JPS6120894A - Nuclear reactor - 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 provides an axial flow pump blade that is disposed in an annular gap formed between a reactor pressure vessel and a reactor core shroud, and that the axial flow pump blade is driven by a drive unit. The present invention relates to a nuclear reactor that circulates coolant within the reactor pressure vessel by driving the reactor.

[Technical Background of the Invention] Conventionally, the following two types of systems have been adopted for circulating coolant in a reactor pressure vessel in a nuclear reactor.

On the one hand, as shown in FIG. 4, a plurality of (for example, 10) closed loop recirculation systems are formed outside the reactor pressure vessel a,
This recirculation system is equipped with a large external recirculation pump C, which converts the coolant flowing out from the lower part of the reactor pressure vessel a into a high water head by the external recirculation pump C, and transfers the coolant to the reactor core. The air is supplied to a plurality of jet pumps e arranged around the shroud d.

The other type, as shown in Fig. 5, has a plurality (for example, 10) of internal recirculation pumps f installed vertically below the reactor pressure vessel a, with a shaft located outside the core shroud d. Coolant is sent to the lower part of the core by driving a flow pump 8 (not shown).

[Problems with the Background Art] However, since the nuclear reactor shown in Figure 4 has an external recirculation system, in the event that the recirculation system is ruptured, the coolant will be transferred to the reactor containment vessel. (not shown).

On the other hand, the reactor shown in FIG. 5 has the disadvantage that when the internal recirculation pump f is stopped, the natural circulation flow rate of the coolant is lower than in the reactor shown in FIG. Also,
The structure is such that a large number of holes are drilled in the lower part of the reactor pressure vessel a, and the axial flow pump, that is, the internal recirculation pump f, is accessed through these holes, which makes the work complicated. Providing a large number of holes in the bottom of a reactor pressure vessel for mounting an axial pump is undesirable from both an economic and safety standpoint. Furthermore, the large number of internal recirculation pumps f increases costs.

Furthermore, in the reactors shown in FIGS. 4 and 5, the coolant flowing into the core shroud d once passes through a fairly narrow diameter portion, so the loss due to fluid resistance is quite large, and the occurrence of flowing water vibration is also considered.

[Objective of the Invention 1 The present invention has been made in view of the above points, and the first object is to provide a cooling water circulation system that has no external loop and minimizes the number of holes for installing pumps near the bottom of the reactor pressure vessel. The objective is to provide a nuclear reactor with a system. The second object is to provide a single reactor having a cooling water circulation system that allows for a sufficiently large natural circulation flow rate when the pump is stopped and that is less likely to cause unstable flow during operation. A third object is to provide a nuclear reactor in which a high head axial flow pump can be easily incorporated into the reactor pressure vessel. A fourth object is to provide a nuclear reactor that can prevent crud accumulation in the coolant pool, which occurs when a circulation system is incorporated into the reactor pressure vessel.

[Summary of the Invention] The present invention provides at least one axial flow pump and an integer number (11 jet pumps) of the axial flow pump arranged in the annular gap formed between the reactor pressure vessel J and the core shikoroud, The reactor is characterized in that the discharge flow of the axial pump is used as the driving flow of the jet pump to circulate the coolant in the reactor pressure vessel. This is a null pump (axial flow pump) with the role of a conventional external pump, and for this reason, the equivalent of external piping is placed in the annular gap between the reactor core shroud and the reactor pressure vessel. .

Furthermore, since this pump is used for supplying driving water, it is necessary to use a pump with a high water head, so it is a multi-stage pump with a long shaft length. For this reason, the shaft of the pump impeller is supported at the upper and lower parts of the pump casing arranged around the core circumference, and the shaft of the drive motor is connected from the lower part.

Furthermore, in order to prevent the accumulation of crud in the water stagnant at the bottom of the annular part around the reactor core, which is divided by partition plates, a thin nozzle is connected to the jet pump throw section 1~ from the bottom of the annular part, making it possible to circulate the water existing at the bottom. I have to.

[Embodiment 1 of the invention Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

Note that explanations of the same parts as in the conventional example (FIGS. 4 and 5) will be omitted.

1 to 3 show nuclear reactors according to embodiments of the present invention.
JL) Therefore, a core shroud 21 is installed in the reactor pressure vessel 1 surrounding the reactor core 2, and this core shroud 21 is installed inside the reactor pressure vessel 1.
A steam separator 22 and an evaporative dryer 2 are installed in the loud 21 Th.
3 is installed.

In the annular gap 24 formed between the reactor pressure vessel 1 and the reactor core 2, two internal pumps (axial flow pumps) 19, eight jet pumps 20, and an internal pump 19 are installed. Eight driving water pipes 12 are arranged to supply discharge flow to jet pump nozzles 13. The annular gap 24 is separated from the core lower plenum 25 by a partition plate 17 near its bottom, and only the discharge port 11 of the jet pump 20 is open to the core lower plenum 25.

Further, a stagnant water circulation ruzzle 18 is connected to the jet pump throat 16 from the bottom of the annular gap 24 .

The internal pump 19 has three stages with a long shaft length, and the pump shaft 5 holding the impeller 4 has an upper bearing 7 and a lower bearing 8 supported by a bearing support part 6 at the lower part of the internal pump casing 3.
r: ″Supported.

Shaft 9 of drive motor 10 of internal pump 19
is connected to the pump shaft 5 at the lower part of the partition plate 17.

The jet pump 20 includes a jet pump suction pipe 14 and a jet pump nozzle 13 arranged in the throw 1 part 16 of the jet pump suction pipe 14.
The driving water is supplied from the discharge hole 1 of the internal pump 19.
1 , the driving water is supplied from the driving water flow manhole 15 to the jet pump nozzle 13 through the driving water piping 12 .

In the reactor configured as described above, high-pressure water discharged from the two internal pumps is supplied to the nozzles 13 of each of the four jet pumps 20 through the driving water piping 12, and this driving water is supplied to the jet pumps. The water in the suction pipe 14 is accelerated and enters the reactor core 2 from the discharge hole 11 of the jet pump 20 through the lower plenum 25. In the reactor core 2, a part of the water boils and becomes steam, which is transferred from the reactor pressure vessel to main steam. The water flows through the pipe 26 and is supplied to the turbine system, and the remaining water becomes saturated water, mixes with the water supplied from the water supply pipe 27, and returns to the suction side of the internal pump 19.

The internal pump 19 needs to have a multi-seven-stage impeller 4 in order to increase the discharge pressure, but since the bonnet 1 and foot 5 are longer than conventional ones, it is housed in a long pump casing 3, and the pump shaft 5 is It is supported by bearings 7.8 located at the top or bottom.

Since it is difficult to integrate such a long pump 19 with the drive motor 1°, the pump body is separated from the drive motor 10 and assembled and supported outside the jet pump 20, drive water piping 12, and pressure vessel 1. After integration using a structure, reactor pressure vessel 1 or reactor core Sikoroud 2
It is preferable to fixedly support it at 1. At this time, the pumpshades 71 to 5 pierce the bottom of the partition plate 17 through the seal portion and project into the lower blenheim portion 25. -h, the drive motor 10 is installed at the bottom of the reactor pressure vessel 1, but the motor 11 and the foot 9 are connected to the pump shaft 5 from below during assembly.
be combined with 1. Water stagnates at the bottom of the annular gap 24 between the reactor pressure vessel 1 and the reactor core 2, which is separated from the lower blenheim 25 by the partition plate 17, and crud accumulates. In order to promote stagnant water circulation, a stagnant water circulation nozzle 18 is connected to the bottom of the annular gap 24 and the throat part 16 of the jet pump 20, and through this narrow nozzle 13 the stagnant water circulation nozzle 18 is constantly connected to the annular gap 24.
The water at the bottom of the tank mixes with the mainstream.

According to the nuclear reactor of this embodiment, the following effects can be obtained.

In other words, according to the reactor of the example, at least one multistage large axial flow pump is disposed in the annular gap between the core shroud 8 and the reactor pressure vessel 1, so the flow path area is that of a jet pump type. (Fig. 4) or an internal pump type (Fig. 5), it can be more than 10 times larger. Therefore, the required flow rate can be circulated at low rotational speed and low flow rate. Therefore, the viscous resistance between the inner wall of the reactor pressure vessel, the axial flow pump, and the cylinder on the required side, and the I! i! Since the frictional resistance is also small, the pump power is reduced and sufficient natural circulation flow rate can be ensured in case a pump stoppage accident occurs.1 [Effects of the Invention] As explained above, the present invention At least one
A base axial flow pump and a jet pump of an integral multiple of this axial flow pump are arranged, and the discharge flow of this axial flow pump is used as the driving flow of the above-mentioned Gen] pump to circulate the coolant in the reactor pressure vessel. It is a furnace.

According to the present invention, since a large number of jet pumps are arranged,
Even when the internal pump is stopped, the natural circulation flow rate is sufficient and stable operation is possible, resulting in the following effects.

First, a safe nuclear reactor is obtained since there is no external loop and no holes are required in the lower part of the reactor pressure vessel.

Second, the natural circulation flow ψ when the pump is stopped can be increased.

Thirdly, the pump power is small, and therefore the number of driving pumps can be reduced.

Fourth, since the internal pump and jet pump are integrated and assembled, installation work becomes easier.

Fifth, accumulation of crud can be prevented.

Note that the present invention is not limited to the above-mentioned embodiments, but includes the following modifications and applications.

(1) The number of inter-small pumps and jet pumps can be varied. (2) The cross-sectional shape of the driving water piping and the piping route can be changed in various ways. (3) Piping can be installed on the suction side of the internal pump to draw water from below. (4) The height of the jet pump can be increased to change the position and number of drive nozzles. (5
) It is possible to combine the pump shaft and motor shaft in various ways. (6) A special type of internal pump can be used.

[Brief explanation of the drawing]

1 to 3 are schematic configuration diagrams of one embodiment of the nuclear reactor according to the present invention, FIG. 1 is a cross-sectional view of the reactor along line A-A in FIG. Figure B-)3 is a schematic cross-sectional view taken in the perspective direction, Figure 3 is a schematic cross-sectional view taken in the B-B arrow direction of Figure 1, and Figures 4 and 5 are schematic configuration diagrams of a conventional nuclear reactor. It is. 1... Reactor pressure vessel, 2... Reactor core, 3... Internal pump casing, 4... Impeller,
5...Pump shaft, 6...Bearing support part, 7...Upper bearing, 8...Lower bearing, 9...7-tashaft, 10...Internal pump drive motor, 11...・Discharge hole, 12・
... Drive water piping, 13... Jet pump nozzle, 14... Jet pump suction pipe, 15... Drive water flow hole, 16... Jet pump throat, 17... Partition plate, 18... - Stagnant water circulation nozzle, 19... Internal pump, 20... Jet pump, 21... Core shroud, 22... Steam water separator, 23... Steam dryer,
24... Annular gap portion, 25... Core lower blennium, 26... Main steam pipe, 27... Water intake pipe. Application agent Patent attorney Kikuchi 5 Category 1 Figure 2 Figure 3

Claims (4)

[Claims] (1) At least one axial pump and a jet pump whose number is an integral multiple of the axial pump are disposed in the annular gap formed between the reactor pressure vessel and the core shroud, and the discharge flow of the axial pump is A nuclear reactor, characterized in that the reactor is configured to circulate coolant within the reactor pressure vessel as a driving flow for a jet pump. (2) Axial flow pump blades are arranged around the shroud at equal intervals in the circumferential direction of the shroud, and these axial flow pump blades are arranged concentrically with the core shroud and fixedly supported within the annular gap. 2. The nuclear reactor according to claim 1, further comprising a drive section provided on a side outer wall of said reactor pressure vessel. (3) The shaft of the axial flow pump is supported via bearings at the upper and lower parts of the pump casing, the pump casing is fixed in the annular gap independently of the pump drive motor, and the pump drive motor shaft is connected to the pump shaft. A nuclear reactor according to claim 1, characterized in that the reactor is connected to a nuclear reactor. (4) The nuclear reactor according to claim 1, further comprising a nozzle between the bottom of the annular gap and the jet pump throat.