JPH0531730B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for estimating the mass of metal loose parts mixed into a primary nuclear reactor system.

[Technical background of the invention and its problems]

For example, objects left behind in the reactor during reactor construction or nuclear fuel exchange, or damaged objects due to falling off or deteriorating plant equipment parts may enter the reactor primary system. Such foreign objects that are mixed into the primary reactor system and float around are usually called loose parts. Such loose parts tend to accumulate particularly at the bottom of the reactor pressure vessel and the bottom of the steam generator, which adversely affects the plant. That is, possible adverse effects of loose parts on the plant include damage to fuel rods due to blockage of channel boxes, increase in radioactive crud in the primary reactor system, inability to drive control rods, and damage to steam generators. Furthermore, it is predicted that serious problems will arise in terms of continued plant operation and safety.

In order to remove loose parts that cause problems in plants, it is first necessary to detect where the loose parts are located in containers or piping of plant equipment, etc. The detection method is to detect the impact sound generated by impact with the inner walls of containers and piping of plant equipment, etc., and to locate the impact position of the loose part based on this impact sound. It has already been proposed. For example, a time difference direct display method that directly uses data on the arrival time difference of shock waves to multiple impact sound testers, or a control point display method that locates as the intersection of two hyperbolas with a constant time difference, etc. has been proposed. Until now, no technology has been disclosed for estimating the mass of . Therefore, if the mass of loose parts can be estimated and evaluated, it is possible to improve the safety of the plant and improve its operating rate based on this. There was a desire to develop a technology for estimating

[Purpose of the invention]

The present invention was made in view of the above circumstances, and
The purpose of the present invention is to provide a method for estimating the mass of metal loose parts that is capable of estimating the mass of metal loose parts mixed into containers such as plant equipment, piping, and steam generators.

[Summary of the invention]

In order to achieve the above object, the present invention uses a sensor to detect the impact sound generated by the collision of metal loose parts mixed into the primary reactor system, and uses a sensor to detect the frequency or period of the wavefront portion of the detected impact signal. The mass of the metal loose parts is estimated by comparing the frequency or period of the wave crest of this shock signal with the corresponding known correlation data or diagram of the frequency or period of the wave crest and the mass. It is something.

Next, a method for estimating the mass of metal loose parts according to the present invention will be described.

A metal object simulated as a metal loose part was placed in a container also simulating a nuclear reactor pressure vessel, and this simulated metal object was caused to impact against the inner wall of the container, and the impact signal generated at that time was detected by a sensor such as an accelerometer. It is then amplified using an amplifier. The frequency (hereinafter referred to as wave crest frequency) and the period of the wave crest portion (hereinafter referred to as wave crest period) of the wave crest portion (about the first wave or second wave) of this amplified shock signal are recorded. Next, the wave crest frequency and wave crest period of the same impact signals as above are recorded for simulated metal bodies of various masses, and these are summarized to form the wave crest frequency vs. mass correlation diagram in Figure 1 and the wave crest frequency vs. mass correlation diagram in Figure 2. Figure obtained. As can be seen from these correlation diagrams, when the mass of the simulated metal body is large, the wavefront frequency is high;
The wave crest frequency becomes lower as the mass becomes smaller, and the wave crest period becomes shorter as the mass of the simulated metal body becomes larger, and the wave crest period becomes longer as the mass of the simulated metal body becomes smaller. Experimental results also revealed that changes in the wavefront frequency and wavefront period due to the mass of the simulated metal body are reproducible and are closely related to the mass of the metal loose parts.

Based on the above-mentioned knowledge, after a sensor detects the impact signal generated when a loose metal part collides with the inner wall of a plant equipment container or piping, the wave crest frequency or wave crest period of this impact signal is determined in advance. The mass of the metal loose part is estimated using correlation data or a correlation diagram between the known wave crest frequency or wave crest period and mass.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to the drawings.

FIG. 3 shows a block diagram for carrying out the method of estimating the mass of metal loose parts of the present invention. For example, the detector 1 detects an impact signal generated when a metal loose part collides with the inner wall of a container or pipe of plant equipment (not shown). This detected shock signal is input to an amplifier 2, where it is amplified to a predetermined size and then sent to a frequency analyzer 3 at the next stage.
is input. In the frequency analyzer 3, the waveform of the wavefront portion of the shock signal is extracted, and the wavefront frequency or wavefront period is determined by the microcomputer 4 at the next stage. The obtained wavefront frequency or wavefront period is then compared with known correlation data or a correlation diagram between the wavefront frequency or wavefront period and the mass stored in the memory of the microcomputer 4. The comparison result is displayed by the output device 5. In this way, the mass of the metal loose parts can be determined.

FIG. 4 shows another block configuration diagram for carrying out the method for estimating the mass of metal loose parts of the present invention, and the same parts as in FIG. 3 are given the same reference numerals for explanation. A detector 1 detects an impact signal generated when a metal loose part collides with, for example, an inner wall of a container or pipe of plant equipment (not shown). The detected impact signal is input to the amplifier 2, amplified to a predetermined magnitude, and then input to the digital waveform recording device 6 at the next stage. In this digital waveform recording device 6, the input shock signal is digitized, and then its wavefront frequency or wavefront period is digitally calculated and compared with the known wavefront frequency or wavefront period stored in the next stage computer 4. A comparison is made between the mass correlation data. By displaying the results of this comparison on the output device 5, the mass of the metal loose parts can be known.

〔Effect of the invention〕

According to the present invention, it is possible to estimate and evaluate the mass of metal loose parts mixed into containers or pipes of plant equipment, etc., so it is possible to improve the safety of the plant and its operating rate.

[Brief explanation of drawings]

FIGS. 1 and 2 are wave crest frequency vs. mass correlation diagrams and wave crest period vs. mass correlation diagrams, respectively, according to the present invention, and FIGS. 3 and 4 are diagrams showing the method for estimating mass of metallic loose parts of the present invention. FIG. 1...Detector, 2...Amplifier, 3...Frequency analyzer,
4...Microcomputer, 5...Output device, 6...
Digital waveform recording device.

Claims (1)

[Claims] 1. A sensor detects an impact signal generated by a collision of a metal loose part present in a container, piping, or steam generator of plant equipment, etc., and determines the frequency or period of the wave crest of the detected impact signal, The mass of the metal loose part is estimated by comparing the frequency or period of this wave crest with corresponding known correlation data or correlation diagram of the frequency or period of the wave crest and mass. A method for estimating the mass of metal loose parts.