JPH0366640B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an annular steam generator in a reactor vessel of a tank-type fast breeder reactor.

<Conventional technology> Fast breeder reactors use sodium as a coolant to increase thermal efficiency compared to light water reactors, but the high temperature of the sodium coolant causes problems in the material strength of equipment that comes into contact with the coolant. As a result, the creep effect becomes noticeable.

Furthermore, thermal stress becomes excessive due to the sudden temperature gradient distributed in the structural material.

The reactor vessel is one of the devices that make up the reactor structure, and the reactor vessel is the most important device as a coolant boundary, and it is necessary to take sufficient measures to deal with the above-mentioned strength problems due to thermal stress. There is.

However, the above-mentioned reactor vessel had a problem because the temperature change was particularly large in the portion in contact with the upper plenum (high-temperature plenum).

Therefore, the flow of sodium (coolant) in the conventional nuclear reactor vessel is as shown by the arrows in FIGS. 6a and 6b. That is, the sodium leaving the core 1 enters the steam generator 3 from the upper plenum (high temperature plenum) 7 and returns to the lower plenum (low temperature plenum) 8 as cooled sodium through heat exchange.
Sodium in the lower plenum 8 is sucked in from the lower end of the main circulation pump 2 and sent into the reactor core 1 as high-pressure sodium. At the inlet of the reactor core 1, a portion of the sodium rises along the reactor vessel 5 by the reactor wall cooling shell 6 and reaches the upper plenum 7.
The reactor vessel 5 is cooled by reactor wall cooling sodium flowing through its inner surface. 4 is a safety container.
In the reactor wall cooling shell 6, sodium in the upper plenum 7, whose temperature changes rapidly as the reactor operates, hits the reactor vessel 5, causing a temperature gradient in the plate thickness direction in the reactor vessel 5, and reducing thermal stress. It also has the function of suppressing the occurrence of thermal shock, that is, the role of preventing the application of thermal shock.

As a means of lowering the temperature of the reactor vessel 5 to a temperature range where creep is no longer a problem in terms of structural strength, for example, a sufficient reactor wall cooling flow rate is provided, or a thermal liner 9 or the like is installed in the reactor wall cooling shell 6 in contact with the upper plenum 7. Methods have been proposed to maintain the cooling capacity of the furnace wall, such as by taking heat insulation measures or by providing a gas insulation layer.

Furthermore, as shown in FIG. 7, a nuclear reactor for use in a light water reactor in which a heat transfer tube 13 for steam generation is directly disposed inside a reactor vessel 11 is disclosed in Japanese Patent Application Laid-Open No. 187894/1983. The steam heat transfer tube 13 has a function of lowering the temperature of the reactor vessel 11. In the figure, 12 indicates the core, → marks indicate the flow of primary coolant, and marks indicate the flow of secondary coolant.

<Problems to be Solved by the Invention> In the case of the structure shown in FIG. 6 above, the reactor wall cooling flow rate itself becomes an ineffective flow rate in terms of thermal efficiency as a nuclear reactor, which causes a reduction in plant efficiency. Therefore, from the viewpoint of maintaining high plant efficiency, there are restrictions on taking an excessively large furnace wall cooling flow rate. Therefore, in order to maintain the temperature of the reactor vessel 5 as low as necessary with a small amount of flow rate for cooling the reactor wall, the upper plenum 7
Sufficient heat insulation measures are required for the furnace wall cooling shell 6 that is in contact with the furnace wall, but this results in the problem of increasing the amount of material or complicating the structure of the furnace wall cooling shell 6.

In addition, the structure shown in Figure 7 above is suitable for small light water reactors such as heat supply reactors, small power reactors, and marine reactors, and the primary coolant exchanges heat with the secondary coolant through natural circulation without using a pump. The purpose of this is to rationalize the heat exchanger system by
It is unsuitable for fast breeder reactors where the temperature of the secondary coolant is higher than that of light water reactors.

The present invention was made in view of the above-mentioned circumstances, and it not only streamlines the heat exchanger system, but also actively adopts a nuclear reactor vessel's temperature reduction and heat shield function for the purpose of protecting the reactor vessel. It is an object of the present invention to provide an annular steam generator within a furnace vessel.

<Means for Solving the Problems> Therefore, the in-vessel annular steam generator of the present invention is constructed between two concentric cylindrical shells arranged inside the reactor vessel in the upper reactor plenum. At least two sets of arc-shaped heat exchanger tubes each consisting of an outer tube and an inner tube are housed. The coolant in the upper plenum is stored below the upper part of the double concentric cylindrical shell. The air flows through the upper air heat transfer tube to the lower plenum.

<Function> When arranging heat transfer tubes consisting of an outer tube and an inner tube of an annular steam generator in an arc shape around the entire inner circumference of the reactor vessel, an outer tube serving as a water supply pipe is placed on the reactor vessel side. Since the inner tube, which is a steam tube, is disposed inside the reactor vessel, the temperature on the reactor vessel side can be particularly reduced by removing heat from the heat transfer tube of the annular steam generator. Furthermore, by dividing the heat exchanger tube in the circumferential direction, the temperature can be further reduced.

<Example> Fig. 1a is a plan view showing an embodiment of the in-vessel annular steam generator of the present invention, with one-half of the reactor sectioned away, and Fig. 1b is a cross-sectional view of A--A in the same figure. 2 is a longitudinal sectional view of a nuclear reactor according to an embodiment of the present invention, FIG. 3 is a sectional view taken along line B-B of FIG. FIG. 5a is a vertical cross-sectional view of a triple tube used as a heat exchanger tube, and FIG. 5b is a cross-sectional view of the same.

The reactor vessel 22 houses a reactor core 24, a circulation pump 27, and an annular steam generator (hereinafter referred to as an annular SG) 35.

The core support structure 25 includes the core 24 and the circulation pump 2.
7 and annular SG35 are vertically and horizontally supported.

The roof slab 32 supports the water system headers (water supply header 33, steam header 34, intermediate header 40), core upper mechanism 38, and circulation pump 27, and serves as various shields.

The annular SG 35 is connected to equipment that has a function of detecting whether or not the heat exchanger tube 39 is damaged.
Helium gas inlet line 36a, outlet line 3
6b, and a helium gas plenum 36 is provided in the water system header.

The annular SG 35 inside the reactor vessel 22 is composed of a cylindrical inner shell 28, a cylindrical outer shell 30, a heat transfer tube 39, a water supply header 33, a steam header 34, and an intermediate header 40. In the case of this embodiment, as shown in FIG. A large number of multiple pipes are connected from the water supply header 33 to the intermediate header 40, and the inner pipe 39b
The intermediate header 40 is installed inside the outer tube 39a.
A large number of multiple pipes are connected from the steam header 34 to the steam header 34. The heat exchanger tube 39 is connected to the heat exchanger tube support 2
9, and arranged so as to be routed horizontally around the arcuate SG 35. In addition to arranging the effective heat transfer area of the arcuate SG 35 in the most efficient manner in terms of space, the reactor vessel 22 is 22
It has two functions: as a heat shield to maintain low temperatures and to alleviate thermal shock.

Note that the heat exchanger tubes 39 used are of known high reliability (multilayer tubes) in order to prevent sodium-water reaction accidents, and replacement of the heat exchanger tubes during the life of the plant is not considered.

Next, I will explain from the systematic aspect.

The circulation path of the sodium cooling system is such that the sodium in the upper plenum 23b that has exited the core 24 passes through the flow weir at the upper part of the cylindrical inner shell 28 and passes through the heat exchanger tube support 2.
9, the tube bundle of heat exchanger tubes 39 routed horizontally is lowered, and the lower plenum 23 is lowered from its lower end.
a, enters the circulation pump 27, and enters the core inlet piping 37.
After that, it returns to the core 24 again.

On the other hand, in the water system, water enters the water supply header 33 from the water supply line 33a, passes through the outer pipe 39a of the heat transfer tube 39 disposed on the reactor vessel 22 side, and passes through the intermediate header 40.
The heat exchanger tubes 3 that entered the reactor core 24 side once again
The heated steam passes through the inner pipe 39b of No. 9 and is sent to the turbine via the steam header 34 and the steam line 34a.

The multiple pipes mentioned above may be a double pipe as shown in FIG. 4 or a triple pipe as shown in FIGS. 5a and 5b.

The double tube shown in Fig. 4 has an outer tube 51 for flowing sodium to the outside, and an inner tube 52 for flowing water or steam to the inside.
The gap 53 between the inner and outer tubes is
The gap 53 is filled with highly conductive sodium, and the end of the gap 53 is sealed with a thin cover 54. Note that it is also conceivable to flow helium gas into the gap 53 for leak detection. Figure 5 a, b
The triple tube shown in Figure 5 is an outer tube through which sodium flows outside.
5. Consisting of an inner pipe 56 through which water or steam flows inside, and a central pipe 57 that interconnects the inner and outer pipes,
A plurality of grooves 58 serving as fluid passages are provided between the inner tube 56 and the central tube 57 in the longitudinal direction of the tubes.

The double-pipe or triple-pipe space 36 corresponds to the helium gas plenum 36 in FIG. 1b, and supplies helium gas from the helium gas inlet line 36a.
The helium gas is taken out from the helium gas outlet line 36b. Inner tube 52, 56 or outer tube 51, 5
If an abnormality such as a crack occurs in the double tube filled with sodium as shown in Fig. 4, the thin cover 54 will break, so the abnormality can be detected by sampling the gas from the helium gas plenum 36, or if the double tube is filled with sodium, the thin cover 54 will break. If there is no such gap, an abnormality can be detected by sampling the gas in the helium gas plenum 36 communicating with the gap 53. Fifth
In the case of the triple tube shown in FIGS. a and b, the presence or absence of abnormalities such as cracks in the inner and outer tubes can be detected by sampling the gas in the helium gas planer 36, which is a space communicating with the groove 58.

<Effects of the Invention> According to the annular steam generator in a reactor vessel of the present invention described in detail above, the following effects are achieved.

The annular SG heat transfer tube is housed inside the reactor vessel,
By routing the upper air heat exchanger tubes horizontally,
Compared to the conventional shell-and-tube type SG (steam generator), it is much easier to secure an effective heat transfer area.

The structure consisting of a cylindrical inner shell, a heat transfer tube, and a cylindrical outer shell performs low temperature maintenance and heat shield functions to protect the reactor vessel, thereby increasing the reliability of the structural strength of the reactor vessel itself. is significantly improved.

From the perspective of low-cost plant design, the required space in the reactor structure can be minimized by simplifying the arrangement of the top surface of the roof slab and rationalizing the reduction of the reactor vessel, making it possible to reduce costs including the reduction of the containment vessel.

[Brief explanation of drawings]

FIG. 1a is a plan view showing one embodiment of the in-vessel annular steam generator of the present invention, with a half of the reactor cut away; FIG. 1b is a sectional view taken along the line A-A in the same figure; Second
The figure is a longitudinal cross-sectional view of a nuclear reactor according to an embodiment of the present invention.
The figures are a cross-sectional view taken along line B-B in Figure 1b, Figure 4 is a vertical cross-sectional view of a double tube used as a heat exchanger tube, Figure 5a is a vertical cross-section of a triple tube used as a heat exchanger tube, Figure 5b is a cross-sectional view of the same, Figure 6a is a nuclear reactor with a built-in conventional steam generator, and Figure 6b is a cross-sectional view taken along line CC in Figure 6b, and Figure 6b is a nuclear reactor with a built-in conventional steam generator. FIG. 7 is a vertical cross-sectional view of a nuclear reactor vessel, and FIG. 7 is a vertical cross-sectional view of a small nuclear reactor for a light water reactor incorporating a conventional steam generator. 4,21...Safety vessel, 5,11,22...Reactor vessel, 7,23b...Upper plenum, 8,2
3a... lower plenum, 1, 12, 24... core, 28... cylindrical inner shell, 29... heat exchanger tube support, 30... cylindrical outer shell, 32...
Roof slab, 33... Water supply header, 34... Steam header, 35... Annular steam generator, 39...
Heat exchanger tube, 39a... outer tube, 39b... inner tube,
40...Middle header.

Claims (1)

[Claims] 1 At least two sets of arc-shaped heat transfer tubes consisting of an outer tube and an inner tube are housed between double concentric cylindrical shells arranged inside the reactor vessel in the upper reactor plenum, and the heat transfer tubes are installed on the roof slab. an outer pipe formed of a large number of pipes communicating from the water supply header to the intermediate header, and a large number of pipes stored inside the outer pipe and communicating from the intermediate header to a steam header provided inside the water supply header. An annular steam generator in a nuclear reactor vessel, characterized in that the coolant in the upper plenum flows from above the double concentric cylindrical shell to the lower plenum below the double concentric cylindrical shell through the heat transfer tube.