JPS6195295A - Water treatment device for nuclear power plant - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a cooling water and wastewater purification device for a nuclear power plant, and more particularly to a nuclear power plant water treatment device. [Background of the Invention] As an example of using an electrochemical reaction for water treatment in a nuclear power plant, it is known that a bipolar electrolytic cell is used to purify reactor water, as shown in Japanese Patent Application Laid-Open No. 58-24897. ing. This method is effective in removing metal ions and iron oxides from high-temperature, high-pressure water, but since the filler is simply porous insoluble particles, there is a limit to the components that can be removed, and the removal efficiency decreases unless the water is used at a high temperature. There were problems such as what to do.

[Purpose of the invention]

The object of the present invention is to provide a device that removes each impurity with high efficiency in the purification of cooling water and wastewater of a nuclear power plant by energizing a bipolar electrolytic section filled with a mixture of fillers capable of effectively removing each impurity. Our goal is to provide the following. (Summary of the Invention) Water treatment equipment for nuclear power plants has three major problems: limited removal components, severe clogging and short lifespan of each material, and large amount of waste. Extending the service life and reducing the amount of waste by purifying with a bipolar electrolytic section filled with a filler that can be used or incinerated, and using a filler that can effectively remove each impurity depending on the nature of the impurity. This eliminates restrictions on the components to be removed, thereby making it possible to efficiently remove metal ions, iron oxides, and halogen ions with a small amount of waste. An embodiment of the water treatment device will be explained with reference to Fig. 1.The device consists of a bipolar electrolytic cell consisting of an anode 1, a cathode 2, fillers 3, 4, 5, a support for the filler 6, and an external power source 7. The structure of the filler 3 is porous particles impregnated with silver ions, the filler 4 is porous particles, and the filler 5 is metal oxide particles.The treated water has a structure in which gas generated by decomposition of water enters the device. Flow from bottom to top so that it flows quickly without stagnation. Next, we will explain the function of the bipolar electrolyzer.
Each filler 3, 4.5 contains 9 metal ions, iron oxide,
-) 0 gen ions can be efficiently removed. Since the fillers that work effectively on metal ions, iron oxides, and halogen ions are different, the functions of the bipolar electrolytic section will be explained separately for each object to be removed. First, metal ions will be explained. The removal mechanism of metal ions is electrolytic reduction precipitation followed by fine □
This is occlusion into the pore. Therefore, metal ions are fillers 4.
Part of the iron oxide that undergoes electrolytic reduction at the cathode part of 5 is precipitated on the surface of the fillers 4 and 5, and the rest is occluded in the pores of the filler 4. Next, iron oxide will be explained. The removal mechanism of substances is agglomeration due to the application of electricity and electrical adhesion.Of these, the most important is the aggregation due to the application of electricity.-This reaction occurs as a result of the generation of hydrogen gas and the reduction of dissolved oxygen that occurs at the cathode part of the filler. This is caused by ion occlusion of hydroxide ions on the surface of iron oxide. This agglomeration is affected by the material of the filler, and when a metal oxide such as titanium dioxide or ferrite is used as a filler layer, this effect is reduced. Therefore, iron oxide aggregates at the cathode part of the filler 5 and adheres to the filler 3, 4.5.Furthermore, since iron oxide has a positive natural potential (surface potential), some are removed by electrical attachment to the cathode portion of the fillers 3 and 4.5.Finally, we will explain the halogen ions.The removal mechanism of the halogen ions is gasification by electrolytic oxidation, followed by occlusion and halogenation. The halogen ions are electrolytically oxidized at one pole of the fillers 3, 4.5 and become halogen gas, which is occluded in the pores of the fillers 4, 5.However, the halogen gas is absorbed by the water. It is easy to dissolve and return to a single halogen ion, and electrolytic oxidation and occlusion alone are sufficient.Therefore, the remaining halogen ions are fixed as silver halide using a filler 3 and removed. The filler supports 6 were placed so that each filler was separated to facilitate recycling. It is not necessary to install the fillers 3 and 4.5. The arrangement of the fillers 3 and 4.5 does not necessarily have to be as shown, and it is possible to fill them in a warm state, but it is possible to do so depending on the ease of regeneration of each filler and functional layer. □ Porous particles impregnated with silver ions are filled with metal oxide, porous particles, and porous particles impregnated with silver ions in this order from the water inlet. The filling material 3 used does not necessarily need to be energized, and it is also possible to transfer the filling material 3 to another tower and operate the two towers, the packed electrolytic cell and the packed tank, in series. Next, fill material a; 4. This section explains S regeneration and waste treatment. Since the processing method differs depending on each filler, we will explain each filler separately below. First, the filler 3, which is a porous particle impregnated with silver ions, will be explained. Since the filler 3 is non-recyclable, recyclable, and recyclable, if the halogen ion removal performance deteriorates, it is transferred to another tank and reused by impregnating it with silver ions. Next, the filler 4, which is a porous particle, will be explained. The filler 4 can be regenerated with acid. If the metal ion removal performance deteriorates,
The filling material is transferred to another tank and stirred in dilute sulfuric acid to be regenerated and reused. The filling material 5, which is a metal oxide, does not need to be recycled in terms of impurity removal performance, but if radioactive materials accumulate in the filling material 5 and the radiation dose rate of the purification device becomes high, the filling material 5 may have a limited lifespan. Transfer material 5 to another tank and ED
It is regenerated by stirring and heating in an aqueous solution of a complexing agent such as TA. “If the iron oxide removal performance deteriorates, take action by performing air force bubbling and backwashing while each filler is still in the equipment.The wastewater generated from the regeneration of each filler is treated with activated carbon, and the used Activated carbon is incinerated to reduce its volume.
When a carbonaceous material such as activated carbon or activated carbon fiber is used for the porous particles of the fillers 32 and 4, it is also possible to reduce the volume by incinerating the fillers 3 and 4 without regenerating them. Finally, an example of six systems is shown in FIG. 2 to explain the systems in which the above-mentioned accessory equipment for regenerating filler material is installed in the purification apparatus according to the present invention. Purification bag according to the invention! The filler regeneration system No. 8 includes a silver ion re-impregnation tank 9 for filler 3 which is porous particles impregnated with silver ions, a regeneration tank 10 using dilute sulfuric acid for filler 4 which is porous particles, and metal oxide. Regeneration tank 11 using a complexing agent for the filler 5. It consists of a pure water tank 12 for backwashing and an activated carbon packed tower 13 for treating recycled waste liquid. The filler material 3.4 is taken in and taken out from the upper part of the purification apparatus 8, and the filler material 5 is taken out from the lower part of the purification apparatus 8, transferred to each regeneration tank 9, 10.degree. 11, and the purification apparatus 8 is refilled after regeneration. If the amount of iron oxide accumulated in each filler 3, 4.5 increases and the iron oxide removal rate decreases, backwashing is performed while bubbling with pure water in the pure water tank 12 and compressed air. The recycled waste liquid and backwash waste water are treated in an activated carbon packed tower 13. Used activated carbon is also incinerated to reduce its volume. Next, an example of application to an actual machine will be explained. F Nuclear Plant - An example of application to the condensate purification system of the next system is shown in Figure 3, reactor 14. Turbine 15. A purification device 8 according to the present invention is installed in the condensate purification system following the condensate vessel 16, and after removing metal ions, iron oxides, and halogen ions in the condensate, it is preheated and returned to the reactor 14. Purification bag M8 by
Since alkali metal ions and alkaline earth metal ions cannot be removed by
Alternatively, in the event of a seawater leak, the condensate treated with the purification device 8 according to the present invention is desalinated by passing it through the desalination system 17 equipped with a desalination device 1118, and then returned to the reactor 14 using three types of filling materials. It is desirable to determine the filling ratio according to the water quality of condensate in each nuclear power plant.In new nuclear plants, seawater leakage hardly occurs due to the improved material of the condenser 16, so silver ions for removing halogen ions are impregnated. Filler 3 is 5-fL, 4**t! "°"tlkfF)2M(
b3HE”0, ・You only need to fill it.
・Next, FIG. 4 shows an example in which the purification device according to the present invention is applied to purification of nuclear plant equipment drain. The equipment drain stored in the equipment drain tank 19 is sent to the sample tank 20 after removing metal ions, iron oxides, and halogen ions in the purification device 8 according to the present invention, and after checking the water quality, it is sent to the condensate storage tank 21. A desalination system 17 is installed for the same reason as the condensate purification system even in a system where no water is stored. If the quality of the water in the sample tank 20 does not meet the standards, reprocessing is performed in the desalination device 18 of the desalination system 17. Most of the substances currently removed from equipment drains are iron oxides. Therefore, when only iron oxides are to be removed, the purifying device 8 according to the first invention is composed of two types of fillers: filler 4, which is porous particles, and filler 5, which is metal oxide. In addition, when only iron oxides are to be removed, it is not necessary to apply electricity to direct current, and low-frequency alternating current may be used.6Finally, an example in which the purification device according to the present invention is applied to purification of nuclear plant fuel pool water. is shown in Figure 5. The water in the fuel pool 22 is used to store spent fuel, used parts with strong radioactivity, etc. in the fuel pool for a long period of time.
The water in the 0m feed boule 22, which needs to maintain water clarity, remove radioactive substances, and remove corrosive halogen ions, is passed through the skimmer surge tank 23 into the purification bag of the present invention! The purifying device 8 according to the present invention generates active oxygen when removing impurities and has a sterilizing effect, thus maintaining the clarity of the fuel pool and water. can do. In addition, in this case, even if alkali metal ions, especially sodium ions, are present in the water, there is no need to install the desalination system 17 because the half-life of radioactive sodium-24 is short and there is no need to remove them.
Since the purification device according to the present invention has functions such as removing metal ions, removing iron oxides, removing halogen ions, sterilizing, and decomposing organic matter, it can be applied to a wide range of applications such as general industrial wastewater treatment, sewage treatment, etc. It is possible to apply it to the field. An experiment to demonstrate the effects of the present invention will be described. Since it is difficult to completely simulate the cooling water and wastewater of an actual nuclear power plant, pure water is added with cobalt ions as metal ions, iron(III) oxide as iron oxide, and chloride ions as halogen ions. Each function of the purification method according to the present invention will be explained separately. First, the metal ion removal characteristics will be described. Figure 6 shows the filled electrolytic cell used in the experiment. The size of the electrolytic cell is 8
0 x 1100 x 40 with electrolytic section 24. A stirring section 25 is provided at the bottom. The electrolytic section 24 uses ferrite plates (100 x 100 x 5 m+) for both the anode 26 and the cathode 27, between which activated carbon fibers 28 as porous particles and nylon nets 29 as spacers are filled in a total of 5 g* in five layers. The experiment was conducted by placing a cobalt chloride aqueous solution of 2.2/Q in a 200 mQ electrolytic cell and applying a constant DC current of 0.1 A to the electrolyte, and measuring the change in cobalt ion concentration with respect to the current application time. Cobalt ion concentration analysis was performed using atomic absorption spectrometry. The results □ are shown in Figure 7. - The activated carbon fiber 28 becomes bipolar due to direct current, and cobalt ions with a low reduction potential are electrolytically reduced and precipitated at the cathode part, which is thought to be occluded in the pores. The iron oxide removal characteristics will be described. The mechanism for removing iron oxides is aggregation due to energization and electrical adhesion, but first we will discuss aggregation due to energization. Changes in particle size resulting from agglomeration upon application of electricity were measured. Experimental equipment is 100X100
10 as anode and cathode on both sides in a x100Wn electrolytic cell
A ferrite plate of 0x100x5 was installed, 700mQ of iron oxide (m) suspension of 5 / Q was placed, and DC current was applied at 70V for 3 layers.Then, the iron oxide (m) was dried and used as a sample to determine the particle size. A light transmission type particle size distribution analyzer was used to measure the particle size.The results are shown in Figure 8.From the results of a more precise study of the agglomeration effect due to zero current, it was found that iron oxide was present in the cathode section. It is thought that hydroxide ions generated by water decomposition and reduction of dissolved oxygen are adsorbed to the surface and aggregated.Furthermore, the influence of the cathode material on the aggregation of iron oxides due to energization was investigated.The experiment was performed as described above. A 10 g/Ω iron oxide (m) suspension was placed in an electrolytic cell for 700 mQ, and after 30 m1N direct current was applied at 70 V, the suspension was placed in a sedimentation bottle and the degree of sedimentation was observed.Cathode used in the experiment The material was ferrite. There were five types: titanium dioxide, platinum, graphite, and grassy carbon. The results are shown in Figure 9. This shows that iron oxide can be efficiently aggregated by using a metal oxide as the cathode material. First, we will discuss the electrical adhesion of iron oxide to the filler.The experiment was conducted using 200 mg of a 1/a iron oxide (III) suspension.
Place it in the electrolytic bath shown in FIG. The change in iron oxide (In) concentration with respect to the current application time was measured when a constant DC current of IA was applied. Concentration analysis of iron oxide (1) was carried out by dissolving iron oxide (m) in hydrochloric acid and then measuring the iron ion concentration by atomic absorption spectrometry. The results are shown in FIG. 10. Since iron oxide has a positive natural potential (surface potential) in pure water, it is thought that it is electrically attached to the cathode portion of the filler and removed. Regarding iron oxides, in addition to this electrical adhesion, in the purifying apparatus of the present invention, agglomeration occurs due to energization, so it can be expected that both the removal rate and the amount removed will be further improved. Finally, we will discuss the halogen ion removal performance. In the experiment, 2.2 g/'a of cobalt chloride aqueous solution was poured into 200 m
g Place it in the electrolytic bath shown in Fig. 6, and This was done by measuring the change in chloride ion concentration with respect to the current application time when a constant DC current was applied to LA. Chloride ion concentration analysis was performed using the mercuric sulfate method. The results are shown in FIG. It is thought that chloride ions undergo electrolytic oxidation at the anode part of the filler, become chlorine gas, and are occluded within the pores. Regarding halogen ions, in the purification device of the present invention, in addition to occlusion as halogen gas, porous particles to which silver ions are attached fix and remove silver ions as silver halide.
It can be expected that both the removal rate and removal amount will be further improved. [Effects of the Invention] As described above, the present invention provides metal ions, iron oxides,
It has the effect of being able to remove impurities in water, such as halogen ions, with high efficiency.

[Brief explanation of the drawing]

Fig. 1 is a schematic structural diagram of an embodiment of the nuclear power plant water treatment equipment of the present invention, Fig. 2 is a system diagram of the purification equipment including the filling material regeneration system of the equipment of Fig. 1, and Fig. 3 is Figure 1 is a nuclear power plant condensate purification system diagram using the purification equipment, Figure 4 is the
Figure 5 is a nuclear plant equipment drain purification system diagram using the purification device shown in Figure 1. Figure 6 is a diagram of the nuclear plant fuel pool water purification system using the purification equipment shown in Figure 1. The explanatory drawings, FIG. 7, FIG. 8, FIG. 9, and FIG. DESCRIPTION OF SYMBOLS 1... Anode, 2... Cathode, 3... Filler made of porous particles impregnated with silver ions, 4... 1st hole made of porous particles 5. Hard grass 2nd eye $q General Lfr Shun (ni) $IO Metsu Raisaki Town (i)

Claims (1)

[Claims] 1. In bipolar electrolytic purification equipment for cooling water and wastewater in nuclear power plants, metal oxide particles such as titanium dioxide and ferrite, porous particles such as activated carbon, and porous particles impregnated with silver ions are filled singly or in combination. A nuclear power plant water treatment device characterized by being made of wood.