JPH0139079B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a method for cleaning radioactive waste liquid processing equipment, and in particular, a method for evaporating and drying radioactive waste liquid or slurry generated at a nuclear power plant and solidifying the dried product. It is suitable for radioactive waste liquid treatment equipment.

[Background of the invention]

An example of a conventional radioactive waste liquid treatment device and its cleaning method will be explained with reference to FIG.

FIG. 1 is a system diagram of the radioactive waste liquid processing equipment, in which the waste liquid supply tank 1 includes a waste liquid source valve 30 and a liquid supply pump 1.
0, a heating jacket 11 to which a conduit 50 is connected and conduits 51 and 52 for heat medium supply and discharge are connected;
A drying device 14 is provided, in which a rotary blade 13 driven by a drive device 12 such as an electric motor is rotatably installed. 15 and further connected to a feeder 16 via a dry matter valve 32, and the feeder 16 is connected to a solidification processing device 17 and a solidified matter filling can 18 through a feeder outlet valve 32. On the other hand, a condenser 19 and a drying device 1 are connected to conduits 58 and 59 for supplying and discharging cooling water.
4 are connected by a conduit 55.

Radioactive waste liquid generated at a nuclear power plant or the like is transferred to a waste liquid supply tank 1 and temporarily stored therein, and is supplied to a drying device 14 via a waste liquid main valve 30 and a conduit 50 at a predetermined supply capacity by a liquid supply pump 10. .
Here, the radioactive waste liquid is transferred to the drying device 1 by the centrifugal force of the rotating blades 13 driven by the driving device 12.
4 is spread out into a thin film on the inner wall surface, and is evaporated and dried by the heating of the heating medium flowing through the conduit 51, the heating jacket 11, and the conduit 52. The evaporated matter is supplied to the condenser 19 through the conduit 55, where it is condensed with cooling water supplied through the conduit 58 and discharged through the conduit 59, and the condensate is sent to other systems via the condensate outlet valve 34 through the conduit 60. The liquid is delivered. The non-condensable gas in the evaporated material is sent through the vent outlet valve 35 and through the conduit 57 to other vent processing systems. On the other hand, the dry matter is dried through the dry matter outlet pipe 5.
3, enters the dry material hopper 15, and enters the dry material valve 32.
The dried material is supplied to one end of the feeder 16 through the feeder 16, and after being transferred to the other end, it is supplied to the solidification processing device 17 via the feeder outlet valve 33 and the conduit 40, where the dried material is solidified in a method suitable for long-term storage or disposal. The solidified material is filled into the solidified material filling can 18 through the conduit 41.

In order to carry out a series of these processes smoothly, the radioactive waste liquid processing equipment must be maintained in good health. In other words, the radioactive waste liquid is dried by evaporation until the residual water content is less than a few percent by weight, so dried matter gradually accumulates inside the drying equipment, impeding smooth operation after long periods of operation. Must be cleaned regularly.

A conventional cleaning method will be explained. First, heat medium conduit 5
1, the waste liquid valve 30 is closed in order to clean the inside of the system from the waste liquid source valve 30 to the drying device 14 via the conduit 50, and instead, the cleaning water source valve 31 is opened and the conduit 54 is closed. The cleaning water is supplied from the liquid supply pump 10 to the drying device 14 via the conduit 50.
Supply cleaning water inside. The drive device 12 is driven in the same way as during waste liquid treatment, so the rotor blades 13 are rotating, and the washing water is spread out against the inner wall surface of the drying device 14 by the action of centrifugal force, as in the case of waste liquid, and the cleaning water is Clean distribution channels.

In the conventional cleaning method described above, the flow path of the waste liquid can be sufficiently cleaned because the amount of washing water is several times the amount of the waste liquid supplied, but the washing water collects on the cylindrical wall due to the action of centrifugal force. It is difficult to clean the center of the rotor blade 13 or every corner of the parts that make up the rotor blade, and even if the inside of the drying device 14 is filled with liquid after washing with water, the concentration of solids in the cleaning water is still low. The disadvantages were that it was expensive and that cleaning was not thorough.

[Purpose of the invention]

The present invention aims to eliminate the above-mentioned drawbacks.
To provide a cleaning method that facilitates cleaning up to the inside of a drying device of a radioactive waste liquid treatment device, minimizes the amount of cleaning water, and enables more complete cleaning in a short time.

[Summary of the invention]

The present invention allows cleaning water to flow to the central part of the rotor blade and the members that make up the rotor blade, which could not be reached by conventional cleaning methods.The main points are as follows. be.

(1) A cleaning water supply conduit 20 and a spray pipe 21 are installed in the upper part of the drying device 14 separately from the conduit 50 that is common to the waste liquid supply, and the cleaning water is uniformly supplied to the rotary blades 13. disperse.

(2) The drive device 12 is configured with a variable speed device, which enables rotation at a lower speed than during waste liquid treatment operation, reduces the load GD ² (flywheel effect of rotary blades) on the drive device, and stops and restarts rotation of the drive device. This reduces the time load and facilitates a quick restart (hot start).

Furthermore, if the number of revolutions during processing operation is N ₁ and the number of low-speed revolutions is N ₂ , the amount applied to the drive device when starting at the number of revolutions N ₁ is [GD ² ] ₁ , whereas when starting at the number of revolutions N ₂ , the [GD ² ] ₂ applied to the drive device could be reduced as shown in the following equation.

[GD ² ] ₂ = (N ₂ / N ₁ ) ₂ × [GD ² ] ₁ The frequency of restarting the motor is determined by the load GD ² , so by setting the rotation speed at restart to a low speed, The load GD ² can be reduced and restarts can be made easier.

(3) By temporarily stopping the rotor 13,
Cleaning water can be distributed all the way to the center of the rotor.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIG. The supply of the heat medium to the heat medium conduit 51 is stopped, and the waste liquid main valve 30 is closed. Next, open the washing water source valve 31,
Washing water is supplied to the drying device 14. (time T ₀ ).
It is desirable that the initial amount of washing water be approximately the same as the amount of waste liquid supplied in order to prevent thermal shock caused by rapid cooling of the drying device 14. The amount of washing water is increased at time _T1 . The amount of cleaning water should be about 3 to 5 times the amount of waste liquid supplied, and if it is too small, the cleaning effect will be poor.
On the other hand, if it is too large, the load on the drive device 12 will increase, which is not preferable. The rotation speed is lowered at time T ₂ and stopped once at time T ₃ . Next, cleaning water is sprayed from the cleaning water supply conduit 20 and the spray pipe 21 provided at the top of the drying device 14. Thereby, the cleaning water can be distributed even to the parts where the cleaning water did not flow while the rotary blade 13 is rotating. The amount of spray water depends on the amount of waste liquid supplied.
It is best to spray a 10 to 20 times larger amount of cleaning water in a short period of time.

Next, at time _T4 , the spray water is stopped and the drive device 12 is restarted, and at time _T5 , the rotational speed is set to the same rotational speed as during the waste liquid treatment operation. This is because a high speed is more effective than a low speed in order to completely clean solid matter stuck during waste liquid treatment. At time _T6 , the rotor rotates at a low speed again, at time _T7 , the supply of cleaning water is stopped, and after shaking off the water adhering to the rotor blade, it is stopped at time _T5 . In order to facilitate comparison with FIG. 2, which is an embodiment of the present invention, a conventional example is shown in FIG. 3.

In order to clarify the effects of the present invention, the solid content concentration contained in the cleaning water at each hour for the cleaning method shown in FIG. 2, which is an embodiment of the present invention, and the cleaning method shown in FIG. 3, which is a conventional example. That is, FIG. 4 shows the measurement results of the amount of washed solids. In FIG. 4, the ◯ mark and the solid line are the embodiment of the present invention, and the △ mark and the broken line are the conventional example. In the conventional example, the solid content concentration in the wash water decreases with the passage of time, and the decrease in solid content concentration continues until time _T7 . After that, in order to measure the amount of solids remaining in the drying device 14, the inside of the drying device 14 is filled with water, and the amount of solids that have adhered to every corner of the drying device 14 is dissolved and washed, and the solid content in the full-water washing water is The concentration is shown at time _T10 . On the other hand, the example of the present invention is the same as the conventional example up to time _T3 , but the solid content concentration increases again at time _T4 . That is, since the rotation was stopped from time T ₃ to T ₄ , it is shown that the attached solids are well washed away. This can also be seen from the fact that the solid content concentration after time T ₁₀ full liquid washing became lower.

〔Effect of the invention〕

As explained above, the present invention supplies cleaning water for the radioactive waste liquid treatment equipment from the spray nozzle installed at the top of the drying equipment, and causes the rotary blades to rotate and stop, thereby eliminating the solid matter that has adhered inside the drying equipment. It has the effect of sufficiently cleaning and removing the components.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a radioactive waste liquid treatment device, FIG. 2 is a state diagram explaining an embodiment of the cleaning method of the present invention, and FIG. 3 is a state diagram explaining a conventional cleaning method.
FIG. 4 is a diagram showing data on solid content concentration in washing water comparing an embodiment of the present invention with a conventional washing method. 12... Drive device, 13... Rotor blade, 14...
Drying device, 16... feeder, 19... condenser,
20...Washing water supply conduit, 21...Spray pipe.

Claims (1)

[Claims] 1. In a method for cleaning solid content of radioactive waste adhering to the inside of a drying device for drying radioactive waste in which a rotor is rotatably installed and a heating jacket through which a heat medium flows is enclosed, In addition to supplying washing water into the drying device by switching between waste liquid and washing water supplied from the liquid conduit, washing water is supplied from the spray nozzle installed at the top of the drying device, and the rotation speed of the rotary blades of the drying device is controlled. A method for cleaning a radioactive waste liquid processing equipment, characterized in that the cleaning method is variably controlled, the cleaning water is temporarily stopped during the supply of cleaning water, and the cleaning method is further rotated.