RU2197759C2 - Method and device for measuring pressure of graphite contact ring onto zirconium tube in reactor process channel - Google Patents

Abstract

FIELD: controlling parameters of reactor units. SUBSTANCE: method primarily designed for type RBMK reactors involves use of ultrasonic vibration receiver for recording acoustic signal produced due to ultrasonic action of acoustic transmitter onto acoustic system incorporating water-filled zirconium tube damped by graphite rings. Acoustic system is adjusted to working conditions with low Q-factor and high sensitivity to damping action of graphite rings. Scale showing amplitude of reflected ultrasonic radiation as function of graphite contact ring pressure onto zirconium tube is calibrated by means of auxiliary graphite ring fitted onto tube. Zirconium tube damped by graphite rings is scanned by acoustic transmitter and ultrasonic vibration receiver. Amplitude and phase of acoustic signals arriving from graphite rings are recorded. Graphite ring pressure onto tube is determined according to calibration scale obtained earlier. Device implementing proposed method has acoustic transmitter and ultrasonic vibration receiver, acoustic-transmitter oscillator, and detector signal converting module. It also has bushing incorporating acoustic transmitter and ultrasonic vibration receiver which are disposed in diametrically opposite ends of single line placed in tube when scanning location point of graphite ring. Linear displacement transducer records bushing position in zirconium tube. EFFECT: enhanced safety, reliability, economic efficiency, and operating precision of reactor unit. 4 cl, 3 dwg

Description

 The invention relates to the regulation of the parameters of reactor plants (RU) and, in particular, can be used to determine the pressure force of the contact graphite ring on a zirconium pipe in the process channel (TK) of the RBMK reactor (high-power channel reactor) at nuclear power plants (NPPs).

 A known ultrasonic method taken as a prototype for determining the pressure force of a graphite ring on a zirconium pipe (Scientific research work (R&D) P / R P-6476 dated 12/30/1988), which is based on the registration of a Lamb wave with a resonance in the frequency range f = 250 kHz - 500 kHz. In this case, an acoustic system consisting of a zirconium tube filled with water and damped by graphite rings is subjected to ultrasonic treatment. The pressure force of the graphite ring on the pipe wall is adjusted to 46 kg. Due to the absorption of the Lamb wave, only the contact of the graphite ring of the pipe wall is recorded. The received data is processed on a personal computer (PC).

The disadvantages of this method of determining the pressure force of a graphite ring on a zirconium pipe in the technological channel of the reactor are:
1. Reducing the safety and reliability of switchgear due to insufficient control of the contact between the inner surface of the graphite ring and the outer wall of the zirconium pipe in the technological channel of the reactor due to the ability to register only the contact of the graphite ring of the pipe wall with a ring pressure of 46 kg

 2. Reducing the accuracy and efficiency of reactor operation due to the low accuracy of measuring the pressure force of a graphite ring on a zirconium pipe, which does not allow the diagnosis and prediction of the state of technological channels as a result of many years of operation of the reactor.

The same R&D describes a device for determining the pressure force of a graphite ring on a zirconium pipe in the technological channel of the reactor, which is closest to the proposed one. This device contains an emitter and a receiver of ultrasonic vibrations, which are in the same sector of the zirconium tube opposite the cut in the graphite ring, are located at an angle and have a gap with respect to the inner wall of the pipe. The emitter operates under the action of a generator that is manually controlled in the frequency range f = 200 kHz - 500 kHz, and the receiver is connected to an input amplifier, which, in turn, is connected by its output to an analog-to-digital converter (ADC) running under PC control . The disadvantages of this device for determining the pressure force of a graphite ring on a zirconium pipe are
1. reduced accuracy and efficiency of the device due to manual control of the generator;
2. reduced accuracy of the device due to the lack of preliminary processing of the receiver signal;
3. reduced reliability and safety of the switchgear due to the complexity of the design of the device for determining the pressure force of a graphite ring on a zirconium pipe due to the need for strict requirements for the location of the emitter and receiver to the “cuts” in the graphite rings;
4. reduced accuracy of the device due to the lack of noise immunity;
5. reduced accuracy of the device due to the lack of a mechanism responsible for the location of the sensors in the pipe.

 The proposed inventions solve the problem of improving the safety and reliability of reactor operation, as well as extending the working life during monitoring, diagnostics and predicting the condition of technological channels as a result of many years of operation of the reactor under intense neutron irradiation and elevated temperature.

 To obtain such a technical result, in the proposed method for determining the pressure force of a contact graphite ring on a zirconium tube, an acoustic signal is recorded by the ultrasonic vibrations receiver from the ultrasonic action of the emitter on an acoustic system consisting of a zirconium tube filled with water and damped by contact graphite rings.

Distinctive features of the proposed method are that the acoustic system sets the operating mode with low quality factor and high sensitivity to damping by graphite rings, calibrates the scale of the dependence of the amplitude of the reflected ultrasonic radiation on the pressure force of the graphite ring on the zirconium tube using an additional graphite ring worn on the pipe is scanned by the emitter and receiver of ultrasonic vibrations of the zirconium pipe damped by graphite to rings, record the magnitude of the amplitude and phase of the acoustic signals coming from the graphite rings, and determine the pressure force of the graphite ring on the pipe in accordance with the previously obtained calibration scale. In addition, a distinctive feature is that to establish an operating mode with a low quality factor in the speaker system, the frequency of the ultrasonic signal of the emitter f = 51.2 kHz ± 0.1 kHz, or f = 58.1 kHz ± 0.1 kHz, or f = 65.63 kHz ± 0.1 kHz, or f = 77.87 kHz ± 0.1 kHz, or f = 89.85 kHz ± 0.1 kHz and an amplitude in the range of 5 V, in this case, the receiver signal is out of phase with respect to the emitter signal and with a delay in the range from 0 to 45 ^o , which allows you to set it in the speaker system forced standing wave mode with amplitude in the range 0-0.5 V.

 As a result of the practical application of the proposed method, the safety and reliability are increased, as well as the economy and accuracy of the switchgear due to the possibility of determining not only the contact, but also directly the pressure force of the contact graphite ring on the zirconium pipe, which in turn will allow for monitoring, diagnostics and prediction of the condition technological channels of RU. Moreover, as laboratory studies have shown, it is advisable to use the parameters of ultrasonic signals provided in the proposed method.

 To obtain the named technical result, we propose a device that, like the one closest to it, known for work (R&D R-6476), includes an emitter and a receiver of ultrasonic vibrations, a frequency generator for emitter operation, and a receiver signal conversion module containing analog PC-to-digital converter.

 Distinctive features of the proposed device are that it additionally contains a module including a sleeve containing an emitter and a receiver of ultrasonic vibrations, which are located diametrically opposite on one line, placed in a zirconium tube when scanning the location of the graphite ring, a linear displacement sensor that fixes the position of the sleeve in the pipe, and the signal conversion module of the receiver of the device further comprises an amplifier, an active half-wave rectifier of the media values and an active low-pass filter, while the frequency generator for the emitter is controlled by a PC. In addition, a feature is that the device uses a crystal oscillator with a frequency resolution of 32 Hz. As a result of the practical application of the proposed device, the safety and reliability, as well as the efficiency of the reactor installation, are improved by increasing the accuracy of the device for determining the pressure force of a contact graphite ring on a zirconium pipe in the RBMK reactor channel due to preliminary processing of the signal from the ultrasonic vibrations receiver and the presence of device noise immunity the presence of a mechanism responsible for the location of the emitter and receiver of ultrasonic frigged in the pipe, the presence of a computer control a generator of ultrasonic vibrations as well as by simplifying the structure of the device due to the lack of strict requirements for the location of the transmitter and receiver to the cuts in the graphite rings. In addition, as laboratory studies have shown, the quartz frequency generator used provides high accuracy and stability when setting the operating mode in frequency and amplitude.

 The claimed group of inventions meets the requirement of unity of invention, since it forms a single inventive concept, moreover, one of the declared objects of the group - "A device for determining the pressure force of a contact graphite ring on a zirconium pipe in the reactor channel" is intended to implement another claimed object of the group - "Method for determining the force pressure of the contact graphite ring on the zirconium pipe in the reactor’s process channel, "while both objects of the group of inventions channeling to solve the same problem to obtain a single technical result.

 The invention is illustrated by drawings, which depict: in FIG. 1 - a fragment of the acoustic system, consisting of a zirconium tube filled with water and damped by a graphite ring with an air gap between them, formed by a paper strip 0.2 mm thick with a waveform of the acoustic signal; figure 2 is a fragment of the acoustic system, consisting of a zirconium tube damped by a graphite ring with an oscillogram of the acoustic signal; figure 3 is a structural diagram of a device implementing the proposed method.

The proposed method is carried out in the following sequence: first, a specially designed sleeve is placed in the zirconium tube of the reactor TC, in which the emitter and receiver of the ultrasonic signal are located, the operating mode is set in the speaker system to provide a wide uniform frequency characteristic of the radiation and reception, allowing the electric signal to be reproduced without distortion in emitter and acoustic signal on the electrical side in the receiver, which becomes sensitive to external impacts. To do this, use the frequency of the ultrasonic signal f = 51.2 kHz ± 0.1 kHz, or f = 58.1 kHz ± 0.1 kHz, or f = 65.63 kHz ± 0.1 kHz, or f = 77.87 kHz ± 0.1 kHz, or f = 89.85 kHz ± 0.1 kHz and the amplitude in the range of 5 V, while achieving the receipt of the receiver signal antiphase relative to the signal of the emitter and with a delay of 0 to 45 ^o and set the acoustic mode of the forced standing wave with an amplitude of up to 0.5 V, which gives a low quality factor and high sensitivity to damping graphite rings. If necessary, to establish the required mode in the acoustic system, the frequency of the ultrasonic signal with a resolution of 32 Hz is changed. When the operating mode is established, the sleeve with the emitter and receiver should be outside the zone of the graphite rings in the speaker system. Next, they proceed to the calibration mode, which is necessary to establish the sensitivity of the device and establish the range of registration of pressure forces. For this, a separate contact graphite ring with a metal clamp is put on the zirconium tube, a sleeve with an emitter and a receiver of ultrasonic vibrations is brought in and installed in such a way that the center of the receiver is opposite the middle of the graphite ring. The metal clamp is pulled together with a force of 5 kg according to the "force meter" and the gain control of the receiver sets the minimum level of a constant signal in the range of 50 - 100 mV. The value of this signal, corresponding to a pressure force of 5 kg, is recorded in the PC memory. After removing the force from the metal clamp, a constant voltage corresponding to zero pressure is entered into the PC memory. In the PC memory, it is necessary to enter intermediate values for pressures of 1 kg, 2 kg, etc., creating a scale of pressure forces up to 5 kg. Next, the calibration ring is removed or left, passing to the mode of direct measurement of the pressure force of contact graphite rings on a zirconium tube depending on the amplitude and phase of the acoustic signal. Using an electric drive, moving the sleeve with the emitter and receiver at a speed of 1-2 cm / s, they scan the location of the contact graphite rings along the height of the zirconium tube, recording the processed acoustic signal in the PC memory, which is proportional to the distribution of ring pressure forces in accordance with the calibration scale . In this case, the pressure distribution diagram of the rings with the location (height) of the sleeve with sensors is displayed on the monitor screen. Scanning can be carried out in two passes through the pipe TC from top to bottom and back.

 To implement the method, a device has been developed that runs under the control of a PC, using the specially developed Test program. exe., which consists of three routines: Rejim. exe, to establish the operating mode in the speaker system, Kalibr. exe, to establish the calibration scale and Registr. exe, for direct registration of the pressure force of contact graphite rings on a zirconium tube when scanning by the emitter and receiver.

Example 1. Figure 1 shows a fragment of an acoustic system consisting of a zirconium tube filled with water and damped by a graphite ring with an air gap between them formed by a paper strip 0.2 mm thick, for which an oscillogram of the amplitude change of the ultrasonic signal when scanning this ring with sensors is shown:
1 - graphite ring,
2 - zirconium pipe,
3 - emitter of an ultrasonic signal,
4 - receiver of an ultrasonic signal,
5 - ultrasonic signal at the location of the graphite ring,
6 - direction of movement of the sensors.

 The oscillogram shows that when scanning the location of the graphite ring due to the absorption and reflection of part of the ultrasonic signal, the amplitude of the ultrasonic signal decreases. In the established mode, the amplitude value of the processed acoustic signal of the receiver takes the value Uout = 350 mV, which corresponds to the pressure force of the graphite ring on the pipe F = 4.3 kg.

Example 2. Figure 2 presents a fragment of an acoustic system with a tight-fitting graphite ring to a zirconium pipe:
1 - graphite ring,
2 - zirconium pipe,
3 - emitter of an ultrasonic signal,
4 - receiver of an ultrasonic signal,
5 - ultrasonic signal at the location of the graphite ring,
6 - direction of movement of the sensors.

 The oscillogram shows how, as a result of increased damping, the effects of absorption and reflection are so pronounced that at the interface of the acoustic media, the ultrasonic signal changes the amplitude and phase, passing twice through zero, and the polarization effect is more pronounced. The change in the amplitude of the ultrasonic wave in the middle of the ring is proportional to the pressure force of the ring. In the established mode, the amplitude Uout = 350 mV of the acoustic signal of the receiver corresponds to a pressure force of F = 2 kg, and for Uout = 100 mV, the pressure force is F = 4.15 kg.

 The proposed method was laboratory tested on a water filled zirconium pipe 1.5 m long, on which 8 graphite rings with different pressure values were installed. Pressure adjustment was provided by individual metal clamps.

 A device for determining the pressure force of a split contact graphite ring on a zirconium tube (Fig. 3) includes an ultrasonic oscillator (1), an ultrasonic oscillator emitter (2), a receiver ultrasonic signal amplifier (3), an active medium-voltage rectifier (4), active low-pass filter (LF) (5), system acoustic signal receiver sensor (6), linear displacement sensor (7), linear displacement sensor signal shaper (8), 16-bit counter (9), analog-to-digital converter of the ADC (10) ), P are parallel LPT (11), an interface for exchanging information with PC (12), the sleeve with ultrasonic vibration transducers (13). Graphite rings (14) belong to the speaker system (15) of the zirconium tube.

 The operation of the device consists of three main parts - this is the installation of the operating mode in the acoustic system, then the calibration and the mode of direct registration of pressure when scanning a zirconium pipe. A sleeve with ultrasonic sensors is installed in the zirconium pipe TK and the device is turned on. On the included PC, the Test program starts. exe, from the menu of which Rejim is selected to set the operating mode of the speaker system. exe. When this program is started, the generator (1) of the device generates a signal with an ultrasonic frequency of 51.2 kHz and an amplitude of 5 V, which is transmitted to the emitter (2) and to the analog-to-digital converter (10) and digitally transmitted to the PC via the parallel interface (11) (12), which, according to the same program, performs the inverse conversion of a digit into an analog signal and displays the emitter signal on the PC monitor screen. At the same time, the acoustic signal from the receiver (2) is fed to the amplifier (3). From the output of the amplifier (3), the amplified acoustic signal of the system enters the ADC (10) and digitized through the interface (11) enters the PC memory (12), which displays the analog signal of the speaker system on the monitor screen. When superimposing two signals, the emitter and the receiver, an assessment is made of the working state of the speaker system. If necessary, the program allows you to change the frequency of the ultrasonic signal of the emitter (2) with a resolution of 32 Hz. After establishing the operating mode in the speaker system, they switch to the calibration mode. To do this, put on a separate contact graphite ring with a metal clamp on the pipe and place a sleeve with sensors opposite it. On the PC, the Kalibr program is selected and launched for execution from the menu. exe.

 Having chosen the range of recording the pressure force, a graphite ring is pulled together with a metal clamp as indicated by a force meter, for example 5 kg. In this case, the ultrasonic signal of the working frequency from the generator (1) is supplied to the emitter (2). The acoustic signal from the receiver sensor (6) is amplified by an amplifier (3), rectified by an active medium-voltage rectifier (4) to a constant voltage and, passing through an active low-pass filter (5), is fed to the ADC (10), digitized and then through the interface ( 11) enters the PC memory (12), where the constant voltage program assigns a compression force value of 5 kg. The value of this correspondence is entered into the PC (12). Then, the compression of the graphite ring is removed and the digitized value of the constant voltage corresponding to zero pressure is also stored in the PC memory (12). To form a scale for the dependence of the receiver output voltage on the pressure force, it is required to store several intermediate values for pressure forces from 1 kg to 5 kg in the PC memory (12). After performing the calibration procedure, they switch to the mode of direct measurement of the pressure force of graphite rings on the pipe. To do this, the Registr program is selected to start from the software menu. exe. In this mode, the device operates as follows: the generator (1) is turned on, the acoustic signal of the system from the output of the receiver (6), passing the amplifier (3), the active rectifier (4), the active filter N.Ch. (5), the ADC (10) through the interface (11) enters the PC memory (12). Simultaneously with the receiver signal, a signal from the linear displacement sensor (7), which passes through the signal shaper (8), a 16-bit counter (9), and an interface (11), is sent to the PC (12). When scanning a technological channel (TC), which is carried out by a sleeve (13) with sensors (2) and (6) by means of an electric drive, the values of the processed acoustic signal from graphite rings and the signal from the sensor are entered into the PC memory (12) using the Registr.exe program linear displacement located on the edge of the zirconium pipe. Registr program. exe operates in the ON-LINE mode, which when scanning displays on the PC monitor screen (12) a graph of the distribution of the pressure force of graphite rings over the height of the process channel.

 Currently, a program and base is being prepared for the implementation of the proposed device at the Smolensk nuclear power plant.

Claims (4)

 1. A method for determining the pressure force of a contact graphite ring on a zirconium pipe in the technological channel of the RBMK reactor (high-power channel reactor) by recording by the receiver of ultrasonic vibrations of the acoustic signal generated from the ultrasonic action of the emitter on the acoustic system consisting of a zirconium pipe filled with water and damped with graphite rings, characterized in that the acoustic system sets the operating mode with low quality factor and high sensitivity to damping with graphite rings, calibrate the scale of the dependence of the reflected ultrasound radiation pressure on the pressure of the contact graphite ring on the zirconium pipe using an additional graphite ring worn on the pipe, scan the emitter and ultrasonic vibrations receiver of the zirconium pipe damped by the graphite rings, record the magnitude of the amplitude and phase acoustic signals coming from graphite rings and determine the pressure force of the graphite ring on the pipe in accordance According to the previously obtained calibration scale. 2. The method of determining the pressure force according to claim 1, characterized in that for the establishment of an operating mode with a low quality factor and high sensitivity to damping by graphite rings in the acoustic system, the frequency of the ultrasonic signal of the emitter is f = 51.2 kHz ± 0.1 kHz, or f = 58.1 kHz ± 0.1 kHz, or f = 65.63 kHz ± 0.1 kHz, or f = 77.87 kHz ± 0.1 kHz, or f = 89.85 kHz ± 0.1 kHz and an amplitude in the range of 4 to 5V in the sweep to afford antiphase signal receiver relative to the emitter and a signal delay in the range 0-45 ^o, allowing SET put into speaker forced standing wave mode amplitude 0-0,5V range.  3. A device for determining the pressure force of a contact graphite ring on a zirconium tube in the technological channel of the RBMK reactor (high-power channel reactor), including an emitter and a receiver of ultrasonic vibrations, a frequency generator for emitter operation and a receiver signal conversion module containing an analog-to-digital converter and operating under the control of a personal computer (PC), characterized in that it further comprises a module including a sleeve containing an emitter and an ultrasound receiver new oscillations, which are located diametrically opposite on the same line, placed in a zirconium tube when scanning the location of the graphite ring, a linear displacement sensor that detects the position of the sleeve in the zirconium tube, and the signal receiver module of the device contains an additional amplifier, an active half-wave rectifier of average value and active low-pass filter, while the frequency generator for the emitter is running a PC.  4. The device according to claim 3, characterized in that the device uses a quartz frequency generator with a frequency resolution of 32 Hz.

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