JP2006038623A - Nuclear power generation plant with boiling water reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nuclear power generation plant with a boiling water reactor including a means which can introduce to the residual heat removal systems the water with its quality that can suppress the quantity of generated corrosion products in the storage of carbon steel pipes composing residual heat removal systems during the normal operation of the reactor. <P>SOLUTION: During the operation of the reactor, pipes in the residual heat removal systems 17 to 25 are stored in a condition where they are filled with suppression pool water. In order to restrain the generation of iron hydroxide from the carbon steel pipes, it is necessary to control the concentration of dissolved oxygen and the conductivity of the stored water. As substitute water systems which can control the conductivity and the concentration of the dissolved oxygen, a device 31 (a nitrogen gas bubbling device) for the deoxidization treatment of the stored water, a device 33 for the desalination treatment of it, a valve 35 for supplying the stored water, and a pump 36, are provided. When the residual heat removal systems are stored with them filled with water during the operation of the reactor, the water in a substitute water storage tank 30 which has undergone at least one of the deoxidization treatment and the desalination treatment is introduced to the residual heat removal systems as the stored water. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for storing a residual heat removal system pipe suitable for suppressing an increase in the dose rate of a residual heat removal system (residual heat removal system) in a boiling water nuclear power plant (BWR), and the residual heat removal system is stopped during BWR operation. It is related with the means which suppresses adhesion of the radionuclide contained in the reactor water to the residual heat removal system piping at the time of a residual heat removal system operation | movement at the time of BWR stop by suppressing generation | occurrence | production of the iron corrosion product in a piping surface inside.

  In BWR, cooling water is forcibly circulated using a recirculation pump or an internal pump in order to efficiently transfer the heat generated in the fuel to the cooling water in the reactor pressure vessel to produce steam. The steam generated in the nuclear reactor is sent to the turbine after removing moisture with a separator and a dryer provided in the upper part of the core. Some steam is extracted as turbine bleed air and used as a heat source for high and low pressure heaters, and most of the other steam is used for power generation and then condensed in a condenser and returned to water.

  The condensate is almost completely degassed in the condenser, and oxygen and hydrogen generated by radiolysis of water in the core are almost completely removed. Condensate is re-supplied to the reactor as feed water.

  At that time, in order to suppress the generation of radioactive corrosion products in the nuclear reactor, in order to mainly remove metal impurities in the condensate, the total amount of the condensate is filtered with an ion exchange resin filtration device such as a desalination treatment device, Next, it heats to near 200 degreeC with a multistage low pressure heater and a high pressure heater.

  On the other hand, the corrosion products are also generated from the water contact parts such as the pressure vessel and recirculation system, and become the source of radioactive corrosion products circulating in the furnace. As a rule, stainless steel and stainless steel such as stellite steel with low corrosion are used.

  The reactor pressure vessel made of low-alloy steel is built up with an inner surface of stainless steel to prevent the low-alloy steel from coming into direct contact with the reactor water. In addition to such material considerations, a portion of the reactor water is purified by a reactor water purification device to positively remove metal impurities that are slightly generated in the reactor water.

  However, in spite of such corrosion control measures by material and water quality control, it is inevitable that very few metal impurities exist in the reactor water, and some metal impurities are boiled in the fuel rods as metal oxides. Adhere to the surface.

  The metal element attached to the surface of the fuel rod undergoes a nuclear reaction upon irradiation with neutrons emitted from the fuel, and generates radionuclides such as cobalt 60, cobalt 58, chromium 51, and manganese 54. These radionuclides are mostly in the form of oxides and remain attached to the fuel rod surface.

  Some of these radionuclides are eluted depending on the solubility of the incorporated oxide or re-released into the reactor water as an insoluble solid called a clad. These radioactive materials are removed by the reactor water purification system.

  The radioactive material that could not be removed accumulates on the surface of the wetted part of the structural material while circulating in the recirculation system together with the reactor water. As a result, radiation is radiated from the surface of the structural material, and radiation exposure occurs to workers during regular inspection work. The dose of work exposure is controlled so that it does not exceed the specified 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 economically as possible. Therefore, various methods for reducing the attachment of radionuclide to the pipe and various methods for reducing the concentration of the radionuclide in the reactor water that serves as a driving force for the attachment of the radionuclide to the pipe have been studied.

  As one of such methods, metal ions such as zinc are allowed to coexist in the reactor water, a dense oxide film containing zinc is formed on the surface of the recirculation piping that contacts the reactor water, and cobalt 60 into the oxide film is formed. , A method for suppressing the uptake of radionuclides such as cobalt 58 has been proposed (see, for example, Patent Document 1).

  There has also been proposed a technique for forming a pre-oxidized film under certain conditions on a recirculation system pipe and a reactor water purification system pipe through which reactor water is passed during operation of the nuclear reactor (see, for example, Patent Document 2).

  However, these technologies do not take into account the residual heat removal system through which reactor water is passed during the reactor shutdown operation, and measures to suppress the attachment of radionuclides in the reactor water extend to the residual heat removal system. It was n’t.

  Therefore, when the residual heat removal system is operated when the reactor is shut down, the residual heat removal system comes into contact with the reactor water containing the radionuclide, so that the radionuclide adheres to the residual heat removal system and becomes an exposure source during the periodic inspection work.

  In particular, an improved boiling water light water reactor without a recirculation system greatly contributes to exposure during periodic inspection work. In addition, since the residual heat removal system is composed of carbon steel piping, even if the oxide containing radioactive nuclides adhered in the past is removed by decontamination, it remains on the surface of the piping during storage of the residual heat removal system during reactor operation. The generated corrosion products promote the reattachment of radionuclides in the reactor water during the operation of the residual heat removal system, and the decontamination effect cannot be maintained.

  Therefore, in order to suppress the formation of corrosion products during storage of the residual heat removal system, after decontamination of the residual heat removal system piping, there is a method of forming an oxide film or chemical conversion film, and a method of adding a rust inhibitor to the stored water. It has been proposed (see, for example, Patent Document 3).

JP-A-58-79196 (pages 2-4, FIGS. 1 to 3) JP-A-62-95498 (pages 3-5, FIGS. 1-5) JP 2002-236191 A (Pages 6-8, FIGS. 1-6) “Anti-corrosion technology”, Vol 28, pp. 32-37 (1979)

  However, in the above prior art, the supply source of water used for storage of the residual heat removal system piping is not particularly considered, and normally, the water in the suppression pool is used for surveillance operation of the residual heat removal system, and the water is used. It is stored in the state retained in the residual heat removal system piping. The water in this suppression pool is not water quality with particular attention paid to the inhibition of carbon steel corrosion.

  An object of the present invention is to provide a boiling water type equipped with means for introducing water of water quality capable of suppressing the amount of corrosion products generated during storage during normal operation of a carbon steel pipe constituting the residual heat removal system into the residual heat removal system. To provide a nuclear power plant.

In order to achieve the above object, the present invention provides
a. Prepare water with low dissolved oxygen concentration and low conductivity b. Utilize water with low dissolved oxygen concentration and low conductivity already used in other BWR systems c. Tanks, valves, etc. that store the quality water to introduce residual water into the residual heat removal system during reactor operation, such as using purified water from the suppression pool. Connect the system consisting of the pump to the residual heat removal system.

  That is, in order to achieve the above object, the present invention includes a storage water deoxygenation processing device, a storage water demineralization processing device, a valve for distributing storage water, and a pump, and a residual heat removal system is provided during operation of the reactor. A boiling water nuclear power plant is proposed in which water that has been subjected to at least one of deoxygenation treatment and desalting treatment is introduced into the residual heat removal system as stored water when it is stored in full water.

  The present invention also includes a circulating water deoxygenation processing device, a circulating water demineralization processing device, and a valve that distributes the circulating water. When the surveillance operation of the residual heat removal system is performed during the reactor operation, the dewatering treatment water is removed. A boiling water nuclear power plant is proposed in which water subjected to at least one of oxygen treatment and desalting treatment is introduced into a residual heat removal system.

  The present invention further proposes a boiling water nuclear power plant equipped with a deoxygenation apparatus for bubbling suppression pool water with nitrogen or an inert gas.

  In order to achieve the above object, the present invention proposes a boiling water nuclear power plant equipped with a desalting apparatus for desalinating suppression pool water.

  The present invention also includes surveillance of a residual heat removal system, which is provided with at least one of replacement water deoxygenation apparatus and replacement water demineralization apparatus, a valve and a pump for distributing replacement water, and is performed during the operation of the reactor. A boiling water nuclear power plant is proposed in which water remaining in the piping of the residual heat removal system is replaced with water subjected to at least one of deoxygenation treatment and desalting treatment immediately after the operation is completed.

  The present invention further proposes a boiling water nuclear power plant equipped with a gas bubbling device for bubbling condensate storage tank water with nitrogen or an inert gas to bring the dissolved oxygen concentration to 0.5 ppm or less.

  In any boiling water nuclear power plant, a high-frequency induction heating device is introduced into the residual heat removal system pipe during construction or periodic inspection of the boiling water nuclear power plant, and the inner surface of the residual heat removal system pipe is set to 400 ° C or higher. An oxide film can be formed by heating.

  Prior to all the above treatments, the corrosion film of the residual heat removal system pipe incorporating the radionuclide may be removed by chemical decontamination.

  Remaining heat removal system piping normally allows reactor water to flow only when the reactor is stopped, compared to recirculation piping and reactor water purification system piping through which reactor water is passed during reactor operation. The BWR plant shutdown operation begins by inserting a control rod to stop the nuclear fuel fission reaction. As a result of this operation, a large amount of steam is generated from 280 ° C. to 150 ° C., so steam is sent from the main steam line to the condenser and the reactor is cooled by the heat of vaporization of the generated steam.

  At a temperature of 150 ° C. or lower, the cooling efficiency due to the heat of vaporization decreases, so the reactor water is cooled by the residual heat removal system branched from the reactor water recirculation system. The cooled reactor water passes through the reactor recirculation system or returns directly to the reactor. At a temperature of 100 ° C. or lower, cooling by the heat of vaporization cannot be performed, so cooling in the residual heat removal system is the main.

  Since the residual heat removal system needs to have a spare system, it has two or more systems. Therefore, the plant stop operation is alternately performed at each stop. Further, the flow rate of water passing through the residual heat removal system heat exchanger and the bypass line flow rate of the heat exchanger are controlled to adjust the speed of cooling the reactor water. In the recirculation system piping and the reactor water purification system piping, radioactive ions in the reactor water are taken into the oxide film as the oxide film grows due to corrosion, and radionuclides accumulate.

  However, in the residual heat removal system, the reactor water temperature at the start of operation is as low as 150 ° C or lower, and the reactor water temperature decreases at the start of operation. Since it is as short as several hours, the contribution of the above process is small. The inventors have studied in detail the accumulation mechanism of radionuclides in the residual heat removal system piping, and as shown below, adhesion of radioactive ions occurs in a process different from the recirculation system piping and the reactor water purification system piping. I understood that.

  In carbon steel piping used in the residual heat removal system, as seen in the reactor water purification system piping, in high-temperature water, ions such as nickel contained in the reactor water were taken in addition to hematite and magnetite. Produces ferrite.

  However, in low temperature water at 100 ° C. or lower where the piping of the residual heat removal system is exposed during the reactor operation, iron hydroxide becomes the main corrosion product. Iron hydroxide produced under these conditions has a property of adsorbing various ions in water with a large surface area in an algal form. For this reason, when the reactor shutdown operation is performed and the operation of the residual heat removal system is started, the adsorption of radioactive ions in the reactor water occurs. The concentration of radioactive ions in the reactor water shows a behavior in which it rises immediately after the reactor shutdown operation and then decreases.

  At the start of residual heat removal system operation, the reactor water radioactivity concentration has already decreased as the temperature decreases, so the radioactive ions adsorbed on the iron hydroxide at the start of operation can also be simply absorbed. Since it is released as the active concentration decreases, exposure due to the accumulation of radionuclides in the residual heat removal system is not a problem.

  However, in iron hydroxide, dehydration reaction is caused by a reaction such as Chemical Formula 1 or Chemical Formula 2 at a temperature of about 100 ° C. or higher, resulting in hematite or magnetite. At this time, if nickel, cobalt, and their radioactive ions are adsorbed in the dehydration region, ferrite containing these nickel and cobalt is generated as shown in Chemical Formula 3 and Chemical Formula 4, and it is difficult to desorb.

  FIG. 9 is a diagram schematically showing the process of attaching radioactive ions to the residual heat removal system piping. The adsorption region of radioactive cobalt ions and the dehydration region at a temperature of 100 ° C. or more are generated in the iron hydroxide formed on the carbon steel pipe of the residual heat removal system, and cobalt ferrite is generated in the region where these two layers overlap, Accumulation occurs.

したがって、余熱除去系統配管への放射性イオンの蓄積を防止するには、原子炉運転中に余熱除去系統配管表面で生じる水酸化鉄の発生を抑制すればよい。原子炉運転中に余熱除去系統が運用されるのは、月に１回程度の頻度で行われるサーベイランス運転の時のみで、サーベイランス運転終了後に余熱除去系統は停止され、そのままの状態で満水保管される。

Therefore, in order to prevent accumulation of radioactive ions in the residual heat removal system piping, generation of iron hydroxide generated on the surface of the residual heat removal system piping during the operation of the reactor may be suppressed. The residual heat removal system is operated only during the surveillance operation that is performed once a month during the operation of the nuclear reactor. After the surveillance operation is completed, the residual heat removal system is stopped and stored as it is. The

  Since the water of the suppression pool is used for the surveillance operation, the residual heat removal system is in a state of being fully stored with the water of the suppression pool. The water quality of this suppression pool is not the water quality that paid special attention to the corrosion inhibition of carbon steel. It is known that lowering the dissolved oxygen concentration and lowering the conductivity are effective for inhibiting the corrosion of carbon steel in still water.

  FIG. 10 is a diagram showing the dependence of dissolved oxygen concentration on the corrosion rate of carbon steel in still water at room temperature shown in Non-Patent Document 1, and FIG. 11 shows the carbon steel shown in Non-Patent Document 1. It is a figure which shows the influence of the electrical conductivity which has on the corrosion rate of.

  It can be seen that the lower the both, the lower the corrosion rate. Therefore, in order to suppress the generation of iron hydroxide generated on the surface of the residual heat removal system piping, a method of storing the residual heat removal system with water having a low dissolved oxygen concentration and low conductivity can be considered.

  FIG. 12 is a diagram showing the results of comparison of the accumulated amount of radioactive cobalt ions by the inventors for each carbon steel immersion environment. Carbon steel specimens are immersed in water that simulates the quality of the water in the suppression pool, water that simulates the quality of the outlet water of the condensate purification system, and water that simulates the quality of the condensate makeup water system, and then radioactive. It was attached to a hot water loop that could use cobalt ions. The high-temperature water loop was operated so as to follow a temperature history simulating the residual heat removal system when the reactor was shut down, and when the temperature dropped, the test piece was taken out and the amount of accumulated radioactive cobalt was compared.

  From FIG. 12, the effect of suppressing the accumulation of radioactive cobalt ions could not be obtained with dissolved oxygen concentration and conductivity water quality comparable to the condensate makeup water system.

  On the other hand, it was found that the concentration of radioactive cobalt ions, which is about half the amount, can be obtained with water having a dissolved oxygen concentration and conductivity that are about the outlet water of the condensate purification system.

  In the boiling water nuclear power plant of the present invention, the dissolved oxygen concentration is used as storage water for the residual heat removal system during operation of the reactor. Since water with low conductivity is used, the amount of iron hydroxide generated in the carbon steel piping of the residual heat removal system during storage is reduced, and the reactor water containing radioactivity is retained by the reactor shutdown operation. When it flows into the removal system, it is possible to suppress the adhesion of the radioactivity to the residual heat removal system piping.

  At least one of dissolved oxygen concentration and conductivity on the side of the residual heat removal system at the junction point from the recirculation system or reactor water purification system to the residual heat removal system and the junction point from the residual heat removal system to the recirculation system or reactor water purification system A replacement water injection port is provided for injecting water with reduced water, and a tank, a pump, and a valve for storing replacement water are connected to the injection port by piping.

  In the middle of the residual heat removal system, for example, near the upstream of the heat exchanger, a branch for leading the water to be replaced to the waste treatment system is provided, and a detector for measuring drainage conductivity and dissolved oxygen concentration is provided at the branch point. .

  FIG. 1 is a diagram showing a system configuration of Embodiment 1 of a boiling water nuclear power plant according to the present invention.

  During normal operation of the reactor, the cooling water in the reactor pressure vessel 1 is circulated through the recirculation system 3 by the recirculation pump 2. The steam generated in the reactor pressure vessel 1 is guided to the turbine 5 by the main steam system 4, and after working in the turbine 5, is returned to water by the condenser 6.

  In order to remove impurities contained in the condensate, the entire amount of the condensate is purified by being passed through the condensate purification device 8 by the condensate pump 7 and used as water supply. The feed water is passed through the low-pressure feed water heater 10 and the high-pressure feed water heater 11 by the feed water pump 9 and supplied into the reactor pressure vessel 1 through the feed water system 12.

  A part of the feed water purified by the condensate purification device 8 is supplied to the control rod drive system through the control rod drive water pump 15 and the control rod drive water purification device 16 and used to insert the control rod into the reactor core.

  The temperature of the core at the time of shutdown is initially lowered by the heat of evaporation of the reactor water. When the temperature of the reactor water reaches about 150 ° C., the cooling efficiency decreases, so the residual heat removal system 17 is used. Residual heat removal system inlet valve 18, residual heat removal system heat exchanger inlet valve 19, residual heat removal system heat exchanger outlet valve 20, residual heat removal system return valve 21 outside the reactor containment vessel, residual heat removal system return valve 22 inside the reactor containment vessel Is opened, the residual heat removal system pump 23 is started, the reactor water is supplied to the residual heat removal system heat exchanger 24 and further cooled, and the reactor is stopped.

  At that time, the opening / closing amounts of the residual heat removal system heat exchanger bypass valve 25 and the residual heat removal system heat exchanger inlet valve 19 are adjusted to adjust the inflow amount of the reactor water to the residual heat removal system heat exchanger 24, and the reactor water temperature Adjust the descent rate. On the other hand, the residual heat removal system during normal operation of the reactor is in a stopped state.

  Surveillance operation is performed using the water in the suppression pool 27 in the reactor containment vessel 26 at a frequency of about once a month. Surveillance operation is an operation in which the suppression pool outlet valve 28 and the suppression pool return valve 29 are opened, a residual heat removal system pump 23 is used to form a closed loop that passes through the suppression pool 27, and the water in the pool is circulated.

  After the surveillance operation, the residual heat removal system is stored as it is, and the water of the suppression pool 27 is fully stored in the piping of the residual heat removal system. This water is replaced with replacement water with low dissolved oxygen concentration and low conductivity. Replacement water is prepared in the replacement water storage tank 30 in advance.

  The water in the replacement water storage tank 30 is reduced in dissolved oxygen concentration by the nitrogen gas bubbling device 31 and is passed through the replacement water desalination processing device 33 by the replacement water circulation pump 32 to remove impurities and lower the conductivity. Keep it. The water quality of the replacement water is, for example, a conductivity of 0.3 μS / cm or less and a dissolved oxygen concentration of 0.5 ppm or less.

  After the surveillance operation, the residual heat removal system inlet valve 18, the residual heat removal system return valve 21 outside the reactor containment vessel, and the residual heat removal system return valve 22 inside the reactor containment vessel are kept closed, and the suppression pool outlet valve 28, The suppression pool return valve 29 and the residual heat removal system heat exchanger bypass valve 25 are closed, the residual heat removal system heat exchanger inlet valve 19, the residual heat removal system heat exchanger outlet valve 20, the waste treatment system valve 34, and the replacement water supply valve. 35 and the replacement water feed pump 36 replaces the water remaining in the pipe with the replacement water in the replacement water storage tank 30.

  Next, the residual heat removal system heat exchanger inlet valve 19 and the residual heat removal system heat exchanger outlet valve 20 are closed, the residual heat removal system heat exchanger bypass valve 25 is opened, and residual water remaining in the bypass line is replaced with replacement water. Rinse with.

  Subsequently, the residual heat removal system heat exchanger bypass valve 25 is closed and the residual heat removal system return valve 21 outside the reactor containment vessel is opened, and the remaining heat removal system return valve 21 outside the reactor containment vessel to the waste treatment system valve 34 is opened. Residual water remaining in the residual heat removal system piping is washed away with replacement water.

  By these operations, the residual water containing dissolved oxygen and impurities and remaining in the residual heat removal system piping can be replaced with clean replacement water in which dissolved oxygen and impurities are reduced.

  FIG. 2 is a diagram showing a system configuration of Embodiment 2 of the boiling water nuclear power plant according to the present invention.

  In the second embodiment, in addition to the first embodiment, a conductivity meter 37 and a dissolved oxygen concentration meter 38 are provided at the entrance of the waste treatment system. Each data measured by the conductivity meter 37 and the dissolved oxygen concentration meter 38 is collected in the information processing control device 39 by the signal processing cable 40.

  In the information processing control device 39, the residual heat removal system heat exchanger inlet valve 19, the residual heat removal system heat exchanger outlet valve 20, the residual heat removal system return valve 21 outside the reactor containment vessel, the residual heat removal via the valve control signal processing cable 41. The system heat exchanger bypass valve 25, the waste treatment system valve 34 and the replacement water feed valve 35 are controlled to be opened and closed and the replacement water feed pump 36 is started and stopped.

  After the surveillance operation is completed, after the suppression pool outlet valve 28 and the suppression pool return valve 29 are closed, the control operation of replacing the residual water in the residual heat removal system piping with the replacement water using the information processing control device 39 is started.

  First, the residual heat removal system outside return valve 21 and the residual heat removal system heat exchanger bypass valve 25 are closed, the residual heat removal system heat exchanger inlet valve 19, the residual heat removal system heat exchanger outlet valve 20, and the waste treatment. The system valve 34 and the replacement water supply valve 35 are opened, and the replacement water supply pump 36 is controlled to start.

  As a result, when the residual water in the corresponding residual heat removal system pipe is replaced with the replacement water, the values of the conductivity meter 37 and the dissolved oxygen concentration meter 38 are reduced to the same level as the replacement water. As such values, for example, the conductivity is 0.3 μS / cm, and the dissolved oxygen concentration is 0.5 ppm.

  In the information processing control device 39 that detects this, the residual heat removal system heat exchanger inlet valve 19 and the residual heat removal system heat exchanger outlet valve 20 are then closed, the residual heat removal system heat exchanger bypass valve 25 is opened, and the bypass is bypassed. Each valve is controlled so that residual water remaining in the line is washed away with replacement water.

  When the residual water in the bypass line is swept away, the values of the conductivity meter 37 and the dissolved oxygen concentration meter 38 once rise, and then when the residual water is completely swept away, it drops to the same level as the replacement water.

  In the information processing control device 39 that has detected this, next, the residual heat removal system heat exchanger bypass valve 25 is closed, the residual heat removal system outside the reactor containment vessel is opened, and the residual heat removal system outside the reactor containment vessel is returned. Residual water remaining in the residual heat removal system piping from the valve 21 to the waste treatment system valve 34 is washed away with replacement water.

  At this time, if the residual water in the residual heat removal system pipe is washed away, the values of the conductivity meter 37 and the dissolved oxygen concentration meter 38 once rise, and then the residual water is completely washed away, it is equivalent to the replacement water. Decrease to level.

  By such control, the residual water in the residual heat removal system piping is automatically replaced with replacement water having low conductivity and low dissolved oxygen concentration.

  FIG. 3 is a diagram showing a system configuration of Embodiment 3 of the boiling water nuclear power plant according to the present invention.

  In the third embodiment, the outlet water of the condensate purification device 8 is used as the replacement water instead of the replacement water of the first embodiment. Since the outlet water of the condensate purification device 8 is degassed by the condenser 6 and becomes a low dissolved oxygen concentration, the condensate is purified by the condensate purification device 8 and has low conductivity. It can be used as the residual heat removal system piping replacement water of the invention.

  In the third embodiment, the piping is branched from the outlet of the condensate purification device 8, and the replacement water feed pump 36 and the replacement water are replaced with the condensate degassed by the condenser 6 and purified by the condensate purification device 8. The residual heat removal system is supplied through the water supply valve 35.

  In the fourth embodiment, condensate replenishment system water (P) is used instead of the outlet water of the condensate purification apparatus 8 used in the third embodiment. The dissolved oxygen concentration and conductivity of the condensate replenishment system water (P) are 0.5 ppm or less and 0.3 μS / cm or less, and can be used as replacement water for the residual heat removal system piping of the present invention.

  In the fifth embodiment, the water in the suppression pool 27 is not used in the surveillance operation of the residual heat removal system, but the water in the replacement water storage tank 30 shown in FIG. 1 is used.

  The suppression pool outlet valve 28 is closed, the suppression pool return valve 29 is opened, and the replacement water supply valve 35 is further opened so that the replacement water can be supplied to the residual heat removal system.

  Next, the surplus heat removal system pump 23 and the replacement water feed pump 36 are activated to perform a surveillance operation using the replacement water. The replacement water supplied to the residual heat removal system reaches the suppression pool 27 by causing residual water in the residual heat removal system piping to flow into the suppression pool 27. As a result, the residual heat removal system piping is replaced with replacement water having low conductivity and low dissolved oxygen concentration.

  In the sixth embodiment, the water in the suppression pool 27 is not used in the surveillance operation, but the outlet water of the condensate purification apparatus 8 is used as a system configuration as shown in FIG. The suppression pool outlet valve 28 is closed, the suppression pool return valve 29 is opened, and the replacement water feed valve 35 is further opened so that the outlet water of the condensate purification apparatus 8 can be supplied to the residual heat removal system.

  Next, surveillance operation using the outlet water of the condensate purification apparatus 8 is performed by activating the residual heat removal system pump 23 and the replacement water feed pump 36. The outlet water of the condensate purification system supplied to the residual heat removal system reaches the suppression pool 27 by causing residual water in the residual heat removal system piping to flow into the suppression pool 27. As a result, the inside of the residual heat removal system pipe is replaced with the outlet water of the condensate purification device 8 having a low conductivity and a low dissolved oxygen concentration.

  FIG. 4 is a diagram showing a deoxygenation and desalination treatment method for suppression pool water. In Example 7, the suppression pool water is deoxygenated and desalted, and this suppression pool water is used for surveillance operation.

  A nitrogen gas bubbling device 31 is connected to the suppression pool 27 so that the dissolved oxygen concentration of the suppression pool water is 0.5 ppm or less. A suppression pool water purification pump 42 and a suppression pool water desalting apparatus 43 are attached to the suppression pool 27 so that the conductivity of the suppression pool water is 0.3 μS / cm or less.

  When surveillance operation of the residual heat removal system is performed using the suppression pool water deoxygenated and desalted in this way, residual water in the residual heat removal system piping can be replaced with deoxygenated and desalted suppression pool water. .

  FIG. 5 is a diagram showing a system configuration of Example 8 of the boiling water nuclear power plant according to the present invention.

  In Example 8, the nitrogen gas bubbling device 31 is used to deoxygenate the condensate storage tank water in the condensate storage tank 13, and this is used as replacement water for the residual heat removal system piping.

  The condensate storage tank 13 is laid with piping connected to the residual heat removal system, and the residual heat removal system uses the condensate storage tank water deoxidized by the replacement water supply valve 35 and the replacement water supply pump 36 as replacement water. You can send water.

  In this way, after the surveillance operation is completed, if the valve and the pump are operated in the same manner as in Example 1, the residual water remaining in the residual heat removal system can be replaced with deoxygenated condensate storage tank water. it can.

  In the ninth embodiment, the water in the suppression pool 27 is not used at the time of surveillance operation, but condensate storage tank water that has been deoxygenated as a system configuration as shown in FIG. 5 is used.

  The suppression pool outlet valve 28 is closed, the suppression pool return valve 29 is opened, and the replacement water feed valve 35 is further opened so that the deoxygenated condensate storage tank water can be supplied to the residual heat removal system.

  Next, surveillance operation is performed using the condensate storage tank water that has been deoxygenated by activating the residual heat removal system pump 23 and the replacement water feed pump 36.

  The deoxygenated condensate storage tank water supplied to the residual heat removal system reaches the suppression pool 27 by causing residual water in the residual heat removal system piping to flow into the suppression pool 27. As a result, the residual heat removal system piping is replaced with condensate storage tank water having low conductivity and low dissolved oxygen concentration.

  FIG. 6 is a diagram showing a system configuration of Example 10 of the boiling water nuclear power plant according to the present invention.

  In Example 10, after the surveillance operation is completed, the residual water in the residual heat removal system piping is replaced with the outlet water of the reactor water purification system. The piping system is branched from the reactor water purification system and connected to the residual heat removal system so that the outlet water of the reactor water purification device 47 can be introduced into the residual heat removal system.

  The reactor water purification system is branched from the inlet portion of the recirculation pump 2, and the reactor water taken out from the reactor water purification system is recirculated by the reactor water purification system pump 44, the reactor water purification system regenerative heat exchanger 45, and the reactor water purification system non-reactor. After being sent to the regenerative heat exchanger 46 and the temperature being lowered, impurities are removed in the reactor water purification device 47.

  The outlet water of the reactor water purification device 47 from which impurities have been removed is preheated through the reactor water purification system regenerative heat exchanger 45 and then merged with the feed water. In the reactor water purification device 47, since ion components are also removed, the conductivity of the outlet water of the reactor water purification device 47 is lower than 0.3 μS / cm, and the dissolved oxygen concentration in the reactor water during plant operation is low. Since the NWC condition is about 200 ppb, the dissolved oxygen concentration is 0.5 ppm or less, which is suitable for the storage water of the residual heat removal system piping.

  In addition, since the reactor water purification system is always in operation while the plant is operating, if the piping system is configured as shown in FIG. 6, it can be used at the end of the surveillance operation.

  After the surveillance operation, the residual heat removal system inlet valve 18, the residual heat removal system return valve 21 outside the reactor containment vessel, and the residual heat removal system return valve 22 inside the reactor containment vessel are kept closed, and the suppression pool outlet valve 28, The suppression pool return valve 29 and the residual heat removal system heat exchanger bypass valve 25 are closed, the residual heat removal system heat exchanger inlet valve 19, the residual heat removal system heat exchanger outlet valve 20, the waste treatment system valve 34, and the replacement water supply water. The valve 35 is opened, and the water remaining in the pipe is replaced with the outlet water of the reactor water purification device 47 by the replacement water feed pump 36.

  Next, the residual heat removal system heat exchanger inlet valve 19 and the residual heat removal system heat exchanger outlet valve 20 are closed, the residual heat removal system heat exchanger bypass valve 25 is opened, and the residual water remaining in the bypass line is supplied to the reactor water. Rinse with the outlet water of the purification device 47.

  Subsequently, the residual heat removal system heat exchanger bypass valve 25 is closed, the residual heat removal system outside the reactor containment vessel is opened, and the residual heat from the residual heat removal system outside the reactor containment vessel 21 to the waste processing system valve 34 is opened. Residual water remaining in the removal system piping is washed away with the outlet water of the reactor water purification device 47.

  By these operations, the residual water containing dissolved oxygen and impurities and remaining in the residual heat removal system piping can be replaced with clean outlet water of the reactor water purification apparatus 47 in which dissolved oxygen and impurities are reduced. If the reflux water from the reactor water purification system to the feed water is used as the replacement water of the residual heat removal system, the feed water flow rate is reduced, and therefore the shortage is replenished from the condensate storage tank 13 using the condensate supply pump 14.

  In the eleventh embodiment, the water in the suppression pool 27 is not used in the surveillance operation, but a pipe is branched from the reactor water purification system as shown in FIG.

  The suppression pool outlet valve 28 is closed, the suppression pool return valve 29 is opened, the replacement water feed valve 35 is opened, and the outlet water of the reactor water purification device 47 is ready to be supplied to the residual heat removal system.

  Next, the residual heat removal system pump 23 and the replacement water feed pump 36 are activated, and a surveillance operation is performed using the outlet water of the reactor water purification device 47.

  The outlet water of the reactor water purification system supplied to the residual heat removal system pushes residual water in the residual heat removal system piping into the suppression pool 27 and reaches the suppression pool 27. As a result, the residual heat removal system piping is replaced with the outlet water of the reactor water purification device 47 having a low conductivity and a low dissolved oxygen concentration.

  When the reflux water from the reactor water purification system to the feed water is used for surveillance operation of the residual heat removal system, the flow rate of the feed water is reduced, and the condensate supply tank 14 is used to replenish the shortage.

  FIG. 7 shows an underwater simulating the quality of suppression pool water by preparing a test piece of carbon steel whose surface was polished with water-resistant abrasive paper and a test piece having an oxide film formed on the surface using a high frequency induction heater. FIG. 7 is a view showing a result of comparing the amount of radioactive cobalt deposited after storing two types of test pieces and performing a radioactive cobalt adhesion test similar to the experiment of FIG. 6.

  Magnetite-based oxide film formed on the surface of a carbon steel specimen by high-frequency induction heating suppresses the formation of iron hydroxide due to corrosion during storage, and suppresses cobalt adhesion during high-temperature water flow. .

  FIG. 8 is a diagram showing a processing method of Example 12 in which this principle is applied to an actual residual heat removal system piping.

  During periodic inspection work, the spiral coil 48 for high-frequency induction heating is inserted into the pipe from the opening through inspection work such as valves of the residual heat removal system, and swept while rotating to form an oxide film by high-frequency induction heating on the inner surface of the pipe. .

  When the periodic inspection is completed and the plant is operated, the suppression pool water flows into the residual heat removal system piping and is in a state of full storage. At this time, even if the quality of the suppression pool water is poor, an oxide film mainly composed of magnetite by high-frequency induction heating is formed in this residual heat removal system piping, so that it is difficult for a new corrosion film to be generated. Yes.

  Therefore, even when high temperature water containing radioactivity flows into the residual heat removal system at the time of the next plant shutdown, the formation of a corrosion film that takes in radioactive cobalt is suppressed, so that the adhesion of radioactive cobalt is suppressed.

  In Example 13, after removing the corrosion film of the residual heat removal system pipe that has taken in the radionuclide by chemical decontamination, the radiocobalt adhesion suppressing method according to any one of Examples 1 to 12 is applied. In the existing BWR, the radionuclide is already taken in the corrosion coating formed in the water contact portion of the residual heat removal system piping. When this radionuclide is removed and the radiocobalt adhesion suppression method according to any of Examples 1 to 12 is applied, contribution to periodic inspection work exposure from the radionuclide already present in the residual heat removal system piping is achieved. Disappear. As a result, the radioactive cobalt adhesion suppression effect obtained in Examples 1 to 12 appears as it is as a work exposure reduction effect.

  According to each of the above embodiments, since water having a low dissolved oxygen concentration and / or conductivity is used as storage water for the residual heat removal system during reactor operation, corrosion during storage is suppressed, and the residual heat removal system Reduces the amount of iron hydroxide produced in carbon steel piping, and adsorbs and adheres to the iron hydroxide remaining on the piping surface when reactor water containing radioactivity flows into the residual heat removal system by shutting down the reactor The amount of radioactivity generated can be suppressed, and the exposure during regular inspection work can be reduced.

It is a figure which shows the system | strain structure of Example 1 of the boiling water nuclear power plant by this invention. It is a figure which shows the system | strain structure of Example 2 of the boiling water nuclear power plant by this invention. It is a figure which shows the system | strain structure of Example 3 of the boiling water nuclear power plant by this invention. It is a figure which shows the deoxygenation and desalination processing method of the suppression pool water in Example 3 of the boiling water nuclear power plant by this invention. It is a figure which shows the system | strain structure of Example 8 of the boiling water nuclear power plant by this invention. It is a figure which shows the system | strain structure of Example 10 of the boiling water nuclear power plant by this invention. It is a figure which shows the surface treatment dependence which acts on the cobalt 58 adhesion amount in experiment by inventors. It is a figure which shows the processing method of Example 12 which applied the high frequency induction heating to the residual heat removal system piping of an actual machine. It is a figure which shows typically the radioactive ion attachment process to the residual heat removal system piping. It is a figure which shows the dissolved oxygen concentration dependence which acts on the corrosion rate of the carbon steel in room temperature still water. It is a figure which shows the influence of the electrical conductivity which acts on the corrosion rate of carbon steel. It is a figure which shows the result of inventors comparing the accumulation amount of radioactive cobalt 58 ion for every carbon steel immersion environment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reactor pressure vessel 2 Recirculation pump 3 Recirculation system 4 Main steam system 5 Turbine 6 Condenser 7 Condensate pump 8 Condensate purification device 9 Feed water pump 10 Low pressure feed water heater 11 High pressure feed water heater 12 Feed water system 13 Water storage tank 14 Condensate supply pump 15 Control rod drive water pump 16 Control rod drive water purification device 17 Residual heat removal system 18 Residual heat removal system inlet valve 19 Residual heat removal system heat exchanger inlet valve 20 Residual heat removal system heat exchanger outlet valve 21 Residual heat removal system return valve outside reactor containment 22 Remaining heat removal system return valve inside reactor containment 23 Residual heat removal system pump 24 Residual heat removal system heat exchanger 25 Residual heat removal system heat exchanger bypass valve 26 Reactor containment vessel 27 Suppression pool 28 Suppression pool outlet valve 29 Suppression pool return valve 30 Replacement water storage tank 31 Nitrogen gas bubbling device 32 Replacement water circulation pump 33 Replacement water desalination device 34 Waste treatment system valve 35 Replacement water feed valve 36 Replacement water feed pump 37 Conductivity meter 38 Dissolved oxygen concentration meter 39 Information processing control device 40 Signal Processing cable 41 Valve control signal processing cable 42 Suppression pool water purification pump 43 Suppression pool water demineralizer 44 Reactor water purification system pump 45 Reactor water purification system regenerative heat exchanger 46 Reactor water purification system non-regenerative heat exchanger 47 Furnace Water purification device 48 High frequency induction heating spiral coil

Claims (20)

Equipped with storage water deoxygenation equipment, storage water demineralization equipment, valves for distributing storage water, pumps,
Boiling water nuclear power characterized by introducing water that has undergone at least one of deoxygenation treatment and desalination treatment into the residual heat removal system as stored water when the residual heat removal system is stored in full water during the operation of the reactor Power plant. In the boiling water nuclear power plant according to claim 1,
A boiling water nuclear power plant characterized in that water from at least one of condensate purification system outlet water and condensate makeup water is used as storage water to be introduced into the residual heat removal system as storage water for the residual heat removal system. In the boiling water nuclear power plant according to claim 1,
A boiling water nuclear power plant characterized by using water with a dissolved oxygen concentration of 0.5 ppm or less and conductivity of 0.3 μS / cm or less as storage water for the residual heat removal system. It is equipped with a deoxygenator for circulating water, a desalinator for circulating water, and a valve for distributing the circulating water.
A boiling water nuclear power plant characterized by introducing water subjected to at least one of deoxygenation treatment and desalting treatment as circulating water to the residual heat removal system when performing surveillance operation of the residual heat removal system during the operation of the nuclear reactor. . In the boiling water nuclear power plant according to claim 4,
A boiling water nuclear power plant characterized in that water from at least one of condensate purification system outlet water and condensate makeup water is used as circulating water to be introduced into the residual heat removal system as circulation water in the residual heat removal system. In the boiling water nuclear power plant according to claim 4,
A boiling water nuclear power plant characterized by using water with a dissolved oxygen concentration of 0.5 ppm or less and conductivity of 0.3 μS / cm or less as circulating water for the residual heat removal system. In the boiling water nuclear power plant according to claim 4,
Before the surveillance operation of the residual heat removal system is completed, water that has been subjected to at least one of deoxygenation treatment and desalting treatment as circulating water is introduced into the residual heat removal system, and at least a part of the residual heat removal system is filled with the corresponding circulating water. After that, the boiling water nuclear power plant is characterized by terminating the surveillance operation. A boiling water nuclear power plant comprising a deoxygenation treatment device for bubbling suppression pool water with nitrogen or an inert gas. The boiling water nuclear power plant according to claim 8,
A boiling water nuclear power plant comprising means for controlling the dissolved oxygen concentration of suppression pool water to 0.5 ppm or less by bubbling of an inert gas. A boiling water nuclear power plant comprising a desalination apparatus for desalinating suppression pool water. The boiling water nuclear power plant according to claim 10,
A boiling water nuclear power plant comprising a desalination treatment device for suppressing the conductivity of suppression pool water to 0.3 μS / cm or less. Comprising at least one of replacement water deoxygenation apparatus and replacement water demineralization apparatus, a valve and a pump for distributing replacement water,
Immediately after the end of surveillance operation of the residual heat removal system performed during the reactor operation, water remaining in the piping of the residual heat removal system is replaced with water subjected to at least one of deoxygenation treatment and desalination treatment. Boiling water nuclear power plant. The boiling water nuclear power plant according to claim 12,
A boiling water nuclear power plant comprising a pipe and a valve for discharging water to be replaced into a radioactive waste treatment system. In the boiling water nuclear power plant according to claim 12 or 13,
A boiling water nuclear power plant characterized in that at least one of a conductivity meter and a dissolved oxygen meter is installed in a piping system connected from a residual heat removal system to a waste treatment system. The boiling water nuclear power plant according to any one of claims 12 to 14,
A data collection device for collecting conductivity meter or dissolved oxygen meter data, an information processing control device for determining the end of replacement from the water to be replaced to the replacement water based on the collected data, a pump and A boiling water nuclear power plant comprising a control device for operating a valve. The boiling water nuclear power plant according to claim 15,
Boiling water nuclear power generation characterized in that it has an information processing control device that judges that replacement is completed when at least one of the conditions of electric conductivity of 0.3 μS / cm or less and dissolved oxygen concentration of 0.5 ppm or less is achieved. plant. The boiling water nuclear power plant according to any one of claims 12 to 15,
A boiling water nuclear power plant characterized in that at least one of condensate purification system outlet water and condensate makeup water system water is used as the replacement water. A boiling water nuclear power plant comprising a gas bubbling device for bubbling condensate storage tank water with nitrogen or an inert gas so that a dissolved oxygen concentration is 0.5 ppm or less. The boiling water nuclear power plant according to any one of claims 1 to 18,
A high-frequency induction heating device is introduced into the residual heat removal system pipe during construction or periodic inspection of the boiling water nuclear power plant, and the oxide film is formed by heating the inner surface of the residual heat removal system pipe to 400 ° C or higher. Boiling water nuclear power plant. The boiling water nuclear power plant according to any one of claims 1 to 18,
Prior to all the treatments, the boiling water nuclear power plant is characterized by removing the corrosion film of the residual heat removal system pipe incorporating the radionuclide by chemical decontamination.

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