JPH01244202A - Plug device of heat transfer pipe for intermediate heat exchanger - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention (Industrial Field of Application) The present invention relates to a stopper device for a heat transfer tube for an intermediate heat exchanger in a shell-and-tube type straight tube heat exchanger, particularly in a tank type fast breeder reactor. Pertains to.

(Prior Art) FIG. 2 is a schematic longitudinal sectional view of a conventional tank-type fast breeder reactor. In this figure, a reactor vessel 1 consisting of a main vessel 1a and a guard vessel 1b that protects the outside of the reactor vessel 1 is supported by a cavity wall 2, and a roof slab 3 that closes the upper end opening of the main vessel 1a is A core upper mechanism 7 above a core 6 supported via a plenum part 5 is penetrated by a core support body 4 provided at the bottom of 1a. Further, a partition u8 is provided in the main container 1a to cross the main container 1a, and by this partition 8, the inside of the main container 1a is divided into a hot pool 9 and a cold pool 1o above the partition.

Furthermore, a primary main circulation pump 11 is provided passing through the roof slab 3, and a thin-walled cylinder 1 concentrically surrounds the primary circulation pump 11.
2 passes through the partition wall 8 and terminates in the cold pool 10. Further, the in-furnace pipe 13 on the discharge side of the pump 11 is arranged concentrically with the thin-walled cylinder 12, and its end communicates with the plenum portion 5.

Further, an intermediate heat exchanger 14 which is a shell and tube type heat exchanger is provided passing through the roof slab 3, and the lower end of this intermediate heat exchanger 14 passes through the front bulkhead 8 and enters the cold pool 10. It is terminated. In addition, in the figure, 8a indicates a partition wall support, and 8b indicates an opening for supporting an intermediate heat exchanger.

FIG. 3 is a longitudinal sectional view showing details of the intermediate heat exchanger 14. In this figure, the intermediate heat exchanger 14 is connected to the roof slab 3
It has a double pipe including an outer shell 16 perpendicular to the outer shell 16, and an outer pipe 17 and an inner pipe 18 arranged at the axis of the outer shell to circulate the secondary coolant, and the partition wall at the lower part of the outer shell 16. Support 8
An inner shell 19 having a similar shape to the lower part of the outer shell 16 is provided below b. Further, a lower tube plate 20 and an upper tube plate 21 are installed at the upper end of the inner shell 19 and the axial middle part of the outer shell 16, respectively, and the tube plates 20 and 21 are connected to form a plurality of heat transfer tubes 22.
is provided.

In addition, the upper part of the outer shell 16 of the intermediate heat exchanger 14.

That is, the outer periphery of the portion slightly above the upper tube plate 21 is covered by a concentric cylindrical skirt 23 hanging from the lower surface of the roof slab 3, and the lower portion of the outer shell 16,
That is, the outer circumference of the portion from slightly below the upper tube plate 21 to the lower end of the outer shell 16 is 1)? 1. It is covered by a stand pipe 24 hanging down from the partition wall 8.

Further, the outer shell 16 is provided with a plurality of windows 25 for the primary coolant 15 distributed in the circumferential direction at positions covered by the skirt 23 . Further, a dip tube 26 is provided along the axis of the inner tube 18 of the double tube, and this tube is terminated in contact with a chain plate 18a at the lower end of the inner tube 18. Further, a secondary coolant outlet 27 is provided in the outer tube 17 at the double end thereof.

In addition, in the figure, 16a is a flange for attaching the outer shell 16 to the roof slab 3, and 28 is the outer shell 16 of the intermediate heat exchanger and exchanger.
29 indicates a heat shield provided near the upper end, 29 indicates a radiation shield provided stacked thereon, and 30 indicates a section between the lower end of the outer shell 16 and the lower end of the inner shell 19, between the lower end of the outer shell 1 (3) and the stand pipe 2.
4 shows bellows which are provided between each member and the lower end thereof to absorb the difference in thermal expansion between these members.

In the conventional fast breeder reactor with the above configuration, the hot pool 9
The high-temperature primary coolant 15 flows into the outer shell 16 through the window 25 of the outer shell 16 of the intermediate heat exchanger 14, and
In the inner heat transfer tube bundle 22a, the coolant exchanges heat with the secondary coolant flowing inside the inner and outer tubes to become low temperature, and flows into the cold pool 10 from the lower end of the outer shell by natural convection. The low-temperature primary coolant in the cold pool 10 is forcibly sent to the reactor core 6 by the main circulation pump 11, where it becomes high temperature again and rises toward the hot pool 9.

When the fast breeder reactor is healthy, primary sodium exists above the upper tube sheet 21, below the lower tube sheet 20, and within the heat transfer tubes 22 in the in-tube-upstream flow path type intermediate heat exchanger.
Secondary sodium exists outside the heat exchanger tube 22 in the space between the upper and lower tube sheets. If leakage occurs in the heat exchanger tube 22, the boundary between the secondary side and the downstream side will disappear, so repairs must be performed.

By the way, when leakage occurs in the heat transfer tubes 22 in the fast breeder reactor intermediate heat exchanger 14 having the above structure, conventionally, the intermediate heat exchanger is pulled out of the reactor vessel 1 and repaired.

(Problem to be Solved by the Invention) In order to pull the intermediate heat exchanger out of the reactor vessel for the above-mentioned repair, it is necessary to cut the piping of the secondary side cooling system that connects to the intermediate heat exchanger. It is also necessary to use casks to store and transport the intermediate heat exchanger to the site of repair. This cask is extremely heavy due to its strong radiation shielding performance, and although the crane capacity of the building is only needed for repairs, it can withstand the combined weight of the intermediate heat exchanger and cask. Must be.

Further, not only is the intermediate heat exchanger itself radioactive due to use, but also radioactive corrosion products adhere to it during use, which poses many problems in carrying out repair work. For example, apart from activation of the intermediate heat exchanger, radioactive corrosion products can be removed by cleaning, but this cleaning generates large amounts of radioactive waste. Furthermore, even if cleaning is performed, the intermediate heat exchanger itself is activated, and it is difficult to completely remove deposits by cleaning, so repairs must be performed by robots.

The present invention has been made based on the above-mentioned circumstances, and when a leak occurs in a heat transfer tube of an intermediate heat exchanger, the leaking heat transfer tube is plugged and closed without having to be pulled out from the reactor vessel. The aim is to provide an intermediate heat exchanger that can be replaced by repair.

[Structure of the Invention] (Means for Solving the Problems) The stopper device for heat transfer tubes for an intermediate heat exchanger of the present invention is for external use;
It is used in an intermediate heat exchanger that has a tube bundle consisting of a large number of heat transfer tubes housed in this outer shell and whose upper and lower ends are supported by upper and lower tubes, and has an outer diameter and an axial length that can be inserted into the heat transfer tubes. It consists of a cylindrical plug with one end closed, which is larger than the axial length of the heat transfer tube, and a tube expansion mechanism installed within the plug with a distance equal to the distance between the upper and lower tube sheets, which prevents leakage. The plug is inserted into the heat exchanger tube, and the tube expansion mechanism is activated.

(Function) The stopper device for a heat transfer tube for an intermediate heat exchanger of the present invention having the above configuration has the following features:
If a leak occurs in a heat exchanger tube, the intermediate heat exchanger can be repaired without having to pull the intermediate heat exchanger out of the reactor vessel by simply putting a stopper on the leaking heat exchanger tube. As a result, various problems such as installation of large-capacity cranes associated with extraction, increase in radioactive waste, and deterioration in the workability of repair work by robots can be solved all at once.

(Embodiment) FIG. 1, in which the same parts as in FIG. 2 are denoted by the same reference numerals, is an enlarged vertical sectional view of a main part of an embodiment of the present invention.

In this figure, the heat transfer tube 22 is provided by connecting an upper tube sheet 21 and a lower tube sheet 22, and has its upper end opened into the outer shell 16 and its lower end opened into the inner shell 19. Inside the tubular plug 31, which is longer than the heat transfer tube 22 and closed at one end, there are tube expansion mechanisms 32 arranged at intervals equal to the interval between the upper and lower tube plates 21 and 20.
is installed. The tube expansion mechanism 32 expands the diameter of the plug 31 from the inside using a hydraulic mechanism or other appropriate means.

When a leak occurs, it is detected by an appropriate means (not shown), and the heat exchanger tube in which the leak occurs is detected. The plug 31 is then inserted into the heat transfer tube 22 identified as having leaked from outside the reactor vessel 1 by remote control. Here, plug 3
1, the tube expansion mechanism 32 installed near the upper and lower ends of the inside of the plug 31 with a gap between the upper and lower tube plates 21 and 20 is activated.
The corresponding portion is enlarged and brought into pressure contact with the opening of each tube plate 20, 21 of the heat exchanger tube 22. As a result, the openings at the upper and lower ends of the heat exchanger tube are closed, and the damage to the barrier between the downstream side sodium and the secondary side sodium is repaired when the closure is completed.

Note that the present invention is not limited to the above embodiments.

For example, the middle part of the plug 31 may be made into a bellows to have enough flexibility to function as a plug. When doing this, in order to eliminate the temperature difference that occurs between the plugged heat exchanger tube and other healthy heat exchanger tubes that occurs during plugging, it is necessary to The difference in thermal expansion between the two can be absorbed by the bellows portion.

[Effects of the Invention] In the present invention, when a leak occurs in a heat transfer tube, the leaky heat transfer tube is sealed without pulling the intermediate heat exchanger out of the reactor vessel, thereby improving the integrity of the reactor. It is possible to prevent the leakage results from spreading to others.

Furthermore, since repairs can be carried out without having to pull out the intermediate heat exchanger, problems such as the installation of large-capacity cranes, an increase in radioactive waste, and deterioration of the workability of repair work by robots are caused by the removal. can be solved all at once.

[Brief explanation of the drawing]

Fig. 1 is an enlarged vertical cross-sectional view of essential parts of an embodiment of the present invention, Fig. 2 is a schematic longitudinal cross-sectional view showing a conventional tank-type fast breeder reactor, and Fig. 3 is an intermediate view of the fast breeder reactor shown in Fig. 2. FIG. 3 is an enlarged vertical cross-sectional view of the main parts of the heat exchanger.

Claims (1)

[Claims] An outer shell that can be inserted into the heat exchanger tubes and is used in an intermediate heat exchanger that has an outer shell and a tube bundle consisting of a large number of heat transfer tubes housed in the outer shell and whose upper and lower ends are supported by upper and lower tube plates. It consists of a cylindrical plug with one end closed and an axial length larger in diameter than the axial length of the heat transfer tube, and a tube expansion mechanism provided within the plug at a distance equal to the distance between the upper and lower tube sheets. A stopper device for a heat transfer tube for an intermediate heat exchanger, characterized in that the plug is inserted into a leaking heat transfer tube to operate the tube expansion mechanism.