JPS6149638B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for removing trace amounts of metal ions such as cobalt ions, anions such as chloride ions, and fine particulate metal salts such as iron oxide contained in reactor water of a nuclear reactor. It is related to the device.

Corrosion products activated in the reactor core accumulate in the reactor water and must be removed. Conventionally, a reactor water purification system as shown in FIG. 1 has been generally provided.

In the figure, 1 is a nuclear reactor, and the high-temperature, high-pressure steam generated here is sent to the turbine 2 via the main steam pipe 24, and after being liquefied in the condenser 3, the feedwater heater 8
The reactor 1 is then refluxed to the reactor 1. In this condensate flow path, a reactor water system purification system 4 consisting of an over-desalination device 6 and a demineralization device 7 is constructed, and thereby metal ions such as cobalt, iron, and manganese, metal salts such as iron compounds, and chlorine ions It is designed to remove anions such as As a separate system from the reactor water system purification system 4 described above, reactor water in the reactor 1 is sucked and pressure-fed to a recirculation pump 13 via a recirculation pipe 11, and a reheat exchanger 5 and a cooler are installed in the flow path. A reactor water system purification system 25 consisting of a demineralizer 9 and a superdemineralizer 10 is provided.

The above demineralizer 10 is of the same type as the above demineralizer 6, and uses an ion exchange resin. Since this ion exchange resin has a problem in heat resistance, a structure is used in which a cooler 9 is provided upstream of the super-demineralizer 10 to cool the reactor water and then flow it to the super-demineralizer 10. Then, the reactor water that has passed through the furnace over-desalinator 10 passes through the regenerative heat exchanger 5,
The reactor water flowing into the cooler 9 is precooled.

In the conventional reactor water purification system as described above, a large amount of heat loss occurs due to the cooling of the reactor water by the cooler 9, and the reheat exchanger 5 is used to reduce this heat loss.
Furthermore, although this device can remove cations and anions, it does not have a sufficient effect in removing fine particulate metal salts.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a method and an apparatus for purifying reactor water under high temperature and high pressure conditions.

In order to achieve the above object, the reactor water purification method according to the present invention alternately places a porous conductive filler and a porous electrically insulating member between a pair of electrodes with a structure through which liquid can flow. interposed between the pair of electrodes,
By supplying electricity while flowing reactor water in a direction that intersects the pole surface of the electrode, bipolar electrolysis is performed between the electrodes, and metal ions and anions in the reactor water are occluded in the bipolar filler. At the same time, it is characterized by neutralizing the charge on the fine particulate metal salts in the reactor water using a bipolar filler and attaching them to the reactor water.

In the reactor water purification device according to the present invention, a porous conductive filler and a porous conductive member are alternately interposed between a pair of concentric cylindrical electrodes having a liquid-permeable structure. A bipolar electrolyzer is constructed by arranging a plurality of the bipolar electrolytic units, and a means for flowing reactor water across the polar faces of the electrodes is provided, and each The present invention is characterized in that a means for connecting the electrode to the DC electrode is provided.

Next, the outline of the apparatus of the present invention will be explained with reference to FIG. In this figure, members with the same drawing reference numbers as in the conventional device (FIG. 1) are the same constituent members as in the conventional device. Section A is a bipolar electrolysis section according to the present invention, which includes a bipolar electrolytic cell 12, which will be described later with reference to FIGS. 3 and 4, and a purification circulation pump 30 for circulating reactor water to this bipolar electrolytic cell 12. and piping. Section B is a bipolar electrolytic cell cleaning section which will be described later.

A detailed sectional view of the bipolar electrolytic cell 12 described above is shown in FIG.

Since the bipolar electrolyzer 12 passes high-temperature and high-pressure reactor water, a pressure vessel type case 1 that can withstand this is used.
A reactor water inflow pipe 12b and a reactor water outflow pipe 12c are fixedly connected to each other at both ends thereof, and two supports 15a and 15b are fixed inside thereof in the form of partition plates.

A large number of bipolar electrolysis units 14, 14, . . . are interposed between the two supports 15a, 15b.

FIG. 4 is an enlarged sectional view of the bipolar electrolysis unit 14. The bipolar electrolytic unit 14 has an inner cylinder 19 made of porous metal and an outer cylinder 20 having a large number of holes in the tube wall, which are arranged concentrically, and each has an electrically insulating member 22 at one end. , 22', and the bottom plate 18 is attached to the other end via electrically insulating members 22, 22', respectively.

Electrical wiring 16a, so as to conduct the DC external power supply 16 to the inner cylinder 19 and outer cylinder 20, respectively.
Connect 16b. 16c is the electrical wiring 16 mentioned above.
This is a polarity changeover switch provided in the middle of a and 16b. When purifying reactor water, this switch is inserted into the upper part of the figure, with the outer cylinder 20 serving as the anode and the inner cylinder 19 serving as the anode.
are respectively conducted to the cathode.

Water holes 15a-1 and 15b-1 are formed in the supports 15a and 15b, respectively. The flange 17 of the bipolar electrolysis unit 14 is connected to the water passage hole 15b of the support body.
1, and the bottom plate 18 of the bipolar electrolytic unit 14 is fixed to the support body 15b according to the water passage hole 15a of the support body.
1 is fixed to the support body 15a so as not to block it. As a result, the reactor water flows to the outer surface of the outer cylinder 20 as shown by the arrow C, flows through the outer cylinder 20 and the inner cylinder 19 as shown by the arrow E, and flows through the water passage hole 1 of the support body 15b as shown by the arrow D.
Flows through 5b-1.

A filler 21 is provided between the inner cylinder 19 and the outer cylinder 20.
Interpose. This filler is constructed by alternately laminating porous conductive fillers and porous electrically insulating members.

In this example, a nylon net was used as the porous electrically insulating member, and activated carbon fiber was used as the porous conductive filler.

The above-described filler 21 according to the present invention can also be constructed by mixing a granular or fine-grained electrically conductive member and a granular or fine-grained electrically insulating member.

As described above, the device of this embodiment has a porous electrically insulating member between a pair of concentric cylindrical electrodes,
A bipolar electrolytic unit is constructed by alternately interposing porous conductive fillers, a bipolar electrolytic cell is constructed by arranging a plurality of bipolar electrolytic units,
This bipolar electrolytic cell is provided with means for causing reactor water to flow therethrough, and is also provided with means for connecting each electrode constituting the bipolar electrolytic unit to a DC power source.

As mentioned above, since the structure is such that water flows in the direction of arrow E through the wall surface of the outer cylinder 20, the filler 21, and the wall surface of the inner cylinder 19, the inner cylinder 19 is a porous metal tube with water permeability. The water flow path is narrow enough to prevent the fibers and particles constituting the filler 21 from passing through.

Further, as described above, the outer cylinder 20 is made of a material that does not undergo so-called anodic oxidation to form water-soluble compounds, since it is electrically connected to the anode of the DC power supply 16 and acts as an anode for electrolysis.

Next, the bipolar electrolytic cell cleaning section B shown in FIG. 2 will be explained.

This is provided to clean and regenerate impurities removed from reactor water when they accumulate in the bipolar electrolytic cell 12.The ion recovery device 31 is the main component, and the inside of this recovery device 31 is a pump 32, circulation pipes 33, 34, and valves for circulating the cleaning water in the recovery device to the bipolar electrolytic cell 12; 35 and 36. Valves 37 and 38 are provided to isolate the bipolar electrolytic cell 12 from the reactor purification system piping 25 while the cleaning pure water is circulated to the bipolar electrolytic cell 12 using the above configuration.

As the ion recovery device 31, any device having the function of removing metal ions and anions in water can be appropriately selected and used, but it is convenient to use a filter device using activated carbon.
In this example, a super-demineralizer precoated with a mixture of oxine-impregnated activated carbon and an anion exchange resin is used.

In this way, the reactor water purification system piping 2 of this embodiment
Reference numeral 5 is provided with a valve for temporarily shutting off the bipolar electrolytic cell 12 from the reactor water purification system, and the direction in which the purified water for cleaning is circulated to the bipolar electrolytic cell 12 by the pump 32 is as follows. The flow direction of reactor water should be opposite to that during normal operation.

In order to purify reactor water using the reactor water purification system configured as described above, the valve 3 shown in FIG.
7 and 38, close the valves 35 and 36, operate the purification circulation pump 30 to circulate the reactor water through the bipolar electrolyzer 12, and turn the polarity switch 16c shown in FIG. The outer cylinder 20 is connected to the anode and the inner cylinder 19 is connected to the cathode, respectively, and the reactor water flows from the outside of the outer cylinder to the inside of the inner cylinder, as shown by the arrow E.
Distribute it like E′.

This creates a potential difference between the outer cylinder 20, which is the anode, and the inner cylinder 19, which is the cathode, but activated carbon fibers, which are conductive fillers, and nylon nets, which are electrically insulating members, are alternately placed between the two electrodes. Since the activated carbon fibers that are the filler are stacked in layers, the activated carbon fibers as the filler become bipolarized, resulting in a state similar to when N electrolytic cells are provided in series.
However, N is the number of laminated nylon nets. As a result, the effective area of the electrode is increased approximately N times, so that ions in the reactor water can be actively electrolytically removed even in a narrow gap between the electrolytic electrode plates. Since the bipolar electrolytic cell 12 has a plurality of bipolar electrolytic units 14 arranged as described above, it has a large effective electrode plate area.
Even a small bipolar electrolyzer can exhibit large electrolysis capacity.

Metal ions such as cobalt ions and anions such as chlorine ions are thereby occluded by the bipolar filler (activated carbon fiber) and removed from the reactor water.

In addition, fine particles of insoluble salts such as iron oxide are electrically charged in the reactor water, so they electrophores toward an electrode of opposite polarity, touch the opposite electrode, have their charge neutralized, and adhere.

In this embodiment, as described above, the outer cylinder is used as an anode,
Since the inner cylinder is used as a cathode, metal ions, which are cations, and positively charged metal salt fine particles move toward the inner cylinder 19, which is a cathode, in the direction of arrow E, that is, in the same direction as the flow direction of reactor water. electrophoresis due to electric force. Therefore, the aforementioned impurities in the reactor water can be smoothly removed.

As explained above, in the reactor water purification method according to the present invention, a porous conductive filler and a porous electrically insulating member are alternately interposed between a pair of electrodes. By supplying electricity while flowing reactor water, bipolar electrolysis is performed between the electrodes, which causes the metal ions and anions in the reactor water to be occluded in the filler, and at the same time neutralizes the electrical charge of the fine particulate metal salts in the reactor water. It can be applied to the filling material. and,
Since the above-mentioned removal action does not use an ion exchange reaction, it can be carried out under the general conditions of reactor water, for example, at a high temperature and pressure of 285°C and 80ato.

When the impurities in the reactor water are removed as described above, the impurities are accumulated in the bipolar electrolytic cell 12. To clean this, close the valves 37 and 38 shown in FIG.
5 and 36 are opened, and the pump 32 is operated to circulate pure water into the bipolar electrolytic cell 12. Since this flow direction is opposite to the flow direction of reactor water during reactor water purification, accumulated impurities are easily washed away. At this time, when the polarity changeover switch 16c is operated to connect the inner tube 19 to the anode and the outer tube 20 to the cathode, the metal ions and chlorine ions occluded in the filler will be eluted into the pure water that is the cleaning solution. It is encouraged to do so. The washed out metal ions, anions, and metal salts are separately removed by a recovery device 31.

After cleaning the bipolar electrolytic cell 12 as described above, the pump 32 is stopped, the valves 35 and 36 are closed, and the valves 37 and 38 are opened and the purification circulation pump 3
0 and operate the polarity changeover switch 16c to connect the anode of the DC power source to the outer cylinder 20 and the cathode to the inner cylinder 19, respectively, and purification of the reactor water can be resumed.

As in this embodiment, if the flow of reactor water to the bipolar electrolyzer can be temporarily shut off, and if the cleaning water can be made to flow in the opposite direction to the above-mentioned water flow, the bipolar electrolyzer It is economical because the bipolar electrolytic cell can be used repeatedly by cleaning and removing impurities accumulated in the cell.

Next, an experiment conducted to confirm the effect of removing reactor water impurities by bipolar electrolysis applied to the present invention will be described.

FIG. 5 is a sectional view of an experimental bipolar electrolytic cell.

41 is the cathode, 42 is the anode, both 100mm x 100mm.
It is a 5t ferrite board.

The electrolytic cell 43 is constructed so as to house the above-mentioned two electrode plates separated by 35 mm, and is further provided with a stirring section 44 below the electrolytic cell 43 as means (not shown) for stirring the electrolytic solution.

Six nylon nets 45, 4 are placed between the above two electrode plates.
5... and five activated carbon fiber layers 46, 46... are laminated and interposed.

In the experiment, particles with a diameter of 2 to 5 μm were placed in the above bipolar electrolytic cell 43.
A cobalt chloride aqueous solution containing iron oxide of m is introduced and electricity is applied, and the cobalt ion concentration and iron concentration are determined every 10 minutes using an atomic absorption spectrometer, and the chloride ion concentration is determined using the mercuric nitrate method. was quantified.

FIG. 6 is a chart showing changes in the residual cobalt ion concentration and the residual chlorine ion concentration, and is the result of applying current at 0.1 A using 200 ml of 2.2 mg/cobalt chloride solution.

Cobalt ion concentration at the start of energization is 1.0
mg/, and the chloride ion concentration was 1.2 mg/.
As shown in the figure, the concentration decreased significantly, and after 30 minutes, the concentration of cobalt ions was 0.1mg/, and the concentration of chloride ions was 0.3mg/
decreased to

Figure 7 is a chart showing temporal changes in the concentration of iron oxide fine particles. Distilled water in which 1.0 mg of iron oxide fine particles (particle size 2 to 5 μm) are suspended is placed in the bipolar electrolytic cell shown in Figure 5. The results of the experiment are shown below.

The curve marked with a black circle in the same figure shows the case where only stirring is performed without energization, and a slight decrease is observed at first, but the decreasing curve gradually approaches a horizontal line.The curve marked with a white circle in the same figure shows the case when electricity is applied. , a significant decrease was observed. This is thought to be because the charged and floating iron oxide fine particles are attracted by the electric force and migrate, touch the bipolar electrodes, have their charged charges neutralized, and adhere to the activated carbon fibers.

The above experiments show that bipolar electrolytic treatment is extremely effective in removing and cleaning cobalt ions, chloride ions, and iron oxide fine particles in reactor water. Although this experiment was conducted at normal temperature and pressure, similar effects are expected under high temperature and high pressure, which is the general condition of reactor water.

As detailed above, the reactor water purification method according to the present invention uses a porous conductive filler (activated carbon fiber in the above embodiment) between a pair of liquid-permeable electrodes, and a porous conductive filler (activated carbon fiber in the above embodiment). electrically insulating members (nylon mesh in the above example) are alternately interposed between the pair of electrodes, and electricity is supplied between the pair of electrodes while flowing reactor water in the direction intersecting the electrode surface. By performing bipolar electrolysis, it is possible to occlude metal ions and anions in the reactor water in the filler, as well as neutralize the charge on the fine particulate metal salts in the reactor water and make them adhere to the water. It is thermoeconomically advantageous because it can be purified by

Further, the device according to the present invention is a bipolar electrolytic unit in which a porous electrically insulating member and a porous electrically conductive filler are alternately interposed between a pair of concentric cylindrical electrodes having liquid permeability. A bipolar electrolyzer formed by arranging a plurality of the bipolar electrolysis units is provided with means for allowing reactor water to flow across the pole faces of the electrodes, and means for making each electrode conductive to a DC power supply. By providing this, the method of the present invention described above can be easily carried out and its effects can be fully exhibited.

Furthermore, by attaching an appropriate cleaning device to the above-mentioned bipolar electrolytic cell, it is possible to remove it from the reactor water and wash the reactor water impurities accumulated in the bipolar electrolytic cell, thereby regenerating the purification function. Economical.

[Brief explanation of the drawing]

Fig. 1 is a piping diagram of a reactor water purification system commonly used in the past, Figs. 2 to 4 show a purification system according to the present invention, Fig. 2 is a piping diagram, and Fig. 3 is a A cross-sectional diagram of an electrode electrolyzer with electrical wiring added,
FIG. 4 is a sectional view of the bipolar electrolysis unit with electrical wiring added. Figures 5 to 7 show experiments to confirm the effects of the present invention, Figure 5 is a cross-sectional view of an experimental bipolar electrolyzer, Figure 6 is a chart showing the effect of removing cobalt ions and chloride ions, and Figure 7 is a chart showing the effect of removing iron oxide. 12...Bipolar electrolytic cell, 12a...Same case, 1
2b...Reactor water inflow pipe, 12c...Reactor water outflow pipe, 14...Bipolar electrolysis unit, 16...DC power supply, 16a, 16b...Reactor water wiring, 16c...
Same polarity changeover switch, 19...Inner cylinder of concentric cylindrical electrode, 20...Outer cylinder, 22, 22'...Electrical insulating member, 30...Purification circulation pump, 32...Washing water pump, 35, 36, 37, 38... Valve, 41... Cathode of experimental bipolar electrolytic cell, 42...
The same anode, 43...the same container, 44...4 the same stirring part,
45... Nylon net as a porous electrically insulating member, 46... Activated carbon fiber as a porous conductive filler.

Claims (1)

[Scope of Claims] 1 A porous conductive filler and a porous electrically insulating material are optically filled between a pair of electrodes having a structure that allows liquid to flow between the front and back surfaces, By supplying electricity while flowing reactor water in a direction that intersects the pole surface of the electrodes, bipolar electrolysis is performed between the electrodes, and the metal ions and anions in the reactor water are converted into bipolar filling material. A nuclear reactor water purification method characterized by occluding and removing fine particulate metal salts and neutralizing the charge with a bipolarized filler and attaching them. 2 A pair of large-diameter and small-diameter cylindrical electrodes with a structure that allows liquid to flow through the cylindrical wall is arranged concentrically, and a porous conductive filler and a porous electrical conductive material are arranged between the pair of electrodes. A bipolar electrolytic unit is constructed by alternately interposing insulating members, and a bipolar electrolytic cell is formed by arranging a plurality of the bipolar electrolytic units. 1. A nuclear reactor water purification system, characterized in that a main stage is provided to allow reactor water to flow through the reactor water, and means for connecting each electrode to a DC power source is provided. 3 The above-mentioned concentric cylindrical electrode uses the outer cylinder as an anode,
The atom according to claim 2, wherein the inner cylinder is used as a cathode, and the means for flowing the reactor water is configured to flow the reactor water from the outer cylinder side toward the inner cylinder. Reactor water purification system. 4. The means for circulating reactor water shall be capable of temporarily blocking the flow of reactor water, and the bipolar electrolyzer shall be a means for distributing cleaning water in the opposite direction to the direction of flow of reactor water. A nuclear reactor water purification system according to claim 2 or 3, characterized in that it is equipped with: 5. The reactor water purification system according to claim 4, wherein the means for circulating the cleaning water is equipped with an activated carbon-filled electrolytic treatment device for regenerating the cleaning liquid. .