JPH0882695A - Condensate purification system of nuclear power plant - Google Patents

Abstract

(57) [Summary] [Purpose] To easily remove silica in condensate, generate little amount of used ion exchange resin, and maintain high purity of the primary coolant. [Structure] The steam generated in the nuclear reactor 1 is sent to a turbine 3 through a main steam pipe 2, the steam that has finished its work in the turbine 3 is condensed in a condenser 4, and this condensed water is solidified in a condensate filter 5. After filtering the components and removing ion components with the condensate demineralizer 10, water is supplied to the reactor 1 through the water supply pipe 8. Here, the condensate demineralizer 10
Is composed of a cation resin tower 11, a filter 12 incorporating a reverse osmosis membrane or a hollow fiber membrane, and an anion resin tower 13 which are sequentially connected in series. A silica analyzer is connected to the water supply pipe 8. The cation resin tower 11 is used to make the condensate liquid acidic and the silica into a colloid or insoluble filter 12
And efficiently removed by the anion resin tower 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a condensate purification system for a nuclear power plant, which is intended to remove silica and prevent ion-exchange resin contamination in a condensate demineralizer for a condensate purification system installed in a nuclear power plant. .

[0002]

2. Description of the Related Art A boiling water nuclear power plant sends steam generated in a nuclear reactor 1 to a turbine 3 through a main steam pipe 2 as shown in FIG. After completing the process, the steam is condensed in the condenser 4, and the condensate from the condenser 4 is purified by the condensate purification system 7 including the condensate filtration device 5 and the condensate desalination device 6, and then the water supply pipe 8
Water is supplied to the reactor 1 as a coolant through.

Here, the condensate demineralizer 6 comprises a large number of mixed-bed condensate demineralizers connected in parallel. After the condensate filter 5 collects water, the condensate demineralizer 6, That is, the mixed-bed condensate demineralization tower removes ions and supplies water to the reactor 1. In the figure, reference numeral 9 is a reactor coolant purification system, which purifies the reactor water in the reactor 1.

If silica (SiO ₂ ) is contained as an impurity in the main steam or feed water, silicon compounds are deposited on the turbine system, which causes a reduction in turbine efficiency and accelerates stress corrosion cracking. Therefore, it is necessary to reduce the silica concentration.

Conventionally, the removal of silica in the reactor water has been carried out by backwashing precoating of the filter desalting apparatus of the reactor coolant purification system 9. Further, silica in the pure water of the water supply system is not considered to be an impurity that particularly adversely affects the plant, and the present situation is that no special removing means is applied.

[0006]

Conventionally, there is no epoch-making method for removing silica in condensate water or reactor water,
It is said that the method of removing with an ion exchange resin is the most efficient. In a mixed-bed condensate desalination system using an ion exchange resin, silica is removed by the condensate desalination system while the ion exchange resin is new, but when water is passed for about 1 year, silica has an ion selectivity. Since it is low, it is hardly removed. But,
Since other ions are removed, the function required of the condensate demineralizer is satisfied.

Here, if the chemical solution of the condensate demineralizer is regenerated, the silica removing ability is restored and the silica can be removed again. At the old plant, the concentration of ionic impurities other than silica in the condensate is high, and the condensate demineralizer is operated while regenerating the chemical solution.

[0008] Therefore, although the silica removing ability was maintained to some extent, the condensate demineralizer was operated in a non-regenerative manner (the ion-exchange resin is made to be disposable without regenerating the chemical solution) with the recent purification of condensed water. Operation method) is being performed. In non-regenerative operation, the condensate desalination unit will be operated for many years without silica removal capability.

Further, TOC eluted from the ion exchange resin
(Total organic carbon) became a problem because other impurities decreased as the condensate became highly purified.

The silica concentration in the reactor water is reduced by backwashing or backwashing the conventional reactor coolant purification system filter desalting apparatus. In order to keep the silica concentration low, this is a backwashing or backwashing process. The frequency of should be increased. However, there is a problem that the backwash or the backwash precoating frequency increases, the operator's load and mistakes occur, and the amount of used ion exchange resin is increased.

The present invention has been made in order to solve the above problems, and it is possible to easily remove silica in condensate, generate a small amount of used ion exchange resin, and maintain high purity of the primary coolant. The purpose is to provide a condensate purification system for a nuclear power plant.

[0012]

According to the present invention, steam generated in a nuclear reactor is sent to a turbine through a main steam pipe, steam from the turbine is condensed in a condenser, and the condensed water is condensed into a condensate filter and a condenser. In a condensate purification system of a nuclear power plant in a system for purifying pure water by a condensate purification system consisting of a condensate demineralizer to supply pure water to the reactor as a coolant,
The condensate demineralizer is characterized in that a cation resin tower filter and an anion resin tower are sequentially connected in series.

[0013]

[Function] A low concentration silica ion present in the condensate is made into colloid or insoluble by the cation resin tower of the condensate demineralizer, the particle size is made large and the silica is removed by the filter, and then the anion resin tower Pass water. Although a filtration device is used as an auxiliary means for silica removal, silica is not completely colloided even through the cation resin tower, so silica is removed in the anion resin tower.

In the case where the anion resin tower has a silica break, by adjusting the concentration of sodium hydroxide (NaOH) and circulating it in the anion resin tower, silica having weak ion selectivity (weak bond with the ion exchange resin), etc. It is possible to recover the silica removing ability of the anion resin tower by selectively releasing only the above from the ion exchange resin and performing partial regeneration.

This partial regeneration is very simple in the regeneration operation by adopting the single bed type, the deterioration of the ion exchange resin due to the regeneration operation is suppressed, and the concentration of the waste waste liquid is low because of the partial regeneration. It also has the effect of suppressing the amount generated.

[0016]

EXAMPLE An example of a condensate purification system of a nuclear power plant will be described with reference to FIGS. 1 and 2. In FIG.
The reactor 1 is connected to the main steam pipe 2, and the terminal of the main steam pipe 2 is connected to the turbine 3. The turbine 3 is connected to the condenser 4, and the condenser 4 is connected to the condensate filtering device 5. The condensate filter 5 is connected to the condensate demineralizer 10, the condensate demineralizer 10 is connected to a feed pipe 8, and the feed pipe 8 is connected to the reactor 1.

The condensate demineralizer 10 is a cation resin tower.
11, a filter 12 incorporating a reverse osmosis membrane or a hollow fiber membrane and an anion resin tower 13 are sequentially connected in series, and a large number of sets of this condensate demineralizer 10 are connected in parallel.

FIG. 2 shows a line for supplying NaOH to the anion resin tower 13 from the condensate filter 5 to the water supply pipe 8 in FIG. That is, in FIG. 2, the first isolation valve 14 is connected between the filter 12 and the anion resin tower 13, and the second isolation valve 15 is connected between the anion resin tower 13 and the water supply pipe 8. ing.

A regeneration line 16 branched and bypassed from the outlet side of the first isolation valve 14 and the inlet side of the second isolation valve 15 is connected, and a NaOH circulation tank 17 is connected to this regeneration line 16. This NaOH circulation tank 17 has NaO
The H supply tank 18 and the waste treatment system line 19 are connected. A silica analyzer 20 is connected to the water supply line 8.

In the condensate purification system of the reactor plant having the above structure, the silica concentration at the outlet line of the anion resin tower 13 is monitored by the silica analyzer 20, and the silica break at which the silica concentration at the outlet of the anion resin 13 is confirmed is increased. At this point, NaOH is circulated manually or automatically from the NaOH circulation tank 17 through the regeneration line 16 to regenerate the anion resin or the like 13 to regenerate silica, carbonic acid or the like having weak ion selectivity.

It should be noted that this regeneration can be selectively performed with respect to silica, carbonic acid or the like having a weak ion selectivity by circulating NaOH. In addition, regenerating liquid, NaO
If the silica break does not subside even if the wastewater from the H circulation tank 17 is regenerated, it is discharged to the waste treatment system line 19,
The NaOH circulation tank 17 is replenished from the OH supply tank 18.

Silica break refers to a state in which the ion exchange resin apparently loses the ability of exchanging silica to remove silica, or a state in which silica is detected at the outlet of the ion exchange resin tower. .

Although cations are removed by flowing through the cation resin tower 11, the reaction proceeds in the direction of decreasing concentration of anions due to the theory of chemical equilibrium, and silica exists as ions in the form of anions. To a nonionic (colloidal) state.

After increasing the particle size of this colloid and removing it with a filter, the colloid is allowed to flow into the anion resin tower 13. here,
Even if the cationic resin tower 11 is flown, not all of the silica is made into colloid, so the anion resin tower 13 removes the silica.

When silica breaks in the anion resin tower 13, by adjusting the concentration of NaOH and circulating it in the anion resin tower 13, only silica or the like having weak ion selectivity (weak bond with resin) is selectively selected. By releasing from the ion exchange resin and performing partial regeneration, the anion resin tower 13
The ability of removing silica can be restored.

This partial regeneration is very simple in the regeneration operation by adopting the single bed type, the deterioration of the ion exchange resin due to the regeneration operation is suppressed, the concentration of the waste liquid for regeneration is low,
The amount generated can be suppressed.

In the above embodiment, the condensate demineralizer 10 is used.
By dedicating one column out of the plurality of columns arranged in parallel for silica removal, the anion resin can be regenerated periodically. Also. The condensate purification system of the above embodiment can also be applied to the desalting tower of the liquid waste treatment system line.

[0028]

According to the present invention, in the condensate purification system of a nuclear reactor plant, the ion exchange resin is divided into a cation resin tower and an anion resin tower to collect and store water,
Ion-exchange resin contamination can be reduced.

Further, by installing a reverse osmosis membrane or a hollow fiber membrane device in both resin towers, the silica removal performance is improved and the concentration of silica brought into the reactor is reduced. Therefore, the number of times of backwashing of the reactor coolant purification system can be reduced, and the amount of ion exchange resin can be reduced.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a condensate purification system of a nuclear power plant according to the present invention.

FIG. 2 is a system diagram showing the condensate desalination apparatus in FIG.

FIG. 3 is a system diagram showing a condensate purification system of a conventional nuclear power plant.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor, 2 ... Main steam pipe, 3 ... Turbine, 4 ... Condenser, 5 ... Condensate filter, 6 ... Condensate demineralizer (conventional example),
7 ... Condensate purification system, 8 ... Water supply pipe, 9 ... Reactor coolant purification system, 10 ... Condensate demineralizer (present invention), 11 ... Cation resin tower, 12 ... Filter, 13 ... Anion resin tower, 14 ... First isolation valve, 15 ... Second isolation valve, 16 ... Regeneration line, 17 ... NaOH
Circulation tank, 18 ... NaOH supply tank, 19 ... Waste treatment system line, 20 ... Silica analyzer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Nagasawa 66-2 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba Engineering Co., Ltd.

Claims (5)

[Claims] 1. Steam generated in a nuclear reactor is sent to a turbine through a main steam pipe, steam from this turbine is condensed by a condenser, and this condensed water is composed of a condensate filter and a condensate demineralizer. In a condensate purification system of a nuclear power plant in a system for purifying with a condensate purification system and supplying water to the reactor as a coolant, in the condensate demineralizer, a cation resin tower, a filter and an anion resin tower are sequentially connected in series. A condensate purification system for a nuclear power plant, which is characterized by consisting of 2. The condensate purification system for a nuclear power plant according to claim 1, wherein the filter has at least one of a reverse osmosis membrane and a hollow fiber membrane incorporated therein. 3. A regeneration line for circulating sodium hydroxide (NaOH) bypassing the inlet side and the outlet side of the anion resin tower.
Condensate purification system of the nuclear plant described. 4. The condensate purification system for a nuclear power plant according to claim 1, wherein a silica meter is connected to the outlet side of the anion resin tower. 5. An NaOH circulation tank is provided in the regeneration line, a waste treatment system is connected to the outlet side of the NaOH circulation tank, and the anion resin tower is provided in the waste treatment system. A condensate purification system for a nuclear power plant according to claim 1.