JPH01176976A - Tank type fast breeder - Google Patents

Abstract

PURPOSE:To relax the heat stress of a heat-transfer tube and a tube plate and to improve the performance of a nuclear reactor by employing a bellows structure between the upper tube plate of heat-transfer tubes arranged in the shroud 20 of an intermediate heat exchanger and a through-hole for secondary sodium outflow. CONSTITUTION:In the shroud 20 forming the main body barrel of the intermediate heat exchanger, the upper tube plate 24 and a lower tube plate 25 are arranged at an axial interval, and the heat-transfer tubes 23 to which a bellows 50 is connected are arranged between the upper and lower tube plates. The intake hole 26 is bored in the shroud 20 above the tube plate 24 and primary sodium flows in through the hole 22 from the hole 26 from above the heat-transfer tubes 23. Secondary sodium, on the other hand, flows in through a through-hole 27 bored in the secondary sodium tube 22 and flows out of a hole 28. The temperature difference between the primary sodium and secondary sodium or an irregularity of the temperature distribution generates heat stress in the heat-transfer tubes 23 to generate a buckling phenomenon with high possibility. The bellows 50, however, is connected nearby the upper part of the heat-transfer tubes 23, so the expansion of the heat-transfer tubes 23 due to heat stress is absorbed to preclude a breakage.

Description

[Detailed Description of the Invention], [Objective of the Invention] (Industrial Application Field) The present invention relates to a tank-type fast breeder reactor, and particularly to a tank-type fast breeder reactor that can be operated with the intermediate heat exchanger plenum filled with primary coolant. Regarding tank-type fast breeder reactors.

(Prior art) Tank-type fast breeder reactors generally use liquid metallic sodium as primary and secondary coolants, and the primary sodium heated in the reactor core is guided to an intermediate heat exchanger installed in the reactor vessel. It exchanges heat with secondary sodium, and the cooled primary sodium is sent back to the reactor core.

FIG. 3 shows the schematic configuration of a conventional tank-type fast breeder reactor. In the center of the core fuel assembly 5,
A reactor core 8 consisting of a blanket fuel assembly 6 and a reflector 7 is installed.

- A core upper mechanism 10 is installed through the center of the roof slab 9 that closes the upper end of the reactor vessel 1,
A plurality of intermediate heat exchangers 11, a plurality of circulation pumps 12, etc. are independently installed around this.

13 indicates a motor that drives the circulation pump 12, and
The discharge side of the circulation pump 12 is connected via an inlet pipe 14.

It is connected to the high pressure premna 15.

The intermediate heat exchanger 11 includes a shroud 20, a secondary sodium inlet pipe 21 and a secondary sodium outlet pipe 22 coaxially arranged in the center thereof, and the secondary sodium outlet pipe 22.
It includes a large number of heat exchanger tubes 23 inserted into a heat exchange chamber formed between the shroud 20 and an upper tube sheet 24 and a lower tube sheet 25 that support these heat exchange tubes 23.

Further, the shracto 20 is provided with an inflow hole 26 for sucking in primary sodium, and the outlet pipe 22 is provided with a through hole 27 for allowing secondary sodium to enter and exit the outside 1 of the heat transfer tube 23.
．． 2B is provided, and a primary sodium outlet 29 is provided at the lower end.
is provided.

Further, a partition wall 38 is provided at the upper part of the intermediate heat exchanger plenum 34.
is provided, and this partition wall 38 is connected to the intermediate heat exchanger upper space 3.
7 and an intermediate heat exchanger plenum 34.

During operation, a free liquid level is formed inside the intermediate heat exchanger plenum 34 at a height approximately equal to the primary coolant and liquid level in the upper plenum 3. The space 41 above the free liquid level is filled with a cover gas, such as argon, to avoid contact between the primary coolant and air.

In this tank-type fast breeder reactor, primary sodium in the upper plenum 3 passes through the inlet hole 26 and passes through the intermediate heat exchanger 11.
shroud 20 , flows through heat transfer tubes 23 from upper tubesheet 24 , through lower tubesheet 25 and primary sodium outlet 29 , and into lower plenum 4 .

The primary sodium that has flowed into the lower plenum 4 is sent into the inlet pipe 14 by the circulation pump 12 driven by the drive motor 13, and then roughly passes through the high pressure plenum 15.
It ascends through the gap between the core fuel assembly 5 and the blanket fuel assembly 6, during which time the primary sodium is heated.

The heated primary sodium impinges on the lower end of the upper core structure 10, changes its flow radially, and flows back into the intermediate heat exchanger plenum 34 through the inlet holes 26.

On the other hand, the secondary sodium flows inside the inlet pipe 21 toward the lower tube plate 25, passes through the through hole 27 provided near the lower end of the outlet pipe 22, which forms a double pipe with the inlet pipe 21, and passes through the outlet pipe 22 and the shroud 20. It flows into the heat exchange chamber formed between the heat exchanger tubes 23
After exchanging heat with some of the sodium passing through the hole, the through hole 2
8 flows through the outlet pipe 22 and is led to a secondary heat exchanger (not shown). After dissipating heat in this secondary system heat exchanger, the secondary sodium is pressurized by a secondary sodium circulation pump (not shown), passes through the secondary sodium inlet pipe 21 again, and is returned to the intermediate heat exchanger 11.

(Problems to be Solved by the Invention) In the structure of a conventional tank-type fast breeder reactor, an intermediate heat exchanger 1 is installed in the upper plenum 3 so as to penetrate the partition wall 2.
1 is arranged. Since the intermediate heat exchanger plenum 34 is provided to contain the liquid level position of the primary sodium in the upper plenum 3, a free liquid level of the primary sodium flowing into the intermediate heat exchanger plenum 34 is always formed.

A portion of the primary sodium that has flowed into the intermediate heat exchanger 11 through the inflow hole 26 collides with the secondary sodium outlet pipe 22,
A part of the primary sodium collided at this time is blown up onto the free liquid surface by dynamic pressure and falls onto the free liquid surface. As a result, the fluctuation of the free liquid level in the intermediate heat exchanger plenum 34 becomes large, and the inflow to each heat exchanger tube in the heat exchange chamber becomes uneven, and the cover gas filled on the free liquid level becomes This causes it to get caught up in sodium.

If the flow surrounding each heat exchanger tube 23 becomes non-uniform, there is a possibility that thermal deformation of the heat exchanger tubes and tube sheets will occur due to the temperature difference.

The present invention was devised to solve the above-mentioned problems, and it alleviates the thermal stress of multiple heat transfer tubes and tube sheets provided in an intermediate heat exchanger, thereby making it possible to improve the performance of a nuclear reactor. The purpose of this project is to provide a tank-type fast breeder reactor.

[Structure of the invention]

(Means for solving the problems) A tank-type fast breeder reactor according to the present invention. The interior of the reactor vessel containing the reactor core and primary coolant is partitioned into an upper plenum and a lower plenum by a partition, and an intermediate space passes through the partition wall to exchange heat between the primary coolant and the secondary coolant within the reactor vessel. In a tank-type fast breeder reactor equipped with a heat exchanger and a circulation pump for circulating a primary coolant, an upper tube plate and a lower tube are arranged at intervals in the axial direction in the shroud of the intermediate heat exchanger. It is characterized by having a bellows structure between the upper tube plate of the plurality of heat exchanger tubes provided between the plate and the through hole for secondary sodium outflow.

(Function) In the present invention, it is considered that there is a high possibility that buckling will occur in each heat transfer tube due to thermal stress etc. due to non-uniform temperature of the primary coolant flowing into the intermediate heat exchanger. Therefore, a bellows is connected near the end of each heat exchanger tube on the upper tube plate side, and the expansion and contraction of the heat exchanger tube due to uneven temperature distribution is absorbed by the deformation of the bellows. As described above, it is possible to provide a tank-type fast breeder reactor with excellent structural soundness.

(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a partial vertical sectional view showing a first embodiment of a tank-type fast breeder reactor according to the present invention, which is a particularly characteristic feature of the invention.

FIG. 3 is a longitudinal sectional view partially showing an intermediate heat exchanger.

In FIG. 1, in the shroud 20 forming the main body of the intermediate heat exchanger, there are upper tube plates 24 spaced apart in the axial direction.
and a lower tube plate 25 are disposed, and a plurality of heat exchanger tubes 23 with bellows 50 connected therebetween are disposed. Upper tube plate 2
Above 4, an annular section surrounded by shroud 20 forms an intermediate heat exchanger plenum 34. Rough upper tube plate 2
4 The upper shroud 20 has primary sodium inflow holes 2
6 is drilled.

The primary sodium passes through the inflow hole 26 and flows in from the upper part of the plurality of heat transfer tubes 23 . On the other hand, secondary sodium flows in through the through hole 27 and flows out through the through hole 28.

There is a temperature difference between the primary sodium and the secondary sodium, so heat exchange takes place here, but that temperature difference or
There is a high possibility that thermal stress will occur in the plurality of heat transfer tubes 23 due to uneven temperature distribution of the primary and secondary sodium, and buckling phenomenon will occur, but near the top of the plurality of heat transfer tubes 23,
Since the bellows 50 are connected, expansion and contraction of the plurality of heat exchanger tubes 23 due to thermal stress can be absorbed and damage can be prevented. As described above, it becomes possible to improve the safety, thermal efficiency, and mechanical soundness of the tank-type fast breeder reactor.

〔Effect of the invention〕

According to the tank-type fast breeder reactor according to the present invention, a bellows is connected to the vicinity of the upper ends of a plurality of heat transfer tubes fixed by an upper tube sheet and a lower tube sheet in the intermediate heat exchanger. The bellows deforms and absorbs the expansion and contraction of the heat exchanger tubes caused by temperature differences and uneven temperature distribution.

As described above, it is possible to prevent buckling deformation and damage of the plurality of heat transfer tubes, improve the soundness of the intermediate heat exchanger, and provide a highly reliable tank-type fast breeder reactor.

[Brief explanation of the drawing]

FIG. 1 is a partial vertical sectional view showing an embodiment of the tank-type fast breeder reactor intermediate heat exchanger of the present invention, FIG. 2 is a vertical sectional view of a conventional intermediate heat exchanger, and FIG. This is a longitudinal section showing the structure of a breeder reactor. 1... Reactor vessel 2... Partition wall 3... Upper plenum 4... Lower plenum 5... Core fuel assembly 6... Blanket fuel assembly 7... Reflector 8...・Reactor core part 9... Roof slab 10... Core upper mechanism 11... Intermediate heat exchanger 12... Circulation pump 13... Drive motor 14... Inlet piping 15... High pressure plenum 20. ...Shroud 21...Secondary sodium inlet pipe 22...Secondary sodium outlet pipe 23...Heat transfer tube 24...Upper tube plate 25
... Lower tube plate 26 ... Inflow hole 27 ...
Through hole 28...Through hole 29...Primary sodium outlet 34...Intermediate heat exchanger plenum 37...Intermediate heat exchanger upper space 38...Partition wall agent Patent attorney Norihiro Ken Yudo No. Ken Komaru Figure 1 Figure 2

Claims (1)

[Claims] The inside of the reactor vessel containing the reactor core and the primary coolant is partitioned into an upper plenum and a lower plenum by a partition wall, and an upper part penetrates the partition wall to exchange heat between the primary coolant and the secondary coolant within the reactor vessel. In a tank-type fast breeder reactor equipped with an intermediate heat exchanger having a plurality of heat transfer tubes fixed by a tube sheet and a lower tube sheet, and a circulation pump that circulates the primary coolant, the upper tube sheet and the secondary sodium A tank-type fast breeder reactor characterized in that the upper end of the heat transfer tube between the outflow holes has a bellows structure.