CN109540938B - Device and method for measuring steam content of cross section of steam generator tube bundle area - Google Patents
Device and method for measuring steam content of cross section of steam generator tube bundle area Download PDFInfo
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- CN109540938B CN109540938B CN201910034334.3A CN201910034334A CN109540938B CN 109540938 B CN109540938 B CN 109540938B CN 201910034334 A CN201910034334 A CN 201910034334A CN 109540938 B CN109540938 B CN 109540938B
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Abstract
A device and a method for measuring the steam content of the section of a tube bundle area of a steam generator comprise a gamma ray transmitting and receiving device, a gamma ray scanning mobile measuring platform, a stepping motor driving and controlling system and a ray counting rate collecting system. The method can continuously obtain the section steam content of any chord length between the secondary side tube bundles of the steam generator by a gamma ray scanning method, and corrects a calculation formula by considering the structural parameters and the flow parameters of the steam generator, thereby accurately distinguishing the fluid with a complicated tube bundle geometry and the fluid with different primary and secondary sides and solving the measurement problem of the section steam content of the secondary side tube bundles of the steam generator.
Description
Technical Field
The invention relates to the technical field of two-phase flow measurement and reactor thermal hydraulic power, in particular to a device and a method for measuring the steam content of the section of a tube bundle area of a steam generator.
Background
The steam generator is used as a device for exchanging heat of a primary side and a secondary side of the nuclear power plant, has a crucial position in the whole nuclear power system, and the working performance and the reliability of the steam generator are directly related to the stable operation of the whole nuclear power plant. Damage to the heat transfer tubes of the steam generator due to vibration, corrosion, thermal fatigue, and the like, has a significant impact on the safety and reliability of the nuclear power plant. Therefore, the research on the two-phase flow boiling heat transfer and flow characteristics between the secondary side heat transfer tube bundles of the steam generator has important significance.
The section vapor content (also called void fraction) of the two-phase flow is an extremely important parameter in the research of the two-phase flow, accurate data cannot be obtained through theoretical calculation, and experimental measurement is the only reliable way for obtaining the section vapor content. Due to the diversity of the flow pattern and the complexity of the flow of the vapor-liquid two-phase flow, the measurement of the vapor content of the cross section is always a difficult point of the two-phase flow measurement technology. In a narrow slit channel of a tube bundle at the secondary side of the steam generator, along with boiling heat exchange under the condition of high temperature and high pressure, the measurement of the steam content of the cross section is difficult.
For a long time, scholars at home and abroad make a great deal of research work on the measurement technology of the steam content of the two-phase flow section, and the main measurement methods comprise a quick-closing valve method, a high-speed camera method, a differential pressure method, a capacitance method, a light guide/electric conduction probe method, a ray method and the like. These methods for measuring the steam content of the cross section have been successful to some extent, but have also been inevitably limited to the respective methods.
Both the quick-closing valve method and the high-speed camera shooting method have high measurement accuracy, but the quick-closing valve method needs to cut off fluid and is difficult to measure in real time; the high-speed camera shooting method needs the visualization of a test section and has large workload of image processing in the later period. The two methods are generally applied to experimental research, most of working media are air-water two-phase flow under normal pressure, and in engineering application, particularly in a high-temperature high-pressure tube bundle narrow slit channel of a steam generator, real-time measurement cannot be realized.
The differential pressure method is a simple method for measuring the steam content of a section, in a vertically ascending gas-liquid two-phase flow, the total pressure drop consists of three parts of friction pressure drop, weight pressure drop and acceleration pressure drop, and under a homogeneous model, the steam content of the section can be deduced from the weight pressure drop, so that the accurate weight pressure drop of the two-phase flow needs to be obtained. However, under the condition of secondary side saturation boiling between tube bundles, the ratio of friction pressure drop to accelerated pressure drop is difficult to evaluate, so that the steam rate of the obtained section has great uncertainty.
The capacitance method regards the electrodes arranged on the two-phase flow pipeline as a capacitor, the capacitance value of the capacitor is related to the dielectric constant of a two-phase mixture, and the dielectric constant of the two-phase mixture is related to the dielectric constant of each phase separation and the steam content of the cross section, so that the steam content of the cross section can be obtained by measuring the capacitance value between the two electrodes. The capacitance method is influenced by the flow pattern of the two-phase flow, and different test conditions need a targeted sensor structure; the capacitance method is also susceptible to parameters such as water quality and temperature, so that the measurement method has a plurality of difficulties in measuring the steam content of the cross section between the narrow slits of the tube bundle in the steam generator.
The optical guide/electric conduction probe method is a method for measuring two-phase flow local parameters, can obtain important two-phase flow parameters of accurate local vapor content, bubble speed, bubble size, interface area concentration and the like, has high signal transmission speed and sampling frequency, and has wide application prospect. However, the probe method is an intrusive measurement mode, and inevitably generates interference to a flow field; the local vapor fraction obtained by the probe method is difficult to be related with the cross-sectional vapor fraction, especially for complex flow cross-sections such as tube bundle channels.
The ray method is one of the commonly used methods for measuring the steam content of a cross section, and mainly comprises gamma rays, X rays, neutron rays and the like. The ray method is a non-contact measurement mode, and has high stability because the ray attenuation is not interfered by external conditions, thus being suitable for measuring the vapor content of the section of the vapor-liquid two-phase flow under the conditions of high temperature and high pressure. The ray source is not in direct contact with fluid or even the pipe wall, so that the ray source can be conveniently moved to realize measurement at different positions. The traditional ray measurement method is limited to a round pipe, and the influence of a complex structure in the pipe is not considered. In addition, the operation of the radiation is dangerous, and certain protection needs to be performed on the radiation to ensure the safety of personnel.
Based on the above review of the conventional section vapor content measurement method, each method has its advantages, but the method has limitations. In the steam generator, high-pressure supercooled water is arranged on the primary side, high-pressure saturated steam-water two-phase flow is arranged on the secondary side, and vigorous heat transfer exists between the primary side and the secondary side. In order to measure the steam content of the cross section in the narrow slit channel of the secondary side tube bundle, the following difficulties need to be overcome:
(1) extreme environments of high temperature and high pressure boiling heat transfer;
(2) the narrow slit passage is narrow, so that the interference to a flow field is avoided as much as possible;
(3) complex geometries of the tube bundle zone can be identified;
(4) it is possible to distinguish between fluids that are treated differently on the primary and secondary sides.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a device and a method for measuring the steam content of the section of the tube bundle area of the steam generator, which overcome the defects of the traditional section steam content measuring method, can accurately obtain the section steam content in the narrow slit channel of the secondary side tube bundle, and has important significance for researching the flow and heat transfer of the secondary side two-phase flow of the steam generator.
In order to achieve the purpose, the invention adopts the technical scheme that:
an apparatus for steam generator tube bundle section vapor fraction measurement, comprising: the device comprises a gamma ray transmitting and receiving device, a gamma ray scanning mobile measuring platform, a stepping motor driving and controlling system and a ray counting rate collecting system, wherein the stepping motor is connected with the mobile measuring platform to drive the mobile measuring platform and drive the gamma ray transmitting and receiving device arranged on the mobile measuring platform to complete measurement of vacuole share by a gamma ray scanning method, and the ray counting rate collecting system completes data collection;
the gamma ray emitting and receiving device comprises137The Cs-emitting source 1 is,137the Cs radioactive source 1 is positioned inside the shielding lead tank 2, and137the Cs radioactive source 1 is correspondingly provided with a collimator 13 and a scintillation crystal detector 14;
the gamma ray scanning mobile measuring platform comprises a stepping motor driving device and a mobile support, the stepping motor driving device comprises a stepping motor mobile platform 4 and a mobile sliding table 6, a guide rail 5 is arranged on the stepping motor mobile platform 4, and a stepping motor 3 provides power for the stepping motor mobile platform 4;
the movable support comprises a radiation source side movable support 10 and a receiver side movable support 12, and the radiation source side movable support 10 is connected with the receiver side movable support 12 through a connecting rod device 11;
a steam generator cylinder 17 is arranged between the source side moving bracket 10 and the receiver side moving bracket 12;
the stepping motor driving and controlling system comprises a driver 8, wherein the driver 8 is connected with the stepping motor 3, a controller 7 is connected with the driver 8, and the controller 7 and the driver 8 are respectively connected with a 24V direct-current power supply 9;
the ray counting rate acquisition system comprises a ray collector 15, an industrial personal computer 16, an acquisition program and connecting wires among all devices; the ray collector 15 is connected with the scintillation crystal detector 14, and the ray collector 15 is connected with the industrial personal computer 16;
the movable support 10 at the radiation source side is fixedly connected with the movable sliding table 6, so that the scanning function of driving the movable support by the stepping motor driving device is realized;137cs radiation source 1And the shielding lead tank 2 is fixed on the radiation source side moving support 10, and the collimator 13 and the scintillation crystal detector 14 are fixed on the receiver side moving support 12.
A steam generator heat transfer tube bundle 18 is arranged in the steam generator cylinder 17.
Said137The Cs radioactive source 1, the central aperture of the collimator 13 and the center of the receiving plane of the scintillation crystal detector 14 are positioned on the same straight line
A method for measuring the steam content of the section of a tube bundle area of a steam generator comprises the following steps;
(1) selecting a proper measuring section, and arranging a gamma ray transmitting and receiving device, a gamma ray scanning mobile measuring platform, a stepping motor driving and controlling system and a ray counting rate collecting system according to the technical scheme;
(2) calibrating a gamma ray scanning mobile measuring platform and setting scanning parameters;
(3) calibrating a gas phase background and a liquid phase background;
(4) scanning and measuring the vapor content of the gas-liquid two-phase flow section on a cross section;
(5) and calculating the steam content of the section of the secondary side tube bundle area of the steam generator according to the measured gas phase background, liquid phase background, the ray counting rate of the gas-liquid two-phase flow, the flow parameters and the structural parameters of the steam generator.
The specific steps are as follows;
firstly, calibrating a gamma ray scanning mobile measuring platform and setting scanning parameters:
(1) selecting a proper measuring section, and arranging a gamma ray scanning mobile measuring platform, a stepping motor driving and controlling system and a ray counting rate acquisition system according to the technical scheme;
(2) adjusting the test platform to ensure that the moving direction of the ray is vertical to the narrow slit direction of the tube bundle to be tested and ensure that the moving measurement plane is vertical to the axial direction of the tube bundle;
(3) arrangement of137The Cs radioactive source 1 and the scintillation crystal detector 14 select a proper collimator 13 according to the size of the narrow slit gap between the tube bundles and arrange the collimator on the scintillation crystalBefore the detector 14, the emission direction of the center of the radioactive source, the central aperture of the collimator 13 and the center of the receiving plane of the scintillation crystal detector 14 are ensured to be on the same straight line;
(4) setting a program of a stepping motor 3 on a stepping motor driver, and determining the scanning length and the advancing speed;
secondly, the calibration process of the gas phase background and the liquid phase background is as follows:
(5) filling the primary side of the steam generator with liquid and the secondary side of the steam generator with air, and measuring the temperature and the pressure of the primary side and the secondary side (used for determining the density of the medium); opening the radioactive source and the ray receiving device, driving the stepping motor 3 according to a preset program, carrying out scanning measurement on the steam generator, and recording the counting rate of the gas phase background; in order to improve the measurement precision, the positive and negative scanning measurement is carried out, the radioactive source returns to the initial position, and the radioactive source is closed after the collection is finished;
(6) filling the primary side of the steam generator with liquid, filling the secondary side of the steam generator with liquid, and measuring the temperature and pressure of the primary side and the secondary side (used for determining the density of the medium); opening the radioactive source and the ray receiving device, driving the stepping motor 3 according to a preset program, carrying out scanning measurement on the steam generator, and recording the liquid phase background counting rate; in order to improve the measurement precision, the positive and negative scanning measurement is carried out, the radioactive source returns to the initial position, and the radioactive source is closed after the collection is finished;
and finally, collecting the secondary side gas-liquid two-phase flow counting rate of the steam generator:
(7) measuring the temperature and pressure of the primary side and the secondary side (for determining the density of the medium) when the stable heat transfer process is achieved between the steam generator tube bundles; opening the radioactive source and the ray receiving device, driving the stepping motor according to a preset program, carrying out scanning measurement on the steam generator, and recording the counting rate of the gas-liquid two-phase flow; in order to improve the measurement precision, the positive and negative scanning measurement is carried out, the radioactive source returns to the initial position, and the radioactive source is closed after the collection is finished;
(8) and repeating the steps, and measuring the next working condition point until the two-phase counting rate acquisition of all the working conditions is completed.
The cross section vapor content calculation formula is as follows:
wherein C isiFor a correction factor, the correction factor is 0 for the case where the ray passes only through the secondary side of the steam generator; for the case where the ray passes through both the secondary and primary sides, the correction factor is:
the invention has the beneficial effects that:
the invention adopts a gamma ray scanning method to measure the steam content of the section of the secondary side tube bundle area of the steam generator, and has the following innovations:
(1) the advantages of gamma rays are fully utilized, the device can stably work in a high-temperature and high-pressure environment, and the interference to two-phase fluid is avoided;
(2) a stepping motor driving platform is built, so that the movement of the radioactive source and the receiver is accurately controlled, and the measurement precision is improved;
(3) the structural parameters and the flow parameters of the steam generator are considered, and a correction factor for calculating the steam content of the cross section is provided, so that the fluids with complicated tube bundle geometric structures and different primary and secondary sides are accurately distinguished.
The embodiment of the invention optimizes the traditional method for measuring the steam content of the section by using the gamma ray and solves the measurement problem of the steam content of the section between the secondary side tube bundles of the steam generator. By adopting the method, the section steam-containing rate on any chord length between the secondary side tube bundles of the steam generator can be obtained, and the average steam-containing rate of the whole section can be calculated through area weighting. The method has important significance for researching the flow and heat transfer of the secondary side two-phase flow of the steam generator.
According to the technical scheme for measuring the steam content of the section of the tube bundle area of the steam generator, the two-phase counting rate of the specific section can be obtained through ray scanning, and the attenuation of rays is not interfered by the outside, so that the steam generator can stably run under the conditions of high temperature and high pressure without contacting with fluid, and the influence on a two-phase flow field is avoided.
When the steam content of the cross section is calculated, the structural parameters arranged in the steam generator tube are considered, so that the complex geometric structure of the tube bundle area can be distinguished; the different fluids on the primary side and the secondary side can be distinguished by considering the thermal fluid parameters of the primary side and the secondary side in the steam generator.
Drawings
FIG. 1 is a schematic diagram of a gamma ray scanning mobile measurement structure according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a cross-section of a secondary side of a tube bundle region of a gamma ray scanning steam generator according to an embodiment of the present invention;
fig. 3 is an illustration of two exemplary cases of gamma rays passing through a steam generator according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
The embodiment of the invention provides a method and an experimental device for measuring the steam content of a section of a tube bundle area of a steam generator, and fig. 1 is a schematic diagram of a gamma ray scanning mobile measurement structure, which is used for describing a gamma ray transmitting, receiving and data collecting system and a driving and control system of a scanning mobile measurement platform. Mainly comprises137The device comprises a Cs radioactive source 1, a shielding lead tank 2, a stepping motor 3, a stepping motor moving platform 4, a guide rail 5, a moving sliding table 6, a controller 7, a driver 8, a 24V direct-current power supply 9, a radioactive source side moving support 10, a connecting rod device 11, a receiver side moving support 12, a collimator 13, a scintillation crystal detector 14, a ray collector 15, an industrial personal computer 16, a steam generator barrel 17 and a steam generator heat transfer tube bundle 18.
The steam generator cylinder 17 to be tested is arranged in the middle; a stepping motor 3, a stepping motor moving platform 4, a guide rail 5 and a moving sliding table 6 are arranged on one side to form a stepping motor driving device; fixing a radiation source side moving support 10 and a moving sliding table 6, and connecting the radiation source side moving support with a receiver side moving support 12 through a connecting rod device 11 to form a moving support; the step motor driving device and the movable support jointly form gamma ray scanning mobile measurementA platform; the driver 8 is connected with the stepping motor 3, the controller 7 is connected with the driver 8, and the controller 7 and the driver 8 are respectively connected with the 24V direct current power supply 9 to form a stepping motor driving and controlling system; on a moving support137The device comprises a Cs radioactive source 1, a shielding lead tank 2, a collimator 13 and a scintillation crystal detector 14, which form a gamma ray transmitting and receiving device; the scintillation crystal detector 14, the ray collector 15 and the industrial personal computer 16 are connected in sequence to form a ray counting rate collecting system.
The operation process of measuring the steam content of the cross section of the tube bundle area of the steam generator by using a gamma ray scanning method comprises the following steps:
firstly, calibrating a gamma ray scanning mobile measuring platform and setting scanning parameters:
(1) selecting a proper measuring section, and arranging a gamma ray scanning mobile measuring platform, a stepping motor driving and controlling system and a ray counting rate acquisition system according to the technical scheme;
(2) adjusting the test platform to ensure that the moving direction of the ray is vertical to the narrow slit direction of the tube bundle to be tested and ensure that the moving measurement plane is vertical to the axial direction of the tube bundle;
(3) arrangement of137The system comprises a Cs radioactive source and a scintillation crystal detector, wherein a proper collimator is selected according to the size of a narrow slit gap between tube bundles, and the Cs radioactive source and the scintillation crystal detector are arranged in front of the scintillation crystal detector, so that the central emission direction of the radioactive source, the central aperture of the collimator and the center of a receiving plane of the scintillation crystal detector are on the same straight line;
(4) and setting a stepping motor program on a stepping motor driver, and determining the scanning length and the traveling speed.
Secondly, the calibration process of the gas phase background and the liquid phase background is as follows:
(5) filling the primary side of the steam generator with liquid and the secondary side of the steam generator with air, and measuring the temperature and the pressure of the primary side and the secondary side (used for determining the density of the medium); opening the radioactive source and the ray receiving device, driving a stepping motor according to a preset program, carrying out scanning measurement on the steam generator, and recording the counting rate of the gas phase background; in order to improve the measurement precision, the positive and negative scanning measurement is carried out, the radioactive source returns to the initial position, and the radioactive source is closed after the collection is finished;
(6) filling the primary side of the steam generator with liquid, filling the secondary side of the steam generator with liquid, and measuring the temperature and pressure of the primary side and the secondary side (used for determining the density of the medium); opening the radioactive source and the ray receiving device, driving a stepping motor according to a preset program, carrying out scanning measurement on the steam generator, and recording the liquid phase background counting rate; in order to improve the measurement precision, the positive and negative scanning measurement is carried out, the radioactive source returns to the initial position, and the radioactive source is closed after the collection is finished;
and finally, collecting the secondary side gas-liquid two-phase flow counting rate of the steam generator:
(7) measuring the temperature and pressure of the primary side and the secondary side (for determining the density of the medium) when the stable heat transfer process is achieved between the steam generator tube bundles; opening the radioactive source and the ray receiving device, driving the stepping motor according to a preset program, carrying out scanning measurement on the steam generator, and recording the counting rate of the gas-liquid two-phase flow; in order to improve the measurement precision, the positive and negative scanning measurement is carried out, the radioactive source returns to the initial position, and the radioactive source is closed after the collection is finished;
(8) and repeating the steps, and measuring the next working condition point until the two-phase counting rate acquisition of all the working conditions is completed.
In order to further obtain the vapor content of the gas-liquid two-phase flow cross section between the narrow slits of the tube bundle, the calculation formula is explained in detail according to the measured gas phase background, liquid phase background, ray counting rate of the gas-liquid two-phase flow, and flow parameters and structural parameters of the steam generator with reference to fig. 2 and 3.
FIG. 2 is a schematic view of a ray scanning method for measuring the vapor content of a cross section of a vapor generator, wherein a uniform gamma ray emitted by a radioactive source is shielded by a shielding lead tank, then passes through the vapor generator in a sector shape, and is received by a scintillation crystal detector after being shielded again by a collimator. Assuming that the collimator is thick enough to shield the emitted gamma rays, the scintillation crystal detector can only receive radiation over an area of the inner diameter of the collimator, i.e., the effective radiation that is swept across the steam generator is an elongated cylinder having a diameter equal to the inner diameter of the collimator.
In the process of scanning the steam generator along the measuring section, there are two typical situations, as shown in fig. 3, the left side is that the ray only passes through the narrow slit between the tube bundles, i.e. only passes through the secondary side fluid and does not pass through the primary side fluid; to the right are the rays that will pass through the tube bundle, i.e., through both the secondary and primary side fluids.
The basic law of ray attenuation, lambert-beer law, is:
I＝I0exp(-μx)
I0-initial intensity or count rate of gamma rays;
i-intensity or count rate after attenuation of the permeating substance;
μ -linear absorption coefficient of matter for gamma rays;
x-ray is the distance, mm, traveled by the transmission medium.
Lambert-beer law can also be expressed as:
I＝I0exp(-(μ/ρ)ρx)
mu/rho-the mass absorption coefficient of a substance for gamma rays, i.e. the ratio of the linear absorption coefficient to the density of the substance.
The mass absorption coefficient is not influenced by the density and physical state of the substance, and is the same for water and water vapor under different conditions.
For the case that the ray only passes through the tube bundle gap, under the condition of gas phase background calibration, the following conditions are provided:
Iair＝I0exp(-(μ/ρ)mρmxm-(μ/ρ)airρairx)
Iair-the count rate received by the radiation receiver in full-gas conditions;
(μ/ρ)m-mass absorption coefficient of stainless steel;
ρm-density of stainless steel sleeve;
xm-thickness of the stainless steel sleeve;
(μ/ρ)air-the mass absorption coefficient of air;
ρair-density of air at normal temperature and pressure;
the x-ray penetrates through the thickness of the secondary side in the steam generator sleeve;
under the condition of liquid phase background calibration:
Iwater＝I0exp(-(μ/ρ)mρmxm-(μ/ρ)waterρwaterx)
Iwater-the count rate received by the ray receiver in full water conditions;
(μ/ρ)water-the mass absorption coefficient of water and water vapour;
ρwater-density of normal temperature and pressure water;
under the two-phase test conditions:
Itp＝I0exp(-(μ/ρ)mρmxm-(μ/ρ)waterρtpx)
Itp-the count rate received by the radiation receiver under biphasic test conditions;
ρtp-density of the secondary side two-phase steam-water mixture;
by formula transformation, neglecting the air density (which brings about an error of about 0.1%), the density of the two-phase steam-water mixture can be obtained:
according to the two-phase flow average density model, the following are provided:
ρtp＝ρsgα+(1-α)ρsl
ρsg-measuring the saturated vapour density under operating conditions;
ρsl-measuring the saturated liquid density under operating conditions;
so that the steam content alpha of the cross section can be obtained under the condition that the ray only passes through the slit of the tube bundleiFormula for calculation：
The steam content of the cross section measured by the above calculation formula is the case shown on the left side of fig. 3, and the corresponding area range is: the length is the chord length of the ray passing through the steam generator cylinder, and the width is the inner diameter of the collimator and takes the inner wall of the steam generator sleeve as a boundary.
For the condition that rays pass through a tube bundle gap and pass through primary side water of the tube bundle, the method comprises the following steps under the condition of gas phase background calibration:
Iair＝I0exp(-(μ/ρ)mρmxm-(μ/ρ)airρairx-(μ/ρ)waterρwaterxf)
xf-the thickness of the water on the primary side through which the radiation has penetrated;
under the condition of liquid phase background calibration:
Iwater＝I0exp(-(μ/ρ)mρmxm-(μ/ρ)waterρwaterx-(μ/ρ)waterρwaterxf)
under the two-phase test conditions:
Itp＝I0exp(-(μ/ρ)mρmxm-(μ/ρ)waterρtpx-(μ/ρ)waterρfhwaterxf)
ρfhwaterdensity of high temperature and high pressure water on the primary side.
By formula transformation, neglecting the air density (which brings about an error of about 0.1%), the density of the two-phase steam-water mixture can be obtained:
in contrast to the case where the ray passes through the bundle slit only, and not through the primary side water, the above formula contains a correction factor:
the correction factor is composed of two parts, one part is rhofhwater/ρwaterThe density ratio of water, namely the density ratio of the high-temperature and high-pressure water on the primary side during the two-phase test to the normal-temperature and normal-pressure water during calibration; another part is the structural coefficient xfAnd/x is the ratio of the thickness of the primary side water penetrated by the radiation to the thickness of the secondary side void penetrated by the radiation.
Considering that the portion of the radiation passing through the steam generator is an elongated cylinder and the radiation is uniformly distributed over its emission cross-section, the correction factor can be further expressed as:
Vf-the volume of water on the primary side penetrated by the radiation;
v-ray penetrates the volume of the secondary side steam-water two-phase flow.
Thereby obtaining the steam content alpha of the cross section under the condition that the ray passes through the slit of the tube bundle and the primary side water of the tube bundleiCalculating the formula:
the steam content of the cross section measured by the above calculation formula is the case shown on the right side of fig. 3, and the corresponding area range is: the length is the chord length of the ray passing through the steam generator cylinder, and the width is the inner diameter of the collimator and takes the inner wall of the steam generator sleeve and the outer wall of the heat transfer pipe as boundaries.
Thus, the section steam content alpha on any chord length of the outer secondary side of the tube bundle can be obtained by scanning the section of the steam generatoriThe average section vapor fraction alpha of the whole section can be calculated by the section vapor fraction on each chord length, and the calculation formula is as follows:
αi-section vapor fraction at the ith chord length;
Ai-the cross-sectional area corresponding to the ith chord length.
Claims (2)
1. A method for measuring the steam content of the section of a tube bundle area of a steam generator is characterized by comprising the following steps;
(1) selecting a proper measuring section, and arranging a gamma ray transmitting and receiving device, a gamma ray scanning mobile measuring platform, a stepping motor driving and controlling system and a ray counting rate collecting system;
(2) calibrating a gamma ray scanning mobile measuring platform and setting scanning parameters;
(3) calibrating a gas phase background and a liquid phase background;
(4) scanning and measuring the vapor content of the gas-liquid two-phase flow section on a cross section;
(5) calculating the steam content of the section of the secondary side tube bundle area of the steam generator according to the measured gas phase background, liquid phase background, the ray counting rate of the gas-liquid two-phase flow, and the flow parameters and the structural parameters of the steam generator;
the cross section vapor content calculation formula is as follows:
wherein C isiFor a correction factor, the correction factor is 0 for the case where the ray passes only through the secondary side of the steam generator; for the case where the ray passes through both the secondary and primary sides, the correction factor is:
the device in the step (1) is specifically as follows:
the device comprises a gamma ray transmitting and receiving device, a gamma ray scanning mobile measuring platform, a stepping motor driving and controlling system and a ray counting rate collecting system, wherein the stepping motor is connected with the mobile measuring platform to drive the mobile measuring platform and drive the gamma ray transmitting and receiving device arranged on the mobile measuring platform to complete measurement of vacuole share by a gamma ray scanning method, and the ray counting rate collecting system completes data collection;
the gamma ray emitting and receiving device comprises137A Cs radioactive source (1),137the Cs radioactive source (1) is positioned inside the shielding lead tank (2), and137the Cs radioactive source (1) is correspondingly provided with a collimator (13) and a scintillation crystal detector (14);
the gamma ray scanning mobile measuring platform comprises a stepping motor driving device and a mobile support, the stepping motor driving device comprises a stepping motor mobile platform (4) and a mobile sliding table (6), a guide rail (5) is arranged on the stepping motor mobile platform (4), and a stepping motor (3) provides power for the stepping motor mobile platform (4);
the movable support comprises a radiation source side movable support (10) and a receiver side movable support (12), and the radiation source side movable support (10) and the receiver side movable support (12) are connected through a connecting rod device (11);
a steam generator cylinder (17) is arranged between the source side moving bracket (10) and the receiver side moving bracket (12);
the stepping motor driving and controlling system comprises a driver (8), wherein the driver (8) is connected with the stepping motor (3), a controller (7) is connected with the driver (8), and the controller (7) and the driver (8) are respectively connected with a 24V direct-current power supply (9);
the ray counting rate acquisition system comprises a ray collector (15), an industrial personal computer (16), an acquisition program and connecting wires among the devices; the ray collector (15) is connected with the scintillation crystal detector (14), and the ray collector (15) is connected with the industrial personal computer (16);
the radiation source side moving support (10) is fixedly connected with the moving sliding table (6), so that the stepping motor driving device is driven to moveThe scanning function of the movable support;137a Cs radioactive source (1) and a shielding lead tank (2) are fixed on a movable support (10) at the radioactive source side, and a collimator (13) and a scintillation crystal detector (14) are fixed on a movable support (12) at the receiver side;
a steam generator heat transfer tube bundle (18) is arranged in the steam generator cylinder (17);
said137The Cs radioactive source (1), the central aperture of the collimator (13) and the center of the receiving plane of the scintillation crystal detector (14) are on the same straight line.
2. The method for steam generator tube bundle section vapor fraction measurement according to claim 1, characterized by the specific steps of;
firstly, calibrating a gamma ray scanning mobile measuring platform and setting scanning parameters:
(1) selecting a proper measuring section, and arranging a gamma ray scanning mobile measuring platform, a stepping motor driving and controlling system and a ray counting rate acquisition system according to the technical scheme;
(2) adjusting the test platform to ensure that the moving direction of the ray is vertical to the narrow slit direction of the tube bundle to be tested and ensure that the moving measurement plane is vertical to the axial direction of the tube bundle;
(3) arrangement of137The system comprises a Cs radioactive source (1) and a scintillation crystal detector (14), wherein a proper collimator (13) is selected according to the size of a narrow slit gap between tube bundles and is arranged in front of the scintillation crystal detector (14), and the central emission direction of the radioactive source, the central aperture of the collimator (13) and the center of a receiving plane of the scintillation crystal detector (14) are ensured to be on the same straight line;
(4) setting a program of a stepping motor (3) on a stepping motor driver, and determining the scanning length and the traveling speed;
secondly, the calibration process of the gas phase background and the liquid phase background is as follows:
(5) filling liquid into the primary side of the steam generator, filling air into the secondary side of the steam generator, and measuring the temperature and the pressure of the primary side and the secondary side; opening the radioactive source and the ray receiving device, driving a stepping motor (3) according to a preset program, scanning and measuring the steam generator, and recording the counting rate of the gas phase background; in order to improve the measurement precision, the positive and negative scanning measurement is carried out, the radioactive source returns to the initial position, and the radioactive source is closed after the collection is finished;
(6) filling liquid into the primary side and the secondary side of the steam generator, and measuring the temperature and the pressure of the primary side and the secondary side; opening the radioactive source and the ray receiving device, driving a stepping motor (3) according to a preset program, scanning and measuring the steam generator, and recording the liquid phase background counting rate; in order to improve the measurement precision, the positive and negative scanning measurement is carried out, the radioactive source returns to the initial position, and the radioactive source is closed after the collection is finished;
and finally, collecting the secondary side gas-liquid two-phase flow counting rate of the steam generator:
(7) measuring the temperature and pressure of the primary side and the secondary side when the stable heat transfer process is achieved between the steam generator tube bundles; opening the radioactive source and the ray receiving device, driving the stepping motor according to a preset program, carrying out scanning measurement on the steam generator, and recording the counting rate of the gas-liquid two-phase flow; in order to improve the measurement precision, the positive and negative scanning measurement is carried out, the radioactive source returns to the initial position, and the radioactive source is closed after the collection is finished;
(8) and repeating the steps, and measuring the next working condition point until the two-phase counting rate acquisition of all the working conditions is completed.
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