JPS62142901A - Steam generator - 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] [Industrial application field] The present invention relates to a steam generator for a fast breeder reactor.

[Conventional technology]

Figure 3 shows an example of the configuration of the secondary main cooling system of a fast breeder reactor.

The secondary main cooling system mainly includes an intermediate heat exchanger 9, a steam generator 6, a secondary main circulation pump 1o, and a sodium main pipe connecting these devices. In this secondary main cooling system, the high-temperature secondary sodium that has exchanged heat with the primary sodium from the reactor passes from the intermediate heat exchanger 9 through the hot leg piping 11 and reaches the steam generator 6. After exchanging heat with the water/steam system 12 on the turbine side and reaching a low temperature, it passes through the cold leg piping 13 to the intermediate heat exchanger 9.
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FIG. 4 shows an example of the structure of a general steam generator 6 applied to this secondary main cooling system. The steam generator 6 includes an internal structure composed of a tube bundle section consisting of a large number of heat transfer tubes 1, an internal shroud 14, an external shroud 15, etc., an outer shell 2,
It is composed of an external structure including a main body support part 16, a sodium inlet nozzle 3, a sodium outlet nozzle 4, a water/steam header 17, and the like. Water and steam flow inside the heat transfer tube 1,
Sodium flows outside the heat exchanger tube 1, and the inside of the outer shell is filled with sodium. Heat exchange is performed through one wall of the heat exchanger tube.

Now, if the wall of the heat transfer tube 1 is damaged in the steam generator 6, the water/steam flowing inside the tube comes into contact with the sodium flowing outside the tube, a so-called sodium/water reaction occurs, and a large amount of heat and hydrogen are generated. Things arise. For this reason, the pressure within the steam generator increases rapidly, and this pressure increase is considered to propagate as a shock wave to other devices through the secondary main piping, significantly affecting the structural integrity of one device.

When a liquid-free steam generator as shown in FIG. 4 is used in a secondary main cooling system as shown in FIG. 3, the secondary main circulation pump 10 installed in the cold leg piping 13 Since the shock wave generated in the steam generator 6 is transmitted to the intermediate heat exchanger 9 through the hot leg piping 11, it contributes to the reflection of pressure waves.

As an effective means for reducing the influence of this pressure propagation and ensuring the integrity of the intermediate heat exchanger, there is a method of creating a gas space by providing a free liquid level within the steam generator. Figure 5 shows a structural diagram of the steam generator of the French fast breeder reactor [Super Phoenix ■] that uses this method. In this figure, the same parts as in FIG. 4 are indicated by the same numbers.

The structure is the same as that shown in FIG. 4, and is composed of a heat exchanger tube 1, an inner shroud, an outer shroud, an outer shell 2, a main body support part 16°, a sodium inlet nozzle 3, a sodium outlet nozzle 4, a water/steam header 17, etc.

Water and steam flow inside the heat exchanger tube 1, and sodium flows outside the heat exchanger tube 1, and heat exchange is performed through the wall of the heat exchanger tube 1.

An overflow nozzle 18 is provided at the upper part of the steam generator 6, and a free liquid level is created by the overflow of sodium, thereby creating a gas space 19. The shock wave generated by the sodium-water reaction due to the failure of the heat exchanger tube 1 is sufficiently reduced within this gas space before reaching the intermediate heat exchanger.

The volume of the gas space necessary to reduce shock waves is considered to be sufficient at most, and the increase in the dimensions of the steam generator due to the provision of this gas space is only a small amount, and it is not large in terms of physical quantity. There was no impact. Therefore, this method is an extremely effective means for reducing shock waves.

In addition, Figure 5 is published by Nuclear Engineering, 6, 1978 (NUCL).
EARENGINEE! RING INTERNATION
ONAL, June 1978).

[Problem that the invention seeks to solve]

In the above conventional example, an overflow nozzle is provided in the steam generator to create a free liquid level and a gas space. Another possible method for creating a free liquid level is to connect a cover gas system to the top of the steam generator and control the liquid level using gas pressure.

However, as is clear from the structure of these methods,
An attached system (overflow system, cover gas system, 1lii) is required to create a gas space.

An object of the present invention is to provide a steam generator that can create a gas space inside it without installing an overflow system or a cover gas system.

[Means for solving problems]

The above object is achieved by providing a vent hole in the sodium inlet nozzle inserted inside the steam generator.

[Effect]

When filling the secondary main cooling system with sodium, if the sodium liquid level in the steam generator exceeds the level of the gas vent hole provided in the natwau nozzle inserted from the top of the steam generator, the sodium inlet nozzle and The space between the outer shell of the steam generator becomes a sealed gas space, and from then on, the rise in the sodium liquid level is suppressed by the gas pressure in this sealed gas space, making it possible to create a gas space above the steam generator. can.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a structural diagram of a steam generator that has been converted into a steam generator, with a sodium inlet nozzle 3. A sodium outlet nozzle 4 is connected to the bottom. The sodium inlet nozzle 3 is inserted inside the steam generator,
A gas vent hole 5 is provided at an appropriate position from the nozzle tip.

Let's consider sodium filling into a steam generator configured in this way. Sodium is supplied through the sodium inlet nozzle 3 or the sodium outlet nozzle 4 from the 1-lium supply system (not shown in the figure), while discharging the gas filling the inside of the steam generator 6 from the sodium inlet nozzle. It is stored in the steam generator. The discharged gas is exhausted to the outside of the secondary cooling system by an appropriate gas venting device provided on the piping connected to the sodium b-containing nozzle. However, the sodium liquid level in the steam generator is lower than the gas vent hole 5 provided in the sodium inlet nozzle 3.
When the level is exceeded, the space between the sodium inlet nozzle 3 and the steam generator outer shell becomes a sealed gas space 1[7, and the gas filling this space is no longer discharged. Therefore, from then on, the rise in the sodium liquid level is suppressed by the gas pressure in the sealed gas space 7, and a gas space can be created above the steam generator.

In a steam generator like this steam generator, which has a free sodium liquid level inside, in order to prevent the cover gas from being entrained by the flow near the sodium inlet nozzle during normal use, the sodium liquid level should be kept at about 1 m from the tip of the inlet nozzle. 6 The present invention solves this problem by simply providing a gas vent hole in the sodium inlet nozzle without requiring the installation of new accessory equipment such as an overflow system or cover gas system. It is extremely useful in that it can be produced by itself.

Furthermore, since the sodium liquid level can be adjusted only by the height of the gas vent hole 5, the volume of the sealed gas space 7 can be adjusted by simply adjusting the drilling position of the gas vent hole 5 during the manufacturing and welding stage of the sodium inlet nozzle 3. can be adjusted freely.

In addition, a small-diameter gas vent hole 5 is sufficient, and during normal use, sodium will flow out through this hole, so there is no need to worry about the problem of cover gas being drawn in from this hole. .

FIG. 2 shows another embodiment of the invention, a steam generator 6 in which the sodium inlet and outlet nozzles are configured as a single double tube nozzle.

A double tube nozzle 8 consisting of an outer tube as a sodium inlet nozzle 3 and an inner tube as a sodium outlet nozzle 4 is inserted into the upper part of the outer shell 2 housing the heat exchanger tube 1. A gas vent hole 5 is provided in the same manner as in Figure 1.

The method of forming the sealed gas space 7 accompanying the sodium filling in this steam generator is also based on exactly the same principle as shown in FIG. 1.

〔Effect of the invention〕

According to the present invention, a gas space of a predetermined volume can be created within a steam generator without installing new accessory equipment such as an overflow system or a cover gas system.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a schematic diagram of a steam generator according to an embodiment of the present invention;
The figure is a schematic diagram of a steam generator according to another embodiment of the present invention, Figure 3 is a typical secondary main cooling system diagram of a fast breeder reactor, and Figure 4 is a diagram of a typical steam generator of a fast breeder reactor. The schematic diagram, FIG. 5, is a schematic diagram of a conventional steam generator with a gas space. DESCRIPTION OF SYMBOLS 1...Heat transfer tube, 2...Outer shell, 3...Sodium inlet nozzle, 4...Thorium outlet nozzle, 5...
gas vent hole. 6... Steam generator, 7... Sealed gas space, 8...
Double pipe nozzle, 9... Intermediate heat exchanger, 10... Secondary main circulation pump, 11... Hot leg piping, 12...
Water/steam system. 13... Cold leg piping, 14... Internal shroud, 15... External shroud, 16... Main body support part, 17... Water/steam header, 18... Overflow nozzle. Figure 1 ゛Blind Figure 2■ 3m Figure 1

Claims (1)

[Claims] 1. In a steam generator used in a sodium-cooled fast breeder reactor with a sodium inlet nozzle inserted inside,
A steam generator characterized in that the sodium inlet nozzle is provided with a gas vent hole.