JPH05119181A - Fast breeder - Google Patents

Abstract

PURPOSE:To enable reduction in reactor thermal stress of a nuclear reactor by arranging a conical shell at an upper opening of a main container as upper cover and a heat insulating material outside the conical upper lid of the main container. CONSTITUTION:In a shift to a complete rated output operating condition via a high temperature standby condition from a low temperature condition of a nuclear reactor, temperature rises near the liquid surface of a hot pool 10 within the vessel 1 of the reactor, which leads a rise in temperature at a conical shell part 17 of the upper lid of the reactor vessel 1 with the transmission of radiant heat from the liquid surface of the pool 10 and by convective heat through a reactor vessel cover gas part 18. Moreover, the outside of the shell 17 is insulated from heat with a heat insulating material, hence, resulting in no large difference in temperature along the vessel 1 upward from near the liquid surface of the reactor vessel 1. In a stoppage operation with a shift to a lower temperature condition from this temperature condition-opposite from the state of a rising output in the nuclear reactor, too, this allows the conical shell part 17 of the upper liquid of the reactor vessel to follow any change in temperature near the surface of liquid metal as does at the start of operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fast breeder reactor, and more particularly to a fast breeder reactor capable of rationalizing heat resistance design of a reactor vessel.

[0002]

2. Description of the Related Art FIG. 3 shows a schematic structure of a conventional fast breeder reactor. Inside a bottomed cylindrical main vessel 1, a reactor core 2 for generating heat energy by a nuclear reaction is provided. Inside the main container 1, a plurality of main circulation pumps 4 that circulate a liquid metal (usually liquid sodium) 3 as a primary coolant, a liquid metal (not shown) (normally from a primary coolant to a secondary coolant) A primary cooling system facility including a plurality of intermediate heat exchangers 5 for transmitting heat energy to liquid sodium) is housed.

A core inlet plenum portion 6 is provided below the core 2, and the core 2 and the core inlet plenum portion 6 are provided in the main vessel 1.
It is supported by a core support 7 provided at the bottom of the inside.
An upper core mechanism 8 is arranged above the core 2. A partition wall 9 is arranged inside the main container 1.
The partition 9 divides the space inside the main container 1 into an upper hot pool 10 and a lower cold pool 11.

The plurality of main circulation pumps 4 and the plurality of intermediate heat exchangers 5 are arranged in the main container 1 at equal intervals in the circumferential direction. Also, at the lower end of the main circulation pump 4, piping in the furnace
12 are connected, and the lower end of this in-core piping 12 extends from the cold pool 11 to the core inlet plenum 6. The main circulation pump 4 is surrounded by a thin-walled cylindrical body 13 extending from the lower portion of the main circulation pump 4 to the furnace piping 12. The lower end of the cylindrical body 13 is passed through the partition wall 9 and introduced into the cold pool 11. The interior communicates with the internal space of the cold pool 11.

A safety container 14 having a bottomed cylindrical shape is provided outside the main container 1 in case of a coolant leakage accident.
The fast breeder reactor configured as described above is supported by the cavity wall 16 of the reactor building via the support member 15 provided on the outer periphery of the upper portion.

Further, the upper opening of the main container 1 is closed by a roof slab 17 forming an upper lid. A cooling layer 18 is formed on the roof slab 17, and a cooling gas is circulated through the cooling layer 18 to prevent the roof slab 18 from overheating. Liquid metal is contained in the hot pool 10 and the cold pool 11 as a primary coolant, and a cover gas is filled between the liquid surface of the liquid metal 3 and the roof slab 17 to form a cover gas layer 30. Has been formed.

Next, the operation of the conventional fast breeder reactor will be described.

First, the liquid metal 3 as the primary coolant is the core 2
While passing upwards, it receives heat energy from the nuclear reaction to become high temperature and flows into the hot pool 10. Then, it flows into the intermediate heat exchanger 5 from the upper part, and the heat energy is transferred to the liquid metal as the secondary coolant to lower the temperature and flow down into the cold pool 11. On the other hand, the liquid metal 3 in the cold pool 11 is pressurized by the main circulation pump 4 and returned to the core inlet plenum portion 6 through the in-core piping 12. The liquid metal as the secondary coolant heated in the intermediate heat exchanger 5 is guided to the outside of the main container 1 and heats the steam for driving the turbine.

[0009]

In the conventional fast breeder reactor constructed as described above, the roof slab is cooled to a low temperature, while the liquid metal in the main container is in the vicinity of the liquid surface of the liquid metal in the hot pool. At high temperature, resulting in a large axial temperature drop in this region of the main vessel and a short axial length resulting in a large temperature gradient. FIG. 4 shows the temperature distribution near the liquid surface of the main vessel of such a fast reactor. Since this causes an increase in thermal stress, from the viewpoint of heat resistance, this portion of the main container at the liquid surface level A is cooled with the liquid metal of the cold pool, or a furnace wall heat protection structure is provided. There was a need.

The present invention has been made in view of the above points, and an object thereof is to provide a fast breeder reactor capable of reducing the thermal stress of the reactor wall of the reactor vessel.

[0011]

The present invention has an internal core,
The core upper part mechanism, the main circulation pump and the intermediate heat exchanger are housed, and the main circulation pump and the intermediate heat exchanger are supported by the conical upper lid of the reactor upper part, and the inside is divided into the hot pool and the cold pool by the partition wall. A main container having a cylindrical bottom and a safety container arranged to cover the outside of the main container, and a main container supporting skirt that is placed on the Bemusut of the reactor building downward from the bottom plate of the main container. In the vertically arranged fast breeder reactor, a conical shell forming an upper lid is arranged in the upper opening of the main container, and a heat insulating material is arranged outside the conical upper lid of the main container.

[0012]

According to the present invention, since the main container is supported by the lower part, it is not necessary to contact the concrete with the upper part, and it is not necessary to cool the main container cover part. Therefore, in the procedure of transitioning the reactor from the low temperature state to the rated output operation state through the high temperature standby state, the temperature rises near the liquid level of the hot pool in the reactor vessel, but the conical lid part at the top of the reactor vessel Temperature rises due to radiant heat transfer and convective heat transfer from the hot pool liquid level through the reactor vessel cover gas section, and the outside of these conical lids is thermally insulated. The temperature drop along the reactor vessel in the direction is small. Further, even in the stop operation for shifting the reactor from the high temperature state to the low temperature state, the upper lid portion of the main container can follow the temperature change in the vicinity of the liquid metal liquid surface similarly to the start-up. That is, a steep temperature gradient is not generated in the vicinity of the liquid surface of the main vessel even when the output of the nuclear reactor changes, and the thermal stress can be relaxed without introducing a special device.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a vertical sectional view showing an embodiment of a fast breeder reactor according to the present invention.

In FIG. 1, a core 2 for generating heat energy by a nuclear reaction is provided inside a main container 1 having a bottomed cylindrical shape.
Is provided. Further, inside the main container 1, a plurality of main circulation pumps 4 that circulate a liquid metal (usually liquid sodium) 3 as a primary coolant, a liquid metal (usually liquid sodium) as a primary coolant to a secondary coolant (Fig. A primary cooling system facility including a plurality of intermediate heat exchangers 5 for transmitting heat energy to (not shown) is housed.

The core 2 is supported by a core support 7 provided at the bottom of the main container 1. An upper core mechanism 8 is arranged above the core 2. A partition wall 9 is arranged inside the main container 1. The partition 9 divides the space inside the main container 1 into an upper hot pool 10 and a lower cold pool 11.

The plurality of main circulation pumps 4 and the plurality of intermediate heat exchangers 5 are arranged in the main container 1 at equal intervals in the circumferential direction. An internal pipe 12 is connected to the lower end of the main circulation pump 4, and the lower end of the internal pipe 12 extends from the cold pool 11 to the core inlet plenum 6.

A safety container 14 having a bottomed cylindrical shape is provided outside the main container 1 in case of a coolant leakage accident.
The fast breeder reactor configured as described above has a bottom plate 19 of the main vessel.
Is formed in a stepped shape so as to draw an arc serving as a downward convex portion between the main container support skirts 20 in a longitudinal section passing through the central axis of the main container 1. The main container support skirt is
It is supported by the base mat 25 of the reactor building.

The upper opening of the main container 1 is closed by a conical shell 17 forming an upper lid. The inner surface of the conical shell 17 is in contact with the reactor cover gas 18, and the heat insulating material 21 having excellent heat insulating performance is disposed on the outer surface thereof, so that the temperature of the conical shell 17 changes from the temperature near the liquid surface of the liquid metal 3. I try not to change suddenly. Also, hot pool 10 and cold pool
Liquid metal (usually liquid sodium) is contained in 11 as a primary coolant, and a cover gas is filled between the liquid surface of the liquid metal 3 and the roof slab 17.

Next, the operation of this embodiment having such a configuration will be described.

The liquid metal 3 as the primary coolant is sent to the intermediate heat exchanger 5 as in the conventional apparatus, and the liquid metal as the secondary coolant heated in the intermediate heat exchanger 5 is discharged to the outside of the main container 1. It is guided and heats steam for driving the turbine.

When the reactor is shifted from the low temperature state to the rated output operation state through the high temperature standby state, the temperature rises near the liquid surface of the hot pool 10 in the reactor vessel, but the cone of the reactor vessel top cone The shell part 17 is also the furnace container cover gas part
The temperature rises from the liquid surface of the hot pool 10 via 18 by radiant heat transfer and convective heat, and since the outside of these conical shells 17 is thermally insulated by the heat insulating material 21, it rises from the vicinity of the liquid surface of the reactor vessel. The temperature drop along the reactor vessel 1 in the direction does not increase. Further, even in the stop operation of shifting from the high temperature state to the low temperature state contrary to the increase in the output of the reactor, the conical shell portion 17 of the upper lid of the reactor vessel also follows the temperature change in the vicinity of the liquid metal liquid surface as at the time of startup. It becomes possible to do.

FIG. 2 shows the axial temperature gradient from the vicinity of the liquid metal level B of the hot pool 10 of the reactor vessel 1 to the upper side. The heat-resistant design of the reactor vessel is simplified when it is not necessary to cool the lid portion of the reactor upper portion as in the reactor structure of the present invention.

[0024]

EFFECTS OF THE INVENTION According to the present invention, the temperature gradient in the vicinity of the liquid surface of the main vessel where the severest thermal stress is generated in the conventional reactor structure becomes gentle, and the thermal stress can be reduced in the conventional type. Therefore, the furnace wall cooling device and the furnace wall heat protection structure required for this are not required, and it is possible to reduce the cost of the reactor structure, and it is necessary to install an extra device inside the main vessel in the reactor. In other words, the diameter of the main vessel can be reduced, which leads to a reduction in the size of the reactor building, which contributes to a reduction in plant construction cost.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing the structure of a fast breeder reactor according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a temperature distribution near a liquid surface of a fast breeder reactor to which the present invention is applied.

FIG. 3 is a vertical cross-sectional view showing a conventional example of a fast breeder reactor.

FIG. 4 is a characteristic diagram showing a temperature distribution near a liquid surface in a conventional fast breeder reactor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Main container 2 ... Core 3 ... Liquid metal 4 ... Main circulation pump 5 ... Intermediate heat exchanger 6 ... Core inlet plenum 7 ... Core support 8 ... Core upper mechanism 9 ... Partition 10 ... Hot pool 11 ... Cold pool 17 … Conical shell part 18… Furnace container cover gas part 20… Main container support skirt 21… Insulation

Claims (1)

[Claims] 1. A bottomed cylindrical main container having a core, an upper core mechanism, a main circulation pump, and an intermediate heat exchanger housed therein, and having a partition for partitioning the interior into a hot pool and a cold pool, and this main container. In a fast breeder reactor having a safety container arranged so as to cover the outside of the main container, the main container supporting skirt is hung vertically from the bottom plate of the main container and is placed on the base mat of the reactor building. A fast breeder reactor characterized in that the upper opening is closed by a conical shell forming an upper lid, the inner surface of the conical shell is in contact with the reactor cover gas, and the outer surface is provided with a heat insulating material.