JPS63284489A - Tank type fast breeder - Google Patents

Abstract

PURPOSE:To prevent the fluctuation in the liquid level of a coolant and to maintain the defectless operation of a nuclear reactor by providing a guide plate to attenuate the perpendicular flow rate component of the coolant flowing toward the coolant liquid surface to the inside peripheral face of a hanging body. CONSTITUTION:The guide plate 40 having an inside circumferential cylindrical shape is provided under the liquid surface of the primary sodium 6 on the inside peripheral face of the hanging body 4. The primary sodium 6 flowing out of a reactor core part 2 changes its direction radially in the lower part of an upper mechanism 16 of the core and flows toward the inside wall of the body 4. The greater part of the sodium 6 flows out of a hanging body flow hole 8 and part of the sodium 6 rises along the inside peripheral wall of the body 4. The ascending flow of the sodium 6 passes the cylindrical guide plate 40 provided on the inside peripheral face of the body 4 and the annulus part of the body 4 and the greater part thereof flows from the flow hole 8 to the outside of the hanging body. The flow backward toward the inside of the body 4 by passing an orifice 41 is also possible. The sodium is attenuated in the perpendicular flow rate component after the passage through the orifice 41 so that the sodium 6 flows by changing its direction toward the lateral side. The oscillation in the free liquid surface of the sodium 6 is, therefore, prevented.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a tank-type fast breeder reactor, and in particular to a tank-type fast breeder reactor in which the reactor core is held in a hanging shell suspended from a roof slab. Regarding furnaces.

(Prior technology) Tank-type fast breeder reactors generally use liquid metallic sodium as the primary and secondary coolant, and the primary sodium heated in the reactor core is transferred to an intermediate heat exchanger installed in the reactor vessel. The cooled primary sodium is then fed back into the reactor core to exchange heat with the secondary sodium.

FIG. 4 shows a schematic configuration of a conventional tank-type fast breeder reactor, in which a reactor core part 2 is formed inside a reactor vessel 1, and this reactor core part 2 is attached to a Lux slab 3 that covers the upper opening of the reactor vessel 1. It is held by a suspension barrel 4 that is installed vertically. The inside of the reactor vessel 1 is filled with primary sodium 6 as a coolant, and the suspension shell 4 is filled with primary sodium 6 as a coolant.
A hanger flow hole 8 is provided in which the primary sodium 6 that has flowed up through the reactor core 2 flows. Reactor core 2
is composed of a fuel assembly 9, a blanket fuel assembly IO, and a reflector 11.

The inside of the reactor vessel 1 is partitioned into an upper plenum 14 and a lower plenum 15 by a partition wall 13 . A core upper mechanism 16 is installed through the center of the roof slab 3, and a plurality of intermediate heat exchangers 17 and a plurality of circulation pumps 18 are installed independently at the periphery.

The circulation pump 18 has an impeller 20 driven by a motor 19, and the discharge side of the circulation pump 18 is connected to the inlet pipe 2.
1 to a high pressure plenum 22.

In the intermediate heat exchanger 17, a secondary sodium outlet pipe 26 is provided coaxially in the center of the shroud 25, and a secondary sodium inlet pipe 27 is further provided within the secondary sodium outlet pipe 26. A large number of heat transfer tubes 29 are supported by an upper tube sheet 27 and a lower tube sheet 28 provided between the shroud 25 and the secondary sodium outlet pipe 26.

The shroud 25 is provided with a through hole 30 for sucking sodium 6 into m, and the secondary sodium outlet pipe 26 is provided with through holes 32 and 33 for allowing the secondary sodium 31 to enter and exit around the heat transfer tube 29. It is being

An outlet nozzle 34 for sodium 6 is provided at the lower end of the shroud 25.

In the tank-type fast breeder reactor configured as described above, the sodium 6 in the lower plenum 15 is pumped through the circulation pump 18.
It passes through the inlet pipe 21 and is fed into the reactor core 2 from the high-pressure plenum 22. - When sodium 6 flows up through the reactor core 2, its temperature increases due to the heat of the reactor core 2.

The heated sodium 6 flows from the reactor core 2 into the upper plenum 14, passes through the hanging shell flow hole 8, and flows into the intermediate heat exchanger 17. It flows into the intermediate heat exchanger 17 through the through hole 30 of the shroud 25 and exchanges heat with the secondary sodium 31 as it passes through the heat transfer tube 29, giving the secondary sodium 31 the heat previously obtained in the reactor core 2. .

The primary sodium 31 whose temperature has been reduced after heat exchange flows into the lower plenum 15 through the outlet nozzle 34 and is again sent into the reactor core 2 by the circulation pump 18.

On the other hand, the secondary sodium 31 is connected to the secondary sodium inlet pipe 27
It flows from the through hole 33 on the inlet side between the secondary sodium outlet pipe 26 and the shroud 25, flows around the heat exchanger tube 29, and exchanges heat with the sodium 6 to m, raising its temperature. The heated secondary sodium 31 passes through the through hole 32 on the outlet side.
The sodium flows through the secondary sodium outlet pipe 26 and is led to a secondary heat exchanger (not shown).

After dissipating heat there, the sodium is pressurized by a secondary pump (not shown) and sent into the intermediate heat exchanger 17 through the secondary sodium inlet pipe 27 again.

(Problems to be solved by the invention) In the tank-type fast breeder reactor configured as described above,
As shown in FIG. 5, the sodium 6 that has flowed up through the reactor core 2 flows into the upper plenum 14, and the sodium 6 that has flowed up through the reactor core 2 flows through the hanger flow hole 8.

However, the sodium 6 in a part of m rises along the inner wall surface of the hanging M4 and reaches the free liquid level of the -order sodium 6, causing liquid level fluctuation. This liquid level fluctuation is particularly large in a portion of the suspension 3514 where the suspension body flow hole 8 is not provided.

Due to this liquid level fluctuation, the cover gas 36 covering the upper part of the primary sodium 6 liquid level is drawn into the sodium 6 into m, and when the sodium 6 mixed with this cover gas 36 circulates through the reactor core 2, the high pressure plenum 22 Gas accumulates inside. This gas pool expands as the temperature rises, making it impossible to properly distribute the flow rate in the reactor core 2, making it difficult to operate the reactor in a healthy manner.

In addition, if the gas mixed in the -order sodium 6 accumulates in the fuel bottle (not shown) installed in the core fuel assembly 9, the cladding tube near the gas will not be cooled by the sodium 6, causing abnormal heat generation. However, in the worst case, the cladding pipe will burst.

In addition, if the free liquid level of -order sodium fluctuates greatly, the liquid level waves will act as a source of vibration for the reactor internal structures such as the upper core mechanism 16 and the hanging shell 4, causing the reactor internal structures to vibrate and cause structural fatigue. Therefore, there is a risk that the integrity of the reactor internals may be impaired due to cracks (fatigue fracture) in the reactor internals.

The present invention has been made in consideration of the above circumstances, and its purpose is to prevent the fluctuation of the free liquid level of primary sodium, prevent the entrainment of cover gas, and prevent the upper core mechanism, suspension structure, etc. An object of the present invention is to provide a tank-type fast breeder reactor that can prevent structural fatigue due to vibrations.

[Structure of the invention]

(Means for solving problems) In the present invention, a reactor core is housed within a reactor vessel.

This reactor core is held in a suspension shell suspended from a roof slab that covers the upper opening of the reactor vessel, and the coolant that has flowed up in the reactor core is circulated through the suspension shell flow hole provided in the suspension shell. In the tank-type fast breeder reactor configured to do so, a guide plate is provided on the inner circumferential surface of the hanging barrel to reduce the vertical flow velocity component of the coolant flowing toward the coolant liquid surface.

(Function) The coolant that has flowed up through the reactor core flows into the upper plenum, and a portion of it flows up along the inner peripheral surface of the suspension barrel. The vertical flow velocity component of the coolant flow is attenuated by the guide plate, and no fluctuations occur in the coolant liquid level.Furthermore, a flow hole can be provided near the liquid level of the suspension shell 4, so that it can be used during thermal transients. Stratified flow can be quickly eliminated.

(Embodiment) An embodiment of a tank-type fast breeder reactor according to the present invention will be described with reference to FIGS. 1 to 3. The schematic structure of the tank-type fast breeder reactor is shown in FIG. 1, and the same members as in FIGS. 4 and 5 are denoted by the same reference numerals and the explanation thereof will be omitted.

A first embodiment of the present invention is shown in FIG.
An inner cylindrical guide plate 40 as a guide plate is provided below the primary sodium 6 liquid level on the inner circumferential surface of the hanging WA4. The guide plate 40 protrudes in a cylindrical shape in the circumferential direction inside the hanging barrel 4 near the free liquid level of the primary sodium 6 .

In this tank-type fast breeder reactor, the primary sodium 6 flowing out from the reactor core section 2 changes its direction radially at the bottom of the upper core mechanism 16 and heads toward the inner wall of the suspension shell 4. A part of the primary sodium 6 flows out from the flow hole 8 and rises along the inner circumferential wall of the suspension barrel 4.

This ascending flow of secondary sodium 6 passes through a circumferential guide plate 40 provided on the inner circumferential surface of the suspension shell 4 and the annulus section of the suspension shell 4, and most of it exits from the flow hole 8 to the outside of the suspension shell. on the other hand,
A flow can also flow back into the suspension shell 4 through the orifice 41.

After passing through this orifice 41, the vertical flow velocity component is attenuated,
- Sodium 6 turns to the side and flows. Therefore, the free liquid level of the -order sodium 6 is prevented from fluctuating. In addition, even when low-flow, low-temperature coolant comes out of the core during scram, the stratified interface inside the suspension shell 4 reaches the height of the suspension shell flow hole 8, so the mixing volume increases and the stratified flow disappears early. Figures 2 and 3 show another embodiment of a tank-type fast breeder reactor, in which an ori-rice 42 of a guide plate 40 provided to form an annulus portion inside the suspension shell 4 is placed at the core center. It is characterized by the holes being opened diagonally. By doing so, there is a weak swirling flow inside the hanging barrel 4, and no jet stream is blown up toward the liquid surface, so it is possible to prevent the liquid level inside the hanging barrel from fluctuating.

〔Effect of the invention〕

The tank-type fast breeder reactor according to the present invention is equipped with a guide plate on the inner circumferential surface of the hanging barrel to decelerate the vertical flow velocity component of the coolant flowing toward the coolant liquid level, thereby preventing the coolant liquid level from swinging. can do.

Therefore, it is possible to prevent entrainment of the cover gas, and also to prevent structural fatigue due to vibrations of the core upper mechanism, suspension shell, etc., thereby maintaining healthy operation of the nuclear reactor.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view of a hanging barrel portion of a first embodiment of a tank-type fast breeder reactor according to the present invention, and FIGS. 2 and 3 show other embodiments of the present invention. FIG. 4 is a schematic configuration diagram of a conventional tank-type fast breeder reactor, and FIG. 5 is an enlarged view of the hanging barrel portion of the conventional example. 1... Reactor vessel, 2... Reactor core, 3...
Roof slab, 4... Hanging shell 6... - secondary sodium, 8... Hanging barrel flow hole, 9... Fuel assembly, 10... Blanket fuel assembly. 11... Reflector, 13... Partition wall. 14... Upper plenum, 15... Lower plenum, 16... Core upper mechanism, 17... Intermediate heat exchanger, 18... Recirculation pump, 36... Cover gas, 40... Information board, 41.42...
Orifice. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. A reactor core is housed in the reactor vessel, and this reactor core is held in a hanging shell suspended from a roof slab that covers the upper opening of the reactor vessel, and the coolant that has flowed up through the reactor core is carried by the hanging shell. In a tank-type fast breeder reactor configured to circulate through a hanging barrel flow hole provided in the shell, the vertical flow velocity component of the coolant flowing toward the coolant liquid level on the inner peripheral surface of the hanging barrel is attenuated. A tank-type fast breeder reactor characterized by the provision of a guide plate.