the cement slurry kneading device for solidifying radioactive waste of the present invention has an inlet for introducing cement for solidifying radioactive waste and water, and a slurry kneading device for cement slurry for solidifying radioactive waste and water that is continuously introduced from the inlet. a kneading tank for kneading cement for assimilation and water; a stirring and kneading means for stirring and kneading the cement for solidification and water put into the kneading tank; , and a cement slurry discharge means for discharging the agitated and kneaded cement slurry for solidification treatment through it, and having a variable effective opening amount, the ratio is controlled.

Furthermore, the cement slurry discharge means is constituted by a weir,
It is preferable to discharge the cement slurry by overflowing it from the upper part.

[Effect]

The cement kneading device for solidification treatment of radioactive waste of the present invention is configured as described above, continuously kneads cement for solidification treatment and water, and changes the effective opening amount at one end of the kneading tank. By providing a discharge means that can change the liquid level of the cement slurry in the mixing tank and change the residence time of the cement slurry, it is possible to secure the desired mixing time and perform sufficient mixing. There is.

Furthermore, by configuring the discharge means as a weir and making the height of the weir adjustable, it is possible to adjust the residence time of the cement slurry in the kneading tank, and to adjust the residence time of the cement slurry in accordance with the amount of moisture, etc. in the cement slurry. This allows for proper kneading and also allows for precise control of the amount of radioactive waste to be filled into the container.

〔Example〕

Embodiments according to the present invention will be described below with reference to the drawings.

Elements with the same reference numerals have the same functions, so duplicate explanations will be omitted.

FIG. 1 shows a state in which an embodiment of the cement kneading device for assimilating radioactive waste according to the present invention is incorporated into a solidification treatment device, and FIG. 2 shows a schematic configuration of the cement kneading device for solidifying radioactive waste according to the present invention. shows.

The assimilation treatment equipment shown in Fig. 1 consists of a cement silo 1 that stores cement as a solidifying agent, a water tank 2 that stores water for mixing, a unit tank 3 that measures the amount of cement to be mixed, and a cement silo 1 that stores cement for solidification. It is composed of a device 9 and a water/cement ratio control device 5.

The cement silo 1 is located above the measuring tank 3 so that cement for solidification can be supplied into the measuring tank 3. Further, the measuring tank 3 is provided with a cement feeder 6 for feeding a predetermined amount of solidified utilization cement to the kneading device 9 from there. The cement feeder 6 is a screw-shaped rotationally driven feeder, and the supply amount can be controlled by controlling the number of rotations. A cement feeder rotation speed controller 7 for controlling the rotation speed of this cement feeder 6 is provided, and this cement feeder rotation controller 7 is controlled by a water/cement ratio control device 5. On the other hand, a water supply amount control valve 8 is provided at the supply port of the water tank 2, and this water supply amount control valve 8 is also connected to the water/cement ratio control device 5, thereby controlling the supply flow rate. This water/cement ratio control device 5 is constituted by a microcomputer.

A solidification treatment container is arranged below the discharge port of the kneading device 9.

The kneading device 9, as shown in FIG. 12a is provided. By using the rotating shaft 12a having such a shape, a propulsive force always acts on the cement formed by mixing assimilated cement and water in the direction in which the screw rotates, and never flows backward.

Further, the number of the rotating shafts 1.2a may be one or more. This supply rotating shaft 12a is connected to the retention section 1 of the kneading device 9.
3 is a stirring blade 13a that rotates and stirs the cement slurry of solidifying cement and water supplied from the supply unit 12;
is provided. The cement slurry in the retention section 13 is rotated and stirred by the stirring blades 13a, and backflow also occurs, making it possible to form a uniform cement slurry. Generally, a paddle type can be used as the stirring blade 13a. Further, this kneading device 9 has a water receptacle 14 for receiving water to be kneaded with cement for solidification from the water tank 2, and a cement receptacle 15 for receiving cement for solidification from the cement feeder 6. It is equipped with

Further, this kneading device 9 is provided with a cement slurry weir 16 in a part of the retention section 13 for supplying the cement slurry that has been kneaded into the radioactive waste treatment container 10. The cement slurry kneaded and formed in the retention section 13 overflows over the upper surface of the cement slurry weir 16 and is supplied to the radioactive waste treatment container 10. Therefore, when the height of the cement slurry weir 16 is kept constant, the same amount of cement slurry is supplied to the radioactive waste treatment container 10 as the amount supplied to the kneading device 9.

The height of the cement slurry weir 16 can be changed up and down, and by changing the height of the weir 16, the residence time of the cement slurry in the retention section 13, that is, the kneading time, is controlled. be able to. Further, by suddenly increasing the height of the cement slurry weir 16, the supply of cement slurry to the radioactive waste treatment container 10 can be stopped instantaneously. Here, the shape of this weir 16 may be flat, triangular, or square.

Further, the radioactive waste processing container 10 is provided with a liquid level detector] 8 for detecting the liquid level of the supplied cement slurry, and a liquid level control device 17. and liquid level control device 17
Based on the signal indicating that the liquid level of the cement slurry supplied by the liquid level detector 18 has reached a predetermined level, the height of the cement slurry weir 16 is changed, and the cement slurry is processed as radioactive waste. Container] Stop the injection into 0 and let it 1d.

The weighing tank 3 is provided with a weight measuring device 4 for measuring its weight. An inlet of a cement feeder 6 is connected to an outlet of this metering tank. This weight measuring device 4 measures the weight in units of 1/100th of a second and transmits the measurement results to the water/cement ratio control device 5. The water/cement ratio control device 5 calculates the change in the weight of the measuring tank 3 based on this al11 fixed result, that is, the amount of decrease in the weight of the solidifying cement in the measuring tank 3, Controlling the cement feeder 6 that controls the amount of solidifying cement supplied to the
Furthermore, the amount of water supplied from the water tank 2 is controlled.

The rate of decrease in the weight of the measuring tank 3 becomes the supply rate of the cement for solidification, and by differentiating the weight measurement signal from the weight measuring device 4, the supply rate of the cement for solidification can be determined. Then, based on the supply rate of the solidified utilization cement obtained by this differential processing, the amount of water supplied from the cement feeder rotation speed controller and the water tank to the supply section 13 of the kneading device 9 is controlled, and the assimilated cement is The mixing ratio of water and water is controlled to be constant. The reason why the weight of the weighing tank 3 is measured and controlled is that when forming cement slurry for radioactive waste solidification treatment, the mixing ratio of solidified cement and water is kept at a high level with an error of about 4 to 5%. This is because precision must be maintained. This is because the physical properties required of the solidified cement as an assimilation treatment agent, such as uniformity, compactness, and ability to contain radionuclides, are significantly affected by the mixing ratio of assimilated cement and water. Therefore, continuous quantitative supply of powder with such high precision cannot be achieved by using a continuous quantitative supply method for general powders, such as cement. This is because, in the case of powder, the bulk specific gravity often fluctuates, and in the conventional powder continuous quantification method, slippage occurs at the support part of the conveyor, so even if the rotation speed of the conveyor is This is because even if it is controlled by the ratio of number to supply amount, the supply amount per unit time will fluctuate by about 10 to 20%. On the other hand, accurate ratio control can be achieved by controlling the supply amount per unit time based on the weight as described above.

The kneading operation of the kneading apparatus of the above embodiment will be explained below.

First, a predetermined amount of cement for assimilation is poured into the measuring tank 3 from the cement silo 1. Next, the charged solidified utilization cement is sent to a cement feeder 6, and this cement feeder 6 supplies a predetermined amount of solidifying cement to the kneading device 6 per unit time by a cement feeder rotation speed controller 7. The amount to be supplied per unit time can be constantly monitored by checking the time change in the weight of the weighing tank 3 measured by the weight measuring device 4, and the supply amount can be determined by checking the time change in weight by the water/cement ratio. It is calculated by the control device 5. If this supply amount is not within a predetermined range, a deviation signal based on the difference between the predetermined supply amount and the actual supply amount calculated by calculating the weight change rate is sent to the cement feeder rotation speed controller. 7, and the rotation speed of the rotation shaft of the cement feeder 6 is changed by the cement feeder rotation speed controller 7 to control the supply amount to a predetermined value.

On the other hand, the water supplied to the kneading device 9 is supplied to the kneading device 9 through a flow rate control valve 8, or the flow rate of this flow rate control valve 8 is also controlled by the water/cement ratio control device 5, and the water is solidified. It is controlled by adjusting the valve opening so that it is a constant ratio to the actual supply amount of cement used.

The solidified utilization cement and water thus supplied to the kneading device 9 are sent to the retention section 13 by the rotation of the rotating shaft 12a of the supply section 12. The mixed slurry of solidified utilization cement and water sent to the retention section 13 is kneaded for a certain period of time by the rotation of the rotary stirring blades 13a provided in the retention section 13, and becomes a cement slurry. Here, the time for kneading, that is, the time for residence in the retention section 13, is the time for the cement slurry salt 16 to be mixed.
depends on the height of the weir. Specifically, if the height of the weir is increased, the volume of the retention section 13 will increase, and the retention time will also increase. On the other hand, if the height of the weir is lowered, the volume of the retention section 13 becomes smaller, and as a result, the kneading time becomes shorter. In this way, the kneading time can be controlled by changing the height of the weir, so even if the composition of assimilated cement and/or water changes, the optimal kneading time can be set according to the composition. In addition, even if the supply amount of cement and water for the solidification agent changes, the cement slurry salt 16
By changing the height, the volume of the retention section 13 can be changed according to the supply amount, so the kneading time can be kept constant.

The kneaded cement slurry is then supplied to the radioactive waste treatment container 10 over the weir 16.

Radioactive waste is placed in the radioactive waste processing container 10 in advance. The cement slurry supplied to the processing container 10 permeates into the voids of the radioactive waste. The porosity of radioactive waste differs depending on the type of radioactive waste, and as a result, the amount to be supplied differs depending on the type of radioactive waste loaded even in the same processing container 10. Therefore, as described above, the liquid level is detected by the liquid level detector 18 that detects the liquid level of the cement slurry in the processing container 10, and when the liquid level reaches a predetermined position, the cement slurry salt 16 is raised. and process container 1
Stop the supply of cement slurry into 0. here,
Since we use a weir-based opening/closing mechanism, the supply of cement slurry can be stopped instantaneously.
This is because the processing container 10 can be filled with cement slurry up to the vicinity of the top.

In addition, although the above embodiment has explained the case of solidifying using cement, the present invention is not limited to cement, but can also be applied to water reducing agents, water retaining agents, cement hardening regulators, swelling agents, bone mounds, antifoaming agents, waterproofing agents, etc. additives, such as synthetic resins, commonly used in cement mortar and cement concrete,
Any admixture may be mixed as long as it is an admixture. Furthermore, in the above embodiment, water is mixed into the cement, but the supplied water is not limited to simple water.
Water reducing agents, water retaining agents, cement hardening regulators, swelling agents, antifoaming agents, waterproofing agents, synthetic resin emulsions, and other additives commonly used in cement mortar and cement concrete I. It is okay even if they are mixed. For example, JP-A-63-2 filed by the same applicant as the present application.
No. 28099, Japanese Patent Application Laid-open No. 63-263477,
Specifically, those described in Japanese Patent Application No. 6311, No. 687 and Japanese Patent Application No. 1-71251 are shown.

Further, the kneading apparatus of the present invention is particularly effective for kneading cement for assimilation treatment of radioactive waste whose setting time has been shortened by changing the composition of additives or cement components.

Specifically, the solidification time of normal cement is about 8 hours, but semi-hard cement is created by adding additives or changing the composition of cement components, which takes about 30 minutes to set for 4 to 5 hours. Cement for treatment is assimilated into the inner surface of the kneading tank of the kneading device in a short period of time, making it necessary to shorten the cleaning treatment cycle of the kneading device.

As a result, problems arise such as a decrease in the operating rate. Furthermore, when such cement is used, it is difficult to obtain a homogeneous solidified cement when the cement paste remaining in the kneading container of the kneading device is quickly mixed with newly kneaded cement paste. However, by using the kneading device of the present invention, it is possible to easily obtain high-quality assimilates even with such cement.

A comparison of the performance of the continuous kneading device according to the above embodiment and the conventional batch-type kneading device revealed that, first, if the processing vessel 10 is a drum can with a capacity of 200 g, the conventional batch-type kneading device requires a stirring capacity of at least 200 g. However, considering that in the continuous system of the present invention, the residence time is usually about 2 minutes, and the time required to charge the cement slurry into the drum can is about 5 minutes, a stirring capacity of 40 to 80 ρ is sufficient.

Therefore, the stirring capacity can be reduced to about one-fifth or two-fifths compared to the conventional batch type.

Further, in the above embodiment, the weir 16 is used for the kneaded cement slurry to gain residence time and to allow the cement slurry in the kneading tank to be completely discharged. The means are not limited to such weirs.In other words, if the effective opening amount for discharging the mixed cement slurry is variable, the amount of discharged cement slurry put into the mixing tank is the same as that of the weir. From this point, by controlling the effective opening amount, it becomes possible to control the residence time, that is, the kneading time.

A concrete example of this is shown in FIG. In this figure, only the kneading device is shown, and other parts are omitted because they are the same as in the previously described embodiment. Further, the stirring blades, rotating shaft, etc. are also the same as in the above embodiment, so they are omitted. A side plate 16a that closes one end of the kneading device is provided on the cement slurry discharge side of this kneading device, and this side plate 16a has a discharge port]. 6b is provided. This discharge port 16b is provided with a means for controlling the effective opening amount. Examples of such means include, for example, the one shown in Figure 4 (
A ball valve type as shown in a), a rotary slide type as shown in Figure 4(b), a movable slide type as shown in Figure 4(c), and a narrowing type as shown in Figure 4(d). , an overflow type as shown in FIG. 4(e) is conceivable, but any type may be used as long as the effective opening amount can be changed.

Here, the amount of cement slurry discharged from this discharge port 16b is determined by the amount H of the open area of the control means and the difference in height between the liquid level S of the cement slurry and the above υ1 outlet 16b (see Figure 3). (Reference).

Specifically, when a certain amount of water and cement are being charged into the kneading device from the inlet 5, when the opening area of the control means is narrowed, the liquid level of the cement slurry in the kneading device will rise. , the discharge amount and the input amount are kept in balance at the high position, and when the opening area is widened, the liquid level of the cement slurry in the kneading device is lowered and the discharge amount and the input amount are kept in balance at the lower position. Therefore, by changing the open area, it is possible to change the retention amount of cement slurry during kneading in the kneading device, and as a result, it is possible to control the retention time and kneading time.

On the other hand, a cylinder 22 for opening and closing the side plate 16a is fixed to the lower side of this kneading device. By operating this cylinder 22, the side plate 1.6a rotates around its upper part, as shown in FIG. 5(a), and one end of the kneading device is fully opened. This full opening makes it possible to completely discharge the cement slurry in the kneading device without leaving it behind. On the other hand, during kneading, stirring, and injection into the radioactive waste treatment container, as shown in FIG. 5(b), the side plate 16a is attracted to the kneading device by the cylinder 22, and one end of the kneading device is sealed. There is. With this configuration, it becomes possible to completely discharge the cement slurry and the like in the kneading device, and the kneading device can be easily cleaned.

〔Effect of the invention〕

As explained above, the kneading device of the present invention enables continuous kneading of water and solidified cement, and even in continuous kneading, it is possible to secure sufficient kneading time, and it can follow fluctuations in kneading capacity. This makes it possible to easily produce cement slurry for solidification treatment of higher quality.

Furthermore, in the kneading device of the present invention, the kneading ratio of water and cement used for solidification is adjusted so that the weight of cement for solidifying agent actually supplied is 1.
Since the kneading process is carried out under certain conditions, it is possible to realize a kneading device that can continuously and accurately control the ratio.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a schematic configuration of an example of a radioactive waste solidification processing apparatus incorporating a kneading device of the present invention, FIG. 2 is a diagram showing a schematic configuration of an example of a kneading device according to the present invention, and FIG. A diagram showing the configuration of another embodiment of the device, FIG. 4 is a diagram showing an example of the emission control means applied to the kneading device shown in FIG. 3,
FIG. 5 is a diagram showing how the kneading device shown in FIG. 3 is used, and FIG. 6 is a diagram showing a schematic configuration of the conventional kneading device. 1... Cement silo, 2... Water tank, 3...
Measuring tank, 4... Weight measuring device, 5... Water/cement ratio control device, 6... Cement feeder, 7...
Cement feeder rotation speed controller, 8... Water supply control valve, 9... Kneading device, 10... Radioactive waste treatment container, 12... Supply section, 1.2 a... Rotating shaft, ] 3...
- Stirring section, 1, 3a... Stirring blade, 16... Cement slurry weir, 18... Liquid level detector. Solidification treatment equipment Figure 1 Emission control means device, funeral diagram Conventional example part diagram

Claims (1)

[Scope of Claims] 1. An input port into which cement for solidification treatment of radioactive waste and water are input; a kneading tank for kneading the cement for solidification treatment and water continuously input from the input port; a stirring and kneading means for stirring and kneading the cement for solidification treatment put into the kneading tank and water; and a stirring and kneading means provided in the tank on the side opposite to the input port, through which the cement slurry for solidification treatment that has been stirred and kneaded is passed. and a cement slurry discharge means whose effective release amount is variable. 2. An input port into which cement for solidification treatment of radioactive waste and water are input; a kneading tank for kneading the cement for solidification treatment and water continuously inputted from the input port; a stirring and kneading means for stirring and kneading the solidified cement for solidification and water; and a stirring and kneading means provided in the tank on the opposite side of the inlet to discharge the stirred and kneaded cement slurry for solidification by overflowing from the upper part. Cement mixing equipment for the solidification treatment of radioactive waste, including a cement slurry weir. 3. The height of the weir of the cement slurry weir is variable;
3. The cement kneading apparatus for solidifying radioactive waste according to claim 2, wherein said cement slurry weir can be fully opened. 4. Further comprising an input control means for continuously controlling the ratio of the respective inflow amounts from the cement hopper for solidification treatment and the water tank connected to the input port, and the input control means controls the weight change of the cement hopper for solidification treatment. The cement kneading apparatus for solidifying radioactive waste according to claim 2 or 3, wherein the ratio of each inflow amount is controlled according to the ratio.