JPH0653276B2 - Condensate demineralizer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a desalination apparatus, and more particularly to a desalination apparatus suitable for a condensate deionization apparatus using an ion exchange resin.

[Background of the Invention]

A conventional nuclear reactor system, particularly a boiling water reactor system, has a structure as shown in FIG. 1, and steam flowing out of a reactor pressure vessel 1 equipped with a reactor cleaning system 10 is a high pressure turbine 2 and a moisture separator 3 Then, it flows into the condenser 5 through the low pressure turbine 4 and is condensed in the condenser 5 to be condensed water. The low-pressure turbine 4 communicates with a water supply heater 9 via an extraction system 11, and the water supply heater 9 includes a condenser 5 via a heater drain system 12.
Is in communication with. Therefore, the corrosion products (hereinafter referred to as “clads”) generated in the condenser 5, the extraction system 11 and the feed water heater 9 become impurities in the condensate, and these impurities are desalted and filtered in the condensate demineralization tower 7. It The condensed water from which the impurities are removed flows into the reactor pressure device 1 through the feed water heater 9, and thereafter, the condensed water is repeatedly circulated in the same manner as this.

In the reactor having the above-described structure, the cladding that has not been filtered by the condensate demineralizer 7 flows into the reactor vessel 1 and is activated, and is attached to the equipment and the piping through this activation. However, an increase in the plant dose rate (exposure dose rate) is a problem. Recently, however, it has become clear that the rate of rise in plant dose can be reduced by reducing the amount of iron introduced into the water supply. By the way, most of the existing plants desalinate and filter the condensate using the above-mentioned condensate demineralizer alone, so the removal rate of the clad is low at 60 to 70%. Concentration of condensate in Japan is 15
The clad concentration of the condensate at the outlet of the condensate demineralizer is 4 to 10 ppb, while it is about 25 ppb. Therefore, the amount of cladding (the main component of which is iron oxide having a particle size of 0.45 μm or more) brought into the reactor reaches 200 to 500 kg per year in a 1100 MWe class reactor.

This is because the conventional demineralizer is condenser water (eg seawater)
Assuming a leak, etc., it is installed to prevent corrosion of the equipment piping due to this, and the desalinizer is considered to exert its ion removing ability, and no consideration was given to the clad removing ability.

Examples of devices related to this type of device include, for example, "Thermal Nuclear Power Generation" vo135, No, 12, 1984 "BWR.
Improving the iron removal performance of the condensate demineralizer. "

[Object of the Invention]

An object of the present invention is to provide a condensate desalination apparatus that can effectively reduce the radiation dose rate of a plant and the amount of radioactive waste by effectively using a cationic resin.

[Outline of Invention]

In order to achieve the above-mentioned object, the present invention provides a condensate demineralization tower in which a cation resin and an anion resin are incorporated to perform condensate demineralization treatment, and the two resins are introduced from the condensate demineralization tower, A first separation column that separates the two due to the difference in specific gravity, and an anion resin treatment column that introduces the anion resin separated in the first separation column and discharges it to the waste treatment system to introduce a new anion resin And a second separation column which introduces a mixture of the two resins from the first separation column and reseparates the two resins due to the difference in specific gravity thereof, and a cationic resin separated in the second separation column A line for returning the gas to the first separation column;
And the new anion resin is introduced from the anion resin treatment tower, respectively, and the mixture is returned to the condensate demineralization tower. It is a thing.

Ion exchange, surface filtration, and adsorption are the functions of iron capture by resin, but iron in condensate mainly exists as insoluble matter (clad), and its particle size is as shown in FIG. It is considered that adsorption is predominant because it is extremely smaller than the resin and the voids between the resins and is unlikely to be mere mechanical filtration.

The affinity between the resin and the cladding, which is the basis of adsorption, is presumed to have a large contribution to the interfacial electrical performance in the condensate.

FIG. 4 summarizes the charged states of the cladding and the ion exchange resin in water in the relationship of PH. Boiling water nuclear power plant that uses neutral pure treatment for condensate treatment (hereinafter BW
In R), PH has a value in the neutral region, that is, in the vicinity of 7. From FIG. 4, when PH is in the vicinity of 7, the cation resin is negatively charged and the anion resin is positively charged.
On the other hand, the cladding is charged to the + side when PH is around 7. Therefore, in the neutral region, the cladding is electrically considered and adsorbs to the cationic resin. Therefore, Clad is B
Under the WR environment, it is mainly adsorbed on the cationic resin.

On the other hand, the removal performance of the condensate demineralization tower of the domestic A plant has changed over time, as shown in Fig. 5, and the removal performance has improved over time, and the use history of the resin has a large effect on the removal performance. Things have become apparent.

Fig. 6 shows the change in iron removal performance with respect to the cladding load at the domestic B plant.

As shown in FIG. 6, the removal performance improves as the cladding load increases. Therefore, it was found that the ion-exchange resin in the demineralization tower has improved iron removal performance due to the increase in usage history and the load of the cladding. A test was conducted to infer this cause. The results are shown in FIG. 7th
The figure is the result of the test which combined the new resin and the old resin.
From Figure 7, regardless of whether the anion resin is new or old,
It can be seen that if the cationic resin is an old resin, the removal performance is good. Therefore, it is presumed that the secular improvement of the condensate demineralization tower removal performance is due to the change of the surface state (potential) of the cation resin.

From the above test results, the iron removal performance of the condensate demineralization tower is due to the cation resin, and the iron removal performance of the cation resin is improved over time due to the change in the surface state (potential) over the years of use. It became clear. Therefore, as a method for improving the removal performance of the condensate demineralization tower, it is effective to exchange only the anion resin for the ion exchange resin in the condensate demineralization tower and use the cation resin as it is.

Regarding the ion exchange resin in the condensate demineralization tower, judging from the ion exchange capacity and the deteriorated state of the resin strength, the anion + cation resin has been exchanged at the same time.

The reason for simultaneously exchanging the anion and cation resins is to keep the ion exchange capacity of the condensate demineralization tower constant.

Figure 8 shows the changes over time in the ion exchange capacities of anion and cation resins. The amount of anionic resin is about 6 to 7 years, which is less than or equal to the minimum required amount when seawater leak is assumed, but the amount of cation resin cannot be less than or equal to the minimum required amount even if used for 20 years or more. On the other hand, FIG. 9 shows the deterioration state of the strength of the ion exchange resin with respect to the years of use. The strength of the anionic resin is significantly deteriorated over the years of use, but the strength of the cationic resin is not significantly deteriorated even after 8 years of use.

Therefore, judging from the viewpoints of ion exchange capacity and resin strength, it was revealed that the anion resin needs to be replaced after 6 to 7 years, but the cation resin can be continuously used. .

As described above, in the condensate demineralization tower, the removal performance is improved due to the change of the surface condition of the cation resin, and from the viewpoint of the ion exchange capacity and the resin strength, the condensate deionization tower continues to be used after the anion resin exchange. Since it can be used, it is effective to leave the cation resin and replace only the anion resin to improve the iron removal performance of the condensate demineralization tower.

Example of Invention

 An embodiment of the present invention will be described below with reference to FIG.

The condensate demineralizer 7 is filled with the ion exchange resin 13, and the condensate is introduced from the condensate system 18 and treated by the condensate demineralizer 7. When it is necessary to replace the anion exchange resin in terms of ion exchange capacity and strength deterioration, the ion exchange resin 13 (anion resin, cation resin) is pressure-fed to the cation resin regeneration tower 14 of the regeneration system. Here, the ion exchange resin is separated into an anion resin and a cation resin according to the difference in specific gravity by the water injected from the bottom of the cation resin regeneration tower 14. The separated anion resin is transferred to the anion resin regeneration tower 15 together with water. The cation resin is transferred from the cation resin transfer line 19 to the resin mixing tower 16. On the other hand, anion resin regeneration tower 1
The anion resin transferred to No. 5 is the waste resin transfer line 21.
Is transferred to the waste resin storage tank of the waste treatment system.
Next, new resin of anion resin is introduced into the anion resin regeneration tower from the new resin introduction port 17, and is transferred to the resin mixing tower via the anion resin transfer line 22. Here, after mixing the new anion resin and the old cation resin, the condensate demineralizer 7 is charged again via the resin transfer line 20.

In addition, in order to completely remove the old anion resin when separating the anion and cation resins, the cation regeneration tower 14
It is carried out by lowering the anion resin extraction nozzle in step 1.

Preliminary separation column 2 to eliminate other old anion resins
3, the mixed layer of cation resin and anion resin in the cation resin regeneration tower 14 is transferred to the preliminary separation tower 23,
By completely separating the resin, the resin separation is carried out in such a way that no old anionic resin remains.

According to this example, the old anion resin is completely eliminated,
It is possible to use a cation resin whose clod removal performance improves with use history without replacement, and is effective in improving the removal performance of the condensate demineralization tower.

FIG. 10 shows a comparison between the annual Fe carry-in amount when the anion resin and the cation resin were exchanged as in the conventional case and the annual Fe carry-in amount according to the present invention in the 1100 MWe class plant.

From FIG. 10, according to the present invention, the annual Fe carry-in amount can be reduced by about 1/2 as compared with the conventional simultaneous exchange of cation and anion resins by improving the condensate demineralization tower removal performance.
The resin exchange frequency is the same as in the conventional case for the anion resin, but it can be reduced to at least 2 times / 30 years for the cationic resin compared to the conventional 5 times / 30 years. A trial calculation based on the amount of resin used in a 1100 MWe class nuclear power plant indicates that the amount of drums generated at one time is about 400, and 1200 can be reduced over the 30-year operating life of the plant. The resin cost is 1
The cost is around 80M ¥, and similarly, it will be reduced by 240M ¥ in 30 years.

〔The invention's effect〕

According to the present invention, since it is possible to maximize the use of a cationic resin whose iron removal performance is improved depending on the usage history, it is possible to suppress the amount of iron carried into the furnace and effectively reduce the radiation dose rate in the plant. it can.

Further, it is possible to effectively reduce the amount of radioactive waste generated by exchanging the ion exchange resin.

[Brief description of drawings]

Fig. 1 is a system diagram of the condensate demineralizer regeneration system, Fig. 2 is a schematic diagram of the plant system, Fig. 3 is a diagram showing a comparison of particle sizes of resin and cladding, and Fig. 4 is a diagram of cladding and ions in water. FIG. 5 is a diagram showing the charged state of the exchange resin, FIG. 5 is a diagram showing the secular change in the iron concentration at the outlet of the condensate demineralizer of the actual machine, and FIG. 6 is a diagram showing the relationship between the cladded load and the outlet iron concentration Fig. 7 shows the effect of outlet iron concentration on old and new resin, Fig. 8 shows the secular change of the flow-through ion exchange capacity of resin, and Fig. 9 shows the secular change of resin crush strength. FIG. 10 is a diagram showing a comparison between the annual Fe carry-in amount in the case where the anion resin and the cation resin are exchanged and the annual Fe carry-in amount according to the present invention in a 1100 MWe class plant as in the past. 1 ... Reactor, 2 ... High-pressure turbine, 3 ... Moisture separator, 4 ... Low-pressure turbine, 5 ... Condenser, 6 ... Condensate pump, 7 ... Condensate demineralizer, 8 …… Water pump, 9 ……
Feed water heater, 10 ... Furnace purification system, 11 ... Extraction system, 12
…… Heater drain system, 13 …… Ion exchange resin, 14…
… Cation resin regeneration tower, 15 …… Anion resin regeneration tower,
16 ... Resin mixing tower, 17 ... New resin inlet, 18 ...
Condensate system, 19 ... Cation resin transfer line, 20 ... Resin transfer line, 21 ... Waste resin transfer line, 22 ... Anion resin transfer line, 23 ... Preliminary separator, 24 ...
Anion resin extraction nozzle.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Ohsumi 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory (56) References JP-A-57-71689 (JP, A) JP 58-101782 (JP, A)

Claims (1)

[Claims] 1. A condensate demineralization tower that incorporates a cation resin and an anion resin for demineralizing condensate, and the two resins are introduced from the condensate demineralization tower, and the two are separated by the difference in their specific gravities. And a first separation column for introducing the anion resin separated in the first separation column and discharging the anion resin into the waste treatment system to introduce a new anion resin, the first separation column A second separation column that introduces a mixture of the two resins from the column and reseparates the two resins by the difference in their specific gravities, and a cation resin separated in the second separation column is the first separation column. To the condensate demineralization tower by introducing the cation resin separated from the first separation tower and the new anion resin from the anion resin treatment tower, and mixing them. A condensate demineralizer equipped with a mixing tower.