JPS6345595A - Method and device for purifying reactor cooling water - Google Patents

Abstract

(57) [Abstract] 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 reactor cooling water purification method and apparatus for purifying reactor cooling water in a nuclear power plant.

Particularly related to purification methods and devices using ion exchange resins that can reduce radiation exposure for workers at nuclear power plants and facilitate waste disposal, especially those equipped with filtration and desalination equipment that uses powdered ion exchange resins. It is.

[Background of the invention]

In recent years, with the increase in the number of operating nuclear power plants, there is a strong desire to reduce the amount of radiation exposure of workers during normal operation and periodic inspections. For this reason, the radioactive substances in the yX ion water, that is, the fine particles mainly composed of iron oxide called cladding (
(particle size 3 μma degree) and “Co”+・2111 Fe Z
It is necessary to efficiently remove radioactive metal ions such as +.

Conventionally, in boiling water reactors, the cooling water that drives the turbine and is recovered by the condenser is passed through a filtration demineralizer pre-coated with powdered ion exchange resin, and granular cation exchange resin and anion exchange. The water is purified by a conventional desalter using a mixed bed of resin and then supplied to the reactor. The powdered ion exchange resin used in the filtration demineralizer is obtained by pulverizing a cation exchange resin and an anion exchange resin.

Usually, the filtration demineralizer and the demineralizer are collectively referred to as a reactor cooling water purification system.

The reason why reactor cooling water purification systems are so effective in reducing radiation exposure for workers will be explained in detail below.

The main cause of exposure is radioactive crud and radioactive “Go”.
This is because "Go" adheres to the pipes and increases the piping line visibility. Also, the cause of the generation of radioactive crud and "Go" is non-radioactive substances leached into the cooling water from the condenser and pipes. This is because iron and cobalt become radioactive when exposed to neutron irradiation inside a nuclear reactor.

Therefore, by removing iron and cobalt (including both cladding and ions) from cooling water, whether radioactive or non-radioactive, the amount of exposure can be reduced. For this reason, a reactor cooling water purification system that combines a filtration desalter and a desalter has conventionally been used. In this equipment, the filtration demineralizer installed upstream simultaneously removes radioactive crud and metal ions from the cooling water, and the demineralizer removes the remaining metal ions that were not completely removed by the filtration demineralizer. I am trying to remove it. Furthermore, in the conventional example, the cation exchange resin is a benzenesulfonic acid-based resin, and the anion exchange resin is a quaternary ammonium-based resin as a powdered or granular ion exchange resin in the filtration demineralizer and the demineralizer. . The molecular structure of each is shown below.

(a) Cation exchange resin (benzenesulfonic acid resin) 0a- (b) Anion exchange resin (quaternary ammonium resin) C
Ha CHa Among the many types of ion exchange resins, benzenesulfonic acid resins are used as cation exchange resins, and quaternary ammonium resins are used as anion exchange resins because they have excellent heat resistance and radiation resistance. , and benzenesulfonic acid resins are strongly acidic, and quaternary ammonium resins are strongly basic, so neutral salts such as NaCQ are present in the cooling water (this occurs when seawater leaks from the condenser). This is because it has a high ability to remove even if it is removed.

As mentioned above, by using a cooling water purification system (combined use of a filtration demineralizer and a demineralizer), the amount of radiation exposure of workers within a nuclear power plant can be significantly reduced. However, in recent years, there has been a desire to further reduce the amount of radiation exposure.

Conventionally, according to Japanese Patent Application Laid-Open No. 58-761.46, a weakly acidic cation exchange resin having a carboxyl group as an ion exchange group was used as a fuel for a weakly acidic cation exchange resin in which an atomic radioactive metal ion was bonded. It was discovered that the non-radioactive metal ions that adhered to the rod became radioactive and were eluted into the cooling water again, which then adhered to the pipes and led to an increase in the radiation dose rate. Therefore, the inventors of the present invention
As a result of various studies to clarify the cause, the following points were clarified. That is, among weakly acidic cation exchange resins, those in which the ion exchange group is directly bonded to the benzene ring exhibit the same phenomenon as the sulfonic acid type resins because the bonding energy of the ion exchange group is relatively large. It became clear. As a result of further investigation, it was found that the ion exchange group is a weakly acidic cation with a binding energy of 300 KJ/mol or less.

[Object of the Invention] An object of the present invention is to provide a purification method and apparatus using an ion exchange resin that can reduce the amount of radiation exposure for workers at a nuclear power plant and facilitate waste disposal.

[Summary of the invention]

In the method for purifying nuclear reactor cooling water of the present invention, the bond energy of the ion exchange group bonded to the main chain of the polymer containing an aromatic ring is 3.
This is a method for purifying nuclear reactor cooling water, which is characterized by bringing reactor cooling water into contact with a cation exchange resin of 00 KJ/mol or less to capture and purify crud or cations in the cooling water. By the way, the inventors have discovered that by improving the reactor cooling water purification system currently in use, it is possible to further reduce the amount of radiation exposure to workers. In other words, if a powdered ion exchange resin is used in a filtration demineralizer,
If a mixture of exchange resin and anion exchange resin with a large particle size distribution (about 5 μm or less) is used in a filtration demineralizer, if the particle size is as small as 5 μm or less, some of the particles will be used in the filtration demineralizer. leaks and gets mixed into the cooling water. It was discovered that the leaked powdered ion-exchange resin was carried into the reactor as it was, increasing the amount of radiation exposure of working tools. A detailed explanation will be given below using FIGS. 3 and 4.

First, consider the case where there is no ion exchange resin leaked into the cooling water 3, and the cooling water contains only non-radioactive metal ions such as cobalt eluted from piping, etc., and this cooling water flows into the reactor. . A fuel rod 8 is loaded inside the nuclear reactor, and the surface of the fuel rod 8 is covered with an oxide film. Considering the charge state of the metal ions 7 that have flowed into the furnace and the surfaces of the fuel rods 8, the metal ions are naturally positively charged, and the surface potential of the fuel rods 8 is also positive. The reason for this is that, as is generally known, the zeta potential of the oxide film becomes positive in water with a pH of 5 to 8.

In this state, since both the metal ions 7 and the surfaces of the fuel rods 8 are positively charged, the metal ions 7 hardly adhere to the surfaces of the fuel rods 8, as shown in FIG.

Next, consider the case where ion exchange resins (cation exchange resin 9 and anion exchange resin 10) leaked from the filtration demineralizer are mixed into the cooling water 3, as shown in FIG.
Cation exchange resin 9 is negative, anion exchange resin 1
0 is positively charged. Since the surface of the fuel rod 8 is positively charged, a portion of the negatively charged cation exchange resin 9 adheres to the surface of the fuel rod 8. Non-radioactive metal ions such as cobalt are adsorbed on the attached cation exchange resin 9. Further, since the cation exchange resin 9 does not normally adsorb metal ions in a saturated state, the metal ions 7 floating in the cooling water 3 will also be adsorbed. As described above, it has been found that when the cation exchange resin leaks into the cooling water, the amount of non-radioactive metal ions adhering to the surface of the fuel rod 8 increases. In other words, it was found that when the cation exchange resin leaks into the cooling water, the average residence time of non-radioactive metal ions in the reactor becomes longer.

Cobalt-59 (15IlGo) is a typical non-radioactive metal ion contained in the cooling water 3.
When this "Co" is irradiated with neutrons in the nuclear reactor 6, a part of it changes into radioactive cobalt-60 ("Go"). In this way, when the cation exchange resin 9 leaks into the cooling water 3, the residence time of Go and other substances in the reactor becomes longer, and as a result, the amount of radioactive metals such as Go produced increases. .

This resulted in increased radiation exposure for workers.

As explained above, when the cation exchange resin leaks from the filtration demineralizer, the amount of radioactive metals generated within the reactor increases, and some of the radioactive metals are peeled off from the fuel rods 8. and elute again into cooling water. As a result, the radioactivity concentration of the cooling water also increases. Some of the radioactive metal ions in the cooling water adhere to the pipes, increasing the dose rate of the pipes.

Furthermore, the amount of radioactive metal ions adhering to the pipe increases due to the presence of the cation exchange resin for the same reason as explained in FIGS. 3 and 4.

As described above, when the cation exchange resin leaks into the cooling water, the amount of radioactive metal produced increases, and the amount of radioactive metal attached to the pipes also increases. As a result, the amount of radiation exposure for workers will increase.

In addition, since the anion exchange resin 10 is positively charged, it is difficult to adhere to the surface of the fuel rod or piping (both surfaces are positively charged), and is not as harmful as the cation exchange resin.

The inventors of the present invention obtained the knowledge of the present invention through the following experiments. That is, using the experimental apparatus shown in FIG. Water was passed to. In addition, about 1 ppb of 80co is dissolved in pure water 11, and after one water passage,
As a result of measuring "Cot" attached to the pipe 14, it was found that when about 0.1 ppm of cation exchange resin is mixed into pure water, 8.
It was found that the amount of 0 CO adhering to piping increased by 1.5 to 2 times. Further, when an anion exchange resin was mixed, no increase in the amount of 5OGo attached to the piping was observed.

The above results show that it is effective to prevent leakage of cation exchange resin into cooling water in order to reduce radiation exposure to workers. Ion exchange resins are used in both the filtration demineralizer and the demineralizer that make up the reactor cooling water purification system, and both use a mixture of cation exchange resin and anion exchange resin. However, since demineralizers use granular ion exchange resin with a large particle size of approximately 500 μm and 8 degrees, there is almost no leakage of ion exchange resin into the cooling water.On the other hand, in filtration demineralizers The average particle size of the ion exchange resin is small, about 8 μm, and the particle size distribution is widely distributed, from several μm to about 100 μm, so the ion exchange resin with a small particle size easily leaks into the cooling water. Therefore, it is necessary to take measures to prevent leakage of the cation exchange resin in the filtration demineralizer.

As a measure to prevent leakage, a method of using only powdered ion exchange resins having a particle size of a certain size or more (for example, 5 μm or more) can be considered. Although this method is effective in preventing leakage, it is disadvantageous in terms of cost.

In other words, since powdered ion exchange resin is manufactured by pulverizing a single particle of ion exchange resin, it is inevitable that particles with a particle size of about 1 μm will be mixed in, so it is desirable to use only those with a certain particle size or more. In some cases, a step is required to sift out particles with a certain particle size or less from the produced powdered ion exchange resin.

In addition, since the particle size to be sieved is as small as a few μm, this process becomes extremely complicated and increases the cost.

Therefore, the present inventors investigated the existence of a cation exchange resin that would not increase the radiation exposure of workers even if the cation exchange resin leaked into cooling water. As a result, the ion exchange groups in the cation exchange resin.

We have found that it is effective to use a cation exchange resin that is bonded to an element other than carbon that constitutes the benzene ring.

This will be explained in detail below.

As mentioned above, when the cation exchange resin leaks into the cooling water 3, the cation exchange resin adheres to the surface of the fuel rod,
Along with this, the average residence time of non-radioactive metal ions (159Go, etc.) in the reactor becomes longer, and the amount of radioactive metal produced increases. Conventionally, benzenesulfonic acid resins in which an ion exchange group (SO3-) is directly bonded to a benzene ring have been used as cation exchange resins, but this resin has heat resistance and
It was found that it has high radiation resistance and is difficult to decompose even when used in a nuclear reactor system.

The reason why the cation exchange resin tends to adhere to the fuel rods 8 is because the cation exchange resin 9 is negatively charged, but the reason why the cation exchange resin is negatively charged is as follows. . In other words, the polymer base (a copolymer of styrene and divinylbenzene) is electrically neutral, but
This is because since the ion exchange group has electrically negative properties, the cation exchange resin as a whole also becomes negative.

By the way, when cation exchange resins enter a nuclear reactor, they are exposed to high temperatures and high radiation, making them easy to decompose.
The order in which a cation exchange resin decomposes is from the ion exchange group part with the smallest chemical bonding energy, and is expressed in the chemical formula as follows.

Assuming that the cation exchange resin decomposes as shown in the above equation, it becomes an electrically neutral polymer base and a negatively charged sulfite ion (SOaz-), of which the sulfite ion is a soluble Immediately move the wood into the cooled wood,
The remaining polymer base becomes electrically neutral, so the fuel rod 8
becomes difficult to adhere to the surface. Even if they adhere, they do not have ion exchange ability, so non-radiative metal ions in the cooling water will not remain on the surface of the fuel rods for a long period of time.

In addition, the cation exchange resin after the ion exchange group is decomposed is electrically neutral, making it difficult to adhere to piping, and as a result, it may also promote the adhesion of radioactive metals (80C0, etc.) to piping. It disappears.

The case where the ion exchange group decomposes from the cation exchange resin has been explained above, but conventional cation exchange resins have
Because a benzenesulfonic acid resin with high radiation resistance was used, the ion exchange groups from the cation exchange resin were difficult to decompose, making it impossible to achieve the above-mentioned effect of reducing radiation exposure for workers.
Therefore, if a cation exchange resin that is easily decomposed thermally is used.

It is possible to achieve the effect of reducing radiation exposure for workers.

Next, a cation exchange resin that is easily decomposed thermally will be explained.

Cation exchange resins can be roughly divided into the following two types depending on the element to which the ion exchange group is bonded. One type is one in which an ion exchange group is bonded to a carbon atom constituting a benzene ring, and this is hereinafter referred to as a benzene ring type. The second type is one in which the ion exchange group is bonded to an element other than the carbon atom constituting the benzene ring, and is hereinafter referred to as a linear type.
The table is.

Examples of benzene ring type and linear type cation exchange resins are shown.

Using seven types of cation exchange resins shown in Table 1, thermally weak resins were experimentally investigated. The experimental method involved using seven types of cation exchange resins at 280°C.

The sample was immersed in high-temperature water at 70 atm, and the change in ion exchange capacity was determined to examine how the ion exchange group decomposes over time. Figure 6 shows the experimental results. In the figure, the horizontal axis shows the immersion time in high-temperature water, and the vertical axis shows the change in ion exchange capacity in logarithm -. From this result, the cation exchange resins that are easily decomposed thermally are ■, O, OG.
From Table 1, it was found that linear ion exchange resins are easily thermally decomposed. The reason why the linear type is easily thermally decomposed is thought to be due to the bonding energy between the ion exchange group and the polymer substrate (see Table 1).

In other words, the ion exchange group bonded to the carbon of the benzene ring (
Benzene ring type) has a large bond energy and is difficult to decompose thermally.On the other hand, an ion exchange group (linear type) bonded to an element other than carbon in the benzene ring has a small bond energy, so It is thought that it becomes easier to decompose thermally.

Figure 7 shows the time t□/1+1 for which the ion exchange capacity becomes 1/10 for each resin from the graph of changes in ion exchange capacity shown in Figure 6. T18 on the axis. The horizontal axis shows the binding energy of the ion exchange group in the corresponding ion exchange resin. From this figure, it can be seen that when the binding energy is 300 KJ/mol or less, ti/io is 1 hour or less, and it is easy to thermally decompose. In particular, linear resins usually have a bond energy of 300 KJ/+mo12 or less and are therefore easily decomposed, and even benzene ring type resins can be easily decomposed if their bond energy is 300 KJ/rioQ or less. I understand that.

Based on the above, in order to further reduce the radiation exposure per worker, it is effective to use a linear type or one with low binding energy of ion exchange groups as the cation exchange resin used for filtration and desalination i4. . Although more than 100 types of cation exchange resins are known, the majority of those currently in use are benzene ring types, and there are only a few straight chain types, especially those used directly in reactor cooling water purification systems. There are no examples of using chain type cation exchange resins, but the following are examples of straight chain type cation exchange resins.

(1) Oxybenzyl sulfonic acid type: Type shown in Table 1 ■.

(2) Acrylic carboxylic acid type: Type shown in Table 1 ■.

(3) Methacrylic carboxylic acid type: The molecular structure of this type is as follows.

CH.

(4) Aromatic carboxylic acid type: The molecular structure of this type is as follows.

(5) What are called chelate resins: In addition to the types shown in Table 1, there are also those with the following molecular structures.

In the present invention, in the case of a cation exchange resin containing divinylbenzene as a molecular component, the amount to be copolymerized is 1 to 2.
0 wt%, especially 2 to 16 wt% is suitable.

Next, what kind of ion exchange resin is best to use for the filtration demineralizer 4 and demineralizer 5 shown in FIG. 1, which will be described in detail later, will be described in detail below.

Impurities contained in cooling water include fine particles such as cladding (hereinafter referred to as impurity a), and cations such as Go''÷, Fe''◆g M n ''10 (hereinafter referred to as impurity A) due to material corrosion. ), anions such as carbonate ions and silicate ions (hereinafter referred to as impurity C), and if seawater leaks from condenser 2, neutral salts such as NaCQ (hereinafter referred to as impurity d) are impurities. It exists as.

Conventionally, as mentioned above, a mixture of benzenesulfonic acid resin, which is a strongly acidic ion exchange resin, and quaternary ammonium resin, which is a strong basic ion exchange resin, is used in the filtration desalter. All of the impurities a = d could be removed by a filtration demineralizer, and the demineralizer was installed for supplementary purposes. On the other hand, in the present invention,
The desalter plays an important role. In other words, since linear cation exchange resins are generally weakly acidic ion exchange resins, they decompose the impurity d (neutral salt) (N a CQ → Na +
Therefore, if seawater leaks from the condenser 2, if a linear ion exchange resin is used as the cation exchange resin in the filtration demineralizer 4, the ability to adsorb ions is low. A salter will not be able to completely remove neutral salts.Therefore.

If there is a possibility of seawater leaking from condenser 2,
In the desalter 5, it is preferable to use a strongly acidic particulate ion exchange resin such as a benzenesulfonic acid resin and a strongly basic particulate ion exchange resin such as a quaternary ammonium resin.
Thereby, neutral salts can be completely removed in desalination Ja5.

In addition, in the above explanation, there is almost no mention of anion exchange resin among the powdered ion exchange resins used in the filtration demineralizer 4, but the anion exchange resin is used in the cooling water 3.
Even if leakage occurs, it will not result in an increase in the radiation exposure of workers, so you can use the same quaternary ammonium resin as in the past.

There is no problem in using resins other than these. Examples of anion exchange resins other than those mentioned above include primary to tertiary amine type anion exchange resins, such as those shown below.

-CH-CH2-CH- CH2N (CH2) Conventionally, quaternary ammonium-based resins have been used as anion exchange resins for filtration demineralizers, but this quaternary ammonium-based resin has strong basicity. This is because since it is an ion exchange resin, if it is mixed with a strongly acidic benzenesulfonic acid resin, the removal rate of neutral salts in the filtration demineralizer will increase.However, in the present invention, the neutral salt removal rate will increase. Since the removal of (impurity d) is carried out in the demineralizer 5, the anion exchange resin used in the filtration demineralizer 4 does not need to be limited to quaternary anthenium resin.

As described below, in the filtration demineralizer 4 using powdered ion exchange resin, by using a cation exchange resin in which the ion exchange group is bonded to an element other than carbon constituting the benzene ring, It becomes possible to significantly reduce the amount of radiation exposure for workers.

According to the present invention, the above-mentioned configuration 4
．． - Therefore, the following effects can also be obtained.

When the powdered ion exchange resin pre-coated on the filtration demineralizer 4 is used for a long period of time (10 to 50),
The cladding in the cooling water 3 is trapped, causing clogging of the resin layer, increasing the pressure loss of the filtration layer. When the pressure loss reaches a certain value, the ion exchange resin is backwashed and only the ion exchange resin is replaced with a new one, but the used ion exchange resin becomes radioactive waste. Currently, about half of the radioactive waste generated from boiling water nuclear reactors is occupied by spent ion exchange resin (hereinafter referred to as waste resin) generated from this filter demineralizer 4. Japanese Unexamined Patent Application Publication No. 1983 (1983) as a means to reduce the volume of waste resin
A thermal decomposition method and an incineration method as disclosed in Japanese Patent No. 107300 have been developed. However, by using the ion exchange resin of the present invention, waste resin treatment by the above-mentioned thermal decomposition method, incineration method, etc. can be easily performed. The reason is
A case where a benzenesulfonic acid resin (Table 1) and an acrylic carboxylic acid resin (O in Table 1) are thermally decomposed will be compared and explained.

FIG. 8 is a graph showing thermogravimetric changes when a benzenesulfonic acid resin (curve ■) and an acrylic carboxylic acid resin (curve ■) are thermally decomposed in a nitrogen atmosphere. As is clear from this figure, benzenesulfonic acid resin has high heat resistance, so even if it is thermally decomposed at 500°C or higher, 50wt%
Some residue remains. On the other hand, acrylic carboxylic acid resin has low heat resistance, so when it is thermally decomposed at 450°C or higher, it can be decomposed by 95 wt% or more, leaving only a small amount of residue.The waste resin used in the present invention was thermally decomposed. This shows that the amount of waste can be significantly reduced.

In addition, as a result of investigating the thermal decomposition characteristics of other cation exchange resins based on the present invention, it was found that
When thermal decomposition is carried out, methacrylic carboxylic acid resin,
Aromatic carboxylic acid resin and chelate resin are 95 wt
% or more, even oxybenzyl sulfonic acid is 70wt
% decomposed.

All of the cation exchange resins used in the present invention are more easily thermally decomposed than benzenesulfonic acid resins.

The results are the same when incinerated in an oxygen-containing atmosphere. That is, conventional benzenesulfonic acid resins have high heat resistance and are difficult to incinerate, and some of the generated residue adheres to the furnace walls, shortening the life of the furnace material. This is because incineration is carried out at a temperature of 800° C. or higher, which tends to cause some of the ion exchange resin to melt and adhere to the furnace wall. Against this.

The cation exchange resin used in the present invention can be easily incinerated.

Furthermore, when conventionally used benzenesulfonic acid resins are thermally decomposed or incinerated, harmful gases such as Hz S and Sox are generated because the resin contains sulfur.

On the other hand, the acrylic carboxylic acid resin and aromatic carboxylic acid resin based on the present invention do not contain sulfur atoms, so even when they are thermally decomposed or incinerated, the Hz S
The gas treatment system can be simplified without generating SOx or SOx, and material corrosion caused by Hx, S, etc. can be prevented.

As described above, when the cation exchange resin according to the present invention is used in the filtration demineralizer 4, it is possible not only to reduce the amount of radiation exposure per worker, but also to facilitate the disposal of radioactive waste.

Note that as the granular cation exchange resin used in the demineralizer 5 is a benzenesulfonic acid resin as in the past, it does not have the effect of facilitating waste disposal; What is the amount of waste?

It is less than 1/10 of the amount of waste generated from the filtration demineralizer 4, so there is no problem. Also, the waste resin generated from the demineralizer 5 and the waste resin generated from the filtration demineralizer 4 are mixed. By processing (thermal decomposition, incineration, etc.), it is possible to alleviate the adverse effects during processing of the benzenesulfonic acid resin generated from the desalter 5.

In other words, SO generated from benzenesulfonic acid resin
Since the concentration of x and Hx S is relatively reduced by the mixing treatment, problems such as material corrosion are alleviated compared to when they are treated alone.

In this explanation, it has been explained that it is desirable for the powdered cation exchange resin used in the filtration demineralizer 4 to have an ion exchange group bonded to an element other than carbon constituting the benzene ring. It is unavoidable to use one in which a part of the ion exchange group is directly bonded to the carbon forming the benzene ring.

The preferred examples of the present invention described above are summarized as follows.

(]) A powdered cation exchange resin used in the filtration demineralizer of the reactor cooling water purification system, in which the ion exchange group is bonded to an element other than carbon that constitutes the benzene ring (linear type)
Use.

(2) The granular ion exchange resin used in the demineralizer of the reactor cooling water purification system is a mixture of benzenesulfonic acid resin as the cation exchange resin and quaternary ammonium resin as the anion exchange resin. use

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

Example 1 Figures 1 and 2 show a first example of the present invention.
FIG. 1 is a system diagram showing a cooling water purification system in a boiling water reactor, and FIG. 2 is a partially detailed cross-sectional view of a filtration desalination device used in the system.

The reactor cooling water 3 that drives the turbine 1 and is recovered by the condenser 2 is purified by the filtration demineralizer 4 and the demineralizer 5, and then passes through the feed water pump 15 and the feed water heater 16 into the reactor 6. return. The demineralizer 5 is loaded with the granular benzenesulfonic acid resin and quaternary ammonium resin mixed in a ratio of 2=1. Further, the filtration demineralizer 4 is pre-coated with powdered ion exchange resin. That is,
First, in the pre-coating tank 17, an acrylic carboxylic acid resin with an average particle size of about 30 μm as a powdered cation exchange resin (Table 1 ■) and a quaternary ammonium resin with a particle size of about 30 μm as a powdered anion exchange resin are added. The weight ratio is 2=1
In addition, a water-soluble polymer electrolyte (polyacrylic acid) was added.

A small amount (about 0.05 to 1 wt%) of polymerized maleic acid, etc.) is added, and the mixture is stirred using a stirrer 18. As a result, a floc in which the cation exchange resin 9 and the anion exchange resin 10 are mixed is formed. This floc is sent to the filtration demineralizer 4 via a valve 19 by a precoat pump 20. A filtration element 21 made of nylon or stainless steel is provided in the filtration demineralizer 4 as shown in the figure, and the flock 22 is precoated thereon.

As a result of operating a boiling water reactor equipped with a cooling water purification device as described above for one year and measuring the surface dose rate in various pipes, the dose rate in the recirculation pipe 23 was the highest, at 20 mR/h.
Met. Note that when a conventional cooling water purification device using a benzenesulfonic acid resin and a quaternary ammonium resin was used in the filtration demineralizer 4, the surface dose rate of the recirculation pipe 23 was 30 mR/h. . In addition, the reactor 6 was operated with various types of powdered ion exchange resin used in the filtration demineralizer 4, and the surface dose rate of the re-Wi ring pipe was measured, and the results shown in Table 2 were obtained. Ta.

Table 2 As is clear from Table 2, according to the present invention, the radiation exposure of workers can be reduced by 1/3 to 1/6 compared to the conventional method. By the way, the surface dose rate of the recirculation piping is 20m.
At R/h, the annual exposure from working tools is 60 to 100
It will be about Manrem.

Furthermore, it has been found that according to the present invention, the life of the powdered ion exchange resin used in the filtration demineralizer 4 can be extended. This will be explained below with reference to FIG. In the figure,
The broken line curve A is pre-coated by mixing acrylic carboxylic acid resin and quaternary ammonium resin at a ratio of 2=1.
It is a differential pressure increase curve when reactor cooling water 3 is purified,
A solid curve B is a differential pressure increase curve when a conventional powdered ion exchange resin (a mixture of a benzenesulfonic acid resin and a quaternary amine resin) is used. This figure shows that the rise of the differential pressure rise curve is slower in the present invention, and the life is approximately 1.5
You can see that it doubles.

Therefore, according to the present invention, the filtration life of the powdered ion exchange resin is extended, and the cost can be reduced.
Since the resin can be used for a long period of time, the amount of waste resin generated is reduced, which has the effect of reducing radioactive waste.

In addition, in the above explanation, the case where a combination of an acrylic carboxylic acid resin and a quaternary ammonium resin is used as the powdered ion exchange resin used in the filtration demineralizer 4 has been explained as an example, but other methods based on the present invention may also be used. Similar effects can be obtained by combining different types of ion exchange resins. That is, there are five types of powdered cation exchange resins such as oxybenzyl sulfonic acid resins, acrylic carboxylic acid resins, and methacrylic carboxylic acid resins, and five types of powdered anion exchange resins such as quaternary ammonium resins and tertiary amine resins. 4
We selected various types, combined them into arbitrary combinations, and experimentally determined their filtration lives. The results shown in Table 3 were obtained from the experiment. Third
In the table, the filtration life when using a conventional powdered ion exchange resin is assumed to be 1, and the filtration life in each combination according to the present invention is shown as a relative value.

Table 3 Fist filtration life: 1 for the conventional method.

As is clear from Table 3, in the present invention, the filtration life can be extended by 1.1 to 1.8 times no matter which combination is used.

As explained above, according to this example, not only can the radiation exposure of workers be reduced by 1/3 to 1/6 compared to conventional methods, but also the lifespan of the ion exchange resin in the filtration demineralizer can be reduced. Since it can be extended by about 1.5 times, costs and the amount of radioactive waste generated can also be reduced by about 1/3.

In addition, in the apparatus of the present invention, an experiment was conducted on the assumption that seawater leaked from the condenser 2 into the cooling water 3, but no trouble occurred. When seawater leaks from the condenser 2, the filtration demineralizer 4 in the conventional device can remove neutral salts such as NaCl2 from the reactor cooling water, but in the present invention, the filtration demineralizer 4 Since a weakly acidic cation exchange resin is used, neutral salts cannot be removed.

However, in this embodiment, since a strongly acidic benzenesulfonic acid resin and a strongly basic quaternary ammonium resin are used in the demineralizer 5, the neutral salts that could not be removed by the filtration demineralizer 4 are Since seawater can be completely removed by the desalination device 5, no problem will occur even if seawater leaks.

In this example, a cation exchange resin, an anion exchange resin, and the king of polymer electrolytes were mixed in the precoat tank 17, but surface treatment etc. If a polymer electrolyte is added in advance, it is sufficient to mix the cation exchange resin and the anion exchange resin in the precoat tank 17.

Example 2 The basic configuration of this example is the same as that of Example 1, but the ratio of powdered cation exchange resin and anion exchange resin used in the filtration demineralizer 4 was changed from that of the example described above. This is an example in which

In the first embodiment, according to the present invention, the filtration demineralizer 4
In this example, the ratio of powdered cation exchange resin to anion exchange resin was changed and changes in the life span were examined. The experimental method was the same as in the case of FIG. 9, and the lifespan was determined by experimentally examining the differential pressure increase curve. FIG. 10 is a diagram showing the experimental results, where the horizontal axis shows the resin ratio and the vertical axis shows the filtration life. The filtration life on the vertical axis is the powdery ion exchange resin (67 wt% for benzenesulfonic acid resin, 33 wt% for quaternary ammonium resin) in the filtration demineralizer in the conventional device.
The lifespan is expressed as a relative lifespan when the lifespan of the mixture (mixed at wt%) is set to 1. In the figure, the solid curve C is
In the case of a powdered ion exchange resin that is a combination of an acrylic carboxylic acid resin and a quaternary ammonium resin, the curve of the broken line indicates the case of a powdered ion exchange resin that is a combination of a methacrylic carboxylic acid resin and a tertiary amine resin. There is.

As is clear from Figure 10, in order to extend the filtration life, the proportion of cation exchange resin should be increased to 50wt% or more.
t% or less (anion exchange resin: 50wt% or less 10wt
% or more). The reason why the filtration life changes depending on the mixing ratio of the anionic and anionic ion exchange resins is considered to be as follows. In other words, the impurities contained in the cooling water 3 are overwhelmingly more cations such as Go"+ and Fe"+ than anions, and if the ratio of cation exchange resin and anion exchange resin is equalized, , the cation exchange resin adsorbs more ions than the anion exchange resin. If at least one of the anion and cation exchange resins adsorbs a large amount of ions, filtration performance is thought to decrease. Therefore, in order to extend the filtration life, it is better to increase the proportion of the cation exchange resin to 50 wt% or more. , Conventionally, the filtration desalination device 4 was considered to remove neutral salts such as NaCΩ when seawater leaks, and for this reason, cations (
The proportion of cation exchange resin could not be increased too much, since equal equivalents of the anion CCU'') and the anion CCU'''' had to be removed. However, in the present invention, the neutral salts are not removed by the filtration demineralizer 4 but are removed by the demineralizer 5, so the proportion of cation exchange resin in the filtration demineralizer 4 is considerably increased. No problem.

Furthermore, from Figure 10, the proportion of cation exchange resin is 90w.
It can be seen that the filtration life is also shortened when the concentration exceeds t%. This is because there is too little anion exchange resin to form a floc (an aggregate of cation exchange resin and anion exchange resin) that is optimal for filtration.

As explained above, it is desirable that the ratio of the powdered cation exchange resin and anion exchange resin is 50 to 90 wt%, preferably 60 to 85 wt%, and this can significantly extend the filtration life. becomes.

Embodiment 3 This embodiment is an embodiment in which the present invention is implemented in a cooling water purification system for a pressurized wooden nuclear reactor, and a system diagram thereof is shown in FIG. 11.

The cooling water 3 heated in the nuclear reactor 6 is transferred to the steam generator 24.1.
The reactor cooling water 3 is circulated to the reactor 6 via the secondary cooling water pump 25, and a portion of the reactor cooling water 3 is supplied to the filtration demineralizer 4 via the heat exchanger 26. In the filtration demineralizer 4, a cation exchange resin and an anion exchange resin having the following molecular structure were mixed at a ratio of 3:1 and used as a powdered ion exchange resin.

Conventionally, in pressurized wooden nuclear reactors, a hotbed type demineralizer using a single granular ion exchange resin was used instead of the filtration demineralizer 4, but it is possible to use a filtration demineralizer as in this example. As a result, the removal performance of crud in the cooling water 3 is greatly improved, and the radiation exposure of workers can be significantly reduced and the method can be applied to other systems. Conventionally, in boiling water reactors, part of the cooling water in the reactor recirculation system was purified using a filtration demineralizer. A mixture of quaternary amine resins was used.

However, even with this filtration demineralizer, some of the ion exchange resin may leak into the cooling water, potentially increasing radiation exposure for workers. Therefore, if the ion exchange resin based on the present invention is used in the filtration demineralizer of the reactor water purification system that purifies a portion of the cooling water in the recirculation system, even if the ion exchange resin leaks, the amount of radiation exposure to workers will be reduced. increase can be minimized.

Further, as in the above embodiment, the life of the filtration demineralizer used in the reactor water purification system can be extended, and waste disposal becomes easier.

Example 4 In Example 1, an example was shown in which the filtration demineralizer 4 and the demineralizer 5 were combined in series as a reactor cooling water purification system, but the demineralizer 5 is not necessarily necessary. , it is also possible to use only the filtration demineralizer 4. That is, the filtration demineralizer 4 also uses an ion exchange resin like the demineralizer 5, and it is possible to remove most of the ions and crud in the filtration demineralizer 4, and the demineralizer 5 can remove most of the ions and crud. This is because it only has a backup function. However, when the ion exchange resin according to the present invention is used in the filtration demineralizer 4, neutral salts cannot be completely removed, so the demineralizer 5 is omitted and used in the condenser 2. If the possibility of seawater leakage from the condenser is extremely low, for example if the condenser is made of materials such as corrosion-resistant steel, or if there is no possibility at all, for example, use river water or well water instead of seawater as the cooling water for the condenser. It is better to use it only when it is used.

According to this embodiment, not only the same effects as in the first embodiment can be obtained, but also the demineralizer 5 can be omitted, thereby making it possible to further reduce costs.

Example 5 When the ion exchange resin used in the purification device reaches the end of its lifespan,
It becomes radioactive waste as used ion exchange resin. Such radioactive waste is currently stored and stored within nuclear power plants, and the amount of this waste tends to increase year by year. This example is an example in which the used ion exchange resin (waste resin) generated from the filtration demineralizer 4 shown in Example 1 is thermally decomposed, and is explained using the processing system diagram shown in FIG. do.

The waste resin 27 is discarded from the filtration demineralizer 4 through a backwashing operation, so it is in the form of slurry, which is transferred to the waste resin tank 2.
Temporarily stored at 8. The waste resin in the waste resin tank 28 is supplied in a constant amount to the pyrolysis device 31 by a slurry pump 30 via a valve 29 in a slurry state of approximately 10%. Also 1
The composition of the waste resin used in this example was 60 wt% acrylic carboxylic acid resin and 30 wt% quaternary ammonium resin.
impurities such as cladding were 10 wt%.

The thermal decomposition device 31 is a continuous processing type rotary kiln, and the operating temperature is 500°C. Further, the inside of the thermal decomposition device 31 is purged with nitrogen gas to create an inert atmosphere. The waste resin 27 supplied to the thermal decomposition device 31 is simultaneously dried and thermally decomposed, and is temporarily stored in a powder hopper 35 as a thermal decomposition residue 32. Further, exhaust gas mainly composed of water vapor and hydrocarbons generated during thermal decomposition is sent to an exhaust gas treatment device 34 via a valve 33 and treated. The pyrolysis residue 32 is temporarily stored in a powder hopper 35, then mixed with cement 37 or plastic in a kneader 36, and after the mixing is completed, it is injected into a drum 39 through a valve 38 to be solidified. Next, the functions and effects of this embodiment will be explained.

First, when the waste resin 27 was thermally decomposed by the thermal decomposition device 31, the waste resin 27 was 20wt% by weight and 10vO by volume.
It was possible to reduce it to α%. On the other hand, if the cation exchange resin in the waste resin 27 is a conventional benzenesulfonic acid resin, the total weight of the waste resin will be 40w even if it is thermally decomposed.
t% and volume also decreased to only 25van%.

Furthermore, in the case of the waste resin used in this example, the gas generated by thermal decomposition is only hydrocarbons, whereas in the case of benzenesulfonic acid resin, as is clear from the above structure, sulfur atoms Because of this, thermal decomposition generates SOx and HzS in addition to hydrocarbons.

Since SOx and Hz S are harmful gases, an alkaline scrubber or the like is required to remove them, which complicates the exhaust gas treatment device 34. However, the present invention does not have such drawbacks.

As described above, by using the ion exchange resin according to the present invention and thermally decomposing it, there is an effect that not only the volume of waste resin can be significantly reduced, but also the exhaust gas treatment device can be simplified.

In this example, an example of processing waste resin generated from a filtration desalination device of a boiling water reactor was shown, but in contrast to the treatment of waste resin generated from a filtration desalination device of a pressurized water reactor shown in Example 3. The same applies to

Example 6 Although Example 5 shows the case where the waste resin 27 is subjected to thermal decomposition treatment, the same effect can be obtained by incineration treatment instead of thermal decomposition. In this case, an incinerator may be used instead of the thermal decomposition device 31, and the waste resin may be incinerated at 600° C. or higher in an air atmosphere. With the ion exchange resin based on the present invention, it is possible to significantly reduce the volume, and the exhaust gas treatment device can also be simplified.

This embodiment also has the following effects. In the case of incineration, waste resin is processed at temperatures above 600°C, usually 800 to 1500°C, so there is a problem that some of the waste resin melts and adheres to the furnace walls, shortening the life of the incinerator. However, if the ion exchange resin according to the present invention is used, it can be easily gasified at temperatures below 600° C. and hardly melts because of its low heat resistance.

Therefore, the problem of waste resin adhering to the furnace wall can be significantly reduced, and the life of the incinerator can be extended.

Example 7 In the above example, an example was shown in which a linear cation exchange resin was used in a filtration demineralizer. A device equipped with this can also be used as a filtration demineralizer. In this example, unlike ion exchange resin, it does not leak into the cooling water and does not have the effect of increasing the surface dose rate of piping, and as a filter with a membrane structure that has ion exchange groups, benzene rings are used. By using a polymer in which an element other than carbon and an ion exchange group are combined, it becomes used and is disposed of as waste.
A high volume reduction effect can be expected. In other words, ■■ in Table 1
In order to use a linear polymer such as 0, the above Example 5
, 6 has the same effect. In this way, even in this example in which a polymer having an ion-exchange group bonded to a linear chain is used as a membrane structure filter, an effect equivalent to or better than that of the above-mentioned example can be obtained.

Incidentally, in Example 1, a powdered linear cation exchange resin having an average particle size of about 30 μm was used, but the present invention is not limited to this particle size. For example, a long linear cation exchange resin may be used in only one direction of the male shape, and if such a fibrous linear cation exchange resin is used, leakage from the filtration demineralizer can be avoided. This has the effect of reducing the amount of

The fibrous ion exchange resin may be both a cation exchange resin and an anion exchange resin, or either one.

Further, as long as the fibrous cation exchange resin is long enough to not pass through a nylon or stainless steel filter element, the cation exchange resin alone may be used. That is, since the cladding to be removed is positively charged and ions such as co are also positively charged, they can be removed using only the cation exchange resin. If you do this,
There is no need to use anion exchange resin, and the amount of waste generated can be significantly reduced.

Moreover, the linear cation exchange resin has a lower degree of dissociation (lower pK^, where PK^ is the logarithm of the reciprocal of the dissociation constant) than a sulfonic acid bonded to a benzene ring, and becomes a weak acid type. For this reason, as described above, the ability to decompose neutral salts decreases, making it difficult to remove NaCQ when seawater leaks. Therefore, linear cation exchange resins with a high degree of dissociation (pK^
By attaching an ion exchange group with 3 or less), it becomes possible to remove NaCn without installing a condensate demineralizer afterwards. That is,
In the future, if the possibility of a large amount of seawater leaking is almost eliminated due to improvements in the reliability of nuclear power plant equipment, linear cation exchange resins with highly dissociable ion exchange groups will be used in filtration demineralizers. This allows the condensate demineralizer 5 (see FIG. 1) to be omitted.

Example 8 The performance of the filtration and demineralizer 4 can be improved by optimizing the particle size or adding fiber to the ion exchange resin according to the present invention.

The performance required of the filtration demineralizer 4 is the following two points. The first point is that the filtration life is long. That is, as the filtration time becomes longer, the amount of crud adsorbed and removed by the precoat layer increases, which causes clogging in the precoat layer and increases the filtration pressure difference. When this differential pressure reaches a certain value (usually 1.75 kg/mouth 2-), the powdered ion exchange resin that is the precoat material is backwashed and discarded, and replaced with a new precoat material. Therefore, in order to reduce costs and waste generation, the differential pressure must rise slowly.

In other words, it is desirable that the filtration life is long. The second required performance is a high crud removal rate from the water to be treated, and usually a removal rate of 90% or more is required.

Basic experiment results 1 When using the cation exchange resin according to the present invention, the filtration life is longer than that of conventional strongly acidic sulfonic acid resins, which is a desirable result, but cracks may occur in the precoat layer during the filtration process. The crud removal rate was 6.
It was found that the ratio was as low as 0 to 90%, and that it was sometimes inappropriate to use it as it was in a filtration demineralizer.

The cation exchange resin of the present invention includes carboxylic acid type am, chelating resin, etc., and first, the case where carboxylic acid type resin is used will be explained.

As carboxylic acid resins, methacrylic carboxylic acid resins, acrylic carboxylic acid resins, etc. are known.
When these are used as precoat materials, their performance is almost the same, so they will be collectively referred to as carboxylic acid resins below. Furthermore, so-called granular resins having a particle size of about 500 μm are known as carboxylic acid resins. However, such granular resins have large particle diameters, making them unsuitable for precoating, as well as insufficient filtration effects and low efficiency of ion exchange reactions, making them impractical.

Therefore, the carboxylic acid resin was pulverized and the average particle size was approximately 50 μm.
m of powdered carboxylic acid resin, mixed this with powdered anion exchange resin at a ratio of 2:1, and further added a small amount of polymer flocculant (polyacrylic acid amide, etc.), It was made into a pre-coated material. Using this, water including cladding was filtered. The results are shown in FIG. 13 in comparison with the case where a conventional sulfonic acid resin was used as the cation exchange resin. From this, the filtration differential pressure increases with the filtration time, but with carboxylic acid resins, the filtration differential pressure increases more slowly than with sulfonic acid resins, and the filtration life is about 1.
5 times (however, it can be seen that the filtration pressure difference is 1.75).

However, the crud removal rate decreases with the filtration time, and in the case of carboxylic acid resins, it becomes about 75% when the filtration pressure difference reaches 1.75 kgZ2, and it is not possible to secure the 90% or more that is generally considered necessary.

It was found that the cause of this was that cracks were generated in the precoat layer as the filtration time passed. The details will be explained with reference to FIG.

Generally, after forming a precoat layer 41 with a thickness of 2 to 20 cm on the filter element 21, the water to be treated 42 is filtered. This precoat layer shrinks as the filtration time passes, so that cracks 43 are generated as shown in FIG. 14(b), and the cladding removal rate is reduced. Such a phenomenon is also known for conventional sulfonic acid resins, and it is also known that addition of fibers is effective as a measure to prevent cracks 43. Incidentally, the results for the sulfonic acid resin shown in FIG. 13 are also those in which fibers were added. With conventional sulfonic acid resins, the amount of fiber added is 30 to 60 w.
It is known that t% is suitable, and preferably 50wt%. Therefore, after mixing the carboxylic acid resin and anion exchange resin, the fiber ratio was further increased to 50 wt%.
So that it becomes.

Acrylic fiber (approximately 10 μm in thickness, several 100 μm in length)
m) was added and a filtration experiment was conducted using this as a precoat material. The results are compared with the case without fiber added.
As shown in Figure 5, it can be seen that the fibers are fine.

However, even when the fiber ratio is 5'Ow t%, which is considered to be the optimum for sulfonic acid resins, as is clear from Figure 15, the crud removal rate, which is generally considered necessary, is 9.
There is a problem in that it is not always possible to achieve 0% or more. Therefore, the inventor of the present invention clarified the cause of this problem and also found a countermeasure.

In order to clarify the cause of cracks in the precoat layer when carboxylic acid resin is used, we first investigated the cause of cracks in conventional sulfonic acid resins.

As a result, it was found that the cause of crack generation was due to the shrinkage of the precoat layer 41, and that the cause of the shrinkage of the precoat M41 was a synergistic effect of the following two factors. In other words, the first factor is that the particle surface of ion exchange resins is negatively charged for cation exchange resins and positively charged for anion exchange resins, and electrical repulsion occurs in the precoat layer that uses a mixture of both. The force forms a loose layer called a flock. However, when the cladding is adsorbed, the surface charge is canceled out, so the electrical repulsion force decreases, and the precoat layer contracts and becomes a dense layer. The second factor is that conventional sulfonic acid resins are shrinkable resins whose resin particles shrink when they adsorb cladding, so this also causes the precoat layer to shrink.

This may cause cracks to occur. In this way, with conventional sulfonic acid resins, cracks occur due to a decrease in electrical repulsion when the cladding is adsorbed and the shrinkage of the resin itself, and as a way to prevent this, fibers are added. I found out that there is.

In contrast, it has been newly discovered that the crack generation mechanism is different in carboxylic acid resins. That is, the first
The factor (i!! reduction in pressure repulsion) is exactly the same, but the second factor is different. Namely.

Carboxylic acid resin is an expandable resin in which the resin particles do not contract but rather expand even when the cladding is adsorbed. Therefore, it was found that the second factor moves in the direction of relaxing the shrinkage of the precoat layer, and that the amount of shrinkage of the precoat layer is smaller in the carboxylic acid resin than in the sulfonic acid resin. For this reason, the preferred proportion of fibers in sulfonic acid resins is 30 to 60 wt%.
On the other hand, we thought that carboxylic acid-based resin could prevent cracks from occurring in the precoat layer even with a low fiber content. Therefore, a filtration experiment was conducted by changing the fiber ratio. Figure 16 shows the crud removal rate as a function of the fiber percentage when the filtration pressure difference in the precoat layer is 1.75 kg/cm''.For sulfonic acid resins, the fiber percentage is At 30wt% or less, cracks occur in the precoat layer and the crud removal rate drops sharply, whereas with carboxylic acid resins, as expected, cracks do not occur even if the fiber ratio is small, and the fiber ratio is 10%.
It was confirmed that the crud removal rate was 90% even with %w. On the other hand, even in the region where the fiber ratio is large, the crud removal rate decreases again as shown in FIG. 16.

This is because as the fiber ratio increases, the ratio of ion exchange resin having high filtration performance decreases.

Also, in the case of sulfonic acid resins.

When the fiber ratio is 60wt% or more, the crud removal rate is 90% or less, but for carboxylic acid resins, the fiber ratio is 40wt%.
With this, the removal rate is less than 90%. The reason for this is that sulfonic acid resins are strongly acidic resins and have a high ability to remove crud, so they can maintain the desired performance even if the fiber ratio increases slightly, whereas carboxylic acid resins are weakly acidic resins. Therefore, the ability to remove crud is somewhat low, and therefore the fiber ratio cannot be increased very much.

As shown above, it has been found that carboxylic acid resins and sulfonic acid resins have different physical properties, and therefore the optimum amount of fiber added is also different. In other words, in carboxylic acid resin,
It was found that when the fiber ratio is in the range of 10 to 40 wt%, a crud removal rate of 90% or more can be ensured, which is extremely preferable as a filter demineralizer. Note that the fibers may be of any type, such as acrylic fibers, nylon fibers, vegetable fibers, carbon fibers, etc., and the thickness of the fibers may be from several μm to several tens of μm.
As in the conventional case, the range of m and the length may be in the range of several tens of μm to several I.

From the above, the optimal amount of fiber added has been clarified, but
As already mentioned, carboxylic acid resins have an essential drawback of being weakly acidic and have a slightly low crud removal ability. That is, as can be seen from Fig. 16, in the case of carboxylic acid resin, the crud removal rate reaches the maximum value of 9 when the fiber ratio is about 2 wt%.
3%, whereas sulfonic acid resin shows a maximum of 97%.
becomes.

In order to investigate the reason for this in more detail, we investigated the distribution of cladding adsorbed within the precoat layer.

FIG. 17 shows the results, where the vertical axis shows the concentration of the adsorbed cladding, and the horizontal axis shows the depth measured from the surface of the precoat layer 41 in the direction of the filtration element 21. From this, it was found that the sulfonic acid resin has a high crud removal ability because it is a strong acid resin, and most of the crud is adsorbed near the surface of the precoat layer 41. On the other hand, in the case of carboxylic acid resin, which is a weakly acidic resin, the cladding was adsorbed throughout the precoat layer, and it was found that a portion of the cladding reached the filtration element 21. In other words, since the carboxylic acid resin is weakly acidic, the cladding cannot be completely adsorbed by the precoat layer, and some of it reaches the filtration element, resulting in a low cladding removal rate.

In order to give such a carboxylic acid resin the same crud removal ability as conventional sulfonic acid resins, the inventor thought that reducing the particle size of the resin would be a good method. For conventional sulfonic acid resins, powdered resins having a mesh size of 60 to 400, that is, an average particle size of 50 to 150 μm, are used from the viewpoint of precoating properties. However, for carboxylic acid resins that have a slightly low crud removal ability, increasing the reaction surface area by reducing the particle size will increase the effective crud removal ability.
As a result, we thought that a crud removal rate higher than that of sulfonic acid resins could be obtained. Therefore, we further conducted a filtration experiment by changing the particle size of the carboxylic acid resin. The results are shown in FIG. 18, and in this case, the m-fiber ratio was always 20 wt%.

The crud removal rate shown in Figure 18 is when the filtration pressure difference is 1,
The experimental value is shown when the filter reaches 75 kg/C11", and the filtration life is defined as follows. That is,
Conventional sulfonic acid resins have a powder form of 60 to 400 mesh, preferably 100 to 200 abash, that is, an average particle size of 80 μm, as described in Japanese Patent Publication No. 47-44903.
A size of about m is used. Therefore, the average particle size is 80μ
The filtration life when using a sulfonic acid resin of m is set as 1, and the filtration life of the carboxylic acid resin is shown as a relative value to that. As expected from FIG. 18, it was found that the smaller the average particle diameter, the larger the reaction surface area, and the higher the crud removal rate. In addition, the crud removal rate is 90%.
It has also been found that in order to achieve the above, it is desirable that the average particle diameter is 60 μm or less. On the other hand, the filtration life increases as the average particle size increases, and the reason for this is that the smaller the average particle size, the more likely the pre-coat layer will be clogged during cladding adsorption, and as a result, the filtration differential pressure will rise faster. by. Therefore, in order to have a filtration life equal to or higher than that of conventional sulfonic acid resins, it is desirable that the average particle size of the carboxylic acid resin is 30 μm or more. It is desirable that the average particle size of the carboxylic acid resin is 30 to 60 μm in order to have a particle diameter greater than that of conventional sulfonic acid resins.

To further supplement the explanation, conventional sulfonic acid resins have an average particle size of 50 to 150 fi m (60 to 400 me
sh ) is desirable, whereas for carboxylic acid resins 3
The reason why 0 to 60 μm is desirable can be summarized as follows5: In other words, carboxylic acid resins are weakly acidic (sulfonic acid resins are strongly acidic), so in order to obtain a high crud removal rate, the reaction surface area must be increased. Therefore, it is desirable that the average particle diameter be smaller than that of conventional sulfonic acid resins. However, when the average particle size becomes 50 μm or less, the filtration life rapidly shortens, but because carboxylic acid resins have the opposite expansion property, even if the average particle size is around 30 μm, they can still achieve the same filtration as conventional sulfonic acid resins. You can get longevity.

Although FIG. 18 shows the case where the fiber ratio is 20 wt%, the fiber ratio explained in FIG. 16 is 10 to 40 wt%.
In the t% range, it was confirmed that high filtration performance could be obtained by setting the average particle size to 30 to 60 μm. This will be explained with reference to FIG.

First, regarding the m-fiber ratio shown on the horizontal axis, this is 10wt.
% or less, cracks will occur and the crud removal rate will be 90%.
% or less, and even if it is 40 wt% or more, the proportion of the ion exchange resin decreases relatively, resulting in a low crud removal rate.

Regarding the average particle size shown on the vertical axis, if it is 60 μm or more, the reaction surface area is insufficient and the crud removal rate is low;
If it is less than m, clogging will occur in the precoat layer and the filtration life will be shortened. As described above, carboxylic acid resin 7 is expandable and weakly acidic, and its physical properties are different from those of conventional sulfonic acid resins, so it was found that the optimum conditions for the powdered ion exchange resin are also different.

Although the above explanation has been made using carboxylic acid resin as an example, the same results can be obtained with other ion exchange resins as long as they are based on the present invention. Examples of this include the chelate resins shown in Table 1 O, and the cation exchange resins and anion exchange resins shown in Table 1 ■ are mixed at a ratio of 1:1, and fibers are added to this. The experimental results in the case of
The crud removal rate when changing the μm plant fiber in the range of 0 to 60 wt% (however, the filtration differential pressure is 1.75
kg/ro2) with an average particle diameter of 30°τ”eF, 100
μm chelating cation exchange resin. In this case as well, the fiber proportion is 10 to 40 w as in Figure 16.
It was found that the crud removal rate was highest at t%, and if the particle size of the cation exchange resin was 30 to 60 μm, the crud removal rate was approximately 90% or more.

In addition, when using powdered ion exchange resin as a precoat material, use a weakly acidic cation exchange resin and an anion exchange resin at a certain ratio (usually the ratio of cation exchange resin to anion exchange resin is 4 to 1). However, anion exchange resins include powdered quaternary and tertiary resins.
Class, 2nd class.

Alternatively, primary amine resins and the like can be used as in the past.

〔Effect of the invention〕

According to the present invention, the following effects can be obtained.

(1) I5I! Non-radioactive metals such as Go are no longer allowed to remain in the reactor for long periods of time, thereby suppressing the production of BOcO and other substances, and also suppressing the adhesion of radioactive metals to piping, reducing the amount of radiation exposure of workers inside nuclear power plants. It becomes possible to significantly reduce the amount.

(2) Even if ions and crud are captured in the reactor cooling water, the increase in differential pressure and the occurrence of cracks can be suppressed, and the life of the filtration demineralizer can be extended. Therefore, not only can costs be reduced, but also the amount of waste generated can be reduced.

(3) The cation exchange resin used in the invention can be thermally easily decomposed because the bond energy of the ion exchange group is small, so waste disposal is easy and the volume can be reduced significantly. Moreover, no harmful gas is generated during waste treatment, which has the effect of simplifying treatment equipment.

[Brief explanation of the drawing]

A partially detailed sectional view, FIGS. 3 and 4 are diagrams each explaining the behavior of metal ions in a nuclear reactor, FIG. 5 is a system diagram showing an experimental apparatus for explaining the present invention, and FIG. 6 Figure 7 is a diagram explaining the heat resistance of various cation exchange resins, Figure 8 is a diagram explaining the thermal decomposition characteristics of cation exchange resins, and Figure 9 is a diagram explaining the differences in the filtration demineralizer in the present invention. Figure 10 is a diagram illustrating the relationship between the filtration life and the mixing ratio of negative and positive ion exchange resins, and Figure 11 is a diagram illustrating an atomic couplant system showing another embodiment of the present invention. , FIG. 12 is a diagram showing the change over time in the removal rate used in the present invention, and FIG. 14 is a diagram showing a cross section of the precoat layer.
Fig. 15 is a diagram showing the relationship between crud capture amount and crud removal rate, Fig. 161 is a diagram showing the optimal fiber ratio, and Fig. 17 is a diagram showing the relationship between crud capture amount and crud removal rate.
The figure shows the cladding distribution in the cross section of the precoat layer, No. 18.
The figure shows the optimum particle size range, Figure 19 shows the relationship between the optimum average particle size and fiber proportion, and Figure 20 shows the crud removal rate when changing the fiber proportion. 1... Turbine, 2... Condenser, 3... Reactor cooling water, 4... Filtration desalination device, 5... Desalination device, 6...
Nuclear reactor, 9...15...Water pump, 16...Feed water heater, 17...Precoat tank, 20...Precoat pump, 22...Flock

Claims (1)

[Scope of Claims] 1. Cooling water of a nuclear reactor is brought into contact with a cation exchange resin whose ion exchange group bonded to the main chain of a polymer containing an aromatic ring has a binding energy of 300 KJ/mol or less, and the cooling water is A method for purifying nuclear reactor cooling water, the method comprising purifying the cooling water by capturing crud or cations. 2. The nuclear reactor cooling according to claim 1, wherein the cation exchange resin is a linear ion exchange resin in which an ion exchange group is bonded to an element other than carbon constituting a benzene ring. How to purify water. 3. The reactor cooling water according to claim 1, wherein the cation exchange resin has a bond energy of ion exchange groups of 300 KJ/mol or less and an average particle size of 30 to 60 μm. purification method. 4. The method for purifying nuclear reactor cooling water according to claim 1, wherein the ion exchange resin is a membrane-structured resin filter having an ion exchange group. 5. The method for purifying nuclear reactor cooling water according to claim 4, wherein the resin filter having a membrane structure is a hollow fiber filter. 6. Ion exchange containing 50 to 90 wt% of a cation exchange resin and 10 to 50 wt% of an anion exchange resin whose ion exchange group bonded to the main chain of a polymer containing an aromatic ring has a binding energy of 300 KJ/mol or less 1. A method for purifying nuclear reactor cooling water, which comprises bringing reactor cooling water into contact with a resin to capture crud or cations in the cooling water to purify the cooling water. 7. As the cation exchange resin, any one or a combination of oxybenzyl sulfonic acid resins, acrylic carboxylic acid resins, methacrylic carboxylic acid resins, aromatic carboxylic acid resins, and chelate resins are used. A method for purifying nuclear reactor cooling water according to claim 6. 8. The bonding energy of the ion exchange group bonded to the main chain of the polymer containing an aromatic ring is 300 KJ/mol or less,
A method for purifying nuclear reactor cooling water, which comprises bringing reactor cooling water into contact with a fibrous cation exchange resin to trap crud or cations in the cooling water and purifying the cooling water. 9. The method for purifying nuclear reactor cooling water according to claim 8, wherein the average particle size is 30-60 μm. 10. Contacting reactor cooling water with a cation exchange resin containing a cation exchange resin whose ion exchange group bonded to the main chain of a polymer containing an aromatic ring has a binding energy of 300 KJ/mol or less and reinforcing fibers. A method for purifying nuclear reactor cooling water, the method comprising purifying the cooling water by trapping crud or cations in the cooling water. 11. The reactor cooling water purification device according to claim 10, wherein the proportion of the fibers is 10-40 wt% (based on the dry weight of resin and fibers). 12. A cation exchange resin whose ion exchange group bonded to the main chain of a polymer containing an aromatic ring has a binding energy of 300 KJ/mol or less is brought into contact with reactor cooling water to extract cladding or cations from the cooling water. separating the cation exchange resin from the cooling water after a predetermined period of use, and reducing the volume of the resin by thermally decomposing or incinerating part or all of it. Purification method. 13. The bond energy of the ion exchange group bonded to the main chain of the polymer containing aromatic rings in the reactor cooling water purification system is 300.
A nuclear reactor cooling water purification device characterized in that it is filled with a cation exchange resin of KJ/mol or less. 14. In the reactor cooling water purification system, the bond energy of the ion exchange group bonded to the main chain of the polymer containing the aromatic ring is 30.
Cation exchange resin 50-90wt below 0KJ/mol
% and an anion exchange resin of 10 to 50 wt %. 15. In the reactor cooling water purification system, the bond energy of the ion exchange group bonded to the main chain of the polymer containing the aromatic ring is 30.
0KJ/mol or less, and the average particle size is 30-60
A nuclear reactor cooling water purification device characterized by being filled with μm cation exchange resin.