JPS6273197A - Fast breeder 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 [Technical Field of the Invention] The present invention relates to a fast nuclear reactor equipped with a cooling structure for ensuring the integrity of a reactor vessel.

[Technical background of the invention]

In general, a fast breeder reactor has a core and a primary coolant (
This primary coolant is circulated through the reactor core and heated by the nuclear reaction of the nuclear fuel in the reactor core.

This heated primary coolant is led to an intermediate heat exchanger to exchange heat with a secondary coolant (usually liquid sodium), and then the secondary coolant is led to an evaporator to exchange heat with water. The superheated steam obtained here is sent to the turbine for driving the starter.

By the way, in this type of fast breeder reactor, it is necessary to design the reactor vessel in such a way that it can withstand high temperatures. It is also necessary to guide the high temperature primary coolant that has passed through the core to the medium ray heat exchanger so as not to lower the temperature.

Therefore, in recent years, a fast breeder reactor having a configuration as shown in FIG. 3 has been developed.

Figure 3 shows the schematic configuration of a tank-type fast breeder reactor.
1 in the figure is the core 2 and the primary coolant (usually liquid sodium)
The upper opening of the furnace vessel 1 is shielded by a roof slab 4. Also, furnace vessel 1
A high-temperature coolant storage container 5 is disposed inside the reactor, supported by a core support structure 6 that supports the reactor bottom 2. This storage vessel 5 has a gap 7 between the upper half 5A and the inner circumferential surface of the reactor vessel 1, has a lower half 5B with a small diameter, and has its lowermost end attached to the core support structure 6. A conical portion 5C having a downward slope toward the center is provided between the half portion 5A and the lower half portion 5B.

A passage forming plate 8 is disposed inside the furnace vessel 1 along the inner surface of the furnace vessel 1, and a low temperature coolant passage 9 is formed between the inner surface of the furnace vessel 1 and the passage forming plate 8. has been done. The flow path forming plate 8 has a communication port 10 located directly below the core 2, and the upper part of the peripheral wall is a double wall (inner peripheral wall 11.A, outer peripheral wall 11B).
The annular area (downcomer) composed of its double walls as
12 is opened to a low temperature coolant storage space 15.

Further, between the lower end of the double wall of the flow path forming plate 8 and the core support structure 6, there is an annular partition wall 13 centered around the core 2.
is attached. This partition wall 13 is located on the outside of the high temperature coolant storage container 5 and is located at the conical portion 5C of the high temperature coolant storage container 5.
An annular coolant retention space 14 is formed between the reactor vessel 1 and a low-temperature coolant storage space 15 that communicates with the lower end of the reactor core 4.

Further, the roof slab 4 supports a primary coolant circulation pump 16 and an intermediate heat exchanger 17. These circulation pumps 16... and heat exchangers 17...
* are arranged alternately on the circumference around the core 2.

The primary coolant circulation pump 16 operates in the coolant retention space 14.
It passes through the inside of the cylinder 18 provided on the conical part 5C and further penetrates the partition wall 13 to connect to the low temperature coolant storage space 1.
It has been introduced in 5. The suction side communicates with the coolant retention space 14, and the discharge side communicates with the low temperature coolant storage space 15.
The primary coolant 3 in the coolant retention space 14 is sent into the low-temperature coolant storage space 15 by communicating with the coolant storage space 14 .

Further, the intermediate heat exchanger 17 has a primary coolant inflow side located within the high temperature coolant storage container 5 and a primary coolant outflow side communicated with the low temperature coolant storage space 15 . The primary coolant 3 is stored in the low temperature coolant storage space 1.
It is configured to be distributed to 5.

Next, the operation of the tank-type fast breeder reactor configured as described above will be explained.

Now, when the primary coolant 3 in the low temperature coolant storage space 15 is pressurized by the primary coolant circulation pump 16, the primary coolant 3 in the low temperature coolant storage space 15 passes through the core 2 as shown by arrow a. , is heated by the heat generated by the nuclear reaction of the uranium fuel in the reactor core 2 and reaches the high temperature coolant storage container 5,
It flows into the intermediate heat exchanger 17 as shown by the arrow. here,
The primary coolant 3 transfers heat to the secondary coolant, is cooled and flows out into the low temperature coolant storage space 15 as shown by arrow C, and is circulated again through the core 2 into the high temperature coolant storage vessel 5. Repeat.

On the other hand, the primary coolant 3 in the low-temperature coolant storage space 15 pressurized by the primary coolant circulation pump 16 moves up the low-temperature coolant flow path 9 as shown by arrow d, and crosses the outer circumferential wall 11B of the double wall portion. As shown by arrow e, the coolant crosses over and flows between the inner and outer peripheral walls 11A and 118, and further flows out into the low-temperature coolant storage space 15.

By the way, in the tank-type fast breeder reactor configured as above, the high temperature primary coolant that has passed through the reactor core 2 and is heated is stored in the high temperature coolant storage container 5, and the high temperature primary coolant that has passed through the reactor core 2 is stored in the reactor vessel 1. Since the previous low temperature primary coolant comes into contact, the furnace vessel 1 will be kept at a relatively low temperature. Therefore, the design of the furnace vessel 1 can be facilitated. Furthermore, since a partition wall 13 is provided on the outside of the high-temperature coolant container 5 to form a coolant retention space 14, the primary coolant present in this space 14 is transferred to the high-temperature primary coolant in the high-temperature coolant container 5. It functions as a heat shield between the low-temperature primary coolant in the low-temperature coolant storage space 15 and prevents the temperature of the coolant 3 in the high-temperature coolant storage container 5 from decreasing.

[Problems with background technology]

Next, the heat flow characteristics of the coolant in the low temperature coolant flow path 9 and the downcomer 12, which form the coolant flow path for cooling the reactor vessel 1 in the conventional fast breeder reactor, will be explained.

The temperature of the coolant rising in the low temperature coolant flow path 9 is:

Although it is determined by the balance between the heat input from the downcomer 12 and the heat dissipated from the furnace vessel 1 to the outside space, the temperature generally increases toward the downstream of the flow path, as shown in FIG.

Therefore, in the low-temperature coolant flow path 9, the temperature distribution becomes such that the coolant temperature decreases in the direction of gravity, resulting in a thermo-hydraulic stable condition.

On the other hand, the temperature of the coolant flowing down the downcomer 12 is determined by the heat input from the high temperature primary coolant 3 held in the high temperature coolant container 5 and the heat radiation to the coolant flowing through the low temperature coolant flow path 9. In this case as well, the temperature increases as the flow path becomes downstream (in the direction of gravity) (see FIG. 4). However, in this case, the coolant temperature will increase in the direction of gravity, so
Thermo-hydrodynamically unstable conditions arise.

This unstable condition becomes especially noticeable during a reactor trip when the coolant flow rate is small.

When this unstable condition occurs, the coolant may not descend uniformly through the downcomer 12, but may form a flow pattern in which it descends as a whole while generating large natural convection in the circumferential direction of the downcomer 12.

If such convection occurs, the outer peripheral wall 11B.

Furthermore, a temperature difference may occur in the circumferential direction of the furnace vessel 1, which may pose a problem in ensuring the integrity of the structure (see FIG. 5).

[Purpose of the invention]

The present invention was made in view of the above circumstances, and its purpose is to:
In a fast reactor in which an inner peripheral wall and an outer peripheral wall are provided in the reactor vessel to circulate a low-temperature coolant to cool the reactor vessel, the circumferential direction between the reactor wall and the inner peripheral wall and between the inner peripheral wall and the outer peripheral wall is An object of the present invention is to provide a fast nuclear reactor that prevents temperature distribution from occurring in the circumferential direction of a reactor vessel by localizing coolant convection.

[Summary of the invention]

In order to achieve the above object, the present invention provides an inner circumferential wall and an outer circumferential wall in the furnace vessel, and a space between the furnace vessel and the outer circumferential wall.

In a fast reactor in which the reactor vessel is cooled by circulating coolant between the outer circumferential wall and the inner circumferential wall, there are ) is provided with vertical ribs to localize circumferential natural convection.

[Embodiments of the invention]

An explanation will be given with reference to one embodiment of the present invention.

FIG. 1(a) is a top view of one embodiment of the present invention.
Figure (b) is a longitudinal sectional view of a part thereof.

As shown in these figures, the only difference from the conventional fast reactor shown in Fig. 3 already explained is that vertical ribs are installed between the reactor vessel and the outer circumferential wall, and between the outer circumferential wall and the inner circumferential wall. Since there are no other differences in the configuration, the same components will be designated by the same reference numerals and detailed explanations thereof will be omitted.

As shown in FIGS. 1(a) and (b), an outer circumferential wall 2 and an inner circumferential wall 3 are provided inside the furnace vessel 1, and the furnace vessel 1 and the outer circumferential wall 2 are provided inside the furnace vessel 1.
The coolant is circulated between the outer circumferential wall 2 and the inner circumferential wall 3 (downcomer 9).

Vertical ribs 5 having communicating holes 7 are installed in the low temperature coolant flow path 8 and the downcomer 9 at equal intervals in the circumferential direction.

Next, the operation of this embodiment will be explained. As already mentioned, in the downcomer 9, a thermo-hydraulic unstable state occurs in which the temperature of the coolant increases in the direction of gravity, and this tendency is particularly exacerbated when the flow rate is low, such as during a nuclear reactor trip.

However, according to this embodiment, since the circumferential flow is obstructed by the vertical ribs 5, large-scale circumferential convection (vortex generation) as in the case where the vertical ribs 5 are not generated does not occur. To explain this in more detail with reference to FIG. 2, for example, the downcomer 9 between the inner circumferential wall 2 and the outer circumferential wall 3 is partitioned in the circumferential direction by vertical ribs 5, so that the circumferential convection f is Convection occurs only locally within the area between the ribs 9, and circumferential convection on a large scale is inhibited, making it possible to prevent asymmetric temperature distribution from occurring in the circumferential direction of the furnace stand iS. Become.

〔Effect of the invention〕

As explained above, according to the present invention, by localizing circumferential natural convection between the reactor vessel and the outer circumferential wall and between the outer circumferential wall and the inner circumferential wall in the reactor, an asymmetric temperature distribution occurs in the circumferential direction of the reactor vessel. It is possible to prevent this from happening.

・1. Easy drawing! 1 (explanation Fig. 1<a) is a top view of an embodiment of the present invention, Fig. 1(b)
) is a partial vertical cross-sectional view of the same figure (a), FIG. 2 is an enlarged cross-sectional view for explaining the present invention in detail, FIG. FIG. 5 is a diagram for explaining the temperature distribution in the reactor and the occurrence of natural convection in the reactor of the fast breeder reactor shown in FIG. 3, respectively.

”−・furnace vessel 2.Outer wall 3 Inner peripheral wall 5. Vertical ribs 7...Communication hole 8. Low temperature coolant flow path 9. Downcomer Agent: Patent Attorney Noriyuki Chika Same as Hiroshi Sanmata Rod 1 diagram (b) Figure 2 Figure 3 31 eel Figure 4 Figure 5

Claims (2)

[Claims] (1) High-temperature coolant storage that is arranged within the reactor vessel with a gap between the reactor vessel containing the reactor core and primary coolant and the inner surface of the reactor vessel to accommodate the high-temperature coolant that has passed through the reactor core. A coolant retention space is formed between the container and the high-temperature coolant container arranged outside the high-temperature coolant storage container, and an outer peripheral wall arranged inside the furnace container and the furnace wall are cooled. In a fast nuclear reactor, an annular space between the reactor wall and the outer circumferential wall and between the outer circumferential wall and the inner circumferential wall,
A fast nuclear reactor characterized by vertical ribs installed at equal intervals in the circumferential direction. (2) The fast nuclear reactor according to claim 1, wherein the vertical rib has a plurality of small holes.