JPH0634087B2 - Nuclear power plant - Google Patents

Description

The present invention relates to a nuclear power plant, and more particularly to reducing the ionic activity concentration in a nuclear reactor and the replaceable radiation source in a reactor pipe. The present invention relates to a nuclear power generation facility capable of reducing radiation exposure.

(Prior Art) In a so-called dual boiling water nuclear power plant equipped with both a filtering device and a desalting device in a condensate purification system, iron oxide in the condensate is collected by the filtering device and the desalting device, and water is supplied. The concentration of iron oxide from the system was drastically reduced, and the amount of iron oxide carried into the reactor was drastically reduced. Therefore, radioactive material generated by the activation of iron oxide in the reactor (hereinafter abbreviated as sedimentation source)
Has been drastically reduced, and the resulting exposure has been reduced. However, since the amount of iron oxide has decreased, nickel and cobalt that are corroded and eluted from stainless steel of the water supply system and the reactor system cannot be caught by the iron oxide and continue to adhere to the surface of the fuel rod. For this reason, ionic radioactive substances in the reactor water will be increased, and these will be incorporated into the oxide film formed during the operation of the reactor primary system piping (hereinafter abbreviated as a replaceable radiation source) to increase the radiation dose rate. I was allowed to do it.

As a countermeasure against this, in a boiling water nuclear power generation facility that uses a powder ion exchange resin (hereinafter abbreviated as FD) as a condensate filtration device, FD bypass or loose precoat of FD powder ion exchange resin is performed to remove the condensate. The iron oxide load on the salt equipment is increased, and the condensed iron oxide is leaked from the outlet of the condensate desalination equipment. In this way, the iron oxide concentration is controlled so that the nickel-to-iron concentration ratio is 1/2 or less in the water supply system, and iron oxide is injected into the reactor from the water supply system.

Here, the number less than 1/2 of the nickel to iron concentration ratio is
It is a value that allows iron oxide to capture nickel and cobalt that have become ionic due to corrosion elution in the nuclear reactor and sufficiently adhere and maintain them on the fuel rod surface. If nickel etc. can be sufficiently adhered and maintained on the surface of the fuel rods in this way, the concentration of ionic radioactivity in the reactor water can be reduced, reducing the incorporation of radioactivity into the oxide film of the reactor piping, that is, the replaceable radiation source. Can be reduced.

(Problems to be solved by the invention) However, in the control of the nickel-to-iron concentration ratio by such FD bypass, the iron oxide concentration in the condensate differs depending on the individual nuclear power generation facility, the FD, the condensate demineralizer, etc. This is not always possible due to the different iron oxide removal performance of the above, and as a result of increasing the iron oxide load on the condensate demineralizer, there is a problem of fouling the resin of the condensate demineralizer. There is.

The present invention has been made in consideration of such points,
An object of the present invention is to provide a nuclear power generation facility that can reliably control the concentration ratio of nickel to iron in a water supply system without burdening the condensate demineralizer.

[Structure of Invention]

(Means for Solving Problems) The present invention relates to a condensate filter for collecting iron oxide in condensate produced by reactor steam rotating a turbine, to a condensate dewatering system via a condensate system pipe. A nuclear power generation facility to which a salt device is connected, and a water supply system pipe for feeding water to a nuclear reactor is connected to the condensate demineralizer, and an iron injection device for adjusting an iron oxide injection amount to the condensate filtration filter. Is connected by an iron receiving pipe, the iron injection pipe of the iron injection device is connected to the water supply system pipe, and the iron oxide collected by the condensate filtration filter is injected into the water supply system pipe. It has a feature.

(Operation) According to the present invention, since an arbitrary amount of iron oxide can be injected into the water supply system pipe by the iron injection device, it is possible to reliably control the concentration of nickel to iron in the water supply system to an arbitrary concentration.

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

FIG. 1 is a schematic system diagram showing an example of a nuclear power generation facility according to the present invention.

A main steam pipe 3 having a main steam valve 2 is connected to the reactor 1,
The main steam pipe 3 is connected to a turbine 4, and a condenser 5 is provided below the turbine 4. A condensate pump 6, a hollow fiber membrane filter 8 serving as a condensate filtration filter, and a condensate demineralizer 9 are sequentially connected to the condenser 5 via a condensate system pipe 7. Further, a feedwater heater 12 is connected to the condensate demineralizer 9 via a water supply system pipe 10, and this water supply system pipe 10 is connected to the reactor 1, and a water supply oxygen injection device is connected to the water supply system pipe 10. 11 and a water supply sampling device 14 are connected.

Here, the hollow fiber membrane filter 8 is for removing the clad (iron oxide) in the condensate, and the condensate demineralizer 9 is for removing the ionic impurities in the condensate. The apparatus 11 is an apparatus for injecting oxygen in order to suppress corrosion in the feed water heater 12 and feed water. The feed water sampling device 14 is for measuring the iron concentration and the nickel concentration in the feed water.

Further, an iron injection device 13 is connected to the hollow fiber membrane filter 8 via an iron receiving pipe 22, and an iron injection pipe 23 on the outlet side of the iron injection device 13 is connected to a water supply system pipe 10 on the outlet side of the feed water heater 1. It is connected. This iron injection device 13 is used for the iron receiving tank 1
5, a circulation pump 16, a circulation regulating valve 18, a circulation sampling device 19, and an iron injection regulating valve 20 are connected by a circulation pipe 17.

Next, the operation of this embodiment having such a configuration will be described.

The steam generated in the reactor 1 flows from the main steam valve 2 to the main steam pipe 3
Condensate is condensed in the condenser 5 via the turbine 4 and the turbine 4. This condensate flows into the hollow fiber membrane filter 8 via the condensate pump 6,
Most of the iron oxide in the condensate is collected by the hollow fiber membrane filter 8. After that, the condensate passes through the condensate demineralizer 9 to remove almost 100% of iron oxide in the condensate, and returns to the reactor 1 via the water supply system. During this time, oxygen is injected into the water supply by the water supply oxygen injecting device connected to the water supply system pipe 10 to suppress corrosion in the water supply system.

In this case, the iron concentration in the water supply is determined by the water supply sampling device 14
Although it can be confirmed by, it is normally maintained at an extremely low level of about 0.5 ppb or less.

The iron oxide collected by the hollow fiber membrane filter 8 flows back through the hollow fiber membrane filter 8 so that the iron receiving pipe 22
It is collected in the iron receiving tank 15 of the water supply iron injecting device 13 and is stored in the water in the iron receiving tank 15. In this case, the circulation pump 16 is operated and the iron oxide-containing water circulates in the circulation pipe 17. The iron oxide concentration of this circulating water is measured by the circulating sampling device 19.

On the other hand, the nickel and iron concentrations are confirmed by the water supply sipping device 14, the opening of the iron injection adjusting valve 20 is adjusted so that the nickel to iron concentration ratio in the water supply system is 1/2, and the necessary iron oxide is supplied. Inject into.

As described above, according to this embodiment, the nickel-to-iron concentration ratio in the water supply system can be reliably controlled to 1/2 or less. Further, since the iron oxide collected by the hollow fiber membrane filter 8 is sent to the iron injection device 13, the load of iron oxide on the condensate demineralization device 9 can be reduced. Furthermore, since the hollow fiber membrane filter 8 is used as the condensate filter instead of the powder ion exchange resin (FD), the iron oxide can be easily collected by backwashing.

〔The invention's effect〕

As described above, according to the present invention, the nickel to iron concentration ratio in the water supply system can be reliably controlled to an arbitrary concentration. Further, the load of iron oxide on the condensate demineralizer can be reduced.

As a result, the ionic radioactivity concentration in the reactor water can be reduced, the radioactivity taken into the oxide film formed in the reactor primary system piping can be reduced, and the replaceable radiation source can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic system diagram showing an example of a nuclear power generation facility according to the present invention. 1 ... Reactor, 4 ... Turbine, 5 ... Condenser, 7 ...
Condensate piping, 8 ... Hollow fiber membrane filter, 9 ... Condensate demineralizer, 10 ... Water supply piping, 13 ... Iron injection device, 15
…… Iron receiving tank, 16 …… Circulation pump, 17 …… Circulation piping, 18 …… Circulation adjustment valve, 20 …… Iron injection adjustment valve, 22
…… Iron receiving pipe, 23 …… Iron injection pipe.

Claims (1)

[Claims] 1. A condensate demineralizer is connected via a condensate system pipe to a condensate filtration filter for collecting iron oxide in condensate produced by rotating a turbine by turbine steam. In a nuclear power generation facility to which a water supply pipe for sending water to a nuclear reactor is connected to a desalination device, an iron injection device for adjusting the iron oxide injection amount is connected to the condensate filter by an iron receiving pipe, and the iron injection is performed. A nuclear power generation facility characterized in that an iron injection pipe of the apparatus is connected to the water supply system pipe, and the iron oxide collected by the condensate filtration filter is injected into the water supply system pipe.