JPS6330787A - Jet pump-cavitation detector for boiling water type reactor - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a device for detecting cavitation occurring in a jet pump of a boiling water nuclear reactor.

(Prior Art) Figure 2 shows a schematic configuration of a boiling water nuclear power plant, and 1 in the figure is a reactor pressure vessel. The coolant 2 in the reactor pressure vessel 1 flows into the reactor core 4 from a lower blemish 3 provided below the reactor core 4, and flows within the reactor core 4 from below to above. At that time, the temperature is raised by the heat of nuclear reaction in the reactor core 4, and it flows out from the reactor core 4 as a two-phase flow of water and steam. The coolant 2 that has passed through the core 4 is separated into water and steam by a steam separator 5, and the separated steam is removed from the moisture in the steam by a steam dryer 6.
3 and a steam isolation valve 8 to a turbine 9, and the turbine 9 generates electricity via a generator 10.

In addition, the steam that has performed the work of the turbine is condensed in a condenser 11, and then supplied into the reactor pressure vessel 1 via a water supply pipe 13 by a water supply pump 12 from a water supply sparger 14 provided above the reactor core 4. be done. This water supply sparger 1
The feed water supplied into the reactor pressure vessel 1 from 4 is mixed with the reactor water separated by the steam water separator 5, and
and the reactor core 4. A part of the reactor water that has flowed down to the downcomer section 15 flows into the recirculation pump 17 from the recirculation pipe 16 connected to the reactor pressure vessel 1, and after being pressurized by the recirculation pump 17, the water is transferred to the downcomer section. The fluid is supplied as a driving fluid to the nozzle portion 18a of the jet pump 18 installed in the jet pump 15. Further, the remaining part is sucked into the jet pump 18 by the driving fluid from the recirculation pump 17, and is ejected together with the driving fluid into the lower blennium 3 and flows into the reactor core 4.

By the way, in such a boiling water reactor, the steam separator 5
The reactor water separated in the reactor pressure vessel 1 has a temperature close to the saturation temperature of the steam generated in the reactor pressure vessel 1, that is, the subcool (difference between the temperature of the reactor water and the saturation temperature of the steam) is small. When reactor water with a small amount of water is sucked into the jet pump 18, cavitation is likely to occur. However, as described above, the reactor water separated by the steam separator 5 is mixed with the water supplied from the water supply sparger 14, so by the time it reaches the nozzle portion 18a of the jet pump 18, the temperature becomes relatively low, and the jet Since the water head pressure from the water surface of the coolant 2 acts on the nozzle portion 18a of the pump 18, cavitation does not occur in the jet pump 18 under normal conditions, but if, for example, the water supply from the water supply sparger 14 is stopped. In such a case, cavitation occurs in the jet pump 18.

Figures 3 to 7 show the state of the reactor when the water supply from the water supply sparger 14 is stopped.As shown in Figure 3, when the water supply flow rate a rapidly decreases to zero, water flows into the core 4. As the temperature of the coolant 2 increases, the void fraction within the core 4 increases, and the neutron flux gradually decreases. and,
As the void fraction increases, the water level d in the reactor decreases as shown in FIG. 4, a scram signal is generated, and control rods are rapidly inserted into the reactor core 4. When the control rods are rapidly inserted into the reactor core 4, the neutron flux rapidly decreases, the void fraction in the reactor core 4 decreases, and the pressure loss of the coolant 2 passing through the reactor core 2 decreases. The flow 1ic increases little by little, but eventually decreases because the recirculation pump 17 is tripped as the water level in the reactor falls.

Further, at this time, the reactor pressure e decreases with the reactor water level d, but increases rapidly because the main steam isolation valve 8 is closed following the rapid insertion of the control rods.

Under such circumstances, the required suction head f of the jet pump 18 gradually decreases almost simultaneously with the scram, as shown in FIG. At about the same time, it decreased significantly. Therefore, the margin suction head obtained by subtracting the necessary suction head f from the effective suction head Q is approximately 8
After a second, the value becomes negative, and cavitation occurs until the recirculation pump 17 is tripped.

As described above, when cavitation occurs in the jet pump 18, the discharge flow rate of the jet pump 18 decreases, so as shown in FIG. The core inlet flow aCt transiently decreases significantly compared to the core inlet flow aCt, and the cooling ability for the fuel temporarily decreases. Therefore, as shown in Fig. 7, the minimum critical fuel power ratio (△MCPR) shows a positive value as shown by the solid line 11 when cavitation does not occur, but when cavitation occurs, it shows a positive value. As with rAi2, it sometimes showed a negative value, and there was a risk that the integrity of the fuel would be impaired.

(Problems to be Solved by the Invention) As described above, when cavitation occurs in the jet pump 18, the integrity of the fuel may be impaired, and the jet pump 18 may be damaged due to vibration or the like. However, as described above, cavitation often occurs temporarily, and it has been extremely difficult to reliably detect this and prevent cavitation from occurring.

The present invention was made based on these circumstances, and
The purpose of this is to detect cavitation that occurs in jet pumps in advance, and to prevent cavitation from occurring in boiling water reactors.
An object of the present invention is to provide a cavitation detection device.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a reactor pressure detector for detecting the pressure within the reactor pressure vessel, and a reactor pressure detector connected to the reactor pressure vessel. a main steam flow rate detector for detecting steam flow flowing through the main steam pipe, a feed water flow rate detector for detecting the flow rate of water supplied to the reactor pressure vessel, and a water supply flow rate detector for detecting the flow rate of water supplied to the reactor pressure vessel; a jet pump discharge flow rate detector that detects a jet pump discharge stream installed in the downcomer section between the reactor pressure vessel and the reactor core, and each of these detections. a downcomer section enthalpy calculation circuit that calculates the enthalpy of reactor water in the downcomer section based on a detection signal from the downcomer section; a jet pump inlet pressure detector that detects the inlet pressure of the jet pump; and a detection signal from the pressure detector. a jet pump saturation enthalpy calculation circuit that calculates the saturation enthalpy of reactor water in the jet pump based on a signal; an output signal from the jet pump saturation enthalpy calculation circuit; and an output signal from the downcomer enthalpy calculation circuit; The present invention is characterized by comprising a cavitation detection circuit that compares the values and outputs a cavitation occurrence warning signal when the difference between the two exceeds a preset value.

(Function) In the present invention, the enthalpy of reactor water in the downcomer section is compared with the saturation enthalpy of reactor water in the jet pump, and when the difference between the two exceeds a preset value, a cavitation occurrence warning signal is output. As a result, cavitation occurring in jet pumps can be detected in advance.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows a schematic configuration of a boiling water nuclear power plant equipped with a jet pump cavitation detection device according to the present invention. Detector, 20 is main steam pipe 7
This is a main steam flow rate detector that detects the main steam flow rate Ws flowing through the main steam flow rate Ws. Further, in the figure, 21 and 22 are a water supply flow rate detector and a water supply temperature detector that detect the water supply flow rate WFw and the water supply temperature T flowing through the water supply pipe 13, and 23 is a water supply water temperature detector that detects the water supply flow rate IWjet of the jet pump 18. This is a jet pump discharge flow rate detector. Each of these detectors 19°20.
Reactor pressure detection signal 1 output from 21.22.23
9S, main steam flow rate detection signal 208° feed water flow rate detection signal 2
1S, the feed water temperature detection signal 22S, and the jet pump discharge flow rate detection signal 23 are each input to the downcomer section enthalpy calculation circuit 25, and the following calculation processing is performed in the downcomer section enthalpy calculation circuit 25.

That is, the downcomer section enthalpy calculation circuit 25 calculates the feed water enthalpy hFw based on the feed water temperature detection signal 228 from the feed water temperature detector 22, and also calculates the feed water enthalpy hFw based on the jet pump discharge flow rate detection signal 23S from the jet pump discharge flow m detector 23. Based on this, the core inlet flow II W c is calculated. Furthermore, from the reactor pressure detection signal 198 from the reactor pressure detector 19, the saturation enthalpy hf(
Po), and from these calculation results downcomer section 1
The enthalpy hDOWN of reactor water No. 5 is calculated from the following formula and outputted as a downcomer enthalpy detection signal 258.

The downcomer part enthalpy detection signal 258 output from the downcomer part enthalpy calculation circuit 25 is input to the cavitation detection circuit 27, and the jet pump part saturation enthalpy detection signal 26S from the jet pump part saturation enthalpy calculation circuit 26 is input to the cavitation detection circuit 27. compared to Here, the jet pump part saturation enthalpy calculation circuit 26 calculates the amount of reactor water in the jet pump 18 based on the inlet pressure detection signal 248 from the jet pump inlet pressure detector 24 provided near the nozzle part 18a of the jet pump 18. The saturation enthalpy hjeL is calculated, and this saturation enthalpy hjet is supplied to the cavitation detection circuit 27 as a jet pump section saturation enthalpy detection signal 268. Therefore, in the cavitation detection circuit 27, the downcomer enthalpy calculation circuit 2
The downcomer part enthalpy detection signal 258 from 5 and the jet pump part saturation enthalpy detection signal 26S from the jet pump part saturation enthalpy calculation circuit 26 are compared,
The difference between the two (Δh=hDOWN hjeO is 58tu/
Knee it bitation occurrence warning signal 27S when lb or more
1 is output to the recording/displaying device 28. In addition, △h is 15B
When tu/1b or more, cavitation generation signal 27S
2 is output to the recording/displaying device 28.

In this way, in this embodiment, the enthalpy hDowN of the reactor water in the downcomer section 15 and the saturation enthalpy hjat of the reactor water in the jet pump 18 are determined, and when the difference between the two exceeds a preset value, the cavitation occurrence warning signal 27S1 is generated. Jet pump 18
It is possible to detect cavitation that occurs in advance. Therefore, by controlling the rotation speed of the recirculation pump 17, for example, cavitation can be prevented from occurring.

[Effects of the Invention] As described above, according to the present invention, cavitation occurring in a jet pump can be detected in advance, so cavitation can be prevented from occurring, and the reliability of the jet pump can be significantly improved. Can be done.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a boiling water nuclear power plant equipped with a jet pump cavitation detection device according to the present invention, Figs. 2 to 7 are diagrams for explaining conventional examples; A schematic configuration diagram of a water-type nuclear power plant, Figure 3 shows the water supply flow layer when water supply from the water supply sparger is stopped. Diagram showing temporal changes in neutron flux and core inlet flow rate,
Figure 4 is a diagram showing temporal changes in reactor water level and reactor pressure when the water supply is stopped, Figure 5 is a diagram showing temporal changes in various suction heads of jet pumps during scram, Figure 6 is a diagram showing the temporal change in the core inlet flow when cavitation occurs and does not occur in the jet pump during scram, and Figure 7 shows the time change in the core inlet flow when cavitation occurs and does not occur in the jet pump. FIG. 3 is a diagram showing temporal changes in the minimum fuel output ratio. DESCRIPTION OF SYMBOLS 1...Reactor pressure vessel, 4...Reactor core, 5...Steam water separator, 6...Steam dryer, 7...Main steam pipe, 13
... Water supply pipe, 14 ... Water supply sparger, 15 ...
Downcomer section, 17...Recirculation pump, 18...Jet pump, one...Reactor pressure detector, 20...
・Main steam flow rate detector, 21... Water supply flow rate detector, 22
... Feed water temperature detector, 23... Jet pump discharge flow rate detector, 24... Jet pump inlet pressure detector, 25... Downcomer section enthalpy calculation circuit, 26.
・・Jet pump part saturation enthalpy calculation circuit, 27・
... Cavitation detection circuit, 28... Recording indicator. Applicant's agent Patent attorney Takehiko Suzue Figure 3 Time (ro・) Time (sho) KuΣ(, IcLcr-

Claims (1)

[Claims] A reactor pressure detector that detects the pressure within the reactor pressure vessel, a main steam flow rate detector that detects the main steam flow rate flowing through a main steam pipe connected to the reactor pressure vessel, and the reactor pressure vessel. a feed water flow rate detector that detects the flow rate of feed water supplied into the reactor pressure vessel; a feed water temperature detector that detects the temperature of the feed water supplied into the reactor pressure vessel; and a downcomer portion between the reactor pressure vessel and the reactor core. a jet pump discharge flow rate detector for detecting the discharge flow rate of a jet pump installed in the jet pump; a downcomer section enthalpy calculation circuit for calculating the enthalpy of reactor water in the downcomer section based on detection signals from each of these detectors; a jet pump inlet pressure detector that detects the inlet pressure of the jet pump; a jet pump section saturation enthalpy calculation circuit that calculates the saturation enthalpy of reactor water in the jet pump based on a detection signal from the pressure detector; a cavitation detection circuit that compares the output signal from the jet pump section saturation enthalpy calculation circuit with the output signal from the downcomer section enthalpy calculation circuit and outputs a cavitation occurrence warning signal when the difference between the two exceeds a preset value; A jet pump for a boiling water reactor characterized by having the following features:
Cavitation detection device.