JPH07128323A - Method for measuring and controlling organic impurities - Google Patents

Abstract

PURPOSE:To prevent impurities from being mixed by decomposing organic impurities into organic carbon and inorganic ions, measuring the concentrations thereof simultaneously, and then estimating the type of impurities based on the measurements. CONSTITUTION:A sample containing impurities eluded from an anion-exchange resin and a cation-exchange resin are introduced to an organic compound decomposing section where the impurities are decomposed into organic carbon and other decomposition products. In this regard, wet oxidation or ultraviolet irradiation is employed and one kind of hydrogen peroxide, permanganate, chromate, or a combination thereof is selected as an oxidizing agent. The impurities eluted from the ion exchange resin produce ions of sulfuric, nitric, and nitrous and carbon dioxide. The carbon dioxide is purged with nitrogen, for example, and separated and then the concentration of organic carbon is measured by an infrared analyzer. Subsequently, inorganic ion impurities are concentrated from the remaining sample liquid and classified through elution before being identified by ion chromatography. The type of impurity is estimated based on the ratio between the organic carbon concentration and the inorganic ion impurities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring and managing organic impurities in ultrapure water used as cooling water for nuclear power plants or cleaning water for semiconductor factories that manufacture LSI.

[0002]

2. Description of the Related Art A large amount of ultrapure water is manufactured and used in a nuclear power plant and a semiconductor factory for manufacturing LSI. In nuclear power plants, operation control is performed to keep the impurity concentration in the cooling water as low as possible in order to protect the reactor materials from corrosion phenomena. On the other hand, in semiconductor factories, VLSI
There is a need to maintain the purity of the wash water in order to increase the reliability of Water quality control of equipment that uses these ultrapure water is not only to confirm that the cleanliness of water is maintained, but also to investigate the source of contamination even when a trace amount of impurities is mixed, and It is an important role to promptly take appropriate measures to prevent.

FIG. 1 shows a plant configuration of a boiling water nuclear power plant. The steam generated by the combustion of the nuclear fuel loaded in the reactor 1 is guided to the high-pressure turbine 3 and the low-pressure turbine 4 through the main steam pipe 2 to perform work. The steam after the work is re-condensed in the condenser 5, passes through the condensate pipe 6, the condensate pump 7, the condensate filtering device 8, the condensate demineralizer 9, and the condensate booster pump 10 to supply water. Be led to. The condensed water is purified by the condensate filtering device 8 and the condensate demineralizer 9 using the ion exchange resin. Further, the cooling water passes through the water supply pipe 11 and the water supply pump 12 in the water supply system, is heated by the water supply heater 13, and then returns to the reactor 1 again. On the other hand, the reactor water circulates in two series of recirculation systems, which are composed of the recirculation pump 14 and the recirculation system pipe 15. Further, a part of the reactor water is guided to the reactor cleaning equipment 18 through the reactor cleaning system pump 16 and the reactor cleaning system piping 17 and purified.
Then, it joins the water supply system pipe 11 and returns to the reactor 1. During that time, since the reactor decontamination equipment filter desalination device 18 uses the powder ion exchange resin, it is necessary to cool the reactor water to 60 ° C. or below. There is. On the other hand, the cooling water of the plant is stored in the condensate storage tank 20 and supplied to the condenser 5 and the reactor 1. The condensate storage tank 20 collects the supply water 21 obtained by filtering and desalting industrial water and the cooling water in the plant,
Recovered water 22 from the waste treatment system to be purified is supplied.

Impurities flowing in from the feed water are boiled and concentrated in the reactor, but a part of the reactor water is purified by a filter desalting device of the reactor cleaning system to keep the reactor water clean. Be drunk On the other hand, organic impurities are mainly due to the supply water from the condensate storage water, or the deterioration of the ion exchange resin used in the organic solvent or condensate desalination equipment or reactor purification equipment used during the periodic inspection work. It may flow into the reactor.

However, since various chemical species of organic impurities are assumed depending on the generation source and the organic impurities have the property of being easily decomposed by heat, radiation, etc. and changing their chemical forms, individual impurities should be directly measured. Is difficult. Therefore, under the present circumstances, organic carbon, which is an organic impurity, is decomposed into carbon dioxide, and the organic carbon concentration (TOC; Total Organic)
(Indicated as Carbon) is used as an index of the concentration of organic impurities. (For example, Tsutomu Sakamoto, Chemical Technical Journal MOL, January 1988, 73, (1987); JP-A-60-159642.
No .; JP-A-3-21866).

However, when the TOC concentration becomes higher than the control value or the normal value, the source of the generation is investigated, and when the organic impurities flow into the reactor and decompose, the water quality of the reactor water changes (conductivity). , PH) must be evaluated. However, the organic impurity organic carbon (TOC)
It is difficult to evaluate the change in water quality after decomposition of organic substances and organic impurities based on the information of concentration alone. Further, JP-A 1-219558 and JP-A 3-10
As seen in Japanese Patent No. 158, there has been devised a measuring device for thermally decomposing or ultraviolet decomposing organic impurities and thereafter measuring the concentration of inorganic ions as decomposition products. When measuring organic impurities using these analyzers, changes in water quality after decomposition of organic impurities can be evaluated. However, since there is insufficient information on the concentration of organic carbon in organic impurities, it is difficult to evaluate the type of organic impurities, and water quality management that considers the origin of the source is not sufficient.

[0007]

In a nuclear power plant, a semiconductor plant or the like which uses ultrapure water, organic impurities in pure water have been measured and managed. However, most of organic impurities are not ion-dissociated and cannot be detected by a permanent conductivity meter or pH meter. Furthermore, even when systematic water is analyzed using a TOC meter, changes in water quality when the measured organic impurities flow into the reactor and decomposed cannot be estimated. This is because when organic impurities flow into the reactor and decompose, the measured organic carbon becomes carbon dioxide (CO ₂ ) and moves to the turbine system together with the steam, and is not dissolved in the reactor water.

Sulfuric acid generated from sulfur contained in organic impurities is a chemical species of impurities that actually affect the changes in the electrical conductivity and pH of the reactor water and accelerate the corrosion of metallic materials such as reactor internals. This is because it is an inorganic ion such as an ion (SO ₄ ²⁻ ), a nitrate ion (NO ₃ ⁻ ) generated from nitrogen, a nitrite ion (NO ₂ ⁻ ), or a chlorine ion (Cl ⁻ ) generated from chlorine. If the concentrations of these inorganic ions can be detected in advance in the sample water near the source or upstream of the reactor, it becomes possible to predict the water quality change when the water flows into the reactor. On the other hand, it is necessary to reduce the inflow of organic impurities into the reactor as much as possible, and if contamination with system water is confirmed, promptly identify the contamination source and take appropriate measures to prevent contamination. Is required.

For this reason, it is difficult to estimate the molecular weight or the type of the organic impurity only by the concentration of the organic impurity or the concentration of the decomposition product of the organic impurity which is currently measured. It is difficult to estimate the generation source of organic impurities such as ion exchange resin, organic solvent or lubricating oil. Furthermore, although the change in water quality after decomposition can be estimated by measuring only inorganic ions after decomposing organic impurities, the amount of information is insufficient for estimating the type of organic impurities (source of mixing organic impurities).

As described above, the organic impurities can be measured by simultaneously measuring the concentration of organic carbon and the concentration of inorganic impurities produced when the organic impurities are decomposed, and estimating the type of the organic impurities and the water quality change when the organic impurities are decomposed. And the management method is important.

[0011]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made a method of decomposing organic impurities into organic carbon and inorganic ions, and then measuring their concentrations in the same manner. We devised a management method to evaluate the water quality change after impurity decomposition.

The structure of the method for measuring organic impurities of the present invention is shown in FIG. FIG. 2 shows an example of organic impurities eluted from an anion exchange resin and a cation exchange resin as an example of organic impurities, and the measurement method will be described.

A sample containing organic impurities eluted from the anion exchange resin and the cation exchange resin is introduced into an organic substance decomposition section to decompose the organic impurities into organic carbon (TOC) and other decomposition products (inorganic ion impurities). As a method for decomposing the organic impurities, a wet oxidation method used for measuring TOC or an ultraviolet irradiation method can be applied. However, the oxidant peroxodisulfate used to accelerate the decomposition of organic impurities used in the conventional organic carbon measuring apparatus produces sulfate ions (SO ₄ ²⁻ ) after decomposition. Sulfate ion (SO
₄ ²⁻ ) can also be assumed as a decomposition product of an organic impurity that is an eluate from a cation resin, and cannot be distinguished when measuring inorganic ions described later. Therefore, the oxidant is sulfate ion (S
O ₄ ^2-), nitrate ion (NO ₃ ^-), nitrite (NO
₂ ^-), chloride ion (Cl - becomes exclusive), etc., hydrogen peroxide, is necessary to select one or two or more combinations of permanganate or chromate ^-) and fluorine (F . By the decomposition of the organic impurities mentioned above,
The eluate from the ion exchange resin shown in FIG. 2 produces sulfate ions (SO ₄ ²⁻ ), nitrate ions (NO ₃ ⁻ ), nitrite ions (NO ₂ ⁻ ), and carbon dioxide. As the next step, carbon dioxide in the decomposition product is degassed with nitrogen gas or argon gas and separated, and then the TOC concentration is measured with a non-dispersive infrared analyzer.

Further, the sample liquid from which carbon dioxide has been separated is introduced into a column filled with an ion exchange resin, and after the inorganic ion impurities are concentrated, the ions to be detected by the change in conductivity after elution and separation according to the type of inorganic ion impurities by the eluent. Inorganic ion impurities are identified using the measurement principle of the chromatographic method.

According to the above method, the TOC concentration and the inorganic ion impurities after decomposition can be measured simultaneously. From these, it is possible to estimate the chemical species and molecular weight of the organic impurities present in the sample from the TOC concentration and the ratio of inorganic ionic impurities.

Specific chemical species of organic impurities and a method for estimating molecular weight are shown in Table 1 by taking an organic substance containing carbon, oxygen, sulfur and nitrogen as an example.

[0017]

[Table 1]

From the molecular structure of the organic substances shown in Table 1, when these organic substances are divided into organic carbon and inorganic ion impurities and measured, the ratio of carbon (C), nitrogen (N) and sulfur (S) shown in the molecular formula Measured at. With this idea, it is possible to extract a compound having the closest atomic number ratio among the organic impurities listed in advance when unknown organic impurities are measured. It is important to prioritize extraction of organic impurities listed in advance, such as eluates from ion-exchange resins, rust preventives, and lubricating oils, which can be assumed as sources of organic impurities in the plant. Note that the possibility of the above estimation is low when two or more types of organic impurities are mixed. However, the amount of information is larger than the conventional measurement result of only TOC or inorganic impurities, and the possibility of identifying the source becomes extremely high when combined with the priority of the source.

Further, from the measurement result of the inorganic ion concentration, it is possible to evaluate the ion concentration when the system water that has been temporarily measured flows into the reactor or the like and is decomposed. Therefore, the range of increase in conductivity or the range of change in pH can be estimated. It will be possible. The water quality of equipment that uses ultrapure water is monitored by a pH meter and a conductivity meter that allow continuous measurement. Therefore, it is necessary to convert the change in water quality due to the mixing of organic impurities into the values of pH and conductivity. The estimated values of conductivity and pH measured at 25 ° C. can be estimated by a relational expression using the inorganic ion concentration and the respective limit ionic conductivity shown in the following formula.

[Estimation formula of pH]

[0021]

[Equation 1]

[Electrical conductivity estimation formula]

[0023]

[Equation 2]

[0024]

[Operation] By adopting this method for measuring and controlling organic impurities in a plant using pure water, it becomes possible to identify the source of organic impurities and to prevent contamination quickly, and to improve the inorganic impurities after decomposition of organic impurities. It is possible to predict a change in conductivity, a change in pH, or the like that is affected by the formation of ionic impurities.

As a result, the reliability of organic impurity concentration management in a plant using pure water can be improved.

[0026]

EXAMPLES Examples of the present invention will be shown below.

FIG. 3 shows a flow chart of an embodiment of a method for measuring organic impurities. At the beginning of the measuring method, the sample water to be measured is sampled at 23. In the next 24, organic impurities in the sample water are decomposed into organic carbon and inorganic ion impurities by a wet oxidation method or an ultraviolet decomposition method. In step 25, carbon dioxide, which is a product of organic carbon, is separated from the decomposed mixture of organic carbon and inorganic ion impurities using an inert gas such as nitrogen gas or argon gas. The separated carbon dioxide is quantified with a non-dispersive infrared spectrometer. On the other hand, the inorganic ionic impurities are quantified in step 27 for each ionic impurity by the ion chromatography method.

Information on the organic carbon concentration 26 and the inorganic ion concentration 27 measured by the above method is led to a computer having a program for calculation processing according to the flow shown in FIG. Next, the organic carbon and inorganic ion concentrations are converted into the respective numbers of atoms in steps shown in 30 (for example, S, N, C
l, F, etc.). Next, the ratio of the number of each atom is calculated in 31 steps (for example, S / C, N / C, Cl / C, F /
C, Cl / S, S / N, etc.). The atomic number ratio of each of these is made to correspond to the combination information 33 of the number of atoms of the organic compound which can be assumed to be generated or mixed in the plant in 32 steps in advance, and the organic compounds having a close atomic number ratio are listed. Up. This facilitates estimation of what organic impurities coexist in the sample water.
Next, the changes in pH and conductivity that occur when the organic impurities are decomposed are calculated in steps 34 and 35 using Equations 1 and 2 shown before the inorganic ion concentration data. The information from the organic impurities measured and calculated according to the flow is finally divided into respective items and output in step 36.

FIG. 4 shows an embodiment relating to an organic impurity measuring apparatus for carrying out a method of wet-decomposing organic impurities. The sample water is led to the organic impurity monitor through a sample collection line 38 branched from a system pipe 37 requiring measurement. Considering that it is possible to prevent contamination of carbon dioxide gas in the atmosphere and contamination from the sampling container, it is preferable to sample the sample water rather than offline sampling. Solid impurities in the sample water are separated by the filter 39. For clogging of the filter, the differential pressure of the filter is monitored by the pressure gauge 40, and when the differential pressure of the filter becomes high, the filter is replaced or backwashed to maintain the operating pressure within the allowable operating pressure. An oxidant is added to the sample water from which the solid content is removed via an oxidant storage tank 41 and an injection pump 42 in order to assist wet decomposition. After that, in order to remove the inorganic carbon, it is led to the deaerator 43, and the inorganic carbon such as carbon dioxide gas is degassed and removed by supplying the inert gas such as nitrogen gas or argon gas from the gas cylinder 44. The sample water excluding the inorganic carbon is introduced into an organic substance decomposer 45 capable of being decomposed by heating to about 200 ° C. and decomposed into organic carbon and inorganic ions, and then cooled to room temperature through a cooler 46. The sample water containing the organic carbon and the inorganic ions is introduced into the organic carbon separator 47, and the inorganic carbon such as carbon dioxide gas is degassed and separated with an inert gas such as nitrogen gas or argon gas to obtain a non-dispersive infrared analyzer 48. To measure the organic carbon concentration.

On the other hand, the sample water from which organic carbon has been removed is introduced into an ion chromatographic analyzer. In an ion chromatographic analyzer, sample water is passed through a concentration column 49 filled with an ion exchange resin to concentrate inorganic ions in the ion exchange resin. afterwards,
The switching valve 50 is switched, and the eluent is passed through the concentration column from the eluent tank 51 via the pump 52. As a result, the inorganic ion impurities concentrated in the ion exchange resin are separated and eluted because the affinity with the ion exchange resin differs depending on the type of impurities. Since the elution time delay due to the type of inorganic ion impurities has already been confirmed, the impurities can be identified by the time delay from the elution start time to the detection. Further, the concentration of the separated impurities is measured by the conductivity meter 54 after removing the ions by the suppressor 53 downstream of the concentration column.
Detected in. Conversion from the measured conductivity value to the impurity concentration is performed using a calibration curve using known impurities. Further, the measurement results of the organic carbon concentration and the inorganic impurities may be sent to the respective output devices 48 and 55, but they can be rationalized by combining them into one output device.

FIG. 5 shows an embodiment in the case of decomposing organic carbon by using ultraviolet rays. The system configuration is almost the same as the configuration in which the organic impurities are decomposed by the wet decomposition method shown in FIG. 4, and the sample water after degassing inorganic carbon is introduced into the ultraviolet decomposer 56 to decompose the organic impurities. The object can be achieved by adopting a configuration in which the organic carbon and inorganic ion impurities are measured thereafter.

[0032]

By using the method for measuring and controlling organic impurities according to the present invention in a plant that uses pure water, it is possible to estimate the type of organic impurities, identify the source of organic impurities, and rapidly mix them. Preventive measures can be taken. In addition, when information on water quality changes after decomposition of organic impurities is required as in water quality management of nuclear power plants, it is possible to estimate water quality changes due to decomposition products by this method for measuring organic impurities. Become.

The fact that the above measurement and control can be performed on organic impurities can improve the reliability of water quality control as compared to the water quality control of only organic impurities or decomposed inorganic impurities.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a system configuration of a boiling water nuclear power plant and a mixing route of organic impurities.

FIG. 2 is an explanatory diagram showing a configuration of an organic impurity measuring method.

FIG. 3 is an explanatory diagram showing a method for measuring organic impurities and a method for estimating organic impurities based on the measurement results and a method for estimating changes in pH and conductivity after decomposition.

FIG. 4 is an explanatory diagram showing an example of an organic impurity monitor that decomposes and measures organic impurities by a wet oxidation method.

FIG. 5 is an explanatory diagram showing an embodiment of an organic impurity monitor that decomposes and measures organic impurities by ultraviolet rays.

[Explanation of symbols]

1 ... Reactor, 8 ... Condensate filter, 9 ... Condensate demineralizer, 18 ...
Reactor purification system filter desalting machine, 20 ... Condensate storage tank, 43
... inorganic carbon deaerator, 45 ... organic matter decomposer, 47 ... organic carbon separator, 49 ... inorganic ion concentration column, 54 ... conductivity meter, 56 ... ultraviolet decomposer.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G21D 3/08 GDB G 9117-2G

Claims (2)

[Claims] 1. In a water quality analysis method for equipment using water of high cleanliness, after measuring minute amounts of mixed organic impurities into organic carbon and inorganic ions, the organic carbon concentration and inorganic ion concentration are simultaneously measured and measured. A method for measuring and controlling organic impurities, which comprises estimating the type of organic impurities from the concentration ratio of the organic carbon and the inorganic ion impurities or the ratio of the number of atoms. 2. The method for measuring and controlling organic impurities according to claim 1, which estimates the conductivity and hydrogen ion concentration when the organic impurities are decomposed from the measured inorganic ion impurity concentration.