JPH0242543B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the cleaning of ion exchange resins used in the treatment of radioactive liquids, and more specifically, the present invention relates to the cleaning of adhering and adsorbed solids on the ion exchange resins used in the treatment using as little waste liquid as possible. The present invention relates to a method and apparatus for performing the process under evacuation.

Suspended solids contained in the primary cooling water of a nuclear power plant are closely related to suppressing the radiation dose in the plant, reducing radiation exposure during work, maintaining the integrity of the fuel assembly, etc. Ionic components and suspended solids are often removed using a condensate desalination device. The ion exchange resin used for the condensate desalination treatment of the primary waste water is physically cleaned of adhering and adsorbed solids prior to chemical regeneration in order to regenerate the ion exchange capacity. Reducing the amount is an extremely important issue in order to reduce processing time, radiation exposure, and running costs of waste liquid treatment equipment.

Conventionally, physical cleaning of solids attached to and adsorbed on ion-exchange resins involves vigorous mixing (scrubbing) with air in the presence of cleaning water in a tank, and then backwashing by pumping water into the resin layer from the bottom. This is done by repeatedly overflowing the resin layer, and finally draining the water on the resin layer from the extraction pipe, and in this method, a large amount of waste liquid is discharged.

The present invention focuses on the application of resin during the physical cleaning process.
It is an object of the present invention to provide a method for cleaning ion exchange resins that reduces the amount of cleaning liquid containing adsorbed solids as much as possible. Another object of the present invention is to provide an apparatus for cleaning resin while reducing the amount of discharged liquid as much as possible.

According to the present invention, the ion exchange resin on which suspended solids have been attached and adsorbed is scrubbed, the water in which the solids separated from the resulting resin are suspended is filtered, and the filtered water is refluxed and used for scrubbing the resin. When used again (or repeatedly), the solids captured in the filtration device are backwashed and discharged as a relatively highly concentrated suspension, reducing the running cost of the waste liquid treatment device and shortening the processing time. , it becomes possible to reduce the amount of radiation exposure.

The present invention will be explained below with reference to the drawings. FIG. 1 is an explanatory diagram of an apparatus for carrying out the method of the present invention. Contaminated ion exchange resin used in the condensate desalination equipment is introduced into a tank 1 equipped with a withdrawal pipe 2 and a water and air dispersion pipe 3, and water and air are passed from the dispersion pipe 3 to the tank 1 through valves 4 and 5. to scrub the resin. Next, after stopping the introduction of water and air, the water on the resin layer is discharged from the extraction pipe 2 to the filtration device 9. The extraction tube 2 has a structure that does not allow ion exchange resin of normal particle size to pass through, but allows suspended solids much smaller than normal particle size to pass through.
Further, the extraction pipe 2 is attached relatively close to the separation surface between the resin and water in the tank. The filtration device 9 includes a water supply device 8 installed between the extraction pipe 2 and the filtration device 9;
For example, it is preferable to use a booster pump. Any suitable device can be used as the filtering device 9, and for example, an electromagnetic filter or an edged disc filter can be used.

The water that has passed through the filtration device 9 and from which suspended solids have been removed is returned to the tank 1. The reflux water is introduced into the space of the tank 1 or the lower resin layer via the pipe 11 or 12, for example. The reflux water may also be divided and fed simultaneously through pipes 11 and 12. It is preferable that the reflux water is sent in such a manner that it does not mix with the water held in the tank 1, and that an equivalent amount of the water held in the tank 1 after scrubbing is passed through the filtration device 9 and refluxed so that the water held in the tank 1 circulates once. is preferred.

Then, the reflux to the filtration device 9 is stopped, and the tank 1
After blowing air through the dispersion tube 3 and scrubbing again to further release the resin-attached and adsorbed solids into the water, the scrubbing is stopped, and the contaminated water is drawn out from the tube 2 and passed through the filtration device 9 into the tank as described above. The equivalent amount of retained water is refluxed. The above operation is repeated until the solid matter attached to and adsorbed on the resin is washed to a desired extent.

During the above operations, if the differential pressure between the inlet and outlet of the filtration device reaches the operating control value due to the captured solids (when or when the inflow from the tank is stopped), water and air are introduced from the conduit 10 to the filtration device 9. The solids captured on the filter are separated, backwashed, and discharged. The effluent resulting from backwashing of the filtration device 9 is discharged as a relatively highly concentrated suspension, and the amount discharged is much smaller than the effluent discharged in the conventional method. The discharged suspension is sent to a waste liquid treatment system and undergoes necessary treatment.

If the amount of cleaning water in the tank 1 decreases during the above operation, water is replenished into the tank 1 together with air during scrubbing or separately.

In the above explanation, before the filtration operation, scrubbing that supplies water and air or scrubbing that supplies only air is performed to remove solids from the ion exchange resin. It is also possible to supply only water to float and disturb the ion exchange resin, thereby removing the solid content. In this case, water supplied into the tank 1 from the lower part of the tank 1 rises up the tank and reaches the extraction pipe 2.
A part or all of it is extracted from the filtration device 9.
guided by. The water from which the solid content has been removed by the filtration device 9 is returned to the tank 1, and a portion of the water extracted from the extraction pipe 2 for floating and stirring the ion exchange resin is guided to the filtration device 9. In this case, the remaining water is circulated to the lower part of the tank 1 via the pipe 13. In this way, the floating and
The flow rate of water required for agitation does not have to be the same as the filtration flow rate of the filtration device, and therefore a large flow rate of water can be ensured for floating and agitating the ion exchange resin. Furthermore, by circulating the remaining water to the lower part of the tank 1 as described above, the filtration device can be made smaller.
The entire device becomes compact. Therefore, the total amount of water retained is reduced.

In this way, if the solid content is removed by scrubbing without using air, that is, by supplying water from the bottom of the tank to suspend and disturb the ion exchange resin, the amount of air discharged from the tank will be reduced. This is preferable because it reduces the load on the filter that removes radioactive substances from the air.

The resin cleaning operation described above can be performed manually, but it can also be performed automatically using a program timer, microcomputer, sequencer, etc. It is also possible to simultaneously and continuously perform the resin scrubbing operation and the filtration and reflux operation of the resulting contaminated water.

Example A contaminated ion exchange resin was cleaned using the apparatus shown in FIG. 3.9 ^{m3 of} contaminated cation exchange resin and 2.2 m3 of anion exchange resin used for condensate desalination treatment
After introducing the mixed resin with m ³ into the tank 1 and introducing an appropriate amount of water from the washing water introduction pipe 6, water and air were introduced into the tank from the dispersion pipe 2 through the valves 4 and 5, and the water and air were poured into the tank from the dispersion pipe 2.
The resin was scrubbed for 15 minutes. At this point, the tank held approximately ^10m3 of water. The water in which solids separated from the resin are suspended is discharged from the extraction pipe 2, passed through a vacuum filter (edge disk filter) via a booster pump 8, and the filtered water is sent to the pipe 1.
1 and refluxed into the tank. After approximately 10 m ³ of water has passed through the filter, the flow back to the filter is stopped and air is introduced into the tank 1 through the dispersion tube 3 for scrubbing, and then the suspended contaminated water generated as described above is passed through the filter 9. It refluxed. After repeating the above-mentioned scrubbing and filtration operations, air and water were passed through the filter for backwashing, and the solid content of the effluent was measured. The solid content was iron oxides and hydroxides, and the amount of discharged liquid was approximately ^45m3 , and a total of approximately 5.9Kg as Fe was discharged.

The same amount of condensate water as above was passed through the ion exchange resin mixture used in the above test to wash the contaminated resin according to conventional methods. In this method, the resin introduced into the tank was scrubbed with water and air for about 6 minutes, and the washing water in which solids were suspended was overflowed by backwashing and then flowed out from the extraction pipe. The above scrubbing and backwashing was performed nine times. The amount of liquid discharged each time is approximately 10
It was ^m3 . The total amount of discharged liquid was approximately ^100m3 , and a total of approximately 5.7Kg of Fe was discharged.

As a result of the above test, it was found that the method of the present invention can remove attached and adsorbed solids when cleaning ion exchange resins with a much smaller amount of waste liquid discharged than the conventional method. This shows that it will be much easier.

Although the above description relates to cleaning ion exchange resins used in the treatment of radioactive liquids, it is of course possible to apply the method of the present invention to cleaning ion exchange resins used in the treatment of other fluids.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the ion exchange resin cleaning apparatus of the present invention. 1...tank, 2...extraction pipe, 3...dispersion pipe, 7...vent, 8...water supply device, 9...filtration device, 13...piping.

Claims (1)

[Claims] 1. In a method for cleaning an ion exchange resin contaminated with suspended solids in water to be treated, water containing suspended solids separated from the resin by scrubbing is mixed with the resin and water in a tank. The solids are extracted from a extraction pipe installed relatively close to the separation surface, a portion is passed through the filtration device and refluxed, and the remainder is circulated to the lower part of the tank.The solids captured by the filtration device are backwashed in the filtration device. A cleaning method for ion exchange resin, which is characterized by discharging it out of the system. 2. Scrubbing the ion exchange resin in the presence of water by introducing water and air or air from the bottom of the tank,
The resulting solid-suspended water is passed from the extraction pipe through the water supply device, part of it is passed through the filtration device and returned to the tank, and the remainder is circulated to the bottom of the tank, where the above-mentioned scrubbing and filtration are repeated. A method according to claim 1. 3. The method according to claim 2, wherein after scrubbing, the equivalent amount of water held in the tank is recycled through a filtration device. 4. The method according to claim 1, wherein the filtration device is backwashed by supplying water and air when the differential pressure between the inlet and outlet of the filtration device reaches an operational control value. 5 A tank equipped with a withdrawal pipe and a dispersion pipe, a filtration device equipped with a backwash mechanism that communicates with the withdrawal pipe via a water supply device, and in which a portion of the withdrawn liquid communicates with the space of the tank, and the remainder of the withdrawn liquid. An ion exchange resin cleaning device consisting of a circulation path to the bottom of the tank. 6. The device according to claim 5, wherein the filtration device is an electromagnetic filter. 7. The device according to claim 5, wherein the filtration device is an etched disk filter.