JPH04127090A - Built-in type recirculation pump - Google Patents

Abstract

PURPOSE:To ensure constant revolution of a pump even when a power source is lost by mounting a plurality of rotary blades on a rotating shaft to be housed into a motor case, which is provided with an outflow port of a fluid to drive and rotate the rotary blades. CONSTITUTION:A plurality of rotary blades 22 are mounted on a hollow tube 21 on an outer circumference of a rotating shaft within a motor case 8 mounted on an outer circumference of a lower mirror 4 of a reactor pressure vessel. The rotating shaft acts as impeller shaft 9 thereabove and as a motor shaft 10 at a motor section. As the tube 21 is connected to the rotating shaft with a key, with the rotation of the rotary blades 22, an impeller 5 rotates through the rotating shaft. An inflow port 23 and an outflow port 24 of a fluid for rotating the rotary blades 22 are formed in the case 8 and an introduction pipe 25 is connected to the inflow port 23 to introduce a reactor water in the reactor pressure vessel while a discharge pipe 26 is connected to the outflow port 24 to be linked to a low pressure section. An injection valve 27 and a discharge valve 28 set at the introduction pipe 25 and a leader pipe 26 are controlled to open simultaneously when revolution of a pump falls below a fixed value as caused by the losing of a power source.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a built-in recirculation pump for a nuclear reactor, and particularly to a recirculation pump that does not suddenly stop even in the event of a loss of external power. Concerning self-contained recirculation pumps.

(Prior Art) As shown in FIG. 3, when a built-in recirculation pump 1 is installed inside the reactor to circulate core cooling water in a boiling water reactor, it is usually placed outside the shroud 2. Eight to twelve units are attached to the lower mirror 4 of the reactor pressure vessel 3 and feed cooling water to the lower part of the reactor core 5. Such a built-in recirculation pump 1 has a structure as shown in FIG.
is provided on a baffle plate in the downcomer 6 in the furnace. The motor 7 is a submerged type and is housed in a motor case 8 attached to the outer periphery of the pressure vessel lower mirror 4. The motor 7 is connected to the impeller 5 by a rotating shaft, which is an impeller shaft 9 at the upper part and a motor shaft 10 at the lower part. Transmits power to impeller 5. Cooling water in the reactor descending through the downcomer 6 is pressurized by the impeller 5 and sent to the lower part of the reactor core 5, so that it rises and enters the reactor core 5 to cool the fuel. The motor is connected to an external power source through a cable.

The impeller of this self-contained recirculation pump goes inside the furnace, so
The motor is also made compact to avoid external interference, and there is a limit to increasing the diameter of both the impeller and motor. Therefore, the inertia of this pump is small.

Therefore, if the power to this motor is lost for some reason during the operation of the nuclear reactor, for example, if the external power is lost due to a lightning strike, the rotation speed will be reduced to 1200 rpm s as shown in Figure 5.
Pump inertia 19.5) A pump with cgrrl' has a flow rate of 10
As shown in the graph showing the change in pump speed (%) against the elapsed time (seconds) after the loss of external power when the work was 0%, the pump rotation speed suddenly decreased and the pump speed decreased accordingly. As shown in Figure 6, which shows the change in the core flow rate (%) with respect to the elapsed time (seconds) after the loss of external power, the cooling water to the core decreases, and a thermal load is temporarily applied to the fuel (for a few seconds).

In order to prevent this, the power supply of the current built-in recirculation pump is equipped with an M-G set 11 as shown in Figure 7, so that even if the external power supply is lost, the M-G set 11
The inertia of the built-in recirculation pump 1 secures the power supply and prevents sudden loss of power.

(Problem to be Solved by the Invention) By the way, this M-G set 11 is a mechanical combination of a motor 101 and a generator 102 via a fluid coupling, and the fluid coupling is connected to an input shaft and rotates. The impeller and the launch connected to the output shaft face each other and are immersed in oil, and the rotation speed of the generator 102 is controlled by adjusting the amount of oil. The output of the generator 102 is supplied to the built-in recirculation pump 1 via a transformer 103, a rectifier 104, an inverter 105, etc., and the built-in recirculation pump 1 is rotated at a rotation speed proportional to the output. It has become. In addition, in FIG. 7, the reference numeral 106 is a disconnector,
107 is a circuit breaker, 108 is a cable, 109 is a main transformer, 110 is a main generator, and 111 is a station transformer.

As described above, the M-G set 11 is large, has a complicated electrical system, and takes up a large space in the reactor building.
This poses a large cost burden.

The present invention has been made to address these points, and eliminates the above-mentioned drawbacks and uses a large M-type as a power source for a built-in recirculation pump.
To provide a built-in recirculation pump that can maintain the rotational speed of the pump above a certain level even if power is lost without disposing a G set.

[Structure of the Invention] (Means for Solving the Problems) The built-in recirculation pump of the present invention has a plurality of rotary blades mounted in a motor case on a rotary shaft that connects an impeller and a motor and transmits rotational force to the impeller. The motor case is provided with an inlet and an outlet for the fluid that drives the rotor to rotate.

(Function) In the built-in recirculation pump of the present invention, when the power is lost, a valve or the like is installed so that the fluid flowing from the high pressure section to the low pressure section is introduced from the inlet provided in the motor case and flows from the outlet to the low pressure section. By operating the impeller, the rotor blades attached to the rotary shaft can be rotated, and this rotational force can prevent the impeller from stalling and ensure a rotation speed above a predetermined value.

(Example) Hereinafter, one example of the present invention will be described based on the drawings. Note that the same parts as in the conventional example are given the same reference numerals, and the explanation thereof will be omitted.

FIG. 1 shows a self-contained recirculation pump according to one embodiment of the present invention. Further, FIG. 2 shows a cross section taken along line A-A in FIG. 1. In this embodiment, several rotary members g22 are attached to a hollow tube 21 on the outer periphery of a rotating shaft in a motor case 8 attached to the outer periphery of the lower mirror 4 of the reactor pressure vessel. The rotating shaft is the impeller shaft 9 at the top and the motor shaft 10 at the remoter part, and the hollow tube 21 is connected to the rotating shaft with a key.
When the rotary blade 22 rotates, the impeller 5 also rotates via the rotating shaft. Inflow port 2 for fluid that rotates the rotor blade 22
3 and an outflow port 24 are formed in the motor case 8. An inlet pipe 25 for introducing reactor water in the reactor pressure vessel 3 as a fluid, for example, is connected to the inflow port 23.
A discharge pipe 26 leading to the low pressure section is connected to the drain pipe 26. An injection valve 27 and a discharge valve 28 are installed in the introduction pipe 25 and the discharge pipe 26, respectively, and when the pump rotation speed drops below a certain value due to power loss, this is detected and the injection valve 27 and discharge valve 28 are activated. Control them to open at the same time. Note that when reactor water is used as the fluid to rotate the rotor blades 22 in this way, the reactor water enters the motor section for several seconds until the power is restored, so a furnace is installed in the middle of the inlet pipe 25 to prevent the temperature of the motor 7 from rising. Two water storage containers must be installed to constantly store and cool reactor water. Furthermore, as a precaution, a heat shielding wall 30 is provided between the rotor blade 22 in the motor case and the stator 7 a % rotor 7 b of the motor 7 to protect the insulation of the motor 7 even when hot water enters. .

With the above configuration, in this embodiment, if the pump rotational speed drops below a certain value due to power loss, this will be detected and the injection valve 27 provided on the introduction pipe 25 will Discharge pipe 2 in another direction of motor case 8
The discharge valve 28 above 6 opens at the same time. The exhaust line is connected to a low pressure area, such as a condensing chamber (not shown), so that reactor water rapidly flows into the motor case 8 and impinges on the rotor blades 22. Since the hollow tube 21 to which the rotor blade 22 is attached is connected to the rotary shaft with a key, the impeller 5 rotates due to the collision of this reactor water.

As is clear from the above explanation, in the built-in recirculation pump according to this embodiment, even in the event of power loss, reactor water is vigorously injected into the rotor blades inside the pump, so that more than a certain number of pumps are required. It is possible to obtain the rotational speed and prevent fuel overload of the reactor core.

[Effects of the Invention] As explained above, according to the present invention, even if the motor power is lost, the minimum necessary rotation speed of the pump can be ensured without requiring large equipment. I can do it,
It is possible to prevent fuel overload in the reactor core. Therefore, the built-in recirculation pump of the present invention greatly contributes to improving the safety and reducing costs of nuclear power plants.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the built-in recirculation pump of the present invention, FIG. 2 is a sectional view taken along line A-A in FIG. 1,
Figure 3 is a cross-sectional view of a boiling water reactor with a conventional built-in recirculation pump, Figure 4 is a cross-sectional view of a conventional built-in recirculation pump, and Figures 5 and 6 are each a cross-sectional view of a conventional boiling water reactor with a built-in recirculation pump. FIG. 7 is a graph showing temporal changes in pump speed and core flow rate at the time of loss. FIG. 7 is a power supply system diagram of a conventional built-in recirculation pump having an MG set. 4... Reactor pressure vessel lower mirror, 5... Impeller, 7...
...Motor, 8...Motor case, 9...Impeller shaft, 10...Motor shaft, 21...Porrow tube, 22...Rotor blade, 23...Inflow port, 2
4... Outlet, 25... Inlet pipe, 26... Discharge pipe, 27... Injection valve, 28... Discharge valve, 29
...Reactor water storage container, 3o...Heat shield wall

Claims (1)

[Claims] A motor case attached to the outside of the reactor pressure vessel lower mirror, a motor housed within this motor case,
In the built-in recirculation pump, the built-in recirculation pump includes an impeller that is arranged in a reactor pressure vessel and rotates to send cooling water to the reactor core, and a rotating shaft that connects the impeller and the motor and transmits rotational force to the impeller. A built-in recirculation pump characterized in that a plurality of rotary blades housed in the motor case are attached to the rotary shaft, and the motor case is provided with an inlet and an outlet for a fluid that rotationally drives the rotor blades. .