JP2002139595A - Radioactive waste liquid disposal system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the disposal time and improve the reliability of filtrate quality by monitoring the state of a cake layer formed within a filter. SOLUTION: A pump 2 and the filter 3 are connected to a radioactive waste liquid collecting tank 1 through piping. A turbidmeter 8 is set in the filtrate discharging pipe 18 of the filter 3. The outlet side of the turbidmeter 8 is connected to a sump tank 4 through a sump tank inlet valve 21. The sump tank inlet valve 21 is remotely opened and closed by a measurement control device 11. One side of a return pipe 5 branched from the sump tank inlet valve 21 is connected to the outlet side of the turbidmeter 8, and the other is connected to the collecting tank 1. A collecting tank return valve 20 remotely opened and closed by the measurement control device 11 is set in the return pipe 5. A cake discharge valve 19 is connected to the cake discharge side of the filter 3, and a metal drum 6 is connected to the downstream side from the cake discharge valve 19. A powdery activated charcoal feeder 7 is connected to the collecting tank 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radioactive waste liquid treatment for treating a washing waste liquid, a shower drain, or a radioactive waste liquid containing a chemical oxygen demand (COD) component or an oil component generated in a nuclear power plant or the like. About the system.

[0002]

2. Description of the Related Art A washing waste liquid or a radioactive waste liquid such as a shower drain generated at a nuclear power plant or the like is subjected to an adsorption treatment and a filtration treatment with powdered activated carbon, together with a detergent component and a dirt component transferred from the laundry to the waste liquid by washing or the like. After removing radioactive materials, the treated water is discharged outside the plant.

[0003] The treatment of washing waste liquid or shower drain is as follows:
Radioactive material concentration of treated water or water quality [SS (suspended matter) concentration, COD (chemical oxygen demand) concentration, n-hexane extractables concentration, pH] described in the environmental impact report are control values determined by each nuclear power plant It is implemented as follows.

A conventional radioactive waste treatment system of this type will be described with reference to FIG. In FIG. 5, the suction side of a pump 2 is connected to the bottom of a collection tank 1 for collecting radioactive waste liquid via a pipe, and the discharge side of the pump 2 is connected to a filter 3. The filtered water outlet side of this filter 3 is a filtered water outflow pipe
It is connected to the sump tank 4 via 10.

[0005] A return pipe 5 branching off from the filtered water outflow pipe 10 and connecting to the collection tank 1 is connected, and the cake discharge side of the filter 3 is connected to the drum 6 via a cake discharge valve 19. The collection tank 1 is connected to a powdered activated carbon feeder 7. The return pipe 5 is connected to a collection tank return valve 20, and the filtered water outflow pipe 10 is connected to a sump tank inlet valve 21.

The above-mentioned radioactive waste liquid treatment system receives a radioactive waste liquid (raw liquid) such as a washing waste liquid or a shower drain in the collection tank 1, and a chemical oxygen demand (COD) which is a dissolved component contained in the received waste liquid. Powdered activated carbon is supplied or injected from the powdered activated carbon feeder 7 to reduce the amount of powdered activated carbon.

[0007] Collection tank 1 adsorbing these dissolved components
The radioactive waste liquid in the inside is transferred to the filter 3 by the pump 2. The powdered activated carbon to which the dissolved components are adsorbed and the suspended solids (SS) contained in the waste liquid are filtered by the filter 3, and the filtered water is collected into the sump tank 4 through the filtered water outflow pipe 10. The powdered activated carbon and the suspended solids filtered by the filter 3 are concentrated in the filter 3, formed into a cake, discharged to the drum 6 through the cake discharge valve 19, and filled in the drum 6.

[0008] The filter 3 includes a stirring blade 3b in a filtration chamber 3a.
And the filter plate 3c are alternately arranged at a narrow interval, and the stirring blade 3b is rotated at a constant speed by the rotation drive of the motor 17 during filtration. The filtration plate 3c has a filtrate discharge mechanism 18, and filtration membranes are stretched on both sides of the filtration plate 3c.

The radioactive waste liquid supplied from the collection tank 1 to the filter 3 through the pump 2 is supplied under pressure from one of the filtration chambers 3a and is formed on the surface of a filtration membrane stretched on both sides of the filtration plate 3c. The filtrate is finely filtered by the cake layer of the powdered activated carbon and the suspended substance, and the filtrate is discharged from the filtrate discharge mechanism 18 of the filter plate 3c via the filtered water outflow pipe 10 by opening / closing the return valve 20 or the sump tank inlet valve 21. 5 to the sump tank 1 or the filtered water outflow pipe 10 to the sump tank 4.

A cake layer of powdered activated carbon and a suspended substance is formed on the surface of a filtration membrane stretched on both sides of the filter plate 3c, and the cake layer does not grow beyond a certain thickness due to the action of the stirring blade 3b. Then, the water is filtered and dehydrated while passing through the space between the filter plates 3c and moving toward the cake discharge valve 19 provided in the other side of the filter chamber 3a.

When the above-mentioned cake layer is not formed, the filtrate discharged to the outside via the filtrate discharge mechanism 18 contains a large amount of powdered activated carbon and suspended matter, and is transferred from the return pipe 5 to the collection tank 1. You. When the cake layer is formed, the filtrate becomes clear and is transferred to the sump tank 4 by opening and closing the collection tank return valve 20 or the sump tank inlet valve 21.

When the above-mentioned cake layer is not formed, the motor 17 is controlled to rotate the filter plate 3b at a low speed in order to stably grow the cake layer. When the cake layer is formed, the filter plate 3b is rotated at a high speed by the motor 17. The cake is discharged from the cake discharge valve 19 to the drum 6 in the form of a hard paste. The torque of the motor 17 of the stirring blade 3b is controlled by a torque control device.

[0013]

By the way, in the conventional radioactive waste liquid treatment system described above, the powdered activated carbon and the suspended solids formed on the surface of the filtration membrane stretched on both sides of the filter plate 3c at the start of the treatment operation and the like. From the state where the cake layer does not exist, the time until the cake layer was formed and the filtrate became clear and the quality of the filtered water that could be transferred to the sump tank 4 was monitored over time. This time needs to be a time that has a sufficient margin with respect to the filtrate clarification time confirmed by a test operation or the like. However, there is a problem that the processing time becomes longer by a margin.

Further, if the filtration membrane stretched on both sides of the filter plate 3c becomes abnormal even after the transfer to the sump tank 4 is started after the elapse of the filtrate clarification time, the filtrate which has not been refined is removed from the sump tank. 4 and there is a problem with the reliability of the filtered water quality.

The present invention has been made to solve the above-mentioned problems, and indirectly confirms the state of a cake layer of powdered activated carbon and suspended solids formed on the surface of a filtration membrane stretched on both sides of a filtration plate 3c. Accordingly, it is an object of the present invention to provide a radioactive waste liquid treatment system that shortens the treatment time and improves the reliability of filtered water quality.

[0016]

The invention according to claim 1 is
A collection tank for radioactive waste liquid, a filter connected to the outlet side of the collection tank via a pump, a sump tank connected to the filtrate outlet side of the filter via a filtered water outflow pipe, A powdered activated carbon feeder connected to a tank, a return pipe branched from the filtered water outflow pipe and the other end connected to the collection tank, a stirring blade installed in the filter, and the filtered water outflow pipe. And a turbidity meter provided.

According to the present invention, by measuring the turbidity of the filtered water, the state of the cake layer of the activated carbon powder and the suspended substance formed on the surface of the filtration membrane stretched on both sides of the filter plate is ensured, Filtration time can be reduced. Further, even after the transfer of the filtered water to the sump tank after the cake layer is formed, the reliability of the filtered water quality can be improved by indirectly checking the state of the cake layer.

According to a second aspect of the present invention, a return valve is attached to the return pipe, a sump tank inlet valve is attached to the filtered water outflow pipe connected to the sump tank, and a detection signal of the turbidity meter is input. A measurement control device for outputting a control signal to the return valve or the sump tank inlet valve is provided.

According to the present invention, the turbidity meter for measuring the turbidity at the outlet side of the filtered water of the filter is monitored by the measurement control device,
When the turbidity exceeds the set value, an alarm is issued and at the same time, the collection tank return valve or the sump tank inlet valve is switched by remote automatic operation of the measurement control device, and the filtered water flow after filtration is switched to the collection tank or the sump tank and flows in can do.

In this case, in particular, if an output signal system for inputting the output signal of the measurement control device to the torque control device for controlling the rotation speed of the stirring blade is provided, the outlet side of the filtered water outflow pipe of the filter can be provided. The rotation speed of the stirring blade in the filter can be switched to low speed by remote automatic operation of the measurement control device for monitoring the turbidity of the water.

According to a third aspect of the present invention, there is provided a collecting tank for radioactive waste liquid, a filter connected to the outlet side of the collecting tank via a pump, and a filtered water outlet pipe at a filtered water outlet side of the filter. A sump tank interposed and connected, a powdered activated carbon feeder connected to the collection tank, a return pipe branched from the filtered water outflow pipe and the other end connected to the collection tank, and installed in the filter. And a differential pressure gauge provided between the discharge side of the pump and the filtered water outflow pipe via a differential pressure gauge mounting pipe.

According to the present invention, the powdered activated carbon formed on the surface of the filtration membrane stretched on both sides of the filter plate is measured by measuring the pressure difference between the inlet side of the filter and the outlet side of the filtrate in the filtration process. The state of the cake layer of suspended solids can be confirmed and treated indirectly. Further, even after the transfer to the sump tank is started after the formation of the cake layer, the reliability of the filtered water quality can be improved by indirectly checking the state of the cake layer.

According to a fourth aspect of the present invention, a return valve is attached to the return pipe, a sump tank inlet valve is attached to the filtered water outflow pipe connected to the sump tank, and a detection signal of the differential pressure gauge is inputted. A measurement control device for outputting a control signal to the return valve or the sump tank inlet valve is provided.

According to the present invention, while the filtrate is being transferred to the sump tank, the measurement value of the differential pressure gauge is monitored by the measurement control device, and when the differential pressure becomes equal to or less than the set value, an alarm is issued and the measurement is performed at the same time. The collection tank return valve is opened and the sump tank inlet valve is closed by the remote automatic operation of the control device, the filtrate is closed, and the filtrate is transferred to the collection tank via the return pipe. By switching the return valve or the sump tank inlet valve, the filtered water flow after the filtration can flow into the collection tank or the sump tank.

In this case, in particular, if an output signal system for inputting the output signal of the measurement control device to the torque control device for controlling the rotation speed of the stirring blade is further provided, it is possible to automatically control the measurement control device by remote control. The stirring blades of the filter can be switched to low-speed rotation. Also, by measuring the pressure difference between the inlet side of the filtered water and the outlet side of the filtered water, the rotation speed of the stirring blade in the filter can be controlled.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a radioactive liquid waste treatment system according to the present invention will be described with reference to FIGS. The same parts as those in FIG. 1 are denoted by the same reference numerals. In FIG. 1, one end of a pipe is connected to the bottom of a collection tank 1 for collecting radioactive waste liquid, the suction side of a pump 2 is connected to the other end of the pipe, and the discharge side of the pump 2 is connected to a filter 3 by a pipe. .

A filtrate discharge mechanism 18 is attached to a filter plate 3c installed in a filtration chamber 3a in the filter 3, and the turbidity of the filtrate is measured in a filtrate water outflow pipe 10 connected to the filtrate discharge mechanism 18. A turbidimeter (Tu) 8 is installed. The outlet side of the turbidity meter 8 is connected to the sump tank 4 via the filtered water outflow pipe 10, and the filtered water outflow pipe 10 connected to the sump tank 4 is remotely operated from the output signal line 13 by the measurement control device 11. The sump tank inlet valve 21 which opens and closes according to is installed.

The outlet side of the turbidity meter 8 and the sump tank inlet valve 21
One end of the return pipe 5 is connected from the filtered water outflow pipe 10 to the inlet side, and the other end is connected to the collection tank 1. The return pipe 5 is provided with a collection tank return valve 20 that is opened and closed by remote control by the measurement control device 11. The cake discharge side of the filter 3 is connected to the drum 6 via the cake discharge valve 19.
Connect to The collection tank 1 is connected with a powdered activated carbon feeder 7.

The filter 3 includes a stirring blade 3b in a filtration chamber 3a.
And the filter plate 3c are alternately arranged at a narrow interval, and the stirring blade 3b is rotated at a constant speed by the rotation drive of the motor 17 during filtration. The filtration plate 3c has a filtrate discharge mechanism 18, and filtration membranes are provided on both sides of the filtration plate 3c.

The input side of the measurement control device 11 is connected to the turbidity meter 8 via the detection signal line 12, and the output side thereof is connected via the output signal line 13 to the return valve 20, the sump tank inlet valve 21 and the torque control device. Connected to 14. The torque control device 14 is connected to a motor 17 via a torque control signal line 16.

The waste liquid supplied from the collection tank 1 to the filter 3 through the pump 2 is supplied under pressure from one of the filtration chambers 3a of the filter 3, and is filtered and dehydrated while moving through the space between the filter plates 3c. You.

The powdered activated carbon and the suspended solids (SS) that have adsorbed the dissolved components filtered by the filter plate 3c of the filter 3 are concentrated in the filtration chamber 3a to form a cake. The cake is discharged into the drum 6 in the form of a hard paste from a cake discharge valve 19 disposed on the other side of the filtration chamber 3a. Filtrate is filter plate 3
The liquid is discharged to the outside from the filtrate discharge mechanism 18 of (c) through the filtered water outflow pipe 10 and transferred to the collection tank 1 or the sump tank 4 from the return pipe 7. The torque of the stirring blade 3b is controlled by a torque controller 14 via a motor 17.

In the processing operation, the collection pump 2 is started, and the stock solution is supplied under pressure from the collection tank 1 to one of the filtration chambers 3 a of the filter 3. The filter 3 rotates the stirring blade 3b at a low speed in order to form a stable cake layer with the powdered activated carbon and the suspended matter on the surface of the filtration membrane stretched on both sides of the filter plate 3c.

The filtrate is discharged from the filtrate discharge mechanism 18 of the filter plate 3c to the outside via the filtered water outflow pipe 10, and is transferred from the return pipe 5 to the collection tank 1. At this time, the collection tank return valve 20 is opened and the sump tank inlet valve 21 is closed by remote automatic operation based on the input from the output signal line 13 of the measurement control device 11.

The turbidity meter 8 installed in the filtered water outflow pipe 10 of the filter 3 is monitored by the measurement control device 11, and when the turbidity falls below the set value, the torque control device 14 is automatically operated by the measurement control device 11 by remote control. The rotation of the stirring blade 3b of the filter 3 is controlled at a high speed by the control of the motor 17 by the torque control signal line 16 from the motor. Thereafter, if the turbidity is equal to or less than the set value, the collection tank return valve 20 is closed and the sump tank inlet valve 21 is opened by remote control by the measurement control device 11, and the filtrate is transferred to the sump tank 4.

While the filtrate is being transferred to the sump tank 4, the turbidity meter 8 installed in the filtered water outflow pipe 10 of the filter 3 is monitored by the measurement control device 11, and if the turbidity exceeds the set value, At the same time as issuing an alarm, the collection tank return valve 20 is opened and the sump tank inlet valve is opened by remote automatic operation of the measurement control device 11.
21 is closed, and the filtrate is transferred to the collection tank 1 via the return pipe 5. Further, the motor 17 is controlled by remote automatic operation of the measurement control device 11, and the stirring blade 3b of the filter 3 is switched to low-speed rotation.

When the measured value of the turbidity meter 8 with respect to the elapsed time of the treatment operation is compared with the analysis result obtained by sampling the filtrate and measuring the SS (suspended substance) concentration, it has almost the same tendency as shown in FIG. Curve can be obtained. FIG.
In the graph, the horizontal axis represents time, and the vertical axis represents the relationship between turbidity and SS concentration.

This result is obtained by monitoring the measured value of the filtrate turbidity meter to detect an abnormality in the concentration of SS (floating substance) contained in the filtrate, and automatically controlling the sump tank 4 by remote automatic control by the measurement control device 11. Alternatively, it indicates that transfer switching control to the collection tank 1 is possible.

That is, if the measured value of the turbidity meter 8 is below a certain value, the SS (floating substance) concentration of the filtrate is low, so that the cake layer of the activated carbon powder and the floating substance is formed on the surface of the filtration membrane of the filter plate 3b. Well formed.

Next, a second embodiment of the radioactive liquid waste treatment system according to the present invention will be described with reference to FIGS. In FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description of the overlapping parts will be omitted.

In order to achieve the same function as that of the turbidimeter 8 in the first embodiment shown in FIG.
In order to measure the pressure difference between the inlet side of the filter 3 and the filtered water outflow pipe 10 of the filter 3 as shown in FIG.
In other words, the differential pressure gauge (dP) 9 is installed via 15.

In the present embodiment, after the processing operation is started in the same manner as in the first embodiment, the measurement value of the differential pressure gauge 9 is monitored by the measurement control device 11, and the differential pressure becomes equal to or higher than the set value. For example, the stirring blade 3b of the filter 3 is rotated at high speed by remote automatic operation of the measurement control device 11. Thereafter, if the differential pressure is equal to or higher than the set value, the collection tank return valve 20 is closed and the sump tank inlet valve 21 is opened by remote control by the measurement control device 11, and the filtrate is transferred to the sump tank 4.

While the filtrate is being transferred to the sump tank 4, the measurement value of the differential pressure gauge 9 is monitored by the measurement control device 11. The collection tank return valve 20 is opened and the sump tank inlet valve 21 is closed by remote automatic operation, and the filtrate is transferred to the collection tank 1 via the return pipe 5. Further, the stirring blade 3b of the filter 3 is automatically operated by the remote control of the measurement control device 11.
Switch to low speed rotation.

When the measured value of the differential pressure gauge 9 with respect to the elapsed time of the processing operation is compared with the analysis result obtained by sampling the filtrate and measuring the concentration of SS (floating substance), as shown in FIG.
= A (a is a constant).

This result is obtained by detecting the abnormality of the cake layer formed on the surface of the filtration membrane stretched on the surface of the filter plate 3c by monitoring the differential pressure of the filter 3, and This indicates that the transfer switching control to the sump tank 4 or the collection tank 1 can be performed by the automatic control.

That is, if the value measured by the differential pressure gauge 9 is a certain value or more, the cake layer of the activated carbon powder and the suspended substance is sufficiently formed on the surface of the filtration membrane of the filtration plate b, and the filtration is performed by the fine filtration by the cake layer. It can be confirmed that the SS (floating substance) concentration of the liquid has been reduced to a predetermined value or less.

It is to be noted that a configuration in which the first embodiment is combined with the present embodiment, that is, a configuration in which a turbidity meter 8 and a differential pressure gauge 9 are installed together to perform switching control during waste liquid treatment complementarily is also possible. Good.

[0048]

According to the present invention, in the treatment of the filter, the state of the cake layer of the powdered activated carbon and the suspended substance formed on the surface of the filtration membrane stretched on both sides of the filter plate is indirectly confirmed. As a result, the treatment time can be shortened, and the reliability of the filtered water quality can be improved.

Therefore, the filter removes the radioactive substances in the radioactive waste liquid (raw liquid) such as the washing waste liquid or the shower drain containing the radioactive substances generated in a nuclear power plant or the like,
The water quality standards described in the Environmental Impact Report can be satisfied.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a first embodiment of a radioactive liquid waste treatment system according to the present invention.

FIG. 2 is a system diagram showing a second embodiment of the radioactive liquid waste treatment system according to the present invention.

FIG. 3 is a characteristic diagram showing a change in turbidity at an outlet of a filter and a concentration of SS (floating substance) with respect to a processing time in the first embodiment shown in FIG. 1;

FIG. 4 is a characteristic diagram showing changes in a filter differential pressure and an SS (suspended substance) concentration with respect to a processing time in the second embodiment shown in FIG. 2;

FIG. 5 is a system diagram showing a conventional radioactive waste liquid treatment system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Collection tank, 2 ... Pump, 3 ... Filter, 4 ... Sump tank, 5 ... Return piping, 6 ... Drum, 7 ... Powdered activated carbon feeder, 8 ... Turbidity meter (Tu), 9 ... Differential pressure gauge (dP) ),Ten
… Filtration water outflow pipe, 11… Measurement control device, 12… Detection signal line, 13… Output signal line, 14… Torque control device, 15… Differential pressure gauge mounting pipe, 16… Torque control signal line, 17… Motor, 18… Filtration water discharge pipe, 19 ... cake discharge valve, 20 ... collection tank return valve, 21 ... sump tank inlet valve.

Claims (5)

[Claims] 1. A collection tank for a radioactive waste liquid, a filter connected to an outlet side of the collection tank via a pump, and a sump connected to a filtrate outlet side of the filter via a filtered water outflow pipe. A tank, a powdered activated carbon feeder connected to the collection tank, a return pipe branched from the filtered water outflow pipe and the other end connected to the collection tank, a stirring blade installed in the filter, A radioactive waste liquid treatment system, comprising: a turbidity meter provided in a filtered water outflow pipe. 2. A return valve is attached to the return pipe, a sump tank inlet valve is attached to the filtered water outflow pipe connected to the sump tank, a detection signal of the turbidity meter is input, and the return valve or the sump is input. 2. The radioactive waste liquid treatment system according to claim 1, further comprising a measurement control device that outputs a control signal to the tank inlet valve. 3. A collection tank for radioactive waste liquid, a filter connected to the outlet side of the collection tank via a pump, and a sump connected to the filtrate outlet side of the filter via a filtered water outflow pipe. A tank, a powdered activated carbon feeder connected to the collection tank, a return pipe branched from the filtered water outflow pipe and the other end connected to the collection tank, a stirring blade installed in the filter, A radioactive waste liquid treatment system, comprising: a differential pressure gauge provided between a discharge side of a pump and the filtered water outflow pipe via a differential pressure gauge mounting pipe. 4. A return valve is attached to the return pipe, a sump tank inlet valve is attached to the filtered water outflow pipe connected to the sump tank, a detection signal of the differential pressure gauge is input, and the return valve or the sump tank is input. 4. The radioactive waste liquid treatment system according to claim 3, wherein a measurement control device that outputs a control signal is provided at the inlet valve. 5. An output signal system for inputting an output signal of the measurement control device to a torque control device for controlling a rotation speed of the stirring blade.
The radioactive waste liquid treatment system according to the above.