JPH06103356B2 - Reactor feedwater iron injection facility for boiling water nuclear power plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is for controlling the iron concentration in feed water by injecting electrolytic iron in a boiling water nuclear power plant in order to reduce the radioactivity concentration in the reactor water. The present invention relates to improvement for making electrolytic iron injection equipment optimal for application to an actual plant.

[Prior Art] Generally, corrosion products such as metal ion components and insoluble components (clads) are eluted from constituent materials such as pipes, pumps and heat exchangers of boiling water nuclear power plants (this specification). In the book, both the metal ion component and the clad are referred to as corrosion products). Most of the corrosion products generated in the turbine system upstream of the condensate purification device are removed by the condensate purification device (condensate filtration device and condensate desalination device), but the water supply system downstream of the condensate purification device. Corrosion products generated in the process flow into the reactor without being purified.

The corrosion products brought into the reactor are deposited and accumulated on the fuel surface due to the boiling evaporation phenomenon of cooling water occurring on the fuel surface. Some of the corrosion products attached to the fuel surface are irradiated with neutrons and become radioactive substances. For example, corrosion products such as Ni and Co become radioactive substances with a long half-life such as ⁵⁸ Co and ⁶⁰ Co by neutron irradiation. Some of the corrosion products that have become radioactive due to the adhesion to the fuel rods are eluted or released again into the cooling water (reactor water) to circulate the reactor water. It becomes a radiation source by accumulating and accumulating on the inner surface of the equipment and piping of the reactor water purification system that purifies some of the impurities in the reactor water.

When the concentration of radioactive material in the reactor water increases, the amount of radioactive material that adheres and accumulates on the inner surface of the above-mentioned constituent materials increases, and the amount of radiation in the equipment piping increases. As a result, the dose received by workers when conducting inspections of equipment and piping will also increase.

Therefore, a technique for operating a plant while keeping the radioactive substance concentration in the reactor water as low as possible has been developed and applied.

As one example, in order to reduce the amount of Fe generated, which accounts for the majority of corrosion products, the amount of corrosion products such as low alloy steel or weathering steel is reduced in place of conventional carbon steel pipes. The use of materials is done. Furthermore, in order to effectively remove the generated corrosion products, the condensate purification device is a double type that combines a filter and a desalting device.

In addition, in the water supply system downstream of the condensate purification device that cannot purify the newly generated corrosion products, oxygen gas is injected into the cooling water to make them coexist, forming a protective film with a corrosion suppression effect on the material surface, and generating corrosion. It suppresses the generation of objects.

On the other hand, a measure to reduce the amount of ⁶⁰ Co, which is a species with a long half-life, by using a material with a low content of ⁵⁹ Co is also adopted.

In a plant that adopted such measures to reduce corrosion products, the amount of corrosion products flowing into the reactor could be reduced, but the radioactive material concentration in the reactor water will be stabilized at a higher level than before. A phenomenon was seen.

As a result of investigating this factor, the amount of Ni and Co generated from the stainless steel feedwater heater tube located downstream of the condensate purification device or stainless steel, and the structural material inside the reactor using Inconel material It is considered that the reason is that the amount of Fe corrosion products is greatly reduced. Further, it was proved that the above estimation was correct because the concentration of radioactive substances in the reactor water decreased as a result of increasing the iron concentration in the feed water by performing the partial bypass operation of the condensate purification device described above. Therefore,
A method of controlling the Fe concentration in the feed water according to the amounts of Ni and Co generated from the feed water heater tube and the reactor internal structure is currently applied (eg Hitachi review).
vol70, No. 4 (1988), p417-419).

One method of controlling the Fe concentration in the feed water is the partial bypass operation of the condensate purification device described above. In this case,
Of the dual condensate purification devices consisting of a filter and a demineralizer, only the filter can be bypassed. If the cooling pipe of the condenser on the upstream side of the condensate purification device is damaged,
This is because it is necessary to prevent the seawater used as cooling water from mixing with the reactor water, and in case of emergency, bypass operation of the condensate demineralizer is not preferable. Therefore, control of the Fe concentration in the feed water by bypass operation of the condensate purification device is bypass operation of only the upstream filter, and operation is via the desalinator installed downstream. In this case, the controllability of the Fe concentration in the feed water depends on the change in the iron removal performance of the desalting device that cannot be bypassed, and there is a problem that the concentration control is difficult.

As another method for controlling the Fe concentration in the feed water, a method of directly injecting Fe into the feed water has been considered and adopted. An outline of an apparatus disclosed in Japanese Patent Application Laid-Open No. 62-226099 as an iron ion generating apparatus for injecting iron into the water supply will be described with reference to FIG.

The equipment is CO ₂ gas injection source water tank 1, iron plate electrode electrolysis tank 2, CO ₂
It is composed of the diffuser 3. CO ₂ gas injection source water tank 1 has C at the bottom
A nozzle 4 capable of injecting O ₂ gas is provided. A plurality of iron plates 5 having high purity are installed in parallel in the iron plate electrode electrolyzer 2, and a nozzle 6 capable of feeding an inert gas (N ₂ or Ar) is provided in the lower part. The CO ₂ diffuser 3 is provided with a nozzle 7 at the bottom thereof, which can feed an inert gas (N ₂ or Ar) to diffuse the CO ₂ gas. First, CO ₂ gas is bubbled through the nozzle 4 into previously degassed pure water supplied to the CO ₂ injection source water tank 1 from the inlet pipe 1 ′ or normal pure water so that the pure water absorbs CO ₂ gas. . Absorption adjusts the CO ₂ gas partial pressure in the vessel in accordance with the CO ₂ gas of a predetermined amount is proportional to the partial pressure of CO ₂ gas. Pure water, which has absorbed CO ₂ and has increased conductivity, enters the next electrolytic cell 2. The Fe ions can be eluted at a low applied voltage by flowing the pure water having a high conductivity between the electrodes. Since a film may be formed on the electrode at the same time as Fe elution, the polarity of the electrode is controlled by an external DC power supply so that it can be periodically reversed. Furthermore, the nozzle 6 under the electrode
A gas such as N ₂ or Ar is blown in to strip the O ₂ gas during electrolysis and remove the deposits on the electrode. The arrangement of the iron plate electrodes may be a double pole system in which a DC power source is connected to both ends or a single pole system in which a power source is connected to each electrode. The former is preferable for this selection when the conductivity of the liquid is high.

Fe ion-containing water containing CO ₂ gas generated in the electrolytic tank 2 to dissipate the CO ₂ gas in the gas N _2, Ar or the like in the following CO ₂ dissipator. The pH of the liquid rises with CO ₂ emission, and Fe ions may promote the precipitation of iron hydroxide. This is because Fe ³⁺ ions are generated as a precipitate in Fe ions.

By this device and operation, a liquid in which iron ions are dissolved in pure water can be generated and delivered from the outlet pipe 3 '.

[Problems to be Solved by the Invention] In order to apply the electrolytic iron ion generator described in Japanese Patent Laid-Open No. 62-226099 to an actual plant as a feed water iron injection device, it is necessary to use an existing facility in the actual plant. Connection conditions,
There is a shortage of equipment necessary for long-term operation and maintenance, or equipment for maintaining the safety of the iron injection device and the plant, and specifically, there are the following problems.

Issue 1: Figure 3 shows the results of an electrolytic ionic iron implantation test that simulated the actual plant conditions conducted by the inventors. The horizontal axis shows the iron injection concentration injected from between the condensate purification device and the feed water heater, and the vertical axis shows the iron analysis value at the reactor feed water inlet. As shown by the black circled graph in this figure, when injected into the feed water in the form of electrolytic iron ions, ionic iron adheres to the injection pipe and the pipe part after the injection point, and the injection efficiency is low at about 30%, It was confirmed that it was not. Therefore, it is necessary to improve the injection efficiency and provide a facility that enables stable injection operation.

Second issue: In the case of an actual plant, the stored water in an outdoor tank will be used as the water source for the electrolyte, and the temperature will change depending on the season. A change in the temperature of the electrolytic solution affects the conductivity of the electrolytic solution, and in particular, a decrease in the solution temperature causes a decrease in electrolytic efficiency. Therefore, in order to perform stable operation for a long period of time, it is necessary to keep the temperature of the electrolytic solution constant.

Problem No. 3: Balance between the amount of water supplied to the feed iron injection device and the amount of water injected from the device (the balance between the amount of water supplied to 1'and the amount of water discharged from 3'in Fig. 2) In consideration of the above, as shown in FIG. 3, the injected iron tends to adhere to the inner surface of the injection pipe, so the resistance of the injection pipe increases over time, and the amount of water supplied to the iron injection device may become excessive. There is a nature.
On the contrary, when the amount of water supplied to the feed water iron injection device becomes insufficient, the water level in the electrolysis cell lowers, resulting in a decrease in electrolysis efficiency, or injecting water containing air into the reactor water supply system. Fear may occur and interfere with plant operation. Therefore, for long-term stable operation, it is necessary to maintain a balance between the feed water entering the feed water iron injecting device and the inject water exiting therefrom.

Problem No. 4: In order to perform nighttime operation and continuous operation such as holidays, it is necessary to be able to operate safely even in the unlikely event of equipment failure or to automatically stop equipment. There is.

An object of the present invention is to solve the above problems and provide a reactor feedwater iron injection facility suitable for being applied to an actual plant.

[Means for Solving the Problems] The contents devised in the present invention in order to make the feedwater iron injection device applicable to an actual plant are shown below.

In order to improve the injection efficiency, which is the first problem, the following solution is adopted. That is, according to the result of the simulation test shown in FIG. 3 conducted by the inventors, oxygen gas was blown into the electrolyte containing iron ions generated by electrolysis as shown by the white circled graph in FIG. It was confirmed that the injection efficiency increased up to about 80% when solidified (that is, clad) as the oxide or hydroxide was injected. It is presumed that this is due to the effect of stabilizing the iron by using the iron clad as compared with the iron ion.

Based on the above facts, in the present invention, iron, which has been conventionally injected as iron ions into the water supply, is injected in the form of an iron clad. For this purpose, a facility is provided in which injected water containing iron ions is temporarily stored in a container and oxygen gas or air can be blown into the container.

Next, in order to prevent the temperature drop of the electrolytic solution, which is the second problem, equipment for adjusting the electrolytic solution to a constant temperature is provided before the electrolytic solution is supplied to the electrolytic cell. As a concrete means, the temperature can be adjusted by a combination of a heating device and a thermostat.

In order to solve the third problem, the feed water amount to the feed water iron injecting device and the injecting water amount from the iron feeding device are accurately controlled, or the water level in each tank is detected and controlled. In the former case, a highly accurate flow rate control device is required, and it is difficult to cope with a change in the water level due to leakage of the electrolytic solution in the device. Therefore, it is considered realistic to detect the water level in each tank and correct the water level abnormality as in the latter case.

For the fourth issue, we will examine whether the occurrence of an abnormality in the water supply iron injecting facility will hinder the operation of the facility or whether it will hinder the maintenance of the integrity of the facility. , The abnormality detection means and the automatic abnormality elimination means are set for those that are considered to cause problems. Specifically, the following items require abnormality detection and abnormality elimination means.

(1) Abnormality of electrolytic solution heating equipment (2) Abnormality of electrolytic voltage (3) Abnormality of water level (4) Abnormality of injection pressure (5) Leakage of electrolytic solution [Action] Ni, Co, etc. brought into the reactor with water supply Corrosion products adhere to the fuel surface and become radioactive substances by neutron irradiation, which are again eluted into the reactor cooling water and adhered and accumulated on the inner surfaces of equipment and pipes outside the reactor pressure vessel. As described above, the radiation dose rate is increased. By the way, if the corrosion products of Ni and Co attached to the fuel surface are attached and accumulated on the fuel surface as complex oxides of Fe ₂ NiO ₄ and Fe ₂ CoO ₄ , they will be eluted again into the reactor cooling water. The rate at which the fuel adheres is remarkably slowed down, and the fuel adheres and accumulates on the fuel surface for a long period of time, and as a result, re-adhesion and accumulation on the above-mentioned equipment and the inner surface of the pipe is suppressed. To do this, iron is injected into the feed water so that the weight ratio of Fe / Ni in the feed water is 2 or more (actually a little more than about 3) so that Ni and Co can form the above stable composite oxide. It is necessary to. (In the cooling water, the Co concentration is about 1% of the Ni concentration, so the Co and Ni concentrations are represented by the Ni concentration.) This is the basic principle of the feed water iron injection technique, and the present invention is also based on this basic principle. It is a thing.

In the present invention, in view of the test results shown in FIG. 3, the injection efficiency is increased by injecting iron into the reactor feedwater in the form of clad rather than the form of ion. By controlling the temperature of the water supplied to the electrolyzer, the electrolysis efficiency is kept stable and high. By detecting and adjusting the water level in the reaction tank, we will balance the amount of water supplied to and from the water supply iron injection equipment. During operation of the equipment, if an abnormal condition out of the allowable value occurs, stop the equipment of the equipment or isolate the equipment system.

[Embodiment] An embodiment of a water supply iron injection facility according to the present invention is shown in FIGS.
It will be described with reference to the drawings.

In the figure, a CO ₂ injection source water tank 1, an electrolytic tank 2 and a reaction tank 8 are connected by pipes 13 and 14. The supply water that has entered the tank 1 from the pipe 36 has its conductivity increased by blowing carbon dioxide gas from the nozzle 4, then enters the electrolytic tank 2 through the pipe 13, and flows between the iron plate electrodes 5 arranged in parallel, The electrolysis causes iron ions to elute into it. An inert gas such as nitrogen gas or argon gas is blown into the tank 2 from a nozzle 6 below the electrode to strip oxygen gas during electrolysis and remove deposits from the electrode. The iron plate electrodes may be arranged in a double pole system in which a DC power source is connected to both ends, or in a single pole system in which a DC power source is connected to each electrode. The iron ion-containing water produced in the electrolysis tank 2 enters the reaction tank 8 through the pipe 14, where the nozzle 8 '
By injecting air from the iron, the iron ions are converted into iron hydroxide or iron oxide to be clad. From the exhaust pipe 55 above the tanks 2 and 8, the supplied carbon dioxide gas, inert gas, and air are exhausted. The water containing the cladized iron produced as described above is injected into the water supply to the reactor through the pipe 56 and the injection pump 15. The reaction tank 8
Oxygen may be blown into the air instead of air.

The device according to the invention will be described in more detail.

The electrolytic iron produced in the electrolysis tank 2 is finally clad in the reaction tank 8 and injected into the reactor water supply, so it is not necessary to use degassed water as the water supplied from the pipe 36. Therefore, in the case of an actual plant, a pure water tank water in which industrial water is filtered and desalted and stored or a condensate storage tank in which water in the plant is collected and stored can be directly used as a supply water source.

In the pure water tank water or the condensate storage tank water, the dissolved oxygen concentration is usually 1 to 5 ppm dissolved from the atmosphere. Therefore, when the water from the water source is used, iron in the outlet water of the electrolytic cell 2 has about 50% of the clad component.
The inventors confirmed the conditions for further increasing the ratio of clad iron to 90% or more in the reaction tank 8 and found that a reaction time of about 20 minutes or more in the state of an air blowing amount of 0.1 air / h / l (electrolytic solution). It was decided that time was needed. Therefore, the reaction tank 2 provided on the downstream side of the electrolytic tank 2 needs to have a capacity capable of ensuring a reaction time with oxygen of 20 minutes or more.

In addition, it was confirmed that it is effective to provide a stirrer in the reaction tank in order to improve the reactivity and to carry out the reaction while stirring the electrolytic solution.

It is desirable that the temperature of the electrolyte is controlled to be constant so that there is no seasonal variation. That is, the temperature of pure water storage tank or condensate storage tank water is 3 ° C throughout the year.
We are experiencing changes in the range of ~ 20 ° C. Therefore, in order to prevent seasonal fluctuations, it is desirable to keep the water temperature at 20 ° C or higher. When electrolysis was carried out at a water temperature of 20 ° C, the electrolysis efficiency that contributed to the generation of iron was confirmed to be a good result of about 80%.

As a means for controlling the temperature of the electrolytic solution, for example, as shown in FIG. 4, an electric heater 16 is provided in the CO ₂ injection source water tank 1,
By monitoring the water temperature of the tank with a thermometer 17 and automatically controlling the thermostat of the controller 20 to activate the heater when the temperature is below the target temperature and to stop the heater when the temperature exceeds the target temperature, electrolysis The temperature of the electrolytic solution in the tank 2 can be adjusted. In addition, if a controller that automatically changes the heater current depending on the difference between the water temperature and the target temperature is used, the water temperature adjustment accuracy is improved.

The water levels in the CO ₂ injection source water tank 1, the electrolytic tank 2 and the reaction tank 8 are adjusted as follows. In order to easily adjust the water levels of these tanks, as shown in FIG. 5, the upper water levels of the tanks should be matched in advance, and the connecting pipes 13 should be connected between the tanks.
14 or weirs (see, for example, FIG. 1) are connected so that when the water level in one of the tanks changes, the electrolytic solution can move so that it becomes equal to the water level in the other tank. Also, it is desirable to install the connecting pipes or weirs between the tanks in consideration of the purpose of each tank. For example, the connecting pipe 13 between the CO ₂ injection source water tank 1 and the electrolysis tank 2 has one end connected to the upper portion of the CO ₂ injection source water tank 1 from the viewpoint of CO ₂ gas absorption and temperature adjustment efficiency. It is desirable to connect the other end to the lower part of the electrolytic cell 2 in order to match the upward flow of N ₂ gas with the flow direction of the electrolytic solution. The connecting pipe 14 between the electrolytic cell 2 and the reaction cell 8 is
Since it is necessary to take out water containing iron after the electrolysis is completed, it is desirable to take out the water from the upper part of the electrolytic bath 2 (upper part of the electrode) and connect it to the reaction bath 8.

With the above structure, detection of water level in each tank 1, 2, 8
The monitoring can be performed by detecting and monitoring the water level of the reaction tank 8 among these three tanks. Therefore, this will be described below.

The upper limit water level in the reaction tank 8 can be maintained by controlling the inlet water flow rate based on the detection result of the upper limit water level meter 11 or by the overflow line 12. As a result, even if the amount of water supplied to the CO ₂ injection source water tank 1 is too large compared to the amount of water injected from the reaction tank 8 to the reactor feedwater, it is possible to prevent water from leaking from each tank. On the other hand, in order to prevent air from entering the reactor water supply system, the reaction tank 8
It is necessary to provide a lower limit water level gauge 9 above the point where the injected water is taken out from and to monitor so that the water level does not fall below the lower limit water level due to excess flow rate of the injected water from the reaction tank 8. Further, the intermediate water level gauge 10 provided between the upper limit water level gauge 11 and the lower limit water level gauge 9 shown in FIG. 5 is a reaction tank for backing up the lower limit water level gauge 9 or for stabilizing the cladding rate. It is provided considering that it will be used to maintain the amount of water.
In this case, the injection pump 15 works at the water level of the intermediate water level gauge 10 or more, and the injection pump 15 stops at the water level of the intermediate water level gauge 10 or less, so that the device is the upper water level gauge 11 or the water level of the overflow line 12. It becomes possible to operate between the intermediate water level gauges 10.

The abnormality monitoring equipment for monitoring and automatically operating the above-mentioned water supply iron injecting equipment will be described in detail below with reference to FIG.

It is necessary to detect and respond to abnormality in electrolyte heating equipment, abnormality in electrolytic current, abnormality in water level, abnormality in injection pressure, leakage of electrolyte, and the following measures are taken for that purpose.

First, the abnormality of the electrolytic solution heating equipment will be described. Monitor the indicated value of the thermometer 17 as the temperature of the electrolyte in the detection line 19,
It is judged by the control device 20 whether or not it exceeds the upper limit temperature in consideration of the allowable fluctuation range in the adjustment target temperature, and when it is determined that the upper limit temperature is reached and the abnormality of the heating equipment has occurred, the heating equipment A signal for stopping the operation is sent from the control device 20 to the control line 21.
Then, the heating heater 16 is turned off.

Secondly, in the monitoring of the electrolytic voltage abnormality, the electrolytic voltage is constantly monitored by the detection line 22, and the control device 20 judges whether or not the electrolytic voltage is equal to or higher than a preset upper limit value, and exceeds the upper limit value. In this case, a signal for stopping the electrolysis power supply 31 is sent through the control line 23 to stop the power supply.

Thirdly, regarding the water level abnormality, the signal of the lower limit water level gauge 9 of the reaction tank 8 described above is sent to the control device 20 through the detection line 24, and the equipment inlet valve 26 and the outlet valve 27 are closed through the control line 25 and Stop infusion pump 15. In this case, the equipment is substantially stopped, so it is desirable to stop the electrolytic power supply, the heater power supply, and the like.

Fourth, regarding the injection pressure abnormality, the system pressure of the injection line is monitored by the pressure gauge 28, and whether or not the preset pressure is exceeded is constantly monitored by the detection line 29. When the pressure becomes high, the control line This can be dealt with by providing control equipment for stopping the injection pump 15 and stopping the operation of the entire equipment at 30.

Fifth, regarding the leakage of the electrolytic solution, the electrolytic solution leaked from the feed water iron injection equipment is received by the receiving tray 32 provided at the lower part of the equipment, and the water level of the electrolytic solution received by the receiving tray 32 or the electrolytic solution received by the receiving tray 32 is received. A detector to detect the presence or absence of the water level in the tank 33 that is received downstream again
Always monitor with 34, by this, the signal of the presence or absence of the above-mentioned leakage is sent to the control device 20, and when the electrolyte leakage is detected,
The control device closes the inlet valve 26 to stop the supply of water, and performs an operation to stop the equipment.

For each of the above five abnormalities, it is often difficult to continue sound operation of the feedwater iron injection equipment regardless of which abnormality occurs, and it is necessary to stop the entire feedwater iron injection equipment and isolate the system by detecting one abnormality. Is desirable. In this case, by detecting one abnormality, the heating equipment is stopped, the electrolysis power supply is stopped, the injection pump is stopped, and the inlet valve and the outlet valve of the water supply iron injection equipment are closed to isolate the system. Further, if an alarm generating facility that operates upon detection of an abnormality is added, the facility can be repaired and restored at an early stage.

Now, an embodiment of the case of applying the water supply iron injection facility of the present invention to an actual plant will be described below with reference to FIG.

In Fig. 1, the demineralized water used as the electrolytic solution and the injection water is supplied from the supply water tank (not shown) to the water supply iron injection facility.
It is supplied to the CO ₂ injection source water tank 1 by a supply water pipe 36. In this case, if the pressure of the supply water tank is insufficient, it is necessary to add a supply water pump to the supply water pipe 36. Since a general nuclear power plant has a supply water tank and a supply water pump as existing equipment, it is not necessary to add a supply water pump, so it is omitted in FIG. The inlet valve 37 is provided for manually isolating the system when the water supply iron injection equipment is not used, such as during a regular inspection period. The automatic valve 26 is a valve that is activated when system isolation becomes necessary during automatic operation of the feedwater iron injection facility. The type of valve may be an automatic valve such as a solenoid valve or an electric motor valve.

The flow rate control valve 38 is a valve necessary for adjusting the amount of water supplied to the water supply iron injection facility. The flow rate is adjusted by the indicated value of a flow meter 39 provided downstream of the flow rate adjusting valve 38. The electric water supplied to the CO ₂ injection source water tank 1 is heated by an electric heater 16. The temperature is adjusted based on the result detected by the thermometer 17, and a temperature control device having a built-in thermostat is provided to adjust the temperature to the set temperature. At the same time as this temperature adjustment, in order to obtain a sufficient conductivity to electrolyze the iron electrode 5 in the electrolysis tank 2 located downstream, CO ₂
Carbon dioxide gas is blown in from the lower part of the pressurization source water tank 1. The carbon dioxide gas is supplied from a plurality of carbon dioxide gas cylinders 40, and is supplied via a carbon dioxide gas supply pipe 41, a flow meter 42, a flow rate control valve 43, and a check valve 44 capable of preventing backflow of water when the carbon dioxide gas is stopped.

The feed water after adjusting the temperature and the conductivity is guided to the lower part of the electrolytic cell 2 through the pipe 13 and rises between the electrodes 5. in the meantime,
A current is supplied to the electrode 5 from the DC power supply 31, and iron ions are eluted in the electrolytic solution. Further, nitrogen gas is blown into the electrolytic solution from the lower part of the electrolytic cell 5 to operate while suppressing adhesion of scale to the iron electrode surface. Nitrogen gas is supplied to the electrolyzer 5 from a plurality of nitrogen gas cylinders 45 through the supply pipe 4
6, through a flow meter 47, a flow rate control valve 48, a check valve 49. The electrolytic solution containing iron ions and the like after electrolysis is guided to the reaction tank 8. The electrolysis tank 2 and the reaction tank 8 may be connected by the pipe 14 as shown in FIG. 5, but iron may adhere to the inside of the connecting pipe and may be blocked.
FIG. 1 shows an example in which they are connected by a weir. Therefore, the electrolytic solution containing electrolytic iron overflows into the reaction tank 8 from the upper part of the electrolytic tank 2 over the weir. Therefore, even if the water in the reaction tank 8 is exhausted, the electrolysis tank 2, CO ₂
It is possible to prevent the pressurization source water tank 1 from running out of water,
It is possible to prevent the phenomenon of 16 overheating or abnormal increase in electrolytic voltage.

The water containing electrolytic iron ions introduced into the reaction tank 8 is stirred by a stirrer 50.
At the same time, the air is blown from the compressed air system in the power plant, and iron ions become iron hydroxide or iron oxide to form a clad. Air supply is provided by the supply pipe 51,
This is performed via a flow meter 52, a flow rate control valve 53, and a check valve 54.

The carbon dioxide gas supplied to the CO ₂ injection source water tank 1, the nitrogen gas supplied to the electrolysis tank 2 and the air supplied to the reaction tank 8 are
The exhaust pipe 55 provided in the upper part of the electrolysis tank 2 and the reaction tank 8 guides it to an exhaust system duct in a building, and is discharged.

The water level adjustment in the reaction tank 8 will be described. The lower limit water level and the intermediate water level are detected by the electrode type water level gauges 9 and 10. The upper limit water level is adjusted in the overflow line 12 in FIG. 1. The operation of the injection pump 15 is performed when there is water between the intermediate water level and the upper water level in the reaction tank 8.
Care should be taken not to inject air into the water supply system, and the lower limit water level gauge 11 should stop the injection pump 15 assuming that the intermediate water level gauge 10 did not operate for some reason. Therefore, if it is not necessary to consider the above concern, the lower limit water level gauge 9 or the intermediate water level gauge 10 may be deleted. In the example shown in FIG. 1, an electrode type water level gauge is shown, but a float type water level gauge may be adopted. If the float type water level meter is used for a long period of time, electrolytic iron in the reaction tank may adhere to the operating part and cause malfunction, so periodic inspection is necessary.

The injected iron sufficiently clad in the reaction tank 8 is injected into the reactor water supply pipe 61 through the injection pipe 56, the injection pump 15, the flow control valve 59, and the injection pipe main valve 60. When a reciprocating pump is used as the injection pump 15, the injection pressure pulsates, so an air chamber 57 is provided to prevent pulsation. Further, an automatic valve 27 is provided to isolate the system when the water supply iron injection equipment is abnormal, and a check valve 58 is provided to prevent backflow of water supply into the water supply iron injection equipment due to a failure of the injection pump 15.

On the other hand, a flushing pipe 62 for discharging the injected iron remaining in the injection pipe is provided on the check valve downstream side and on the feed water iron injection facility side. The flushing pipe 62 is usually provided with a stop valve 63 because it is not necessary to flow the injected water.

In addition, the reaction tank 8 and the electrolysis tank 2 are inspected when checking the water supply iron injection equipment.
And stop valves 64, 6 for draining water from the CO ₂ injection source water tank 1
Drain pipes 67, 68, 69 with 5, 66 are installed at the bottom of each tank.

In order to detect water leakage from each tank of the water supply iron injection equipment, a receiving tray 32 and a detector 34 for detecting leaked water received in the receiving tray 32 when water leakage occurs are provided. The tray 32 shown in FIG. 1 receives the leaked water during normal operation, the drainage water from the drainage pipes 67, 68, 69 of each tank during the inspection, and the flushing water from the flushing pipe 62. This is shown as an example in the case of a structure that doubles as.

The drain water under inspection is discharged from the tray 32 through the drain pipes 69 and 70 with the stop valve 68 opened to the drain discharge port 71 in the building.

By using the above-mentioned water supply iron injection equipment, it is possible to clad electrolytic iron, stable injection operation can be achieved, stable electrolytic conditions can be achieved by adjusting the temperature of the electrolytic solution, and air can be mixed into the water supply system. Water level control for prevention can be achieved, and it will be a feedwater injection facility that can be automatically operated in an actual plant.

Next, an example of the system configuration of the above operation of the feed water iron injecting equipment, automatic monitoring of the operation state, and automatic stop will be described with reference to FIG.

First, the infusion pump system sends a signal from the switch 72, which manually shuts down the infusion pump 15, to the AND circuit 73,
Send to infusion pump power supply 75 via R circuit 74. At this time, if the "high" water level signal generated when the water level in the reaction tank 8 is equal to or higher than the intermediate water level of the intermediate water level gauge 10 is guided to the AND circuit 73, the injection pump 15 is operated. Also, the intermediate water level gauge 10
If it is lower than the water level of, the OR circuit 77, the wipeout 78, the OR circuit 74, and the NOT circuit 7 are generated by the signal of the infusion pump switch 72 led to the AND circuit 76 and the signal of “middle” of the intermediate water level gauge 10.
The operation of the injection pump 15 is stopped via 9. The electrolyte temperature is adjusted by turning on the power switch 80 of the heater 16 and connecting the heater 16 to the heater power supply 83 via the temperature indicating controller 81 and the thermostat 82. Further, the inlet automatic valve 26 and the outlet automatic valve 27 of the water supply iron injection equipment are operated by respective power sources 88 and 89 via the OR circuits 86 and 87 by the signals of the switches 84 and 85 on the control panel. Is activated. Similarly, the operation of the DC power supply for electrolysis and the agitator of the reaction tank are performed by switches 90 and 91 on the control panel, respectively.
It is performed via the OR circuits 92 and 93, the DC power supply 94 and the agitator power supply 95.

These injection pumps, heaters for heating, iron injection equipment inlet and outlet valves, DC power supply, stirrer circuit, the signal of the lower limit water level meter 9 of the reaction tank, the signal of abnormal voltage from the electrolytic power supply device 31, CO ₂ OR circuit 96, 77, 97, 98, 99, 100, wipeout 7 for abnormal signal of thermometer 17 of injection source water tank, abnormal signal of pressure gauge 28 in injection line and abnormal signal of water leak detector 34
8, 101, 102, 103, 104, and NOT circuits 79, 105, 106,
By introducing into the injection pump power supply 75, the heating heater power supply 83, the inlet automatic valve (closed) power supply 88, the outlet automatic valve (closed) power supply 89, the DC power supply 94 and the agitator power supply 95 via 107 and 108, respectively. By any of the above abnormalities, the shutdown and system isolation of the water supply iron injection facility can be achieved.

Further, an abnormal signal of the lower limit water level gauge 9 of the reaction tank, an abnormal signal from the electrolytic power supply device 31, an abnormal signal of the thermometer 17 of the CO ₂ injection source water tank, an abnormal signal of the pressure gauge 28 in the injection line, and a water leakage detector. When an abnormal signal from 34 is generated, each signal is sent to the alarm means 109, 110, 111, 112, and 113,
Make sure to generate an alarm.

By adopting the system configuration as shown in FIG. 6, it is possible to automatically detect the abnormality of the equipment and automatically stop the abnormality when the abnormality occurs.

Next, an embodiment in which simplification of equipment is considered without impairing the object of the present invention will be described below.

Specifically, as shown in FIG. 7, by using a reciprocating pump having an injection pressure adjusting function, an injection flow rate adjusting function, and a backflow prevention function as the injection pump 15, the pressure gauge 28 and the check valve of FIG. The valve 58 and the flow control valve 59 are omitted. Further, by providing a facility having a function of setting an upper limit of the electrolysis voltage as the DC power supply 31 for supplying the electrolysis current, the management system for the electrolysis voltage is omitted.

As a result of the above, as shown in FIG.
Only three cases of monitoring by the lower limit water level meter 9 of the reaction tank, the thermometer 17 of the CO ₂ injection source water tank and the water leakage detector 34 are required.

As still another embodiment, a configuration in which the equipment is most simplified is shown in FIGS. 9 and 10 without impairing the object of the present invention.

In FIG. 9, the lower limit water level gauge 9 of the reaction tank 8 is deleted by performing an operation in which the amount of demineralized water supplied to the feed water iron injection facility is set to be sufficiently larger than the amount sent by the injection pump 15. In this case, during normal operation, an overflow line 12 is provided in order to exceed the water level in the reaction tank, whereby the operation is performed while constantly discharging the excess water amount. Further, the automatic isolation valve at the facility outlet can be removed by using a pump having a backflow prevention function as the injection pump 15. Further, the agitator 50 is eliminated by increasing the amount of compressed air supplied to the reaction tank 8 to an amount sufficient to stir the liquid in the reaction tank 8.

As shown in FIG. 10, the abnormality monitoring items in this embodiment based on the above equipment configuration and operation are only the thermometer 17 of the CO ₂ injection source water tank and the water leakage detector 34. Further, the circuit of the equipment outlet automatic valve and the stirrer can be omitted.

FIG. 11 is an explanatory diagram of the relational structure between the feed water iron injection facility and the boiling water nuclear power plant described above. Reactor 100, main steam pipe 101, turbine 102, condenser 103, condensate pump 104, condensate purification device (filter 105, demineralizer 106), feed water pipe 61, feed water heater 107, reactor feed water inlet In the water supply pipe 61 of the primary cooling system constituted by the pipe 108, the injection water containing the clad iron is injected from the water supply iron injection facility A of each of the embodiments of the present invention. On the other hand, the Fe / Ni ratio (weight ratio) in the reactor inlet feedwater
Is measured by analyzer B and this ratio is 2 or more (actually about 3)
The injection iron concentration from the injection equipment A is controlled so that This control is usually performed by controlling the current of the electrolytic DC power supply of the electrolytic cell 2 in the facility A. As a result, stable Fe ₂ Ni, which is difficult to elute, as described above in the [Action] section.
Corrosion products are made to adhere and accumulate on the surface of the reactor fuel as a composite oxide of O ₄ and Fe ₂ CoO ₄ .

[Effects of the Invention] The iron injection efficiency can be improved by injecting iron into the reactor water supply in the clad form instead of the ion form. Stabilization of the electrolysis efficiency of the electrolyzer can be achieved by adjusting the temperature of the water supplied to the electrolyzer for producing water containing iron ions to be changed to the clad in the reaction tank. By monitoring and adjusting the water level in the reaction tank, it is possible to prevent the injection of air-mixed water into the reactor water supply, the stable conversion of iron ions from the reactor to the cladding, the stable operation of the electrolytic cell, each tank It is possible to prevent water from leaking. In addition, the operating state of the equipment is monitored, and if an abnormality occurs, the equipment is stopped and the system is isolated to ensure safety. As a result of the above, a reactor feedwater iron injection facility excellent in applicability to an actual plant can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the feed water iron injecting equipment of the present invention when applied to an actual plant, FIG. 2 is a diagram showing a conventional example of an electrolytic iron ion generator, and FIG. Graphs of the test results showing the difference in the injection efficiency between the melt (ion) and the solid (clad), FIG. 4 and FIG. 5 are examples of the feed water iron injection equipment according to the present invention, respectively, equipment monitoring,
Figure showing the control system and means for monitoring the water level,
FIG. 6 is a diagram showing a monitoring / control system relating to the embodiment of FIG. 1, FIG. 7 is a diagram showing another embodiment of the water supply iron injecting equipment of the present invention when applied to an actual plant, FIG. Shows a monitoring / control system of the embodiment, FIG. 9 shows a still another embodiment, FIG. 10 shows a monitoring / control system of the embodiment, and FIG. 11 shows a reactor plant. It is a figure which shows the relationship of the water supply iron injection equipment with respect to. 1 ... CO ₂ injection source water tank, 2 ... Electrolysis tank 8 ... Reaction tank, 9 ... Lower water level gauge 10 ... Intermediate water level gauge, 11 ... Upper water level gauge 12 ... Overflow line 15 ... Injection pump, 16 ... Heating heater 17 ... Temperature 26 ... Automatic inlet valve 27 ... Automatic outlet valve 28 ... Pressure gauge 31 ... Direct current power supply for electrolysis 32 ... Sauce 34 ... Leak detector

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ichiro Kataoka 3-2-1, Saiwaicho, Hitachi, Ibaraki Hitachi Engineering Co., Ltd. (72) Inventor Katsumi Ozumi 3-1-1, Saiwaicho, Hitachi, Ibaraki No. 1 Hitachi Ltd., Hitachi Works (72) Inventor Akira Ichimura 3-10-2 Bentencho, Hitachi City, Ibaraki Hitachi Kyowa Industry Co., Ltd. (72) Toshio Sawa 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Address: Hitachi Research Laboratory, Hiritsu Seisakusho Co., Ltd. (56) Reference JP 61-240196 (JP, A) JP 55-63798 (JP, A) JP 62-233796 (JP, A) Actual development Sho 63-135200 (JP, U)

Claims (8)

[Claims] 1. Iron is injected into the feed water according to the weight concentration of nickel in the feed water so that the weight ratio of iron and nickel in the feed water to the reactor of the boiling water nuclear power plant is controlled to a predetermined value. In an iron injection facility for reactor water supply, the electrolyzer for producing water containing iron ions and the water containing iron ions received from the electrolyzer are temporarily stored and supplied with air or oxygen. Tank for converting iron ions into iron hydroxide or oxide, and means for injecting water containing iron hydroxide or oxide produced in the reactor into the reactor feedwater And a reactor water supply iron injection facility for a boiling water nuclear power plant. 2. The electrolytic cell is an electrolytic cell for producing iron ion-containing water by electrolyzing an iron electrode in contact with water, and means for adjusting the temperature of water supplied to the electrolytic cell is provided. Item 1
Iron supply facility for reactor feedwater of the boiling water nuclear power plant described. 3. A carbon dioxide gas injection source water tank for injecting carbon dioxide gas into the water supplied to the electrolytic cell, and the means for adjusting the temperature has a controllable heater provided in the carbon dioxide gas injection source water tank. The reactor feedwater iron injection facility for a boiling water nuclear power plant according to claim 2. 4. A means for detecting the water level in the reaction tank, and
A means for controlling the amount of water supplied to the electrolytic cell and / or the amount of water injected into the reactor water supply from the reaction vessel so as to keep the detected water level within a predetermined water level or within a predetermined water level range. 1. A reactor water supply iron injection facility for a boiling water nuclear power plant according to 1, 2, or 3. 5. The reaction tank has an overflow line, and the water level in the reaction tank is controlled by the overflow line or by detecting the upper limit water level by the water level detection means in the reaction tank to control the supplied water amount and / or the injected water amount. It adjusts so that it may not exceed an upper limit water level by doing, The reactor water supply iron injection equipment of the boiling water nuclear power plant of Claim 4 characterized by the above-mentioned. 6. The water level in the reaction tank is adjusted so as not to fall below the lower water level by controlling the supplied water amount and / or the injected water amount based on the detection of the lower water level by the water level detection means in the reaction tank. The reactor water supply iron injection facility for a boiling water nuclear power plant according to claim 4 or 5. 7. The arrangement and mutual communication structure of the electrolytic cell and the carbon dioxide gas injection source water tank are arranged such that the upper water level in the electrolytic tank and the upper limit water level in the reaction tank coincide with each other by fluid communication. A reactor feedwater iron injection facility for a boiling water nuclear power plant according to claim 3, 4, 5, or 6. 8. The water temperature in the electrolysis tank, the injection pressure from the reaction tank to the reactor feed water, or the electrolysis voltage in the electrolysis tank exceeds a predetermined allowable upper limit value, and the water level in the reaction tank is a predetermined allowable lower limit value. Temperature, or when water leakage occurs from the reaction tank, electrolysis tank or carbon dioxide gas injection source water tank, the electrolytic tank supply water temperature adjusting means, electrolysis current of the electrolysis tank or from the reaction tank to the reactor water supply is detected. 8. The reactor water supply iron injection equipment for a boiling water nuclear power plant according to claim 1, further comprising means for stopping the injection pump of claim 2, isolating the system of the water supply iron injection equipment, or issuing an alarm.