JP2020176949A - Molten fuel outflow pipe of fast reactor and fast reactor - Google Patents

Abstract

To appropriately discharge molten fuel in a fast reactor.SOLUTION: A molten fuel outflow pipe 54 provided in a core of a fast reactor 1, inside of which is filled with a coolant, includes: an inner pipe 62 in which a lower opening 62b is formed on the lower end side in the axial direction; and an outer pipe 60 which is provided so as to surround the inner pipe 62 and adjacent to a heat generation region of the core. The outer pipe 60 and the inner pipe 62 can be fused by heat of the molten fuel in the heating region, and an inner pipe inside 62a and the lower opening 62b become an outflow path allowing the molten fuel, which has flowed into the inner pipe 62 due to the fusing of the outer pipe 60 and the inner pipe 62, to flow out therefrom.SELECTED DRAWING: Figure 5

Description

The present invention relates to a molten fuel outflow pipe of a fast reactor and a fast reactor.

A fuel assembly and control rods are arranged in the core of the fast reactor, and the control rods are housed in the control rod guide pipes. In a fast reactor, core damage may occur. When the core is damaged, it has been proposed to let the molten fuel flow out to the debris core catcher via the control rod guide pipe from the viewpoint of preventing the recriticality of the molten fuel in the fuel assembly (for example, the following). (See Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-125837

In Patent Document 1 described above, the molten fuel that has invaded by melting the peripheral wall of the control rod guide pipe melts the dashpot in the control rod guide pipe, thereby forming an outflow path through which the molten fuel flows out. However, since the fusing position of the dashpot is far from the melting position of the peripheral wall, the temperature of the molten fuel drops because the molten fuel comes into contact with other members and sodium etc. and loses heat before reaching the dashpot. It ends up. If the temperature of the molten fuel drops, the dashpot may not be properly melted by the molten fuel and the molten fuel may not flow out.

Therefore, the present invention has been made in view of these points, and an object of the present invention is to appropriately flow out the molten fuel of a fast reactor.

In the first aspect of the present invention, the molten fuel outflow pipe of the high speed furnace provided in the core of the high speed furnace is filled with a cooling material, and a lower opening is provided on the lower end side in the axial direction. The formed inner pipe and the outer pipe provided so as to surround the inner pipe and adjacent to the heat generating region of the core are provided, and the outer pipe and the inner pipe are formed by the heat of the molten fuel in the heat generating region. The inside of the inner pipe and the lower opening become a flow path for the molten fuel that has flowed into the inner pipe due to the fusing of the outer pipe and the inner pipe. Provide a tube.

Further, the distance between the outer peripheral surface of the inner pipe and the inner peripheral surface of the outer pipe may be smaller than the radius of the inner pipe.

Further, the thickness of the inner pipe and the thickness of the outer pipe may be smaller than the distance between the outer peripheral surface of the inner pipe and the inner peripheral surface of the outer pipe.

Further, the gap between the inner pipe and the outer pipe may be a flow path portion through which the coolant flows.

Further, the molten fuel outflow pipe is provided on the lower end side of the outer pipe in the axial direction, and has an inflow portion formed by an inflow port into which the coolant flows into the flow path portion and the shaft of the outer pipe. Cooling material formed on the upper end surface in the direction and flowing out of the flow path portion is formed on the opening on the outer pipe and the upper end surface of the inner pipe in the axial direction and flows through the flow path portion. An opening on the inner tube through which the material flows into the inside of the inner tube may be further provided.

In the second aspect of the present invention, the molten fuel outflow pipe is a high-speed furnace in which a plurality of molten fuel outflow pipes are dispersedly arranged in the core, and the molten fuel outflow pipe is filled with a cooling material inside. An inner pipe having a lower opening formed on the lower end side in the axial direction and an outer pipe provided so as to surround the inner pipe and adjacent to a heat generating region of the core are provided, and the inner pipe and the outer pipe are provided. The upper end in the axial direction is located above the heat generation region, and the axial lower pipe of the inner pipe and the outer pipe is located below the heat generation region, and the outer pipe and the inner pipe are located. Can be melted by the heat of the molten fuel in the heat generating region, and the inside and the lower opening of the inner pipe flow out the molten fuel that has flowed into the inner pipe due to the fusing of the outer pipe and the inner pipe. Provide a fast furnace that serves as an outflow channel.

According to the present invention, there is an effect that the molten fuel of the fast reactor can be appropriately discharged.

It is a schematic diagram for demonstrating an example of the structure of the fast reactor 1 which concerns on one Embodiment of this invention. It is a schematic diagram for demonstrating an example of the arrangement state of a core component group. It is a schematic diagram for demonstrating an example of the structure of the molten fuel outflow pipe 54. FIG. 3 is a cross-sectional view taken along the line II of FIG. It is a schematic diagram for demonstrating the outflow route of molten fuel.

<Structure of fast reactor>
The configuration of the fast reactor according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 is a schematic diagram for explaining an example of the configuration of the fast reactor 1 according to the embodiment. The fast reactor 1 uses uranium, plutonium, or the like as fuel to sustain the fission chain reaction while controlling it, and extracts energy. The fast reactor 1 is a tank type fast reactor in which an intermediate heat exchanger and a pump are provided in a main container. However, the present invention is not limited to this, and for example, the fast reactor 1 may be a loop type fast reactor in which an intermediate heat exchanger and a pump are provided outside the main container.

As shown in FIG. 1, the fast reactor 1 includes a main container 3, a core 5, a core tank 7, a core superstructure 9, a diamond grid 11, a pump 13, a pipe 15, a partition plate 17, and the like. It has an intermediate heat exchanger 19 and a core catcher 21. In FIG. 1, the flow of the coolant is indicated by an arrow. Further, FIG. 1 shows one molten fuel outflow pipe 54, which will be described later.

The main container 3 is a thin-walled, large-diameter container. The diameter of the main container 3 is, for example, about 15 m to 20 m.
The core 5 is arranged in the central portion of the main container 3. The core 5 has an exothermic region 5a in which a fission chain reaction can occur.

The core tank 7 is a tank that houses the core 5. The core tank 7 is provided above the diamond grid 11. Inside the core tank 7, a core component group (fuel assembly, control rods, etc.) is arranged.
The core superstructure 9 is located directly above the core components. The core upper structure 9 is provided with various measuring devices such as a control rod drive mechanism, a thermometer, and a fuel damage position detector.

The diamond grid 11 functions as an inlet for inflowing the coolant into the core 5. The coolant flows into the core 5 during the normal operation of the fast reactor 1 to cool the core 5. The coolant is, for example, liquid metal sodium, but is not limited to this. The diamond grid 11 is provided with a large number of cylindrical connecting pipes for inserting the lower end portions of the core components.

The pump 13 generates power for circulating the coolant in the main container 3. The pump 13 sucks the coolant and directs it to the core 5. Although one pump 13 is shown in FIG. 1, a plurality of pumps 13 are provided in the main container 3 at predetermined intervals along the circumferential direction.

The pipe 15 is a pipe connecting the diamond grid 11 and the pump 13. The coolant sucked by the pump 13 flows to the diamond grid 11 via the pipe 15.

The partition plate 17 is a wall that partitions the inside of the main container 3 into an upper plenum and a lower plenum. The area above the partition plate 17 is the upper plenum, and the area below the partition plate 17 is the lower plenum.

The intermediate heat exchanger 19 exchanges heat with the coolant to lower the temperature of the coolant. The intermediate heat exchanger 19 is provided in the main container 3 along the vertical direction. The intermediate heat exchanger 19 has an inflow port 19a located in the upper plenum and an outflow port 19b located in the lower plenum. The inflow port 19a is an opening through which the high-temperature coolant of the upper plenum passing through the core 5 flows. The high-temperature coolant flowing in from the inflow port 19a exchanges heat in the intermediate heat exchanger 19. The outlet 19b is an opening through which the coolant whose temperature has dropped due to heat exchange flows out to the lower plenum. Although one intermediate heat exchanger 19 is shown in FIG. 1, a plurality of intermediate heat exchangers 19 are provided in the main container 3 along the circumferential direction at predetermined intervals.

In the fast reactor 1, a core damage accident may occur. Therefore, in the present embodiment, when a core damage accident occurs, the molten fuel of the core 5 is discharged to the core catcher 21 via the molten fuel outflow pipe 54 (details will be described later).

The core catcher 21 is arranged at the bottom of the main container 3. That is, the core catcher 21 is located in the lower plenum. The core catcher 21 receives at least one of the molten fuel of the core 5, the solidified molten fuel, and the mixture of the molten fuel and the solidified (for convenience of explanation, simply referred to as molten fuel). Further, the core catcher 21 has a function as a cooling unit for cooling the received molten fuel. As a result, it is possible to prevent the molten fuel from melting the main container 3 and leaking to the outside.

<Arrangement of core components>
The arrangement state of the core component group of the core 5 will be described with reference to FIG.
FIG. 2 is a schematic diagram for explaining an example of the arrangement state of the core component group. As shown in FIG. 2, the core 5 is provided with a fuel assembly 50, a control rod assembly 52, and a molten fuel outflow pipe 54 as core component groups. In FIG. 2, for convenience of explanation, the fuel assembly 50 is shown as a white hexagon, the control rod assembly 52 is shown as a black-painted hexagon, and the molten fuel outflow pipe 54 is shown as a hatched hexagon. Has been done.

In the core 5, a plurality of fuel assemblies 50, control rod assemblies 52, and molten fuel outflow pipes 54 are regularly arranged as shown in FIG. The control rod assembly 52 and the molten fuel outflow pipe 54 are arranged at a predetermined ratio with respect to the fuel assembly 50.

The fuel assembly 50 is a fuel assembly in which a plurality of fuel rods are bundled. The individual fuel rods contain pelletized fuel in the pipe. As shown in FIG. 2, a plurality of fuel assemblies 50 are arranged in the core 5.

The control rod assembly 52 is for controlling the output of the fast reactor 1 with the control rods. The control rods are housed in a guide tube. The control rod assembly 52 is arranged between the plurality of fuel assemblies 50 as shown in FIG.

The molten fuel outflow pipe 54 is a pipe for letting out the molten fuel of the core 5. When a core damage accident occurs, a part of the peripheral wall of the molten fuel outflow pipe 54 is melted by the molten fuel, and the molten fuel flows into (enters) the inside of the molten fuel outflow pipe 54 from the fusing portion. The molten fuel that has flowed into the pipe falls inside the pipe and reaches the core catcher 21 (FIG. 1). As a result, the molten fuel can be smoothly discharged to the core catcher 21.

A plurality of molten fuel outflow pipes 54 are dispersedly arranged in the core 5. Here, as shown in FIG. 2, a plurality of molten fuel outflow pipes 54 are provided at the center and the outer peripheral portion of the core 5, respectively. The arrangement state of the molten fuel outflow pipe 54 in the core 5 is not limited to the arrangement state shown in FIG.

<Detailed configuration of molten fuel outflow pipe 54>
The detailed configuration of the molten fuel outflow pipe 54 will be described with reference to FIGS. 3 and 4.
FIG. 3 is a schematic view for explaining an example of the configuration of the molten fuel outflow pipe 54. FIG. 4 is a cross-sectional view taken along the line II of FIG. In FIG. 3, the molten fuel outflow pipe 54 in a state of being inserted into the connecting pipe 11a of the diamond grid 11 is shown.

The molten fuel outflow pipe 54 is a double pipe, and the coolant flows through the gap between the double pipes. As shown in FIG. 3, the molten fuel outflow pipe 54 includes an outer pipe 60, an inner pipe 62, an inflow portion 64, a flow path portion 66, an outer pipe upper opening 68, and an inner pipe upper opening 70. Has.

As shown in FIG. 4, the outer pipe 60 is a cylinder forming the outer shape of the molten fuel outflow pipe 54. The outer pipe 60 is provided so as to surround the outer peripheral surface of the inner pipe 62. The outer pipe 60 is adjacent to the heat generating region 5a of the core 5. The outer pipe 60 is inserted into the connecting pipe 11a of the diamond grid 11 and connected to the connecting pipe 11a. Although not shown in FIG. 3, the core catcher 21 (FIG. 1) is located below the connecting pipe 11a.

As shown in FIG. 4, the inner pipe 62 is arranged in the outer pipe 60 through a predetermined gap. The inner pipe inside 62a, which is the inside of the inner pipe 62, is filled with a coolant. A lower opening 62b is formed on the lower end side of the inner pipe 62 in the axial direction. The lower opening 62b has an opening formed on the end surface of the lower end of the inner pipe 62 in the axial direction. The lower opening 62b communicates with the inside 62a of the inner pipe.

As shown in FIG. 3, the axial upper end of the inner pipe 62 is lower than the axial upper end of the outer pipe 60. On the other hand, the upper end of the inner pipe 62 in the axial direction is located above the heat generating region 5a (see FIG. 1). That is, the upper ends of the inner pipe 62 and the outer pipe 60 in the axial direction are located above the heat generating region 5a. The lower end of the inner pipe 62 in the axial direction is substantially the same as the lower end of the outer pipe 60 in the axial direction. The axial lower pipes of the inner pipe 62 and the outer pipe 60 are located below the heat generating region 5a (see FIG. 1). Since the inner pipe 62 and the outer pipe 60 are in the above positional relationship with respect to the heat generating region 5a, the molten fuel in the heat generating region 5a can melt the peripheral walls of the outer pipe 60 and the inner pipe 62 by heat when the core is damaged. For example, the portion of the peripheral wall of the outer pipe 60 adjacent to the heat generating region 5a is melted by the molten fuel. The fusing portion of the inner pipe 62 due to the molten fuel is substantially the same position as the fusing portion of the outer pipe 60 in the axial direction.

In order to make it easier for the molten fuel to melt the inner pipe 62, the width of the gap between the inner pipe 62 and the outer pipe 60, the thickness of the inner pipe 62 and the outer pipe 60, etc., take into consideration the characteristics of the molten fuel, etc. Can be set to an appropriate size. For example, it is desirable that the gap between the inner pipe 62 and the outer pipe 60 (the distance between the outer peripheral surface of the inner pipe 62 and the inner peripheral surface of the outer pipe 60) is set small. As an example, the distance between the outer peripheral surface of the inner pipe 62 and the inner peripheral surface of the outer pipe 60 is smaller than the radius of the inner pipe 62. As a result, the outer pipe 60 and the inner pipe 62 are brought into close contact with each other, and the molten fuel easily melts the inner pipe 62 following the outer pipe 60. Further, the thickness of the inner pipe 62 and the thickness of the outer pipe 60 may be smaller than the distance between the outer peripheral surface of the inner pipe 62 and the inner peripheral surface of the outer pipe 60. Further, the thickness of the inner pipe 62 may be smaller than the thickness of the outer pipe 60. Even if the temperature of the molten fuel drops after the outer pipe 60 is blown, the inner pipe 62 is easily blown because the thickness of the inner pipe 62 is smaller than the thickness of the outer pipe 60.

When the outer pipe 60 and the inner pipe 62 are blown by the molten fuel, the molten fuel flows into the inner pipe 62 (specifically, the inner pipe 62a) from the fusing portion. The coolant that has flowed into the inner pipe 62a flows out from the lower opening 62b of the inner pipe 62. That is, the inner pipe inner 62a and the lower opening 62b serve as outflow passages through which the molten fuel flows out. Since there is no shield or the like inside the inner pipe 62a, the coolant that has flowed into the inner pipe 62a tends to flow out from the lower opening 62b.

The inflow portion 64 is a portion where the coolant flows into the molten fuel outflow pipe 54. The high-pressure coolant sent to the diamond grid 11 by the pump 13 flows into the inflow section 64. As shown in FIG. 3, the inflow portion 64 is provided on the lower end side of the outer pipe 60 in the axial direction. The inflow portion 64 is formed with an inflow port into which the coolant flows. The inflow port is formed on the outer peripheral surface of the outer pipe 60.

The flow path portion 66 is a portion through which the coolant flows in the molten fuel outflow pipe 54. As shown in FIG. 3, the flow path portion 66 is a portion of a gap between the inner pipe 62 and the outer pipe 60. The flow path portion 66 communicates with the inflow section 64, and the coolant flowing in from the inflow section 64 flows through the flow path section 66. The coolant in the flow path portion 66 flows upward in the axial direction as shown in FIG.

The outer pipe upper opening 68 is an opening formed on the upper end surface of the outer pipe 60 in the axial direction. The outer pipe upper opening 68 communicates with the flow path portion 66, and the coolant flowing through the outer pipe upper opening 68 flows out of the outer pipe (upper plenum) from the outer pipe upper opening 68. The flow flowing out from the opening 68 on the outer pipe of the coolant is generated because the pressure in the flow path portion 66 is larger than the pressure outside the pipe.

The inner pipe upper opening 70 is an opening formed on the upper end surface of the inner pipe 62 in the axial direction. The inner pipe upper opening 70 communicates with the flow path portion 66, and the coolant flowing through the inner pipe upper opening portion 66 flows into the inner pipe inner 62a from the inner pipe upper opening 70. The flow of the coolant flowing into the inner pipe inside 62a is generated because the pressure in the flow path portion 66 is larger than the pressure in the inner pipe 62a.

During the normal operation of the fast reactor 1, a part of the coolant flowing into the molten fuel outflow pipe 54 flows out from the outer pipe upper opening 68 via the flow path portion 66. Further, a part of the coolant flows to the inside of the inner pipe 62a via the flow path portion 66, and flows out from the lower opening 62b.

The molten fuel outflow pipe 54 can be pulled out upward from the state of being inserted into the connecting pipe 11a of the diamond grid 11. At this time, the coolant remaining in the flow path portion 66 of the molten fuel outflow pipe 54 is discharged from the outflow port of the inflow portion 64. That is, the inflow portion 64 also has a function of a discharge port for discharging the coolant.

<Outflow route of molten fuel>
The outflow of the molten fuel through the molten fuel outflow pipe 54 will be described with reference to FIG.
FIG. 5 is a schematic diagram for explaining the outflow route of the molten fuel. In FIG. 5, the flow of molten fuel is indicated by a thick arrow.

Here, it is assumed that in the fast reactor 1, core damage occurs in which the fuel assembly 50 (FIG. 2) melts due to overheating of the fuel. Then, the molten fuel of the fuel assembly 50 (heat generation region 5a) blows the peripheral walls of the outer pipe 60 and the inner pipe 62 of the adjacent molten fuel outflow pipe 54. Since the outer peripheral surface of the inner pipe 62 is close to the outer pipe 60, the molten fuel easily melts not only the outer pipe 60 but also the inner pipe 62.

When the peripheral walls of the outer pipe 60 and the inner pipe 62 are blown, the molten fuel enters the inner pipe 62 (that is, the inner pipe 62a) via the fusing portion (see FIG. 5). As shown in FIG. 5, the molten fuel that has entered the inner pipe inner 62a falls down the inner pipe inner 62a and flows out from the lower opening 62b that communicates with the inner pipe inner 62a. The coolant flowing out from the lower opening 62b passes through the connecting pipe 11a of the diamond grid 11 and reaches the core catcher 21 (FIG. 1). The coolant that has reached the core catcher 21 is cooled by the core catcher 21 having a cooling function. This makes it possible to prevent the molten fuel from melting the main container 3 of the fast reactor 1 and leaking to the outside when the core is damaged.

<Effect in this embodiment>
The molten fuel outflow pipe 54 of the fast reactor 1 of the above-described embodiment has a double pipe structure in which an outer pipe 60 adjacent to a heat generating region 5a of the core 5 surrounds an inner pipe 62. The outer pipe 60 and the inner pipe 62 can be melted by the molten fuel in the heat generating region 5a. The inner pipe inner 62a and the lower opening 62b of the inner pipe 62 serve as an outflow passage for the molten fuel that has flowed into the inner pipe 62 due to the melting of the outer pipe 60 and the inner pipe 62 by the molten fuel.

With the above configuration, when the core is damaged, the peripheral walls of the outer pipe 60 and the inner pipe 62 arranged close to each other are melted by the molten fuel in the heat generating region 5a. That is, since the molten fuel in which the outer pipe 60 is blown melts the inner pipe 62 located at a short distance, the inner pipe 62 is melted before the temperature drops, and the inside of the inner pipe 62 is formed from the blown portion ( It becomes easy to flow into the inner pipe 62a). Further, in the inner pipe 62, the lower opening 62b communicates with the inner pipe inner 62a, so that the molten fuel flowing into the inner pipe inner 62a falls down the inner pipe inner 62a and flows out from the lower opening 62b. .. By using the molten fuel outflow pipe 54 having a simple structure as described above, it is possible to appropriately outflow the molten fuel when the core is damaged.

During normal operation, in the molten fuel outflow pipe 54, the coolant flows through the flow path portion 66 in the gap between the inner pipe 62 and the outer pipe 60, and a part of the coolant flows out of the pipe from the opening 68 on the outer pipe. It flows out to (upper plenum), and a part of the coolant flows into the inner pipe inside 62a from the inner pipe upper opening 70. This has the following advantages.

First, if the fast reactor 1 has a structure in which the high-temperature coolant in the upper plenum flows into the molten fuel outflow pipe 54, the coolant in the molten fuel outflow pipe 54 is warmed and gas is used. If gas is generated, the reactivity of the core 5 increases, which causes a problem. On the other hand, in the present embodiment, the flow of the coolant from the outer pipe upper opening 68 toward the upper plenum can prevent the high-temperature coolant of the upper plenum from flowing into the molten fuel outflow pipe 54. As a result, it is possible to prevent the coolant in the molten fuel outflow pipe 54 from being heated and generating gas.

Further, similarly to the above, in the case of the fast reactor 1, when the coolant of the upper plenum having a high temperature flows into the molten fuel outflow pipe 54, the high temperature region and the low temperature region enter the molten fuel outflow pipe 54. (Specifically, the upper part in the molten fuel outflow pipe 54 becomes a high temperature region, and the lower part in the molten fuel outflow pipe 54 becomes a low temperature region). When a temperature difference occurs, thermal stress is generated in the molten fuel outflow pipe 54, which may cause fatigue failure or the like in the molten fuel outflow pipe 54. On the other hand, in the present embodiment, the low-temperature coolant flows into the inner pipe 62a from the inner pipe upper opening 70, so that the temperature inside the inner pipe 62 is easily made uniform, and the inner pipe 62 is fatigued. Destruction can be suppressed.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes can be made within the scope of the gist. is there. For example, all or part of the device can be functionally or physically distributed / integrated in any unit. Also included in the embodiments of the present invention are new embodiments resulting from any combination of the plurality of embodiments. The effect of the new embodiment produced by the combination has the effect of the original embodiment.

1 Fast reactor 5 Core 5a Heat generation area 54 Molten fuel outflow pipe 60 Outer pipe 62 Inner pipe 62a Inner pipe inner 62b Lower opening 64 Inflow part 66 Flow path part 68 Outer pipe upper opening 70 Inner pipe upper opening

Claims (6)

It is a molten fuel outflow pipe of a fast reactor installed in the core of a fast reactor.
The inside is filled with coolant, and an inner pipe with a lower opening formed on the lower end side in the axial direction,
An outer pipe provided so as to surround the inner pipe and adjacent to the heat generating region of the core,
With
The outer pipe and the inner pipe can be blown by the heat of the molten fuel in the heat generating region.
The inside of the inner pipe and the lower opening serve as an outflow passage for discharging the molten fuel that has flowed into the inner pipe due to the fusing of the outer pipe and the inner pipe.
Molten fuel outflow pipe for fast reactor. The distance between the outer peripheral surface of the inner pipe and the inner peripheral surface of the outer pipe is smaller than the radius of the inner pipe.
The molten fuel outflow pipe of the fast reactor according to claim 1. The thickness of the inner pipe and the thickness of the outer pipe are smaller than the distance between the outer peripheral surface of the inner pipe and the inner peripheral surface of the outer pipe.
The molten fuel outflow pipe of the fast reactor according to claim 1 or 2. The gap between the inner pipe and the outer pipe is a flow path portion through which the coolant flows.
The molten fuel outflow pipe of the fast reactor according to any one of claims 1 to 3. An inflow portion provided on the lower end side of the outer pipe in the axial direction and formed with an inflow port through which the coolant flows into the flow path portion.
An opening on the outer pipe formed on the upper end surface of the outer pipe in the axial direction and allowing the coolant flowing through the flow path to flow out of the pipe.
Further provided is an inner pipe upper opening formed on the upper end surface of the inner pipe in the axial direction and in which a coolant flowing through the flow path portion flows into the inside of the inner pipe.
The molten fuel outflow pipe of the fast reactor according to claim 4. A fast reactor in which multiple molten fuel outflow pipes are dispersed and arranged in the core.
The molten fuel outflow pipe
The inside is filled with coolant, and an inner pipe with a lower opening formed on the lower end side in the axial direction,
An outer pipe provided so as to surround the inner pipe and adjacent to the heat generating region of the core,
With
The axial upper ends of the inner pipe and the outer pipe are located above the heat generation region.
The axial lower pipe of the inner pipe and the outer pipe is located below the heat generation region.
The outer pipe and the inner pipe can be blown by the heat of the molten fuel in the heat generating region.
The inside of the inner pipe and the lower opening serve as an outflow passage for discharging the molten fuel that has flowed into the inner pipe due to the fusing of the outer pipe and the inner pipe.
Fast reactor.

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