JPH04221799A - Treating method for radioactive sludge - Google Patents

Abstract

PURPOSE:To dispose radioactive sludge of a relatively high level in a form, in which the sludge can be stably reserved for a long period, through a simple process and to reduce exposure of a worker to radiation by performing pretreatment and stabilizing treatment in the same container. CONSTITUTION:Sludge 2 having relatively high radiation concentration is transferred from a sludge storage tank 1 to a treating container 3. In this case, a solidifying agent 4, such as cement and glass powder, is added and agitated and mixed. Continuous dehydrating treatment is carried out in the same container 3 by an electric permeation method. After dehydrating treatment, in case of the agent 4 being cement, it is left standing as it is to form a cement cured substance. In case of the agent 4 being glass, after stabilizing treatment (process C) of water heat synthetic reaction is carried out by means of a heater 6 and a press 7, the glass powder forms an uniform solid substance 8. As noted above, since the number of treating containers and conveyance of sludge during the treatment can be eliminated, an amount of a generating radioactive contaminated material is reduced, and a risk of a worker being exposed to radiation can be reduced.

Description

[Detailed description of the invention]

[Object of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating radioactive sludge generated from facilities such as nuclear power plants.

0002

[Prior Art] Among the radioactive sludge generated from facilities such as nuclear power plants, treatment and disposal methods have not yet been established for sludge with a relatively high radioactivity level, and it is currently stored in storage tanks within each facility. There is.

0003

[Problem to be solved by the invention] However, as the operating period becomes longer, the amount of radioactive waste stored increases, and storage space is limited, so it is difficult to treat radioactive sludge with relatively high radioactivity concentration. A method needs to be established as soon as possible.

The present invention was made in response to the above-mentioned circumstances, and is a method for solidifying radioactive sludge with a relatively high radioactivity concentration and storing it in a stable state for a long period of time. The object of the present invention is to provide a method for treating sludge with a relatively high radioactivity level, which minimizes radiation exposure by performing treatment and stabilization operations to reduce transport of radioactive sludge.

[Configuration of the invention]

[Means for Solving the Problems] That is, the radioactive sludge treatment method of the present invention involves transferring the radioactive sludge directly from a storage tank to a final storage container, pre-treating it, and then stabilizing it to solidify it. It is characterized by making it.

[0006]

[Operation] According to the present invention, since the pretreatment and stabilization treatment are performed in the same container, the process can be simplified, and the radioactivity between the pretreatment container and the pretreatment and stabilization treatment can be By eliminating the sludge transfer line,
It is possible to minimize the amount of radioactive contaminants generated and reduce the risk of radiation exposure for workers.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be described based on the drawings. Figure 1 shows an example of the radioactive sludge treatment process according to the present invention, and in the figure, reference numeral 1 indicates spent ion exchange resin and spent fuel storage pool generated in the reactor coolant cleaning system (CUW). Sludge with relatively high radioactivity concentration such as used filter aids generated in purification systems 2
This is a sludge storage tank that stores sludge. From this sludge storage tank 1, sludge 2 having a concentration within a range that can be transported by pump (normally 5 wt% concentration, maximum 10 wt% concentration) is transferred to a processing container 3. At this time, a solidifying agent 4 such as cement or glass powder is also added and stirred and mixed uniformly (Step A), and then continuously dehydrated in this processing container 3 (Step B).
. Such in-container dehydration methods include the electroosmosis method, which is carried out by inserting a module 5 that integrates electrodes and membranes into the container, and the dehydration method, which is carried out by inserting a membrane filter such as a hollow fiber membrane filter. There are ways to do this. Which one to select is based on the properties of the sludge liquid; the former is selected for sludge that is easy to filter, and the latter is selected for sludge that is difficult to filter. As an index of ease of filtration, there is filtration specific resistance. The dehydration treatment (step B) by such a method is performed continuously while supplying the sludge 2 until the inside of the treatment container 3 is filled.

[0008] After the dehydration treatment, if the solidifying agent 4 is cement, if it is left as it is, a cement solidified body will be formed. However, if the main component of the sludge is an ion exchange resin, cement may not be suitable, and a method of adding glass powder and hydrothermally solidifying the sludge is effectively used. In the case of hydrothermal solidification, a thick walled container is used as the processing container 3, and after the dehydration treatment, for example, a stabilization treatment step (step C) of the hydrothermal synthesis reaction (hot press) using a heater 6 and a press 7
) to form a homogeneous solidified body 8 in which the resin is confined in a glass matrix. In this case, the thick-walled container has the effect of also functioning as a shielding container.

[0009] As an experiment, a simulated sludge of powdered ion exchange resin was dehydrated in a container and solidified by hydrothermal reaction. The results will be explained next. Experimental Example 1 As shown in FIG. 2, a hollow fiber membrane filter 11 was installed in a processing container with a diameter of 80 mm, and a dehydration treatment was performed on simulated sludge 12 containing 0, 5, and 20% by weight of cladding at a reduced pressure of -510 mmHg. Ta. The water content after each dehydration process is shown in Figure 3, with the height direction position in the processing container taken as the vertical axis, and the solid line a in order from the one with the least amount of crud.
, b, and c. In addition, in FIG. 2, the measurement points at which the water content was measured are indicated by x marks. As is clear from this figure, the hollow fiber membrane filter was able to sufficiently dehydrate the container.

Experimental Example 2 Dehydration in a container was carried out by electroosmosis using the apparatus shown in FIG. As shown in this figure, a simulated sludge 26 When the sludge was dehydrated, a dehydrated liquid 27 was collected in the center of the treatment container, and the sludge after treatment had a moisture content as shown in FIG. In the figure, the solid line d indicates the measured value at the center of the sludge in the container, and the solid line e indicates the measured value at the outside of the sludge. Further, a chain line f indicates a height position corresponding to the upper surface of the sludge in the container in FIG. As is clear from this test result, it can be seen that sufficient dehydration can be achieved by electroosmosis.

Experimental Example 3 When hydrothermal solidification of sludge was attempted using a small-scale device with a diameter of 2 cm using the blending ratio shown in the following table, it was possible to form a solidified material with sufficiently high compressive strength as shown in the table. .

[0012] As is clear from the above explanation, sludge with a relatively high radioactivity level can be dehydrated and reduced in volume in a container, and then solidified quickly in the same container. There is no need to prepare a separate dewatering device, a sludge transfer line between the dehydrating device and the solidification device, and associated equipment such as pumps, which reduces the generation of secondary radioactive waste and reduces the amount of radiation exposure for workers. It is possible to reduce the

[0013]

Effects of the Invention As explained above, according to the present invention, relatively high level sludge can be processed into a form that can be stored stably for a long period of time through a simple process, thereby reducing the radiation exposure of workers. It is possible to reduce the

[Brief explanation of the drawing]

[Fig. 1] An explanatory diagram showing an embodiment of the radioactive waste sludge treatment system according to the present invention.

[Figure 2] Cross-sectional view of a processing container equipped with a hollow fiber membrane filter

[Figure 3] Graph showing the water content of sludge after dehydration using the hollow fiber membrane filter in Figure 2

[Figure 4] Cross-sectional view of a processing container equipped with an electroosmosis device

5 is a graph showing the water content of sludge after dehydration treatment by the electroosmosis device of FIG. 4. FIG.

[Explanation of symbols]

1...Sludge storage tank 2…Sludge 3...Processing container 4...Solidifying agent 5...Module 6...Heater 7...Press 11...Hollow fiber membrane filter 12…Simulated sludge 21...Anode 22...Cathode 23...Electrode liquid 24...Cation exchange membrane 25... Porous membrane 26…Simulated sludge 27…Dehydrated liquid

Claims (1)

[Claims] Claim 1: When solidifying radioactive sludge generated from a radioactive substance handling facility, the radioactive sludge is directly transferred from a storage tank to a final storage container, pretreated, and then stabilized to form a solidified body. A method for treating radioactive waste sludge, characterized by: