JPS628095A - Monitor device for loose part - 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] <Industrial Application Field> The present invention relates to a device for monitoring fallen parts using detected noise, and in particular can effectively monitor fallen parts in a fluid circulation system of a nuclear reactor. Regarding monitoring equipment.

<Conventional technology and its problems> When parts fall off in the reactor circulation system, such as the reactor or the steam generation section connected to it, the loose parts can damage various equipment or damage the internal fluid. Problems arise such as the flow of water being obstructed. Nuclear technology requires greater safety than other technical fields, and the occurrence of loose parts must be minimized, and when loose parts occur, the fact and location of the occurrence must be accurately and promptly identified. need to be detected. For this reason, devices and systems for monitoring loose parts have been developed and provided.

FIG. 3 shows a conventional loose parts monitoring system. In the figure, vibrations detected by a sensor (for example, an accelerometer) 1 are converted into electrical signals and sent to a digital loose parts detector 2 . This loose parts detector 2 determines whether or not the received signal exceeds a preset specified value, and if the value exceeds the specified value, it is set to HIGH to indicate that loose parts have occurred.
Generates an H alarm signal (voltage pulse). This H.I.G.
H alarm signal is digital loose parts locator 3
It is determined whether the signal is appropriate, and if it is determined to be appropriate, the mask alarm 4 issues an alarm.

FIG. 5 is a diagram showing the arrangement of sensors in a pressurized wooden nuclear reactor (PWR) (this diagram will also be used in the embodiments of the present invention described later). In the figure, 20 is a reactor pressure vessel, 21 is a pressurizer, 22 is a circulation pump, and 23 is a steam generator. In the illustrated apparatus, there are four steam generation circulation systems (four loops). Among these loops (
Taking the loop for the steam generator 23A as an example, the sensor arrangement is normally as follows. Note that the other loops are also arranged in a similar manner. Two of them are attached to the upper part of the reactor pressure vessel 20, and two of them are attached to the in-core guide tube 24 of the lower part. In the steam generator 23A, one is attached near the hanging fitting 25, one is attached to the water supply pipe 26, and other parts are attached to the drain pipe, blowdown pipe, etc. Also, one piece is attached to the circulation pump 22. Note that the circles in the figure indicate the locations where the sensors are placed, and . indicates a sensor for constant monitoring, and O indicates a sensor for monitoring during abnormal conditions. Of these, the constant monitoring sensor is placed in the primary coolant circulation system, which is the most dangerous part of the plant, and where loose parts are most likely to accumulate.

Next, a method for determining whether a signal is correct or incorrect in the loose parts monitoring device will be explained. In the nuclear reactor shown in Figure 5, the difference in the placement distance of each sensor is at least 2.5 m or more,
- The distance between both ends of the secondary cooling system is more than 250 m. Here, if the sound velocity of materials such as piping is 5000 m/sec, three or more HIs occur within 0.5 milliseconds (msec).
If a GH alarm is detected, or if the interval between two alarms is 50m5ec or more, it is determined to be a false alarm. This judgment pattern will be explained using FIG. The basis of this judgment is to select three channels in order from the earliest among the sensors that detected the HIGH alarm, and perform estimation by triangulation based on the time difference between impact waveform generation between each channel. In other words, the impact generation position can be estimated from the relationship between the time difference between the impact waveform generation and the propagation speed of the rope.For example, judgment pattern 1.2.3 in Figure 2 indicates that there is only one impact; If an impact takes more than 5011 seconds after the first impact, or three or more impacts occur in succession within 0.5 n+sec, etc., it is judged as unlikely based on the flow velocity of the internal fluid, the distance between each sensor, etc. On the other hand, judgment pattern 4.5.6 has an impact of 0.5 m5e.
2 within c, the second impact is 0.5 tssec to 50 tasec from the first impact, similarly the third impact is 9.5 tasec from the first impact.
m5ec~5Q m5ec is a pattern that can occur depending on the flow rate of the internal fluid, the distance between each sensor, etc. In this case, the detection result is determined to be correct.

However, in the above method, the alarm occurrence pattern is only analyzed temporally and numerically, so the recognition of the alarm occurrence pattern in the system becomes rough.
Even patterns that cannot actually occur cannot be determined to be false alarms, leading to frequent false alarms.

In particular, when a plant is started or stopped, the pressure, temperature, etc. in the system change rapidly, generating various background noises, and since this noise changes compared to during steady operation, false alarms are more likely to occur. There will be more.

<Object of the present invention> The present invention is constructed to solve the above-mentioned problems,
The purpose of the present invention is to provide a device that can prevent false alarms from occurring and accurately detect abnormalities within the system.

<Summary of the present invention> In short, the present invention analyzes the impact sound detected by each sensor by comparing it with the delay time and transmission pattern between each channel, which are stored in advance, to accurately determine whether the alarm is correct or incorrect. It is a device configured to make a judgment.

<Example> Examples of the present invention will be specifically described below.

In FIG. 1, the signal detected by a first sensor 1 is sent to a loose parts detector 2. In FIG.

On the other hand, the signals detected by the other sensors 6 are similarly sent to the loose parts detector 8. Similarly, the signal of the nth sensor 7 is also sent to the nth loose parts detector 9. The pattern of HIGH alarm signals generated by these loose parts detectors is checked for validity by a false alarm reduction device 5 disposed inside the locator 3, and if it is valid, a mask alarm 4 issues an alarm.

At this time, the false alarm reduction device (circuit) 5 performs the following functions to check the validity.

(1) The sensor that first generated the HIGH alarm, and
Check the signal transmission pattern (signal transmission combination) with the sensor that occurred the second time.

(2) The sensor that first generated the HIGH alarm, and
The delay time between the sensor and the second sensor is checked.

In all of these tests, the signal transmission pattern and delay time in each channel when an alarm occurs is checked in advance, this data is memorized, and the actually measured signal transmission pattern and delay time are compared with this stored data. Check the validity.

FIG. 4 shows an example of the relationship between signal transmission patterns and delay times. This figure shows the pattern and delay time in a pressurized water reactor. In the figure, the numbers surrounded by circles indicate each sensor; for example, Φ indicates the first sensor, and ■ indicates the second sensor. Here, the first sensor is attached to the in-core guide tube 24 in FIG. 5, the second sensor is attached to another adjacent in-core guide tube, the third sensor is attached to the upper part of the pressure vessel 20, and the fourth The sensor of pressure vessel 20
A fifth sensor is located in the blowdown pipe of the steam generator 23, and a sixth sensor is located in the steam generator drain pipe in the upper part of the steam generator 23 adjacent to the third sensor. Also, the sensors connected by arrows are
The sensors are capable of transmitting signals to each other, and the number next to the arrow indicates the maximum delay time (n+
5ec).

An example of alarm determination will be shown using this diagram.

If the first HIGH alarm occurs in the first sensor, the next HIGH alarm generation pattern should be one of the following.

(1) Maximum delay time of the second sensor is 0.7m5ec
A HIGH alarm occurs within

(2) Maximum delay time of the third sensor is 3.7+m5e
HIG) I alarm occurs within c.

(3) Maximum delay time of the fourth sensor is 3.3n+se
HIGH alarm occurs within c.

If it does not match any of the patterns (1) to (3) above, it is a false alarm, and only other matching patterns are judged to be loose parts alarms.

In addition, when we simulated the performance of a conventional device and the device according to the present invention using a certain plant as an example, the device of the present invention determined that about 80% of the loose parts alarms of the conventional device at the time of plant startup were false alarms. And this judgment turned out to be correct. Therefore, according to the present invention, the subsequent alarm analysis time can be significantly reduced.

Effects> Since the present invention has the above-described configuration, it is possible to accurately determine the presence or absence of loose parts not only during steady plant operation, but also at times when false alarms are particularly likely to occur, such as when starting up or stopping the plant. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a signal transmission system diagram of a loose parts monitoring device showing an embodiment of the present invention, FIG. 2 is a diagram showing a pattern of determining whether a signal is correct or incorrect in a conventional device, and FIG. 3 is a signal transmission system diagram of a conventional device.
FIG. 4 is a diagram showing the signal transmission pattern of each sensor and the maximum delay time of signal transmission, and FIG. 5 is a perspective view of the pressurized wooden nuclear reactor showing the arrangement of the sensors. 1.6.7...Sensor

Claims (2)

[Claims] (1) In a device in which multiple acoustic sensors are arranged in the internal fluid circulation system and the presence or absence of loose parts is determined based on the signals from each acoustic sensor, the circuit that processes the signal from each sensor is An alarm reduction circuit is installed, and this false alarm reduction circuit compares the stored data with the actually measured data with a circuit that stores data on the signal transmission pattern and signal transmission delay time from each sensor in advance. A loose parts monitoring device characterized by comprising a circuit for determining whether it is correct or incorrect. (2) The loose parts monitoring device according to claim (1), wherein the device having an internal fluid circulation system is a pressurized water nuclear reactor.