JPS58211693A - Method of monitoring abnormality of jet pump equipment - 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 method for monitoring abnormalities in jet pump equipment for a boiling water nuclear reactor.

[Technical background of the invention and its problems] A jet pump constitutes a part of equipment that drives the recirculation flow rate of a boiling water nuclear reactor, and plays an important role in controlling the nuclear couplant. The main parts of the jet pump are constructed as shown in FIG. In other words, at the end of the driving water supply pipe lJ'' that penetrates the reactor pressure vessel and rises in the axial direction of the vessel, there are two inlet mixers (the one on the right is shown broken and removed) that hangs downward. ) 2 are attached, and the lower ends of these inlet mixers 2 are fitted and fixed into the upper end openings of the diffuser 3.The inlet mixers 2 are attached to the bracket 4 fixed to the q-up part of the supply pipe 1. It is fixed by a beam 5.This beam is exposed to repeated stress over a long period of time and may crack in some cases.If the beam breaks due to the progression of this crack, the inlet mixer 2
The supporting force against the inlet mixer disappears, and the inlet mixer, shown on the right, is separated from the diffuser 3 and no longer functions as a jet pump.

If an accident like the one in Chapter L occurs, not only will it be impossible to maintain the necessary recirculation flow rate, but the safety of the atomic coupler may also become a problem.

However, in conventional nuclear reactors, there was no monitoring means that could detect the occurrence of beam cracks at an early stage, which could lead to jet pump disassembly as described above.

[Purpose of the invention]

The present invention has been made based on the following two circumstances, and aims to provide a jet pump equipment abnormality monitoring method that can detect cracks in a beam for fixing an inlet mixer in the V stage.
It has been the target.

[Summary of the invention]

In the present invention, the fatigue component of the differential pressure signal between the inlet and outlet of the jet pump is processed, and this is compared with the processed value of the fluctuation component during normal operation.
The above purpose has been achieved by detecting the presence or absence of an abnormality.

Embodiment of the Invention The output of the differential pressure gauge 6 shown in FIG. 1 is input to the determination circuit shown in FIG. Root Mean 5quar
e.

NRM to calculate NRMS=v'λ-fJi-drunken lips)
S calculation unit A calculates the logarithm of the ratio between this calculation result and the standard NRMS, that is, NRMSB, and determines J based on this and the magnitude of the judgment value J obtained by accumulating data during normal operation. , when this judgment result is No, a second judgment part C judges whether a beam crack has occurred or a change in the reactor operating state, depending on whether the phenomenon is observed only in a single jet pump or all jet pumps. have. Note that NAP SD indicates power spectral density.

If cracks occur in the beam of the jet pump and this progresses, it will no longer be possible to obtain sufficient clamping force for the inlet mixer, and the driving fluid will leak from the middle, causing a change in the DC level of the differential pressure signal △P. However, even before this occurs, a change appears in the fluctuation component of the differential pressure signal ΔP. The present invention focuses on this and detects the occurrence of cracks in the beam at an early stage. In other words, Figure 3 shows the power spectrum density of the differential pressure signal when the beam is cracked (solid line a) and that under normal conditions (dashed line b).
), and it can be seen from this that the power spectrum density below IHz increases when cracks occur. Figure 4 is! ■It shows a comparison between the power spectrum density of the differential pressure signal △P under normal conditions (dashed line b) and that when a crack has occurred in the beam of the other jet pump in the pair (solid line C). It can be seen that no significant change in power spectral density is observed in this case.

Therefore, the above monitoring means can detect whether a crack has occurred in the beam of one of the jet pumps or whether an abnormal change in the fluctuation component of the differential pressure signal ΔP is due to a change in operating conditions.

〔Effect of the invention〕

As described above, according to the present invention, the occurrence of cracks in the beam of a jet pump can be detected at an early stage, thereby making it possible to prevent accidents caused by the progress of cracks.

[Brief explanation of the drawing]

FIG. 1 is a front view of the main parts of a jet pump, FIG. 2 is a flowchart of an embodiment of the present invention, and FIGS. 3 and 4 are graphs for explaining the present invention in detail. 2...Inrenotomikiza; 3...Diffuser, 4
... Plackett, 5... Beam 6... Differential pressure gauge application agent Patent attorney Kikuchi Go Department

Claims (1)

[Claims] The NRIVIS below 1 Hz of the fluctuation component of the differential pressure signal between the outlets of the jet pump's diffuser was determined, and it was obtained by calculating the logarithm of the ratio between this and the NRMS B during normal operation, and by accumulating data during normal operation. A jet pump equipment abnormality 1 observation method, characterized in that the presence or absence of a crack in a beam that fixes an inlet mixer of a jet pump is detected by comparing the logarithm with a determination threshold and determining the magnitude of the logarithm and the determination threshold.