JPH1062595A - Radioactive waste liquid processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a backwash operation of filter, simplify operation action by avoiding a backwash water transport pipe and reduce the equipment size reducing the capacity of sludge storage. SOLUTION: Downstream of an LCW collection tank 5 accepting radioactive waste liquid containing sludge 4 in a sedimentation tank 2, a rotary filter 24 is arranged instead of conventional LCW filter device assembled with hollow fiber membrane filter. With this rotary filter 24, the sludge 4 in radioactive waste liquid from the LCW collection tank 5 is filtered. By this, backwash operation conducted with hollow fiber member filter becomes unnecessary and providing a backwash water line returning the backwash water to the sedimentation tank 2 is not required. Thus, operation action for this is simplified and the equipment can be reduced in size. Besides, as the sludge filtered in the rotary filter 24 can be stored directly in a drum 25, the extraction process of sludge 4 from the sedimentation tank 2 becomes unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radioactive liquid waste treatment method for treating a radioactive liquid waste containing an insoluble substance generated in a nuclear power plant.

[0002]

2. Description of the Related Art Generally, an apparatus for treating a radioactive waste liquid containing an insoluble substance generated in a nuclear power plant, etc., captures the insoluble substance in the waste liquid with a hollow fiber membrane filter and converts the soluble substance into an ion exchange resin. After removing the radioactive material in the radioactive waste liquid by using the water, the treated water is reused in the plant. The insoluble substance captured by the hollow fiber membrane filter is peeled off by detecting a decrease in the flow rate or an increase in the pressure and performing appropriate back washing.

An example in which a hollow fiber membrane filter is used in an apparatus for treating radioactive liquid waste will be described with reference to FIG. In FIG. 3, reference numeral 1 denotes a condensate filtration device configured by incorporating a hollow fiber membrane filter, 2 denotes a sedimentation separation tank connected to the condensate filtration device 1,
3 is the supernatant in the settling tank 2 and 4 is sludge,
Reference numeral 5 denotes a low conductivity waste liquid (hereinafter referred to as LCW) collection tank into which the supernatant 3 flows into the sedimentation separation tank 2, and reference numeral 6 denotes an LC having a built-in hollow fiber membrane filter connected to the LCW collection tank 5.
W filtration devices 7 are LCW desalination devices connected to the LCW filtration device 6.

[0004] Here, the condensate filtration device 1 and the LCW filtration device 6 capture insoluble substances with a hollow fiber membrane filter, and the LCW desalination apparatus 7 captures soluble substances with an ion exchange resin.

The radioactive waste liquid to be treated is a condensate filtration device 1
, And collected in the LCW collection tank 5 via the sedimentation separation tank 2. The waste liquid flowing into the LCW collection tank 5 is the supernatant 3 of the LCW sump and the sedimentation separation tank 2. LCW sump
The waste liquid generated from the LCW equipment flows in.

In the settling / separation tank 2, backwash water generated when the hollow fiber membrane filter in the condensate filtration device 1 installed in the condensate purification system is backwashed, and a backwash water line from the LCW filter device 6. 8
Backwash water flowing through the sedimentation tank 2 and sludge 4
And the dehydrating liquid from the dehydrating device 11 which is performed before the solidifying treatment by the solidifying device 10 flows through the dehydrating liquid line 12.

[0007] The waste liquid in the LCW collection tank 5 in which the supernatant of the LCW sump and the sedimentation separation tank 2 is collected is supplied to the LCW filtration device 6.
The insoluble substance and the soluble substance are removed by the LCW desalting apparatus 7 and used as reuse water.

[0008] The hollow fiber membrane filter has a pore diameter of 0.1 µm. In general, insoluble substances in water at nuclear power plants are 1.0
Most of the particles have a particle size of 1010 μm. Therefore, the insoluble substances captured by these hollow fiber membrane filters flow into the sedimentation separation tank 2.

Here, the structure of the dewatering apparatus 11 for processing the sludge 4 of the settling / separation tank 2 from the extraction line 9 will be described with reference to FIG. In FIG. 4, the dewatering device 11 mainly includes a motor drive unit 13, a speed reduction unit 14, and a solid-liquid separation unit 15. The solid-liquid separation section 15 includes a basket 17, a screen 18, a screw 19, a conical ball 20,
It has a liquid supply pipe 21, a cake discharge pipe 22, and a dehydration outlet 23.

The suspension slurry extracted from the sedimentation / separation tank 2 using a pump or the like is supplied from a liquid supply pipe 21 into a rotating basket 17, and is supplied to a screen 18 stretched on the inner surface of the basket 17. The solid content and the dehydrated liquid are separated by filtration by centrifugal force.

The solids separated by filtration are conveyed to a conical ball 20 by a screw 19, blocked by the conical ball 20, further dehydrated by centrifugal force, conveyed by a screw 19 as cake (solids) and discharged from the cake. Discharge from exit 22. The dehydrated liquid from which solids have been removed flows out from the dehydration port 23 to the sedimentation tank 2 through the dehydration liquid line 12.

[0012]

By the way, as described above, an L filter using a hollow fiber membrane filter for removing insoluble substances is used.
According to the CW filtration device 6, as the waste liquid is treated by the hollow fiber membrane filter, insoluble substances are captured on the hollow fiber membrane, and the flow rate and pressure gradually increase.

Therefore, in order to secure the soundness and the throughput of the hollow fiber membrane filter, it is necessary to detect this and perform an appropriate backwashing operation. The backwash water accompanying this backwash operation is transferred to the sedimentation separation tank 2 through the backwash water line 8 and settled.
The supernatant 3 is transferred to the LCW collection tank 5 so that the LCW
There is a problem that causes an increase in the system flow rate of the system.

Further, according to the above-described method for treating insoluble substances, the insoluble substances captured by the condensate filtration device 1 and the LCW filtration device 6 in the settling / separation tank 2 are backwashed by the operation of backwashing. 8, the insoluble substance is deposited on the bottom of the sedimentation tank 2. The sludge 4 of the insoluble substance deposited on the bottom of the sedimentation separation tank 2 needs to be extracted with a pump or the like. To extract the sludge 4, there is a problem that the concentration of the extracted slurry is high and the possibility of clogging in a pump or a pipe increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and does not generate backwash water flowing into a sedimentation / separation tank, and simplifies operation by eliminating backwash water transfer piping. It is another object of the present invention to provide a radioactive waste liquid treatment apparatus capable of downsizing equipment and reducing the storage capacity of sludge to reduce equipment.

Further, the present invention removes insoluble substance sludge suspended in the sedimentation separation tank, and stores the removed insoluble substance sludge in a container such as a drum can. It is an object of the present invention to provide a radioactive waste liquid treatment apparatus which does not require sludge extraction processing.

[0017]

SUMMARY OF THE INVENTION According to the present invention, there is provided a sedimentation separation tank, a waste liquid collection tank for receiving radioactive waste liquid containing suspended matter in the sedimentation separation tank, and a suspension in the waste liquid collection tank. A rotary filter which is a filtration device for removing water, a container for storing insoluble substances dehydrated by the rotary filter, and a filter cloth pre-coated on the rotary filter.

According to the present invention, since the backwashing operation is not required, the operation operation can be simplified and the equipment can be downsized. In addition, the suspension is pre-coated on the filter cloth of the rotary filter, but since the pre-coat layer is kept at a constant thickness by the stirring blade, the waste liquid can be processed without reducing the processing flow rate. Further, the insoluble substance scraped off by the stirring blade can be discharged outside the apparatus while being concentrated in the rotary filter.

According to a second aspect of the present invention, the filter medium of the rotary filter is made of ceramics, and the ceramics have a pore diameter of 0.1 μm or less. According to the present invention, since the particle size of the insoluble substance is larger than the pore size of the filter medium, without clogging the filter medium with the insoluble substance,
The radioactive waste liquid can be efficiently treated.

[0020] The invention of claim 3 is characterized in that the filter medium of the rotary filter comprises a reverse osmosis membrane. According to the present invention, since the particle size of the insoluble substance is larger than the pore size of the filter medium, without clogging the filter medium with the insoluble substance,
Up to 100 angstroms of insoluble material in radioactive waste can be captured and processed.

According to a fourth aspect of the present invention, a motor for driving a rotary shaft of a rotary filter and a cake discharge valve are connected to a torque control device via a signal cable. According to the present invention, a radioactive waste liquid containing an insoluble substance is treated by switching a rotary filter between a concentration operation and a dehydration operation as necessary. Therefore, it is possible to select whether the water content of the sludge such as the insoluble substance captured on the filter medium of the rotary filter is a concentrate or a dehydrated product.

According to a fifth aspect of the present invention, two rotary filters are arranged in series, a ceramic or filter cloth is incorporated into a filter medium of a rotary filter of a preceding stage, and a reverse osmosis membrane is incorporated into a filter medium of a rotary filter of a subsequent stage. Features.

According to the present invention, the filter medium of the rotary filter is a rotary filter made of ceramics or filter cloth, and captures insoluble substances having a particle diameter of about 1 μm.
By using a reverse osmosis membrane rotary filter to capture insoluble substances up to 100 ohms in particle size,
A clear processing solution can be obtained efficiently.

According to a sixth aspect of the present invention, the container is JISZ16
It is characterized by comprising an open drum or a metal container of 00 or 1601. According to the present invention, sludge discharge such as insoluble matter captured on a filter medium of a rotary filter is stored in a JISZ1600 (steel open drum), a 1601 steel drum (for liquid), a shielded metal container, or the like. .

Thus, since the sludge discharge such as insoluble substances captured by the rotary filter contains radioactive substances, it is shielded from the outside by being stored in the container or the like, and can be handled safely.

The invention according to claim 7 is characterized in that the cake filled in the container from the rotary filter is mixed with a solidifying agent and solidified. Sludge effluent such as insoluble substances captured by the rotary filter is mixed with a solidifying agent such as cement or plastic or asphalt and solidified into a drum. Since the radioactive material in the sludge discharge is thereby solidified, the radioactive material can be held in a stable state in the container.

An eighth aspect of the present invention is characterized in that a liquid inflow pipe of the concentrated waste liquid obtained by evaporating and concentrating the radioactive waste liquid is connected to the liquid inflow pipe of the rotary filter. As the radioactive waste liquid containing the insoluble substance, the concentrated waste liquid obtained by evaporating and concentrating the radioactive waste liquid is filtered through a rotary filter.
By performing the evaporative concentration treatment, the insoluble substance is concentrated, and the treatment capacity for passing water through the rotary filter can be reduced.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a radioactive liquid waste treatment apparatus according to the present invention will be described with reference to FIGS. This embodiment is different from the conventional example shown in FIG. 3 in that (1) the rotary filter 24 shown in FIG. 1 is used instead of the conventional LCW filtration device 6, and (2) the backwash water line shown in FIG. 8, the removal line 9 and the dehydrating liquid line 12 are eliminated.

FIG. 1 is a system diagram showing an apparatus for treating a radioactive waste liquid according to an embodiment of the present invention. FIG. 2 is a diagram showing a rotary filter 24 using a rotary filter 24 instead of the LCW filter 6 in FIG. It is a block diagram which shows a structure schematically.

That is, in this embodiment, as shown in FIG. 1, the radioactive waste liquid containing the insoluble substance is stored in the LCW collection tank 5. The waste liquid flowing into the LCW collection tank 5 is L
CW sump (not shown) and supernatant 3 of sedimentation separation tank 2
In the LCW sump, waste liquid generated from an LCW-based device flows.

The backwash water of the condensate filtration system 1 incorporating the hollow fiber membrane filter flows into the sedimentation separation tank 2. In the sedimentation / separation tank 2, a suspension 4 of insoluble substances and the like in the backwash water is separated into four suspensions and a liquid layer portion of the supernatant 3. 2 at the bottom. The supernatant 3 in the liquid layer portion is transferred to the LCW collection tank 5.

The radioactive waste liquid from the LCW collection tank 5 is solid-liquid separated by a rotary filter 24 into an insoluble substance and a soluble substance, and the soluble substance is removed by the LCW desalting apparatus 7, purified, and reused. Used in the plant.

The insoluble matter captured by the rotary filter 24 is discharged in a cake form from a cake discharge valve 29 of the rotary filter 24 shown in FIG. The cake discharged into the drum 25 is mixed with a solidifying agent such as cement, plastic, or asphalt by the solidifying device 10 and solidified into the drum 25.

Next, in this embodiment, a rotary filter 24 used in place of the conventional LCW filtration device 6 shown in FIG. 3 will be described. The use of the rotary filter 24 instead of the LCW filtration device 6 enables the trapped sludge to be discharged as cake without performing a backwashing operation. There is a great effect that there is no need to extract and treat sludge.

That is, as shown in the enlarged view of FIG. 2, the rotary filter 24 has filter plates 27 and stirring plates 28 alternately arranged in a narrow space in a filtration chamber 26 having a pressure-resistant structure. , And rotates at a constant speed during filtration by driving of the motor 36. The filter plate 27 has a filtrate discharge mechanism 30, and filter cloth is provided on both sides of the filter plate 27.

The waste liquid is supplied under pressure from one of the filtration chambers 26,
It is filtered and dehydrated while moving through the gap of the filter plate 27. The cake is a cake discharge valve 29 provided in the other side of the filtration chamber 26.
Is discharged as a hard paste from the filter plate.
From the filtrate discharge mechanism 30 through the liquid outlet pipe 32, return pipe 33
Discharged to the outside. The cake discharge valve 29 is opened and closed by inputting a signal from the torque control device 31 via a signal cable 38.

The signal cable from the torque controller 31
A signal is input to the motor 36 via 37, and the rotating shaft 35 rotates to control the torque of the stirring plate 28. Rotary filter
Reference numeral 24 denotes a filter that agitates the cake layer adhering to the filter medium surface with a stirring plate 28 to give fluidity to the cake having a predetermined thickness or more. It is discharged outside.

In general, most of insoluble substances in water of a nuclear power plant are particles having a particle size of 1.0 to 10 μm. LCW
The waste liquid flowing into the collection tank 5 is the supernatant liquid 3 of the sedimentation separation tank 2 and the waste liquid waste of the LCW system equipment. It is said that in order to remove particles having a particle size of 1.0 to 10 μm, it is possible to efficiently filter without clogging if the particles are captured with a filter medium having a size smaller by one order.

As the filter medium of the rotary filter 24, it is usually difficult to form a pore size of 1 μm or less by knitting a filter cloth, so that particles in the waste liquid or particles whose particle diameter is known in advance on the surface of the filter cloth are used. Precoat and treat the waste liquid. A filter made of ceramics or a reverse osmosis membrane having a pore diameter of 0.1 μm or less may be used.

Further, the rotary filter 24 can switch between the concentration operation and the dehydration operation by adjusting the torque control device 31 according to the processing flow rate, the property of the waste liquid, the form of the discharge cake, and the like.

In the treatment of radioactive waste liquid, by selecting the filter medium of the rotary filter 24, for example, when two rotary filters 24 are arranged in series, a filter cloth or a ceramic filter medium is used as the filter medium of the first rotary filter 24. A reverse osmosis membrane is used as a filter medium for the second rotary filter. As a result, the insoluble substance having a coarse particle diameter is captured by the first device, and the fine particles are captured by the second device, so that clear treated water can be efficiently obtained.

The drum 25 is preferably JIS Z1600, 1601 or a shielded metal container for corrosion and shielding from the outside. In addition, although the supernatant 3 of the sedimentation separation tank 2 and the waste liquid of the LCW system equipment are described as the waste liquid flowing into the LCW collection tank 5, the concentrated waste liquid after evaporating and concentrating the radioactive waste liquid is also described. Can be processed.

[0043]

According to the first aspect of the present invention, the suspended substance is pre-coated on the filter cloth of the rotary filter. However, the pre-coat layer is maintained at a constant thickness by the stirring blade.
The waste liquid can be processed without reducing the processing flow rate.

Further, the sludge shaved off by the stirring blade is discharged outside the rotary filter while being concentrated in the rotary filter, so that the backwashing operation is not required. Thereby, there is no generation of backwash water, and the driving operation can be simplified. Further, the backwashing water line from the rotary filter and the dehydrating liquid line from the dewatering device can be omitted, and the equipment can be significantly reduced because the sludge storage capacity of the settling tank is reduced.

According to the second aspect of the present invention, since the particle size of the insoluble substance is larger than the pore size of the filter medium, the radioactive waste liquid can be efficiently treated without clogging of the filter medium insoluble substance. Therefore, it is possible to reduce the number of cleaning operations performed to improve the increase in pressure and the decrease in processing flow rate due to clogging of the filter medium. Further, since the number of times of washing is reduced, it is possible to reduce the amount of washing waste liquid generated and maintain the soundness of the filter medium.

According to the third aspect of the present invention, since the particle size of the insoluble substance is larger than the pore size of the filter medium, the filter medium does not become clogged with the insoluble substance. In addition, 1 in radioactive waste liquid
Since it is possible to capture and process even an insoluble substance having a thickness of 00 Å, a clear processing solution can be obtained as reuse water.

According to the fourth aspect of the present invention, the operation of the rotary filter can be switched between the concentration operation and the dehydration operation without changing the equipment. In addition, the water content of the sludge can be selected. Thus, the sludge can be processed into a form as required.

According to the fifth aspect of the present invention, ceramics or filter cloth is used as a filter medium of the rotary filter in the preceding stage to capture insoluble substances having a particle diameter of about 1 μm.
By using a reverse osmosis membrane as the filter medium of the subsequent rotary filter and capturing insoluble substances having a particle size of up to 100 Å, clear and reused water can be obtained efficiently.

According to the sixth aspect of the present invention, since the sludge discharge such as insoluble substances captured by the rotary filter contains radioactive substances, it is stored in JIS Z1600, 1601, a shielded metal container or the like. Thereby, the sludge discharge is shielded from the outside and can be handled safely.

According to the invention of claim 7, the sludge discharge is mixed with a solidifying agent and solidified in a container such as a drum. Therefore, the radioactive substance can be held in the container in a stable state.

According to the eighth aspect of the present invention, by treating the waste liquid subjected to the evaporation and concentration treatment, the insoluble substance is concentrated, and the processing capacity for passing water through the rotary filter can be reduced. The diameter can be reduced.

[Brief description of the drawings]

FIG. 1 is a system diagram for explaining an embodiment of a radioactive liquid waste treatment apparatus according to the present invention.

FIG. 2 is a configuration diagram showing a rotary filter in FIG. 1 in an enlarged schematic cross section.

FIG. 3 is a system diagram for explaining a conventional radioactive waste liquid treatment method.

FIG. 4 is an enlarged longitudinal sectional view of the dehydrating apparatus in FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Condensate filtration apparatus 2 ... Sedimentation separation tank 3 ... Supernatant liquid 4 ...
Sludge suspension, 5: LCW collection tank, 6: LCW filtration device, 7: LCW desalination device, 8: Backwash water line, 10: Solidification device, 11: Dehydration device, 12: Dehydration liquid line, 13: Motor Drive unit, 14 ... reduction unit, 15: solid-liquid separation unit, 16: casing,
17… Basket, 18… Screen, 19… Screw, 20
… Conical ball, 21… supply tube, 22… cake discharge tube, 23… dewatering outlet, 24… rotary filter, 25… drum, 26…
Filtration chamber, 27… Filter plate, 28… Stirring plate, 29… Cake discharge valve,
30: Filtrate discharge mechanism, 31: Torque control device, 32: Liquid outlet pipe, 33: Return pipe, 34: Liquid inlet pipe, 35: Rotating shaft, 36: Motor, 37, 38 ... Signal cable.

Claims (8)

[Claims] 1. A sedimentation separation tank, a waste liquid collection tank for receiving radioactive waste liquid containing sludge in the sedimentation separation tank,
A rotary filter for filtering sludge in the waste liquid collecting tank, a container for storing insoluble substances dehydrated by the rotary filter, and a filter cloth pre-coated on the rotary filter; Processing equipment. 2. The radioactive waste liquid treatment apparatus according to claim 1, wherein the filter medium of the rotary filter is made of ceramics, and the pore diameter of the ceramics is 0.1 μm or less. 3. The radioactive waste liquid treatment apparatus according to claim 1, wherein the filter medium of the rotary filter is made of a reverse osmosis membrane. 4. The radioactive waste liquid treatment apparatus according to claim 1, wherein a motor for driving a rotary shaft of the rotary filter and a cake discharge valve are connected to a torque control device via a signal cable. 5. The rotary filter according to claim 1, wherein two rotary filters are arranged in series, a ceramic or filter cloth is incorporated in a filter medium of a rotary filter of a preceding stage, and a reverse osmosis membrane is incorporated in a filter medium of a rotary filter of a subsequent stage. Item 6. The radioactive liquid waste treatment apparatus according to Item 1. 6. The radioactive waste liquid treatment apparatus according to claim 1, wherein the container is formed of a JIS Z1600 or 1601 open drum or a metal container. 7. The radioactive waste liquid treatment apparatus according to claim 1, wherein the cake filled in the container from the rotary filter is mixed and solidified with a solidifying agent. 8. The apparatus for treating radioactive waste liquid according to claim 1, wherein an inflow pipe for a concentrated waste liquid obtained by evaporating and concentrating the radioactive waste liquid is connected to a liquid inflow pipe of the rotary filter.