JP5022886B2 - Moisture detection method, moisture detection device and pipe inspection device - Google Patents

Description

  The present invention relates to a moisture detection method, a moisture detection device, and a pipe inspection device, and in particular, is applied to detection of moisture in a heat insulating material provided around a tower and a tank such as a distillation tower of a chemical plant and a pipe. The present invention relates to a moisture detection method, a moisture detection device, and a pipe inspection device that are suitable for use.

  Conventionally, pipe inspection in a plant such as a chemical plant, that is, detection of moisture in a heat insulating material surrounding the pipe has been performed using visual observation, ultrasonic waves, or eddy currents. However, in this pipe inspection method, since it is necessary to remove the metal cover and the heat insulating material, a great amount of labor and time are required for the pipe inspection. Moreover, it was necessary to stop the chemical plant during the pipe inspection.

  As a method of inspecting the pipe without removing the metal cover and the heat insulating material, there is a method of measuring moisture in the heat insulating material that causes corrosion of the pipe. In this method, neutrons generated from a neutron source such as californium are irradiated from the outside of the metal cover, the neutrons are decelerated by the moisture in the heat insulating material, and then the heat scattered in the direction opposite to the neutron irradiation direction. This is a method for measuring a neutron flux (Japanese Patent Publication No. 7-58253). The amount of moisture contained in the heat insulating material is identified based on the measured thermal neutrons.

Japanese Patent Publication No. 7-58253

  The method described in Japanese Patent Publication No. 7-58253 is affected by the background of thermal neutrons generated from a neutron source and the background of thermal neutrons other than those to be inspected. The quantity cannot be measured accurately. In particular, it is impossible to distinguish between thermal neutrons generated by decelerating with liquid (heavy oil, kerosene, etc.) flowing in the piping of chemical plants and thermal neutrons generated by decelerating with moisture contained in the heat insulating material. It is difficult to inspect the pipe by the method described in Patent Document 1 during the operation of the chemical plant in which the liquid is flowing.

  An object of the present invention is to provide a moisture detection method, a moisture detection device, and a pipe inspection device that can accurately measure the position of water in a heat insulating material without stopping the flow of liquid in an inspection object.

  A feature of the present invention that achieves the above-described object is that a pulsed fast neutron having a single energy is irradiated to a heat insulating material attached around a test object in which a liquid exists, and is generated by the fast neutron. The time change in the intensity of thermal neutrons traveling in the direction opposite to the irradiation direction of fast neutrons is calculated based on the time of generation of pulsed fast neutrons, and based on the obtained information on the time change, To find the position of water in

Since this invention irradiates the heat insulating material of the inspection object location with the pulsed fast neutron having a single energy, the irradiation direction of the fast neutron in the state where the liquid flows in the inspection object (for example, piping) Can calculate the temporal change in the intensity of thermal neutrons traveling in the reverse direction, based on the time of generation of fast neutrons.
For this reason, since the time when the thermal neutron was generated can be obtained based on the obtained information of the time change, the water in the heat insulating material can be obtained even when the liquid is flowing in the inspection object (for example, piping). Can be determined. Therefore, the position of water in the heat insulating material can be accurately measured without stopping the flow of liquid in the inspection object (for example, piping).

  “Thermal neutrons traveling in the direction opposite to the irradiation direction of fast neutrons” include not only the direction opposite to the irradiation direction by 180 ° but also thermal neutrons having a velocity component that proceeds in the direction opposite to the irradiation direction by 180 °. It is out.

  Examples of inspection objects include distillation towers, reaction towers, reaction tanks, adsorption towers, mixing tanks and other towers and tanks, tanks (such as tanks filled with chemicals used in plants and petroleum tanks), and piping.

  ADVANTAGE OF THE INVENTION According to this invention, the position of the water in a heat insulating material can be accurately measured, without stopping the flow of the liquid in piping.

  The present invention provides various methods for the inventors to distinguish between thermal neutrons generated by decelerating with liquid flowing in the inspection object (piping and distillation tower) and thermal neutrons generated by decelerating with moisture present in the heat insulating material. It was made based on new findings obtained through examination. This finding is that the thermal neutrons can be distinguished by irradiating the heat insulating material with pulsed neutrons having a single energy. In addition to piping and distillation towers, inspection objects include towers and tanks such as reaction towers, reaction tanks, adsorption towers and mixing tanks, and tanks. The contents of the new knowledge will be specifically described below. The following description will be made with reference to a pipe that is an inspection object, but the same applies to towers, tanks, and tanks.

As a neutron generator for generating pulsed fast neutrons having a single energy, for example, an apparatus for generating neutrons using a fusion reaction of deuterium and deuterium was used. By causing the accelerated deuterium ions to collide with deuterium stored in a hydrogen storage alloy such as titanium in a pulsed manner, neutrons having an energy of about 2.5 MeV are generated in a pulsed manner. The generated pulsed fast neutrons (hereinafter referred to as pulsed fast neutrons) are irradiated from the outside of the metal cover onto a pipe with a heat insulating material covered with a metal cover. Fast neutrons with an energy of about 2.5 MeV travel about 22 m per microsecond because the velocity is about 2.2 × 10 ⁷ m / sec. The irradiated pulsed fast neutrons are scattered by the metal cover, the heat insulating material, the moisture in the heat insulating material, the piping and the liquid in the piping, and lose energy to become thermal neutrons. The fast neutrons lose almost no energy in the case of scattering by metal, and most of the energy is lost by scattering by light elements contained in moisture or the like, and are converted into thermal neutrons in a few microseconds. Among such thermal neutrons, thermal neutrons traveling in the opposite direction to the irradiation direction of pulsed fast neutrons were made incident on a neutron injector such as a ³ He neutron detector. The average energy of thermal neutrons is 0.025 eV, and the velocity is about 2200 m / sec. Therefore, the traveling speed is about 2.2 cm per 10 microseconds. This thermal neutron is detected by the neutron injector at the time when the time required from the position where the thermal neutron is made to enter the neutron injector has elapsed. The position of thermal neutronization can be identified from the detection time of thermal neutrons based on the time when pulsed fast neutrons having a single energy are generated. The amount of water can be identified from the thermal neutron flux measured at that time. Therefore, by using pulsed fast neutrons with a single energy generated by a neutron generator, and by measuring the time variation of the thermal neutron count rate based on the generation time of the fast neutrons, thermal neutrons Since the converted position can be identified, the position of water present in the heat insulating material in a state where the liquid flows in the pipe can be obtained with higher accuracy. Without stopping the operation of a plant such as a chemical plant, the thermal insulation material can be irradiated with fast neutrons, the thermal neutrons generated by this irradiation can be measured, and the position of the water can be obtained. Since the operation of the plant is not stopped, the operation rate of the plant can be improved.

  Embodiments of the present invention will be described below with reference to the drawings.

A pipe inspection apparatus according to Embodiment 1 which is a preferred embodiment of the present invention will be described with reference to FIG.
This pipe inspection apparatus is a kind of moisture detection apparatus that detects a corroded place and a place where corrosion is likely to occur in a pipe that is an inspection object, and each of the pipe inspection apparatuses of Examples 2 to 5 to be described later. Included in moisture detector. The pipe inspection apparatus 15 of this embodiment includes a neutron generator tube (neutron generator) 1, a neutron detector ³ He proportional counter (neutron injector) 2, a controller 4, a multichannel wave height analyzer 8, and data processing. A device 9 is provided. The BF ₃ proportional counter 2 may be used as a neutron detector. A power source 3 is connected to the neutron generator tube 1 by a cable. ^{The 3} He proportional counter 2 is connected to a multichannel wave height analyzer 8 via a preamplifier 6 and an amplifier 7. A high voltage power supply 5 is connected to the preamplifier 6. A data processing device 9 is connected to the multichannel wave height analyzer 8 and the display device 16. The control device 4 is connected to the power source 3 and the multichannel wave height analyzer 8. Neutron generating tube 1 and ³ He proportional counter 2 are attached to a support member (not shown).

A heat insulating material 12 is attached to the pipe 11 so as to surround the pipe 11 that is an inspection object. The pipe 11 is, for example, a chemical plant pipe. A metal cover 13 covers the outer surface of the heat insulating material 12. A liquid (for example, any one of heavy oil, light oil, kerosene, chemical substances, etc.) 10 flows in the pipe 11. The neutron generating tube 1 and the ³ He proportional counter 2 face the surface of the metal cover 13, and their axial centers are arranged in the radial direction of the pipe 11.

The water 14 existing in the heat insulating material 12 is rainwater that has entered between the metal cover 13 and the pipe 11 through a gap between the metal cover 13 of the pipe 11 installed outdoors. This water 14 causes corrosion of the pipe 11. The inspection performed using the pipe inspection device 15 for the pipe 11 arranged outside the chemical plant will be described below. The pipe inspection device 15 has a weight and a size that can be moved by an inspector. The inspector attaches the neutron generator tube 1 of the pipe inspection device 15 and the ³ He proportional counter tube 2 which is a neutron detector to the support member, and arranges it at a predetermined distance from the outer surface of the metal cover 13 at the inspection location. . The support member is placed so as not to fall on the ground or the concrete surface on which the pipe 11 is installed. The inspector uses an input device (not shown) connected to the data processing device 9 to measure the diameter of the pipe 11, the thickness of the heat insulating material 12 and the metal cover 13, and from the metal cover 13 to the neutron generator 1 and ³ He proportional counter. Information such as the distance up to 2, the type name of the liquid 10 flowing in the pipe 11 (for example, names of kerosene, heavy oil, chemical substances, etc.) and the material of the heat insulating material are input. These pieces of information are stored in a memory (not shown) of the data processing device 9.

The control device 4 generates a pulsed first control command at a predetermined first time interval based on a clock signal from a clock generator (not shown), and the power source 3 is turned on based on the first control command. Control. The power source 3 is turned on and off at the first time interval, and a high voltage is applied to the neutron generating tube 2 in the ON state. Thereby, the neutron generating tube 2 generates pulsed fast neutrons 20 at the first time interval. Specifically, as shown in FIG. 2 (A), the neutron generating tube 1 generates fast neutrons 20 having a time width t at times T1, T3, T5, T7. It occurs in pulses. As the neutron generating tube 1, a neutron generating tube that generates fast neutrons by fusion reaction of deuterium and deuterium is used. The neutron generating tube 1 generates fast neutrons 20 having a single energy of about 2.5 MeV. As the neutron generating tube 1, it is also possible to use a neutron generating tube that generates fast neutrons by a fusion reaction of tritium and deuterium.
In this case, monoenergetic fast neutrons 20 of about 14 MeV are generated in the neutron generator tube.

  The generated fast neutrons 20 lose energy by elastically scattering with the metal cover 13, the heat insulating material 12, the water 14 existing in the heat insulating material 12, the pipe 11 and the constituent elements of the liquid 10 flowing in the pipe 11. The thermal neutrons 21 with lower energy are obtained. The fast neutron 20 loses a lot of energy mainly by elastic scattering with an element having a small atomic number (for example, hydrogen element), and hardly loses energy by elastic scattering with an element having a large atomic number. For this reason, the fast neutron 20 loses little energy depending on the metal cover 13, the heat insulating material 12, and the pipe 11, and mainly loses energy due to the water 14 and the liquid 10 to become thermal neutrons 21.

The thermal neutron 21 has lost energy due to the elastic scattering of the fast neutron 20 and thus may fly in all directions. Among these thermal neutrons 21, thermal neutrons 21 flying in the direction opposite to the direction of irradiation with fast neutrons 20 are detected by the ³ He proportional counter 2. A high voltage from the high voltage power source 5 is applied to the ³ He proportional counter 2 via the preamplifier 6. ^{The 3} He proportional counter 2 detects the thermal neutron 21 by detecting protons, which are charged particles generated by a nuclear reaction between the thermal neutron 21 and ³ He. That is, when the generated proton energy is lost internally, the ³ He proportional counter 2 generates a current signal corresponding to the lost energy. ^{Since 3} He has a very small reaction with other than thermal neutrons, the ³ He proportional counter 2 detects almost only the fast neutrons 21 without detecting the incident fast neutrons 20. The current signal output from the ³ He proportional counter 2 is converted into a voltage signal through the preamplifier 6 and the amplifier 7 and input to the multichannel wave height analyzer 8. The multi-channel wave height analyzer 8 analyzes the height of the voltage signal and obtains the energy spectrum of protons generated by the nuclear reaction. This energy spectrum information is input from the multichannel wave height analyzer 8 to the data processor 9. The multichannel wave height analyzer 8 is based on a pulse-shaped second control command (sampling command) output at a predetermined second time interval determined by the clock signal from the control device 4 at a second time interval. Proton energy spectrum information is obtained for each sampled voltage signal. The second time interval is much shorter than the first time interval. Therefore, for example, the voltage signal is sampled many times between time T and time T3, and the number of proton energy spectra obtained by the multichannel wave height analyzer 8 is the same. The sampling of the voltage signal, that is, the measurement of thermal neutrons, is based on the generation time of the fast neutrons 20 generated in the neutron generating tube 1 (for example, times T1, T3, T5, T7. This is done based on the command.

The data processing device 9 performs the following processing on the energy spectrum information of each input proton. That is, information on the energy spectrum of thermal neutrons is extracted from the energy spectrum information of protons. In other words, information on the energy spectrum of thermal neutrons can be obtained by separating noise information such as energy spectrum information of γ rays from proton energy spectrum information. The information on the energy spectrum of the obtained thermal neutron is integrated to calculate the number of thermal neutrons detected by the ³ He proportional counter 2 per unit time (thermal neutron detection rate) (thermal neutron intensity). This detection rate is calculated for each input energy spectrum information of protons. The data processing device 9 inputs information on the rate of occurrence of each fast neutron 20 generated at the predetermined time interval in the neutron generator tube 2. Information on this incidence can be obtained by a fast neutron measurement device 24 described later.

  The fast neutron measurement device 24 will be described in detail with reference to FIG. As described above, when the neutron generating tube 1 that generates fast neutrons using the fusion reaction of deuterium and deuterium is used as the neutron generating tube 1, the fast neutron measuring device 24 is used. The fast neutron measurement device 24 includes a charged particle detector 19, a preamplifier 6A, an amplifier 7A, a multichannel wave height analyzer 8A, and a data processing device 9A. The charged particle detector 19, the preamplifier 6A, the amplifier 7A, the multichannel wave height analyzer 8A, and the data processing device 9A are connected to each other in this order. The charged particle detector 19 is installed in the proton extraction unit 27 of the neutron generator tube 1.

  The neutron generating tube 1 collides the deuterium ions 25 generated by the above-described fusion reaction with the target 23 having occluded deuterium to generate fast neutrons and protons 26. This fast neutron is irradiated to the heat insulating material 12. The rate of proton generation is equal to that of fast neutrons. The generated protons 26 are detected by the charged particle detector 19. The proton detection signal detected by the charged particle detector 19 is amplified by the preamplifier 6A and the amplifier 7A and input to the multichannel wave height analyzer 8A. The multichannel wave height analyzer 8A performs the same processing as the multichannel wave height analyzer 8 to obtain the proton energy spectrum. The data processing device 9A obtains the proton detection rate using the proton energy spectrum information. The data processing device 9 </ b> A uses the information on the relative positional relationship between the target 23 and the charged particle detector 19 and the information on the size of the charged particle detector 19 to convert it into an overall proton generation rate. The generation rate of the whole proton is the generation rate of fast neutrons.

  The angular distribution of the fast neutron generation rate due to the fusion reaction of deuterium and deuterium is shown in FIG. When the energy of the deuterium ions is about 100 keV, the generation rate of fast neutrons irradiated in the same direction as the flight direction of the deuterium ions 25 is larger than the generation rate in the direction opposite to the flight direction. Therefore, by using the neutron generating tube 1 that generates a fusion reaction of deuterium and deuterium, it is possible to irradiate the pipe 11 to be inspected with many fast neutrons. The neutron generating tube 1 is a highly safe apparatus because fast neutrons are not generated by stopping irradiation of the deuterium ions 25 onto the target 23.

The data processing device 9 shown in FIG. 1 converts each image information shown in FIG. 2 based on each input fast neutron generation rate information and each calculated thermal neutron detection rate information (thermal neutron intensity information). The image information is generated and output to the display device 16. These image information, the pulsed fast neutrons 20 emitted from the neutron generator tube 1, the image information indicating the incidence of the respective time of occurrence (see FIG. 2 (A)), and the ³ He proportional counter 2 It is the image information (refer FIG. 2 (B)) of the detection rate of a thermal neutron calculated | required using the energy spectrum information of the proton obtained based on the output signal. The image information shown in FIG. 2B shows information on the distribution of thermal neutron detection rates in the state where the water 14 is present in the heat insulating material 12 (hereinafter referred to as first detection rate information). This image information includes a thermal neutron region a (hereinafter referred to as a water region a) generated based on the water 14 and a background thermal neutron region b (hereinafter referred to as a background region b). The image information shown in FIG. 2C shows information on the distribution of thermal neutron detection rate (hereinafter referred to as second detection rate information) when no water 14 is present in the heat insulating material 12, and the background region. Only b exists. The second detection rate information shown in FIG. 2 (C) indicates that the thermal neutrons scattered in the direction opposite to the irradiation direction of the fast neutrons 20 in the state where the water 14 does not exist in the heat insulating material 12 as described above. It is obtained in advance by measurement and stored in a memory (not shown) of the data processing device 9. The image information (FIG. 2B) showing the distribution of thermal neutron detection rate in the state where the water 14 is present in the heat insulating material 12 uses the first and second detection rate information in the data processing device 9, and these It is created by overlapping the information. The image information created by the data processing device 9 is output to the display device 16. The display device 16 displays the image information shown in FIGS. 2A and 2B when the water 14 is present in the heat insulating material 12, and when the water 14 is not present in the heat insulating material 12. Displays each piece of image information shown in FIG. 2 (A) and FIG. 2 (C). The distribution of the thermal neutron detection rate in the second detection rate information shown in FIG. 2C increases as the number of fast neutron 20 irradiations is repeated. This is because the thermal neutron lifetime is about 20 minutes, which is longer than the first time interval for irradiating the fast neutron 20, and the thermal neutrons measured by the ³ He proportional counter 2 increase.

The data processing device 9 subtracts the second detection rate information from the distribution information of the thermal neutron detection rate calculated for each proton energy spectrum information input during the pipe inspection. When water is present in the heat insulating material 12 by this calculation, the distribution information of thermal neutron detection rate larger than zero (information of temporal change in the intensity of thermal neutrons) in a certain period from the generation time of the fast neutron 20 as a base point. ) Is obtained. This distribution information is obtained, for example, by subtracting the distribution information shown in FIG. 2C from the distribution information of the thermal neutron detection rate in FIG. 2B, from time T1 to time T2, and from time T3 to time T4. The distribution information of the thermal neutron detection rate for the water region a in Distribution information of the thermal neutron detection rate for the background region b is not included. When there is no water in the heat insulating material 12, the thermal neutron detection rate becomes zero. The data processing device 9 further obtains the amount of water 14 based on the distribution information of the thermal neutron detection rate for the water region a obtained by the above calculation, and the time when the distribution information is generated (for example, time T1). To the position where the water 14 exists based on the time T2). Since the fast neutron 20 travels about 22 m per microsecond, the time when the fast neutron 20 irradiated from the neutron generating tube 1 reaches the position of the liquid 10 and the water 14 is substantially the same. Position the water 14 is present, the rate of thermal neutrons 21 fast neutrons 20 occurs is decelerated with water 14, the distance between the metal cover 13 with ³ He proportional counter 2, the thickness of the metal cover 13, And the time when the distribution information of the thermal neutron detection rate for the water region a is generated. The obtained information on the amount of water 14 and the location of the water 14 is output to the display device 16 and displayed.

The principle by which the position of the water 14 and the amount of the water 14 existing in the heat insulating material 12 can be detected by measuring the thermal neutron 21 traveling in the direction opposite to the irradiation direction of the fast neutron 20 will be described below. The detected thermal neutrons 21 are generated when the fast neutrons 20 lose energy in each of the water 14 and the liquid 10 in the pipe 11, so the detection rate of the thermal neutrons 21, the amount of water 14, and the heat The detection rate of neutron 21 and the amount of liquid 10 have a correlation with each other. The amount to be measured is the amount of water 14, but measurement of the water 14 becomes difficult when the ratio of the amount of thermal neutrons 21 generated by the liquid 10 is large. Therefore, in order to increase the ratio of the thermal neutron 21 generated by the water 14 to the thermal neutron 21 generated by the liquid 10 among the thermal neutrons 21 measured by the ³ He proportional counter 2, the velocity of the thermal neutron 21 is increased. Is about 2.2 cm per 10 microseconds. Since the distance between the water 14 and the ³ He proportional counter 2 is shorter than the distance between the liquid 10 and the ³ He proportional counter 2, the thermal neutron 21 from the water 14 is more than the thermal neutron 21 from the liquid 10. It is detected by the ³ He proportional counter 2 as soon as possible. In principle, the detection rate can be measured with a time resolution of about 10 microseconds. For this reason, the resolution of the position of about 2.2 cm is obtained. Fast (spread of detection time corresponding to the velocity distribution of the thermal neutrons 21) time spread of time, etc. to the neutron 20 thermal neutrons 21 is generated, the minimum distance and maximum from the water 14 to ³ He proportional counter 2 Difference in distance (because the ³ He proportional counter 2 is rod-shaped, there is a difference in detection time between the front end and the rear end of the counter 2) and the shortest distance from the liquid 10 to the ³ He proportional counter 2 Since the detection time is affected by the difference in the longest distance, the thermal neutron 21 from the water 14 and the thermal neutron from the liquid 10 cannot be completely separated. However, the thermal neutrons generated by the water 14 are measured by measuring the detection rate of the thermal neutrons 21 detected by the ³ He proportional counter 2 with reference to the generation time of the fast neutrons 20 generated by the neutron generator 1. The detection rate can be obtained. That is, the detection rate of the thermal neutron 21 obtained based on the output signal from the ³ He proportional counter 2 at every sampling time (measurement time) when the second control command is output based on the generation time. From this, by subtracting the background thermal neutron detection rate (for example, the detection rate of thermal neutrons from the liquid 10), the detection rate of thermal neutrons generated by the water 14 at each measurement time can be obtained. Thermal neutron detection rates for the background, as described above, in the absence of water 14 in the heat insulating material 12 is irradiated toward the high-speed neutrons 20 thermal insulation material 12, the thermal neutron 21 ³ He proportional counter 2 It can be obtained by measuring. The position where the water 14 exists can be obtained based on the time when the distribution information of the thermal neutron detection rate for the water region a is generated and the velocity of the thermal neutron generated in the water 14. Moreover, the quantity of the water 14 in the heat insulating material 12 is calculated | required as follows. The detection rate of thermal neutrons 21 corresponding to the amount of water 14 is measured in advance, and the thermal neutron detection rate corresponding to the amount of water 14 is stored in the memory of the data processing device 9. By reading the amount of water 14 corresponding to the thermal neutron detection rate obtained based on the output signal from the ³ He proportional counter 2 from the memory, the amount of water 14 can be measured.

  An example of the result of the water | moisture content test | inspection in the heat insulating material 12 of the piping 11 is shown in FIG. The neutron generating tube 1 generates fast neutrons 20 having a time width t in pulses at times T1, T3, and T5. The generated fast neutrons 20 are converted into thermal neutrons 21 by the water 14, and the thermal neutrons 21 correspond to the generation times of the pulsed fast neutrons 20 from time T1 to time T2, from time T3 to time T4, Detection is performed between time T5 and time T6. The generated fast neutrons 20 become thermal neutrons 21 due to the liquid 10 in the pipe 11, and the thermal neutrons 21 correspond to the generation time of the pulsed fast neutrons 20 mainly from the time T1 to the time T3. , And are detected between time T3 and time T5 and between time T5 and time T7, respectively. Therefore, by measuring the thermal neutron detection rate corresponding to the time, such as the thermal neutron detection rate from time T1 to time T2, from time T3 to time T4, and from time T7 to time T8, the liquid Therefore, the ratio of the detection rate of the thermal neutron 21 by the water 14 to the detection rate of the thermal neutron 21 by 10 can be increased, and the water 14 can be detected with high accuracy.

  In this embodiment, pulsed fast neutrons having a single energy are irradiated onto the inspection target portion, so that the irradiation is performed based on the generation time of the fast neutrons 20 while the liquid 10 is flowing in the pipe 11. A thermal neutron detection rate distribution corresponding to the neutron 20 can be obtained. For this reason, the position where the water 14 exists in the heat insulating material 12 can be accurately measured without stopping the flow of the liquid 10 in the pipe 11. The amount of water 14 present in the heat insulating material 12 can also be measured with higher accuracy.

When fast neutrons having a plurality of energies are irradiated on the inspection target location, a plurality of thermal neutrons having different energies are generated by the liquid 20 and the water 14. When these thermal neutrons are detected by the ³ He proportional counter 2, the respective distributions of thermal neutron detection rates of the respective energies overlap, and the S / N ratio deteriorates. In this embodiment, since single energy fast neutrons are irradiated, the S / N ratio of the detected detection rate is improved. Since pulsed fast neutrons are irradiated, thermal neutron detection rate distribution based on the generation time of fast neutrons 20 can be obtained. Therefore, as described above, even when the liquid 10 is flowing in the pipe 11, the position where the water 14 exists in the heat insulating material 12 (the position where the pipe 11 is corroded or the pipe 11 is corroded). Can be measured with high accuracy.

  In this embodiment, it is possible to know whether or not the water 14 exists in the heat insulating material 12 without stopping the operation of the chemical plant, that is, in a state where the liquid 10 is flowing in the pipe 11. When 14 exists, the position where the water 14 exists can be calculated | required more accurately. Since the operation of the chemical plant is not stopped, the operating rate of the chemical plant can be improved.

  Moreover, since the present Example uses the apparatus which produces | generates a fast neutron using the fusion reaction of deuterium and deuterium as the neutron generator tube 1, the generation rate of the fast neutron in the deuterium acceleration direction becomes high. Therefore, by setting the acceleration direction of deuterium as the irradiation direction of the fast neutron pipe, the ratio of the fast neutron generation rate irradiated to the pipe 11 with respect to the entire fast neutron generation rate can be increased. Good fast neutron irradiation. Furthermore, since the background can be lowered, the position where the water 14 is present in the heat insulating material 12 can be detected with higher accuracy.

In this embodiment, when the generated proton energy is lost inside the ³ He proportional counter 2, a current signal corresponding to the lost energy is detected. However, the neutron detector may count the number of generated protons. Measurement is possible for the reason described below. When a scintillator is used as a neutron detector, it emits once every time a proton enters. The number can be measured by converting the light into an electrical signal using a photomultiplier tube or the like. Even when a semiconductor detector is used, a single pulsed voltage can be measured by passing a preamplifier and an amplifier when a single proton is incident. The number of protons can be measured by measuring the number of voltage pulses. The detection rate of thermal neutrons is obtained based on the number of protons measured. Also in this case, based on the thermal neutron detection rate, the position where the water 14 exists and the amount of the water 14 can be obtained as described above. The measurement of the number of protons can measure the thermal neutron detection rate with higher accuracy than when measuring the current signal, and more accurately determine the position of the water 14 and the amount of the water 14 in the heat insulating material 12. Can do. When measuring the number of protons, the multi-channel wave height analyzer 8 is unnecessary, and the output of the amplifier 7 may be directly input to the data processing device 9. For this reason, the structure of a piping inspection apparatus can be simplified rather than the structure of FIG.

A pipe inspection apparatus according to embodiment 2, which is another embodiment of the present invention, will be described with reference to FIG. The pipe inspection apparatus 15A of the present embodiment has the same configuration as that of the pipe inspection apparatus 15 of the first embodiment except that it includes four ³ He proportional counters, a preamplifier 6, an amplifier 7, and four multichannel wave height analyzers 8 each. The same. These ³ He proportional counter includes a pair of ³ He proportional counter 2A, and a pair of ³ He proportional counter 2B. The preamplifier 6, the amplifier 7 and the multichannel wave height analyzer 8 are connected to each other as in the first embodiment. Each preamplifier 6 are respectively connected to a pair of ³ He proportional counter 2A, and a pair of ³ He proportional counter 2B. Each multi-channel wave height analyzer 8 is connected to one data processing device 9. A power source 3 is connected to the neutron generator tube 1. A high voltage power supply 5 is connected to each of the four preamplifiers 6. In FIG. 5, the connection of the three preamplifiers 6 and the high-voltage power supply 5 is not shown because the drawing becomes complicated. The control device 4 outputs a first control command to the high-voltage power supply 3 and outputs a second control command to the four multichannel wave height analyzers 8.
The pair of ³ He proportional counters 2 </ b> A and the pair of ³ He proportional counters 2 </ b> B are arranged on both sides of the neutron generator 1 so as to be symmetric with respect to the axis of the neutron generator 1. The axis of each of the neutron generator tube 1 and the ³ He proportional counter tubes 2A and 2B faces the center of the pipe 11. Each of the pair of ³ He proportional counters 2 </ b> A and each of the pair of ³ He proportional counters ² </ b> B is located at a position equidistant from the liquid 10 in the pipe 11.

Based on the first control command, single energy fast neutrons 20 are irradiated from each neutron generating tube 2 to the metal cover 13. The fast neutrons are generated in a pulse shape at each time when the first control command is output. The generated thermal neutrons are incident on the corresponding ³ He proportional counter. The energy spectrum information of each proton obtained by each multichannel wave height analyzer 8 connected to each ³ He proportional counter is input to the data processor 9. The data processor 9 performs the same processing as that of the first embodiment based on the energy spectrum information of these protons, calculates the distribution information of the thermal neutron detection rate corresponding to each ³ He proportional counter, and FIG. The image information of A) and FIG. 2B is created. When the water 14 does not exist, the image information of FIG. 2 (A) and FIG. 2 (C) is created.

This embodiment, when the water 14 is unevenly distributed in the heat insulating member 12, the distance from the water 14 to ³ He proportional counter 2A and ³ He proportional counter 2B differs ³ is closer to the water 14 the He Proportional counters show higher thermal neutron detection rates. The data processing device 9 can determine the presence or absence of the water 14 in the heat insulating material 12 using the difference in the detection rate. When the water 14 exists uniformly in the heat insulating material 12, it is necessary to measure the detection rate of the thermal neutron 21 corresponding to the amount of the water 14 in advance. It becomes possible.
The present embodiment can also obtain the effects produced in the first embodiment.

A pipe inspection apparatus according to embodiment 3, which is another embodiment of the present invention, will be described with reference to FIG. The pipe inspection apparatus 15B of the present embodiment includes three sets of the neutron generating tube 1 and the pair of ³ He proportional counters 2 in the second embodiment. These three sets of neutron generators 1 and a pair of ³ He proportional counters 2 are arranged at intervals of 120 ° around the pipe 11 to be inspected, and are attached to an annular connector (moving body) 17 surrounding the pipe 11. It is done. A pair of ³ He proportional counters 2 are arranged on both sides of the neutron generator 1 so as to be symmetrical with respect to the axis of the neutron generator 1. The connector 17 is installed on the surface of the metal cover 13 and is movably attached to a guide rail (guide device) 28 surrounding the metal cover 13. The three sets of neutron generator 1 and the pair of ³ He proportional counters 2 rotate around the metal cover 13 by moving the connector 17 along the guide rail 28.

Pipe inspection apparatus 15B, similar to the pipe inspection apparatus 15A of the second embodiment includes a pre-amplifier 6, an amplifier 7 and a multi-channel pulse-height analyzer 8 every ³ He proportional counter 2. Six multi-channel wave height analyzers 8 are connected to one data processing device 9. A second control command from the control device 4 is input to each multi-channel wave height analyzer 8. Each axis of each neutron generator tube 1 and each ³ He proportional counter tube 2 faces the center of the pipe 11.

The connector 17 is rotated by a predetermined angle, and then held at that angle, and fast heat neutrons are irradiated to the heat insulating material 12 from each of the three neutron generating tubes 1. Thermal neutrons generated in the water 14 existing in the heat insulating material 12 and the liquid 10 in the pipe 11 are measured by each ³ He proportional counter 2.
When the measurement of thermal neutrons at a certain angle is completed, the connector 17 is rotated by a predetermined angle. In this way, measurement of thermal neutrons is performed over the entire region in the circumferential direction of the heat insulating material 12 while repeating the movement and holding of the neutron generating tube 1 and the ³ He proportional counter 2 around the metal cover 13 by a predetermined angle. Done. When the water 14 is unevenly distributed in the heat insulating material 12 in the circumferential direction of the pipe 11, the distance from the water 14 to the two ³ He proportional counters 2 located on both sides of the one neutron generator 1 is different. For this reason, the detection rate of thermal neutrons obtained from the output signal of the ³ He proportional counter 2 located near the water 14 among these ³ He proportional counters 2 is a large value. Therefore, it is not necessary to provide a plurality of pairs of ³ He proportional counters in one neutron generating tube 1 as in the second embodiment, and a pair of ³ He proportional counters 2 provided for one neutron generating tube 1 are piped. 11, the pipe inspection device 15 </ b> B can determine the presence or absence of the water 14 over the entire area in the circumferential direction of the heat insulating material 12.

The present embodiment can obtain the effects produced in the second embodiment, and can further reduce the number of ³ He proportional counters 2 per one neutron generating tube. Even if only one set of one neutron generator tube 1 and a pair of ³ He proportional counters 2 is provided instead of three, it takes an inspection time, but the heat insulating material 12 can be inspected in the entire circumferential direction. is there.

A pipe inspection apparatus according to embodiment 4 which is another embodiment of the present invention will be described with reference to FIG. Figure 7 shows only part of the neutron generating tube 1 and a pair of ³ He proportional counter 2 of the pipe inspection apparatus 15C of the present embodiment is omitted remaining structure of the pipe inspection system 15C . The configuration of the omitted portion is a configuration related to the neutron generating tube 1 and the pair of ³ He proportional counters 2 in FIG. In this embodiment, the axis of the neutron generator tube 1 is arranged toward the center of the pipe 11 and the axis extends in the horizontal direction. The axis of each of the pair of ³ He proportional counters 2 positioned on both sides of the neutron generator tube 2 is orthogonal to the axis of the pipe 11 when the pipe 11 is viewed from the ³ He proportional counter 2. Has been placed. In other words, the axial centers of the pair of ³ He proportional counters 2 are arranged substantially in parallel along one plane intersecting (orthogonal to) the axial center of the neutron generating tube 1. This embodiment are arranged in this way ³ He proportional counter tube 2, the area of the ³ He proportional counter 2 facing the heat insulator 12 is large, the thermal neutrons incident on ³ He proportional counter 2 Increases flight distance. Therefore, in this embodiment, the detection efficiency of the detection rate of the thermal neutrons generated from the water 14 is improved. This can further reduce the time required for measuring the water 14 present in the heat insulating material 12. The present embodiment can also obtain the effects produced in the first embodiment. Incidentally, in Examples 1, 2 and 3, the ³ He proportional counter 2 is arranged so that its axial center faces the radial direction of the pipe 11.

A pipe inspection apparatus according to embodiment 5 which is another embodiment of the present invention will be described with reference to FIG. Figure 8 shows only portions of the neutron generating tube 1 and a pair of ³ He proportional counter 2 of the pipe inspection apparatus 15D of the present embodiment is omitted remaining structure of the pipe inspection system 15D . The configuration of the omitted part is the same as that of the pipe inspection apparatus 15C of the fourth embodiment. Pipe inspection apparatus 15D includes a pair of ³ He proportional counter 2 of the pipe inspection apparatus 15C, the pipe 11 (specifically, the metal cover 13) does not face the portion fitted with a thermal neutron shielding material 18, the heat that portion The structure is covered with a neutron shielding material 18. The thermal neutron shielding material 18 is composed of thermal neutron absorbers such as gadolinium, cadmium, and haunium that have a high thermal neutron absorption rate.

In order to measure the thermal neutron detection rate corresponding to the amount of water 14 in advance, and to compare the thermal neutron detection rate measured in advance with the thermal neutron detection rate measured in the actual inspection of the pipe 11, neutron generation It is necessary to accurately measure the generation rate of fast neutrons in the tube 1. In order to measure the generation rate of fast neutrons in the neutron generator tube 1, the pipe inspection device 15 </ b> D has a fast neutron measurement device 24 </ b> A installed close to the neutron generator tube 1 as shown in FIG. 9. Fast neutron monitoring apparatus 24A is an outer surface of the ³ He proportional counter 2C is a neutron detector for measuring the thermal neutron enclosure neutron moderator 17, further outside of the neutron moderating material 17 surrounds a thermal neutron absorbing material 16 It is configured. The measurement of fast neutrons by the fast neutron measurement device 24A will be described. Fast neutrons 21 generated by the target 23 </ b> A provided in the neutron generating tube 1 are irradiated to the heat insulating material 12 and a part thereof is incident on the fast neutron measuring device 24. The fast neutrons becomes decelerated by thermal neutrons 21A neutron moderator 17, the thermal neutrons 21A is detected by the ³ He proportional counter 2C. Thermal neutrons than thermal neutrons 21A generated by deceleration by the neutron moderating material 17, is absorbed by the neutron absorber 16, it is not detected by the ³ He proportional counter 2C. Detection rate of thermal neutrons 21A detected by ³ He proportional counters. 2C, by fixing the installation position of the ³ He proportional counter 2C for neutron generating tube 1, the fast neutrons 20 generated by the neutron generator tube 1 occurs Proportional to rate. By measuring the rate of detection of thermal neutrons 21A with ³ He proportional counter 2C, it is possible to measure the relative values of the incidence of high-speed neutrons.

  Such a present Example can shield the thermal neutron which comes from other than the piping 11 side, and can further reduce the background of a thermal neutron. In the present embodiment, the effects produced in the fourth embodiment can be obtained.

  A moisture detection apparatus according to Embodiment 6 which is another embodiment of the present invention and a moisture detection method using the same will be described with reference to FIG. The moisture detection device 30 of the present embodiment has the same configuration as the pipe inspection device 15 of the first embodiment. The inspection object in the present embodiment is a distillation tower 31 of a chemical plant, and is installed outdoors.

A heat insulating material 12 is attached to the distillation column 31 so as to surround the distillation column 31. A metal cover 13 covers the outer surface of the heat insulating material 12. A liquid (for example, any one of heavy oil, light oil, kerosene, chemical substances, etc.) 10 flows in the distillation column 31. The neutron generator 1 and the ³ He proportional counter 2 face the surface of the metal cover 13, and their axial centers are arranged in the radial direction of the distillation column 31. It is assumed that the water 14 exists in the heat insulating material 12.

  The moisture detection device 30 functions in the same manner as the pipe inspection device 15 and detects the water 14 in the heat insulating material 12 surrounding the distillation tower 31. An outline of detection of the water 14 by the moisture detection device 30 will be described below.

  The neutron generating tube 1 generates fast neutrons 20 having a time width t in a pulse shape. The fast neutrons 20 emitted from the neutron generating tube 1 are the metal cover 13, the heat insulating material 12, the water 14 existing in the heat insulating material 12, the distillation tower 31, and the constituent elements and elasticity of the liquid 10 flowing in the distillation tower 31. By scattering, it loses energy and becomes a lower energy thermal neutron. The fast neutron 20 loses little energy depending on the metal cover 13, the heat insulating material 12 and the distillation column 31, and mainly loses energy due to the water 14 and the liquid 10 to become thermal neutrons.

Among the generated thermal neutrons, thermal neutrons flying in the direction opposite to the irradiation direction of the fast neutrons 20 are detected by the ³ He proportional counter 2. The current signal output from the ³ He proportional counter 2 by the detection of thermal neutrons is converted into a voltage signal when passing through the preamplifier 6 and the amplifier 7, and is input to the multichannel wave height analyzer 8. The multi-channel wave height analyzer 8 analyzes the height of the voltage signal and obtains the energy spectrum of protons generated by the nuclear reaction as described above. This energy spectrum information is input from the multichannel wave height analyzer 8 to the data processor 9.

  Based on the input fast neutron generation rate information and the calculated thermal neutron detection rate information (thermal neutron intensity information), the data processing device 9 uses the images shown in FIG. Information is created and this image information is output to the display device 16. Further, the data processing device 9 obtains the amount of the water 14 in the heat insulating material 12 and the position where the water 14 exists in the same manner as in the first embodiment. The obtained information on the amount of water 14 and the location of the water 14 is output to the display device 16 and displayed.

  In the present embodiment, the effects produced in the first embodiment can be obtained with the distillation column 31 as a target. By knowing the position where the water 14 exists, it is possible to know the position where the distillation column 31 is corroded or the position where corrosion is likely.

  Instead of the moisture detection device 30, any of the pipe inspection devices 15A, 15B, 15C, and 15D used in Examples 2 to 5 may be used as the moisture detection device. In addition, using any of the pipe inspection devices 15, 15A, 15B, 15C, and 15D as a moisture detection device, a distillation tower, a reaction tower, a reaction tank, an adsorption tower, a mixing tank, and the like that are inspection objects other than the distillation tower 31 The inspection of the towers and tanks and the tank, that is, the water in the heat insulating material surrounding these inspection objects can be detected in the same manner as the distillation tower 31.

It is a block diagram of the piping inspection apparatus of Example 1 which is one suitable Example of this invention. The distribution of the detection rate of thermal neutrons measured in Example 1 is shown, (A) is an explanatory view showing image information showing the generation rate of pulsed fast neutrons at each generation time, and (B) is a heat insulating material. FIG. 5C is an explanatory diagram of image information of thermal neutron detection rate in a state where water is present, and FIG. 8C is an explanatory diagram of image information of thermal neutron detection rate in a state where water is not present in the warm material. 1 is a configuration diagram of a fast neutron measurement apparatus used in Example 1. FIG. It is the characteristic figure which showed the fast neutron generation rate by the fusion reaction of deuterium and deuterium corresponding to an angle. It is a block diagram of the piping inspection apparatus of Example 2 which is another Example of this invention. It is a block diagram of the piping inspection apparatus of Example 3 which is another Example of this invention. A block diagram of another pipe inspection apparatus as in Example 4 is an embodiment of the present invention, (A) is when viewing the pipe from the ³ He proportional counter, a neutron generator tube and ³ He proportional counter Explanatory drawing which shows arrangement | positioning, and (B) are VV sectional drawings of (A). A block diagram of another pipe inspection apparatus of the fifth embodiment which is an embodiment of the present invention, (A) is when viewing the pipe from the ³ He proportional counter, a neutron generator tube and ³ He proportional counter Explanatory drawing which shows arrangement | positioning, and (B) are VI-VI sectional drawings of (A). It is a block diagram of the fast neutron measurement apparatus used with the piping inspection apparatus of Example 5. It is a block diagram of the moisture detection apparatus of Example 6 which is another Example of this invention.

Explanation of symbols

1 ... neutron generating tube, 2 ... ³ the He proportional counters (neutron detectors), 4 ... controller, 8 ... multichannel pulse-height analyzer, 9 ... data processing unit, 10 ... liquid, 11 ... pipe, 12 ... heat insulating material , 13 ... Metal cover, 14 ... Water, 15, 15A, 15B, 15C, 15D ... Pipe inspection device, 16 ... Display device, 17 ... Connector, 18 ... Neutron moderator, 19 ... Charged particle detector, 20 ... High speed Neutron, 21, 21A ... thermal neutron, 23, 23A ... target, 24, 24A ... fast neutron measuring device, 26 ... proton, 30 ... moisture detector, 31 ... distillation tower.

Claims (24)

  Pulsed fast neutrons having a single energy are irradiated to a heat insulating material provided around the object to be inspected, and the fast neutrons are generated. The direction of irradiation of the fast neutrons is opposite. The thermal neutron traveling in the direction is detected, and based on the detection signal of the thermal neutron, the time change of the intensity of the detected thermal neutron based on the generation time of the pulsed fast neutron is calculated and obtained. A water detection method characterized in that a position of water in the heat insulating material is obtained based on the information of the time change.   The moisture detection method according to claim 1, wherein the inspection object is any one of a tower, a tank, a tank, and a pipe in which a liquid exists. A neutron generator that generates pulsed fast neutrons having a single energy, and irradiates the thermal insulation provided around the object to be inspected with the fast neutrons, and is generated by the fast neutrons. Based on the output of the neutron injector and the neutron injector that detects the thermal neutron by injecting thermal neutrons traveling in the direction opposite to the fast neutron irradiation direction, the generation time of the pulsed fast neutrons is determined. A data processing device that calculates a temporal change in the intensity of the thermal neutron detected by the neutron injector, and obtains a position of water in the heat insulating material based on the obtained information on the temporal change, A moisture detection device characterized by that.   The moisture detection device according to claim 3, wherein the data processing device obtains an amount of water in the heat insulating material based on the information on the time change. Moisture detector according to claim 3 or claim 4 wherein the neutron beam injector forming a pair are arranged to be symmetrical with respect to the axis of the neutron generator.   The moisture detection device according to claim 5, further comprising: a guide device disposed around the inspection object; and a moving body to which the neutron generation device and the neutron injection device are attached and move along the guide device. . The axis of each of a pair of said neutron injection device located in the both sides of the said neutron generator is arrange | positioned substantially parallel along the surface orthogonal to the axis of the said neutron generator. The moisture detection device according to claim 6. The moisture detection according to any one of claims 3 to 6, wherein respective axes of the pair of neutron injectors located on both sides of the neutron generator are arranged along a radial direction of the pipe. apparatus. The moisture detection device according to any one of claims 3 to 6 , wherein a surface of the neutron injection device other than a surface facing the inspection object is covered with a thermal neutron shielding material . The moisture detection device according to any one of claims 3 to 9 , further comprising the neutron generation device that generates the fast neutrons by a fusion reaction between deuterium and tritium and deuterium . The moisture detection apparatus according to any one of claims 3 to 6, comprising a fast neutron measurement apparatus. The moisture detection according to claim 11 , wherein the fast neutron measurement device includes a thermal neutron detection device, a neutron moderating member that covers the periphery of the thermal neutron detection device, and a thermal neutron absorber that covers the periphery of the neutron moderation member. apparatus. A charge generated when fast neutrons are generated in the neutron generator, the neutron generator comprising the neutron generator that generates the fast neutrons by a fusion reaction of deuterium with either deuterium or tritium a charged particle detector for detecting particles, and the charged particle detector on the basis of the counting rate of the charged particles detected by the fast neutron claim contains other data processing device which calculates the incidence of 1 1 The moisture detection apparatus according to 1. A neutron generator for generating pulsed fast neutrons having a single energy and irradiating the heat insulating material provided around the pipe with the fast neutrons, and the irradiation direction of the fast neutrons generated by the fast neutrons A neutron injector that detects thermal neutrons that travel in the opposite direction and detects the thermal neutrons, and the neutron injector that is based on the generation time of the pulsed fast neutrons based on the output of the neutron injector And a data processing device for calculating a time change in the intensity of the thermal neutrons detected in the step and obtaining a position of water in the heat insulating material based on the obtained information on the time change. Equipment . The piping inspection device according to claim 14, wherein the data processing device obtains an amount of water in the heat insulating material based on the information on the time change . The pipe inspection apparatus according to claim 14 or 15 , wherein the paired neutron injection devices are arranged so as to be symmetric with respect to an axis of the neutron generation device. The pipe inspection apparatus according to claim 16 , further comprising: a guide apparatus disposed around the pipe; and a moving body to which the neutron generation apparatus and the neutron injection apparatus are attached and move along the guide apparatus. A pair of said each of the claims axis is arranged substantially parallel along a plane orthogonal to the axis of the neutron generator section neutron injection device 1 4 positioned on both sides of the neutron generator The piping inspection device according to any one of claims 17 to 17 . Piping according to each of the axis is any one of claims 13 to 1 7 are arranged along the radial direction of the pipe of the pair of the neutron injection device positioned on both sides of the neutron generator Inspection device. The pipe inspection apparatus according to any one of claims 14 to 17 , wherein a surface of a part other than the surface facing the pipe of the neutron injection apparatus is covered with a thermal neutron shielding material . The pipe inspection apparatus according to any one of claims 14 to 20 , further comprising the neutron generation apparatus that generates the fast neutrons by a fusion reaction between deuterium and tritium and deuterium . Pipe inspection apparatus according to any one of claims 1 4 to claims 1 to 7 having a fast neutron measuring apparatus. The pipe inspection according to claim 22 , wherein the fast neutron measurement device includes a thermal neutron detection device, a neutron moderating member that covers the periphery of the thermal neutron detection device, and a thermal neutron absorber that covers the periphery of the neutron moderation member. apparatus. A charge generated when fast neutrons are generated in the neutron generator, the neutron generator comprising the neutron generator that generates the fast neutrons by a fusion reaction of deuterium with either deuterium or tritium a charged particle detector for detecting particles, and on the basis of the counting rate of the charged particle detected by the charged particle detector, to claim 22 which contains other data processing device which calculates the incidence of the fast neutron The piping inspection device described.

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