JPH068918B2 - Boiling water nuclear power plant - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a condensate of a boiling water reactor (hereinafter referred to as BWR).
The present invention relates to a boiling water nuclear power plant for removing carbon dioxide (CO ₂ ) from a water supply system to reduce an ion load on an ion exchange resin of a condensate demineralizer.

[Technical Background of the Invention] A BWR generally has the following configuration. A reactor pressure vessel is installed in the reactor containment vessel supported by a pedestal for the reactor pressure vessel, and a coolant and a reactor core are housed in the reactor pressure vessel. The coolant flows upward in the core, at which time the temperature rises due to the nuclear reaction heat of the core. The heated coolant becomes a two-phase flow state of water and steam,
It is introduced into a steam separator installed above the core. The water is separated in this water separator, the separated steam is introduced into the steam dryer installed above the water separator,
Dried to dry steam. This dry steam is transferred to the turbine system through the main steam pipe connected to the reactor pressure vessel and used for power generation. The steam that has worked in the turbine system is introduced into the condenser and condensed and liquefied to become condensed water.
This condensate is collected in the hot well of the condenser. Condensate is then introduced into the condensate filter to remove insoluble corrosion products and into the condensate desalination unit. Ionic impurities are removed in this condensate demineralizer, and then heated and returned to the reactor pressure vessel via the water supply system.

The condensate demineralizer is filled with an ion exchange resin, and the ion exchange resin adsorbs ionic impurities in the condensate. At that time, when a certain amount or more of ionic impurities are adsorbed, it is necessary to regenerate the ion exchange resin.
Regeneration of such ion exchange resin is performed by chemicals.
The chemical used to regenerate the ion exchange resin is transferred to the waste treatment system together with the removed ionic impurities. The above chemicals include sulfuric acid (H ₂ SO ₄ ) and caustic soda (Na
OH) is used, and when these chemicals are used, it becomes sodium sulfate (Glauber's salt Na ₂ SO ₄ ) when treated as waste in the waste treatment system. Generally, in a waste treatment system, the volume of waste is reduced as much as possible, but it has been difficult to reduce the amount of sodium sulfate. Therefore, a method that does not use such a chemical, in other words, a method that does not require regeneration of the ion exchange resin has been considered.

As one of the methods, there is a method in which the ion exchange resin is used for a certain period of time without being regenerated and then discarded. Since the ion exchange resin is not regenerated, the above-mentioned chemicals are not used. This method is particularly effective when the ion load from the upstream of the condensate desalination unit is small.

[Problems of Background Art] According to the above configuration, there are the following problems. That is, in a recent plant, considering only the ion load during normal operation, the ion exchange resin can be continuously used for 4 to 5 years without being regenerated. However, immediately after the construction of the plant or immediately after the periodic inspection, the ion load at the start of the plant becomes large. The reason why the ion load becomes high immediately after the plant is constructed or immediately after the periodic inspection is that carbon dioxide gas flows into the reactor water when the plant is opened to the atmosphere. Therefore, it has been required to remove this carbon dioxide gas to reduce the ion load at the time of plant startup.

[Object of the Invention] The present invention has been made based on the above points, and an object of the present invention is to effectively remove carbon dioxide gas in a plant and to start the plant immediately after the plant construction or immediately after the periodic inspection. It is to provide a boiling water nuclear power plant capable of reducing the ion load of the ion exchange resin of the condensate demineralizer.

[Summary of the Invention] That is, in the boiling water nuclear power plant according to the first invention, the steam generated in the reactor pressure vessel is introduced into a turbine for power generation, and the steam that has performed work is introduced into a condenser. In the boiling water nuclear power plant, the condensed water is condensed and liquefied into condensate, which is returned to the reactor pressure vessel through the condensate system having a condensate desalination device and the water supply system. A circulation line that bypasses the condensate demineralizer and returns to the condenser is installed, and when the condensate is circulated through the circulation line at the time of plant startup immediately after plant construction or immediately after regular inspection, a vacuum is generated inside the condenser. Then, a carbon dioxide gas removing mechanism for removing carbon dioxide gas in the condensate is installed.

That is, at the time of plant startup immediately after plant construction or immediately after regular inspection, condensate is circulated through the circulation line while bypassing the condensate demineralizer, and the carbon dioxide removal mechanism evacuates the condenser to circulate it. Try to remove carbon dioxide from the condensate.

In the boiling water nuclear power plant according to the second aspect of the invention, the steam generated in the reactor pressure vessel is introduced into a turbine for power generation, and the worked steam is introduced into a condenser to be condensed and liquefied. In a boiling water nuclear power plant that returns to the reactor pressure vessel via a condensate system having a condensate demineralizer and a water supply system, condensate from a condenser is converted to the condensate demineralizer. A circulation line to bypass and return to the condenser is installed, and when the condensate is circulated through the circulation line at the time of plant startup immediately after plant construction or immediately after regular inspection, the condenser is evacuated to generate carbon dioxide in the condensate. A carbon dioxide gas removal mechanism for removing gas was installed, and further connected to the reactor pressure vessel, a suppression pool located below this reactor pressure vessel, a pure water storage tank connected to the condenser, and a condenser. Condensate storage tank It is characterized in that it has established a degassing mechanism on at least one of the click.

That is, in the structure of the first invention, the reactor pressure vessel, the suppression pool located below the reactor pressure vessel, the pure water storage tank connected to the condenser, and the condensate storage connected to the condenser. The structure in which a deaeration mechanism is installed in at least one of the tanks is added to facilitate the quick and effective removal of carbon dioxide gas.

[Embodiment of the Invention] A first embodiment of the first invention will be described below with reference to FIG. FIG. 1 is a diagram showing a schematic configuration of a BWR plant according to this embodiment, in which reference numeral 1 is a reactor pressure vessel. Cooling water 2 and a core 3 are contained in the reactor pressure vessel 1. The core 3 is composed of a plurality of fuel assemblies, control rods, and the like, which are not shown. The coolant 2 flows upward in the core 3 and, at that time, is heated by the nuclear reaction heat of the core 3. The heated coolant becomes a two-phase flow state of water and steam. The coolant in the two-phase flow state is introduced into a steam / water separator (not shown) installed above the core 3 and separated into steam and water. The separated steam is introduced into a steam dryer installed above the steam separator to be dried and becomes dry steam. This dry steam is transferred to the turbine system 5 via the main steam pipe 4 connected to the reactor pressure vessel 1. A main steam isolation valve 6 is inserted in the main steam pipe 4. The steam transferred to the turbine system 5 is used for power generation and then introduced into the condenser 7. It is condensed and liquefied in the condenser 7 to become condensed water. Reference numeral 8 in the drawing is a drain pipe, and a main steam drain valve 9 is inserted in the drain pipe 8.

The condensate is transferred to the condensate filter 11 and further to the condensate demineralizer 12 via the condensate pipe 10 connected to the condenser 7,
It is returned to the reactor pressure vessel 1 via the water supply pipe 13. A condensate pump 14 is inserted in the condensate pipe 10.
A water supply valve 15 is inserted in the water supply pipe 13. A bypass pipe 16 is arranged in the condensate demineralizer 12, and a bypass valve 17 is inserted in the bypass pipe 16. A minimum flow pipe 18 is arranged between the water supply pipe 13 and the condenser 7, and an automatic opening / closing valve 19 is inserted in the minimum flow pipe 18. A condensate / water recirculation pipe 20 is arranged between the water supply pipe 13 and the condenser 7. An on-off valve 21 is inserted in the condensate / feed water recirculation pipe 20. A make-up water pipe 22 is connected to the condenser 7.
A deaerator 23 is inserted at 2. The deaerator 23 is a so-called thermal deaerator, and is equipped with, for example, an electric heater to raise the water temperature and reduce the solubility of carbon dioxide to remove carbon dioxide from water. Further, a carbon dioxide removing mechanism 29 is connected to the condenser 7. The carbon dioxide removing mechanism 29 is composed of a vacuum pump and an ejector (not shown). That is, when the condensate is circulated before the plant is started, carbon dioxide is removed from the condensate circulated under the atmospheric pressure in the condenser 7 by the vacuum pump and the ejector.

The operation will be described based on the above configuration. Before starting the plant immediately after the plant construction or immediately after the periodic inspection, the condensate pump 14 is first activated to circulate the condensate in a line that bypasses the condensate desalination device 12. That is, the bypass valve 17
Further, the automatic opening / closing valve 19 is opened, and the condensate is circulated in the line connecting the condensate pipe, the condensate filtering device 11, the bypass pipe 16 and the minimum flow pipe 18. At that time, the water supply valve 15 and the opening / closing valve 21 are open. After that, the automatic opening / closing valve 19 is closed and the opening / closing valve 21 is opened, and the condensate is circulated in the line connecting the water supply pipe 13 and the condensate / water supply recirculation pipe 20. Simultaneously with such circulation operation, the inside of the condenser 7 is evacuated by the vacuum pump and the ejector. As a result, deaeration is performed so that the condenser 7 becomes a vacuum, and carbon dioxide gas in the condensate is effectively removed. On the other hand, when the plant starts up, the temperature inside the reactor pressure vessel 1 is raised and increased. Then, when the temperature reaches about 80 ° C., the main steam drain valve 9 is opened to degas the inside of the reactor pressure vessel 1 through the drain pipe 8 to remove carbon dioxide gas in the reactor water. After degassing in this way, the bypass valve 17 is closed and the condensate flows through the condensate demineralizer 12.
At this time, sufficient deaeration has already been performed and carbon dioxide has been removed, so the ion load in the condensate demineralizer 12 is also greatly reduced.

As described above, according to the present embodiment, the condensate is condensed by the condensate demineralizer 12 immediately after the plant construction or immediately after the periodic inspection before the plant is started.
Since it is circulated in a line that bypasses the degasser, the carbon dioxide gas in the condensate can be effectively removed.
As a result, when condensate flows through the condensate demineralizer 12 when the plant is started, the ion load on the condensate demineralizer 12 can be significantly reduced. Therefore, the problem of excessive ion load at the time of plant startup, which had been a concern in the past, has been resolved, and it is possible to operate the ion exchange resin without using it for a certain period of time and then discard it, and also to extend the certain period of time. To be done. Specifically, the ion load is about 12, and as a result, the above period is doubled. The ion load is 12 here for the following reason. That is, the forms in which carbon dioxide gas is dissolved and becomes a load of the ion exchange resin are HCO ₃ ⁻ and CO ₃ ²⁻ . The _HCO ³ -, the total concentration of _CO ^{3 2-,} in addition to the impurity ions in the water, for example ^Cl -, is the same as the total amount of _SO ^{4 2-like,} thus _HCO ³ in water -, _CO ^{3 2-} is When removed, the ion load becomes 12. Further, carbon dioxide gas in the reactor pressure vessel 1 is also removed through the drain pipe 8, and the makeup water to the condenser 7 is also degassed by the deaerator 23. Therefore, carbon dioxide gas in the condensate water and the reactor water can be effectively removed. Reference numeral 30 in the figure denotes a degassing pipe of the deaerator 23.

Next, a second embodiment will be described with reference to FIG. In the second embodiment, a deaerator 25 is attached to the condensate / feed water recirculation pipe 20 to remove the carbon dioxide gas in the condensate more quickly than in the first embodiment. This will be described below. A bypass pipe 24 is arranged in the on-off valve 21, and a deaerator 25 is inserted in the bypass pipe 24. The deaerator 25 is a heating deaerator like the deaerator 23. Further, on-off valves 26 and 27 are inserted on the inlet side and the outlet side of the deaerator 25. Further, the deaerator 25 is provided up to the condenser 7 to which a deaeration pipe 28 is connected. That is, the carbon dioxide gas from which the deaerator 25 has been removed is sucked into the condenser 7 through the degassing pipe 28, and then sucked and removed by the vacuum pump and the ejector. The other structure is the same as that of the first embodiment, and the description thereof is omitted.

Therefore, condensate must be degassed from the condensate / water recirculation pipe 20 to the deaerator 25.
The carbon dioxide gas is removed by the deaerator 25 at the time of circulation through the line that passes through and returns to the condenser 7. Therefore, the same effects as those of the first embodiment can be obtained, and the carbon dioxide gas can be removed more quickly.

Next, an embodiment of the second invention will be described with reference to FIGS. 3 and 4. This embodiment is the same as the first embodiment or the second embodiment of the first invention except that the deaeration mechanism in the pure water storage tank, the deaeration mechanism in the condensate storage tank, and the reactor pressure vessel At least one of the degassing mechanism of No. 1 and the degassing mechanism in the suppression pool is added. The third
In the figure, the structure corresponding to the first or second embodiment of the first invention is omitted. In the figure, reference numeral 31 is a pure water storage tank, 32 is a condensate storage tank, and a bubbling type deaeration mechanism 32 is installed in each of the pure water storage tank 31 and the condensate storage tank 32. A bubbling type deaeration mechanism 33 is also installed in the reactor pressure vessel 1 and the suppression pool 34. Therefore, the configuration of the bubbling type deaeration mechanism 33 will be described with reference to FIG. Reference numeral 35 in FIG. 4 denotes a tank, which corresponds to the pure water storage tank 31, the condensed water storage tank 32, the reactor pressure vessel 1 or the suppression pool 34. In the lower part of the tank 35, nitrogen gas is jetted through a nitrogen gas (N ₂ ) jet nozzle 36. The nitrogen gas jet nozzle 36 is connected to a nitrogen gas cylinder 38 via a pipe 37. Further, two open / close valves 39 are inserted in the pipe 37. Then, the carbon dioxide gas in the treated water is degassed by spouting nitrogen gas from below in a state where the treated water is introduced into the tank 35 through the treated water introducing pipe 40. The degassed carbon dioxide gas is exhausted through the degassing pipe 41, while the degassed treated water is transferred to a desired place through the treated water pipe 42. The bubbling degassing mechanism 33 having such a configuration removes carbon dioxide gas in the pure water storage tank 31, the condensate storage tank 32, the suppression pool 34, or the reactor pressure vessel 1, and the condensate demineralizer 12 It reduces the ion load in.

Therefore, not only the same effects as those of the first and second embodiments of the first invention can be obtained, but also the carbon dioxide gas can be removed more effectively, and the ion load in the condensate demineralizer 12 can be improved. Is extremely effective in reducing

[Effects of the Invention] As described in detail above, according to the boiling water nuclear power plant according to the first and second inventions, carbon dioxide gas in the plant can be effectively removed, and immediately after the plant construction or the periodic inspection. The ion load on the condensate demineralizer at the time of plant startup can be significantly reduced, and as a result, the ion exchange resin of the condensate demineralizer is used for a certain period without being regenerated and then discarded. Can be hired. At that time, the above-mentioned certain period can be extended.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a boiling water nuclear power plant according to a first embodiment of the first invention, and FIG. 2 is a configuration of a boiling water nuclear power plant according to a second embodiment of the first invention. FIG. 3, FIG. 3 and FIG. 4 are views showing an embodiment of the second invention, FIG. 3 is a view showing the configuration of a boiling water nuclear power plant, and FIG. 4 is a bubbling degassing mechanism. It is a figure which shows the structure of. 1 ... Reactor pressure vessel, 5 ... Turbine system, 7 ... Condenser, 1
0 ... Condensate pipe 12 ... Condensate demineralizer, 13 ... Water supply pipe, 1
6 ... Bypass piping, 17 ... Bypass valve, 18 ... Minimum flow line, 20 ... Condensate / supply water recirculation piping, 29 ... Carbon dioxide removing mechanism, 31 ... Pure water storage tank, 32 ... Condensate storage tank, 33 ... Bubbling Degassing mechanism, 34 ... Suppression pool.

Claims (4)

[Claims] 1. The steam generated in a reactor pressure vessel is introduced into a turbine for power generation, and the steam that has worked is introduced into a condenser to be condensed and liquefied to be condensed water, and condensed water is removed. In a boiling water nuclear power plant that returns to the reactor pressure vessel via a condensate system having a salt system and a water supply system, the condensed water from the condenser bypasses the condensate desalination apparatus and is returned to the condenser. A carbon dioxide removal mechanism that installs a circulation line and evacuates the inside of the condenser to remove carbon dioxide gas when the condensate is circulated through the above circulation line when the plant is started immediately after the plant construction or immediately after the periodic inspection. A boiling water nuclear power plant characterized by being installed. 2. The boiling water nuclear power plant according to claim 1, wherein the circulation plane has a degassing mechanism. 3. The boiling water nuclear power plant according to claim 1, wherein the condenser has a deaeration mechanism in its makeup water system. 4. The steam generated in the reactor pressure vessel is introduced into a turbine for power generation, and the worked steam is introduced into a condenser to be condensed and liquefied to be condensed water and condensed water is removed. In a boiling water nuclear power plant that returns to the reactor pressure vessel via a condensate system having a salt system and a water supply system, condensate from the condenser bypasses the condensate demineralizer and returns to the condenser. A carbon dioxide removal mechanism that installs a circulation line and evacuates the inside of the condenser to remove carbon dioxide gas when the condensate is circulated through the above circulation line when the plant is started immediately after the plant construction or immediately after the periodic inspection. And a reactor pressure vessel, a suppression pool located below the reactor pressure vessel, a pure water storage tank connected to the condenser, and a condensate storage tank connected to the condenser. Take off one Boiling water nuclear power plant, characterized in that they have installed mechanisms.