Method and device for checking gas gap in process channel of uranium-graphite reactor

FIELD: operating uranium-graphite reactors.

SUBSTANCE: proposed method for serviceability check of process-channel gas gap in graphite stacking of RBMK-1000 reactor core includes measurement of diameters of inner holes in graphite ring block and process-channel tube, exposure of zirconium tube joined with graphite rings to electromagnetic radiation, reception of differential response signal from each graphite ring and from zirconium tube, integration of signal obtained, generation of electromagnetic field components from channel and from graphite rings, separation of useful signal, and evaluation of gap by difference in amplitudes of signals arriving from internal and external graphite rings, radiation amplitude being 3 - 5 V at frequency of 2 - 7 kHz. Device implementing this method has calibrated zirconium tube installed on process channel tube and provided with axially disposed vertically moving differential vector-difference electromagnetic radiation sensor incorporating its moving mechanism, as well as electronic signal-processing unit commutated with sensor and computer; sensor has two measuring and one field coils wound on U-shaped ferrite magnetic circuit; measuring coils of sensor are differentially connected and compensated on surface of homogeneous conducting medium such as air.

EFFECT: ability of metering gas gap in any fuel cell of reactor without removing process channel.

2 cl, 9 dwg

 

The proposal relates to techniques for operating a uranium-graphite nuclear reactors of the RBMK type and can be used to control the state of the reactor core.

During operation of the RBMK-1000 reactors under the action of radiation, temperature, and channel and pressure of the coolant, change the shape of the channel pipe, graphite blocks and rings due to the phenomena of creep and radiation growth. At the same time until the onset of the critical fluence is reduced diametral clearance “TC-graphite masonry” and the lower height of the graphite columns.

This in turn can lead to exhaustion project diametral clearance between zirconium pipe technology channel (TC) and outer graphite ring (ha) and the occurrence of contact between the channel and the graphite walls and, as a consequence, their “jamming”. There are also additional stresses in the graphite blocks, which leads to premature cracking, distortion of masonry in General. All these circumstances are beyond design basis and result in reduced service life of the reactor.

Currently, the term safe operation of many TC can be extended for several years provided a systematic monitoring of the technical condition of the channels without removing channels (control through tenku TC) with accurate measurement of gas gaps “TC-graphite and selective replacement of potentially dangerous channels. This will significantly reduce the process of overhaul, repair, and will also reduce the period of layoff units for mass change channels. Estimated time of exhaustion of the gas gap, as well as the experience of the evaluation of the gap according to the results of indirect measurements of the dimensions showed that for each of the fuel cell gap of the individual and the process of closing may take from 15 to 25 years. The estimated time of the beginning of the transition period graphite and rings from shrinking the swelling is ~20 years of operation (critical fluence). So after selective replacement parts is potentially dangerous to the criterion of exhaustion gap TC after ~20 years of operation in the replacement of the remaining channels will no longer be necessary, at least until the expiry of the project resource manual TC - 30 years.

In connection with the foregoing, a special significance is the development of methods and hardware for periodic measurements of gaps in the system “TC-graphite non-destructive method (control through the wall of the channel, without removing TC).

The aim of the invention is to provide a method and device by direct measurement (through the wall of the channel pipe TC) values of the gas gap on any of the fuel cell uranium-graphite nuclear reactor without removing TC.

This goal is achieved due to the fact that in the method of control gas gap is TC uranium-graphite nuclear reactor, including the measurement of internal diameters of the holes in the block of graphite rings and channel tunnel technological channel, the effects of electromagnetic radiation on zirconium pipe, fitting with the graphite rings, capture differential signal response from each of the graphite ring and zirconium tubes, integrating the received signal, the fixing components of the electromagnetic field from the channel pipe technology channel and graphite rings, the selection of the useful signal and determining the size of the gap by the difference between the magnitudes of the amplitudes of the signals from the inner and outer graphite rings, the effect of lead radiation with an amplitude of 3-5 and frequency 2-7 kHz. The device to control gas gap TC uranium-graphite nuclear reactor designed in the form mounted on the channel tunnel technological channel calibration zirconium tubes with axially located vertically movable differential vector-difference sensor of electromagnetic radiation with the mechanism of its movement, the block of electronic signal processing is switched to the sensor and the computer, when this sensor is designed as two measuring and one of the exciting coils are assembled on the U-shaped ferrite magnetic core, and a measuring coil dates the ICA included counter and compensated on the surface of a homogeneous conducting medium, for example the air and on the outer surface of the calibration tube is assembled block of graphite rings with fixed gaps.

When looking for unique and prototype technical solutions are not found, similar to the distinctive features of the claimed solution, which proves the compliance of the claimed combination of features of the criteria of the invention “Inventive step”.

The essence of the proposed technical solution is disclosed in relation to the RBMK-1000 reactor, the fragment object control with pre-extracted heat-generating Assembly is depicted in figure 1.

Figure 2 - section a-a in figure 1.

Figure 3 - cross-section B-B in figure 1.

Figure 4 is a structural diagram of a device for controlling the gas gap of the LC.

Figure 5 - a section b-b In figure 4. Schematic diagram of the sensor of electromagnetic radiation.

Figure 6 is a fragment of the diagram with signals from the grid spacers and graphite rings obtained when the control gap of the LC, aged 19 years.

Figure 7 is a fragment of a chart with hindering factors.

On Fig - fragment chart with detuning from interfering factors.

Figure 9 is a fragment of a chart of measurements on the new channel without interfering factors.

The object of the control of nuclear reactor RBMK-1000 has the following dimensions (figure 1):

pipe 1 the middle part of the technological channel made of alloy Zr+2.5% Nb (alloy E on THE 95.535-78) and has an outer diameter mm (internal diametermm) with a wall thickness of 4±0.3 mm;

- internal graphite ring 2 has an inner diameter 88+0,23mm and outer diameter of 111-0,23mm;

- outer graphite ring 3 has an inner diameter 91+0,23mm and the outer diameter of 114.3-0,23mm;

graphite clutch 4 height consists of 14 graphite blocks with a height of 200, 300, 500 and 600 mm; geometrical parameters of the block rectangle section 250×250 mm with an inner bore diameter of 114+0,23mm;

- gap “TC-outer graphite ring (diametrically) -radial -.

In accordance with the claimed method, the rate control gas gap TC fuel cell uranium-graphite nuclear reactor is as follows.

Inside zirconium tubes enter the sensor of electromagnetic radiation, and through its influence of electromagnetic radiation on the system “TC-graphite. The effects are radiation with an amplitude of 3-5 and frequency 2-7 kHz. At the same time record the response signal and record it in the form of diagram (Fig.6 and 7). The response signals contain complex differential spectrum of the frequency characteristics, which includes:

- change the gap between the zirconium tube TC and graphite to ICOM outer (useful signal);

- change the gap between the sensor and the inner surface of the pipe (gap-sensor “pipe”);

- change the electric conductivity and magnetic permeability of the pipe materials, graphite rings and blocks;

- change the thickness of the pipe wall;

- change the inner and outer diameters of the pipe;

the presence of slits in graphite rings;

- the presence of oxide (ZrO2) and corrosion (Fe2About3) deposits on the inner surface of the pipe;

- change in the contact resistance between the rings;

- the presence of defects such violations discontinuities in the metal channel of the pipe and, in particular, on the inner surface of the pipe.

These characteristics of the signal response except the first are interfering factors.

The chart plot of TC, worked continuously for more than 19 years of age (6), one can see the characteristic signals from the graphite rings, which are located on the pipe with a large contribution of confounding factors, the main of which are corrosive deposits, especially in the locations of the spacer grids of the fuel Assembly (FA) and changes in the electrical conductivity of zirconium tubes and graphite rings.

For the detuning from the influence of interfering factors (variation of the electrical resistance of zirconium tubes, graphite rings, corrosion deposits on the inner surface the values of TC and so on) that perform the amplitude-phase registration and processing of the response signals. Simultaneous recording of the amplitude and phase of the response signals and their joint processing on your computer allows you to electronically separate the signals from zirconium tubes and the graphite ring, because it made the active component of the electrical resistance of the sensor caused by the component environment with a high conductivity (i.e. zirconium pipe). Made reactive component due to the action niskopropusni component of the environment, i.e. with the graphite rings.

To obtain correct values of the received signal integrate, build from interfering factors and separated from the response signal components of the electromagnetic permeability of zirconium tubes and graphite rings. Rebuilt from interfering factors signal response is depicted in Fig.9. Using the chart, determine the gas gap between the outer wall of the zirconium tubes and any of 272 graphite rings TC. It is equal to the distance between the maximum and minimum values of the amplitudes (peaks) recorded response signals.

Device for controlling the gas gap (figure 4) made in the form of calibration zirconium tubes 1, on the outer surfaces of which are alternately arranged inner 2 and outer 3 graphite rings with fixed gaps. All this system is in the working position is set on the cell the technological channel (not shown) with the previously extracted heat-generating Assembly. Axial gauge pipe 1, and hence TC is vertically movable sensor 5 of electromagnetic radiation. The sensor 5 is connected with a drive mechanism 6, intended for vertical movement sensor height zirconium tubes. Sensor 5-up unit 7 e signal processing and computer 8 cable 9 and consists of two measuring coils 10 and one excitation coil 11 collected on the U-shaped ferrite magnetic core 12.

When measuring the gap between the graphite ring 3 and zirconium pipe 1 insertion resistance is determined by the parameters of the graphite ring and zirconium tubes. Because the magnetic field sensor shielded zirconium pipe, the conductivity of which at least 10 times higher than that of graphite, and the pipe is much closer to the sensor than graphite, the absolute value of the deposited graphite ring resistance is extremely small. At the same time, the gradients of the electromagnetic properties of the pipe TC give a contribution comparable or greater contribution from graphite rings. So in these conditions it was possible to register unchanging signal from graphite rings, you want to compensate the signal from zirconium tubes. This is due to the fact that the sensor is a differential vector differential, sostoyanii two measuring coils 10 and a coil 11 of excitation, installed on a common U-shaped ferrite magnetic core 12. The measuring coil 10 of the sensor 5 includes a counter and compensated on the surface of a homogeneous conducting medium, for example air, so that the total EMF removed from coils of 0 for symmetrical installation of the sensor on the surface of a homogeneous conducting medium, in particular on the surface of zirconium tubes. If there is any heterogeneity near one of the poles of the magnetic circuit occurs differential EMF proportional to the magnitude of the insertion resistance, which is reflected in the chart measurements.

The device is little sensitive to the oxide films and corrosion deposits on the inner surface of the zirconium tubes. As the sensor used invoice vector differential eddy current probe (figure 5). In the sensor 5 exciters and receivers of electromagnetic fields near the local area are inductors with a ferrite magnetic core.

Measurement is carried out at a frequency of electromagnetic waves 2-7 kHz.

The input electromagnetic waves and reception of the response signals is performed using a single sensor 5 installed at a fixed distance from the inner surface of the Zirconia part of the LC.

Measurement of clearances of all 272 rings TC is performed during continuous movement of electron gitogo sensor 5 on the inner surface of the zirconium tubes with writing the received information into the personal computer 8. To do this, the response signals of the sensor pre-amplify, convert into digital form in an electronic unit 7 and is passed to storage and further processing in the computer 8. The device scans a small area of the graphite ring and the pipe directly in front of the sensor. The analysis of the response signals allows to establish a detailed picture of the location of each of the 272 graphite rings on zirconium tube channel.

Structurally, the electromagnetic sensor is installed in the hollow cylinder (figure 4) on wheel supports having opposite from the wheel-side spring-loaded thrust bar. The sensor 5 is placed in the middle of the cylinder in the socket with the device position adjustment. A sinusoidal voltage with amplitude of the order of 3-5 and frequency 2-7 kHz is fed to the excitation coil sensor multi-conductor cable 9. Response signal from the signal coil 10 on the same cable is transmitted to the electronic unit 7. The findings of the cable 9 is attached to the terminals of the sensor 5 and sealed epoxybutane.

The transfer mechanism 6 is designed for uniform displacement sensor height TC, and if necessary to stop it at a given altitude. The mechanism consists of a base-gauge pipe 1, a winch and an electric motor with a gearbox (not shown.)

The calibration tube 1 made of zirconium JV is ava and the bottom part has a node, allowing rigidly fix the design relative to the TC, on the outer surfaces of which are alternately arranged inner 2 and outer 3 graphite rings with fixed gaps. When lowering the sensor in TC usually write this section of the calibration tube with rings, and this information is used for the absolute calibration of the sensitivity of the sensor of electromagnetic radiation.

Unit 7 electronic processing produces signals survey of the sensor, performs recording and storing the response signals, produces transfer all the recorded information in the form of a data file in the computer 8 for further processing, while the real time display shows the current sensor reading on the display.

The measurement time for a single channel - 5 minutes

A typical entry area TC placed on zirconium tube graphite rings shown in Fig.6, 7, 8 and 9. Peaks with a maximum amplitude correspond to the internal graphite rings with zero gap, and peaks with small - amplitude external graphite rings set with a design clearance of 1.5 mm, the difference between the amplitude values from the inner and outer graphite rings corresponds to the radial gap of 1.5 mm Recording such information for each channel every year for several years and comparing it between Soboh is, you can get the values of the velocity of radiation-induced swelling of graphite and plastic deformation (creep) zirconium tubes for different areas of the reactor core. This information will allow you to track the dynamics of radiation-induced swelling of the graphite and to predict the actual timing of the exhaustion gap for each channel, and the accuracy of the forecasts will grow as you collect information.

The chart plot of TC, worked continuously for more than 19 years, (6) one can see the characteristic signals from the graphite rings, which are located on the pipe with a large contribution of confounding factors, the main of which are corrosive deposits, especially in the locations of the fuel Assembly grid spacers, and changes in the electrical conductivity of zirconium tubes.

For the detuning from the influence of interfering factors (variation of the electrical resistance of zirconium tubes, graphite rings, corrosion deposits on the inner surface of the LC and so on) that perform the amplitude-phase registration and integral processing of the response signals.

Simultaneous recording of the amplitude and phase of the response signals, their joint processing on your computer allows you to electronically divide and allocate the response signals separately from zirconium tubes and the graphite ring, because it made the active component electrode the resistance of the transducer caused by the component environment with a high conductivity (i.e. zirconium tube). Made reactive component due to the action niskopropusni component of the environment, i.e. the graphite rings.

Figure 7 (right side of diagram) are clearly visible signals from interfering factors on the site zirconium tubes, free from graphite rings, mainly related to raznesennost zirconium tubes, the presence of the oxide film ZrO2and corrosion deposits Fe2About3. These interfering factors create for the useful signal of the uneven substrate, which significantly distorts the signal and does not allow to correctly identify the gap. Therefore, to highlight only useful component of the differential signal response it integrate with the geometrical parameters of the rings, share and produce the response signals separately from zirconium tubes and each graphite rings constituting the electromagnetic permeability. After the removal of interfering factors account on the diagram takes the form shown in Fig and Fig.9. Obvious smoothed ordinate the response of the interfering factors and, as a consequence, a stable amplitude in the response signals from the external and internal rings.

Thus, the proposed technical solution in the aggregate of the stated features allows you not only to assess the state of the gas gap of the LC in the indicator mode is e, but after detuning from interfering factors (corrosion deposits, varying wall thickness, holes in the locations of the grid spacers FA, changes in the conductivity of zirconium tubes and graphite rings etc) to determine its actual value.

1. The control method of a gas gap of technological channel of the uranium-graphite nuclear reactor, including the measurement of internal diameters of the holes in the block of graphite rings and channel tunnel technological channel, the effects of electromagnetic radiation on zirconium pipe, fitting with the graphite rings, capture differential signal response from each of the graphite ring and zirconium tubes, integrating the received signal, the fixing components of the electromagnetic field from the channel pipe technology channel and graphite rings, the selection of the useful signal and determining the size of the gap by the difference between the magnitudes of the amplitudes of the signals from the inner and outer graphite rings, the effect of lead radiation with an amplitude of 3-5 and frequency 2-7 kHz.

2. The device for implementing the method according to claim 1, made in the form mounted on the channel tunnel technological channel calibration zirconium tubes with axially located vertically movable differential vector dierence mitchiko the electromagnetic radiation and the mechanism of its movement, unit electronic signal processing is switched to the sensor and the computer, when this sensor is made in the form of measuring two and one coil excitation, collected on the U-shaped ferrite magnetic core, and measuring the sensor coil connected in opposite and offset on the surface of a homogeneous conducting medium, e.g. air, and on the outer surface of the calibration tube is assembled block of graphite rings with fixed gaps.



 

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FIELD: operating uranium-graphite reactors.

SUBSTANCE: proposed method for serviceability check of process-channel gas gap in graphite stacking of RBMK-1000 reactor core includes measurement of diameters of inner holes in graphite ring block and process-channel tube, exposure of zirconium tube joined with graphite rings to electromagnetic radiation, reception of differential response signal from each graphite ring and from zirconium tube, integration of signal obtained, generation of electromagnetic field components from channel and from graphite rings, separation of useful signal, and evaluation of gap by difference in amplitudes of signals arriving from internal and external graphite rings, radiation amplitude being 3 - 5 V at frequency of 2 - 7 kHz. Device implementing this method has calibrated zirconium tube installed on process channel tube and provided with axially disposed vertically moving differential vector-difference electromagnetic radiation sensor incorporating its moving mechanism, as well as electronic signal-processing unit commutated with sensor and computer; sensor has two measuring and one field coils wound on U-shaped ferrite magnetic circuit; measuring coils of sensor are differentially connected and compensated on surface of homogeneous conducting medium such as air.

EFFECT: ability of metering gas gap in any fuel cell of reactor without removing process channel.

2 cl, 9 dwg

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