JPH04219476A - Sodium pump - 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]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sodium pump suitable for, for example, a primary main coolant circulation pump in a pool-type fast breeder reactor that uses liquid metal as a coolant.

0003

2. Description of the Related Art A pool type fast breeder reactor incorporating a sodium pump will be described with reference to FIGS. 2 and 3. Inside the reactor vessel 1, there is a core support structure 2 as shown in FIG.
A reactor core 3 is accommodated in the center via a roof slab 4, while the top of the reactor vessel 1 is closed off with a roof slab 4. An intermediate heat exchanger 5 and a primary coolant circulation pump 6 are supported on the roof slab 4, and a control rod drive mechanism 7 that constitutes a core upper mechanism is provided above the core 3, passing through the roof slab 4. . Discharge port 8 of primary coolant circulation pump 6
is connected to the in-furnace piping 9 and communicates with the inside of the reactor core 3.

[0004] Also, a high-temperature coolant (liquid metal sodium is generally used as a coolant) is stored in the reactor vessel 1 as pool water, and a hot pool 11 and a cold pool 12 are stored in the reactor vessel 1 . are vertically divided by a standpipe 14 which is a cylindrical partition, 10 indicates the hot pool liquid level, 13 indicates the cold pool liquid level, and 15 indicates the cover gas space. Argon gas is generally used as an inert gas in this cover gas space 15, and the pressure is always maintained higher than atmospheric pressure while the primary coolant circulation pump 6 is operating.

In this fast breeder reactor, high-temperature sodium heated in the reactor core 3 flows into the hot pool 11, and the sodium in the hot pool 11 flows into the intermediate heat exchanger 5, where it exchanges heat with the sodium flowing through the secondary system. Heat is transferred to this secondary sodium. The low temperature primary sodium cooled by heat exchange in the intermediate heat exchanger 5 is transferred to the cold pool 12.
The coolant is sucked into the suction port 16 of the primary coolant circulation pump 6 via the coolant. The sodium sucked into the suction port 16 is pressurized by the primary coolant circulation pump 6, passes through the discharge port 8, the reactor piping 9, the core support structure 2, and then returns to the reactor core 3 via the reactor circulation path. Forced circulation inside.

In this circulation path, when the primary coolant circulation pump 6 is rotationally driven by a motor (not shown), the pressure loss on the primary side of the intermediate heat exchanger 5 causes the hot pool liquid level 1 to drop.
A liquid level difference is created between the cold pool liquid level 13 and the cold pool liquid level 13 via the stand pipe 14. In FIG. 3, the cold pool liquid level 13 and the pump liquid level 17 are approximately the same liquid level, and a cover gas space 15 is formed above each liquid level.

On the other hand, the heat transferred to the secondary system by the intermediate heat exchanger 5 is transferred to the secondary sodium flowing through the secondary system coolant pipe 18, and this secondary sodium causes the steam generator installed in the secondary system to water and steam in a vessel (not shown).

[0008]

[Problems to be Solved by the Invention] By the way, in a conventional pool type fast breeder reactor, the inside of the hot pool 11 is approximately
The temperature inside the cold pool 12 is, for example, 375°C, and the temperature difference is 15°C.
It's also 5 degrees Celsius. On the other hand, the outer wall of the casing of the primary coolant circulation pump 6 has a temperature of 450 mm due to the radiant heat from the stand pipe 14.
It also becomes ℃. The difference in liquid level height between the cold pool 12 and the hot pool 11 during normal operation is about 2100 mm.

The liquid level in the cold pool 12 (same as the pump liquid level) fluctuates as the pump operating status changes, and due to this liquid level fluctuation, the outer surface of the pump casing receives a thermal load.
The temperature distribution inside the pump casing changes and thermal stress occurs. Therefore, when the liquid level rises rapidly, such as during a nuclear reactor trip, there is almost no strength distribution in the axial direction of the pump casing in the area where the liquid level moves, but the strength distribution in the thickness direction becomes large. There was a problem with thermal stress.

[0010] The present invention was made in consideration of the above circumstances, and its purpose is to make the pump liquid level and the hot pool liquid level the same level, and to prevent any changes during pump rotation changes or reactor trips. The object of the present invention is to provide a sodium pump that can relieve thermal stress on the pump casing even during operation. [Structure of the invention]

[0011]

[Means for Solving the Problems] In order to achieve the above object, the sodium pump according to the present invention includes a lower casing having a suction port and a discharge port, and a lower casing arranged in the lower casing to suck sodium. - An impeller for discharging, an upper casing that is connected to the upper part of the lower casing and encloses sodium whose liquid level is regulated by cover gas, and an upper casing whose upper end is the same as the hot pool liquid level. It is characterized in that it is equipped with an overflow pipe installed at the level and allowing the sodium in the cold pool to overflow.

0012

[Operation] In the present invention having the above structure, the pump casing is cooled by overflowing the sodium in the cold pool through an overflow pipe whose upper end is provided at the same level as the hot pool liquid level. Therefore, even if a rapid liquid level fluctuation occurs in the liquid level movement section in the standpipe during a pump trip, the temperature difference in the pump casing can be reduced.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. FIG. 1 shows one embodiment of the present invention, and the same reference numerals are used to describe the same or corresponding parts as in the conventional structure. Further, the sodium pump of this embodiment is used by being incorporated into the tank-type fast breeder reactor shown in FIG. 2 as a circulation pump.

In FIG. 1, the sodium pump 6a is constructed as follows. In other words, the lower end is the suction port 1.
An overflow pipe 20 is provided inside the upper casing 19 which is closed at 6 . This overflow pipe 2
One end of 0 is provided at a level below the cold pool liquid level 13 during normal operation, and the other end is provided at the same level as the hot pool liquid level 10 (the liquid level when the pump is stopped), and the pump liquid level 17a and the cold pool 12 It communicates with The overflow pipe 20 is supported from the upper casing 19 by overflow pipe supports 21a and 21b.

Further, an eddy current prevention tube 22 is provided in the upper casing 19, and this eddy current prevention tube 22 is connected to a plurality of eddy current prevention tube supports 23a,
23b. The pump shaft 2 is located inside the eddy current prevention pipe 22.
A motor shaft 26 is connected to the upper part of the pump shaft 24 via a coupling 25, and an impeller 27 is attached to the lower part of the pump shaft 24.

A flange portion 28 is formed at the upper end of the upper casing 19, and a shaft sealing device 29 is attached to a portion of the flange portion 28 through which the pump shaft 24 passes. A motor stand 30 is fixed on the flange portion 28, and a motor (not shown) is placed on this motor stand 30, and the pump shaft 24 is rotationally driven by this motor. Further, a lower casing 31 constituting a pump chamber is fixedly connected to the lower end of the upper casing 19 with bolts 32.

Inside the lower casing 31 is a diffuser 33 that swirls and discharges the pump water sucked into the pump chamber from the suction port 16 by the rotation of the impeller 27, and a static pressure sensor fixed with bolts 35 inside the diffuser 33. bearing(
(stationary side) 34 are provided respectively. This hydrostatic bearing 34
is composed of a journal (rotation side) 36 that is integrally machined and provided at the tip of the impeller 27. The lower end of the lower casing 31 serves as a discharge port 8 for pump water sucked in from the suction port 16 .

Pump liquid level 17a in upper casing 19
A cover gas space 15 is located above the cover gas space 15, and above this cover gas space 15 there are a heat shield plate 37 that blocks radiant heat from the pump liquid level 17a, and a biological shield 3 that blocks radiation.
8 are provided respectively. The heat shield plate 37 and the biological shield 38 are connected to the roof slab 4 of the upper part of the reactor vessel 1.
Located within.

[0019] In the figure, reference numeral 11 is a hot pool, and 14 is a hot pool.
39 is a stand pipe (tube) that partitions the hot pool 11 and cold pool 12, 39 is a plurality of pump leak flow holes drilled in the circumferential direction of the suction port 16, and 40 is a plurality of pump leak flow holes bored in the circumferential direction of the diffuser 33. The individual hydrostatic bearing leak flow holes are shown.

[0020] This sodium pump 6a is incorporated and used as a circulation pump in the tank type fast breeder reactor shown in FIG. In FIG. 2, inside a reactor vessel 1, an intermediate heat exchanger 5 supported by a roof slab 4 and a circulation pump 6 are arranged around a core 3 provided in a core support structure 2, A control rod drive mechanism 7 is provided above the roof slab 4, passing through the roof slab 4. A discharge port 8 of the circulation pump 6 is connected to an in-furnace pipe 9 and communicates with the inside of the reactor core 3.

Next, the operation of this embodiment will be explained.

High-temperature sodium heated in the reactor core 3 flows into the hot pool 11, and the primary sodium in the hot pool 11 flows into the intermediate heat exchanger 5 to transfer heat to the primary sodium flowing through the secondary system. The low-temperature primary sodium heat-exchanged in the intermediate heat exchanger 5 is sucked into the suction port 16 of the primary coolant circulation pump 6 via the cold pool 12 . The sodium sucked in through the suction port 16 is pressurized by the circulation pump 6, passes through the discharge port 8, the in-furnace piping 9, the core support structure 2, and is forced to circulate through a circulation path back to the reactor core 3.

In this circulation path, when the circulation pump 6 is rotated by a motor (not shown), a stand pipe 14 is connected between the hot pool liquid level 10 and the cold pool liquid level 13 due to the pressure loss on the primary side of the intermediate heat exchanger 5. A liquid level difference is created through the This cold pool liquid level 13 fluctuates depending on changes in the operating state of the pump.

At this time, in the sodium pump 6a of FIG. 1, sodium enters the pump chamber of the lower casing 31 from the suction port 16 at the bottom of the upper casing 19, is pressurized by the impeller 27, passes through the diffuser 33, and is discharged from the discharge port 8. However, some of it is discharged from the pump leak flow hole 39.
enters the upper casing 19 from the pump free liquid level 17
a, passes through the overflow pipe 20 and returns to the suction port 1.
Return to 6.

On the other hand, the sodium that has entered the gap between the hydrostatic bearing 34 and the journal 36 lubricates the sliding surface of the bearing, and then returns to the suction port 16 via the hydrostatic bearing leak flow hole 40. A cover gas space having a pressure slightly higher than atmospheric pressure is formed above the hot pool liquid level 10, the cold pool liquid level 13, and the pump liquid level 17a.

At this time, the pump shaft 2 may be damaged due to a nuclear reactor trip or the like.
4 stops, the sodium on the primary side of the intermediate heat exchanger 5 stops flowing, so there is no pressure loss, and the liquid level of the cold pool liquid level 13 rapidly increases to the hot pool liquid level 10 and the pump free liquid level 17a, that is, the pump It tries to get as close to the reference liquid level as possible when stopped.

In this manner, in this embodiment, the pump casing is cooled by overflowing the sodium in the cold pool 11 through the overflow pipe 20 whose upper end is provided at the same level as the hot pool liquid level 10. Therefore, during a pump trip, the standpipe 14
Even if rapid liquid level fluctuations occur in the liquid level movement section within the pump casing, the temperature difference in the pump casing can be reduced.

[0028]

[Effects of the Invention] As explained above, according to the present invention,
By installing an overflow pipe in the upper casing and keeping its upper end at the same level as the hot pool liquid level, the inner surface of the casing is cooled by the pump leak flow even when the pump rotation speed is changed or the reactor is tripped. Therefore, a temperature difference applied to the pump casing is less likely to occur, thermal stress is alleviated, and the health of the pump is improved.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of a sodium pump according to the present invention.

FIG. 2 is a longitudinal sectional view schematically showing an example in which a pump is incorporated into a tank-type fast breeder reactor.

FIG. 3 is a longitudinal sectional view showing an example of a conventional sodium pump.

[Explanation of symbols]

3...Reactor core 5...Intermediate heat exchanger 6a...Coolant circulation pump 8...Discharge port 10…Hot pool liquid level 11...Hot pool 13...Cold pool liquid level 14...stand pipe 16...Suction port 19... Upper casing 20...Overflow pipe 27... Impeller 31...Lower casing 33... Diffuser 34...Static pressure bearing 39...Pump leak flow hole 40...Static pressure bearing leak flow hole

Claims (1)

[Claims] Claim 1: A lower casing having a suction port and a discharge port; an impeller disposed within the lower casing for suctioning and discharging sodium; and an impeller disposed in the lower casing for sucking and discharging sodium; What is claimed is: 1. A sodium pump comprising: an upper casing for enclosing regulated sodium; and an overflow pipe within the upper casing, the upper end of which is located at the same level as the liquid level of a hot pool, and overflows sodium from a cold pool.