JPS61176886A - 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 [Technical Field of the Invention] The present invention relates to a reactor vessel installation type fast breeder reactor used for heat exchange between a primary cooling system and a secondary cooling system of a liquid metal cooled tank type fast breeder reactor, for example. The present invention relates to an intermediate heat exchanger, and particularly to an intermediate heat exchanger with an improved primary coolant inlet.

[Technical background of the invention and its problems] In a liquid metal cooled tank type fast breeder reactor, a primary coolant in a tank main vessel serving as a reactor vessel and a secondary coolant circulating in a secondary cooling system including a steam generator are used. A liquid metal such as liquid sodium is used as the coolant, and an intermediate heat exchanger for exchanging heat between the primary coolant and the secondary coolant is installed inside the tank main vessel. That is, as shown in FIG. 4, the tank main vessel 1 is covered above with a roof slab 2, and a plurality of intermediate heat exchangers 3 are mounted on the roof slab 2 at intervals along with a primary circulation pump 5 around the reactor core 4. is suspended from. A safety container 7 is installed outside the tank main container 1 in case the primary coolant 6 leaks.

As shown in FIG. 5, for example, the intermediate heat exchanger 3 is mainly composed of an intermediate cylindrical body 8 vertically suspended from the roof slab 2. This shell 8 has a structure in which primary coolant nI material inlet windows 9 are provided at intervals in the circumferential direction in the upper part of the peripheral wall, and a primary coolant outlet nozzle 10 is provided in the lower end.

Between the primary cold W material inlet window 9 of this shell 8 and the primary coolant outlet nozzle 10, a large number of heat transfer tubes 13 whose upper and lower ends are supported by an upper tube sheet 11 and a lower tube sheet 12 are arranged vertically. arranged,
The primary coolant 6 flows down inside the heat transfer tube 13. In addition, a secondary coolant-filled nozzle 1 is installed at the upper end of the body 8.
4 and a secondary coolant outlet nozzle 15 are provided, and a downcomer pipe 16 communicating with the secondary coolant inlet nozzle 14 hangs down to the lower tube plate 12 at the axial center of the shell 8, and the secondary coolant outlet nozzle 1
An ascending pipe 17 communicating with the descending pipe 16 surrounds the descending pipe 16 and hangs down to the upper tube plate 11. This descending pipe 16 and rising pipe 1
7 is the air formed between the upper tube sheet 11 and the lower tube sheet 12 through the communication ports 16a and 17a, that is, the heat exchange room 1.
As a result, when the secondary coolant flows from the downcomer pipe 16 to the riser pipe 17, it comes into contact with the outer peripheral surface of the heat transfer tube 13 in the heat exchange chamber 18 and exchanges heat with the primary coolant 6.

In the tank main vessel 1, the primary coolant 6 which has become 'Ii&m' above the core 4 flows into the intermediate heat exchanger 3 through the primary coolant inlet window 9 at the top of the shell 8, and flows down inside the heat transfer tube 13. Sometimes 2
After exchanging heat with the secondary coolant, it flows out from the primary coolant outlet nozzle 10, passes through the primary circulation pump 5, and cools the core 4 again.

In addition, the secondary coolant flows into the intermediate heat exchanger 3 from the secondary coolant nozzle 14 at the upper part, and enters the heat exchanger tube 13 in the heat exchange chamber 18.
After contacting the outer circumferential surface of the coolant and exchanging heat with the primary coolant, the coolant is circulated through the secondary coolant outlet nozzle 15 to the secondary cooling system.

Incidentally, such an intermediate heat exchanger 3 is used not only to generate steam in a steam generator (not shown) of the secondary cooling system during normal operation of the nuclear reactor, but also to generate destruction heat even after the reactor trips. Used for removal operations. That is, in order to cool the reactor core 4, which is continuously heated by destruction heat, the primary circulation pump 5 is operated auxiliary, and an air cooler (not shown) branched into the secondary cooling system is used to cool down the secondary cooling system. This allows heat to be dissipated via the coolant. During this breakdown heat operation, the primary coolant 6 thermally contracts due to a decrease in temperature, and becomes a liquid level lower than the normal liquid level NSL during normal output operation, that is, the liquid level at stop (FsL). Therefore, the primary coolant inlet window 9 provided in the shell 8 of the intermediate heat exchanger 3 requires a certain height in order to allow the primary coolant 6 to flow in regardless of the liquid level.

Furthermore, in the unlikely event that the tank main container 1 leaks, the liquid level of the primary coolant 6 will decrease by the amount that leaks into the safety container 7, so the primary coolant inlet window 9 will be closed when the liquid is stopped. Place Fs
It is necessary to support the emergency liquid level ESL which is lower than L.

On the other hand, the upper tube plate 1 forming the heat exchange part of the intermediate heat exchanger 3
1 needs to be placed a predetermined distance below the primary coolant inlet 1!9 in order to ensure uniform flow distribution of the primary coolant 6 to each heat transfer tube 13. Therefore, if the length L from the bottom surface of the roof slab 2 to the primary coolant outlet nozzle 10 of the intermediate heat exchanger 8 is constant, the effective heat exchange length, that is, the heat transfer -13 length is the primary coolant This will be greatly influenced by the height of the entrance window 9.

In the conventional intermediate heat exchanger, as shown in FIG. 5, the primary coolant liquid level at the primary coolant inlet window 9 is the same as the primary coolant liquid level in the tank main vessel. As a result, the lower end position of the primary coolant inlet window 9 must be positioned below the emergency liquid level EsL, and the length of the heat transfer tube 13 is accordingly shortened. Therefore, in order to secure a certain heat transfer area, a large number of heat transfer tubes 13 are required, and the diameter of the shell 8 becomes correspondingly large, which is one of the causes of increasing the size of the nuclear reactor plant.

[Purpose of the Invention] The present invention was made in view of the above circumstances, and it is possible to increase the diameter or length of the shell, make the structure more compact, and moreover, it is possible to make the structure more compact, and moreover, it is possible to increase the diameter or length of the shell. An object of the present invention is to provide an intermediate heat exchanger that can efficiently perform heat exchange operations.

[Summary of the Invention] In the present invention, the reactor is vertically installed in the reactor vessel, primary coolant inlet windows are bored at intervals in the circumferential direction in the surrounding wall earth part, and the primary coolant is installed in the lower end of the reactor. A shell provided with a material extraction nozzle, a pipe for secondary coolant circulation provided inside this shell,
It is provided between the primary coolant inlet window and the primary coolant outlet nozzle of the shell, and is provided between the primary coolant and the secondary coolant to reduce the heat of the primary coolant and the secondary coolant. In an intermediate heat exchanger equipped with a heat exchange section for performing exchange, a cylindrical flow skirt that opens below the falling liquid level of the primary coolant in an emergency is provided around the shell, and the surrounding reactor Even when the liquid level in the container decreases, the cover gas pressure provided in the cylinder is adjusted to maintain and control the primary coolant liquid level in the flow skirt at a high level by adjusting the cover gas pressure in the flow skirt. It is characterized by a configuration consisting of an intake and exhaust pipe, a vent hole bored in the body, a liquid level gauge provided in the body, and a liquid level control device connected to these.

In the above, a cover gas intake and exhaust pipe is provided in the cover gas section of the reactor vessel, and the primary coolant liquid level in the flow skirt is maintained and controlled at a high level by adjusting the cover gas pressure of the reactor vessel. The intermediate heat exchanger as described above.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

It should be noted that the same reference numerals as in FIGS. 4 and 5 are used for corresponding parts in the figures for the same components as in the prior art.

The intermediate heat exchanger 3 according to this embodiment has a cylindrical flow skirt around the shell 8 that opens below the emergency liquid level EsL of the primary coolant 6 in case of a leak in the tank main container 1. 20, a cover gas intake and exhaust pipe 23 is provided in the cover gas space 27 in the upper part of the body 8, and a plurality of vent holes 24 are provided in the upper part of the body 8 to communicate the cover gas space 11127 and the cover gas space 28 in the upper part of the flow skirt. A liquid level gauge 25 for measuring the primary coolant liquid level 1xL in the shell 8 is provided, and a liquid level control device 26 connected to the liquid level gauge 25 and the intake/exhaust pipe 23 is provided. The heat exchange chamber 18 is composed of an upper tube plate 11, a lower tube plate 12, and a heat exchange tube 13, which are supported at their upper and lower ends and allow the primary coolant to flow down therein, as in the conventional case. . Then, the secondary coolant is supplied to the downcomer pipe 16 and the riser pipe 17 in the heat exchange chamber 18.
It is assumed that it will be distributed through.

The upper part of the flow skirt 20 has an airtight structure, and the cover gas space rM28 in the upper part of the flow skirt and the cover gas space 29 in the tank main container have independent pressure conditions.
Further, the space between the flow skirt 20 and the shell 8 is designed to have a sufficient cross-sectional area as a flow path through which the primary coolant flows.

The upper tube plate 11 is provided below the primary coolant inlet window 9 at a distance C. required for flow distribution. The primary coolant inlet window 9 only needs to be below the normal liquid level NsL,
The position inside the tank main container 1 is set higher than that in the conventional case.

The lower tube plate 12 is connected to the primary coolant outlet nozzle 10 via a lower header 21, and the primary coolant outlet nozzle 10 and the lower end of the li8 are connected by an expansion joint 22.

The rest of the structure is the same as the conventional one, so corresponding parts in the figures are given the same reference numerals as in FIGS. 4 and 5, and their explanation will be omitted.

The primary coolant liquid level in the flow skirt 9 (pL is 1xL at the primary coolant inlet window 9 from the primary coolant liquid level 1xL in the shell 8).
The liquid level is higher due to the pressure loss when the secondary coolant 6 flows in, but the liquid level is approximately the same. The primary coolant liquid level 1xL in the shell 8 is measured by the liquid level gauge 25, and the cover gas pressure in the cover gas space 27 in the upper part of the shell is controlled through the cover gas intake and exhaust pipe 23 so that the liquid level is constant. The liquid level is adjusted by the liquid level control device 26 by taking in and out the cover gas. Therefore, the primary coolant liquid level IFL in the flow skirt is also controlled to be substantially constant.

During normal reactor power operation, the primary coolant liquid level 1xL in the shell 8 and the liquid level NsL in the tank main vessel are approximately the same liquid level. The primary coolant 6, which has become high in temperature due to the heat generated in the core 4, flows from the lower end of the flow skirt 20 and into the shell 8 through the primary coolant inlet window 9. And heat exchanger tube 13
As it flows down, it exchanges heat with the secondary coolant, flows out from the primary coolant outlet nozzle 10, passes through the primary circulation pump 5, and cools the core 4 again.

On the other hand, in the unlikely event of a leakage accident in the tank main container 1, the leaked primary coolant 6 is stored in the safety container 7,
The liquid level in the tank main container 1 is the emergency liquid level ESL in the long term.
may drop to.

However, the liquid level IFL in the flow skirt 9 and the liquid level 1xL in the shell 8 are controlled by the liquid level control device 26 to approximately the same liquid level as during normal reactor power operation.

In this case, the reactor is scrammed, and the primary coolant 6 that has become high in temperature due to decay heat generated in the reactor core 4 is circulated by the auxiliary operation of the primary circulation pump 5 and flows into the flow skirt 20 from the lower end. Then, in the same way as during normal reactor power operation, the primary coolant flows into the shell 8 through the inlet window 9, exchanges heat with the secondary coolant, flows out from the primary coolant outlet nozzle, and 1
Next, the core 4 is cooled again via the main circulation pump. In addition, 2
Heat is removed from the secondary coolant by an air cooler provided in a secondary cooling system (not shown), and the primary coolant is cooled in the intermediate heat exchanger 3.

According to the intermediate heat exchanger according to this embodiment, by controlling the liquid level of the primary coolant in the flow skirt 20, the installation position of the primary coolant inlet window 9 can be changed compared to the conventional one. It gets expensive. Therefore, the position of the upper tube plate 11 also becomes higher.

Therefore, for example, when the hanging length of the intermediate heat exchanger 3 from the leaf slab 2 is constant, the length of the heat transfer tube 13 can be made larger than that of the conventional one, and the required heat transfer area is the same. If there is, the number of heat transfer tubes 13 can be reduced, and the diameter of the tube bundle, that is, the diameter of the body can be reduced, which can contribute to making the intermediate heat exchanger and the nuclear reactor plant more compact.

[Effects of the Invention] As detailed in the above embodiments, the intermediate heat exchanger according to the present invention has a structure in which the primary coolant liquid level in the flow skirt can be kept constant at all times. Therefore, the primary coolant flow path in an emergency can be secured without any hindrance, and the primary coolant flow path in an emergency can also be secured without any hindrance, and the decay heat of the core can be removed through the intermediate heat exchanger in an emergency. This can be done safely.

Furthermore, it becomes possible to set the primary coolant inlet window higher than in the conventional case, and it becomes possible to arrange the upper tube plate at a higher place than in the conventional case. Therefore, when using a shell with a constant hanging length inside the furnace vessel, the effective length of the heat exchange section, such as the length of the heat transfer tube, can be made larger than before, which reduces the shell diameter and eventually The reactor vessel can be downsized, contributing to the downsizing of the entire nuclear couple.

In the above embodiment, the cover gas intake/exhaust pipe 23 was connected to the cover gas space 27 in the upper part of the intermediate heat exchanger as shown in FIG. 2, but as shown in FIG. It may also be connected to the cover gas space 29. in this case,
There is an advantage that the cover gas pressure in the tank main vessel 1 and the liquid level IXL in the intermediate heat exchanger shell can be adjusted at the same time.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention,
Fig. 1 is a layout configuration diagram showing the installed state in the furnace, Fig. 2 is a partial sectional view showing an enlarged intermediate heat exchanger, Fig. 3 is a partial sectional view showing another embodiment of the present invention, and Fig. 4 is a partial sectional view showing an enlarged intermediate heat exchanger. 5 and 5 show a conventional example, with FIG. 4 being an arrangement diagram and FIG. 5 being a partial sectional view. 1...Furnace vessel 3...Intermediate heat exchanger 4...
......Reactor core 6...Primary coolant 8...
...Body 10...Primary coolant outlet nozzle 1
3...Heat exchange tube (heat exchange section) 16.
......Secondary coolant downcomer pipe 17...
......Secondary coolant riser pipe 18...
......Heat exchange chamber (heat exchange section) 20...
・・・・・・Flow skirt 23・・・・・・・・・・・・
...Cover gas intake and exhaust pipe 24...
・Vent hole 25...Liquid level gauge 26...Liquid level control device Patent attorney Satoshi Suyama - Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (3)

[Claims] (1) A shell is arranged vertically in the reactor vessel of a nuclear reactor, and has primary coolant inlet windows perforated at intervals in the circumferential direction in the upper part of its peripheral wall, and heat generated by two coolants inside this shell. A cylindrical flow skirt that is provided around the shell and opens below the lowered liquid level of the primary coolant in an emergency; In order to maintain the primary coolant liquid level in the skirt at a high level even when the liquid level in the surrounding reactor vessel decreases, a cover gas intake/exhaust pipe provided in the shell and a vent hole bored in the shell. and a liquid level gauge provided in the shell. (2) The intermediate heat exchanger according to claim 1, wherein a liquid level control device is connected to the liquid level gauge and the cover gas intake/exhaust pipe. (3) The intermediate heat exchanger according to claim 1, wherein the cover gas intake and exhaust pipe is connected to a cover gas space in an upper part of the furnace vessel.