JPH0379077B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention relates to a pure water production system for treating make-up water in a nuclear power plant, and particularly to an after-purification system installed after a pure water storage tank in a make-up water treatment system for secondary cooling water in a pressurized water type nuclear power plant. The present invention relates to a pure water production device useful as a water purifier. [Prior Art] Fig. 1 is a system diagram showing a cooling water system of a pressurized water nuclear power plant. In the figure, 1 is a nuclear reactor, 2 is a steam generator, and primary cooling water 3 is circulated between the two. Secondary cooling water 5 is circulated between the steam generator 2 and the condenser 4, and the steam evaporated in the steam generator 2 passes through the turbine 6 and becomes condensate in the condenser 4, which is then used in the condensate desalination equipment. It is desalted in step 7 and circulated to the steam generator 2. Make-up water to the secondary cooling water system is purified water 9 produced by a pure water production device 8 with a polisher, which is supplied to a pure water storage tank 10.
It is stored in the after polisher 11 to remove impurities, degassed in the deaerator 12 and supplied to the condenser 4. In the secondary cooling water system of such pressurized water nuclear power plants, impurity ions in make-up water become concentrated and cause various problems, so in addition to the absolute amount of each component, the ratio of each component is also regulated.
Water quality standards have been set for Na of 0.06 ppb or less, Cl of 0.15 ppb or less, and Na/Cl (molar ratio) of 0.3 to 0.7. In order to achieve such water quality standards, a pure water production device consisting of a mixed bed of an H-type strongly acidic cation exchange resin and an OH-type strongly basic anion exchange resin is used as the after polisher 11. , the impurity ions mixed in the pure water storage tank 10 and the like are removed and used as make-up water. [Problems to be Solved by the Invention] However, in the conventional pure water production device used as the after polisher 11, since the resin is used in the H/OH type, the pure water storage tank 10
When the anion exchange resin is saturated with CO ₂ mixed in from the atmosphere during storage and the anions break, the Cl concentration of the treated water increases and the Na/Cl molar ratio increases from 0.3 to 0.7.
become dissatisfied with In this type of pure water production equipment,
When cation exchange resin and anion exchange resin are separated and regenerated, both resins cannot be completely separated.
Since it is unavoidable that Na or Cl will leak into the treated water after regeneration, the resin is not regenerated and is replaced and disposed of as is. Therefore, in conventional pure water production equipment, the resin must be replaced frequently, and depending on the scale of the equipment, it is generally necessary to replace the resin about once a month. The purpose of this invention is to solve the above problems.
To provide a pure water production device that can maintain high treated water quality over a long period of time, can be used for makeup water treatment at a nuclear power plant, and can reduce resin replacement. [Means for Solving the Problems] The present invention is a pure water production device for treatment of make-up water in nuclear power plants, which comprises a mixed bed of a strongly acidic cation exchange resin and a strongly basic anion exchange resin. Strongly basic anion exchange resins are H type, which contains less than 0.2 equivalent% of Na form based on the total amount, and strongly basic anion exchange resins contain 0.2 equivalent% of Cl form based on the total amount.
This is a pure water production device characterized by containing only the following and 40 to 80 equivalent percent of HCO ₃ form, with the remainder being OH form. In the make-up water treatment system that supplies the secondary cooling water system of a pressurized water nuclear power plant, make-up water is transferred to condenser 4 in Figure 1.
Since the CO 2 is degassed into the deaerator 12 before being supplied to the after polisher 11, there is no need to remove _CO2 . Therefore, in the pure water production equipment used as the after polisher 11, CO ₂ is not removed.
It is only necessary to remove other impurities such as Na ⁺ and Cl ^- . Ion exchange resin exchanges and adsorbs ions in water, but when the resin exchanges and adsorbs a certain amount of ions, it reaches an equilibrium state and no longer adsorbs the same ions. In this state, the same kind of ions present in the water do not become a load on the ion exchange resin, but other ions are exchanged and adsorbed. Therefore, by using an ion exchange resin that has reached such an equilibrium state from the beginning, it is possible to adsorb only other ions without adsorbing specific ions. Looking at the anion exchange resin, if the anion exchange resin composition is in equilibrium with the dissolved concentration of HCO ₃ ^- at the water temperature of the stored pure water, the HCO ₃ ^- in the water will not be a load on the anion exchange resin. . Therefore, in the present invention, the strongly acidic cation exchange resin is of the H type, which contains only 0.2 equivalent% or less of the Na form relative to its total amount, and the strongly basic anion exchange resin is of the H type, which contains only 0.2 equivalent% or less of the Cl form relative to its total amount. Pure water is produced by performing ion exchange using a mixed bed of a strongly acidic cation exchange resin and a strongly basic anion exchange resin with a resin composition that contains 40 to 80 equivalents of HCO ₃ form and the remainder is OH form. do. The types of ion exchange resins that can be used, the mixing ratio, water flow conditions, etc. are the same as in the pure water production equipment that has been used as an after polisher for the make-up water treatment system for secondary cooling water at nuclear power plants. be. The amount of HCO ₃ form in anion exchange resins is 40-80 equivalent%, but in the treatment of water that has reached equilibrium with the normal atmosphere and has dissolved carbon dioxide gas, it is about 60 equivalent%.
is preferred. In a typical make-up water treatment system for secondary cooling water in a pressurized water nuclear power plant, an equilibrium state exists when the anion exchange resin composition is 60 equivalent percent of HCO ₃ form and the remainder is OH form. When the HCO ₃ form is less than 60 equivalent %, HCO ₃ ^- in the stored pure water becomes a load, and equilibrium is reached when the HCO ₃ form becomes 60 equivalent %. Conversely, when the HCO ₃ form is greater than 60 equivalent %, HCO ₃ ^- is released into the treated water, and equilibrium is reached with the HCO ₃ form reaching 60 equivalent %. In this case, the anion exchange resin composition of HCO ₃ type is
If it is 40 to 80 equivalent %, changes in water quality until equilibrium is reached can be tolerated. However, Comparative Example 2 described below
As shown in Figure 2, CO ₂ in the make-up water is adsorbed while collecting water in H/OH form without containing HCO ₃ form, and as a result, the HCO ₃ form of the anion exchange resin becomes 60 equivalent% and reaches an equilibrium state. If the Na/Cl ratio is allowed to reach the equilibrium state, the Na/Cl ratio will exceed the standard until the equilibrium state is reached, and it will take too long to reach the equilibrium state, which is not preferable. Preparation of HCO ₃ type strongly basic anion exchange resin is as follows:
A column is filled with an OH-type strongly basic anion exchange resin containing 0.2 equivalent% or less of Cl-type, and a NaHCO ₃ solution is passed through the column, followed by extrusion and washing with pure water. The HCO ₃ type strong basic anion exchange resin thus obtained is mixed with an OH type strong basic anion exchange resin containing Cl type 0.2 equivalent% or less at a predetermined ratio within the above range,
Furthermore, a mixed bed is formed by mixing with an H-type strongly acidic cation exchange resin containing 0.2 equivalent% or less of Na-type. The mixed bed type pure water production equipment thus formed is
It is used as the after-polisher 11 of the make-up water treatment system of pressurized water nuclear power plants, and as with conventional systems, pure water is passed through the pure water storage tank 10 for ion exchange, and the sodium contained in the pure water is removed. Removes impurities such as ⁺ and Cl ^- . At this time, HCO ₃ ^- leaks out as it is without being adsorbed by the ion exchange resin.
2 is removed as _CO2 . [Effects of the Invention] As described above, according to the present invention, since an OH type anion exchange resin containing a specific proportion of HCO ₃ type is used in the mixed bed, it can be used in cases where a large amount of carbon dioxide gas is contained in the raw water. , other impurities can be efficiently adsorbed without loading carbon dioxide gas, high treated water quality can be obtained over a long period of time, and resin replacement is less necessary. [Examples] Examples and comparative examples of the present invention will be described below. In each example, % is equivalent %. Example 1 A strongly acidic cation exchange resin Diaion SKN and a strongly basic anion exchange resin SAN (both manufactured by Mitsubishi Chemical Industries, Ltd.) were used as after polishers in the make-up water treatment system for secondary cooling water in a pressurized water nuclear power plant.
Pure water was produced using a mixed-bed pure water production apparatus in which the following products were mixed at a volume ratio of 1:1. At this time, the anion exchange resin is HCO ₃ type.
Mix with OH type and make the resin composition as follows.
Table 1 shows the results of H/OH/HCO ₃ type operation. Cation exchange resin composition: Na type 0.2%, balance H type Anion exchange resin composition: Cl type 0.2% HCO ₃ type 40%,
60% or 80%, remainder OH type

[Table] In the case of 40% HCO type ₃ , the pH was 6.5 and the conductivity was 0.06 μS/cm up to 17,000 B.V. at the initial stage of water sampling. HCO type ₃
In the case of 80%, the conductivity is
It was 1.0μS/cm. Comparative Example 1 Table 2 shows the results of H/OH type operation in Example 1 with the resin composition as follows. Cation exchange resin composition: Na type 0.2%, balance H type Anion exchange resin composition: Cl type 5%, balance OH type

[Table] Before the HCO ₃ break, the Na/Cl molar ratio was within the standard value range, but after that it was out of range and water could not be sampled. Comparative Example 2 In Comparative Example 1, in order to enable water sampling after the HCO ₃ break, the resin composition was changed to the following and H/
Table 3 shows the results of water sampling after HCO ₃ break during OH type operation. Cation exchange resin composition: Na type 0.2%, balance H type Anion exchange resin composition: Cl type 0.2%, balance OH type

[Table] From the above results, in Comparative Example 1, the amount of water sampled before _HCO3 saturation when the treated water quality is within the standard value range is
46,800 B.V., and in Comparative Example 2, it is outside the corresponding standard value of 46,800 B.V. before the HCO ₃ break. On the other hand, in all cases in the examples, the quality of the treated water was within the standard values from the beginning, and the amount of water sampled was six times that of the comparative example, indicating that high quality of the treated water was maintained over a long period of time. You can see what you can get.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing the cooling water system of a pressurized water nuclear power plant. 1...Nuclear reactor, 2...Steam generator, 4...Condenser, 7
... condensate desalination device, 8 ... pure water production device with polisher, 10 ... pure water storage tank, 11 ... after polisher, 12 ... deaerator.

Claims (1)

[Scope of Claims] 1. A pure water production device for treatment of make-up water in a nuclear power plant comprising a mixed bed of a strongly acidic cation exchange resin and a strongly basic anion exchange resin, wherein the entire amount of the strongly acidic cation exchange resin is The strongly basic anion exchange resin contains only 0.2 equivalent% or less of the Na form compared to the total weight of the H-form, and contains 40 to 80 equivalent% of the HCO ₃ form. A pure water production device characterized in that the remainder is of OH type. 2. The pure water production apparatus according to claim 1, wherein the HCO ₃ type anion exchange resin is about 60 equivalent %. 3. The pure water according to claim 1 or 2, wherein the pure water production device is used as an after polisher installed in a make-up water treatment system for secondary cooling water of a pressurized water nuclear power plant. Manufacturing equipment.