JPH06174882A - Fat breeder reactor - Google Patents

Abstract

PURPOSE:To provide a small fast breeder reactor that reduces the amount of heat dissipated outside the reactor and the amount of irradiation of neutrons, can be accommodated by a simple, inexpensive shield structure and a cooling facility, and has high heat utilization efficiency and a long life. CONSTITUTION:A reactor core 2 is provided and a core barrel 3 is provided around the outer periphery of the reactor core 2 and a reflector 4 is provided around the outer periphery of the core barrel 3. The core barrel 3 is supported to the outer periphery of the reflector 4 by means of a support member and a bulkhead 6 constituting the inside wall of a coolant passage 5 for primary coolant is provided and a neutron shield 8 is provided within the coolant passage 5. A reactor vessel 7 constituting the outside wall of the coolant passage 5 is provided around the outer periphery of the neutron shield 8 and a guard vessel 9 is provided around the outer periphery of the reactor vessel 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a small-sized fast breeder reactor, and more particularly to a fast breeder reactor in which heat and neutrons are less diffused to the outside of a reactor vessel.

[0002]

2. Description of the Related Art A conventional small fast breeder reactor has a core surrounded by a plurality of vessels, and a reflector is provided outside the vessel. The reflector reflects neutrons emitted from the core to the outside through the vessel, It promoted combustion and proliferation.

FIG. 4 shows the structure of the conventional fast breeder reactor. A conventional fast breeder reactor 31 has a cylindrical core 32 made of nuclear fuel at the center, and a core barrel 33 that supports the core 32 is provided outside the core 32.
A reactor vessel 34 is provided outside the reactor vessel 34, a guard vessel 35 that protects the reactor vessel 34 is provided outside the reactor vessel 34, and a reflector 36 is provided outside the guard vessel 35. 1 between the core barrel 33 and the reactor vessel 34
A coolant flow path 37 through which the next coolant descends is formed.
An electromagnetic pump 38 is provided vertically above the core 32, and an intermediate heat exchanger 39 and a decay heat removal coil 40 are provided further above the electromagnetic pump 38.

During operation, the reactor vessel 34 is filled with liquid sodium as the primary coolant, and the plutonium in the reactor core 32 is fissioned. The core 32 has plutonium and depleted uranium, and heat is generated by the fission of the plutonium, and neutrons are emitted. This neutron is reflected by the reflector 36 on the outer periphery of the guard vessel 35 and absorbed by the depleted uranium in the reactor core 32 to generate plutonium. The generated plutonium is again fissioned to generate heat. With the combustion of the core 32, the reflector 36 is relatively moved in the vertical direction while maintaining the criticality of the core 32. As a result, the core 32 gradually burns and continues to generate heat for a long time. The primary coolant is driven upward by an electromagnetic pump 38, passes through an intermediate heat exchanger 39, and descends through the coolant flow path 37, as shown by the solid arrow in the figure, and the core 32
And then flows into the electromagnetic pump 38 again. The primary coolant passes through the core 32, absorbs the heat generated in the core 32, and transfers the heat to the intermediate heat exchanger 39. A secondary coolant flows into the intermediate heat exchanger 39 from an inlet pipe 41 as shown by a dashed arrow in the figure, and exchanges heat with the primary coolant. By this heat exchange, the heat of the core 32 is extracted to the outside through the outlet pipe 42 and used for power.

[0005]

However, in the above-mentioned conventional fast breeder reactor, since there is no neutron shield inside the reactor vessel and the reflector is arranged outside the reactor vessel, The vessel and reflector dissipate a large amount of heat into the shield structure containing the fast breeder reactor. In order to remove this heat, there has been a problem that the conventional cooling facility for the shield structure of the fast breeder reactor is increased in size.

Further, in the conventional fast breeder reactor, the amount of neutrons irradiated to the outside of the reactor vessel is large and the argon and nitrogen in the air inside the shield structure are activated, so that their release to the environment is prevented. Therefore, there is a problem that the entire reactor apparatus becomes large in size together with the problem that the cooling equipment becomes large in size. Further, the conventional fast breeder reactor cannot use stainless steel because the neutron dose received by the reactor vessel during the life of the reactor exceeds 10 ²³ nvt (E> 0.1 MeV). There was also the problem of having to use expensive high chromium steel. Furthermore, in the conventional fast breeder reactor, the electromagnetic pump is placed directly above the core, and the heat of the high-temperature liquid sodium heated in the core causes large thermal stress in the electromagnetic pump, which shortens the service life to maintain reliability. Therefore, in the conventional fast breeder reactor, the life of the electromagnetic pump is a limitation on the life of the small-sized fast breeder reactor as a whole. Further, in the conventional fast breeder reactor, the electromagnetic pump and the intermediate heat exchanger are arranged directly above the core, so that the electromagnetic pump and the intermediate heat exchanger must be removed when exchanging the fuel. The replacement work was difficult and there was a possibility of damaging the electromagnetic pump and the like during the fuel replacement. Therefore, the object of the present invention is to reduce the amount of heat and neutron irradiation radiated to the outside of the reactor, which can be accommodated by a simple shielding structure and cooling equipment,
It is to provide a small fast breeder reactor with high heat utilization efficiency.

[0007]

To achieve the above object, a fast breeder reactor according to the present invention comprises a core made of nuclear fuel, a core barrel surrounding the outer periphery of the core, and an annular ring as a whole surrounding the outer periphery of the core barrel. And a partition wall that surrounds the outer periphery of the reflector and that supports the core barrel by a support member that is arranged in the radial direction of the nuclear reactor and that constitutes the inner wall of the coolant channel of the primary coolant. , Surrounding the outer periphery of the partition wall, the neutron shield disposed in the coolant channel, and surrounding the outer periphery of the neutron shield, the reactor vessel constituting the outer wall of the coolant channel, the atom And a guard vessel that surrounds the outer circumference of the furnace vessel.

[0008]

In the fast breeder reactor of the present invention, since the reflector is close to the outer periphery of the core, neutrons are efficiently reflected and the nuclear fuel can be efficiently burned and breeded. Also,
Since the reflector itself is immersed inside the primary coolant,
The heat generated by the reflector is used as the output of the fast breeder reactor, which improves the efficiency of the reactor. Next, the neutron shield of the fast breeder reactor according to the present invention is located inside the reactor vessel, and in the coolant flow path, so the heat generated by the neutron shield is used as the output of the reactor. ,
Moreover, the amount of neutrons irradiated to the reactor vessel and the outside of the reactor vessel is small. This makes it possible to increase the thermal efficiency of the nuclear reactor, reduce the dose of neutrons in the nuclear reactor vessel, and use inexpensive stainless steel as the constituent material of the nuclear reactor vessel. In addition, the requirement for sealing property of the shield structure that houses the fast breeder reactor and the cooling equipment associated with it to the heat and the air in the shield structure that has been radiated is relaxed, and the shield structure and cooling facility are made smaller and simpler. be able to.

[0009]

EXAMPLE A fast breeder reactor of the present invention contains a reflector and a neutron shield inside a reactor vessel, and a coolant passage is constructed so that heat generated by these is used as an output of the reactor. In addition, the electromagnetic pump and the intermediate heat exchanger are formed into an annular shape so as not to hinder the core replacement work, and the electromagnetic pump is arranged so that it can be arranged downstream of the intermediate heat exchanger. By reducing the amount of heat and the amount of neutron irradiation, the efficiency of the fast breeder reactor is improved, and the fast breeder reactor, the shield structure for housing the fast breeder reactor, and the cooling equipment therefor are simplified. An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the construction of an embodiment of the fast breeder reactor of the present invention. The fast breeder reactor 1 has a core 2 made of an assembly of nuclear fuels, and the core 2 is formed in a substantially columnar shape as a whole. The core 2 is surrounded by a core barrel 3 that protects the core 2. An annular reflector 4 that surrounds the core barrel 3 as a whole is disposed outside the core barrel 3. A partition wall 6 that surrounds the outer periphery of the reflector 4 and forms the inner wall of the coolant channel 5 of the primary coolant is provided outside the reflector 4. A reactor vessel 7 that forms an outer wall of the coolant channel 5 is arranged outside the partition wall 6 with a space therebetween. A neutron shield 8 is provided in the core 2 in the coolant passage 5.
It is arranged so as to surround. A guard vessel 9 for protecting the reactor vessel 7 is provided further outside the reactor vessel 7. The reflector 4 is suspended by a plurality of drive shafts 11 penetrating the upper plug 10, and is supported by a reflector drive device 12 so as to be movable up and down. The partition wall 6 extends upward from the base plate 13 on which the reactor core 2 is mounted, and forms an annular coolant flow passage 5 with the reactor vessel 7. Below the coolant flow passage 5, the above-described partition wall 6 is formed. Thus, the neutron shield 8 is arranged. An annular electromagnetic pump 14 is disposed in the coolant flow path 5 above the neutron shield 8, and an intermediate heat exchanger 15 is further above the electromagnetic pump 14.
Is provided. A decay heat removal coil 16 is disposed above the intermediate heat exchanger 15. The intermediate heat exchanger 15 and the electromagnetic pump 14 are integrally formed, and are integrally and continuously formed with the upper structure of the nuclear reactor. As shown in the figure, the tube side and the shell side of the intermediate heat exchanger 15 are configured so that the primary coolant and the secondary coolant flow respectively. Between the intermediate heat exchanger 15, the lower end of the electromagnetic pump 14 and the upper end of the partition wall 6, a seal bellows 17 that absorbs expansion and contraction of the small fast breeder reactor 1 due to heat and defines the coolant flow path 5 is provided. ing. This fast breeder reactor 1 uses nuclear fuel containing plutonium in the core 2. During operation, the plutonium in the core 2 is split to generate heat and excess surplus fast neutrons are absorbed by depleted uranium to produce plutonium in excess of the amount burned. To do. The reflector 4 reflects the neutrons emitted from the core 2 and promotes the combustion and multiplication of nuclear fuel in the core 2. With the burning of the nuclear fuel, the reflector 4 is gradually moved while maintaining the criticality of the nuclear fuel, whereby the fresh fuel portion of the core 2 is gradually burned and the burning can be maintained for a long time.

In operation, the reactor vessel 7 is filled with liquid sodium as a primary coolant, and the primary coolant is used to cool the core 2 while taking out heat from nuclear fission. Next, the flow of the primary coolant will be described. The solid arrows in FIG. 1 indicate the flow direction of the primary coolant. As shown by these solid arrows, the primary coolant is driven downward by the electromagnetic pump 14 and flows through the inside of the neutron shield 8. And reaches the bottom of the reactor vessel 7. Next, the primary coolant rises while flowing through the core 2, and the intermediate heat exchanger 1 is placed above the reactor vessel 7.
5 flows into the tube side. Furthermore, the primary coolant flows out after heat exchange with the secondary coolant in the intermediate heat exchanger 15,
It is driven downward again by the electromagnetic pump 14. In contrast to the primary coolant, the secondary coolant flows into the shell side of the intermediate heat exchanger 15 from the outside through the inlet nozzle 18, and after being heated by the primary coolant in the intermediate heat exchanger 15, the outlet nozzle 19 Flows out from the outside and converts the heat into motive power.

FIG. 2 shows a cross section of the fast breeder reactor of this embodiment along the arrow AA shown in FIG. In this embodiment, six drive shafts 11 are arranged at equal distances from the center, and on the outside thereof, there are an inner case 20 and an outer case 21 of the intermediate heat exchanger 15. A heat transfer tube 22 is arranged between the inner case 20 and the case 21. Reference numeral 23 represents the intermediate heat exchanger 15 and the electromagnetic pump 14.
And an outer shroud that suspends and together. As is clear from FIG. 2 and FIG. 1, in this embodiment, the intermediate heat exchanger 15 is formed in an annular shape, and the drive shaft 11 of the reflector 4 is provided inside thereof, and the drive shaft 11 is a center that does not interfere with the core 2. Is located at a distance from. That is, the upper portion of the reactor core 2 is a hollow space, which allows the electromagnetic pump 1
The core 2 can be replaced without removing the intermediate heat exchanger 4 and the intermediate heat exchanger 15.

FIG. 3 shows a cross section of the fast breeder reactor of this embodiment along the arrow BB shown in FIG. As shown in FIG. 3, the core 2 has a circular cross section as a whole, a core barrel 3 is located outside the core 2, and a generally annular reflector 4 is hung by a drive shaft 11 outside the core barrel 3. It has been lowered. A partition wall 6 is provided outside the reflector 4, and a plurality of ribs 24 are provided inside the partition wall 6 so as to project radially inward of the fast breeder reactor 1. These ribs 2
Reference numeral 4 penetrates the reflector 4 and supports the outer periphery of the core barrel 3 at its tip. The reflector 4 is divided into six parts, and each divided part is suspended by the drive shaft 11 so as to be vertically movable without interfering with the ribs 24. As shown in FIG. 3, there is an annular neutron shield 8 around the partition wall 6 as a whole, and the neutron shield 8 is configured by arranging a large number of cylinders 25 around the partition wall 6 so as to have gaps between them. Has been done. This allows the primary coolant to flow through the inside of the neutron shield 8 and efficiently cool the neutron shield 8.

The operation of this embodiment will be described below based on the above structure. Since the reflector 4 of this embodiment is provided in the vicinity of the outer periphery of the core 2, neutrons are effectively reflected, the nuclear fuel is efficiently burned and propagated, and the criticality is increased with the burning of the nuclear fuel. By gradually moving the reflector 4 while maintaining it, the new fuel portion of the core 2 is gradually burned, and combustion can be maintained for a long time. The neutron shield 8 shields neutrons that pass through or bypass the reflector 4 and radiate, and reduces the amount of neutrons that are irradiated to the space inside the reactor vessel 7 and the shield structure. As a result, stainless steel can be used as a constituent material of the reactor vessel 7,
An inexpensive reactor vessel 7 can be obtained. Furthermore, since the heat and the amount of activated argon and nitrogen in the shielding structure are reduced, the cooling facility of the shielding structure can be downsized, and the sealing requirement for the activated argon and nitrogen can be relaxed. You can Further, since the reflector 4 and the neutron shield 8 are immersed in the primary coolant, the heat generated by them is utilized as the output of the fast breeder reactor 1, and the more efficient fast breeder reactor 1 is provided. Obtainable. Further, in this embodiment, since the electromagnetic pump 14 is installed on the downstream side of the intermediate heat exchanger 15, the primary coolant driven by the electromagnetic pump 14 has the lowest temperature in the circulation cycle. As a result, the thermal stress applied to the electromagnetic pump 14 is small, and the electromagnetic pump 14 can withstand long-term use. As a result, the life of the fast breeder reactor 1 as a whole is extended. Further, since no device such as the electromagnetic pump 14 that interferes with the core 2 is disposed above the core 2, the upper plug 10 can be removed at the time of replacement and the used core 2 can be directly pulled out vertically. This simplifies the nuclear fuel replacement work that was conventionally performed by removing the intermediate heat exchanger 15 and the electromagnetic pump 14, and can prevent damage to the electromagnetic pump 14 and the like due to the replacement work.

The invention according to the present application is the fast breeder reactor 1
The core 2, the core barrel 3, the reflector 4, the partition wall 6, the neutron shield 8, the reactor vessel 7, and the guard vessel 9 are arranged from the center to the outside, and the coolant flow is provided between the partition wall 6 and the reactor vessel 7. Road 5
However, as is clear from the above description, the reflector 4 is divided into a plurality of pieces in the radial direction, and each of the reflectors 4 is formed.
Of which the divided parts of the above are movably supported in the axial direction, those in which the neutron shield 8 is composed of a plurality of cylinders having a gap or a multi-ring torus so that the primary coolant flows through the inside, An annular electromagnetic pump 14 is provided above the coolant channel 5.
And the intermediate heat exchanger 15 are arranged and the reflector 4 is suspended inside the electromagnetic pump 14 and the intermediate heat exchanger 15, or the electromagnetic pump 14 and the intermediate heat exchanger 15 are superstructures of a nuclear reactor. The seal bellows 1 is formed integrally with the body, and is provided between the lower end of the body and the upper end of the partition wall 6 erected on the lower structure of the nuclear reactor.
Those provided with 7 are included in the technical scope of the present invention.

[0016]

In the fast breeder reactor according to the present invention, the reflector is arranged on the outer periphery of the core, and the coolant passage is formed on the outer periphery of the reflector.
A neutron shield is placed in this coolant channel, and since all of these are housed in the reactor vessel and guard vessel,
The heat utilization efficiency is high, and the amount of neutrons and heat that leak to the outside of the reactor vessel is small. Due to the small amount of neutrons and heat leaking to the outside of the reactor vessel, it is possible to form the reactor vessel with steel materials that have a relatively low allowable limit for neutrons and heat, and also to shield the fast breeder reactor and its cooling structure. The equipment can be downsized, and the requirement for the sealing ability of the cooling equipment against the activated nitrogen or argon can be relaxed.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing a cross section perpendicular to the axial direction of an embodiment of a fast breeder reactor according to the present invention.

FIG. 3 is a cross-sectional view showing a cross section perpendicular to the axial direction of an embodiment of a fast breeder reactor according to the present invention.

FIG. 4 is a cross-sectional view showing a cross section in the axial direction of a conventional fast breeder reactor.

[Explanation of symbols]

 1 Fast Breeder Reactor 2 Core 3 Core Barrel 4 Reflector 5 Coolant Channel 6 Partition 7 Reactor Vessel 8 Neutron Shield 9 Guard Vessel 11 Drive Shaft 14 Electromagnetic Pump 15 Intermediate Heat Exchanger 16 Decay Heat Removal Coil 17 Seal Bellow 24 Rib 25 cylinder

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shikihiko Iida 1-1-1, Shibaura, Minato-ku, Tokyo Inside Toshiba Head Office

Claims (1)

[Claims] 1. A core made of nuclear fuel, a core barrel surrounding the outer periphery of the core, an annular reflector as a whole surrounding the outer periphery of the core barrel, and an outer periphery of the reflector in a radial direction of a nuclear reactor. The core barrel is supported by the disposed support member, and the partition wall that forms the inner wall of the coolant channel of the primary coolant and the outer periphery of the partition wall is surrounded and disposed in the coolant channel. A neutron shield,
A fast breeder reactor comprising: a reactor vessel surrounding the outer periphery of the neutron shield and forming an outer wall of the coolant passage; and a guard vessel surrounding the outer periphery of the reactor vessel.