JPH03257398A - Tank type fast breeder reactor - Google Patents

Abstract

PURPOSE:To mitigate thermal stresses of members and to keep structural integrity by elimianating a baffle plate which is, used to be, essentially required, and by forming, in stead, a gas space at least at an upper surrounding wall part. CONSTITUTION:At an upper half part 5A of a housing vessel of high temperature coolant, a plate 24 forming a gas space is placed, and its upper and lower ends are fit to an outer circumference part of the upper half part 5A to form a ring shaped gas space 25 internally. This space 25 is connected to a cover gas atmosphere which is sealed into an upper end part of a reactor vessel 1 through a gas vent hole 26 on a top part of the space. Under this constitution, temperature of a region G is around 380 deg.C and of a region E is around 530 deg.C during normal operation. Accordingly, by setting appropriately width of a region F which is the space 25, and by making the region function as a thermal insulating material, temperature of the region F can be set to be around 450 to 480 deg.C. Consequently, temperature difference to thickness direction of the plate 24 forming the gas space, becomes some 70 to 100 deg.C and the temperature difference can be reduced and also its structure can be simplified by elimination of a baffle plate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a fast breeder reactor equipped with a cooling structure for ensuring the integrity of the reactor vessel.

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

The heated primary coolant is guided to an intermediate heat exchanger to exchange heat with a secondary coolant (also typically liquid sodium), and the secondary coolant is further guided to an evaporator to exchange heat with water. The superheated steam obtained here is configured to be sent to a turbine for driving a generator.

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 an intermediate 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.
In the figure, reference numeral 1 denotes a reactor vessel housing a reactor core 2 and a secondary coolant (commonly known as liquid sodium) 3, and an upper opening of this reactor vessel 1 is shielded by a roof slab 4. Further, a high-temperature coolant storage container 5 is disposed inside the reactor vessel 1 and is supported by a core support structure 6 that supports the reactor core 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. Half part 5A and lower half part 5
A conical portion 5 with a downward slope toward the center is provided between B and B.
It is configured to change C to H.

A flow path forming plate 8 is disposed inside the furnace vessel 1 along the inner surface of the furnace vessel, and a low temperature coolant flow path 9 is formed between the inner surface of the furnace vessel 1 and the flow path forming plate 8. has been done. The flow path forming plate 8 has a communication port 10 located directly below the core 2, and has a double wall (inner peripheral wall 11A1 outer peripheral wall 11B) at the upper part of the peripheral wall, and an annular region (downcomer) constituted by the double wall. 12 is opened to a low temperature coolant storage space 15. A baffle plate 18, which will be described in detail later, is arranged inside the upper end of this annular region 12.

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

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 19 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 is communicated with the low-temperature coolant storage space 15, and the discharge side is connected with the reactor core 2, so that the primary coolant 3 in the low-temperature coolant storage space 15 is fed into the core 2 as shown by the arrow. ing.

Further, the intermediate heat exchanger 17 has a secondary coolant inflow side located in 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 inside 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 secondary 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. The uranium fuel 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 secondary 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 secondary coolant circulation pump 16 is
Entering from
Climb over the outer circumferential wall 11B of the double wall portion as shown by arrow e and climb the mountain/outer circumferential wall 11. It flows into between A and IIB, and further flows out into the low temperature coolant storage space 15.

By the way, in the tank-type fast breeder reactor configured as described above, the high-temperature secondary coolant that has passed through the reactor core 2 and has been superheated is accommodated in the high-temperature coolant storage container 5, and the reactor core 2 is placed in the reactor container 1. The reactor vessel 1 will be kept at a relatively low temperature as the cold-secondary coolant will come into contact with it before it passes through.

Therefore, the design of the furnace vessel 1 can be facilitated. Further, on the outside of the high-temperature coolant container 5, a partition wall 13 is provided to form a coolant retention space 14, so that the primary coolant existing in this space 14 is transferred to the high temperature inside the high-temperature coolant container 5.
It functions as a heat shield between the secondary coolant and the low-temperature secondary 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.

Next, the function of the baffle plate 18 in the furnace wall cooling structure is as follows.
This will be explained with reference to FIGS. 4(a) and 4(b). FIG. 4(a) shows the state around the reactor wall cooling channel during steady operation, and FIG. 4(b) shows the state around the reactor wall cooling channel immediately after a reactor trip.

During steady operation, the temperature in area A is almost the same as that of the primary cooling (approximately 530°C), and the temperature in area C is slightly higher than the coolant temperature in the low-temperature coolant flow path 9 (approximately 380°C). .

By the way, at the time of a reactor trip, the liquid level in the C region rises rapidly, so if the baffle plate 18 is not installed, the liquid level in the upper part of the inner circumferential wall 11A will suddenly rise by about 150° C. ( A temperature difference of -530° C. to 380° C.) is generated, which poses a major problem in ensuring the structural integrity of the inner peripheral wall 11A.

On the other hand, when the baffle plate 18 is installed to form a region B between the baffle plate 18 and the inner circumferential wall 11A, the temperature in the region B becomes approximately 430° C. during steady operation. Therefore, it is possible to reduce the temperature difference in the thickness direction of the upper part of the inner circumferential wall 11A to about 100° C. during a reactor trip.

(Problem to be Solved by the Invention) In the conventional tank-type fast breeder reactor, the second coolant 3
At a position near the liquid level, the outer peripheral wall 11B, the baffle plate 18,
The upper half 5A of the high-temperature coolant storage container 5 will be composed of four thin-walled structures, and the thin-walled flow path forming plate 8 will also be installed at the bottom of the furnace container 1. As the amount of materials increases, the seismic design becomes more complex.

The present invention has been made in consideration of these points, and an object of the present invention is to provide a tank-type fast breeder reactor that can simplify the reactor wall cooling structure and reduce the amount of material. do.

[Structure of the invention]

(Means for Constructing the Problem) As a means for achieving the above object, the present invention provides a reactor vessel in which a reactor core and a primary coolant are housed, a lid for closing an upper end opening of the reactor vessel, and a lid for closing an upper end opening of the reactor vessel. a high-temperature coolant storage container that is disposed on the outside of the reactor vessel with a gap between the inner surface and the high-temperature coolant container that contains the high-temperature coolant that has passed through the reactor core; An annular low-temperature coolant flow path is formed between the low-temperature coolant flow path and the high-temperature coolant container, and the low-temperature coolant flow path overflows from the upper end of the low-temperature coolant flow path. A coolant retention space into which the flowing coolant is guided, and an annular gas space formed in at least the upper peripheral wall of the high-temperature coolant storage container and whose interior is filled with a cover gas sealed in the upper end of the furnace container. The feature is that each is provided separately.

(Function) In the tank-type fast breeder reactor according to the present invention, the low-temperature coolant before passing through the reactor core is supplied to the low-temperature coolant channel to cool the reactor wall. In this cooling structure, the base liquid is introduced into the coolant retention space from the upper end of the low-temperature coolant flow path.

This coolant retention space is not provided with a baffle plate, which was conventionally essential, and the structure is simplified. In addition, the increase in temperature difference due to the omission of the baffle plate is
This problem is solved by forming a gas space in at least the upper peripheral wall of the high-temperature coolant storage container and making this gas space function as a heat insulating material.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of a tank-type fast breeder reactor according to the present invention. In the figure, reference numeral 1 denotes a reactor vessel containing a reactor core 2 and a primary coolant 3, and an upper opening of this reactor vessel 1. teeth,
It is closed by a roof slab 4.

Additionally, inside the furnace vessel 1, as shown in FIG.
A high-temperature coolant storage container 5 is supported by a core support structure 6 that supports the reactor core 2 .

As shown in FIG. 1, this high-temperature coolant storage container 5 has a gap 7 between the upper half 5A and the inner circumferential surface of the furnace vessel 1, and has a lower half 5B with a small diameter and a lowermost end thereof. It is attached to the core support structure 6, and is configured to have a conical part 5C between the upper half part 5A and the lower half part 5B, which slopes downward toward the center.

The upper inner periphery of the furnace vessel 1 is shown in FIGS. 1 and 2 (a).
, as shown in (b), a peripheral wall 20 is arranged to form an annular low-temperature coolant flow path 21 between the peripheral wall 20 and the furnace wall,
The low-temperature coolant flow path 21 is supplied with the low-temperature primary coolant 3 from the lower part of the core support structure 6 via a pipe 22 .

As shown in FIG. 1, an annular partition wall 13 is installed between the lower end of the low-temperature coolant channel 21 and the core support structure 6, with the core 2 at its center. The partition wall 13 is located below the outside of the high-temperature coolant container 5 and forms an annular coolant retention space 4 between the high-temperature coolant container 5 and the conical portion 5C. A low-temperature coolant storage container 15 communicating with the lower end of the core 2 is formed between the reactor core 2 and the reactor core 2 . As shown in FIG. 1, the coolant retention space 14 communicates with the low-temperature coolant storage container 15 via a flow port 23 provided at the outer peripheral edge of the partition wall 13.

On the other hand, as shown in FIG.
are supported, respectively, and these secondary coolant circulation pumps 16 and intermediate heat exchangers 17 are arranged alternately on the circumference around the core 2.

As shown in FIG. 1, each secondary coolant circulation pump 16 has a
The coolant is introduced into the low-temperature coolant storage space 15 through a cylindrical body 19 provided on the conical portion 5C in communication with the coolant retention space 14, and further through the partition wall 13. The discharge side communicates with the reactor core 2, and the primary coolant 3 in the low-temperature coolant accommodation space 15 is
It is designed to be sent to the reactor core 2.

Moreover, each intermediate heat exchanger 17 has -
The secondary coolant inflow side is located within the high-temperature coolant storage container 5, and the secondary cooling shrine outflow side is located within the low-temperature coolant storage space 15. After the primary cooling moon 3 is lowered in temperature by exchanging heat with the secondary cooling moon, it is made to flow down into the low-temperature coolant storage space 15.

On the other hand, as shown in FIGS. 1 and 2(a) and (b), a gas space forming plate 24 is installed in the upper half 5A of the high-temperature coolant storage container 5, and the upper and lower ends thereof are is joined to the outer periphery of the upper half 5A to form an annular gas space 25 inside. This gas space 25 communicates with a cover gas atmosphere sealed in the upper end of the furnace vessel 1 through a gas vent hole 26 at the top thereof.

Further, on the lower surface of the roof slab 4, as shown in FIG. ,
It is inserted into the cooling storage container 5 while maintaining an appropriate radial gap.

Next, the operation of this embodiment will be explained.

- When the primary coolant 3 in the low temperature coolant storage space 15 is pressurized by the secondary coolant circulation pump 16, the primary coolant 3 in the low temperature coolant storage space 15 passes through the core 2 from below to above, It 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. and - next coolant 3
transfers heat to the secondary coolant, is cooled and flows out into the low-temperature coolant storage space 15, and repeats the circulation through the core 2 into the high-temperature coolant storage container 5.

On the other hand, a part of the primary coolant 3 in the low-temperature coolant storage space 15 pressurized by the secondary coolant circulation pump 16 is transferred to the pipe 2
1 to the low-temperature coolant flow path 21 to cool the furnace wall. The primary cooling shrine 3 overflowing from the upper end of the low-temperature coolant channel 21 is guided to the coolant retention space 14, and the high-temperature primary coolant 3 in the high-temperature coolant storage container 5 and the low-temperature coolant storage space 15 The temperature of the primary coolant 3 in the high-temperature coolant storage container 5 is prevented from decreasing by providing heat insulation between the primary coolant 3 and the low-temperature primary coolant 3 in the high-temperature coolant container 5 . The primary coolant 3 in the coolant retention space 14 is ultimately returned to the low-temperature coolant storage space 15 via the flow port 23 .

FIG. 2(a) shows the state around the reactor wall cooling channel during steady operation, and FIG. 2(b) shows the state around the reactor wall cooling channel immediately after a reactor trip.

During steady operation, region G is approximately 380°C and region E is approximately 53°C.
It is 0°C. Therefore, by appropriately setting the width of the region F, which is the gas space 25, and making it act as a heat insulating material, it becomes possible to set the region F to approximately 450° C. to 480° C. As a result, the gas space forming plate 24 at the time of reactor trip
The temperature difference in the wall thickness direction is approximately 0°C to 100°C, and in the case of the conventional structure using the baffle plate 18 (Fig. 4 (a)
), it is possible to reduce the temperature difference to a degree equal to or greater than (see (b)). Moreover, since the baffle plate 18 can be omitted, the structure can be greatly simplified.

Further, since the lower part of the core support structure 6 and the low-temperature coolant channel 21 are connected by the piping 22, the amount of material can be reduced and the structure can be further simplified.

Further, since the steady rest plate 27 is provided on the lower surface of the roof slab 4 in close proximity to the high temperature coolant container 5, the load during an earthquake can be reduced.

In the above embodiment, a case has been described in which the gas space 25 is formed only in the upper half portion 5A of the high-temperature coolant storage container 5, but it may be expanded to the conical portion 5C.

〔Effect of the invention〕

As explained above, the present invention eliminates the conventionally essential baffle plate and instead forms a gas space in at least the upper peripheral wall of the high-temperature coolant storage container. Not only can the stress be relaxed and the soundness of the structure be ensured, but also the structure can be simplified and the amount of material can be reduced.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing a tank-type fast breeder reactor according to an embodiment of the present invention, FIG. 2(a) is an explanatory diagram showing the state around the reactor wall cooling channel during steady operation, (b) is an explanatory diagram showing the state around the reactor wall cooling channel immediately after a reactor trip, Figure 3 is a vertical cross-sectional view showing a conventional tank-type fast breeder reactor, and Figure 4 (a) is during steady operation. FIG. 4B is an explanatory diagram showing the state around the conventional reactor wall cooling channel. FIG. 4(b) is an explanatory diagram showing the state around the conventional reactor wall cooling channel immediately after a reactor trip. 1... Reactor vessel, 2... Reactor core, 3... -Secondary coolant,
4... Roof slab, 5... High temperature coolant storage container,
14... Coolant retention space, 15... Low temperature coolant storage space, 21... Low temperature coolant flow path, 22... Piping, 2
5... Gas space, 26... Gas vent hole, 27...
Steady rest. (0) (b) Figure (0) (b) Figure

Claims (1)

[Claims] Arranged in the reactor vessel with a gap between a reactor vessel in which the reactor core and primary coolant are housed, a lid that closes the upper end opening of the reactor vessel, and the inner surface of the reactor vessel. a high-temperature coolant storage container that accommodates the high-temperature coolant that has passed through the reactor core; and an annular shape that is formed in at least the upper peripheral wall of the reactor vessel and that is supplied with the low-temperature coolant before passing through the reactor core to cool the reactor wall. a coolant retention space formed between the low temperature coolant flow path and the high temperature coolant storage container, into which the coolant overflowing from the upper end of the low temperature coolant flow path is guided; A tank-type high-speed breeder characterized by comprising an annular gas space formed in at least the upper peripheral wall of the high-temperature coolant storage container, the interior of which is filled with cover gas sealed in the upper end of the reactor container. Furnace.