Device and method for measuring temperature of spent fuel pool of nuclear power station

Abstract

The invention discloses a device and a method for measuring the temperature of a spent fuel pool of a nuclear power station. The time measuring module is used for recording and calculating ultrasonic transmitting and receiving time information, the data processing module is used for processing acquired ultrasonic propagation distance and time information, and the data storage module is used for data storage. The temperature monitoring tentacle comprises a piezoelectric wafer electrically connected with the ultrasonic detector and a monitoring workpiece, the monitoring workpiece is provided with a first plane and a second plane, and at least part of the excitation and receiving range of the piezoelectric wafer covers the first plane and the second plane at the same time; and the first plane and the second plane form a step surface which is different from the piezoelectric wafer in spacing. The device is simple in structure, only one temperature monitoring tentacle is needed to complete temperature measurement, and if multiple points need to be measured at the same time, only the number of the tentacles needs to be increased correspondingly.

Description

Technical Field

[0001] The invention belongs to the field of nuclear power detection, and in particular relates to a device and method for measuring the temperature of a spent fuel pool in a nuclear power plant. Background Art

[0002] The spent fuel pool in a nuclear power plant is a facility used to store spent fuel. Its main purpose is to temporarily store highly radioactive spent fuel safely and effectively until its radioactivity level drops to a relatively safe level through natural decay so that it can be transported normally.

[0003] Spent fuel pools are usually located in fuel plants. Some nuclear power plants even place spent fuel pools and refueling pools inside containment. These pools contain boric acid water at a certain concentration. At the same time, the pools are equipped with cooling systems to remove the decay heat generated by the spent fuel.

[0004] Due to the residual heat of the fuel rods, the temperature of the water in the spent fuel pool is constantly changing, which has a great impact on the non-destructive testing of the fuel rods. For X-ray testing, changes in water temperature may affect the propagation characteristics of the rays. For example, changes in water density may affect the attenuation of the rays, thereby affecting the accuracy of the test results. For ultrasonic testing, the propagation speed of ultrasonic waves in water is affected by the water temperature. Changes in water temperature will cause changes in the propagation speed of ultrasonic waves, thereby affecting the test results. For eddy current testing, changes in water temperature will cause changes in the conductivity or dielectric constant of the water body, which will indirectly affect the accuracy of eddy current testing.

[0005] Therefore, the water temperature has a significant impact on the non-destructive testing methods in the spent fuel pool. In order to ensure the accuracy and reliability of the test results, it is necessary to fully consider the water temperature factor in the actual test process, so the measurement of the spent fuel pool temperature is particularly important.

[0006] At present, the mainstream temperature measurement method is to use a temperature gun for remote temperature measurement. The disadvantages of this method are very obvious. Due to the complex and changeable environment of the spent fuel pool, such as water surface fluctuations, steam, smoke, etc., they may interfere with the transmission of infrared radiation, thereby affecting the measurement accuracy of the temperature gun. At the same time, the temperature gun is mainly used to measure the temperature of the surface of the object, and the temperature distribution inside the water body cannot be directly measured. In addition, due to the residual heat of the fuel rods, the temperature of the water body in the spent fuel pool is constantly changing, which also has a certain impact on the accuracy of the temperature gun.

[0007] In addition to using temperature measuring guns, there are other technologies currently applied in this field. Patent CN104575640A discloses a spent fuel pool level and temperature measurement device, which is mainly composed of an RTD continuous level sensor, a differential thermocouple discrete level sensor and a thermocouple temperature sensor. The thermocouple temperature sensor can be used to measure the water temperature of the spent fuel pool, but the device cannot measure the temperature at any position and can only measure at a fixed point.

[0008] Patent CN207472386U discloses a spent fuel pool water level and temperature measurement system, which includes a mounting bracket, a laser rangefinder, an infrared thermometer, a catheter and a local display. The main temperature measurement method is to use an infrared thermometer, which is consistent with the principle of a temperature gun. The disadvantages are also due to the complex environment of the spent fuel pool, thermal disturbances, and the inability to measure deep water temperature.

[0009] Patent CN213932895U discloses a method that uses waveguide technology and special materials to enable ultrasonic temperature measurement devices to be used in strong oxidizing environments. However, due to the different media used, the time difference calculated by this method is different from the actual time difference of ultrasonic waves in a single medium, resulting in deviations in the calculation results. Moreover, this device is not suitable for the strong radiation environment of nuclear power plants.

[0010] In view of the shortcomings of the above patents, the present invention innovatively applies ultrasonic temperature measurement technology to the monitoring of the water temperature of the spent fuel pool. As a non-contact temperature monitoring method, this technology has been widely used in many fields in recent years. It is based on the specific relationship between the propagation speed of ultrasonic waves in the medium and the temperature of the medium, and calculates the temperature change by measuring the propagation speed of ultrasonic waves.

[0011] The core principle of ultrasonic temperature measurement technology is that ultrasonic waves are affected by the physical properties of the medium during propagation, among which temperature is an important factor. When the temperature of the medium changes, the thermal motion state of the molecules inside the medium will also change, which in turn affects the propagation speed of the ultrasonic wave. According to acoustic theory, the propagation speed of ultrasonic waves is closely related to parameters such as the density and elastic modulus of the medium, and these parameters have a certain functional relationship with temperature. Therefore, by measuring the propagation speed of ultrasonic waves, the temperature of the medium can be indirectly inferred.

[0012] Ultrasonic temperature measurement technology has its unique technical characteristics. It can achieve non-contact measurement. Ultrasonic temperature measurement technology does not need to be in direct contact with the object being measured, avoiding heat conduction errors caused by contact. It is also suitable for measurement in harsh environments such as high temperature and corrosive environments. It can be done in real time: This technology can quickly respond to temperature changes and achieve real-time and continuous temperature measurement, making it possible to monitor dynamic processes. It has strong penetration: Ultrasonic waves can penetrate solids, liquids and even gases to monitor internal temperature fields that are difficult to measure directly.

[0013] From the above technical characteristics, it is not difficult to find that ultrasonic temperature measurement technology has the following advantages compared with other temperature measurement technologies, including high precision: With the continuous development of technology, the accuracy of ultrasonic temperature measurement has been significantly improved, which can meet many high-precision temperature measurement needs. Wide range: Ultrasonic temperature measurement technology can cover a wide range from low temperature to high temperature, suitable for a variety of different application scenarios. Simple equipment and low cost: Compared with other temperature measurement technologies, ultrasonic temperature measurement equipment is usually simpler and relatively low in cost, which is easy to promote and apply.

[0014] At present, ultrasonic temperature measurement technology has been applied in many fields, and related theoretical research and manufacturing technology of measuring equipment have become more mature. At present, the application scenarios of ultrasonic temperature measurement technology are mostly ordinary environments, such as combustion chambers, boilers and other equipment. Although this technology has obvious advantages over other temperature measurement technologies, it is limited by development. At present, there are few related applications in harsh environments such as nuclear power plants. At the same time, most of the current ultrasonic temperature measurement equipment is in the form of dual probes, and the measurement process is cumbersome and complicated, and the equipment is also relatively complex. In the face of strong radiation environments such as spent fuel pools in nuclear power plants, the current ultrasonic temperature measurement equipment has disadvantages, and the measurement accuracy of the equipment will also be affected in this environment. Therefore, if you want to expand the application of ultrasonic temperature measurement technology to more severe and complex application scenarios, you need to further upgrade and transform the ultrasonic temperature measurement equipment. Summary of the invention

[0015] The purpose of the present invention is to provide a temperature measuring device for a spent fuel pool in a nuclear power plant, which can be placed at any position in the water body of the spent fuel pool to measure the water sound velocity at any point in the water body, thereby measuring the water body temperature by utilizing the relationship between the water sound velocity and the medium temperature.

[0016] In order to solve the above technical problems, the present invention adopts the following technical solution: a temperature measuring device for a spent fuel pool in a nuclear power plant, comprising:

[0017] An ultrasonic detector, comprising a time measurement module for recording and calculating ultrasonic emission and reception time information, a data processing module for processing the propagation distance and time information of the collected ultrasonic waves, and a data storage module for data storage;

[0018] The temperature monitoring tentacle comprises a piezoelectric chip electrically connected to the ultrasonic detector and a monitoring workpiece, wherein the monitoring workpiece is provided with a first plane and a second plane, the excitation and receiving ranges of the piezoelectric chip simultaneously cover the first plane and the second plane, and the first plane and the second plane form a step surface with a different spacing from the piezoelectric chip.

[0019] In another embodiment, the first plane and the second plane are parallel.

[0020] In another embodiment, a first through hole is opened on the monitoring workpiece, one of the side walls forming the first hole is the step surface, the side wall opposite to the step surface is the opposite side surface, the piezoelectric chip is arranged on the opposite side surface and the sending and receiving surfaces of the piezoelectric chip are arranged toward the step surface.

[0021] The present invention provides a measurement method based on the above-mentioned nuclear power plant spent fuel pool temperature measurement device, which comprises the following steps:

[0022] a. The ultrasonic detector controls the piezoelectric chip to emit ultrasonic waves in a harsh environment with strong radiation. The ultrasonic waves propagate through the water in the spent fuel pool. After a period of time, they propagate to the step surface of the step workpiece that is parallel to the piezoelectric chip. The step surface reflects the propagated ultrasonic waves. Due to the existence of the step surface, two echo signals with a time difference will be generated. The piezoelectric chip receives the reflected wave from the step surface, completing a detection;

[0023] b. By accurately measuring the propagation time of ultrasonic waves in the spent fuel pool, using the water sound speed calculation model, the propagation speed of sound waves in the water of the spent fuel pool, that is, the water sound speed, is calculated. The calculation formula is as follows: c = 2Δd / Δt,

[0024] Where Δd is the step spacing, c is the water sound speed, and Δt is the time difference between two echoes received by the piezoelectric chip.

[0025] c. Introduce the water sound velocity-temperature relationship model, design the temperature monitoring method of the spent fuel pool of the nuclear power plant, and calculate the water temperature.

[0026] In another embodiment, the water sound velocity calculation model can obtain the propagation speed of sound waves in the water of the spent fuel pool, and then by introducing the water sound velocity-temperature relationship model, the temperature of the water in the spent fuel pool can be calculated. The calculation formula is as follows: T = (ac) / b

[0027] Where T is the water temperature, a and b are two constants related to the properties of the liquid, and the constants can be determined according to the specific detection object.

[0028] The beneficial effects of the present invention are as follows: the device has a simple structure, and only one temperature monitoring tentacle is needed to complete the temperature measurement. If multiple points need to be measured simultaneously, only the number of tentacles needs to be increased accordingly; on the basis of the existing ultrasonic temperature measurement theory, a special ultrasonic temperature monitoring system and a special temperature monitoring tentacle are designed. The temperature monitoring tentacle is composed of a piezoelectric chip with radiation resistance and a step-type workpiece with a special structure, so as to complete the temperature monitoring in special application scenarios and solve the application problem of temperature monitoring of the water body in the spent fuel pool of a nuclear power plant; a method for calculating the temperature of the water body in the spent fuel pool under a strong irradiation environment is designed. On the premise of ensuring that the propagation medium is always consistent, the time difference between the two echo signals is accurately measured, and on this basis, a water sound speed calculation model is introduced to calculate the speed of sound wave propagation in the water body of the spent fuel pool, and then a water sound speed-temperature relationship model is introduced. Based on this model, the temperature of the water body in the spent fuel pool can be solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 System overall framework diagram;

[0030] Figure 2 Side view of the temperature monitoring tentacle;

[0031] Figure 3 Top view of the temperature monitoring tentacles;

[0032] Figure 4 Schematic diagram of ultrasonic temperature measurement. DETAILED DESCRIPTION

[0033] The present invention is described in detail below in conjunction with the embodiments shown in the accompanying drawings:

[0034] like Figure 2 As shown in / 3, the temperature measurement device of the spent fuel pool of a nuclear power plant includes: an ultrasonic detector and a temperature monitoring tentacle.

[0035] like Figure 1 As shown, the ultrasonic detector includes a time measurement module for recording and calculating the time information of ultrasonic emission and reception, a data processing module for processing the propagation distance and time information of the collected ultrasonic wave, and a data storage module for data storage;

[0036] The temperature monitoring tentacle includes a piezoelectric chip 1 electrically connected to the ultrasonic detector and a monitoring workpiece 2, wherein a first hole 20 is formed through the monitoring workpiece, one of the side walls forming the first hole is the step surface 23, and the side wall opposite to the step surface is the opposite side surface 24, and a first plane 21 and a second plane 22 with different spacings from the piezoelectric chip are formed on the step surface 23, the piezoelectric chip is arranged on the opposite side surface and the sending and receiving surfaces of the piezoelectric chip are arranged toward the step surface, and the excitation and receiving ranges of the piezoelectric chip cover the first plane 21 and the second plane 22 at the same time, and the first plane 21 and the second plane 22 are parallel.

[0037] The measuring method based on the above-mentioned nuclear power plant spent fuel pool temperature measuring device comprises the following steps:

[0038] a. The ultrasonic detector controls the piezoelectric chip to emit ultrasonic waves in a harsh environment with strong radiation. The ultrasonic waves propagate through the water in the spent fuel pool. After a period of time, they propagate to the step surface of the step workpiece that is parallel to the piezoelectric chip. The step surface reflects the propagated ultrasonic waves. Due to the existence of the step surface, two echo signals with a time difference will be generated. The piezoelectric chip receives the reflected wave from the step surface, completing a detection;

[0039] b. By accurately measuring the propagation time of ultrasonic waves in the spent fuel pool, using the water sound speed calculation model, the propagation speed of sound waves in the water of the spent fuel pool, that is, the water sound speed, is calculated. The calculation formula is as follows: c = 2Δd / Δt,

[0040] Where Δd is the step spacing, c is the water sound speed, and Δt is the time difference between two echoes received by the piezoelectric chip.

[0041] c. Introduce the water sound velocity-temperature relationship model, design the temperature monitoring method of the spent fuel pool of the nuclear power plant, and calculate the water temperature

[0042] The above water sound speed calculation model can obtain the propagation speed c of the sound wave in the water of the spent fuel pool. Then, by introducing the water sound speed-temperature relationship model, the water temperature of the spent fuel pool can be calculated. The calculation formula is as follows: T = (ac) / b, where T is the water temperature, a and b are two constants related to the properties of the liquid, and the constants can be determined according to the specific detection object.

[0043] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A temperature measuring device for a spent fuel pool in a nuclear power plant, characterized in that: It includes: An ultrasonic detector, comprising a time measurement module for recording and calculating ultrasonic emission and reception time information, a data processing module for processing the propagation distance and time information of the collected ultrasonic waves, and a data storage module for data storage; The temperature monitoring tentacle comprises a piezoelectric chip electrically connected to the ultrasonic detector and a monitoring workpiece, wherein the monitoring workpiece is provided with a first plane and a second plane, the excitation and receiving ranges of the piezoelectric chip simultaneously cover the first plane and the second plane, and the first plane and the second plane form a step surface with a different spacing from the piezoelectric chip.

2. The temperature measuring device for spent fuel pool in a nuclear power plant according to claim 1, characterized in that: The first plane and the second plane are parallel.

3. The temperature measuring device for spent fuel pool in a nuclear power plant according to claim 1, characterized in that: The monitoring workpiece is provided with a first through hole, one of the side walls forming the first hole is the step surface, the side wall opposite to the step surface is the opposite side surface, the piezoelectric chip is arranged on the opposite side surface and the sending and receiving surfaces of the piezoelectric chip are arranged toward the step surface.

4. A measurement method based on the temperature measurement device of a spent fuel pool in a nuclear power plant according to claim 1, characterized in that: It includes the following steps: a. The ultrasonic detector controls the piezoelectric chip to emit ultrasonic waves in a harsh environment with strong radiation. The ultrasonic waves propagate through the water in the spent fuel pool. After a period of time, they propagate to the step surface of the step workpiece that is parallel to the piezoelectric chip. The step surface reflects the propagated ultrasonic waves. Due to the existence of the step surface, two echo signals with a time difference will be generated. The piezoelectric chip receives the reflected wave from the step surface, completing a detection; b. By accurately measuring the propagation time of ultrasonic waves in the spent fuel pool, using the water sound speed calculation model, the propagation speed of sound waves in the water of the spent fuel pool, that is, the water sound speed, is calculated. The calculation formula is as follows: c = 2Δd / Δt, Where Δd is the step spacing, c is the water sound speed, and Δt is the time difference between two echoes received by the piezoelectric chip. c. Introduce the water sound velocity-temperature relationship model, design the temperature monitoring method of the spent fuel pool of the nuclear power plant, and calculate the water temperature.

5. The measuring method according to claim 4, characterized in that: The water sound velocity calculation model can obtain the propagation speed of sound waves in the water of the spent fuel pool, and then by introducing the water sound velocity-temperature relationship model, the temperature of the water in the spent fuel pool can be calculated. The calculation formula is as follows: T = (ac) / b Where T is the water temperature, a and b are two constants related to the properties of the liquid, and the constants can be determined according to the specific detection object.

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