JP2862876B2 - Loose parts monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a loose parts monitoring device that monitors a dropped part by detecting a vibration sound generated from a dropped part (loose part) in a fluid flow path. In particular, the present invention relates to a loose parts monitoring device having a low false alarm rate.

[Conventional technology]

If equipment parts fall off in various circulatory systems consisting of pipes through which the steam and liquid of the reactor flow, such as the reactor and the steam generator connected to the reactor, these fallout parts (loose parts)
This causes problems such as damage to various devices and obstruction of the flow of the internal fluid. Nuclear technology requires more safety than other technical fields, so it is necessary to reduce the generation of loose parts as much as possible. It is necessary to accurately detect the location of occurrence and the moving state of the loose parts. For this reason, various countermeasures have been conventionally considered, and the applicant of the present invention has also filed Japanese Patent Application Nos. 57-178567, 57-212687, 58-119834, and 60-1959.
No. 11 and Japanese Patent Application No. 62-171853 have been filed.

In a conventional loose part monitoring device of a nuclear power plant, a value of an impact waveform of a loose part detected by a detector (for example, an accelerometer) attached to each device of a primary cooling system such as a nuclear reactor or a steam generator. However, compared to the normal noise that occurs in each device (for example, pump and motor operating noise, fluid flow noise, etc., these are referred to as background noise), a high alarm alarm is issued if the noise level exceeds a certain ratio. I want to emit. In addition, the loose parts monitoring device incorporates a device called a locator that determines the correctness of the detection signal of the detector attached to each device,
This locator has a function of judging the correctness of a signal from each detector. As a criterion for such judgment,
(A) If the number of times of receiving the high alarm warning within 50 milliseconds (mm sec) is one, it is regarded as an erroneous signal. The reason is that the speed of sound in steel is 3m / msec, and it travels 150m in 50msec. The distance between detectors attached to each device is about 20 m at the maximum, and if loose parts are generated, many signals should be generated from nearby detectors in a short time. (B) If three or more alarm signals are received within 0.5 millisecond, it is regarded as a false signal. Due to the placement of the detectors, it is highly unlikely that more than two alarms will be received within 0.5 ms, which will result in electrical noise between the cables connecting each detector to the control panel. This is because there is a high possibility that the pulse signal is induced and emitted. In the above cases (a) and (b), the signal adjuster and the detector are reset, and at the same time, the centralized alarm and the locator are also reset to cancel the data.

In other cases, it was determined that the alarm was an appropriate loose parts alarm, an alarm was issued by a centralized alarm device, an automatic start of a tape recorder for recording, generation of an external alarm, recording by a printer, and the like were performed. At the same time as this recording, all components of the apparatus except for the external alarm and the tape recorder that are activated are to be reset.

Then, every time an external alarm is issued, the operator goes to the monitoring device, temporarily stops the external alarm, and checks the audio monitor for an abnormal sound at the site. Further, various operations such as stopping the tape recorder and recording the launching time of the printer and the result of listening to the audio monitor on a recording sheet have been performed.

[Problems to be solved by the invention]

However, with conventional monitoring devices, thermal expansion (a squeaking sound occurs when the metal wall of each pipe expands due to thermal expansion) due to pressure changes and temperature changes that occur at the start-up of a nuclear power plant, etc. Causes frequent false alarms. Each time this alarm was issued, the operator had to repeat the various operations described above, making the operation complicated, and in addition, the operator was forced to use a printer or record data using a tape recorder.

According to actual measurement data, one plant startup (several days)
Reported that about 2000 or more false alarms occurred in such a case, and in such a case, it was difficult to perform the above-described operations, and it was almost impossible to analyze.

For this reason, in actual operation, it has been common to exclude the warning of the loose parts at the time of startup and return the system to online after the startup is completed.

That is, the conventional system has a fatal disadvantage that it cannot be used at the time of starting and stopping.

[Means for solving the problem]

The problem of the prior art described above is that, in a monitoring device for loose parts generated in a fluid flow path, a plurality of detectors attached to equipment constituting the fluid flow path and detecting collision by loose parts, An abnormal sound sensing unit that senses the signal of, a true / false determining unit that receives the signal sensed by the abnormal sound sensing unit, determines whether the signal is correct by the number of receptions within a predetermined time, and transmits a positive signal to the energy upper / lower limit analyzing unit The energy (Li) of the signal received from the true / false judgment unit is obtained by combining the detector with the detector that receives the signal from the true / false judgment unit and detects the signal.
Is larger than the energy (Lmin) that can be detected by the sensor farthest from the impact point in the detected sensor group, and smaller than the energy (Lmax) that can be detected by the sensor closest to the impact point in the undetected sensor group ( Lmin <Li <Lmax), a signal within this range is adopted, and an energy upper / lower limit analysis unit that eliminates a signal outside this range as a false signal is provided. Is done.

〔Example〕

First, the configuration of the present invention will be described below with reference to FIGS.

A plurality of detectors (1 to 10, for example, accelerometers) attached to each device constituting the fluid flow path of the nuclear reactor, and a signal conditioner which amplifies signals from the detectors and keeps the amplitude constant. (It is called loose parts detector in 11-20)
And false alarm evaluation to evaluate and record whether it is due to signal background noise or actual loose parts,
It comprises a recording unit (21, FER (false alarm evaluation and recording unit)) and a data recorder (25) for recording only a signal determined to be a loose part.

The false alarm evaluation / recording unit (21) includes an abnormal sound detecting unit 22 for detecting a signal from the signal condition unit (11 to 20).
A true / false judgment unit (23) for judging the correctness of the signal detected by the abnormal sound detecting unit based on the number of receptions within a predetermined time; and the magnitude of the energy of the signal cleared by the true / false judgment unit; It comprises an energy upper / lower limit analysis unit 24 for removing erroneous signals from the combination.

Next, the contents of the present invention will be described in detail below. In FIG. 2, loose parts detectors (signal conditioners) 11 to 20
Then, if there is a sudden impact sound compared to the normal background noise (background noise), the vibration sound sensed by the primary system piping of the nuclear power plant or the accelerometers 1 to 10 installed in the auxiliary equipment, An alarm is issued. Normally, background noise and loose part vibration sound are compared, and an alarm is issued if the ratio is equal to or higher than a certain ratio. In addition, FER (false alarm valuation and recording unit) 21
As a result, the validity check as to whether or not loose parts are generated is performed as follows.

As shown in FIG. 1, the abnormal noise detector 22 detects that abnormal noise is generated in the FER 21 based on an alarm signal from the loose part detectors 11 to 20. Further, it is necessary to diagnose whether the abnormal noise is a loose part. Therefore, this is first performed by the right / wrong judgment unit 23. This function is erroneous when (a) the number of alarms is one within 50 milliseconds and (b) three or more alarms are received within 0.5 milliseconds in the same manner as in the prior art. Consider as an alarm.

The correctness of the signal is judged by the energy upper / lower limit analysis unit 24 for the signal cleared by the judgment unit.

The method of energy upper and lower limit analysis will be described below. Primary equipment such as nuclear reactors and heat exchangers are equipped with detectors (sensors) such as accelerometers at required positions. When loose parts are generated, the sensor at the shortest distance first detects the signal. , (Called channel 1),
Next, a sensor (referred to as a second channel) disposed at the second closest distance emits a detection signal.

Now, the energy level (energy intensity) at the impact point when the loose part collides with the pipe wall of the flow path
Assuming that Li is a detection energy level detected by a sensor provided at a distance D from the impact point, L _A satisfies the following equation (1).

L _A = LiD ^-2 (1) where α is a constant according to equation (1), and the detection / non-detection of the impact by the loose parts in each sensor attached to each part of the flow path is L _A / Ls ( Threshold). Here, the threshold value Ls, related to a threshold that it is background noise L _b, not the loose parts of Ls = KL _b.

Now, let Li and D be constant threshold values in each sensor.
Is as shown in FIG. here, Is a set (group) of sensors that detected loose parts, Is a set of loose parts for which no loose parts were detected. It can be understood from FIG. 4 that the energy level at the impact point due to the loose parts is larger than the energy Lmin that can be detected by the sensor 2 farthest from the impact point in the detected sensor group, and the energy level at the impact point in the undetected sensor group. That is, it is smaller than the energy Lmax that can be detected by the closest sensor 3. That is, the relationship of Lmin <Li <Lmax (2) is established, and the upper and lower limits of the energy at the impact point can be estimated.

As described above, when the relationship of equation (2) is established, the relationship as shown in FIG. 4 occurs. However, when the relationship is not due to loose parts, the characteristics are different from the propagation of sound waves due to metal impact. The relationship in FIG. 4 does not hold.

For example, as shown in FIG. 5, when the relationship between Lmax and Lmin in the sensors of the detected group and the undetected group is reversed, it is not appropriate to consider the impact of loose parts.

As described above, only when it is determined that the part is a true loose part, an HI alarm (high alarm) is issued.
A signal is recorded by the channel data recorder 25.

According to this judgment unit, it has been confirmed in the actual equipment test in a certain reactor apparatus that the conventional technology could reduce 267 false alarms to 18 false alarms, that is, 93% reduction, and 7% that could not be removed was accidental. E = D ^-2 (see FIG. 3) indicates that an impact has occurred in the pattern riding on the pattern.

〔The invention's effect〕

By practicing the present invention, it is possible to judge a false alarm based on background noise at the time of starting a nuclear reactor or the like, and to monitor loose parts even at the time of starting / stopping which could not be monitored conventionally. .

[Brief description of the drawings]

FIG. 1 is an embodiment of the present invention, FIG. 2 is an overall view of a conventional loose parts monitoring device, FIG. 3 is a diagram showing a relationship between a distance from an impact point and detected energy, and FIG. FIG. 5 is a diagram showing a detection situation of each sensor due to a cause other than loose parts. 1-10: Detector, 11-20: Loose parts detector,
21: False alarm evaluation recording unit, 22: Abnormal noise detector, 23
...... Correction judgment part, 24 ... Energy upper / lower limit analysis part, 25 ...
Data recorder.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G21C 17/04 G01H 17/00

Claims (1)

(57) [Claims] 1. A device for monitoring loose parts generated in a fluid flow path, comprising: a plurality of detectors attached to equipment constituting the liquid flow path and detecting collision by loose parts;
An abnormal sound sensing unit for sensing a signal from the detector, and an error detecting unit for determining whether the signal detected by the abnormal sound sensing unit is correct or not based on the number of receptions within a predetermined time and transmitting a positive signal to the energy upper / lower limit analyzing unit. The combination of the determination unit, the magnitude of the signal energy received from the true / false determination unit and the detector detecting the signal, and the energy (Li) of the signal received from the true / false determination unit is included in the detection sensor group. Energy (Lmin) that can be detected by the sensor farthest from the impact point
Considering that the energy is larger than the energy (Lmax) that can be detected by the sensor closest to the impact point among the undetected sensor groups (Lmin <Li <Lmax), a signal within this range is adopted, A loose parts monitoring device comprising: an energy upper / lower limit analysis unit that eliminates external signals as erroneous signals.