CN221926649U - Loop in-water delayed neutron monitoring device and fuel element damage assessment device - Google Patents

Abstract

The utility model relates to a delayed neutron monitoring device in loop water and a fuel element damage evaluation device, wherein the delayed neutron monitoring device comprises: the neutron moderating module comprises a moderating body and a hollow pipeline; the array type plastic scintillator detector is used for detecting beta particles emitted by radionuclides in the loop water; the photoelectric conversion module is used for converting the optical signals detected by the array type plastic scintillator detector into electric signals to obtain first detection signals; the cluster neutron detector is used for detecting neutrons emitted by radionuclides in the loop water; the signal amplification module is used for converting the charge signal detected by the cluster neutron detector into a voltage signal and amplifying the voltage signal to obtain a second detection signal; the coincidence measurement module is used for screening beta signals in the first detection signals, screening neutron signals in the second detection signals, and measuring whether the beta signals and the neutron signals coincide with each other in time or not so as to output delayed neutron signals. Therefore, online accurate monitoring of delayed neutrons in the loop water can be realized.

Description

Delayed neutron monitoring device in loop water and fuel element damage assessment device

Technical Field

The utility model relates to the field of nuclear physics, in particular to a delayed neutron monitoring device in loop water and a fuel element damage assessment device.

Background Art

Damage to reactor fuel elements will cause radioactive nuclides to leak into the coolant loop water. Some precursor nuclides (such as ⁸⁷ Br) will emit neutrons after β decay. These neutrons emitted by β decay are called β-delayed neutrons. Therefore, the damage of fuel elements can be determined by monitoring the delayed neutrons in the loop water. The energy range of delayed neutrons emitted by radioactive nuclides in the loop water is generally hundreds of keV, which is similar to the background neutrons emitted by some activation product decays and the background neutrons produced by (γ, n) reactions. Therefore, the background neutrons emitted by activation product decays, the background neutrons produced by (γ, n) reactions, and the γ radiation background interfere with the detection of delayed neutrons.

For delayed neutron detection in the field of nuclear physics, currently neutron detectors are usually used to monitor delayed neutrons in loop water. However, neutron detectors can generally only detect neutrons, but cannot distinguish between delayed neutrons and background neutrons. Therefore, misjudgments often occur when determining the damage of fuel elements.

Utility Model Content

In view of this, the utility model proposes a delayed neutron monitoring and fuel element damage assessment device in reactor loop water, which can realize online accurate monitoring of delayed neutrons in loop water, so as to help reduce the misjudgment rate of reactor fuel element damage.

According to one aspect of the utility model, a delayed neutron monitoring device in reactor loop water is provided, the device comprising: a neutron moderation module, comprising a moderator body and a hollow pipe in the middle of the moderator body, the hollow pipe is used to accommodate and circulate the reactor loop water, the moderator body is used to moderate the neutrons in the loop water, the pipe wall of the hollow pipe is grooved to set a photoelectric conversion module and fix an array-type plastic scintillator detector, a plurality of cluster-type neutron detectors and a signal amplification module are arranged in the moderator body at intervals; the array-type plastic scintillator detector is used to detect β particles emitted by radioactive nuclides in the loop water; the photoelectric conversion module is used to convert the β particles detected by the array-type plastic scintillator detector into a signal amplification module; The optical signal generated by the particle is converted into an electrical signal to obtain a first detection signal and send it to the coincidence measurement module; the beam-type neutron detector is used to detect neutrons emitted by radioactive nuclides in the loop water; the signal amplification module is used to convert the charge signal generated by the beam-type neutron detector when detecting neutrons into a voltage signal and amplify it to obtain a second detection signal and send it to the coincidence measurement module; the coincidence measurement module is used to identify the β signal caused by β particles in the first detection signal, identify the neutron signal caused by neutrons in the second detection signal, and measure whether the β signal and the neutron signal are temporally correlated, so as to output a delayed neutron signal caused by delayed neutrons in the loop water.

In a possible implementation, the moderator body is composed of at least two plate-like assemblies; holes or grooves are opened in the plate-like assembly to arrange a plurality of cluster neutron detectors and signal amplification modules at intervals.

In a possible implementation, the material of the moderator body is high-density polyethylene, and the outer wall of the moderator body is sequentially coated with a cadmium layer and a lead layer, or sequentially coated with a cadmium layer, a polyethylene layer and a lead layer; the cadmium layer is used to prevent the overflow of thermal neutrons in the loop water and to shield thermal neutrons in the environment, the polyethylene layer is used to shield neutrons in the environment, and the lead layer is used to shield the gamma-ray background and cosmic ray background in the environment.

In a possible implementation, at least one circle of cluster neutron detectors are evenly spaced around the hollow pipe in the moderator body, the cluster neutron detectors are filled with mixed gas, the cluster neutron detectors include multiple boron-coated tubes, and light-shielding measures are taken at both ends of the hollow pipe.

In a possible implementation, the signal amplification module is disposed in the moderator body adjacent to the cluster-type neutron detector, one cluster-type neutron detector corresponds to one signal amplification module, and the signal amplification module includes a charge-sensitive preamplifier.

In one possible implementation, the array-type plastic scintillator detector includes a plurality of plastic scintillators; the plastic scintillator is used to excite scintillation light when beta particles emitted by radioactive nuclides in loop water are detected; the plastic scintillator is in the form of a thin sheet with a thickness of hundreds of microns to increase the contact area between the array-type plastic scintillator detector and the loop water, and the surface of the plastic scintillator is coated with a micron-level reflective layer.

In a possible implementation, photoelectric conversion modules are symmetrically arranged in pairs at both ends of each plastic scintillator, and one plastic scintillator is adjacent to at least two photoelectric conversion modules, wherein the photoelectric conversion modules include silicon photomultiplier tubes.

In a possible implementation, the device further includes: a power supply module, configured to supply power to the cluster neutron detector, the signal amplification module, the photoelectric conversion module, and the coincidence measurement module.

In a possible implementation, the device further includes: a temperature detection module, used to detect the ambient temperature of the photoelectric conversion module; the power supply module is also used to adjust the supply voltage of the photoelectric conversion module according to the ambient temperature detected by the temperature detection module.

According to another aspect of the utility model, a reactor fuel element damage assessment device is provided, comprising: the delayed neutron monitoring device in the reactor loop water; and a fuel element damage assessment module, which is used to assess the damage degree of the reactor fuel element according to the delayed neutron signal output by the delayed neutron monitoring device in the reactor loop water.

According to various aspects of the utility model, the neutron moderation module can be used to slow down the neutrons in the loop water circulating in the hollow pipe and to fix various detectors and other modules. The array-type plastic scintillator detector is used to detect β particles and the beam-type neutron detector is used to detect neutrons. This can improve the detection efficiency of β particles and neutrons, which is beneficial to improve the monitoring efficiency of delayed neutrons in the loop water. The coincidence measurement module is then used to measure whether the β signal in the first detection signal and the neutron signal in the second detection signal are consistent with the time correlation to determine the delayed neutron signal caused by the delayed neutrons. This can realize online and accurate monitoring of delayed neutrons in the loop water, which is beneficial to reduce the misjudgment rate of damage to the reactor fuel elements.

Other features and aspects of the present invention will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the invention and, together with the description, serve to explain the principles of the invention.

FIG1 shows a schematic diagram of a delayed neutron monitoring device in reactor loop water according to an embodiment of the present invention.

2a and 2b are schematic cross-sectional views of two plate-shaped assemblies according to an embodiment of the present invention.

FIG. 2 c shows a schematic cross-sectional view of a moderator body according to an embodiment of the present invention.

FIG. 3 a , FIG. 3 b and FIG. 3 c are schematic diagrams respectively showing three possible disposition positions of the photoelectric conversion module according to an embodiment of the present invention.

FIG4 shows a cross-sectional view of part of a delayed neutron detection device according to an embodiment of the present invention.

FIG. 5 shows a hardware structure diagram of a coincidence measurement module 17 according to an embodiment of the present invention.

Reference numerals

11 represents a moderator body, 12 represents a hollow pipe, 13 represents an array type plastic scintillator detector, 14 represents a photoelectric conversion module, 15 represents a cluster type neutron detector, 16 represents a signal amplification module, 17 represents a coincidence measurement module, 111 represents a circular hole groove on the moderator body 11, 121 represents a groove on the wall of the hollow pipe 12, 131 represents a plastic scintillator, and 151 represents a boron-coated tube.

DETAILED DESCRIPTION

Various exemplary embodiments, features and aspects of the present invention will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

In addition, in order to better illustrate the utility model, numerous specific details are given in the specific embodiments below. Those skilled in the art will appreciate that the utility model can also be implemented without certain specific details. In some instances, methods, means, components and circuits well known to those skilled in the art are not described in detail in order to highlight the gist of the utility model. It should be understood that the specific embodiments described herein are intended only to explain the utility model, rather than to limit the utility model. For those skilled in the art, the utility model can be implemented without the need for some of these specific details. The following description of the embodiments is merely to provide a better understanding of the utility model by illustrating examples of the utility model.

It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "include..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

FIG1 is a schematic diagram of a delayed neutron monitoring device in reactor loop water according to an embodiment of the present invention. As shown in FIG1 , the device comprises:

A neutron moderation module comprises a moderator body 11 and a hollow pipe 12 in the middle of the moderator body 11, wherein the hollow pipe 12 is used to contain and circulate the loop water of the reactor, and the moderator body 11 is used to moderate the neutrons in the loop water. A photoelectric conversion module 14 is provided in a groove on the wall of the hollow pipe 12 and an array-type plastic scintillator detector 13 is fixed thereon. A plurality of cluster-type neutron detectors 15 and a signal amplification module 16 are provided at intervals in the moderator body 11;

An array type plastic scintillator detector 13, used to detect beta particles emitted by radionuclides in the loop water;

The photoelectric conversion module 14 is used to convert the optical signal generated by the array-type plastic scintillator detector 13 detecting beta particles into an electrical signal, obtain a first detection signal and send it to the coincidence measurement module 17;

A cluster neutron detector 15, used to detect neutrons emitted by radionuclides in the loop water;

The signal amplification module 16 is used to convert the charge signal generated by the cluster neutron detector 15 when detecting neutrons into a voltage signal and amplify the signal to obtain a second detection signal and send the second detection signal to the coincidence measurement module 17;

The compliance measurement module 17 is used to identify the beta signal caused by beta particles in the first detection signal, identify the neutron signal caused by neutrons in the second detection signal, and measure whether the beta signal and the neutron signal are temporally correlated to output a delayed neutron signal caused by the delayed neutrons in the loop water.

It should be understood that the hardware structure of the monitoring device shown in Figure 1 is only an exemplary hardware structure proposed in an embodiment of the utility model. In fact, those skilled in the art can design the position and layout of each detector and each module in the moderator body according to actual needs. For example, the outlet at the lower end of the hollow pipe can be set on the side of the bottom of the moderator body 11, so that the monitoring device can be stably placed on the ground.

In a possible implementation, the material of the moderator body 11 can be high-density polyethylene, and the outer wall of the moderator body can be coated with a cadmium layer and a lead layer in sequence, or a cadmium layer, a polyethylene layer and a lead layer in sequence; the cadmium layer is used to prevent the overflow of thermal neutrons in the loop water and shield the thermal neutrons in the environment, the polyethylene layer is used to shield the neutron background in the environment, and the lead layer is used to shield the gamma-ray background and the cosmic ray background in the environment. The cadmium layer can absorb thermal neutrons in the loop water and the environment, thereby preventing the overflow of thermal neutrons in the loop water and shielding the thermal neutrons in the environment, wherein the polyethylene layer can be made of boron-containing polyethylene or polyethylene. It should be understood that the embodiment of the utility model does not limit the thickness of the cadmium layer, the polyethylene layer and the lead layer. For example, the cadmium layer can have a thickness of millimeters, the lead layer can have a thickness of centimeters, and the polyethylene layer can have a thickness of centimeters. By sequentially coating the outer wall of the moderator body with a cadmium layer and a lead layer, or sequentially coating the outer wall with a cadmium layer, a polyethylene layer and a lead layer, the interference of thermal neutrons, neutron background, gamma-ray background and cosmic ray background in the environment on the detection of delayed neutrons in the loop water can be reduced, and the user can be protected from being irradiated by radioactive substances in the loop water.

In a possible implementation, the moderator body 11 can be composed of at least two plate-like assemblies. The embodiment of the utility model does not limit the size and combination of the plate-like assemblies. For example, four plate-like assemblies can also be used, and each plate-like assembly can be connected by bonding, etc., as long as it can be combined into a moderator body of the required size based on the processing technology. Exemplarily, the cross-sectional schematic diagrams of two plate-like assemblies shown in Figures 2a and 2b, and the cross-sectional schematic diagram of a moderator body 11 shown in Figure 2c, can be combined into the moderator body 11 shown in Figure 2c using the two plate-like assemblies shown in Figures 2a and 2b, and the middle area of the moderator body shown in Figure 2c can be directly used as a hollow pipe, or an adapted hollow pipe can be added, and the embodiment of the utility model does not limit this. Among them, the tube wall of the hollow pipe 12 has a plurality of grooves 121 to set the photoelectric conversion module 14 and fix the array type plastic scintillator detector 13; holes or grooves can be opened in the plate-like assembly to set a plurality of clustered neutron detectors and signal amplification modules at intervals, for example, the plurality of circular holes and grooves 111 shown in FIG2c can be respectively provided with clustered neutron detectors 15 and signal amplification modules 16. It should be understood that the moderator body 11 can also be directly processed into an integral molding by a mold, and the embodiment of the utility model does not limit the shape, size and processing method of the moderator body, and the shape of the hollow pipe shown in FIG2c is a possible implementation method provided by the embodiment of the utility model, and those skilled in the art can process the hollow pipe into a circle, rectangle, etc. according to actual needs, and the embodiment of the utility model does not limit this.

As described above, a plurality of cluster neutron detectors 15 and signal amplification modules 16 are arranged at intervals in the moderator body 11. In order to enable the cluster neutron detectors 15 to detect neutrons emitted by radioactive nuclides in the loop water more efficiently, the holes or grooves opened in the plate-like assembly can be evenly distributed around the hollow pipe for at least one circle. Thus, at least one circle of cluster neutron detectors can be evenly arranged around the hollow pipe in the moderator body. For example, two circles of cluster neutron detectors and signal amplification modules can be arranged in two circles of circular center hole grooves in the moderator body 11 shown in FIG. 2c, that is, four cluster neutron detectors and four signal amplification modules can be arranged in the inner circle and the outer circle, respectively.

Among them, a cluster neutron detector can be composed of multiple neutron detectors to improve the neutron detection efficiency. A mixed gas of suitable pressure can be filled into each neutron detector to make the neutron detector insensitive to gamma rays, so that the cluster neutron detector has a higher neutron detection efficiency. Among them, the neutron detector can use a boron-coated tube, that is, a cluster neutron detector can include multiple boron-coated tubes. It should be understood that the boron-coated tube is a possible neutron detector provided by the example of the utility model. In fact, those skilled in the art can use a neutron detector of a type known in the art according to actual needs, and the embodiment of the utility model is not limited to this.

In a possible implementation, as shown in FIG1 , the signal amplification module 16 is disposed in the moderator body 11 adjacent to the cluster-type neutron detector 15 so as to be able to convert the charge signal detected by the cluster-type neutron detector 15 into a voltage signal in real time and send it to the compliance measurement module 17. One cluster-type neutron detector corresponds to one signal amplification module, and the signal amplification module includes a charge-sensitive preamplifier. Among them, the charge-sensitive preamplifier has a small size, low noise and can effectively process the charge signal output by the neutron detector. Of course, other preamplifiers known in the art can also be used, which is not limited to this embodiment of the utility model. Optionally, a signal amplification module can also be designed to convert the charge signal into a current signal and amplify it to obtain a first detection signal, which is not limited to this embodiment of the utility model.

In one possible implementation, the array-type plastic scintillator detector 13 may include multiple plastic scintillator detectors; each plastic scintillator detector includes a plastic scintillator, that is, the array-type plastic scintillator detector 13 includes multiple plastic scintillators, and the plastic scintillator is used to excite scintillation light (that is, generate light signals) when β particles emitted by radioactive nuclides in the loop water are detected; wherein the plastic scintillator is in the form of a thin sheet with a thickness of hundreds of microns to increase the contact area between the array-type plastic scintillator detector and the loop water.

As shown in FIG1 , the loop water flows in from the inlet at the upper end of the hollow pipe 12 and flows out from the outlet at the lower end. The wall of the hollow pipe 12 is grooved to fix the array-type plastic scintillator detector 13, that is, the array-type plastic scintillator detector 13 is arranged in the hollow pipe, so that when the loop water flows through the hollow pipe, the contact area between the thin sheet of plastic scintillator and the loop water increases, which can effectively improve the beta particle detection efficiency of the plastic scintillator, wherein the surface of the plastic scintillator can be coated with a reflective layer, which has a reflective effect, can prevent scintillation fluorescence from entering the water body, and protect the plastic scintillator. In practical applications, those skilled in the art can use plastic scintillator detectors known in the art, for example, plastic scintillator detectors including thin sheet of plastic scintillator, light-conducting film, silicone grease film, reflective film and other materials can be used. The embodiment of the utility model does not limit the type, size, etc. of the array-type plastic scintillator detector 13.

Considering that the plastic scintillator needs to be in a light-proof environment, light-proof measures can be adopted at both ends of the hollow pipe. For example, a light-proof film or a light-proof material can be covered at both ends of the hollow pipe to prevent ambient light from entering the interior of the hollow pipe and affecting the array-type plastic scintillator detector 13 in the hollow pipe. In this way, there is no need to cover the plastic scintillator with a light-proof film or coat it with a light-proof layer, which can improve the detection efficiency of the plastic scintillator for β particles in the loop water and is easy to process.

In a possible implementation, photoelectric conversion modules are symmetrically arranged in pairs at both ends of each plastic scintillator, and one plastic scintillator is adjacent to at least two photoelectric conversion modules, which can improve the photoelectric conversion efficiency, thereby facilitating the improvement of the delayed neutron detection efficiency, wherein the photoelectric conversion module includes a silicon photomultiplier tube (SiPM). It should be understood that the silicon photomultiplier tube is a possible photoelectric conversion device provided by the embodiment of the utility model. In fact, those skilled in the art can use photoelectric conversion devices known in the art to implement the functions required to be implemented by the above-mentioned photoelectric conversion module, and the embodiment of the utility model is not limited to this.

Among them, the symmetrical arrangement of the photoelectric conversion modules in pairs at both ends of each of the above-mentioned plastic scintillators can be understood as symmetrically arranging at least two photoelectric conversion modules at the left and right ends of the plastic scintillator, respectively. The symmetry can be symmetrical about the center of the plastic scintillator. By way of example, Figures 3a, 3b and 3c respectively show three possible arrangement positions of the photoelectric conversion modules provided by the embodiment of the utility model. As shown in Figure 3a, a photoelectric conversion module 14 can be respectively arranged at the upper left corner and the lower right corner of the plastic scintillator 131. As shown in Figure 3b, three photoelectric conversion modules 14 can be respectively arranged symmetrically at intervals on the left and right sides of the plastic scintillator 131. As shown in Figure 3c, two photoelectric conversion modules 14 can also be arranged on the left and right sides of the plastic scintillator 131. The embodiment of the utility model does not limit the shape, size and number of the photoelectric conversion modules 14. The more the number of photoelectric conversion modules, the larger the coverage area and the higher the photoelectric conversion efficiency.

Exemplarily, FIG4 shows a cross-sectional view of a portion of a delayed neutron detection device. As shown in FIG4, a cluster-type neutron detector 15 can be set in the eight circular hole grooves in the moderator body 11 shown in FIG2c. Each cluster-type neutron detector 15 includes 7 boron-coated tubes 151, and each boron-coated tube can be filled with a mixed gas. A photoelectric conversion module 14 is set in the wall groove of the central pipe 12 and an array-type plastic scintillator detector 13 is fixed, that is, a plurality of plastic scintillators are fixed.

In a possible implementation, the device may further include: a power module 18, which is used to power the cluster neutron detector 15, the signal amplification module 16, the photoelectric conversion module 14, and the coincidence measurement module 17. In practical applications, the power module 18 can be integrated into the coincidence measurement module 17, and can independently power multiple cluster neutron detectors 15, multiple signal amplification modules 16, multiple photoelectric conversion modules 14, and the coincidence measurement module 17. In practical applications, the power module 18 can be powered by an external power supply or a battery, which is not limited in this embodiment of the utility model.

Taking into account that the working state of the devices (such as SiPM) in the photoelectric conversion module 14 is greatly affected by the ambient temperature, in order to ensure the normal operation of the photoelectric conversion module 14, each photoelectric conversion module 14 can be powered independently and the ambient temperature of each photoelectric conversion module can be monitored separately, and then the power supply voltage of the photoelectric conversion module is adjusted according to the detected ambient temperature. Therefore, in a possible implementation method, the device also includes: a temperature detection module 19, which is used to detect the ambient temperature of the photoelectric conversion module 14, and the detected ambient temperature can be sent to the power supply module 18, wherein one photoelectric conversion module can correspond to one temperature detection module, and the temperature detection module 19 can include a temperature sensor known in the art, as long as it can detect the ambient temperature; further, the power supply module 18 is also used to adjust the power supply voltage of the photoelectric conversion module 14 according to the ambient temperature detected by the temperature detection module 19.

In practical applications, there is a certain mapping relationship between the ambient temperature of the photoelectric conversion module and the power supply voltage. Based on the mapping relationship, the power supply module 18 can adjust the power supply voltage of the photoelectric conversion module 14 in real time according to the ambient temperature detected by the temperature detection module 19, because the parameters of the photoelectric conversion module change with the temperature, and the power supply voltage needs to be adjusted with the temperature to ensure that the parameters are stable. Optionally, a photoelectric conversion module 14 can be integrated with a temperature detection module 18 on a circuit board to facilitate the detection of the ambient temperature of each photoelectric conversion module 14. It should be understood that the power supply module 18 can also supply power to each temperature detection module 19 at the same time.

It can be known that the plastic scintillator in the array-type plastic scintillator detector 13 not only reacts to β particles, but also reacts to neutrons and γ rays, that is, the plastic scintillator can detect not only β particles, but also neutrons and γ rays, but the light signals generated by different detection objects are different, which makes the first detection signal output by the photoelectric conversion module 14 may include a β signal caused by β particles, a neutron signal caused by neutrons and/or a γ signal caused by γ rays. Therefore, after receiving the first detection signal sent by the photoelectric conversion module 14, the compliance measurement module 17 can first identify the first detection signal to determine the β signal caused by β particles. Also, the cluster neutron detector (such as the cluster boron-coated tube) not only reacts to neutrons, but also reacts to gamma rays, that is, the cluster neutron detector 15 can detect neutrons and gamma rays in the loop water, so the second detection signal may include a neutron signal caused by neutrons and/or a gamma signal caused by gamma rays. Therefore, the compliance measurement module 17 can first identify the first detection signal after receiving the second detection signal sent by the signal amplification module 16 to determine the neutron signal caused by the neutron. Among them, since the pulse amplitudes and pulse shapes of different signals are different, the β signal, the gamma signal and the neutron signal can be identified according to the signal pulse amplitude and/or pulse shape. The embodiment of the utility model does not limit the signal identification method.

Furthermore, the β-n coincidence measurement technology (n represents neutron) known in the art can be used to measure whether the β signal and the neutron signal are temporally correlated, that is, to determine whether the β signal and the neutron signal are temporally correlated. It should be understood that the delayed neutrons released by the radioactive nuclide after β decay are temporally correlated with the released β particles, that is, temporally consistent with the correlation. Therefore, if the neutron signal is a signal caused by a delayed neutron, the β signal and the neutron signal should be temporally correlated. If the neutron signal is a signal caused by other background neutrons, the β signal and the neutron signal are not temporally correlated. Specifically, the β signal can be used as a trigger signal, and the β signal can be appropriately delayed to measure whether the delayed β signal and the neutron signal are temporally correlated. If the two are temporally correlated, the neutron signal can be determined as a delayed neutron signal. This method can be understood as adding a time window to the β signal. If the neutron signal appears within the time window, the neutron signal is considered to be a delayed neutron signal that is temporally correlated with the β signal. That is, the compliance measurement module can have a delayed compliance measurement function, that is, it can measure whether the delay between signals meets preset conditions. The preset conditions can be set as needed, such as the delay does not exceed a predetermined time length. After the β signal is detected, the delayed compliance measurement function can be automatically triggered to determine whether the neutron signal and the β signal are temporally correlated, thereby determining the delayed neutron signal.

The compliance measurement module 17 can be implemented through hardware circuits based on relevant technologies. The present invention does not limit the specific circuit structure of the compliance measurement module 17, as long as it can determine whether the delay between signals meets the preset conditions. Exemplarily, FIG5 shows a hardware structure diagram of a compliance measurement module 17 provided in an embodiment of the utility model. As shown in FIG5, the compliance measurement module 17 may include: a linear amplifier for amplifying an input signal, which can be used to amplify a first detection signal and a second detection signal in an embodiment of the utility model; a pulse amplitude discriminator, which can be used to convert an input pulse whose amplitude exceeds (or is lower than) a certain set level into a pulse output whose amplitude and width meet certain standards, and filter out any input signal below (or above) the set level. In an embodiment of the utility model, it can be used to perform amplitude discrimination on the second detection signal to output a neutron signal and filter out a γ signal; a pulse shape discriminator can be used to give a pulse leading and trailing edge value according to the pulse amplitude, compare the pulse width between the values with a preset time (for example, the pulse width of a β signal can be used as the preset time), output a pulse signal whose pulse width meets the preset time, and filter out a pulse signal whose pulse width does not meet the preset time. In an embodiment of the utility model, the pulse shape discriminator can be combined with the pulse amplitude discriminator to jointly The first detection signal is subjected to shape discrimination and amplitude discrimination to output a β signal and filter out the neutron signal and the γ signal; a delayed coincidence circuit is used to add an appropriate delay to the input signal at one end and compare it with the input signal at the other end. If the two signals are time-correlated, the signal input at one end is output. In the embodiment of the utility model, it can be used to add a delay to the β signal and compare it with the neutron signal. If the delayed β signal and the neutron signal are time-correlated, the neutron signal is output. It should be understood that the embodiment of the utility model does not limit the circuit structure of the delayed coincidence circuit. The delayed coincidence circuit is a coincidence circuit for measuring delayed coincidence. For example, it can be composed of a delay circuit and a logic gate circuit. The delay circuit can add a delay to the β signal. The logic gate circuit can output the neutron signal when the neutron signal and the delayed β signal are time-correlated. For example, when there are positive pulses input at both input ends of the logic gate circuit, that is, when the neutron signal and the delayed β signal are both positive pulses, the logic gate circuit opens and outputs the neutron signal as a delayed neutron signal, otherwise no pulse signal is output.

It should be noted that the compliance measurement module shown in Figure 5 is an exemplary implementation method provided by the embodiment of the utility model. The various devices in the compliance measurement module shown in Figure 5 are existing devices in the field. Those skilled in the art can design the specific circuit structure of the compliance measurement module 17 according to actual needs. It should be understood that the required functional modules can be added to the compliance measurement module 17 according to actual conditions. Those skilled in the art can adopt the compliance measurement devices and systems known in the art as the compliance measurement module 17 used in the embodiment of the utility model. Of course, they can also customize the hardware structure of the compliance measurement module 17. The compliance measurement module 17 can also be implemented in a combination of software and hardware. The embodiment of the utility model does not limit the hardware structure of the compliance measurement module.

According to the delayed neutron monitoring device of the embodiment of the utility model, the neutron moderating module can be used to moderate the neutrons in the loop water circulating in the hollow pipe, and various detectors and other modules can be fixedly set. The array-type plastic scintillator detector is used to detect β particles, and the beam-type neutron detector is used to detect neutrons. This can improve the detection efficiency of β particles and neutrons, which is beneficial to improving the monitoring efficiency of delayed neutrons in the loop water. The coincidence measurement module is then used to measure whether the β signal in the first detection signal and the neutron signal in the second detection signal are consistent with the time correlation to determine the delayed neutron signal caused by the delayed neutrons. This can realize online and accurate monitoring of delayed neutrons in the loop water, which is beneficial to reducing the misjudgment rate of reactor fuel element damage.

Based on the delayed neutron monitoring device in reactor loop water provided by the above embodiment of the utility model, the embodiment of the utility model further provides a reactor fuel element damage assessment device, which is characterized by comprising: the delayed neutron monitoring device in reactor loop water provided by the above embodiment of the utility model; and

The fuel element damage assessment module is used to assess the damage degree of the reactor fuel elements according to the delayed neutron signal output by the delayed neutron monitoring device in the reactor loop water.

It should be understood that those skilled in the art can adopt the reactor fuel element damage assessment technology known in the art to evaluate the damage degree of the reactor fuel element based on the delayed neutron signal. For example, the delayed neutron injection rate can be determined based on the delayed neutron signal, and then the damage degree of the reactor fuel element can be determined based on the delayed neutron injection rate. The embodiments of the present utility model are not limited to this.

The embodiments of the present invention do not limit the hardware form of the fuel element damage assessment module. For example, application specific integrated circuits (ASIC), programmable logic devices (PLD), field programmable gate arrays (FPGA), general-purpose processors, controllers, microcontrollers, microprocessors, etc. can be used.

By using the reactor fuel element damage assessment device of the embodiment of the utility model, the misjudgment rate of reactor fuel element damage can be effectively reduced, and the degree of reactor fuel element damage can be effectively detected.

The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims (10)

1. A delayed neutron monitoring device in reactor loop water, characterized in that the device comprises: A neutron moderation module, comprising a moderator body and a hollow pipe in the middle of the moderator body, wherein the hollow pipe is used to contain and circulate the loop water of the reactor, and the moderator body is used to moderate the neutrons in the loop water. The wall of the hollow pipe is grooved to set a photoelectric conversion module and fix an array-type plastic scintillator detector, and a plurality of cluster-type neutron detectors and a signal amplification module are arranged in the moderator body at intervals; The array-type plastic scintillator detector is used to detect beta particles emitted by radionuclides in loop water; The photoelectric conversion module is used to convert the optical signal generated by the array-type plastic scintillator detector detecting beta particles into an electrical signal to obtain a first detection signal and send it to the coincidence measurement module; The cluster neutron detector is used to detect neutrons emitted by radionuclides in the loop water; The signal amplification module is used to convert the charge signal generated by the cluster neutron detector when detecting neutrons into a voltage signal and amplify the signal to obtain a second detection signal and send the second detection signal to the coincidence measurement module; The coincidence measurement module is used to identify the beta signal caused by beta particles in the first detection signal, identify the neutron signal caused by neutrons in the second detection signal, and measure whether the beta signal and the neutron signal are temporally correlated, so as to output a delayed neutron signal caused by delayed neutrons in the loop water. 2. The device according to claim 1 is characterized in that the moderator body is composed of at least two plate-like assemblies; holes or grooves are opened in the plate-like assembly to arrange multiple cluster-type neutron detectors and signal amplification modules at intervals. 3. The device according to claim 1 or 2, characterized in that the material of the moderator body is high-density polyethylene, and the outer wall of the moderator body is sequentially coated with a cadmium layer and a lead layer, or sequentially coated with a cadmium layer, a polyethylene layer and a lead layer; The cadmium layer is used to prevent thermal neutrons in the loop water from overflowing and to shield thermal neutrons in the environment, the polyethylene layer is used to shield neutrons in the environment, and the lead layer is used to shield the gamma ray background and cosmic ray background in the environment. 4. The device according to claim 1 is characterized in that at least one circle of cluster-type neutron detectors are evenly spaced around the hollow pipe in the moderator body, the cluster-type neutron detectors are filled with mixed gas, the cluster-type neutron detectors include multiple boron-coated tubes, and light-shielding measures are taken at both ends of the hollow pipe. 5. The device according to claim 1 or 4 is characterized in that the signal amplification module is disposed in the moderator body adjacent to the cluster-type neutron detector, one cluster-type neutron detector corresponds to one signal amplification module, and the signal amplification module includes a charge-sensitive preamplifier. 6. The device according to claim 1 is characterized in that the array-type plastic scintillator detector comprises a plurality of plastic scintillators; the plastic scintillator is used to excite scintillation light when detecting beta particles emitted by radioactive nuclides in the loop water; the plastic scintillator is in the form of a thin sheet with a thickness of hundreds of microns to increase the contact area between the array-type plastic scintillator detector and the loop water, and the surface of the plastic scintillator is coated with a micron-level reflective layer. 7 . The device according to claim 6 , wherein photoelectric conversion modules are symmetrically arranged in pairs at both ends of each plastic scintillator, and one plastic scintillator is adjacent to at least two photoelectric conversion modules, and the photoelectric conversion modules include silicon photomultiplier tubes. 8. The device according to claim 1, characterized in that the device further comprises: A power supply module is used to supply power to the cluster neutron detector, the signal amplification module, the photoelectric conversion module and the coincidence measurement module. 9. The device according to claim 8, characterized in that the device further comprises: A temperature detection module, used to detect the ambient temperature of the photoelectric conversion module; The power supply module is also used to adjust the power supply voltage of the photoelectric conversion module according to the ambient temperature detected by the temperature detection module. 10. A reactor fuel element damage assessment device, comprising: a delayed neutron monitoring device in reactor loop water according to any one of claims 1 to 9; and The fuel element damage assessment module is used to assess the damage degree of the reactor fuel elements according to the delayed neutron signal output by the delayed neutron monitoring device in the reactor loop water.