JP2014137249A - Zinc injection method and zinc injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zinc injection method which is capable of further increasing a zinc ion concentration of an aqueous carbonic acid solution including zinc ions, which is to be injected into a nuclear reactor pressure vessel, and is capable of suppressing precipitation of zinc.SOLUTION: A zinc injection device 1 provided with a closed loop including a carbon dioxide gas dissolution tank 2 and a zinc dissolution tank 3 filled with a zinc oxide is used for zinc injection to water supply piping. An aqueous carbonic acid solution generated by release of carbonic acid gas from a carbonic acid gas supply pipe 17 to the carbonic acid gas dissolution tank 2 is supplied to the zinc dissolution tank 3 to dissolve zinc in the zinc oxide in the zinc dissolution tank 3. The aqueous carbonic acid solution containing zinc is circulated in the closed loop to increase the zinc concentration. In an injected liquid tank 39 of a pH controller 14, an aqueous carbonic acid solution is generated by supply of carbonic acid gas from the carbonic acid gas supply pipe 17. The aqueous carbonic acid solution not containing zinc in the injected liquid tank 39 is injected to a zinc injection pipe 28 to which the aqueous carbonic acid solution containing zinc is discharged, so that the zinc concentration of the aqueous carbonic acid solution in the zinc injection pipe 28 is reduced.

Description

  The present invention relates to a zinc injection method and a zinc injection device, and more particularly to a zinc injection method suitable for zinc injection into reactor water in a reactor pressure vessel of a boiling water nuclear power plant (hereinafter abbreviated as BWR plant) and The present invention relates to a zinc injection device.

  For example, a boiling water nuclear power plant (hereinafter abbreviated as a BWR plant) includes a nuclear reactor having a reactor pressure vessel (referred to as RPV) in which a core loaded with a plurality of fuel assemblies is disposed. I have. The reactor water supplied to the core by the recirculation pump (or internal pump) is heated by the heat generated by the fission of nuclear fuel material in the fuel assembly loaded in the core, and a part thereof becomes steam. This steam is led from the RPV to the turbine and rotates the turbine. The steam exhausted from the turbine is condensed in a condenser to become water. This water is supplied to the RPV as feed water. In order to suppress the generation of radioactive corrosion products in the RPV, mainly metal impurities contained in the feed water are removed by a filtration and desalting apparatus provided in the feed water pipe.

  In addition, since the corrosion product that is the source of the radioactive corrosion product is generated from the water contact portion of the BWR plant components such as RPV and recirculation piping, the main components of the BWR plant are corroded. Stainless steel and nickel-based alloys such as nickel base alloys are used. Further, the RPV made of low alloy steel has a built-in stainless steel inner surface to prevent the RPV low alloy steel from coming into direct contact with the reactor water. Reactor water is cooling water present in the RPV. Furthermore, a part of the reactor water is purified by a filtration and desalination apparatus of a reactor purification system connected to the RPV to positively remove metal impurities that are slightly present in the reactor water.

  However, even if the above-mentioned corrosion countermeasures are taken, it is unavoidable that very few metal impurities are contained in the reactor water, so some metal impurities are contained in the fuel assembly as metal oxides. Adhere to the surface of the fuel rod. Impurities (for example, metal elements) adhering to the surface of the fuel rod cause a nuclear reaction by irradiation of neutrons emitted by fission of nuclear fuel material in the fuel rod, and radioactive materials such as cobalt 60, cobalt 58, chromium 51 and manganese 54 are emitted. Become a nuclide.

  These radionuclides remain mostly attached to the fuel rod surface in the form of oxides. However, some radionuclides are eluted as ions in the reactor water depending on the solubility of the incorporated oxide, or re-released into the reactor water as an insoluble solid called a clad. The radioactive material contained in the reactor water is removed by the reactor purification system connected to the RPV. The radioactive material that has not been removed by the reactor purification system is circulated through the recirculation system connected to the RPV together with the reactor water, and on the surface of the BWR plant component (for example, piping) in contact with the reactor water. Accumulated. As a result, the radiation emitted from the surface of the component member causes radiation exposure of workers engaged in the periodic inspection work in the periodic inspection of the BWR plant.

  The exposure dose of the employee is managed so that it does not exceed the prescribed value for each person. In recent years, this specified value has been reduced, and it has become necessary to reduce the exposure dose of each person as much as possible.

  Therefore, various methods for reducing the adhesion of radionuclides to the surface of the piping in contact with the reactor water and methods for reducing the concentration of radionuclides in the reactor water have been studied.

  As one of such methods, a metal oxide such as zinc is allowed to coexist in the reactor water, and a dense oxide film containing zinc is formed on the inner surface of the piping and the surface of the structure in contact with the reactor water. A method for suppressing the incorporation of radionuclides such as cobalt 60 and cobalt 58 into the oxide film is described in JP-A-58-79691.

  Also, in Japanese Patent No. 3344608, zinc oxide powder is supplied into the water in the zinc dissolution tank, and then the pH of the water is adjusted by injecting carbon dioxide gas into the water. It dissolves in water in the dissolution tank to produce water containing zinc ions. Water containing this zinc ion is supplied into the RPV.

  Japanese Unexamined Patent Application Publication No. 2003-28985 also describes a zinc injection system. The zinc injection system has a slurry tank, a dissolution tank and an injection water tank. The zinc slurry generated by adding zinc to pure water (or boric acid aqueous solution) in the slurry tank is transferred to the dissolution tank. High-concentration boric acid water (normal boric acid concentration of 2000 ppm or more) is injected into the dissolution tank, and zinc contained in the zinc slurry is dissolved in the dissolution tank with high-concentration boric acid water. High-concentration boric acid water containing dissolved zinc is introduced into the injection tank, and the zinc concentration is diluted with pure water supplied into the injection tank. The diluted high-concentration boric acid water containing zinc is injected into the loop water of the pressurized water reactor by a makeup water pump.

  Furthermore, Japanese Patent Application Laid-Open No. 2003-28985 describes that the solubility of zinc in an aqueous carbonate solution described in Japanese Patent Application Laid-Open No. 8-86899 (Patent No. 3344608) is low.

JP 58-79196 A Japanese Patent No. 3344608 JP 2003-28985 A

  When preparing zinc ions, there is a method of dissolving a salt of zinc and a zinc compound or zinc metal with an acid and an alkali. In either case, since a counter anion or counter cation having a charge opposite to that of zinc ions is also brought into the reactor water, a chemical form with little influence on the reactor water and components is desired. As one such chemical form, in Japanese Patent No. 3344608, zinc ions are prepared by dissolving a zinc compound (for example, zinc oxide powder) using carbonated water.

  In the zinc injection method described in Japanese Patent No. 3344608, zinc is dissolved in an aqueous solution saturated with carbon dioxide gas generated in a zinc dissolution tank, and an aqueous solution containing zinc ions is generated. Furthermore, the concentration of zinc in the aqueous solution is lowered. When an aqueous solution having a low zinc concentration is injected into RPV reactor water, for example, the effect of suppressing the attachment of radionuclides to the surface of the reactor internal structure and the pipe inner surface connected to the RPV is reduced.

  When high concentration boric acid water is used as described in JP-A-2003-28985, zinc is easily dissolved, and the zinc concentration of high concentration boric acid water can be increased. Even if pure water is injected into the high-concentration boric acid water to dilute the zinc concentration of the high-concentration boric acid water, boron is injected into the reactor vessel and the reactor power changes. In particular, in a boiling water reactor in which the reactor power is controlled by control rod operation and core flow rate control, injecting high-concentration boric acid water containing zinc into the reactor pressure vessel It is necessary to perform control rod operation or core flow rate control in consideration of the concentration of boron contained in the acid water, and the control of the reactor power becomes complicated.

  In addition, when water is used to dilute the zinc concentration, the saturated solubility of zinc in high-concentration boric acid water decreases. For this reason, depending on the zinc concentration of the high-concentration borate water, zinc contained in the high-concentration borate water is deposited on the inner surface of the injection pipe of the high-concentration borate water. Depending on the zinc concentration of the high-concentration boric acid and the degree of decrease in the zinc saturation solubility, there is a risk that the injection pipe of the high-concentration boric acid will be clogged with the deposited zinc.

  An object of the present invention is to provide a zinc injection method and a zinc injection device capable of further increasing the zinc ion concentration of a carbonated aqueous solution containing zinc ions injected into a reactor pressure vessel and suppressing the precipitation of zinc. It is in.

A feature of the present invention that achieves the above-described object is that carbon dioxide gas is injected into a carbonic acid aqueous solution present in the first dissolution tank to dissolve the carbon dioxide gas in the carbonic acid aqueous solution.
Circulating the aqueous carbonate solution in the first dissolution tank in a closed loop including the first dissolution tank and the second dissolution tank in which a solid substance containing zinc exists.
Zinc contained in the solid substance is dissolved in an aqueous carbonate solution supplied from the first dissolution tank to the second dissolution tank by circulation in the second dissolution tank,
Supplying an aqueous carbonate solution containing dissolved zinc to the first dissolution tank by the circulation,
Supplying an aqueous carbonate solution containing zinc in the first dissolution tank to a pipe connected to the reactor pressure vessel through a zinc injection pipe connected to the first dissolution tank;
The purpose is to inject a carbonic acid aqueous solution not containing zinc into a carbonic acid aqueous solution containing zinc flowing in the zinc injection pipe.

  In order to circulate the aqueous carbonate solution containing zinc in the closed loop including the first dissolution tank and the second dissolution tank, every time the second dissolution tank is passed, the zinc contained in the solid substance is dissolved in the aqueous carbonate solution. The zinc ion concentration of can be further increased. For this reason, the zinc ion concentration of the reactor water in the reactor pressure vessel can also be increased in a shorter time.

  In addition, since the aqueous carbonate solution containing no zinc is injected into the aqueous carbonate solution flowing in the zinc injection pipe, the zinc concentration of the aqueous carbonate solution flowing in the zinc injection pipe can be reduced. Precipitation on the inner surface can be suppressed.

Injecting carbon dioxide into the aqueous carbonate solution in the first dissolution tank to dissolve the carbon dioxide in the aqueous carbonate solution,
Circulating the aqueous carbonate solution in the first dissolution tank in a closed loop including the first dissolution tank and the second dissolution tank in which a solid substance containing zinc exists.
Zinc contained in the solid substance is dissolved in an aqueous carbonate solution supplied from the first dissolution tank to the second dissolution tank by circulation in the second dissolution tank,
Supplying an aqueous carbonate solution containing dissolved zinc to the first dissolution tank by the circulation,
Supplying an aqueous carbonate solution containing zinc in the first dissolution tank to a pipe connected to the reactor pressure vessel through a zinc injection pipe connected to the first dissolution tank;
Zinc injection by injecting either carbon dioxide or a carbonic acid aqueous solution having a carbonic acid concentration higher than that of the aqueous carbonic acid solution in the first dissolution tank and not containing zinc into a carbonic acid aqueous solution containing zinc flowing in the zinc injection pipe The object of the present invention described above can also be achieved by lowering the pH of the aqueous carbonate solution containing zinc in the pipe.

  Since the carbonic acid aqueous solution containing zinc is circulated in the closed loop including the first dissolution tank and the second dissolution tank, the zinc ion concentration of the carbonic acid aqueous solution can be further increased as described above. Further, either carbon dioxide or a carbonic acid aqueous solution having a carbonic acid concentration higher than the carbonic acid concentration of the aqueous carbonic acid solution in the first dissolution tank and not containing zinc is injected into the carbonic acid aqueous solution containing zinc flowing in the zinc injection pipe. Since the pH of the aqueous carbonate solution containing zinc in the zinc injection pipe is lowered, dissolution of zinc in the aqueous carbonate solution containing zinc flowing in the zinc injection pipe can be promoted. For this reason, it can suppress that the zinc contained in carbonic acid aqueous solution precipitates on the inner surface of zinc injection piping.

  ADVANTAGE OF THE INVENTION According to this invention, the zinc ion density | concentration of the carbonic acid aqueous solution containing zinc ion inject | poured in a reactor pressure vessel can further be increased, and precipitation of zinc to the inner surface of zinc injection piping can be suppressed.

It is a block diagram of the zinc injection | pouring apparatus used for the zinc injection | pouring method of Example 1 which is one preferable Example of this invention. It is explanatory drawing of the zinc ion implantation method into the reactor pressure vessel in a boiling water nuclear power plant using the zinc injection apparatus shown in FIG. It is explanatory drawing which shows the temperature dependence of the solubility of zinc oxide. It is a block diagram of the zinc injection | pouring apparatus used for the zinc injection | pouring method of Example 3 which is another suitable Example of this invention.

  In Japanese Patent No. 3344608, carbonic acid gas is bubbled into the water in the dissolution tank from the bottom of the dissolution tank to generate carbonated water, and the zinc compound is added to the carbonated water in the dissolution tank and stirred to obtain the zinc compound. Dissolves and produces zinc ions. However, in this method, in order to perform continuous injection, it is necessary to regularly supply an appropriate amount of zinc into the dissolution tank according to the amount of water in the dissolution tank to control the zinc concentration. For this reason, maintenance such as regular management and adjustment during operation is required.

  The inventors have disclosed in Japanese Patent Application No. 2012-258400 “Zinc Injecting Method and Zinc Injecting Device” a first dissolving tank in which a carbon dioxide-dissolving region in which an aqueous carbonic acid solution exists is formed, and a solid substance containing zinc. A closed loop including a second dissolution tank in which a zinc dissolution region is formed is formed, and a carbonate aqueous solution containing zinc ions is circulated in the closed loop to increase the zinc concentration of the carbonate aqueous solution, thereby increasing the zinc concentration. Has been proposed to be injected into the reactor water in the reactor pressure vessel. The zinc concentration of the aqueous carbonate solution is controlled to a predetermined concentration by adjusting the flow rate of the aqueous carbonate solution (flow rate of the aqueous carbonate solution) flowing in the second dissolution tank.

  The temperature in the building in which the first dissolution tank and the second dissolution tank are installed is higher in summer and lower in winter. It was investigated how the saturation solubility of zinc in aqueous carbonate solution changes under the influence of such temperature change. As shown in FIG. 3, the saturated solubility of zinc in the aqueous carbonate solution decreases as the temperature of the aqueous carbonate solution increases. For this reason, the zinc which melt | dissolves in carbonic acid aqueous solution becomes easy to precipitate on the inner surface of zinc injection piping with a temperature rise. For example, when a 20 ° C. aqueous carbonate solution with a saturated zinc concentration rises to 30 ° C., the zinc dissolved in the aqueous carbonate solution precipitates on the inner surface of the zinc injection pipe until the saturated solubility of the carbon dioxide drops to 30 ° C. To do. In addition, when the temperature of water flowing through the pipe connected to the reactor pressure vessel, to which the zinc injection pipe is connected, is higher than that of the carbonated aqueous solution containing zinc injected from the zinc injection pipe, Since the temperature of the water becomes high, zinc dissolved in the aqueous carbonate solution is likely to precipitate. In addition, in the unlikely event that carbon dioxide gas supplied into the first dissolution tank leaks from the carbon dioxide supply pipe, the pH of the aqueous carbonic acid solution rises, and dissolved zinc tends to precipitate in the pipe as a compound. .

  In order to prevent such a problem, that is, precipitation of zinc on the inner surface of the zinc injection pipe, the inventors injected water into an aqueous carbonate solution containing zinc ions in order to reduce the zinc concentration of the aqueous carbonate solution. In this case, as described above, the saturation solubility of zinc in the aqueous carbonate solution decreases, and zinc dissolved in the aqueous carbonate solution may be deposited on the inner surface of the zinc injection pipe. The inventors do not inject water into the carbonic acid aqueous solution to reduce the zinc concentration of the carbonic acid aqueous solution, but inject the carbonic acid aqueous solution or carbonic acid gas into the carbonic acid aqueous solution flowing in the zinc injection pipe to It was decided to reduce the pH of the aqueous carbonate solution while maintaining the saturated dissolution of zinc in the aqueous carbonate solution. When the pH of the carbonic acid aqueous solution is decreased, zinc is easily dissolved in the carbonic acid aqueous solution, and precipitation of zinc can be prevented.

  The inventors have created the present invention based on such examination results.

  Examples of the present invention reflecting the above examination results will be described below.

  A zinc injection method according to embodiment 1, which is a preferred embodiment of the present invention, will be described with reference to FIGS. The zinc injection method of the present embodiment is applied to a boiling water nuclear plant (hereinafter referred to as a BWR plant).

  First, a schematic configuration of this BWR plant to which the zinc injection method of the present embodiment is applied will be described with reference to FIG. The BWR plant includes a nuclear reactor 40, a turbine 48, a condenser 49, a recirculation system, a water supply system, and the like. The reactor 40 installed in the reactor containment vessel 46 has a reactor pressure vessel (hereinafter referred to as RPV) 41 containing a core 42, and a jet pump 43 is installed in the RPV 41. The core 42 is loaded with a plurality of fuel assemblies (not shown). Each fuel assembly includes a plurality of fuel rods filled with a plurality of fuel pellets made of nuclear fuel material. The recirculation system has a recirculation pump 44 and a stainless steel recirculation system pipe 45, and the recirculation pump 44 is installed in the recirculation system pipe 45. The water supply system includes a condensate pump 51, a condensate purification device 52, a low pressure feed water heater 54, a feed water pump 53, and a high pressure from a condenser 49 to an RPV 417 through a feed water pipe 50 connecting the condenser 49 and the RPV 41. The feed water heater 55 is installed in this order.

  Cooling water (hereinafter referred to as “reactor water”) in the RPV 41 is pressurized by a recirculation pump 44, passes through a recirculation system pipe 45, and from a nozzle (not shown) of the jet pump 43 to a bell mouth (not shown) of the jet pump 43. ) The reactor water present around the nozzle is also sucked into the bell mouth by the action of the jet flow jetted from the nozzle. Reactor water discharged from the jet pump 43 is supplied to the core 42 and heated by heat generated by fission of nuclear fuel material in the fuel rods. Part of the heated reactor water becomes steam. This steam is guided from the RPV 41 through the main steam pipe 47 to the turbine 48 to rotate the turbine 48. A generator (not shown) connected to the turbine 48 is rotated to generate electric power. The steam discharged from the turbine 48 is condensed by the condenser 49 to become water.

  This water is supplied into the RPV 41 through the water supply pipe 50 as water supply. The feed water flowing in the feed water pipe 50 is boosted by the condensate pump 57, impurities are removed by the condensate purification device 52, further boosted by the feed water pump 53, and heated by the low pressure feed water heater 54 and the high pressure feed water heater 55. The The extracted steam extracted from the main steam pipe 47 and the turbine 48 by the extraction pipe 56 is supplied to the low-pressure feed water heater 54 and the high-pressure feed water heater 55, respectively, and serves as a heating source for the feed water.

  The zinc injection device 1 used in the zinc injection method of the present embodiment is connected to the feed water pipe 50 between the condensate purification device 52 and the low-pressure feed water heater 54 via the zinc injection pipe 28. Details of the zinc injection device 1 will be described with reference to FIG. A zinc injection apparatus 1 includes a carbon dioxide gas dissolution tank (first dissolution tank) 2 that forms a carbon dioxide dissolution area therein, a zinc dissolution tank (second dissolution tank) 3 that forms a zinc dissolution area therein, and a diluent injection apparatus. 14 and a carbon dioxide supply device 16. The other end of the pipe 4 whose one end is connected to the bottom of the carbon dioxide dissolution tank 2 is connected to the bottom of the zinc dissolution tank 3. One end of the pipe 5 is connected to the top of the zinc dissolution tank 3, and the other end of the pipe 5 is connected to the top of the carbon dioxide dissolution tank 2. A closed loop is formed by the carbon dioxide gas dissolution tank 2, the pipe 4, the zinc dissolution tank 3 and the pipe 5. A circulation pump 6, an on-off valve 7, a thermometer 8 and a flow meter 9 are provided in the pipe 4. A conductivity meter (or pH meter) 10 is provided in the pipe 5. A liquid level meter 13 is provided in the carbon dioxide dissolution tank 2.

  More than the amount consumed in one operation cycle of the BWR plant, for example, 30 kg or more of zinc oxide pellets (solid substance containing zinc) is filled in the zinc dissolution tank 3 in advance. Zinc oxide pellets are charged into the zinc dissolution tank 3 during a fuel change period after the operation of the BWR plant in a certain operation cycle is stopped. Instead of zinc oxide, any of zinc carbonate, basic zinc carbonate, and metallic zinc can be used. The zinc oxide pellets have a size that does not float at the flow rate of the aqueous carbonic acid solution rising in the zinc dissolution tank 3, for example, a particle size of 5 mm or more.

  The carbon dioxide supply device 16 includes a carbon dioxide supply pipe 17, a flow rate adjustment valve 18, and a flow meter 19. The carbon dioxide supply pipe 17 connects a carbon dioxide supply source (for example, a carbon dioxide cylinder) (not shown) and the bottom of the carbon dioxide dissolution tank 2. The makeup water supply device 23 has a makeup water supply pipe 24 provided with an opening / closing valve 25. The makeup water supply pipe 24 connected to the top of the carbon dioxide gas dissolution tank 4 is connected to a water source (not shown).

  The zinc injection pipe 28 is connected to the bottom of the carbon dioxide gas dissolution tank 4 and is connected to the water supply pipe 50 as described above. An injection pump 29, an on-off valve 30 and a pressure gauge 31 are provided in the zinc injection pipe 28.

  The diluent injection device 14 includes an injection liquid tank 39, a carbon dioxide injection pipe 20 provided with a flow rate control valve 21, a water injection pipe 26 provided with an on-off valve 27, and a carbonated water injection pipe 32. A liquid level meter 15 is provided in the injection liquid tank 39. The carbon dioxide injection pipe 20 connects the carbon dioxide supply pipe 17 and the bottom of the injection liquid tank 39. A flow meter 22 is provided in the carbon dioxide gas injection pipe 20. A water injection pipe 26 connected to the top of the injection liquid tank 39 is connected to the makeup water supply pipe 24. A carbonated water injection pipe 32 connected to the bottom of the injection liquid tank 39 is connected to the zinc injection pipe 28. A pump 33, an on-off valve 34 and a flow meter 35 are provided in the carbonated water injection pipe 32.

  A control device (not shown) is connected to the on-off valves 7, 30, 34, the thermometer 8, the flow rate control valves 18, 21, and the flow meters 9, 19, 22, 25, 27, 35 by a signal line (not shown). The conductivity meter 10, the liquid level meters 13, 15 and the pressure gauge 31 are connected.

  The zinc injection method of the present embodiment using the zinc injection device 1 will be specifically described below.

  Based on a control command output from the control device, the on-off valves 25 and 26 are opened, a pump (not shown) provided in the makeup water supply pipe 24 is driven, and makeup water is supplied from a makeup water source (not shown). The carbon dioxide gas dissolution tank 2 is supplied through the makeup water pipe 24. This makeup water is supplied to the injection liquid tank 39 through the water injection pipe 26. The liquid level signal measured by the liquid level meter 13 and the liquid level signal measured by the liquid level meter 15 are input to the control device. When the control device determines that the carbon dioxide gas dissolution tank 2 is full based on the liquid level signal from the liquid level meter 13, the control valve 25 is closed. Thereby, the supply of the makeup water to the carbon dioxide dissolution tank 2 is stopped. When it is determined that the injection liquid tank 39 is full based on the liquid level signal from the liquid level meter 15, the control device stops driving the pump and closes the on-off valve 27. Thereby, the supply of the makeup water to the injection liquid tank 39 is stopped.

  After the carbon dioxide gas dissolution tank 2 is full, the control device opens the flow control valve 18 so that the pH of the carbonic acid aqueous solution in the carbon dioxide gas dissolution tank 2 becomes a set pH (pH is, for example, 3.91). The opening degree of the flow control valve 18 is adjusted to a predetermined opening degree. Carbon dioxide from the carbon dioxide supply source is discharged into the water in the carbon dioxide dissolution tank 2 through the carbon dioxide supply pipe 17. The released carbon dioxide is dissolved in the water in the carbon dioxide dissolution tank 2. The carbon dioxide gas not dissolved in the water rises in the carbon dioxide gas dissolution tank 2 and is discharged to the vent pipe 57 connected to the carbon dioxide gas dissolution tank 2. After the infusate tank 39 is full, the control device opens the flow rate control valve 21 and adjusts the flow rate so that the pH of the aqueous carbonate solution in the infusate tank 39 becomes a set pH (pH is 3.91, for example). The opening degree of the valve 21 is adjusted to the predetermined opening degree. The opening degree of the flow control valve 21 is maintained at the predetermined opening degree while carbonated water containing zinc ions is injected into the water supply pipe 50. A part of the carbon dioxide flowing in the carbon dioxide supply pipe 17 is discharged through the carbon dioxide injection pipe 20 into the water of the injection liquid tank 39. The released carbon dioxide gas is dissolved in the water in the injection liquid tank 39. The carbon dioxide gas not dissolved in the water rises in the injection liquid tank 39 and is discharged to the vent pipe 58 connected to the injection liquid tank 39.

  In the carbon dioxide dissolution tank 2 and the injection liquid tank 39 into which the carbon dioxide gas has been injected, a carbonic acid aqueous solution is generated inside. When the dissolution of carbon dioxide in water reaches equilibrium, the pH of the aqueous carbonate solution is about 4, which is the pH of the saturated aqueous carbonate solution. The supply of carbon dioxide to the carbon dioxide dissolution tank 2 and the injection liquid tank 39 is continuously performed while carbonated water containing zinc ions is being injected into the water supply pipe 50.

  Based on the measured value of a conductivity meter (not shown) provided in the carbon dioxide gas dissolution tank 2, the control device sets the pH of the carbonic acid aqueous solution in the carbon dioxide gas dissolution tank 2 to the set pH (eg, 3.91). When it is determined that it has become, a drive start signal is output to the circulation pump 6. In other words, the carbonic acid concentration of the carbonic acid aqueous solution in the carbon dioxide gas dissolution tank 2 is the same as the carbonic acid concentration of the carbonic acid aqueous solution in the injection liquid tank 39. The circulation pump 6 is driven, and the aqueous carbonate solution in the carbon dioxide dissolution tank 2 is supplied to the zinc dissolution tank 3 through the pipe 4.

  The aqueous carbonate solution supplied to the zinc dissolution tank 3 rises in the zinc dissolution tank 3 while being in contact with the zinc oxide pellets among a large number of filled zinc oxide pellets. The rising low pH carbonic acid aqueous solution dissolves the zinc oxide pellets, and zinc contained in the zinc oxide pellets is ionized and eluted into the carbonic acid aqueous solution. As a result, an aqueous carbonate solution containing zinc ions (injected water containing zinc ions) is generated in the zinc dissolution tank 3.

  The elution of zinc in the zinc dissolution tank 3 changes the pH of the aqueous carbonate solution in the zinc dissolution tank 3 to the neutral side, and the elution degree of zinc into the aqueous carbonate solution is suppressed. The aqueous carbonate solution containing zinc ions is discharged from the top of the zinc dissolution tank to the pipe 5 and supplied to the carbon dioxide dissolution tank 2 through the pipe 5. The aqueous carbonate solution containing zinc ions supplied to the carbon dioxide gas dissolution tank 2 is mixed with the aqueous carbonate solution in the carbon dioxide gas dissolution tank 2, pressurized by the circulation pump 6, and introduced into the zinc dissolution tank 3 through the pipe 4. The aqueous carbonate solution containing zinc ions comes into contact with the zinc oxide pellets in the zinc dissolution tank 3, and as described above, the zinc contained in the zinc oxide pellets is ionized and eluted into the aqueous carbonate solution. For this reason, the density | concentration of the zinc ion of the carbonic acid aqueous solution containing zinc ion increases.

  The aqueous carbonate solution containing zinc ions in the zinc dissolution tank 3 circulates in a closed loop formed by the carbon dioxide dissolution tank 2, the pipe 4, the zinc dissolution tank 3 and the pipe 5. Due to the circulation of the aqueous carbonate solution containing zinc ions, the zinc ion concentration of the aqueous carbonate solution increases every time the aqueous carbonate solution passes through the zinc dissolution tank 3 filled with zinc oxide pellets. The zinc ion concentration of the aqueous carbonate solution circulating in the closed loop will eventually reach a saturation concentration. By circulating the aqueous carbonate solution in the closed loop including the zinc dissolution tank 3 filled with zinc oxide pellets, an aqueous carbonate solution in which the concentration of zinc ions has increased to near the saturation concentration can be easily obtained.

  The control device obtains the zinc ion concentration of the aqueous carbonate solution using the electrical conductivity of the aqueous carbonate solution measured by the conductivity meter 10, and until the zinc ion concentration reaches, for example, 350 ppm (set zinc concentration), The rotational speed is increased to increase the flow rate of the aqueous carbonate solution 24 flowing through the zinc dissolution tank 3. When the zinc ion concentration reaches 350 ppm, the rotational speed of the circulation pump 6 is decreased to decrease the flow rate of the aqueous carbonate solution flowing through the zinc dissolution tank 3. In the initial stage of zinc dissolution in the zinc dissolution tank 3, it is preferable to dissolve zinc in the aqueous carbonate solution earlier because zinc can be injected into the RPV 41 earlier. However, once the zinc ion concentration of the aqueous carbonate solution reaches saturation solubility, it is desirable to reduce the linear flow rate to lower the zinc dissolution rate and save the driving power of the circulation pump 6.

  When it is determined that the zinc ion concentration of the aqueous carbonate solution has reached 350 ppm based on the measured value of the conductivity meter 10, the control device outputs an activation signal for the injection pump 29. The infusion pump 29 is activated by this activation signal. When the injection pump 29 is activated, an aqueous carbonate solution having a zinc ion concentration of 350 ppm discharged from the carbon dioxide dissolution tank 2 is injected into the water supply pipe 50 through the zinc injection pipe 28. Carbonic acid aqueous solution having a zinc ion concentration of 350 ppm is mixed in the feed water flowing in the feed water pipe 50. The control device inputs the measurement value of the pressure gauge 31 to control the opening degree of the on-off valve 30 and adjusts the pressure of the aqueous carbonate solution containing zinc ions injected into the water supply pipe 50. Further, the control device adjusts the rotation speed of the injection pump 29, and the zinc ions of the feed water supplied to the RPV 41 based on the zinc ion concentration of the carbonated aqueous solution to be injected and the flow rate of the feed water flowing in the feed water pipe 50 (feed water flow rate). The injection amount of the aqueous carbonate solution into the water supply pipe 50 is controlled so that the concentration becomes a predetermined value, for example, 0.2 ppb (set zinc concentration).

  During the period from winter to summer, the temperature in the building where the carbon dioxide dissolution tank 2 and the zinc dissolution tank 3 are installed and the temperature of the water supply near the connection point of the water supply pipe 50 to the zinc injection pipe 28 are gradually increased. To rise. As the temperature rises, the temperature of the aqueous carbonate solution injected into the water supply pipe 50 also rises, and the zinc contained in the aqueous carbonate solution injected into the water supply pipe 50 interacts with the inner surface of the zinc injection pipe 28 and the zinc injection pipe 28. There is a risk of depositing on the inner surface of the water supply pipe 50 near the connection location.

  The temperature of the carbonic acid aqueous solution flowing in the pipe 4 measured by the thermometer 8 is input to the control device. When the temperature measured by the thermometer 8 rises above the set temperature due to the influence of the water level temperature of the carbon dioxide dissolution tank 2 and the zinc dissolution tank 3 as described above, the control device opens the on-off valve 34. The rotational speed of the pump 33 is adjusted, and the flow rate of the aqueous carbonate solution (the aqueous carbonate solution not containing zinc) injected from the injection solution tank 39 into the zinc injection pipe 28 is adjusted. The carbonic acid in the injection liquid tank 39 having the same carbonic acid concentration as the carbonic acid concentration in the carbon dioxide dissolving tank 2 is compensated for so as to compensate for the decrease in the saturated solubility of zinc in the carbonic acid aqueous solution due to the temperature rise of the carbonic acid aqueous solution flowing in the pipe 4 The flow rate of the aqueous solution injected into the zinc injection pipe 28 by the carbonated water injection pipe 32 is adjusted. By injecting the carbonic acid aqueous solution from the injection liquid tank 39 into the zinc injection pipe 28, the zinc ion concentration of the carbonic acid aqueous solution containing zinc ions flowing in the zinc injection pipe 28 is diluted to 200 ppm. For this reason, precipitation of zinc on the inner surface of the zinc injection pipe 28 is prevented. The control device inputs the measurement value of the flow meter 35 and monitors whether the injection amount of the carbonic acid aqueous solution injected from the injection liquid tank 39 into the zinc injection pipe 28 has become a necessary amount.

  Even when the temperature of the aqueous carbonate solution in the closed loop decreases, such as when going from summer to winter, the temperature of the aqueous carbonate solution measured by the thermometer 8 is input to the control device. When the detected temperature is lower than the set temperature, the control device does not open the on-off valve 34 and does not drive the pump 33. For this reason, the injection of the carbonic acid aqueous solution from the injection liquid tank 39 to the zinc injection pipe 28 is basically not performed. However, in the unlikely event that the carbon dioxide gas supplied to the carbon dioxide gas dissolution tank 2 leaks from the carbon dioxide gas supply pipe 17, the pH of the aqueous carbonic acid solution in the carbon dioxide gas dissolution tank 2 rises, and the dissolved zinc is a compound. To the inner surface of the zinc injection pipe 28. For this reason, it is desirable to always inject the aqueous carbonate solution from the injection solution tank 39 to the zinc injection pipe 28 for the sake of completeness.

  By injecting the aqueous carbonate solution containing zinc ions from the carbon dioxide dissolution tank 2 into the water supply pipe 50, the liquid level of the aqueous carbonate solution in the carbon dioxide dissolution tank 2 is lowered. For this reason, water is replenished into the carbon dioxide gas dissolution tank 2 from the makeup water source. For example, the control device that has input the liquid level of the carbon dioxide gas dissolution tank 2 measured by the liquid level gauge 13 determines that the liquid level of the carbon dioxide gas dissolution tank 2 is based on this water level. For example, when it is determined that 10% of the 200 kg) has dropped to the first lower limit set liquid level of the carbon dioxide gas dissolution tank 2 in a state where it is injected into the water supply pipe 50 through the zinc injection pipe 28, the on-off valve 25 is opened to replenish. The pump provided in the water supply pipe 24 is driven. The water of the make-up water source is supplied to the carbon dioxide gas dissolution tank 2 through the make-up water supply pipe 24. When it is determined that the liquid level measured by the liquid level gauge 13 has reached the first upper limit set liquid level indicating a full water state by supplying makeup water, the control device stops driving the pump.

  By supplying makeup water to the carbon dioxide gas dissolution tank 2, the carbonic acid concentration of the carbonic acid aqueous solution in the carbon dioxide gas dissolution tank 2 is lowered and the conductivity of the carbonic acid aqueous solution is also lowered. Since the supply of carbon dioxide gas from 17 to the carbon dioxide dissolution tank 2 is continuously performed, the decrease in the carbonic acid concentration is suppressed, and the decrease in the dissolution rate of zinc in the zinc dissolution tank 3 is also suppressed. If the zinc ion concentration of the aqueous carbonate solution circulated due to the supply of makeup water to the carbon dioxide gas dissolution tank 2, the rotational speed of the circulation pump 6 is increased. That is, the control device calculates the zinc ion concentration of the carbonic acid aqueous solution in the carbon dioxide dissolution tank 2 obtained based on the conductivity measured by the conductivity meter 10 to 280 ppm, for example, a 20% decrease in the zinc saturation concentration. When it is determined that the rotational speed is lower, the rotational speed of the circulation pump 6 is increased. The linear flow rate of the aqueous carbonate solution rising in the zinc dissolution tank 3 is increased, and the time required for the zinc ion concentration of the aqueous carbonate solution to reach the saturated zinc concentration is shortened. Thus, even when makeup water is supplied to the carbon dioxide dissolution tank 2 and the zinc ion concentration is lowered, the zinc ion concentration of the aqueous carbonate solution in the carbon dioxide dissolution tank 2 can be increased.

  In addition, the decrease in the zinc ion concentration of the aqueous carbonate solution due to the supply of makeup water to the carbonate gas dissolution tank 2 is reduced by narrowing the interval between the start and stop of supply of makeup water to the carbonate gas dissolution tank 2. It can suppress by making the fluctuation | variation of the water level in 2 small. Supply and stop of makeup water to the carbon dioxide gas dissolution tank 2 can be controlled by opening and closing the on-off valve 25 or starting and stopping of a pump provided in the makeup water supply pipe 24. Practically, it is desirable to open and close the on-off valve 25 with less burden on starting and stopping the pump. The decrease in the carbonic acid concentration of the aqueous carbonate solution due to the supply of makeup water to the injection liquid tank 39 is achieved by reducing the level of the water level in the injection liquid tank 39 by narrowing the interval between the start and stop of supply of makeup water to the injection liquid tank 39. It can suppress by making a fluctuation | variation small. The supply and stop of the makeup water to the injection liquid tank 39 can be controlled by opening and closing the on-off valve 27 or starting and stopping of a pump provided in the makeup water supply pipe 24.

  In addition, the flow volume of the carbonic acid aqueous solution supplied to the zinc dissolution tank 3 measured with the flowmeter 9 is input into a control apparatus. The control device stores the flow rate (set flow rate) of the aqueous carbonate solution supplied to the zinc dissolution vessel 3 corresponding to the saturated concentration of zinc in the aqueous carbonate solution, and is based on the flow rate input from the flow meter 9. 3 confirms whether the flow rate of the aqueous carbonate solution supplied to 3 has reached the set flow rate.

  Further, the injection of the aqueous carbonate solution from the injection liquid tank 39 to the zinc injection pipe 28 lowers the liquid level of the aqueous carbonate solution in the injection liquid tank 39. When the control device determines that the liquid level in the infusate tank 39 measured by the liquid level meter 15 has dropped to the second lower limit set liquid level in the infusate tank 39, the control device opens the open / close valve 27 and supplies the makeup water supply pipe. By the driving of the pump provided at 24, makeup water is supplied to the injection liquid tank 39 through the makeup water supply pipe 24. When it is determined that the liquid level measured by the liquid level meter 15 has reached the second upper limit set liquid level indicating a full water state due to the supply of makeup water, the control device stops driving the pump. The pH of the carbonated aqueous solution in the injection liquid tank 39 is increased by supplying makeup water in the injection liquid tank 39. The control device adjusts the opening degree of the flow rate control valve 21 based on the measured value of the conductivity meter provided in the injection liquid tank 39, and carbonates the carbon dioxide into the injection liquid tank 39 from the carbon dioxide supply pipe 17 through the carbon dioxide injection pipe 20. Inject gas. Thereby, pH of the carbonic acid aqueous solution of the injection liquid tank 39 falls to 3.91, for example.

  According to the present embodiment, the carbonic acid aqueous solution in the carbon dioxide dissolution tank 2 is circulated in a closed loop including the zinc dissolution tank 3 filled with zinc oxide pellets and the carbon dioxide dissolution tank 2, so that zinc ions are injected into the RPV 41. The zinc ion concentration of the carbonated aqueous solution (injected water) can be increased. For this reason, the zinc ion concentration of the reactor water in the RPV 41 can be increased in a shorter time.

  Since the aqueous carbonate solution is circulated in the closed loop to increase the zinc ion concentration of the aqueous carbonate solution, it is necessary to increase the zinc ion concentration using high-concentration boric acid water as described in JP-A-2003-28985. Absent. For this reason, since high concentration boric acid water is not inject | poured in RPV41, control of the reactor power in a BWR plant is simplified.

  In this embodiment, since the flow rate of the aqueous carbonate solution supplied from the carbon dioxide dissolution tank 2 to the zinc dissolution tank 3 through the pipe 4 can be adjusted, the time required to increase the zinc ion concentration of the aqueous carbonate solution to the set zinc ion concentration. Can be shortened. Further, after the zinc ion concentration of the aqueous carbonate solution has increased to the set zinc ion concentration, the flow rate of the aqueous carbonate solution in the zinc dissolution tank 3 can be adjusted to be slow. As a result, it is possible to reduce the load on the circulation pump 6 that supplies the carbonic acid aqueous solution from the carbon dioxide dissolution tank 2 to the zinc dissolution tank 3, and to reduce the power consumed by the circulation pump 6.

  In the present embodiment, the dissolution of carbon dioxide gas and the dissolution of zinc are performed in separate dissolution tanks, that is, an aqueous carbonic acid solution is generated by dissolution of carbon dioxide gas in the carbon dioxide gas dissolution tank 2, and this carbon dioxide is dissolved in the zinc dissolution tank 3. Since zinc is dissolved using an aqueous solution, it is possible to easily adjust the carbonic acid concentration of the aqueous carbonic acid solution generated by dissolving carbon dioxide gas, and to easily generate an aqueous carbonic acid solution containing a predetermined concentration of zinc ions. it can.

  According to the present embodiment, when the temperature of the carbonic acid aqueous solution in the carbon dioxide gas dissolution tank 2 rises due to the influence of the surrounding ambient temperature rise and the saturated solubility of zinc in the carbonic acid aqueous solution decreases, the injection liquid tank 39, the aqueous carbonate solution not containing zinc is injected from the carbonated water injection pipe 32 into the zinc injection pipe 28, so that the zinc ion concentration of the aqueous carbonate solution containing zinc ions flowing in the zinc injection pipe 28 can be reduced. Precipitation of zinc on the inner surface of the injection pipe 28 can be prevented. Further, by constantly supplying a carbonic acid aqueous solution not containing zinc from the constant injection tank 39 to the zinc injection pipe 28, zinc on the inner surface of the water supply pipe 50 near the connection point between the zinc injection pipe 28 and the water supply pipe 50, and in the unlikely event, When carbon dioxide leaks from the carbon dioxide supply pipe 17, it is possible to prevent the precipitation of zinc accompanying the increase in pH of the aqueous carbonic acid solution. In this embodiment, since the carbonic acid aqueous solution (carbonic acid aqueous solution not containing zinc) is injected into the carbonic acid aqueous solution containing zinc ions flowing in the zinc injection pipe 28, the problem caused when injecting pure water can be solved. it can. That is, when pure water is injected into an aqueous carbonate solution containing zinc ions, as described above, the saturation solubility of zinc in the aqueous carbonate solution decreases, so depending on the degree of decrease in the saturation solubility, zinc may be contained in the zinc injection pipe 28. There is a risk of precipitation on the inner surface. In this embodiment, since the carbonic acid aqueous solution is injected into the zinc injection pipe 28, the saturated solubility of zinc in the carbonic acid aqueous solution containing zinc ions flowing through the zinc injection pipe 28 is not observed due to the injection of the carbonic acid aqueous solution. For this reason, in this embodiment, zinc is not deposited on the inner surface of the zinc injection pipe 28 due to the injection of the carbonic acid aqueous solution containing no zinc in the injection liquid tank 39 into the zinc injection pipe 28. The risk of clogging with precipitated zinc in the zinc injection pipe 28 can be significantly reduced, and the zinc injection device 1 can be operated in a stable state.

  In this embodiment, an aqueous carbonate solution containing 350 ppm of zinc ions is injected into the feed water at 3.5 kg / h, which corresponds to a supply rate of 1.2 g / h of zinc ions. Assuming that one operation cycle is 10,000 h, the consumption amount of the solid substance containing zinc is 12 kg for zinc and 15 kg for zinc oxide. In this embodiment, 30 kg of zinc oxide pellets are filled into the zinc dissolution tank 3 during the periodic inspection before the start of the BWR plant. Therefore, it is not necessary to replenish the zinc ion raw material during the plant operation, and zinc during the plant operation. The injection device 1 can be operated continuously.

  In this embodiment, the aqueous carbonate solution containing zinc ions generated as described above in the zinc injection device 1 is injected into the water supply pipe 50, and the supply water containing zinc ions is supplied to the reactor water in the RPV 41. It is possible to reduce the amount of radioactive cobalt attached to the inner surface of the piping 45 and the piping through which the reactor water flows, such as the piping 45 and the purification system piping (not shown) of the reactor purification system. For this reason, the radiation exposure of the worker at the time of the maintenance inspection work of a nuclear power plant can be reduced.

While supplying an aqueous carbonate solution containing zinc ions of a predetermined concentration to the water supply, makeup water is supplied to the carbon dioxide dissolution tank 2 and the aqueous carbonate solution is supplied to the zinc dissolution tank 3, so that the aqueous carbonate solution containing zinc ions is supplied to the water supply. Water injection can be performed continuously. In addition, since it is possible to supply makeup water into the infusion tank 39,
In this embodiment, determination of injection and stop of carbon dioxide into the carbon dioxide dissolution tank 2 and the injection liquid tank 39, determination of the zinc ion concentration of the aqueous carbonate solution, adjustment of the flow rate of the aqueous carbonate solution supplied to the zinc dissolution tank 3, And control of the injection amount of the aqueous carbonate solution containing zinc ions into the water supply pipe 50, control of supply and stop of the makeup water to the carbon dioxide dissolution tank 2 and the injection liquid tank 39, and zinc from the injection liquid tank 39 The control of the injection and stop of the carbonated water solution into the injection pipe 28 is performed by the control device, but it is also possible for the operator to perform a part or all of these control operations. However, it is desirable to use a control device as much as possible from the viewpoint of reducing the burden on the operator.

  The zinc injection method of Example 2, which is another preferred embodiment of the present invention, will be described below. The zinc injection method of the present embodiment is applied to a boiling water nuclear plant (hereinafter referred to as a BWR plant).

  The zinc injection apparatus 1 used in Example 1 is used for the zinc injection method of this example. However, in this embodiment, the diluent injection device 14 of the zinc injection device 1 is used as a pH adjusting device. In the zinc injection method of the first embodiment, the carbonic acid concentration of the carbonic acid aqueous solution in the carbon dioxide gas dissolution tank 2 and the carbonic acid concentration in the injection liquid tank 39 are set to the saturated carbonic acid concentration (pH of the carbonic acid aqueous solution is 3.91, for example). On the other hand, in the zinc injection method of this embodiment, the concentration of carbonic acid in the injection liquid tank 39 is set to the saturated concentration of carbonic acid, and the carbonic acid concentration of the carbonic acid aqueous solution in the carbon dioxide gas dissolving tank 2 is set lower than the saturated concentration of carbonic acid. Yes. Except this point, the zinc injection method of the present embodiment is the same as the zinc injection method of the first embodiment. In order for the diluent injection device 14 of the zinc injection device 1 to function as a pH control device, the control device of the first embodiment uses the carbonic acid concentration of the carbonic acid aqueous solution in the carbon dioxide gas dissolving tank 2 to adjust the carbonic acid concentration in the injection liquid tank 39. A function is required to control the concentration to be lower than the concentration, in other words, to control the concentration of carbonic acid in the injection liquid tank 39 to be higher than the carbonic acid concentration of the carbonic acid aqueous solution in the carbon dioxide dissolution tank 2.

  As in the first embodiment, when the carbon dioxide gas dissolution tank 2 and the injection liquid tank 39 of the pH control device (corresponding to the diluent injection device 14) are full, the control device controls the flow rate adjustment valves 18, 20 respectively. Is opened to adjust the opening degree of each of the flow rate control valves 18 and 20, and supplied from the carbon dioxide supply pipe 17 to the carbon dioxide gas dissolution tank 2 and the injection liquid tank 39 of the pH adjustment device (corresponding to the diluent injection device 14). Adjust each flow rate of carbon dioxide. At this time, the control device sets the opening degree of the flow control valve 18 to a predetermined value so that the carbonic acid concentration of the carbonic acid aqueous solution in the carbon dioxide gas dissolution tank 2 becomes the first initial carbonic acid concentration (for example, the carbonic acid concentration corresponding to pH 4.5). Adjust to the first opening. Further, the control device opens the flow rate control valve 21 so that the carbonic acid concentration of the aqueous carbonic acid solution in the injection liquid tank 39 becomes the second initial set carbonic acid concentration (for example, the carbonic acid concentration corresponding to pH 3.91). The opening is adjusted to a predetermined second opening. The predetermined second opening is larger than the predetermined first opening. While the carbonated water solution containing zinc ions is injected into the water supply pipe 50, the opening of the quantity control valve 18 is held at a predetermined first opening, and the opening of the flow control valve 21 is held at a predetermined second opening. The By controlling the respective opening degrees of the flow rate control valves 18 and 20 by the control device described above, the carbonic acid concentration of the carbonic acid aqueous solution in the injection liquid tank 39 becomes higher than the carbonic acid concentration of the carbonic acid aqueous solution in the carbon dioxide gas dissolving tank 2.

  When the control device determines that the carbonic acid concentration of the carbonic acid aqueous solution in the carbon dioxide gas dissolving tank 2 has reached the first set carbonic acid concentration based on the measured value of the conductivity meter provided in the carbon dioxide gas dissolving tank 2, the circulation pump 6 is turned on. To drive. By driving the circulation pump 6, the aqueous carbonate solution in the carbon dioxide dissolution tank 2 is supplied to the zinc dissolution tank 3 through the pipe 4. An aqueous carbonate solution in which the aqueous solution of carbonate dissolves and circulates zinc contained in the zinc oxide pellets while contacting the zinc oxide pellets in the zinc dissolution vessel 3 while circulating in a closed loop including the carbon dioxide dissolution vessel 2 and the zinc dissolution vessel 3 The zinc ion concentration is increased. When the concentration of zinc ions contained in the carbonic acid aqueous solution in the closed loop reaches 350 ppm which is the preset zinc concentration, the control device drives the injection pump 29, thereby supplying water from the carbon dioxide dissolution tank 2 through the zinc injection pipe 28. Injection of carbonated water containing zinc ions into the pipe 50 is started.

  When the temperature measured by the thermometer 8 is higher than the set temperature due to the influence of the temperature around the carbon dioxide dissolution tank 2 and the zinc dissolution tank 3 as described above, the control device is the same as in the first embodiment. Then, the on-off valve 34 is opened to drive the pump 33. An aqueous carbonate solution (an aqueous carbonate solution not containing zinc) in the injection liquid tank 39 is injected into the aqueous carbonate solution discharged from the carbon dioxide dissolution tank 2 to the zinc injection pipe 28 through the carbonated water injection pipe 32. Since the carbonic acid concentration of the carbonic acid aqueous solution in the injection liquid tank 39 is higher than the carbonic acid concentration of the carbonic acid aqueous solution in the carbon dioxide dissolving tank 2, the zinc injection pipe 28 is injected by injection of the carbonic acid aqueous solution from the injection liquid tank 39 into the zinc injection pipe 28. The carbonic acid concentration of the carbonic acid aqueous solution containing zinc ions flowing inside increases, and the pH of the carbonic acid aqueous solution decreases. For this reason, not only is the zinc ion concentration of the aqueous carbonate solution flowing in the zinc injection pipe 28 diluted by the aqueous carbonate solution injected from the injection liquid tank 39, but also the carbonate aqueous solution flowing in the zinc injection pipe 28 is reduced due to the decrease in pH. Also by the dissolution of the contained zinc, the precipitation of zinc on the inner surface of the zinc injection pipe 28 is prevented.

  The above-described control device is a first control device that controls the rotational speed of the circulation pump 6, and the carbon dioxide concentration of the aqueous carbonate solution in the infusion tank 39 is controlled by the control of the opening degree of the flow rate control valves 18 and 20. When the temperature measured by the second control device and the thermometer 8 that makes the carbonate concentration of the aqueous carbonate solution higher than the set temperature rises above the set temperature, the on-off valve 34 is opened and the pump 33 is driven to drive the injection liquid tank 39. A third control device for injecting an aqueous carbonate solution (a carbonate solution not containing zinc) into the zinc injection pipe 28 is included.

  When the liquid level of the carbonic acid aqueous solution in the carbon dioxide gas dissolution tank 2 is lowered to the first lower limit set liquid level by injecting the carbonic acid aqueous solution in the carbon dioxide gas dissolution tank 2 into the water supply pipe 50, replenishment as in the first embodiment. Water is supplied into the carbon dioxide dissolution tank 2. When the carbonic acid aqueous solution in the injection liquid tank 39 is lowered to the second lower limit liquid level by injecting the carbonic acid aqueous solution in the injection liquid tank 39 into the zinc injection pipe 28, the makeup water is supplied in the same manner as in the first embodiment. Is supplied into the injection liquid tank 39. Thereafter, carbon dioxide gas is supplied into the injection liquid tank 39, and carbonated water having a second set carbonic acid concentration is generated in the injection liquid tank 39.

  In the present embodiment, each effect produced in the first embodiment can be obtained.

  A zinc injection method according to embodiment 3, which is another preferred embodiment of the present invention, will be described with reference to FIG. The zinc injection method of the present embodiment is applied to a boiling water nuclear plant (hereinafter referred to as a BWR plant).

  A zinc injection device 1 </ b> A used in the zinc injection method of the present embodiment is connected to a water supply pipe 50 between the condensate purification device 52 and the low-pressure feed water heater 54 via a zinc injection pipe 28. The zinc injection device 1A has a configuration in which the diluent injection device 14 of the zinc injection device 1 is replaced with a pH adjustment device 59. Other configurations of the zinc injection device 1A are the same as those of the zinc injection device 1.

  The pH adjustment device 59 of the zinc injection device 1 </ b> A includes a carbon dioxide gas injection pipe 36 and a flow rate adjustment valve 37. A flow meter 38 is provided in the carbon dioxide gas injection pipe 36. The carbon dioxide injection pipe 36 is connected to the carbon dioxide supply pipe 17 and the zinc injection pipe 28.

  In this embodiment, an aqueous carbonate solution containing zinc ions is produced in the same manner as in Embodiment 1. The concentration of zinc ions in this aqueous carbonate solution is determined by circulating the aqueous carbonate solution in a closed loop including the carbon dioxide dissolution tank 2 and the zinc dissolution tank 3. To a predetermined zinc ion concentration. Also in the present embodiment, as in the second embodiment, the carbonic acid concentration of the carbonic acid aqueous solution generated by injecting the carbon dioxide gas into the carbon dioxide dissolving tank 2 is lower than the saturated concentration of carbonic acid. In the carbon dioxide dissolution tank 2, the supply of makeup water, the supply of carbon dioxide gas, and the dissolution of zinc in the zinc dissolution tank 3 cause the zinc ion concentration and the carbonate concentration of the aqueous carbonate solution to reach an equilibrium state that has not reached saturation. It has become.

  During operation of the BWR plant, when an aqueous carbonate solution containing zinc ions in the carbon dioxide dissolution tank 2 is injected into the water supply pipe 50 through the zinc injection pipe 28, the ambient temperature of the carbon dioxide dissolution tank 2 and the zinc dissolution tank 3 is Assume that the saturation solubility of zinc decreases and decreases. The temperature measured by the thermometer 8 is input to the control device, and the control device opens the flow rate adjustment valve 37 and injects carbon dioxide from the carbon dioxide supply pipe 17 into the zinc injection pipe 28. The injected carbon dioxide gas is dissolved in a carbonic acid aqueous solution containing zinc ions flowing in the zinc injection pipe 28, and the carbonic acid concentration of the carbonic acid aqueous solution is increased and the pH of the carbonic acid aqueous solution is lowered. For this reason, since zinc is melt | dissolved in carbonic acid aqueous solution in the zinc injection piping 28, it can prevent that zinc precipitates on the inner surface of the zinc injection piping 28. FIG. In addition, in the unlikely event that carbon dioxide leaks from the carbon dioxide supply pipe 17, it is possible to prevent the precipitation of zinc accompanying an increase in the pH of the aqueous carbonic acid solution.

  In the present embodiment, each effect produced in the second embodiment can be obtained. Furthermore, in this embodiment, the pH adjusting device 59 can be simplified in configuration as compared with the diluent injection device 14, and the zinc injection device 1A can be made compact. In the pH adjusting device 59, the injection liquid tank 39, the carbonated water injection pipe 32, and the pump 33 provided in the diluent injection apparatus 14 become unnecessary.

  The zinc injection method of Example 4, which is another preferred embodiment of the present invention, will be described below. The zinc injection method of the present embodiment is applied to a boiling water nuclear plant (hereinafter referred to as a BWR plant).

  The zinc injection apparatus 1 used in Example 1 is used for the zinc injection method of this example. In this embodiment, a thermometer is installed in the feed water pipe 50 in the vicinity of the connection portion between the zinc injection pipe 28 and the feed water pipe 50, and the feed water temperature measured by this thermometer is input as the temperature measured by the thermometer 8. Input to the control device.

  In the present embodiment, as in the first embodiment, an aqueous carbonate solution containing zinc ions is injected from the zinc injection pipe 28 into the water supply pipe 50. In this embodiment, the difference from the first embodiment is the injection of an aqueous carbonate solution containing no zinc from the injection liquid tank 39 to the zinc injection pipe 28.

  The temperature of the carbonic acid aqueous solution flowing in the pipe 4 and the feed water temperature measured by the above-described thermometer provided in the feed water pipe, which are measured by the thermometer 8, are respectively input to the control device. When either the temperature measured by the thermometer 8 or the feed water temperature exceeds the set temperature, the control device opens the on-off valve 34 and drives the pump 33. A carbonate aqueous solution not containing zinc in the injection liquid tank 39 is injected into the zinc injection pipe 28 through the carbonated water injection pipe 32. Thereby, like Example 1, the zinc ion concentration of the carbonic acid aqueous solution containing the zinc ions flowing in the zinc ion injection pipe is diluted, and the vicinity of the zinc ion injection pipe 28 and the connection portion between the zinc injection pipe 28 and the water supply pipe 50. Is prevented from depositing on the inner surface of each of the water supply pipes 50.

  The control of the on-off valve 34 and the pump 33 by the control device considering the feed water temperature in this embodiment can be applied to the second and third embodiments.

  In the present embodiment, each effect produced in the first embodiment can be obtained. Further, since the aqueous carbonate solution containing no zinc is injected into the zinc injection pipe 28 in consideration of the feed water temperature, zinc is injected when the feed water temperature is higher than the temperature of the aqueous carbonate solution containing zinc ions to be sewn. Precipitation of zinc on the inner surface of the water supply pipe 50 in the vicinity of the connection portion between the injection pipe 28 and the water supply pipe 50 can be prevented.

  Each zinc injection method of Examples 1 to 4 can be applied when zinc is injected into a nuclear reactor in a pressurized water source power plant.

  DESCRIPTION OF SYMBOLS 1,1A ... Zinc injection apparatus, 2 ... Carbon dioxide gas dissolution tank, 3 ... Zinc dissolution tank, 4,5 ... Piping, 6 ... Circulation pump, 8 ... Thermometer, 13, 15 ... Liquid level meter, 14 ... Dilution liquid injection Device: 16 ... Carbon dioxide supply device, 17 ... Carbon dioxide supply pipe, 18, 21, 37 ... Flow control valve, 20 ... Carbon dioxide injection pipe, 23 ... Makeup water supply device, 24 ... Makeup water supply pipe, 26 ... Water injection Piping, 28 ... Zinc injection piping, 29 ... Injection pump, 32 ... Carbonated water injection piping, 36 ... Carbon dioxide injection piping, 39 ... Injection liquid tank, 40 ... Reactor, 41 ... Reactor pressure vessel, 42 ... Core, 45 ... recirculation piping, 47 ... main steam piping, 48 ... turbine, 49 ... condenser, 50 ... water supply piping, 59 ... pH adjuster.

Claims (13)

Injecting carbon dioxide into the aqueous carbonate solution present in the first dissolution tank to dissolve the carbon dioxide gas in the aqueous carbonate solution,
Circulating the aqueous carbonate solution in the first dissolution tank through a closed loop including the first dissolution tank and a second dissolution tank in which a solid substance containing zinc exists.
In the second dissolution tank, the zinc contained in the solid substance is dissolved in the aqueous carbonate solution supplied from the first dissolution tank to the second dissolution tank by the circulation,
Supplying the carbonated aqueous solution containing the dissolved zinc to the first dissolution tank by the circulation;
Supplying the aqueous carbonate solution containing zinc in the first dissolution tank to a pipe connected to a reactor pressure vessel through a zinc injection pipe connected to the first dissolution tank;
A zinc injection method comprising injecting an aqueous carbonate solution containing no zinc into the aqueous carbonate solution containing zinc flowing in the zinc injection pipe.   The zinc injection method according to claim 1, wherein a dissolution rate of the zinc from the solid substance containing zinc into the aqueous carbonate solution is controlled by changing a flow rate of the aqueous carbonate solution supplied to the second dissolution tank.   When the liquid level in the first dissolution tank is lowered to the first lower limit set liquid level due to the supply of the aqueous carbonate solution containing zinc circulated in the closed loop to the reactor pressure vessel, the first dissolution tank contains The zinc injection method according to claim 1 or 2, wherein water is supplied and carbon dioxide gas is supplied into the first dissolution tank.   When the liquid level in the second dissolution tank is lowered to the second lower limit set liquid level by injecting the zinc-containing aqueous carbonate solution from the second dissolution tank into the zinc injection pipe, the second dissolution tank contains The zinc injection method according to claim 1 or 2, wherein water is replenished and carbon dioxide gas is supplied into the second dissolution tank. Injecting carbon dioxide into the aqueous carbonate solution present in the first dissolution tank to dissolve the carbon dioxide gas in the aqueous carbonate solution,
Circulating the aqueous carbonate solution in the first dissolution tank through a closed loop including the first dissolution tank and a second dissolution tank in which a solid substance containing zinc exists.
In the second dissolution tank, the zinc contained in the solid substance is dissolved in the aqueous carbonate solution supplied from the first dissolution tank to the second dissolution tank by the circulation,
Supplying the carbonated aqueous solution containing the dissolved zinc to the first dissolution tank by the circulation;
Supplying the aqueous carbonate solution containing zinc in the first dissolution tank to a pipe connected to a reactor pressure vessel through a zinc injection pipe connected to the first dissolution tank;
Either carbon dioxide gas or a carbonic acid aqueous solution having a carbonic acid concentration higher than the carbonic acid concentration of the carbonic acid aqueous solution in the first dissolution tank and not containing zinc is injected into the carbonic acid aqueous solution containing zinc flowing in the zinc injection pipe. And lowering the pH of the aqueous carbonate solution containing zinc in the zinc injection pipe.   The zinc injection method according to claim 5, wherein a dissolution rate of the zinc from the solid substance containing zinc into the aqueous carbonate solution is controlled by changing a flow rate of the aqueous carbonate solution supplied to the second dissolution tank.   When the liquid level in the first dissolution tank is lowered to the first lower limit set liquid level due to the supply of the aqueous carbonate solution containing zinc circulated in the closed loop to the reactor pressure vessel, the first dissolution tank contains The zinc injection method according to claim 5 or 6, wherein water is supplied and carbon dioxide gas is supplied into the first dissolution tank.   When the liquid level in the second dissolution tank is lowered to the second lower limit set liquid level by injecting the zinc-containing aqueous carbonate solution from the second dissolution tank into the zinc injection pipe, the second dissolution tank contains The zinc injection method according to claim 5 or 6, wherein water is supplied and carbon dioxide is supplied into the second dissolution tank.   A first dissolution tank for generating an aqueous carbonate solution, a second dissolution tank filled with a solid substance containing zinc, a closed loop including the first dissolution tank and the second dissolution tank, and the closed loop. A pump device that supplies the aqueous carbonate solution in the first dissolution tank to the second dissolution tank, and injects the aqueous carbonate solution containing zinc in the first dissolution tank into a pipe connected to a reactor pressure vessel. Zinc comprising: a zinc injection pipe; a diluent injection apparatus for injecting a carbonic acid aqueous solution not containing zinc into the zinc injection pipe; and a carbon dioxide supply apparatus for supplying carbon dioxide to the first dissolution tank. Injection device.   The dilution liquid injection device has an injection liquid tank that generates the carbonic acid aqueous solution that does not contain zinc, and a carbonic acid aqueous solution injection pipe that connects the injection liquid tank and the zinc injection pipe, and the carbon dioxide supply device includes the injection The zinc injection device according to claim 9, which is in communication with a liquid tank.   A first dissolution tank for generating an aqueous carbonate solution, a second dissolution tank filled with a solid substance containing zinc, a closed loop including the first dissolution tank and the second dissolution tank, and the closed loop. A pump device that supplies the aqueous carbonate solution in the first dissolution tank to the second dissolution tank, and injects the aqueous carbonate solution containing zinc in the first dissolution tank into a pipe connected to a reactor pressure vessel. A zinc injection pipe, a diluent injection apparatus for injecting a carbonic acid aqueous solution not containing zinc into the zinc injection pipe, a carbon dioxide supply apparatus for supplying carbon dioxide to the first dissolution tank, the carbon dioxide supply apparatus, and the zinc A zinc injection device comprising an injection piping and a carbon dioxide injection piping provided with a flow rate adjusting device.   A control device that controls the flow rate adjusting device to inject the carbon dioxide gas from the carbon dioxide supply device into the zinc injection pipe when the temperature of the aqueous carbonate solution flowing in the closed loop exceeds a preset temperature. The zinc injection device according to 9 or 11. A first dissolution tank for generating an aqueous carbonate solution, a second dissolution tank filled with a solid substance containing zinc, a closed loop including the first dissolution tank and the second dissolution tank, and provided in the closed loop, A pump device that supplies the aqueous carbonate solution in the first dissolution tank to the second dissolution tank, and injects the aqueous carbonate solution containing zinc in the first dissolution tank into a pipe connected to a reactor pressure vessel. A zinc injection pipe, a pH adjusting device for injecting a carbonic acid aqueous solution not containing zinc into the zinc injection pipe, and a carbon dioxide supply device for supplying carbon dioxide to the first dissolution tank,
The pH adjusting device is connected to the carbon dioxide supply device to generate an aqueous carbonate solution containing no zinc, and the aqueous carbonate solution is provided with a flow rate adjusting valve by connecting the injection solution tank and the zinc injection pipe. Has injection piping,
Controlling the first flow rate of the carbon dioxide gas supplied to the first dissolution tank by the carbon dioxide supply device and the second flow rate of the carbon dioxide gas supplied to the injection bath by the carbon dioxide supply device, A zinc injection device comprising: a control device for increasing the carbonic acid concentration of the aqueous carbonic acid solution generated in the injection liquid tank to be higher than the carbonic acid concentration of the aqueous carbonic acid solution generated in the first dissolution tank.

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