JP2544360B2 - Water filtering device for nuclear reactor plant and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a water filtration device for a nuclear reactor plant and a method for manufacturing the same, and particularly to reactor water and condensate water for a reactor using a hollow fiber membrane in a filtration module. The present invention relates to a water filtration device suitable for purification of water and a manufacturing method thereof.

[Conventional technology]

Hollow fiber membrane filters have hitherto been used in various ways such as production of high-purity water, sterile water, blood purification, and artificial organs such as artificial kidneys. In recent years, attention has been paid to its application to purification equipment for condensate and waste water of thermal power plants, nuclear power plants.

Thermal power, nuclear power plants, plant components, and
To maintain the soundness of the equipment, the quality of the water used is controlled. In particular, in nuclear power plants, generation and suppression of corrosion products and their removal are carried out as a measure to reduce radioactivity. This corrosion product is generated from structural materials and piping,
It is called "clad" with iron oxide as the main component. BACKGROUND ART A nuclear power plant uses a filter device to separate and remove radioactive waste liquid generated and corrosion products suspended in condensate of a primary cooling system.

Conventionally, a method using a precoat type filter such as a powder ion exchange resin has been used as this filtering device.

However, there is a problem that a large amount of resin waste is generated in the filtration method using the powder ion exchange resin as the precoat material.

Therefore, in recent years, a method of separating and removing suspended matters in wastewater and condensate with a hollow fiber membrane filter using a precoat material has been applied. The outer diameter of the hollow fiber membrane is about 1 to 0.4 mm,
It is made of a hollow porous polymer material having an inner diameter of about 0.5 to 0.2 mm and has pores with a diameter of 0.1 μm or less. For example, as described in JP-A-56-76208 and JP-A-59-4403, a hollow fiber membrane filter is used to filter about 100 hollow fiber membrane modules filled with thousands of hollow fiber membranes. It is installed in the tower, and the water to be treated is introduced into the filtration tower and permeates into the hollow part of the hollow fiber membrane. FIG. 2 schematically shows the pattern of filtration and trapping of the hollow fiber membrane. The water to be treated 14 is the hollow fiber membrane 8
Permeate from the outside to the hollow part 16. At that time, the cladding was captured on the membrane surface and the pores 13, and the permeated water from which the suspension was removed
15 is led to the exit of the permeation tower.

The pressure difference between the inlet and the outlet of the hollow fiber membrane filter, that is, the filtration pressure difference increases with the trapping of this cladding, and filtration is performed until a predetermined value is reached, and thereafter,
Backwashing is performed to remove the trapped adhering substances 9 from the surface.

FIG. 3 shows a schematic diagram of backwashing. For backwashing, air bubbling 11 on the outside of the hollow fiber membrane, supplying pressurized backwash water 18 to the hollow portion of the hollow fiber membrane, peels the trapped deposits, and the stripped deposits 10 together with the permeated backwash water 17. Is discharged.

Then, the water to be treated is supplied again, and the above-mentioned filtration and backwashing are repeated. Even if the backwashing is performed, the filtration pressure difference does not return to the pressure difference before the filtration, but gradually increases. When the filtration pressure difference reaches the allowable pressure difference, the hollow fiber membrane is replaced.

[Problems to be solved by the invention]

The above-mentioned prior art does not consider the point of film contamination and has a problem that the useful life of the film is short.

FIG. 4 shows the pattern of the film after backwashing. Even after backwashing, some of the cladding remained on the membrane, leaving residue 12 and causing membrane contamination.

This membrane contamination causes an increase in filtration differential pressure because it closes pores having a diameter of 0.1 μm or less formed in the membrane,
There was a problem that the operation time until backwashing, that is, the filtration life was shortened, the backwashing frequency was increased, and the useful life of the membrane was shortened. Hollow fiber membranes used in nuclear reactor plants must be treated as radioactive waste. If the membrane replacement period can be extended, the amount of radioactive waste can be reduced.

An object of the present invention is to provide a water filtration device for a nuclear reactor plant that can reduce the amount of used hollow fiber membranes generated.

[Means for solving problems]

The above object is achieved by making the hollow fiber membrane electrically conductive, setting its specific resistance to 50 kΩcm or less, and relaxing the adhesive force based on the electrostatic force between the hollow fiber membrane and the deposit.

Porous polymer material constituting the hollow fiber membrane, for example, cellulose-based, polyolefin-based, polysulfone-based, polyvinyl alcohol-based or the like to form a conductive substance having a specific resistance of 10 kΩcm or less on the surface, or immersed inside As a result, the hollow fiber membrane has a specific resistance of 50 kΩcm or less.

The conductive hollow fiber membrane has a specific resistance of 1 Ωcm.
The following metals and metal compounds, for example, Ag, Au, Al, Cu, Pt, Pd
A simple substance such as, a compound, or a compound with a specific resistance of 10 kΩc
Conductive polymers of m or less, for example, polyacrylamide, polyethylene oxide, sulfonates, and the like, and a substance having an ion-exchange group-providing ability, for example, sulfuric acid, etc., including vapor deposition including the sputtering method, powder, paste, or A conductive substance is formed on the surface of the polymer material or dipped inside by applying or dipping it in the form of a solution.

It is most preferable to deposit a conductive substance by a sputtering method or the like because it does not block the conductivity and pores on the surface of the hollow film.

[Action]

Generally, a hollow fiber membrane has an electric insulating property and therefore tends to accumulate an electric charge and become charged. FIG. 5 shows the zeta potential of the hollow fiber membrane. From this, the condensate of the nuclear power plant,
It can be seen that the membrane has a negative charge under PH5-8 under reactor water conditions. In addition, under the same conditions, the suspended particles in water are positively charged, and electrostatic power based on Coulomb's law is generated between the film and the suspension, and the film and the deposit are separated from each other. Increase the adhesive strength of.

Since the hollow fiber membrane according to the present invention has conductivity, the adhesive force between the membrane and the adhered matter is relaxed by discharging the electric charge by grounding the hollow fiber membrane filter supporting member or the like, and the residual adhered matter is removed. And the filtration life can be extended.

〔Example〕

<Example 1> Platinum-vanadium was used as a target, and an ionic current of 15 was used.
As mA, ion sputtering was performed for 4 minutes, and platinum-vanadium was vapor-deposited on the entire outer surface of the non-conductive hollow fiber membrane to form a conductive hollow fiber membrane.

The thickness of the vapor-deposited film is several tens of liters, and pores of about 0.1 μm in the hollow fiber membrane are not blocked.

The non-conductive hollow fiber membrane used was a polyethylene-based membrane
Asahi Kasei) Outer diameter 1.2mm, inner diameter 0.6mm Polyvinyl alcohol (made by Kuraray Co., Ltd.), outer diameter 0.8mm, inner diameter 0.4mm Cellulose acetate (made by Toyobo Co., Ltd.) outer diameter 0.4mm, inner diameter 0.2mm Then, water filtration and backwashing were performed with the apparatus shown in FIG.

In FIG. 1, the conductive hollow fiber membrane 1 was set in the filtration device, grounded from the top of the membrane, and fed from the treated water inlet 3 to Fe.
(OH) ₃ containing 10 ppm of iron compounds as the main component, water having a dissolved oxygen concentration of 50 ppb or less and a water temperature of 30 to 35 ° C has a linear flow velocity of 0.15 m / h.
And the suspension is filtered by a membrane and then discharged from the treated water outlet 4. Filtered differential pressure stop is a 0.5 kg / cm ² large summer cod water passage from the initial pressure difference, to flow back to the backwash water inlet 5 than the 0.3 kg / cm ² pressurized water, air supply from the air inlet 6, the air scrambler Bing Then, the backwash water is discharged from the backwash water outlet 7 together with the peeled deposits.

After backwashing, the hollow fiber membrane filter was taken out and the residual deposit was analyzed. The results are shown in Table 1.

According to the present example, the amount of residual deposits causing the film contamination is reduced by 65 to 34% as compared with the untreated one.

<Example 2> Platinum-vanadium was used as the target, and the ion current was changed.
Ion sputtering for 4 minutes at 15 mA, Example 1
The same type of hollow fiber membrane used in
Vanadium was vapor deposited.

In the same manner as in Example 1, water passing, filtration and backwashing were performed,
After backwashing, the amount of residual deposit was analyzed and the results shown in Table 2 were obtained.

According to this example, the amount of residual deposits is reduced by 62 to 32% as compared with the untreated one.

<Example 3> About 5 g / m ^{2 of} silver paste containing silver powder of 0.1 to several microns was applied to the outer surface of the same type of hollow fiber membrane as that used in Example 1, and the same operation as in Example 1 was performed. At this point, water was passed through, filtered, and backwashed, and after the backwashing, the amount of residual adhered substances was analyzed and the results shown in Table 3 were obtained.

According to this example, the amount of residual deposits is reduced by 70 to 45% as compared with the untreated one.

<Example 4> A polyacrylonitrile 5% solution was added as an antistatic agent,
The same type of hollow fiber membrane as that used in Example 1 was immersed for 15 hours to make it conductive.

After the immersion, water was passed through, filtration, and backwashing were carried out in the same manner as in Example 1 without drying, and the amount of the remaining deposits after the backwashing was analyzed to obtain the results shown in Table 4.

According to this example, the amount of residual deposits is reduced by 52 to 30% as compared with the untreated one.

<Example 5> A hollow fiber membrane of the same type as that used in Example 1 was immersed in a hot concentrated sulfuric acid solution at 100 ° C for 3 minutes to subject the surface to sulfonation.

As a result, SO ₃ H groups, which are ion-exchange groups, were provided on the surface of the film.

In the same manner as in Example 1, water passing, filtration and backwashing were performed,
After backwashing, the amount of residual deposit was analyzed and the results shown in Table 5 were obtained.

According to this embodiment, the amount of the remaining deposits is reduced by 17 to 7% as compared with the untreated one.

<Example 6> FIG. 6 shows a comparison of properties by conducting a filtration test using an untreated polyethylene-based hollow fiber membrane filter and a platinum-vanadium vapor-deposited and conductivity-treated one. Water was passed through, filtered, and backwashed in the same manner as in Example 1, and the procedure was repeated until the filtration differential pressure reached an allowable differential pressure. As a result, the time until the replacement time of the membrane at which the filtration pressure difference reaches the allowable pressure difference, that is, the service life becomes a few times longer due to the electroconductivity treatment.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, the water filtration apparatus of a nuclear reactor plant which can reduce the generation amount of a used hollow fiber membrane can be provided.

[Brief description of drawings]

FIG. 1 is a system diagram of a filtration device using a hollow fiber membrane that has been subjected to electroconductivity treatment according to an embodiment of the present invention, and FIGS. 2, 3, and 4 are filtration capture and backwashing using the hollow fiber membrane, FIG. 5 is a schematic diagram showing the attachment of residual deposits, FIG. 5 is a diagram showing a zeta potential curve of a hollow fiber membrane, and FIG. 6 is a diagram showing effects of the present invention. 1 ... Conductive hollow fiber membrane, 2 ... Ground, 3 ... Treated water inlet, 4 ... Treated water outlet, 5 ... Backwash water inlet, 6 ... Air inlet, 7 ... Backwash water outlet, 8 ... Hollow fiber membrane, 9 ... Captured deposit, 10 ... Peeling deposit, 11 ... Air bubbling, 12
…… Residual deposits, 13 …… Pores, 14 …… Untreated water, 15 ……
Permeate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Otsuka 3-1-1, Saiwaicho, Hitachi City Hitachi Factory, Hitachi Co., Ltd. (72) Inventor Satoshi Kikuchi 3-1-1, Saiwaicho, Hitachi Company Hitachi, Ltd. (56) Reference JP-A-56-134211 (JP, A) JP-A-60-99071 (JP, A) JP-A-53-132479 (JP, A) Special table Sho-61- 500833 (JP, A)

Claims (6)

(57) [Claims] 1. A water filtration device for a nuclear reactor plant, which comprises a hollow fiber membrane made of a hollow porous polymer material and having a specific resistance of 50 kΩcm or less. 2. The water filtration device for a nuclear reactor plant according to claim 1, wherein a conductive substance having a specific resistance of 10 kΩcm or less is attached to the surface of the hollow fiber membrane. 3. The water filtration device for a nuclear reactor plant according to claim 1, wherein a conductive substance having a specific resistance of 10 kΩcm or less is formed on the surface of the hollow fiber membrane. 4. The water filtration device for a nuclear reactor plant according to claim 1, wherein a conductive substance having a specific resistance of 10 kΩcm or less is permeated into the material of the hollow fiber membrane. 5. The water filtration device for a nuclear reactor plant according to any one of claims 1 to 4, wherein the hollow fiber membrane is grounded. 6. A hollow fiber membrane made of a porous polymer material is vapor-deposited with a metal having a specific resistance of 1 Ωcm or less, a metal compound, a substance having an ability to impart an ion exchanger, or a conductive polymer having a specific resistance of 10 kΩcm or less, A method of manufacturing a water filtration device for a nuclear reactor plant, which comprises applying or dipping the solution to cause it to penetrate.