JPS5822999B2 - Method for recycling filter material used to filter radioactive wastewater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for regenerating fj material used for r-filtration of radioactive wastewater, and more specifically, the present invention relates to a method for regenerating fj material used for r-filtration of radioactive wastewater. The present invention relates to a method of regenerating sweat material by immersing sweat material in an aqueous hydrogen peroxide solution.

In nuclear power plants using light water-cooled nuclear reactors L-W-H, especially power plants using boiling-type nuclear reactors B-W-H, corrosion of equipment materials occurs in the reactor water that circulates between the reactor and the power generation turbine. Insoluble solid particles (usually called cladding, henceforth referred to as cladding) whose main component is iron oxide are generated, and when they are irradiated with neutrons in the reactor core, they only increase the radioactivity level of the reactor water. Since the crud is deposited on the surface of the reactor fuel assembly and within the reactor water circulation system, a treatment facility is required to remove such crud from the reactor water.

At present, such processing facilities are unable to process cellulose powder, etc.
Either the cladding is filtered and separated using a pre-coating force method using a filter material, or a plate-shaped material having flow holes with an equivalent diameter of 10 microns or more, for example, a constant diameter of 0.4 to 3.0 microns, is used. A membrane filter with a thickness of 10 to 20 microns is used, which is made of plastic and has a large number of circular pores with a uniform diameter cut almost perpendicular to the membrane surface with an aperture ratio in the range of 10 to 20%. A method is adopted in which the cladding is filtered and separated.

In this case, in the latter method, by backwashing the crud deposited on one side of the material as a result of the p-overflow operation, the 1-overfunction of the 1-material can be restored, so a new f'' material is used each time. One material can be used repeatedly without having to be replaced.

However, if the above material is used for a long period of time,
Amorphous and highly sticky substances, such as microorganisms, which are difficult to remove by backwashing operations, etc., gradually adhere to and accumulate on the surface of the material and the flow holes, resulting in the product being replaced with a new material. It is necessary to replace the material or to regenerate it by some method.

In the past, organic matter adhered to the product and the f-hyperfunction was lost1.
Although ultrasonic cleaning methods are known as methods for recycling materials, they cannot be said to be very effective in removing microorganisms attached to P materials.

In view of the current situation, the inventors of the present invention, Nagisa et al., conducted extensive research into a method for completely or almost completely removing organic matter such as microorganisms adhering to the p-material and restoring its first function. The present inventors have discovered that a method of treating the inside of the body is most suitable, and has accomplished the present invention.

That is, the method according to the present invention for regenerating a material used to filter and separate solid particles suspended in radioactive wastewater is to recover the P material to which organic matter such as microorganisms has adhered at room temperature to 70°C.
The treatment is characterized by being immersed in an aqueous hydrogen peroxide solution maintained at a temperature range of 0.degree. C. for a certain period of time.

In this case, it is not clear how hydrogen peroxide acts on organic matter such as microorganisms, but its strong oxidizing action alters the organic matter such as microorganisms and makes it easy to separate from the material. In extreme cases, it may be due to oxidative decomposition.

The hydrogen peroxide aqueous solution used in the method of the present invention may be commercially available, but it is desirable to select one having a hydrogen peroxide concentration in the range of 3 to 30% by weight in relation to the treatment concentration.

The treatment temperature can be selected from the range of room temperature to 70°C, but is preferably in the range of 40 to 60°C.

Hereinafter, the constituent elements and effect requirements of the present invention will be explained in more detail along with the drawings.

FIG. 1 is a flow sheet showing one embodiment of the method of the present invention, where T1 + T2 and T3 indicate a storage tank for radioactive wastewater, a treatment tank, and a storage tank for aqueous hydrogen peroxide solution, respectively.

In FIG. 1, the radioactive wastewater containing crud is introduced from the radioactive wastewater storage tank T1 into the treatment tank T2 via line 1 by pump P1 and does not substantially contain crud while passing through P material F1. It becomes waste water and is taken out from the line 2.

If such operations are continued for a certain period of time, crud will accumulate at the bottom of the material F1 and the material will lose its functionality.
By stopping the introduction of radioactive wastewater and injecting compressed air from line 3, the treatment liquid remaining in the treatment tank is rapidly flowed in the opposite direction to the direction of water passing through the stream, thereby reducing the membrane surface of one material. The crand adhering to the material is washed away and the superfunction of the material is restored.

As a result, the obtained waste liquid flows out of the system through line 5, and is subsequently treated by a known cement solidification method, annuphalt solidification method, or the like.

Normally, if such a backwashing operation is performed, the above-mentioned 1st material's 1st function will be restored to its original state, but if the 1st material F1 is used for a long period of time, the surface and flow holes of the 1st material will be damaged. As shown in FIG. 2, organic substances S1 such as microorganisms are attached, and it becomes difficult to restore the primary function even if the above-mentioned backwashing operation is repeated.

If it is recognized that the organic matter S1 has adhered to the first material F1 in this way, an aqueous peroxide solution is introduced into the treatment tank T2 from the hydrogen peroxide solution storage tank T3 through the line 6, and according to the present invention. Process according to method.

In this case, the hydrogen peroxide aqueous solution in the treatment tank T2 is heated by the heater H.
1 to room temperature to 70°C, preferably 4.
The material is maintained at a temperature of 0 to 60° C. and left for a period of time (approximately 0.5 to 1 hour) such that organic substances such as microorganisms are completely or almost completely removed from the material.

Next, the temperature of the hydrogen peroxide aqueous solution is set to 70 to 80°C,
After the hydrogen peroxide is completely decomposed into water and oxygen, backwashing is performed again to clean the inside of the treatment tank T2.

Incidentally, at this time, oxygen generated by the decomposition of hydrogen peroxide is released into the atmosphere through line 1.

As described above, according to the method of the present invention, there is no need to replace tear material that has lost its drainage function due to attachment of organic matter such as microorganisms with a new one each time, so the amount of radioactive secondary waste generated is small. It is also extremely advantageous economically.

It is also conceivable to use a sodium hypochlorite aqueous solution instead of the hydrogen peroxide aqueous solution according to the present invention, but since these will eventually become radioactive secondary waste that requires post-treatment, the present invention is not applicable. It is not preferable to apply it to such an industrial scale treatment process.

On the other hand, the hydrogen peroxide aqueous solution according to the present invention easily decomposes into water and oxygen, and therefore does not generate radioactive secondary waste.

Furthermore, according to the method of the present invention, it is possible to use a low concentration hydrogen peroxide aqueous solution that is commercially available at a relatively low price.
It is not only extremely economical, but also relatively easy to handle.

Example 1 (Experiment 1) Simulated wastewater containing 20"19/l of iron oxide fine particles in sterile distilled water was prepared using Nuclearpore's Nuclepore Co., Ltd., which has many flow holes (opening ratio 20%) with an average diameter of 1 micron. The mixture was introduced at a constant speed into a processing tank equipped with a polycarbonate membrane filter, and the above-mentioned flushing operation was performed, and the time until the pressure loss reached 2 Kt/cr/1 was measured.

Next, the backwashing operation was performed for a certain period of time to restore the flushing function of the lachrymal material, and then the flushing operation was performed again.

After repeating this swamp-backwashing operation 20 times and measuring the time required for the pressure loss during the swamping operation to reach 2 KP7'crA, the results shown in A in Table 1 were obtained. It was done.

As is clear from this result, it was recognized that the drainage function of each lachrymal material was almost constant.

(Experiment 2) The simulated wastewater containing 105 microorganisms and 6 microorganisms was further introduced into the treatment tank at a constant rate into the simulated wastewater described in Kl, and the swamp-backwashing operation was repeated. As in case 1, the time required for the pressure loss to reach 2yI in the overflow operation was measured, and the results shown in B in Table 1 were obtained.

As is clear from these results, a large amount of microorganisms were attached to the lachrymal material used in the 6th rinsing operation, and its rinsing function was about 30% lower than that of the lachrymal material used in the first rinsing operation. 1/2
It was recognized that .

(Experiment 3) After backwashing the treatment tank used in Experiment 1 and Experiment 2 above, a room temperature hydrogen peroxide aqueous solution (hydrogen peroxide concentration 15% by weight) was injected into the treatment tank, After the tear material was soaked for about 16 hours, the temperature of the aqueous hydrogen peroxide solution was raised to 80°C to completely decompose the remaining hydrogen peroxide.

Next, after extracting and cleaning the solution in the treatment tank, the simulated wastewater used in Experiment 2 was introduced at a constant rate, and as in Experiment 2, the pressure loss in each r-over operation was When the time taken for each to become saturated was measured, the results shown in B of Table 1 were obtained.

As is clear from these results, the lacrimal material immediately after being treated with the hydrogen peroxide aqueous solution improved its rinsing function until it had almost the same performance as the new lacrimal material used for the first rinsing operation in Experiment 2. was found to be recovering.

However, it was observed that when such one material was used repeatedly without being treated with an aqueous hydrogen peroxide solution, its permeation function tended to gradually decrease as in the case of Experiment 2.

(Experiment 4) After backwashing the treatment tank used in Experiment 3 above, an aqueous hydrogen peroxide solution was injected into the treatment tank, and the tear material was washed under the same conditions as in Experiment 3. was played.

Next, in the same way as in Experiment 3, we repeated the wash-backwash operation and measured the time required for the T torque loss to reach 2 hits in each 1-pass operation. The results shown are obtained.

As is clear from these results, it was confirmed that if lachrymal material is regenerated by the method of the present invention, it is possible to use the p material any number of times.

Example 2 Eight treatment tanks shown in Experiment 1 of Example 1 were prepared, and the simulated wastewater used in Experiment 2 was introduced into each treatment tank at a constant rate, and filtered in the same manner as in Ito Experiment 2. - The backwashing operation was repeated 6 times and the time X until the pressure loss in the first 1st pass operation reached 2 hits was measured.

Next, after backwashing each treatment tank, a hydrogen peroxide aqueous solution having a hydrogen peroxide concentration of 5 to 30% by weight is injected into the treatment tanks, and the method of the present invention is carried out under the conditions shown in the second stage. Processing was performed.

Next, after extracting and cleaning the solution in each treatment tank,
The above-mentioned simulated wastewater was introduced at a constant rate, a one-pass operation was performed, and the time Y until the pressure loss in each treatment tank reached 2 or more was measured.

Based on these results, the extent to which the sewage function of one material installed in each treatment tank had been recovered was determined, and the results shown in Table 2 were obtained.

In addition, the "recovery rate of overflow function" shown in Table 2 refers to 1 after regeneration.
The value obtained by dividing the filtration time Y when performing the first filtration operation using the wood by the filtration time X when using new offshore wood is expressed as a percentage.

As is clear from the above results, the method of the present invention can sufficiently restore the filtration function of a material to which organic compounds have adhered, and it is hoped that the method of the present invention can be used at a temperature of 40 to 60°C. It has been found that it is most preferable to carry out

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing one embodiment of the method of the present invention, and FIG. 2 is a partial cross-sectional view of one material used in the method of the present invention, as well as showing the form of attachment of organic compounds. be. T1...- Radioactive wastewater storage tank, T2...
Processing tank, T3...Hydrogen peroxide aqueous solution storage tank, P
l...pump, Hl...heater, Fl
...1 material, Sl...organic compound.

Claims (1)

[Claims] 1. A method for regenerating sweat material that is used to filter and separate solid particles suspended in radioactive wastewater, and which has lost its filtering function due to the attachment of organic matter to its surface. A method for regenerating P material used for filtration of radioactive wastewater, characterized in that the sweat material is treated by immersing it in a hydrogen peroxide aqueous solution maintained at room temperature to 70° C. for a certain period of time. 2. The regeneration method according to claim 1, wherein the radioactive wastewater is wastewater discharged from a facility of a soft water-cooled nuclear power plant. 3. The regeneration method according to claim 1, wherein the solid fine particles are corrosion products containing iron oxide as a main component. 4. The recycling method according to claim 1, wherein the material has flow holes having an equivalent diameter of 10 microns or less. 5. The P material is a film-like body made of plastic as a base material, in which a large number of circular holes having a constant and substantially uniform diameter of 0.4 to 3.0 microns are bored substantially perpendicular to the film surface. The regeneration method described in Section 4. 6. The recycling method according to claim 5, wherein the P material is a polycarbonate film having a thickness of 10 to 20 microns. 7. The recycling method according to claim 5, wherein the P material has an aperture ratio of 10 to 20%. 8. The regeneration method according to claim 1, wherein the organic matter is a microorganism. 9. The regeneration method according to claim 1, wherein the hydrogen peroxide aqueous solution is maintained at a temperature of 40 to 60°C. 10. The regeneration method according to claim 9, wherein the immersion time is in the range of 0.5 to 1 hour. 11 The hydrogen peroxide concentration of the hydrogen peroxide aqueous solution is 3 to 30
% by weight. 12 Hydrogen peroxide aqueous solution is 70-80% after soaking the sweat material.
The regeneration method according to claim 1, wherein the regeneration method is decomposed at .degree.