JP6089434B2 - Pure water conductivity reduction device - Google Patents

Description

The present invention, carbon dioxide dissolved in the pure water, relates reduced conductivity method and apparatus of the pure water to be removed by using an inert gas, can be reduced the conductivity of pure water, especially in a short time a related conductivity low GenSo location of pure water.

  Pure water used in a power generation plant or the like is managed with a management reference value for conductivity in order to prevent corrosion of piping and the like. In particular, in a nuclear power plant, the conductivity of pure water is strictly controlled in order to suppress stress corrosion cracking of the reactor pressure vessel and the reactor internal structure.

FIG. 6 shows an example of a pure water supply path in a conventional nuclear power plant. As shown in FIG. 6, pure water W produced by a pure water production apparatus (not shown) is supplied from the direction of arrow F1 to the storage tank 10 via the upstream pipe 2 and the valve 3, and temporarily stored in the storage tank. 10 is stored. The storage tank 10 has a tank body 11 for storing pure water W, and a filter 11 b is provided on the upper part of the tank body 11. An overflow pipe 11 c is attached to the side surface of the tank body 11. The pure water W stored in the storage tank 10 is supplied to the nuclear power plant through the valve 4 and the downstream pipe 5 and used as primary cooling water. The management of the conductivity is performed based on the pure water W in the pure water production apparatus outlet and the storage tank.

  2. Description of the Related Art Conventionally, techniques related to a method for producing pure water are known (see, for example, Patent Documents 1 and 2). The pure water production method of Patent Document 1 is for producing pure water with low electrical conductivity in accordance with fluctuations in the quality of raw water. In the pure water production method of Patent Document 2, a PH adjustment tank for adjusting the pH of water and a nitrogen gas bubbling tower are provided in the raw water inflow line so as to reduce the discharge amount of regenerated waste liquid.

JP 11-114596 A JP 2001-87795 A

However, in the pure water supply path in the conventional nuclear power plant shown in FIG. 6, the pure water W produced by the pure water production apparatus is temporarily stored in the storage tank 10 and then the nuclear power plant side. Therefore, in the process of storing in the storage tank 10, there is a problem that CO ₂ is dissolved in the pure water W and the conductivity may exceed the management reference value. That is, the conductivity of the pure water W is several tens μS / m in the pure water W produced by the pure water production apparatus, but increases to several hundred μS / m in the process of storing in the storage tank 10. There is a problem.

  As countermeasures in this case, at present, treatments such as disposal of pure water with high conductivity (replacement of pure water) or purification of pure water with a desalting apparatus are performed, but these require prompt action. Therefore, it is necessary to always consider situation monitoring, securing of water, and response time, and there is a problem that the load on operation management becomes large.

The present invention, even when used in temporarily storing the pure water produced, to provide a conductivity lower GenSo location of pure water which can reduce the conductivity of pure water in a short time With the goal.

The invention according to claim 1 in order to achieve the above object, a conductivity reducing device of the pure water is installed in the storage tank of the downstream side of the pure water production device, senses the conductivity of the pure water Supplying inert gas to the pure water stored in the storage tank with a plurality of ejection holes in the supply flow path extending to the vicinity of the bottom of the tank via the overflow pipe of the storage tank through the conductivity detection means And determining whether or not the conductivity of the pure water is within an allowable range based on information from the inert gas supply means and the conductivity detection means, and the conductivity of the pure water exceeds the allowable range If there is a conductivity determination means for commanding the supply of the inert gas from the inert gas supply means to the pure water, and the supply flow path for the inert gas based on a command from the conductivity determination means And a control valve that opens and closes. To.

  According to this invention, when the inert gas and pure water come into contact, carbon dioxide dissolved in the pure water is adsorbed by the inert gas, and the conductivity of pure water is reduced.

The invention described in claim 2 is the conductivity reducing apparatus for pure water according to claim 1, further comprising temperature detecting means for detecting the temperature of the pure water, wherein the conductivity determining means is the conductivity detecting means. in correcting the sensed conductivity with temperature detected by said temperature detecting means, you characterized in that the conductivity of the pure water on the basis of the corrected electrical conductivity to determine whether an acceptable range.

The invention described in claim 3 is the conductivity reducing device of the pure water according to claim 1 or claim 2, wherein the inert gas, you being a nitrogen gas.

According to the first aspect of the present invention, the carbon dioxide dissolved in the pure water is removed by bringing the inert gas into contact with the pure water. Even when the conductivity of the pure water increases, the conductivity of pure water can be reduced in a short time. As a result, the conductivity can be returned to the pure water within the management reference value in a short time, and a quick response can be taken compared to the conventional case. Further, since it is not necessary to dispose of pure water by conventional disposal of pure water or a desalinator, it is possible to reduce costs and facilitate the operation management of pure water. In particular, since the control valve of the inert gas supply flow path is opened and closed based on a command from the conductivity determining means, the work for reducing the conductivity can be automated. Furthermore, since inert gas is contained in the atmosphere in a large amount, even if inert gas is used to reduce the conductivity of pure water, there is no environmental impact and safety in operation management can be ensured. .

According to the second aspect of the present invention, since the temperature detecting means for detecting the temperature of the pure water is provided, even when the temperature of the pure water is changed with the change of the air temperature, it is detected by the conductivity detecting means. The conductivity can be temperature-corrected, and the conductivity of pure water can be accurately grasped. Thus, that it can and Do to suppress the amount of the pure water conductivity inert gas for reducing the.

According to the invention of claim 3, because of the use of inexpensive nitrogen gas as the inert gas, Ru can be suppressed cost for reducing the conductivity of pure water.

It is a schematic diagram of the electrical conductivity reduction apparatus of the pure water concerning embodiment of this invention. It is a control block diagram of the electrical conductivity reduction apparatus of the pure water of FIG. It is a flowchart which shows the procedure of the control in the electrical conductivity reduction apparatus of the pure water of FIG. It is a schematic diagram which shows the principle of the electrical conductivity reduction method of the pure water concerning embodiment of this invention. It is a schematic diagram which shows distribution of the electrical conductivity of the pure water in the storage tank in the electrical conductivity reduction apparatus of FIG. It is a schematic diagram of the supply path | route of the conventional pure water.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  1 to 3 show an embodiment of the present invention, and particularly show a case where it is applied to a nuclear power plant. As shown in FIG. 1, a pure water production apparatus 1 is provided in a facility of a nuclear power plant. The pure water manufacturing apparatus 1 manufactures pure water W to be supplied to each system of a nuclear power plant. The pure water W produced by the pure water production apparatus 1 is supplied to the storage tank 10 via the upstream pipe 2 and the first valve 3 as indicated by an arrow F1. The first valve 3 has a function of supplying and stopping the pure water W to the storage tank 10.

The storage tank 10 has a function of temporarily storing pure water W supplied from the pure water production apparatus 1. The storage tank 10 has a tank body 11, a filter 11b, and an overflow pipe 11c. The tank body 11 is formed in a cylindrical shape in the present embodiment, and has a volume of, for example, 1000 m ³ . The tank body 11 has an inner upper portion formed in the space portion 11a. The upper space portion 11a of the tank body 11 communicates with the outside through a filter 11b. The overflow pipe 11 c is attached to the side surface portion of the tank body 11. The upstream end of the overflow pipe 11c opens into the space 11a. The overflow pipe 11c has a function of discharging a part of the pure water W in the tank body 11 to the outside when the pure water W in the tank body 11 exceeds a predetermined amount.

  A downstream pipe 5 is connected to the lower part of the side surface of the tank body 11. The pure water W temporarily stored in the storage tank 10 is supplied to the plant 6 side via the second valve 4 and the downstream pipe 5 as indicated by an arrow F2. The second valve 4 has a function of supplying and stopping the pure water W from the storage tank 10 to the plant 6 side.

Since the pure water W produced by the pure water production apparatus 1 is temporarily stored in the storage tank 10 and then supplied to each system on the plant 6 side, CO ₂ is added to the pure water W during the storage process. It dissolves and the conductivity of pure water W increases. Therefore, in the present invention, in order to prevent the conductivity of the pure water W from exceeding the control reference value, the conductivity reducing device 12 is provided on the downstream side of the pure water production device 1. The conductivity reducing device 12 includes a nitrogen gas supply line 14 as an inert gas supply means, a nitrogen gas supply pipe 15 as an inert gas supply flow path, a control valve 16, a conductivity detection means 17, and a temperature detection. Means 18 and conductivity determining means 19 are provided.

The conductivity reducing device 12 can reduce the conductivity of the pure water W by supplying nitrogen gas N ₂ as an inert gas toward the pure water W stored in the storage tank 10. Yes. In this embodiment, the nitrogen gas N ₂ is supplied from a nitrogen gas supply line 14 installed in the nuclear power plant. However, as described later, the inert gas supply means is used as the nitrogen gas N 2. You may comprise from the gas cylinder which stores _2. FIG. A nitrogen gas supply pipe 15 is connected to the nitrogen gas supply line 14. The nitrogen gas supply pipe 15 passes through the overflow pipe 11 c, and the upstream portion 15 a extends to the bottom of the tank body 11. A plurality of ejection holes (not shown) through which nitrogen gas N ₂ is ejected toward the pure water W stored in the tank body 11 are formed in the upstream portion 15 a of the nitrogen gas supply pipe 15. A control valve 16 that is operated by an electric signal is provided in the middle of the nitrogen gas supply pipe 15.

  Conductivity detection means 17 for detecting the conductivity of pure water W is attached to the tank body 11 of the storage tank 10. The conductivity detector 17 has a function of converting the detected conductivity of the pure water W into an electric signal. A temperature detection means 18 for detecting the temperature of the pure water W is attached to the tank body 11 of the storage tank 10. The temperature detection means 18 has a function of converting the detected temperature of the pure water W into an electrical signal. The signal K1 from the conductivity detection means 17 and the signal K2 from the temperature detection means 18 are input to the conductivity determination means 19, respectively.

As shown in FIG. 2, the conductivity determining means 19 includes a temperature correcting unit 19a and a determining unit 19b. Pure water W, since the conductivity of the high and low temperature changes, the temperature compensation unit 19a is a function of corrected based on the temperature information of the conductivity detected by the conductivity test known means 17 from the temperature detecting means 18 Have. The determination unit 19b determines whether the conductivity of the pure water W in the storage tank 10 is within an allowable range based on the conductivity corrected by the temperature correction unit 19a, and the conductivity of the pure water W is within the allowable range. When exceeding, it has a function to command supply of nitrogen gas N ₂ from the nitrogen gas supply line 14 into the pure water W. That is, the conductivity determining means 19 outputs the supply signal K3 to the control valve 16 when the conductivity of the pure water W exceeds the allowable range, and the opening of the control valve 16 causes the pure water in the storage tank 10 to be purified. It has a function of supplying nitrogen gas N ₂ into the water W.

  Next, a method and an effect of reducing the conductivity of pure water using the above-described conductivity reducing device 12 will be described.

FIG. 3 shows a procedure of a method for reducing the conductivity of pure water W. The process is started in step 51 of FIG. 3, and in step 52, the conductivity of the pure water W in the storage tank 10 is detected by the conductivity detector 17. Next, the process proceeds to step 53 where the temperature of the pure water W in the storage tank 10 is detected by the temperature detection means 18. Next, the process proceeds to step 54, and based on the information from the conductivity detecting means 17 and the temperature detecting means 18, it is determined by the conductivity determining means 19 whether or not the conductivity of the pure water W is within an allowable range. That is, the conductivity determining means 19, the conductivity detected by the conductivity test known means 17 at a temperature compensation unit 19a corrects, based on the temperature from the temperature detecting means 18, the determination unit 19b is the corrected conductivity Based on this, it is determined whether or not the conductivity of the pure water W in the storage tank 10 is within an allowable range.

In step 54, if the conductivity of the pure water W is determined to be in the allowable range, the process proceeds to step 55, control valve 16 is kept closed, the nitrogen gas N ₂ to the storage tank 10 is not supplied. Then, it returns to step 52 and the above-mentioned process is repeated.

If it is determined in step 54 that the conductivity of the pure water W exceeds the allowable range, the process proceeds to step 56, where the control valve 16 is opened based on the supply signal K3 from the conductivity determination means 19. Then, as shown in step 57, the nitrogen gas N ₂ from the nitrogen gas supply line 14 is supplied into the storage tank 10 through the nitrogen gas supply pipe 15 and stored from the upstream portion 15 a of the nitrogen gas supply pipe 15. Nitrogen gas N ₂ is jetted toward the pure water W. Thus, the pure water W in the storage tank 10 is brought into contact with nitrogen gas N _2, CO ₂ dissolved in the pure water W is adsorbed to the nitrogen gas N _2, the conductivity of the pure water W is reduced Is done. That is, since a plurality of ejection holes (not shown) for ejecting the nitrogen gas N ₂ are formed in the upstream portion 15 a of the nitrogen gas supply pipe 15, the nitrogen gas N is contained in the pure water W in the storage tank 10. ₂ countless bubbles are generated, and the pure water W and the nitrogen gas N2 are sufficiently brought into contact with each other. As a result, CO ₂ dissolved in the pure water W is removed, and the conductivity of the pure water W decreases in a short time. Nitrogen gas N ₂ and CO ₂ in the pure water W rise to the liquid level of the pure water W with the passage of time, and then flow into the space 11 a of the storage tank 10. Nitrogen gas N2 and CO ₂ which has flowed into the space 11a of the storage tank 10, as shown by the arrow F3, is discharged to the outside through the overflow pipe 11c.

Next, returning to step 52, the above process is repeated, and when the conductivity of the pure water W falls within the allowable range, the supply of the nitrogen gas N ₂ into the storage tank 10 is stopped. Then, when the supply of the pure water W to the plant 6 side is stopped due to the inspection of the conductivity reducing device 12, the process proceeds to step 58 and the process is terminated.

Thus, in this embodiment, since the CO ₂ dissolved in the pure water W is removed by bringing the nitrogen gas N ₂ into contact with the pure water W, the temporary water of the produced pure water W is temporarily removed. Even if the electrical conductivity of the pure water W is increased by the effective storage, the electrical conductivity of the pure water W can be reduced in a short time. As a result, the conductivity can be returned to the pure water W within the management reference value in a short time, and a quick response can be taken compared to the conventional case. In addition, since it is not necessary to dispose of pure water by conventional disposal of pure water or a desalinator, it is possible to reduce costs and facilitate operation management of pure water W. Furthermore, since nitrogen gas N ₂ that is an inert gas is contained in the atmosphere in a large amount, even if nitrogen gas N ₂ is used to reduce the conductivity of pure water W, there is no environmental impact and operation. Management safety can be secured.

Moreover, because of the use of inexpensive nitrogen gas N ₂ as an inert gas, it is possible to suppress the cost for reducing the conductivity of the pure water W. Further, since the temperature detection means 18 for detecting the temperature of the pure water W is provided, even when the temperature of the pure water W changes with the change in the air temperature, the conductivity detected by the conductivity detection means 17 is temperature-corrected. The conductivity of the pure water W can be grasped with high accuracy. This makes it possible to suppress the amount of the nitrogen gas N ₂ to reduce the conductivity of the pure water W.

Next, the mechanism of CO ₂ removal and the amount of CO ₂ removal in aeration with nitrogen gas N ₂ will be described. Here, aeration means that a gas is supplied into the liquid and the gas and the liquid are brought into contact with each other.

For aeration by nitrogen gas _{N 2,} nitrogen gas _{N 2} for pure water 1.0 m ³ 1.0 liters (standard conditions) Consider the case of supplying. At this time, 1.0 liter = 1000 cm ³ = 1.0 × 10 ⁻³ m ³ . As shown in FIG. 4, 1.0 liter of supplied nitrogen gas is considered as one bubble in the pure water W. At this time, 1 mol of gas in a standard state is 22.4 liters at 0 ° C. and 1 atm. Therefore, at 25 ° C., 1.0 × 298/273 = 1.091575 liters. In addition, 1 liter of gas in a standard state is 1 / 22.4 = 0.0446428 mol.

According to Henry's law, an amount of gas in proportion to the partial pressure of each gas is dissolved in the solution. However, since no carbon dioxide is present in the nitrogen gas bubbles, carbon dioxide in pure water is sucked into the nitrogen gas bubbles from the ratio of the carbon dioxide partial pressure and the carbon dioxide partial pressure in the bubbles. The partial pressure of carbon dioxide from the water surface is 0.0003 × 1.0 atm from the composition ratio of the atmosphere. Here, since the residence in the pure water W is a sufficiently long time, the carbon dioxide is sufficiently sucked into the bubbles so as to be equal to the partial pressure of the atmospheric pressure. However, since the supplied nitrogen gas N ₂ is in a standard state, it is dissolved in the pure water W by the difference between the atmospheric partial pressures of 0.781 × 1.0 atm and 1.0 × 1.0 atm. Assuming that the temperature is 25 ° C., the dissolved nitrogen gas capacity ΔV _N2 is as follows.
ΔV _N2 = 0.0190 × (1.0−0.781) × 293/298 = 0.00040911 g = 0.000409 / 28 = 0.14611 × 10 ⁻³ mol
If the pressure remains constant, the bubble volume decreases by this amount. Therefore, the volume V ′ _N2 of the nitrogen gas bubbles after being dissolved is as follows.
V ′ _N2 = (0.0446428−0.14611 × 10 ⁻³ ) ÷ (0.0044628) × 1091.575 = 10888.0026 cm ³

Here, when the volume of carbon dioxide sucked into the nitrogen gas bubbles is V ′ _CO2 , the following equation is established.
V ′ _CO2 ÷ (V ′ _CO2 + V ′ _N2 ) = 0.0003 / 0.781 →
V ′ _CO2 = (0.0003 / 0.781) × V ′ _N2 = 0.4179267 cm ³
Therefore, the number of moles M ′ _{CO2 of} carbon dioxide present in the bubbles is as follows.
M ′ _{CO 2} = (0.4179296) ÷ (22.4 × 10 ³ ) × (273 ÷ 298) = 0.0170922 × 10 ⁻³ mol = 17.0922 × 10 ⁻⁶ mol
That is, when 1.0 liter of nitrogen gas N ₂ is supplied, 17.0922 × 10 ⁻⁶ mol of carbon dioxide is adsorbed to the bubbles and removed to the atmosphere. Here, the concentration of carbon dioxide dissolved into pure water saturation _is the _{CO 2 (aq) = K H} P CO2 = 10.2 × 10 -6 mol / l of pure water 1.0 m ³ Carbon dioxide is present at 10.2 × 10 ⁻³ mol. Therefore, the nitrogen gas capacity V _{N2 (B)} necessary for removing all carbon dioxide is as follows.
V _{N2 (B)} = 10200 × 10 ⁻⁶ /17.0922×10 ⁻⁶ = 596.76343 = 596.8 liters

Next, the amount of nitrogen gas required for removing all the saturated dissolved CO ₂ in an actual tank model is determined.

Since to pure water 1.0 m ³ is needed nitrogen gas 596.8 liters for the actual tank capacity 1000 m ^3, it is necessary to 596,800 liters = 596.8m ^3. However, this is a case where removal of all carbon dioxide is considered.

Next, the flow rate of nitrogen gas necessary for continuous ventilation is determined. The increasing tendency of conductivity due to dissolution of carbon dioxide is influenced by the state of contact between gas and liquid, and considering various literatures, for example, the conductivity may increase to the extent that water in a beaker is saturated in one hour. Conceivable. Therefore, the height of the beaker is considered to be about 10 cm, and as shown in FIG. 5, the pure water W is stored in the storage tank 10, and then CO ₂ is dissolved from the gas phase part at the upper part of the tank. Let us consider the case of 200 μS / m at 100 cm and further 100 μS / m at the bottom of 10 cm.

Here, CO ₂ concentration against 200 [mu] S / m is, 10.2 × ¹⁰ 6 mol / l = 10.2 × ¹⁰ 3 mol / l, CO ₂ concentration against 100 .mu.S / m is 5.1 × 10 ^- Considering ⁶ mol = 5.1 × 10 ⁻³ mol, the CO ₂ concentration to be removed is as follows.

Amount of CO ₂ to be removed = 100 × 0.1 × 10.2 × 10 ⁻³ + 100 × 01. × 5.1 × 10 ⁻³ = 15.3 × 10 ⁻² mol

Since the removal amount of CO ₂ by aeration with 1 liter of nitrogen gas N ₂ is 17.0922 × 10 ⁻⁶ mol, 153000 × 10 ⁻⁶ mol / 17.0922 × 10 ⁻⁶ mol = 8951.4515 liters Ventilation is required. Therefore, considering removal within one hour, 8951.4515 liters / 3600 seconds = 2.4865143 liters / second. When the bottom area of the tank is 100 m ² , it can be seen that a small air flow rate of 0.0248651 liters / ^second per 1 m ² is sufficient.

Further, considering that the dissolution of CO ₂ occurs on the upper water surface of the stored pure water W, the nitrogen gas N ₂ vented by aeration floats in the pure water W and stays in the gas phase above the tank. become. Then, as if a state where the nitrogen gas N ₂ is sealed, and to suppress the CO ₂ dissolved from the water surface. Furthermore, since the nitrogen gas N ₂ is dominant on the water surface, the partial pressure of CO ₂ is reduced, and it is considered that there is an effect of removing CO ₂ from the water surface. Considering the above, it is possible to actually perform aeration with nitrogen gas N ₂ at a flow rate smaller than the flow rate obtained by the above calculation.

In this model, the nitrogen gas N ₂ is considered as a model of one bubble. However, in reality, the gas can be divided into several bubbles and supplied as a large number of fine bubbles. When bubbles of the same volume are refined into several small bubbles, the surface area becomes larger than the original one bubble. The surface area becomes 9 times when a bubble having a volume of 1.0 liter becomes many bubbles, and the surface area becomes 99 times when many bubbles of 1.0 mm ³ are formed. As described above, since the surface area is increased by the fine bubbles, the area where the nitrogen gas N ₂ comes into contact with the pure water is increased, which leads to improvement in aeration efficiency. Moreover, when it becomes a fine bubble, since the buoyancy concerning one bubble becomes small and the time for a bubble to stay in a pure water becomes long, it leads to the improvement of aeration efficiency. Furthermore, by being miniaturized, the bubbles of nitrogen gas N ₂ can be distributed over a wide range in the storage tank 10, which also leads to an improvement in aeration efficiency.

Considering the actual operation, in pure water W stored in a tank having a capacity of 1000 m ³ and in which the dissolution of CO ₂ is saturated, nitrogen gas N ₂ is flowed in order to remove all CO ₂ in pure water W. When venting at 2.486543 liters / _second , all the CO _{2 in} 1000 m ³ of pure water can be removed in 596800 / 2.4865 = 240016.08 seconds = 66.6711 hours = 2.7 days.

In the actual storage tank 10, the conductivity is saturated around 100 μS / m, and when the conductivity temporarily rises due to an increase in temperature, etc., the conductivity is as follows for the management target value of 100 μS / m. A reduction of several tens of μS / m is sufficient. Therefore, in the case of reducing the conductivity from 100 μS / m to 75 μS / m, 596800/4 / 2.4865 = 660.0221 seconds = 16.666783 hours at a nitrogen gas N ₂ flow rate of 2.4865143 liters / second = Aeration is only required for 0.6944 days.

In the above consideration, the state of diffusion of dissolved CO ₂ is not taken into consideration, and it is considered that the actual conductivity increasing tendency is different. In the actual storage tank 10, the conductivity is saturated at about 80 μS / m while supplying 50 μS / m of pure water from the pure water production apparatus 1 at 12 m ³ / hour. As data that can be held at present, there is a track record that when this supply is stopped, the conductivity increased from 83 μS / m to 91 μS / m in 36 hours.

The increase in conductivity due to the dissolution of CO ₂ increases according to the formula of A (1-e ^−at ) + α, considering the saturation of dissolution. Strictly speaking, it is preferable to obtain an increase curve of conductivity from the above-mentioned data and the like, and to obtain a necessary air flow rate from the saturation time, but for the sake of simplicity, the following necessary flow rate is estimated.

Assuming that the increase in conductivity from 83 μS / m to 91 μS / m is linear, the CO ₂ concentration will increase from 4.07 × 10 ⁶ mol / liter to 4.46 × 10 ⁻⁶ mol / liter in 36 hours. It will be done. Therefore, in order to remove this, it is sufficient to ventilate at the following flow rate.

0.46 × 10 ⁻⁶ × 10 ⁶ mol / 17.0922 × 10 ⁻⁶ mol / (36 × 3600 seconds) = 0.2077 liters / second As described above, this is actually the nitrogen gas N ₂ Since the miniaturization and the sealing effect can be expected, aeration with nitrogen gas N ₂ becomes possible with a smaller flow rate.

Further, when the supply of nitrogen gas N ₂ is considered as a gas cylinder (capacity per cylinder: 7000 liters), it is 7000 liters / 0.277 liters / second = 9.36 hours. Supply for 36 hours is possible, and a 24-hour aeration is sufficient if three cylinders are used.

As described above, when the storage tank 10 has a capacity of 1000 m ³ and CO ₂ is dissolved in a saturated state in the pure water W stored in the storage tank 10, all the CO in the pure water W is dissolved. _In order to remove ₂ , aeration with 596.8 m ³ (596800 liters) of nitrogen gas N ₂ is required. In order to suppress the increase in the conductivity due to the dissolution of CO ₂ by continuous ventilation, the 1000 m ³ storage tank 10 may be aerated at a flow rate of 2.49 liters / second. However, since the required flow rate is increased in proportion to the tank capacity, a minute air flow rate of 0.025 liter / second per 1 m ³ is sufficient. Further, it is presumed that the necessary ventilation amount is small due to the sealing effect by the nitrogen gas N ₂ , and the above-mentioned flow rate of 2.49 liters / second is a large value with a margin from the viewpoint of maintenance.

Further, the storage tank 10 of 1000 m ³ of CO ₂ was dissolved in a saturated state, and hold aeration at if a flow rate 2.49 l / s and nitrogen gas _{N 2,} 67 hours for all in (2.7 days) CO ₂ Can be removed. At present, when it is saturated at 100 μS / m, in order to reduce a slight increase due to pH, temperature change, etc., the air flow rate of 2.49 liters / second is used to reduce the conductivity by several tens μS / m. For 17 hours (0.7 days). However, the actual increase in conductivity is more gradual than the above assumption, and it can be operated at a lower air flow rate (0.21 liter / second).

The embodiment of the present invention has been described in detail above, but the specific configuration is not limited to the above-described embodiment, and even if there is a design change or the like without departing from the gist of the present invention, It is included in this invention. For example, in this embodiment, nitrogen gas N ₂ is used as an example of an inert gas, but the gas is not limited to nitrogen gas N ₂ as long as it is a gas capable of adsorbing CO ₂ . Further, in this embodiment, the nitrogen gas N ₂ is supplied into the pure water W in the storage tank 10, but the nitrogen gas is contained in the pure water W flowing through the upstream side pipe 2 or the downstream side pipe 5. N ₂ may be supplied. Further, the supply of the nitrogen gas N ₂ is performed by the nitrogen gas supply line 14 installed in the nuclear power plant. However, as described above, the nitrogen gas N ₂ stored in the cylinder may be supplied. .

DESCRIPTION OF SYMBOLS 1 Pure water manufacturing apparatus 10 Storage tank 11 Tank main body 11b Filter 11c Overflow piping 12 Conductivity reduction apparatus 14 Nitrogen gas supply line (inert gas supply means)
15 Nitrogen gas supply piping (inert gas supply flow path)
16 Control valve 17 Conductivity detection means 18 Temperature detection means 19 Conductivity determination means W Pure water N ₂ Nitrogen gas (inert gas)
CO ₂ carbon dioxide

Claims (3)

A reduced conductivity device of the pure water is installed in the storage tank of the downstream side of the water purifying apparatus,
Conductivity detecting means for detecting the conductivity of the pure water;
An inert gas for supplying an inert gas into pure water stored in the storage tank, having a plurality of ejection holes in a supply flow path extending to the vicinity of the bottom of the tank via an overflow pipe of the storage tank Supply means;
Based on the information from the conductivity detection means, it is determined whether the conductivity of the pure water is within an allowable range. If the conductivity of the pure water exceeds the allowable range, the inert gas supply means Conductivity determining means for commanding supply of inert gas into the pure water;
A control valve for opening and closing the supply flow path of the inert gas based on a command from the conductivity determining means;
A device for reducing the conductivity of pure water. Temperature detecting means for detecting the temperature of the pure water;
The conductivity determination means corrects the conductivity detected by the conductivity detection means with the temperature detected by the temperature detection means, and based on the corrected conductivity, the conductivity of the pure water is within an allowable range. The apparatus for reducing conductivity of pure water according to claim 1, wherein:   The conductivity reducing apparatus for pure water according to claim 1 or 2, wherein the inert gas is nitrogen gas.

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