JPS58193495A - Condenser for bwr type reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to boiling water nuclear power generation equipment, and particularly to a condensing device suitable for reducing radioactivity in a plant.

In a boiling water reactor, steam is used to rotate a turbine, then the steam is cooled and condensed in a condenser, impurities are removed from the condensed water in a purification device, and the water is heated to 7 Jo again using a feed water heater and returned to the reactor. If corrosion products (hereinafter referred to as crud) due to corrosion of piping, etc. are present as impurities in this feed water, they will become radioactive in the reactor and -
Radioactive crud will adhere to the secondary system piping, increasing the radiation rate of the plant. Based on this, previous research has succeeded in significantly reducing the occurrence of crud in the water supply system by injecting #l element, and it is possible to reduce the occurrence of crud in the water supply system to less than 0.5[)pb. It becomes.

In addition, the material a of the condenser, which is the main source of the upper fil14 crud of the condensate purification equipment, is made of weather-resistant steel (for example, 8
By adopting MA41A, etc.), the cladding load of the purifier is reduced to 109Pb, which is 1/3iK of the conventional one.

However, even in this case, the performance of the condensate purification device is 50″4
~70% so the crud leaking is 3-5P
For pb and 1100 MWe power class 1 Ashi Kagura/to, the amount of crud brought into the reactor per year is 120Kl to 200Kl.
Kf, and the radiation sensitivity is predicted to exceed 10011t/Hr.

Therefore, current line layers are concerned with improving the performance of condensate purifiers and further reducing condenser corrosion. As for the special characteristics, recent research has shown that weathering steel such as 5MA41A has been adopted as the material for the condenser. It has been found that common carbon steels and co-workers are extremely susceptible to corrosion in water (~7 ppb).

A conventional condenser will be explained with reference to Figure 1.

The steam that has left the turbine enters the condenser 2 through the steam line 1, condenses into water droplets as it passes through the cooling pipe 3, is degassed in the tray 4, flows to the hot well 5, passes through the condensing pipe 6, and becomes condensed. Go to the purifier.

Currently, the condenser 2, tray 4, and hot well 5 are all made of weather-resistant steel. 3 The body of water vessel 2 is 4
The tray 4 and the hot well 5 are in contact with deaerated water. Therefore, the crud generated in the condenser is generated in the tray 4 and the real well 5.

FIG. 2 shows a detailed view of the tray. As shown, the tray is composed of various L-shaped angles, and the amount of crud generated is extremely large.

An object of the present invention is to provide a condenser for reducing crud generation.

Based on test results showing that weathering steel has a high corrosion release rate compared to degassed water, the present invention has developed a system that uses stainless steel for the parts of the condenser that come into contact with degassed water.
This reduces the amount of crud carried into the reactor.

Figure 3 shows the food release rate relative to degassed water. From this, the corrosion release rate of stainless steel is about 1 compared to weathering steel.
/2000 or less.

One embodiment of the present invention will be described below.

As you know, the parts of the condenser that come into contact with deaerated water are the tray and the real well. Since the amount of crud generated depends on the area of the area in contact with the degassed water, the amount of crud generated is currently 10,100.
Comparing a tray and a hotwell in a condenser with an output number of O, the area of the tray is 750-, about three times that of a hotwell, and if the tray is made of stainless steel (for example, 5US304), the crud will be significantly reduced. It turns out.

Therefore, when calculating the amount of crud carried into the reactor when the tray is made of stainless steel, the performance of the condensate purification system is '10.
As a percentage, it can be reduced from half-uniform weathering steel noodles of 160 to 804, about half.

Figure 4 is a table of primary system piping showing this effect.
It is a characteristic diagram which analyzed the relationship between Awk rate and the amount of crud brought in. According to Tore, the future dose rate will be 170 ml (i/H
r to 110 mR/Hr, which can be reduced by about 35-.

According to the present invention, by reducing the crud generated from the condenser, the plant radiation rate can be kept low, thereby reducing the radiation exposure of nuclear power plant employees during regular periods, etc. has a good effect.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the condenser, Figure 2 is a detailed diagram of the tray, Figure 3 is a characteristic diagram showing the corrosion rate depending on the material, and Figure 4 is the correlation between the amount of iron brought into the feed water and the dose rate on the pipe surface. FIG. [

Claims (1)

[Claims] 1. A BWR condenser that condenses steam generated from a nuclear reactor and is characterized by using austenitic stainless steel for the tray that deaerates condensate.