JPS61245087A - Nuclear power generating plant - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a nuclear power plant, and particularly to a nuclear power plant equipped with a carbon dioxide removal device.

[Background of the invention]

In boiling water nuclear power plants, in order to maintain the quality of secondary cooling water as pure water, a condensate demineralizer is installed downstream of the condenser, as described in Japanese Patent Application Laid-open No. 1870871/1987. We are prepared. Condensate demineralizer The granular cation exchange resin and anion exchange resin are mixed and filled, and the demineralizer is composed of several demineralizers of several rn'/tower. This ion exchange resin is chemically regenerated once or twice a year and used repeatedly. An example of a conventional chemical regeneration method is shown in FIG. 4. The ion exchange resin 14 whose desalination performance in the condensate demineralization tower 7 has decreased is transferred to the ion exchange resin regeneration tower 15, and the injected water 16 is transferred to the ion exchange resin regeneration tower 15.
．． The air 17 separates the resin into an anion exchange resin 18 and a cation exchange resin 19 due to the difference in specific gravity. The separated anion exchange resin 18 is transferred to an anion exchange resin regeneration tower 20. Cation exchange resin 19 is regenerated with sulfuric acid 22 in regeneration tower 15, and anion exchange resin 18 is regenerated with sodium hydroxide solution 21 in regeneration tower 20. The regenerated resin is sufficiently washed with water, then transferred to the resin mixing tower 23, where the cation exchange resin and anion exchange resin are mixed, and then charged into the condensate demineralization tower 7 again. Water and air 17 are used for mixing and transferring the resin. Wastes such as regenerated liquid waste generated during these regenerations amount to about 20% of the amount of waste generated in the entire boiling water nuclear power plant. However.

The ion removal performance of ion exchange resins decreases as the amount of adsorbed ions increases, but the performance of anion exchange resins deteriorates particularly quickly. Anion exchange resins adsorb carbon dioxide gas in the air and bicarbonate ions generated when carbon dioxide gas dissolves in water during operations such as regenerating, cleaning, and transferring the resin, creating an ionic load. In the condensate recirculation operation performed during periodic inspections of type nuclear power plants, water in contact with air
Since a large amount of water is passed through the three desalination towers, the ion load due to carbon dioxide gas in the air also increases at this time.

In conventional boiling water nuclear power plants, no measures have been taken to prevent the negative effects of carbon dioxide in the air on the anion exchange resin as described above, so the ion exchange resin is regenerated frequently and a large amount of recycled waste liquid is generated. It is the cause of this.

JIS K2SO3 is the method for removing carbon dioxide from gas.
It was detailed in the Japanese Standards Association in 1975.

[Purpose of the invention]

An object of the present invention is to provide a nuclear power plant that can extend the life of the ion exchange resin in the condensate demineralizer in the nuclear power plant.

[Summary of the invention]

The nuclear power plant of the present invention includes a nuclear reactor, a condenser for condensing steam, a condensate demineralizer for purifying condensate using ion exchanger resin, and a feedwater heater as the main components. The present invention is characterized in that a carbon dioxide removal device for removing carbon dioxide from the air is provided at the air inlet that flows into the plant.

The present invention was made based on the following study results.

In a boiling water nuclear power plant, the types of adsorbed ions and the percentage of the adsorbed amount to the exchange capacity of the anion exchange resin and cation exchange resin used for one year in the condensate demineralizer are
As shown in the figure. Anion exchange resin contains 7 to 15 carbonate ions.
%, chloride ions and sulfate ions were less than 2%. The cation exchange resin contains 5-15% ferric ions, copper, and nickel.

The total amount of zinc, cobalt, etc. was 1% or less.

The amount of iron ions adsorbed by cation exchange resins is decreasing due to improvements in condensers and plant structural materials upstream thereof. On the other hand, the carbonate ions adsorbed on the anions are significantly larger than the value calculated assuming that the conductivity is entirely occupied by carbonate ions during operation at the demineralizer inlet. From this, the carbonate ions adsorbed on the anion exchange resin are not present in the sub-cooling water of the plant during operation.

For example, it is thought to be mixed in during resin chemical regeneration operations, operation of condensate demineralizers during reactor shutdown, storage, etc. Therefore, we investigated the effects of carbon dioxide gas in the air. According to a 1980 survey, the concentration of carbon dioxide in the air was 0.0338.
% (Chemical Society of Japan, Chemistry and Industry, No. 38)
Volume No. 1.

pill, (1985)). When carbon dioxide gas dissolves in water, it forms carbonic acid as shown in equation (1), and dissociates as shown in equation (2), resulting in CO2+ H20= H2CO3...(1)8
2 CO3"H"+HCO3-...(2) Generates bicarbonate ions. Carbon dioxide concentration in the air 0.0338pp
The carbon dioxide concentration in water that is in solubility equilibrium with
(1966), as shown in Figure 6, 0.44 ppm dissolves at 25°C. When water in contact with air is passed through an anion exchange resin, all of these carbonate ions are exchanged with the OH- groups of the ion exchange resin and adsorbed. In addition, the sodium hydroxide (NaOH) solution used to regenerate the anion exchange resin can interact with carbon dioxide gas in the air (3).
The reaction occurs as shown in equation (4), and carbon dioxide gas can be dissolved close to the neutralization point.

NaOH+CO24Na2 CO3−-(3)Na2
CO342Na+C○3-- *-(4) A portion of the carbonate ions dissolved in this manner are also adsorbed onto the anion exchange resin.

Further, in boiling water nuclear power plants, periodic inspections are conducted once a year, and at this time, condensate and feed water recirculation operations are performed immediately before the reactor is shut down and started. This circulates pure water through the condensate system piping or water supply system piping through the condenser and condensate demineralizer, and since the condenser is filled with air when the reactor is shut down (1) Based on the formula 2), carbon dioxide gas in the air becomes carbonate ions and is captured by the anion exchange resin of the condensate demineralizer. For example, the conductivity of water at the inlet of the condensate demineralizer during condensate recirculation is 0.15 to 0.4μS.
/ am, this increase in conductivity is due to carbonate ions. As a result, the anion exchange resin in the demineralization tower used during condensate recirculation is occupied by about 1/3 carbonate ions of the total ion exchange capacity.

The ion load adsorbed on the anion exchange resin in this way is determined by the flow-through ion exchange capacity (unlike the total ion exchange capacity), as shown in Figure 7. When the rate reaches 0.1 μS/cm, the exchange capacity (an indicator of dynamic ion exchange capacity) decreases significantly.

Based on the above study results, it is important to consider the following in the operation and operation of the demineralizer during regeneration of anion exchange resin and during reactor shutdown.
If carbonate ions based on carbon dioxide gas in the air are prevented from being adsorbed to the anion exchange resin.

It has been found that it can be used for a long period of time without any regeneration operation, and that it is also possible to operate without regeneration (disposal without regeneration for 2 to 5 years of its life due to natural deterioration of the anion exchange resin).

On the other hand, granular soda-lime soda asbestos, etc., are commercially available as carbon dioxide adsorbents, and a carbon dioxide absorption tower filled with these is installed in one part of the plant to absorb the carbon dioxide from the air that comes into contact with water or chemical solutions. By supplying through the absorption tower, the influence of the carbon dioxide gas can be eliminated.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG. 1 below.

During operation of a boiling water nuclear power plant, steam 2 generated in the yK subreactor 1 drives a turbine 3 and turns into water in a condenser 4.
Condensate collects in the hot well 5 and passes through the filter 6 and condensate demineralizer 7
The water is purified by water, passes through the feed water heater 8, and returns to the reactor 1. When a nuclear reactor is shut down for periodic inspection or the like, the condenser 4 is vacuum destroyed after fuel combustion is stopped and the temperature of the reactor water is lowered.

To break the vacuum, the vacuum break valve 9 is opened and air is introduced.

After the steam 2 has stopped flowing into the turbine 3.

The condensate is circulated through the feedwater recirculation pipe 10 or the condensate recirculation pipe 11, and the water during this recirculation comes into contact with air in the condenser 4 and absorbs gas. A carbon dioxide absorption tower 12 is installed at the air intake of the condenser 4 to prevent carbon dioxide from flowing into the condenser 4 and to prevent carbonate ions from flowing into the anion exchange resin in the condensate demineralizer 4. Prevent adsorption.

In addition, when starting the reactor, the vacuum breaker valve 9 of the condenser 4
is closed and the inside of the condenser 4 is evacuated by the condensate vacuum pump 13, and then nuclear heating of the nuclear reactor 1 is performed, but condensate recirculation is also performed before the start of operation. Before this condensate recirculation operation, the condensate vacuum pump 13 is driven with the condensate vacuum break valve 9 open, air is introduced through the carbon dioxide absorption tower 12, and carbon dioxide gas is released into the condenser 4. By performing condensate recirculation in the absence of condensate, adsorption of carbonate ions to the condensate demineralizer can be prevented.

The amount of carbon dioxide absorbent filled in the carbon dioxide absorption tower 12 is
If the total pore volume of the condenser 4 and turbine room 5 is 5000 m, the amount of carbon dioxide in the air is 3.32 kg, so by recirculating the condensate after the reactor shuts down and before starting the operation, If 5 times this amount of air passes through the carbon dioxide absorption tower 12 (however, if soda lime is used, the absorption amount is 25
% (JIS K2SO3 (1975)). )is necessary.

According to this embodiment, when the condensate demineralizer is operated while the nuclear reactor is shut down, adsorption of carbonate ions to the anion exchange resin due to carbon dioxide gas in the air can be prevented, so the regeneration frequency of the ion exchange resin can be reduced compared to the conventional year. This can be done from once or twice a year to once every two to three years, and the amount of recycled waste liquid generated can be reduced or eliminated.

[Embodiments of the invention]

A second embodiment is shown in FIG.

To regenerate the ion exchange resin 14 of the demineralization tower 7 whose ion exchange performance has deteriorated among the plurality of condensate demineralization towers installed in a boiling water nuclear power plant, the ion exchange resin 14 is transferred to the regeneration tower 15. Using water 16 and air 17, the anion exchange resin 18 and cation exchange resin 19 are separated by the difference in specific gravity, and the anion exchange resin 14 is transferred to a regeneration tower 20, and the anion exchange resin is transferred to a sodium hydroxide solution 21. After the cation exchange resin 19 is regenerated with sulfuric acid 22 and sufficiently washed with water 16, both ion exchange resins are transferred to the mixing column 23.
The water is mixed in the condensate demineralizer 7 and sent back to the condensate demineralizer 7. In this ion exchange resin regeneration, the water 16 is purified by converting the raw water 24 into pure water using the ion exchange resin 26 of the demineralizer 25 and then adding it to the pure water tank 2.
It can be stored in 7. The pure water tank 27 is equipped with a decarbonation gas tower 12 in an opening such as a manhole, and air enters and leaves the pure water tank only through this decarbonation gas tower 12.

Air 17 used for transporting, separating, etc. the ion exchange resin is obtained by passing outside air 28 through a decarbonation gas tower 12 to a compressor 29.
It is compressed and used.

Sodium hydroxide used for regenerating anion exchange resin is
A decarbonation gas column 12 is provided in the opening of the storage tank 30, so that the air in the tank 30 is passed through the decarbonation gas column, and sodium hydroxide is dissolved and stored therein.

An example of how the decarbonation gas tower 12 is used is shown in FIG.

A pipe 32 can be fixed to a manhole 31 of a storage tank 27, and a decarbonation gas column 12 filled with granular soda lime 33 is fixed to the pipe 32. Decarbonation gas tower 12
The structure is such that it can be attached and removed, and the carbonic acid adsorbent can be replaced, and a net 37 is placed in the front and rear of the carbonic acid adsorbent to prevent it from scattering. The capacity of this carbon dioxide absorption tower varies depending on the capacity of the storage tank and the amount of air passing through. For example, when soda lime is used as an adsorbent, the carbon dioxide absorption capacity is 25% (JIS K 86031975)
It is. On the other hand, the carbon dioxide concentration in the air is 0.0338%
It is. The carbon dioxide gas in 1 volume of air is 0.0338 Q,
This weight is 0.66g in standard condition. According to this example, when the capacity of one condensate storage tank in a boiling water nuclear power plant is 2000 tons and the air in the tank is replaced five times, the amount of soda coal required is the ionization of the condensate demineralizer. During operations such as transferring, separating, backwashing, cleaning, and regenerating the exchange resin, it is possible to eliminate the carbonate ion load that is adsorbed on the anion exchange resin due to carbon dioxide gas in the air, making it possible to regenerate the resin. The frequency can be reduced or eliminated, which has the effect of reducing the amount of waste generated from nuclear power plants.

By reducing resin regeneration to zero, the generation of highly corrosive concentrated waste liquid that concentrates recycled chemicals is eliminated, which not only reduces the type and amount of waste generated, but also improves the corrosive environment within the plant. Contribute.

〔Effect of the invention〕

According to the present invention, reducing the condensate demineralizer regenerated waste liquid to zero;
The equipment for the chemical regeneration system can be downsized, and the regeneration waste liquid concentrator can be eliminated.

Therefore, the type and amount of waste generated from boiling water nuclear power plants can be reduced and further.

Equipment costs can be reduced. Table 1 shows the effects of the present invention.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 show a main system diagram of a boiling water nuclear power plant and a system around a condensate desalination device showing an embodiment of the present invention. FIG. 3 shows the structure and usage example of a carbon dioxide absorption tower, and FIG. 4 shows a conventional method for regenerating a condensate demineralizer. Fifth [! I
is the ion load of the resin actually used, Figure 6 is the solubility of carbon dioxide in the air in water, and Figure 7 is the decrease in the through-flow ion exchange capacity of the anion exchange resin that has adsorbed carbonate ions. Each is shown below. 1... Nuclear reactor, 3... Turbine, 4... Condenser,
5... Hot well, 6... Condensate filter, 7...
Condensate demineralizer, 8... Feed water heater, 9... Condensate vacuum break valve, 10... Feed water recirculation piping, 11... Condensate recirculation piping, 12... Carbon dioxide adsorption Tower, 13... Condensate vacuum pump, 14... Ion exchange resin, 15... Ion exchange resin regeneration tower. 16... Water, 17... Air, 18... Anion exchange resin, 19... Cation exchange resin, 20... Anion exchange resin regeneration tower, 21... Sodium hydroxide solution, 22... Sulfuric acid, 23... Mixing column, 24... Raw water, 25... Pure water production equipment, 27... Pure water storage tank, 28... Outside air, 29... Compressor, 30
... Sodium hydroxide solution storage tank, 31... Manhole, 32... Piping, 33... Carbon dioxide adsorbent, 37... Net. Figure 3 Figure 5 Anion exchange resin Cation exchange resin Saiwaicho 3 Kiga

Claims (1)

[Claims] 1. A nuclear power plant whose main components include a nuclear reactor, a steam turbine, a condenser that condenses steam, a condensate demineralizer that purifies condensate using an ion exchange resin, and a feedwater heater. A nuclear power generation plant characterized in that a carbon dioxide removal device for removing carbon dioxide from the air is provided at an air inlet that flows into the plant. 2. Claim 1, characterized in that a carbon dioxide removal device is provided in a part of the piping having the vacuum breaker valve of the condenser.
Nuclear power plant as described in section. 3. The nuclear power plant according to claim 1, wherein the anion exchange resin regeneration device is provided with a carbon dioxide removal device. 4. The nuclear power plant according to claim 1, characterized in that a washing device for washing the regenerated ion exchange resin with water is provided with a carbon dioxide removal device. 5. The nuclear power plant according to claim 1 or 2, wherein the carbon dioxide absorbent of the carbon dioxide removal device is soda lime or soda asbestos.