CN115144426A - Nuclear fuel rod active detection method and system - Google Patents

Nuclear fuel rod active detection method and system Download PDF

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Publication number
CN115144426A
CN115144426A CN202210811234.9A CN202210811234A CN115144426A CN 115144426 A CN115144426 A CN 115144426A CN 202210811234 A CN202210811234 A CN 202210811234A CN 115144426 A CN115144426 A CN 115144426A
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nuclear fuel
fuel rod
pellet
detected
standard
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王长虹
刘明
张雷
马金波
黄少川
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China Nuclear Power Engineering Co Ltd
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China Nuclear Power Engineering Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
    • G01N23/221—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material by activation analysis
    • G01N23/222—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material by activation analysis using neutron activation analysis [NAA]
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/20—Measuring radiation intensity with scintillation detectors
    • G01T1/202—Measuring radiation intensity with scintillation detectors the detector being a crystal
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/07—Investigating materials by wave or particle radiation secondary emission
    • G01N2223/074—Investigating materials by wave or particle radiation secondary emission activation analysis
    • G01N2223/0745—Investigating materials by wave or particle radiation secondary emission activation analysis neutron-gamma activation analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/10—Different kinds of radiation or particles
    • G01N2223/101—Different kinds of radiation or particles electromagnetic radiation
    • G01N2223/1013—Different kinds of radiation or particles electromagnetic radiation gamma
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/50—Detectors
    • G01N2223/505—Detectors scintillation
    • G01N2223/5055—Detectors scintillation scintillation crystal coupled to PMT
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/60—Specific applications or type of materials
    • G01N2223/625—Specific applications or type of materials nuclear fuels, laser imploded targets
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

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Abstract

The invention discloses an active detection method for a nuclear fuel rod, which comprises the following steps: acquiring characteristic gamma-ray counting curves of a standard nuclear fuel rod before and after pellet activation, and acquiring characteristic gamma-ray counting curves of a nuclear fuel rod to be detected before and after pellet activation; calculating characteristic gamma-ray counting curves of the standard nuclear fuel rod before and after pellet activation to obtain a final counting curve of the standard nuclear fuel rod, and calculating characteristic gamma-ray counting curves of the nuclear fuel rod to be detected before and after pellet activation to obtain a final counting curve of the nuclear fuel rod to be detected; calculating to obtain the pellet abundance of the nuclear fuel rod to be detected, and judging whether the pellet abundance of the nuclear fuel to be detected is qualified. The invention also discloses an active detection system of the nuclear fuel rod. The invention can correct the pellet age of the nuclear fuel rod, eliminate the misjudgment caused by different pellet ages and prolong the service life of the nuclear fuel rod 252 Life or reduction of Cf neutron sources 252 Initial of Cf neutron sourceInitial loading amount and cost reduction.

Description

Nuclear fuel rod active detection method and system
Technical Field
The invention belongs to the technical field of nuclear engineering, and particularly relates to an active detection method and system for a nuclear fuel rod.
Background
The nuclear fuel rod is a unit body of the reactor for releasing heat, and is a core component of the reactor. The nuclear fuel rod is in a strong neutron field when the reactor is operated, is subjected to scouring of high-temperature, high-pressure and high-flow-rate coolant, and simultaneously bears the chemical action of fissile materials, complex mechanical load and steam corrosion, and the working condition is very harsh. When manufacturing characteristics such as the abundance of pellets in the nuclear fuel rod are inconsistent with the design value of the nuclear fuel rod, the reactor core reactivity of the reactor deviates from the expectation, so that the control difficulty of the reactor is increased, and the operation of the reactor is influenced. Therefore, it is necessary to perform a 100% abundance check of all pellets loaded inside it after the nuclear fuel rod is assembled and before the fuel assembly is loaded.
Currently, the active detection device of the nuclear fuel rod generally uses 0.3-1.2 mg 252 The Cf neutron source activates the nuclear fuel rod, and then the scintillator detector with 2-4 holes detects the internal self-ignition of the nuclear fuel rod 235 The intensity of gamma rays emitted by U or other fissile material activation products is used for estimating the characteristic abundance parameter of the pellets in the nuclear fuel rod.
Due to the fact that 252 Half-life of Cf 2.7 years, 1.2mg 252 When the Cf neutron source device has the neutron yield reduced and the activation capacity weakened after the time (less than 5 years) of less than two half-lives, the proportion of the intensity of the gamma rays spontaneously emitted by the core block matrix in the nuclear fuel rod in the intensity of the gamma rays detected by the scintillator detector is increased and reaches a recognizable degree. However, the intensity of the spontaneously emitted gamma rays of the pellets of the same abundance is related to the time (pellet age) for the pellets to pass the last chemical conversion, so that the intensity of the gamma rays detected by the nuclear fuel rods filled with pellets of the same abundance and different ages after the activation of the active detection device is inconsistent, thereby causing the gamma rays to be emitted 235 The abundance of U is qualifiedThe nuclear fuel rod is misjudged as an unqualified problem.
When the neutron source decays to a mass of less than 0.3mg, a new one needs to be loaded into the nuclear fuel rod active inspection device 252 Cf neutron source to avoid the frequent misjudgment caused by different ages of the core blocks. However, it is not currently produced in China 252C The f neutron source needs to be imported from Russia and America, is expensive, and causes high production cost of the nuclear fuel rod.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides the nuclear fuel rod active detection method and the nuclear fuel rod active detection system, which can correct the age of the pellets of the nuclear fuel rod, eliminate the misjudgment caused by different ages of the pellets and prolong the service life of the nuclear fuel rod 252 Life or reduction of Cf neutron sources 252 The initial loading of the Cf neutron source reduces the cost.
The technical scheme for solving the technical problems is as follows:
according to an aspect of the present invention, there is provided a nuclear fuel rod active inspection method including:
acquiring a characteristic gamma ray counting curve before the standard nuclear fuel rod pellet is activated and a characteristic gamma ray counting curve after the standard nuclear fuel rod pellet is activated, and acquiring a characteristic gamma ray counting curve before the nuclear fuel rod pellet to be detected is activated and a characteristic gamma ray counting curve after the nuclear fuel rod pellet to be detected is activated;
calculating a characteristic gamma-ray counting curve before the standard nuclear fuel rod pellet is activated and a characteristic gamma-ray counting curve after the standard nuclear fuel rod pellet is activated to obtain a final counting curve of the standard nuclear fuel rod, and calculating a characteristic gamma-ray counting curve before the nuclear fuel rod pellet to be detected is activated and a characteristic gamma-ray counting curve after the nuclear fuel rod pellet to be detected is activated to obtain a final counting curve of the nuclear fuel rod to be detected;
and calculating to obtain the pellet abundance of the nuclear fuel rod to be detected based on the final counting curve of the standard nuclear fuel rod and the final counting curve of the nuclear fuel rod to be detected, and judging whether the pellet abundance of the nuclear fuel to be detected is qualified.
Preferably, the obtaining of the characteristic gamma ray counting curve before the standard nuclear fuel rod pellet activation and the characteristic gamma ray counting curve after the standard nuclear fuel rod pellet activation specifically includes:
respectively collecting characteristic gamma ray characteristic information of standard nuclear fuel rods detected by a single detector before pellet activation to obtain a plurality of first counting curves;
respectively acquiring characteristic gamma ray characteristic information of the standard nuclear fuel rod after pellet activation, which is detected by a single detector, to obtain a plurality of second counting curves;
shifting and accumulating the plurality of first counting curves to obtain a characteristic gamma ray counting curve of the standard nuclear fuel rod before pellet activation;
and shifting and accumulating the plurality of second counting curves to obtain a characteristic gamma ray counting curve of the standard nuclear fuel rod after pellet activation.
Preferably, the method for acquiring the characteristic gamma ray counting curve of the nuclear fuel rod to be detected before pellet activation and the characteristic gamma ray counting curve of the nuclear fuel rod to be detected after pellet activation specifically comprises the following steps:
respectively collecting characteristic gamma ray characteristic information of nuclear fuel rods to be detected, detected by a single detector, before pellet activation to obtain a plurality of third counting curves;
respectively acquiring characteristic gamma ray characteristic information of the nuclear fuel rod to be detected after pellet activation, which is detected by a single detector, to obtain a plurality of fourth counting curves;
shifting and accumulating the plurality of third counting curves to obtain a characteristic gamma ray counting curve of the nuclear fuel rod to be detected before pellet activation;
and shifting and accumulating the plurality of fourth counting curves to obtain a characteristic gamma ray counting curve of the nuclear fuel rod to be detected after pellet activation.
Preferably, the method includes calculating a characteristic gamma ray counting curve before the standard nuclear fuel rod pellet is activated and a characteristic gamma ray counting curve after the standard nuclear fuel rod pellet is activated to obtain a final counting curve of the standard nuclear fuel rod, and calculating a characteristic gamma ray counting curve before the nuclear fuel rod pellet to be detected is activated and a characteristic gamma ray counting curve after the nuclear fuel rod pellet to be detected is activated to obtain a final counting curve of the nuclear fuel rod to be detected, and the method specifically includes:
calculating to obtain an age correction coefficient based on a characteristic gamma-ray counting curve before the standard nuclear fuel rod pellet is activated and a characteristic gamma-ray counting curve after the standard nuclear fuel rod pellet is activated, or based on a characteristic gamma-ray counting curve before the nuclear fuel rod pellet to be detected is activated and a characteristic gamma-ray counting curve after the nuclear fuel rod pellet to be detected is activated;
and calculating to obtain a final counting curve of the standard nuclear fuel rod and a final counting curve of the nuclear fuel rod to be detected based on the age correction coefficient.
Preferably, the age correction coefficient is calculated based on a characteristic gamma ray counting curve before the standard nuclear fuel rod pellet is activated and a characteristic gamma ray counting curve after the standard nuclear fuel rod pellet is activated, or based on a characteristic gamma ray counting curve before the nuclear fuel rod pellet to be detected is activated and a characteristic gamma ray counting curve after the nuclear fuel rod pellet to be detected is activated, and the age correction coefficient specifically includes:
respectively determining the head end and the tail end of a standard/to-be-detected nuclear fuel rod corresponding to the standard/to-be-detected nuclear fuel rod on a characteristic gamma-ray counting curve before the standard/to-be-detected nuclear fuel rod pellet is activated and a characteristic gamma-ray counting curve after the standard/to-be-detected nuclear fuel rod pellet is activated, setting a point corresponding to the head end of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve before the standard/to-be-detected nuclear fuel rod pellet is activated as the starting point of the characteristic gamma-ray counting curve before the standard/to-be-detected nuclear fuel rod pellet is activated and setting a point corresponding to the head end of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve after the standard/to-be-detected nuclear fuel rod pellet is activated as the starting point of the characteristic gamma-ray counting curve after the standard/to-be-detected nuclear fuel rod pellet is activated;
based on the count values of any two time points of the same position of the same standard/nuclear fuel rod to be detected on the characteristic gamma-ray counting curve before the pellet activation of the standard/nuclear fuel rod to be detected and the characteristic gamma-ray counting curve after the pellet activation of the standard/nuclear fuel rod to be detected respectively, the age correction coefficient is obtained by calculation, and the calculation formula is as follows:
F＝(C A1 -C A2 )/(C B1 -C B2 )
wherein F is an age correction factor, C A1 Is the count value of the first time point on the characteristic gamma-ray count curve after the pellet activation of the standard/nuclear fuel rod to be tested, C A2 Is the count value of the second time on the characteristic gamma ray count curve after pellet activation of the standard/to-be-tested nuclear fuel rod, C B1 Is the count value of a first time point on a characteristic gamma ray count curve before pellet activation of a standard/to-be-tested nuclear fuel rod, C B2 Is the count value of the second time point on the characteristic gamma ray count curve before the pellet activation of the standard/to-be-tested nuclear fuel rod.
Preferably, the obtaining of the final count curve of the standard nuclear fuel rod and the final count curve of the nuclear fuel rod to be tested based on the age correction coefficient specifically includes:
subtracting the product of the counting value of the same position of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve of the standard/to-be-detected nuclear fuel rod before the standard/to-be-detected nuclear fuel rod pellet is activated and the age correction coefficient from the counting value of each position of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve of the standard/to-be-detected nuclear fuel rod after the standard/to-be-detected nuclear fuel rod pellet is activated respectively to obtain the final counting value of the counting curve of each position of the standard/to-be-detected nuclear fuel rod, wherein the calculation formula of the final counting value of the counting curve is as follows:
C F ＝C AA －F×C BA
in the formula, C F To count the final count value of the curve, C AA Is the count value on the characteristic gamma ray counting curve of the standard/nuclear fuel rod to be tested after pellet activation, C BA The counting value is the counting value on the characteristic gamma ray counting curve before the pellet of the standard/to-be-detected nuclear fuel rod is activated, and F is the age correction coefficient;
and respectively obtaining the final counting curve of the standard nuclear fuel rod and the final counting curve of the nuclear fuel rod to be detected based on the final counting value of the counting curve of each position of the standard/nuclear fuel rod to be detected.
Preferably, the pellet abundance of the nuclear fuel rod to be detected is calculated based on the final count curve of the standard nuclear fuel rod and the final count curve of the nuclear fuel rod to be detected, and the method specifically includes the following steps:
fitting the pellet abundance values of different positions of the standard nuclear fuel rod with a final counting curve of the standard nuclear fuel rod to obtain an abundance-counting relation equation of the standard nuclear fuel rod;
substituting each count value on the final count curve of the nuclear fuel rod to be detected into an abundance-count relation equation of the standard nuclear fuel rod to obtain an abundance curve of the nuclear fuel rod to be detected;
obtaining the abundance of the pellets at different positions of the nuclear fuel rod to be detected based on the abundance curve of the nuclear fuel rod to be detected;
comparing the abundance of the pellets at different positions of the nuclear fuel rod to be detected with the nuclear fuel rod detection technical indexes, and judging whether the abundance of the pellets of the fuel rod to be detected is qualified or not according to the comparison result.
According to another aspect of the present invention, there is provided a nuclear fuel rod active detection system including a neutron activation unit, a detection unit, and a data acquisition and processing unit, wherein:
the neutron activation unit is used for performing neutron activation on the nuclear fuel rod pellets;
the detection unit comprises a first detector unit (8) and a second detector unit (3), the first detector unit is arranged at the inlet end of the neutron activation unit, is connected with the data acquisition and processing unit and is used for detecting gamma-ray characteristic information before the nuclear fuel rod pellet is activated to obtain a first signal and transmitting the first signal to the data acquisition and processing unit, and the second detector unit is arranged at the outlet end of the neutron activation unit, is connected with the data acquisition and processing unit and is used for detecting gamma-ray characteristic information after the nuclear fuel rod pellet is activated to obtain a second signal and transmitting the second signal to the data acquisition and processing unit;
the data acquisition and processing unit is used for receiving the first signal and the second signal, determining a characteristic gamma-ray counting curve before the nuclear fuel rod pellet is activated and a characteristic gamma-ray counting curve after the nuclear fuel rod pellet is activated according to the first signal and the second signal, calculating the characteristic gamma-ray counting curve before the nuclear fuel rod pellet is activated and the characteristic gamma-ray counting curve after the nuclear fuel rod pellet is activated to obtain a final counting curve of the nuclear fuel rod, calculating the pellet abundance of the nuclear fuel rod based on the final counting curve, and judging whether the pellet abundance of the nuclear fuel rod is qualified.
Preferably, the data acquisition processing unit includes an acquisition module and a calculation module, the acquisition module includes a first pulse amplitude analyzer, a first data acquisition card, a second pulse amplitude analyzer, and a second data acquisition card, wherein:
the first pulse amplitude analyzer is connected with the first detector unit and is used for converting the first signal into a first square wave signal;
the first data acquisition card is respectively connected with the first pulse amplitude analyzer and the computing module and is used for acquiring a first square wave signal converted in the first pulse amplitude analyzer to obtain a characteristic gamma ray counting curve before the nuclear fuel rod pellet is activated and transmitting the characteristic gamma ray counting curve before the nuclear fuel rod pellet is activated to the computing module;
the second pulse amplitude analyzer is connected with the second detector unit and is used for converting the second signal into a second square wave signal;
the second data acquisition card is respectively connected with the second pulse amplitude analyzer and the computing module and is used for acquiring a second square wave signal converted in the second pulse amplitude analyzer to obtain a characteristic gamma ray counting curve of the activated nuclear fuel rod pellets and transmitting the characteristic gamma ray counting curve of the activated nuclear fuel rod pellets to the computing module;
the computing module is preset with the nuclear fuel rod detection technical index data and is used for computing a characteristic gamma ray counting curve before the nuclear fuel rod pellet is activated and a characteristic gamma ray counting curve after the nuclear fuel rod pellet is activated to obtain a final counting curve of the nuclear fuel rod, computing the pellet abundance of the nuclear fuel rod based on the final counting curve, comparing the pellet abundance of the nuclear fuel rod with the nuclear fuel rod detection technical index, and judging whether the pellet abundance of the nuclear fuel rod is qualified or not according to the comparison result.
Preferably, the acquisition module further comprises a first amplifier and a second amplifier, wherein:
the first amplifier is respectively connected with the first detector unit and the first pulse amplitude analyzer and is used for amplifying the first signal detected by the first detector unit and transmitting the first signal to the first pulse amplitude analyzer, and the first pulse amplitude analyzer converts the amplified first signal into the first square wave signal;
the second amplifier is connected to the second detector unit and the second pulse amplitude analyzer, and is configured to amplify the second signal detected by the second detector unit and transmit the second signal to the second pulse amplitude analyzer, and the second pulse amplitude analyzer converts the amplified second signal into the second square wave signal.
Preferably, the first pulse amplitude analyzer and the second pulse amplitude analyzer are each one of a comparator, a single-channel pulse amplitude analyzer, and a multi-channel pulse amplitude analyzer, wherein when the first pulse amplitude analyzer is a single-channel pulse amplitude analyzer, a lower threshold of the single-channel pulse amplitude analyzer is a signal generated by a 250keV gamma ray, and an upper threshold of the single-channel pulse amplitude analyzer is a signal generated by a 1.1MeV gamma ray;
when the second pulse amplitude analyzer is a single-channel pulse amplitude analyzer, the lower threshold of the single-channel pulse amplitude analyzer is a signal corresponding to the maximum noise of the second detector unit, and the upper threshold of the single-channel pulse amplitude analyzer is a signal generated by 2.5MeV gamma rays;
the multichannel pulse amplitude analyzer can receive gamma rays with energy range larger than 2.5MeV.
Preferably, the first detector unit includes a plurality of first detectors, the second detector unit includes a plurality of second detectors, and the first detectors and the second detectors each include a scintillation crystal, a photoelectric conversion device, a preamplifier, and a housing, wherein:
the scintillation crystal and the photoelectric conversion device are both arranged in the shell, through holes are formed in the scintillation crystal and the shell, the through holes are used for nuclear fuel rods to pass through, the scintillation crystal is used for absorbing gamma rays emitted by nuclear fuel rod pellets when the nuclear fuel rods pass through the through holes and then emitting optical signals, and the photoelectric conversion device is used for converting the optical signals emitted by the scintillation crystal into electrical signals and outputting the electrical signals;
the preamplifier is connected to the photoelectric conversion device, and is configured to receive and amplify the electrical signal to obtain the first signal/the second signal.
Preferably, the number of the first detectors is two or more, each of the first detectors is linearly arranged at an inlet end of the neutron activation unit, each of the first detectors is respectively used for detecting gamma-ray characteristic information before activation of the nuclear fuel rod pellets, and the first signal includes the gamma-ray characteristic information before activation of the nuclear fuel rod pellets, which is respectively detected by each of the first detectors;
the number of the second detectors is more than two, each second detector is linearly arranged at the outlet end of the neutron activation unit, each second detector is respectively used for detecting gamma-ray characteristic information of the activated nuclear fuel rod pellets, and the second signals comprise the gamma-ray characteristic information of the activated nuclear fuel rod pellets, which is respectively detected by each second detector.
Preferably, the detection efficiency of the scintillation crystal on gamma rays of 1.1MeV is more than or equal to 75%, and the thickness of the scintillation crystal is 1-2.5 times of the height of the nuclear fuel rod pellet in the length direction of the nuclear fuel rod.
Preferably, the photoelectric conversion device is a photomultiplier tube or a silicon photomultiplier device.
Preferably, the material of the scintillation crystal is one of Bismuth Germanate (BGO), cesium iodide (CsI), sodium iodide (NaI), and Cadmium Zinc Telluride (CZT).
Preferably, the first detector and the second detector both further include a first shield, the first shield is disposed outside the housing and is configured to shield gamma rays lower than 1.1MeV, the first shield is provided with an opening, and a position of the opening is concentric with the through hole on the scintillation crystal.
Preferably, the neutron activation unit comprises a neutron source and a neutron shield, the neutron source is arranged in the neutron shield, an activation channel is arranged on the neutron shield, and the position of the activation channel is concentric with the through holes of the scintillation crystals in the first detector unit and the second detector unit.
Preferably, the number of the activation channels is multiple, the number of the detection units is multiple sets of the same number as the activation channels, the multiple sets of the detection units are arranged in parallel, and a first detector unit and a second detector unit in each set of the detection units are respectively arranged at the inlet end and the outlet end of the same activation channel;
and second shielding bodies are respectively arranged between the first detector unit and between the second detector unit and the second detector unit in the two adjacent sets of detection units, and are used for shielding mutual interference of gamma rays between the activation channels.
Compared with the prior art, the nuclear fuel rod active detection method and the nuclear fuel rod active detection system can correct the age of the pellets of the nuclear fuel rod, eliminate misjudgment caused by different ages of the pellets, and prolong 252 Service life (more than 3 years) or reduction of Cf neutron source 252 The initial loading of the Cf neutron source is reduced to 1/4 of the original loading, so that the cost is reduced.
Drawings
FIG. 1 is a schematic structural view of an active nuclear fuel rod detection system according to an embodiment of the present disclosure;
FIG. 2 is a schematic structural diagram of a data acquisition and processing unit according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of another data acquisition and processing unit according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of the first detector/the second detector in the embodiment of the present invention.
In the figure: 1-a neutron source; 2-a neutron shield; 3-a second detector unit; 4-an acquisition module; 5-a calculation module; 61-feeding frame; 62-blanking frame; 71-a feeding transmission mechanism; 72-a blanking transmission mechanism; 8-a first detector unit; 9-a second data acquisition card; 10-a first amplifier; 11-a first pulse amplitude analyzer; 12-a first data acquisition card; 13-a scintillation crystal; 14-a housing; 15-a shield; 16-a second amplifier; 17-second pulse amplitude analyzer.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the scope of protection of the present invention.
In the description of the present invention, it should be noted that the terms "on" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience and simplicity of description, and do not indicate or imply that the indicated device or element must be provided with a specific orientation, configured and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "connected," "disposed," "mounted," "fixed," and the like are to be construed broadly, e.g., as being fixedly or removably connected, or integrally connected; either directly or indirectly through intervening media, or through the interconnection of two elements. The specific meaning of the above terms in the present invention can be understood in specific cases for those skilled in the art.
Example 1
The embodiment discloses a nuclear fuel rod active detection method, which comprises the following steps:
acquiring a characteristic gamma ray counting curve before the standard nuclear fuel rod pellet is activated and a characteristic gamma ray counting curve after the standard nuclear fuel rod pellet is activated;
acquiring a characteristic gamma ray counting curve before the nuclear fuel rod pellet to be detected is activated and a characteristic gamma ray counting curve after the nuclear fuel rod pellet to be detected is activated;
calculating a characteristic gamma ray counting curve before the standard nuclear fuel rod pellet is activated and a characteristic gamma ray counting curve after the standard nuclear fuel rod pellet is activated to obtain a final counting curve of the standard nuclear fuel rod;
calculating a characteristic gamma ray counting curve before the pellet of the nuclear fuel rod to be detected is activated and a characteristic gamma ray counting curve after the pellet of the nuclear fuel rod to be detected is activated to obtain a final counting curve of the nuclear fuel rod to be detected;
and calculating to obtain the pellet abundance of the nuclear fuel rod to be detected based on the final counting curve of the standard nuclear fuel rod and the final counting curve of the nuclear fuel rod to be detected, and judging whether the pellet abundance of the nuclear fuel to be detected is qualified.
In some embodiments, obtaining a characteristic gamma ray count curve for a standard nuclear fuel rod prior to pellet activation and a characteristic gamma ray count curve for a standard nuclear fuel rod after pellet activation specifically includes:
detecting standard nuclear fuel rods before activation by adopting a plurality of detectors (first detectors), respectively acquiring characteristic gamma-ray characteristic information of the standard nuclear fuel rods before pellet activation detected by a single detector to obtain an initial characteristic gamma-ray counting curve (marked as a first counting curve) of the standard nuclear fuel rods before pellet activation, and shifting and accumulating a plurality of first counting curves to obtain a characteristic gamma-ray counting curve of the standard nuclear fuel rods before pellet activation;
in the same way, a plurality of detectors (second detectors) are adopted to detect the activated standard nuclear fuel rods, the characteristic gamma-ray characteristic information of the activated standard nuclear fuel rods detected by the single detectors is respectively acquired to obtain a plurality of initial characteristic gamma-ray counting curves (marked as second counting curves) of the activated standard nuclear fuel rods after the pellets are activated, and the plurality of second counting curves are shifted and accumulated to obtain the characteristic gamma-ray counting curves of the activated standard nuclear fuel rods after the pellets are activated.
In some embodiments, the obtaining of the characteristic gamma ray counting curve before the activation of the nuclear fuel rod pellet to be detected and the characteristic gamma ray counting curve after the activation of the nuclear fuel rod pellet to be detected specifically includes:
detecting the nuclear fuel rod to be detected before activation by adopting a plurality of detectors (first detectors), respectively acquiring characteristic gamma-ray characteristic information of the nuclear fuel rod to be detected before pellet activation, which is detected by a single detector, to obtain a plurality of initial characteristic gamma-ray counting curves (marked as third counting curves) of the nuclear fuel rod to be detected before pellet activation, and performing shift accumulation on the plurality of third counting curves to obtain the characteristic gamma-ray counting curve of the nuclear fuel rod to be detected before pellet activation;
in a similar way, a plurality of detectors (second detectors) are adopted to detect the activated nuclear fuel rod to be detected, the characteristic gamma ray characteristic information of the nuclear fuel rod to be detected by a single detector after the nuclear fuel rod pellet to be detected is activated is respectively acquired, a plurality of initial characteristic gamma ray counting curves (marked as fourth counting curves) of the nuclear fuel rod to be detected after the nuclear fuel rod pellet is activated are obtained, and the plurality of fourth counting curves are shifted and accumulated to obtain the characteristic gamma ray counting curve of the nuclear fuel rod to be detected after the nuclear fuel rod pellet is activated.
In some embodiments, the method includes calculating a characteristic gamma-ray counting curve before activation of a standard nuclear fuel rod pellet and a characteristic gamma-ray counting curve after activation of the standard nuclear fuel rod pellet to obtain a final counting curve of the standard nuclear fuel rod, and calculating the characteristic gamma-ray counting curve before activation of a nuclear fuel rod pellet to be detected and the characteristic gamma-ray counting curve after activation of the nuclear fuel rod pellet to be detected to obtain a final counting curve of the nuclear fuel rod to be detected, and specifically includes:
calculating to obtain an age correction coefficient based on a characteristic gamma-ray counting curve before the standard nuclear fuel rod pellet is activated and a characteristic gamma-ray counting curve after the standard nuclear fuel rod pellet is activated, or based on a characteristic gamma-ray counting curve before the nuclear fuel rod pellet to be detected is activated and a characteristic gamma-ray counting curve after the nuclear fuel rod pellet to be detected is activated;
and calculating to obtain a final counting curve of the standard nuclear fuel rod and a final counting curve of the nuclear fuel rod to be detected based on the age correction coefficient.
In some embodiments, the calculating the age correction coefficient based on the characteristic gamma-ray counting curve before the standard nuclear fuel rod pellet is activated and the characteristic gamma-ray counting curve after the standard nuclear fuel rod pellet is activated, or based on the characteristic gamma-ray counting curve before the nuclear fuel rod pellet to be detected is activated and the characteristic gamma-ray counting curve after the nuclear fuel rod pellet to be detected is activated specifically includes:
respectively determining the head end and the tail end of a standard/to-be-detected nuclear fuel rod corresponding to the standard/to-be-detected nuclear fuel rod on a characteristic gamma-ray counting curve before the standard/to-be-detected nuclear fuel rod pellet is activated and a characteristic gamma-ray counting curve after the standard/to-be-detected nuclear fuel rod pellet is activated, setting a point corresponding to the head end of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve before the standard/to-be-detected nuclear fuel rod pellet is activated as the starting point of the characteristic gamma-ray counting curve before the standard/to-be-detected nuclear fuel rod pellet is activated and setting a point corresponding to the head end of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve after the standard/to-be-detected nuclear fuel rod pellet is activated as the starting point of the characteristic gamma-ray counting curve after the standard/to-be-detected nuclear fuel rod pellet is activated;
based on the count values of any two time points of the same position of the same standard/to-be-detected nuclear fuel rod on the characteristic gamma ray counting curve before the pellet activation of the standard/to-be-detected nuclear fuel rod and the characteristic gamma ray counting curve after the pellet activation of the standard/to-be-detected nuclear fuel rod, the age correction coefficient is obtained by calculation, and the calculation formula is as follows:
F＝(C A1 -C A2 )/(C B1 -C B2 )
wherein F is an age correction factor, C A1 Is the count value of the first time point on the characteristic gamma-ray count curve after the pellet activation of the standard/nuclear fuel rod to be tested, C A2 Is the count value of the second time on the characteristic gamma-ray counting curve after pellet activation of the standard/nuclear fuel rod to be tested, C B1 Is the count value of a first time point on a characteristic gamma ray count curve before pellet activation of a standard/to-be-tested nuclear fuel rod, C B2 Is the count value of the second time point on the characteristic gamma ray count curve before the pellet activation of the standard/to-be-tested nuclear fuel rod.
In some embodiments, obtaining the final count curve of the standard nuclear fuel rod and the final count curve of the nuclear fuel rod to be tested based on the age correction factor includes:
and respectively subtracting the product of the counting value of the same position of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve of the standard/to-be-detected nuclear fuel rod before the standard/to-be-detected nuclear fuel rod pellet is activated and the age correction coefficient from the counting value of each position of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve of the standard/to-be-detected nuclear fuel rod after the standard/to-be-detected nuclear fuel rod pellet is activated to obtain the final counting value of the counting curve of each position of the standard/to-be-detected nuclear fuel rod, wherein the calculation formula of the final counting value of the counting curve is as follows:
C F ＝C AA －F×C BA
in the formula, C F Is the final count value of the count curve, C AA Is the count value on the characteristic gamma ray counting curve of the standard/nuclear fuel rod to be tested after pellet activation, C BA The counting value is the counting value on the characteristic gamma ray counting curve before the pellet of the standard/to-be-detected nuclear fuel rod is activated, and F is the age correction coefficient;
and respectively obtaining the final counting curve of the standard nuclear fuel rod and the final counting curve of the nuclear fuel rod to be detected based on the final counting value of the counting curve of each position of the standard/nuclear fuel rod to be detected.
In some embodiments, the calculating, based on the final count curve of the standard nuclear fuel rod and the final count curve of the nuclear fuel rod to be tested, the pellet abundance of the nuclear fuel rod to be tested specifically includes:
fitting the pellet abundance values at different positions of the standard nuclear fuel rod with a final counting curve of the standard nuclear fuel rod to obtain an abundance-counting relation equation of the standard nuclear fuel rod;
substituting each count value on the final count curve of the nuclear fuel rod to be detected into the abundance-count relation equation of the standard nuclear fuel rod to obtain an abundance curve of the nuclear fuel rod to be detected;
obtaining the abundance of the pellets at different positions of the nuclear fuel rod to be detected based on the abundance curve of the nuclear fuel rod to be detected;
comparing the abundance of the pellets at different positions of the nuclear fuel rod to be detected with the nuclear fuel rod detection technical indexes, and judging whether the abundance of the pellets of the fuel rod to be detected is qualified or not according to the comparison result.
The nuclear fuel rod active detection method of the embodiment can correct the pellet age of the nuclear fuel rod, eliminate the misjudgment caused by different pellet ages and prolong the service life of the nuclear fuel rod 252 Life or reduction of Cf neutron sources 252 The initial loading of the Cf neutron source reduces the cost.
Example 2
As shown in fig. 1, the present embodiment discloses an active detection system for a nuclear fuel rod, which is used in the active detection method for a nuclear fuel rod described in embodiment 1, and includes a neutron activation unit, a detection unit, and a data acquisition and processing unit, wherein:
the neutron activation unit is used for performing neutron activation on the nuclear fuel rod pellets;
the detection unit comprises a first detector unit 8 and a second detector unit 3, the first detector unit 8 is arranged at the inlet end of the neutron activation unit and connected with the data acquisition and processing unit and used for detecting gamma ray characteristic information before the nuclear fuel rod pellet is activated to obtain a first signal and transmitting the first signal to the data acquisition and processing unit, and the second detector unit 3 is arranged at the outlet end of the neutron activation unit and connected with the data acquisition and processing unit and used for detecting gamma ray characteristic information after the nuclear fuel rod pellet is activated to obtain a second signal and transmitting the second signal to the data acquisition and processing unit;
and the data acquisition processing unit is used for receiving the first signal and the second signal, determining a characteristic gamma-ray counting curve before the nuclear fuel rod pellet is activated and a characteristic gamma-ray counting curve after the nuclear fuel rod pellet is activated according to the first signal and the second signal, calculating the characteristic gamma-ray counting curve before the nuclear fuel rod pellet is activated and the characteristic gamma-ray counting curve after the nuclear fuel rod pellet is activated to obtain a final counting curve of the nuclear fuel rod, calculating the pellet abundance of the nuclear fuel rod based on the final counting curve, and judging whether the pellet abundance of the nuclear fuel rod is qualified.
In some embodiments, the data acquisition processing unit comprises an acquisition module 4 and a calculation module 5, and the acquisition module 4 comprises a first pulse amplitude analyzer 11, a first data acquisition card 12, a second pulse amplitude analyzer 17, and a second data acquisition card 9.
In particular, a first pulse amplitude analyzer 11 is connected to the first detector unit 8 for converting the first signal into a first square wave signal.
The first data acquisition card 12 is connected to the first pulse amplitude analyzer 11 and the calculation module 5, respectively, and is configured to acquire the first square wave signal converted by the first pulse amplitude analyzer 11 to obtain a characteristic gamma ray counting curve before activation of the nuclear fuel rod pellet, and transmit the characteristic gamma ray counting curve before activation of the nuclear fuel rod pellet to the calculation module 5.
A second pulse amplitude analyzer 17 is connected to the second detector unit 3 for converting the second signal into a second square wave signal.
The second data acquisition card 9 is connected with the second pulse amplitude analyzer 17, the second detector unit 3 and the calculation module 5 respectively, and is used for acquiring the first square wave signal converted in the second pulse amplitude analyzer 17 to obtain a characteristic gamma ray counting curve after the nuclear fuel rod pellet is activated, and transmitting the characteristic gamma ray counting curve after the nuclear fuel rod pellet is activated to the calculation module 5.
The calculation module 5 is preset with the nuclear fuel rod detection technical index data and is used for calculating a characteristic gamma ray counting curve before nuclear fuel rod pellet activation and a characteristic gamma ray counting curve after the nuclear fuel rod pellet activation to obtain a final counting curve of the nuclear fuel rod, calculating pellet abundance of the nuclear fuel rod based on the final counting curve, comparing the pellet abundance of the nuclear fuel rod with the nuclear fuel rod detection technical index, and judging whether the pellet abundance of the nuclear fuel rod is qualified or not according to a comparison result.
In this embodiment, the single-point acquisition time of the first data acquisition card 12 and the single-point acquisition time of the second data acquisition card 9 are both 10ms magnitude.
In some embodiments, the acquisition module 4 further comprises a first amplifier 10 and a second amplifier 16.
Specifically, the first amplifier 10 is connected to the first detector unit 8 and the first pulse amplitude analyzer 11, respectively, and is configured to amplify the first signal detected by the first detector unit 8 and transmit the first signal to the first pulse amplitude analyzer 11, and the first pulse amplitude analyzer 11 converts the electric pulse with a specific amplitude in the amplified first signal into the first square wave signal. By providing the first amplifier 10, the matching degree of the first signal amplitude and the first pulse amplitude analyzer 11 can be improved.
The second amplifier 16 is connected to the second detector unit 3 and the second pulse amplitude analyzer 17, and is configured to amplify the second signal detected by the second detector unit 3 and transmit the second signal to the second pulse amplitude analyzer 17, and the second pulse amplitude analyzer 17 converts the electric pulse with a specific amplitude in the amplified second signal into the second square wave signal. By providing the second amplifier 16, the matching degree of the second signal amplitude and the second pulse amplitude analyzer 17 can be improved.
In some embodiments, the first pulse amplitude analyzer 11 and the second pulse amplitude analyzer 17 are each one of a comparator, a single channel pulse amplitude analyzer, and a multichannel pulse amplitude analyzer.
Specifically, when the first pulse amplitude analyzer is a single-channel pulse amplitude analyzer, the lower threshold of the single-channel pulse amplitude analyzer is a pulse signal generated by a 250keV gamma ray, and the upper threshold of the single-channel pulse amplitude analyzer is a pulse signal generated by a 1.1MeV gamma ray. When the second pulse amplitude analyzer is a single-channel pulse amplitude analyzer, the lower threshold of the single-channel pulse amplitude analyzer is a pulse signal corresponding to the maximum noise of the second detector in the second detector unit 3, and the upper threshold of the single-channel pulse amplitude analyzer is a pulse signal generated by a gamma ray of 2.5MeV. The multichannel pulse amplitude analyzer can receive gamma rays with the energy range larger than 2.5MeV.
In some embodiments, the first amplifier 10, the first pulse amplitude analyzer 11, and the first data acquisition card 12 may be discrete devices, or may be a first integrated device having the same functions as the first amplifier 10, the first pulse amplitude analyzer 11, and the first data acquisition card 12, and the first integrated device may directly complete the acquisition and conversion of the first detector unit signal (first signal).
The second amplifier 16, the second pulse amplitude analyzer 17 and the second data acquisition card 9 may be discrete devices (as shown in fig. 2), or may be a second integrated device having the same function as the second amplifier 16, the second pulse amplitude analyzer 17 and the second data acquisition card 9, and the second integrated device may directly complete the acquisition and conversion of the second detector unit signal (second signal).
It should be noted that, as shown in fig. 1 and 3, the second amplifier 16 and the second pulse amplitude analyzer 17 in the present embodiment may be integrated with the second detector unit 3 and integrated on the second detector unit 3.
In some embodiments, the first detector unit 8 comprises a number of first detectors, the second detector unit 3 comprises a number of second detectors, and each of the first and second detectors comprises a scintillation crystal 13, a photoelectric conversion device, a preamplifier, and a housing 14.
Specifically, the scintillation crystal 13 and the photoelectric conversion device are both arranged in the casing 14, through holes are respectively arranged on the scintillation crystal 13 and the casing 14, the through holes are used for the nuclear fuel rods to pass through, the scintillation crystal 13 is used for absorbing gamma rays emitted by the nuclear fuel rod pellets when the nuclear fuel rods pass through the through holes and then emitting optical signals, and the photoelectric conversion device is used for converting the optical signals emitted by the scintillation crystal into electrical signals (electrical pulse signals) and outputting the electrical signals. The preamplifier is connected with the photoelectric conversion device and is used for receiving the electric signal output by the photoelectric conversion device and amplifying the electric signal to obtain the first signal/the second signal.
In this embodiment, the number of the first detectors is two or more, each of the first detectors is linearly arranged at an inlet end of the neutron activation unit, each of the first detectors is respectively used for detecting gamma-ray characteristic information before activation of the nuclear fuel rod pellet, and the first signal includes the gamma-ray characteristic information before activation of the nuclear fuel rod pellet, which is respectively detected by each of the first detectors.
The number of the second detectors is more than two, each second detector is linearly arranged at the outlet end of the neutron activation unit and is respectively used for detecting the gamma-ray characteristic information of the activated nuclear fuel rod pellets, and the second signals comprise the gamma-ray characteristic information of the activated nuclear fuel rod pellets, which is respectively detected by each second detector.
In addition, in this embodiment, third shielding bodies may be further disposed between two adjacent first detectors and between two adjacent second detectors, and the third shielding bodies may be specifically made of tungsten or lead, and are preferably made of tungsten and are used for shielding γ rays to avoid mutual interference.
In this embodiment, the scintillation crystal 13 and the outer shell 14 are preferably perforated with a central hole, i.e., the through hole is located at the center of the scintillation crystal 13 and the outer shell 14, so as to improve the efficiency of space detection of gamma rays of the nuclear fuel rod matrix (pellet).
In some embodiments, the scintillation crystal 13 should have a 1.1MeV gamma ray detection efficiency of > 75%.
Specifically, the material type of the scintillation crystal 13 may be Bismuth Germanate (BGO), cesium iodide (CsI), sodium iodide (NaI), cadmium Zinc Telluride (CZT), or the like. The thickness of the scintillation crystal 13 in the length direction of the nuclear fuel rod is selected according to the height of the cylindrical pellet to be measured in the nuclear fuel rod, and in the present embodiment, the thickness of the scintillation crystal 13 is preferably 1 to 2.5 times the height of the nuclear fuel rod pellet in the length direction of the nuclear fuel rod.
In this embodiment, the photoelectric conversion device is a photomultiplier tube or a silicon photomultiplier.
In some embodiments, both the first and second detectors further comprise a first shield 15.
Specifically, the first shielding body 15 is disposed outside the outer casing 14 for shielding gamma rays below 1.1MeV to shield the outside (including other parts of the nuclear fuel rod) from the operating structure (i.e., the scintillation crystal 13, the photoelectric converter) inside the outer casing 14. The first shield 15 is provided with an opening which is positioned concentrically with (i.e., directly opposite) the through-hole of the scintillator crystal 13 so that the nuclear fuel rod passes through.
In this embodiment, the shielding effect of the first shielding body 15 on the gamma rays below 1.1MeV is required to be more than 98% of the gamma rays, and the first shielding body 15 may be made of tungsten or lead, preferably tungsten.
In some embodiments, the neutron activation unit includes a neutron source 1, a neutron shield 2.
Specifically, the neutron source 1 is arranged in the neutron shield 2, the neutron shield 2 is provided with an activation channel, and the position of the activation channel is concentric with (i.e. opposite to) the through holes of the scintillation crystals 13 in the first detector unit 8 and the second detector unit 3, so that the nuclear fuel rod enters the activation channel for neutron activation after passing through the through holes on the scintillation crystals 13 in the first detector unit 8, and passes through the through holes on the scintillation crystals 13 in the second detector unit 3 after neutron activation.
In some embodiments, the number of activation channels may be one or more. The number of the detection units is one or more sets which are the same as the number of the activation channels, and the detection units are selected according to the requirements of the production line on the detection speed, the detection precision and other performances of the equipment.
In this embodiment, the number of activation channels is preferably multiple (e.g., two as shown in fig. 1), and the number of detection units is preferably multiple sets. A plurality of sets of detection units are arranged in parallel, and a first detector unit 8 and a second detector unit 3 in each set of detection units are respectively arranged at the inlet end and the outlet end of the same activation channel. Second shields are respectively arranged between the first detector unit 8 and between the second detector unit 3 and the second detector unit 3 in two adjacent sets of detection units, the second shields are used for shielding mutual interference of gamma rays between the activation channels, and the second shields can be made of tungsten or lead, preferably tungsten.
In this embodiment, the number of the acquisition modules 4 is the same as that of the detection units, so that the acquisition paths of the acquisition modules are matched with the detection paths of the detection units, and the acquisition and conversion efficiency of the first signal and the second signal is improved.
In some embodiments, the system further comprises a feeding device and a discharging device.
Specifically, the feeding device is arranged at the inlet end of the first detector 8 and comprises a feeding frame 61 and a feeding transmission mechanism 71, the feeding frame 61, the feeding transmission mechanism 71 and the first detector units 8 are arranged linearly, the feeding transmission mechanism 71 is located between the feeding frame 61 and the first detector units 8, the feeding frame 61 is used for placing nuclear fuel rods to be detected, the feeding transmission mechanism 71 is used for introducing the nuclear fuel rods placed on the feeding frame 61 into an activation channel in a neutron activation unit through holes of scintillation crystals 13 in the first detector units 8 to perform neutron activation, and sending nuclear fuel assemblies subjected to neutron activation into the second detector units 3 to detect gamma ray characteristic information of the nuclear fuel rods subjected to pellet activation.
The blanking device is arranged at the outlet end of the second detector 3 and comprises a blanking frame 62 and a blanking transmission mechanism 72, the second detector units 3, the blanking transmission mechanism 72 and the blanking frame 62 are arranged linearly, the blanking transmission mechanism 72 is arranged between the blanking frame 62 and the second detector units 3, and the blanking transmission mechanism 72 is used for receiving the nuclear fuel rods detected by the second detector units 3 and conveying the nuclear fuel rods out of the blanking frame 62 so as to facilitate blanking.
The following details the operation of the nuclear fuel rod active detection system of the present embodiment, which are as follows:
and (3) detection process: standard nuclear fuel rods (i.e., nuclear fuel rods with known abundance) are placed on the loading frame 61, the standard nuclear fuel rods sequentially penetrate through the first detector units 8, the neutron activation units and the second detector units 3 at a uniform speed by using the loading transmission mechanism 71, then the standard nuclear fuel rods penetrating out of the second detector units 3 are transmitted to the unloading frame 62 by using the unloading transmission mechanism 72, during the period, each first detector in the first detector units 8 respectively detects to obtain a first signal of the standard nuclear fuel rods, and each second detector in the second detector units 3 respectively detects to obtain a second signal of the standard nuclear fuel rods.
Similarly, the nuclear fuel rod to be detected (i.e. the nuclear fuel rod with unknown abundance) is placed on the loading frame 61, the nuclear fuel rod to be detected sequentially and uniformly passes through the first detector unit 8, the neutron activation unit and the second detector unit by using the loading transmission mechanism 71, then the nuclear fuel rod to be detected which passes out of the second detector unit 3 is transmitted to the unloading frame 62 by using the unloading transmission mechanism 72, during the period, each first detector in the first detector unit 8 detects the first signal of the nuclear fuel rod to be detected respectively, and each second detector in the second detector unit 3 detects the second signal of the nuclear fuel rod to be detected respectively.
The data acquisition process comprises the following steps: the first signals of the standard nuclear fuel rods detected by each first detector are amplified by a first amplifier 10 and then transmitted to a first pulse amplitude analyzer 11 to be converted into first square wave signals of the standard nuclear fuel rods, a first data acquisition card 12 acquires the first square wave signals of the standard nuclear fuel rods to obtain a plurality of initial characteristic gamma ray counting curves (namely first counting curves) of the standard nuclear fuel rods before pellet activation, and the first counting curves are transmitted to a calculation module 5;
second signals of the standard nuclear fuel rods detected by the second detectors are amplified by the second amplifiers 16 and then transmitted to the second pulse amplitude analyzer 17 to be converted into second square wave signals of the standard nuclear fuel rods, the second data acquisition card 9 acquires the second square wave signals of the standard nuclear fuel rods to obtain a plurality of initial characteristic gamma ray counting curves (namely second counting curves) of the standard nuclear fuel rods after pellet activation, and the second counting curves are transmitted to the calculation module 5.
Similarly, the first signals of the nuclear fuel rods to be detected, which are detected by the first detectors, are amplified by the first amplifier 10 and then transmitted to the first pulse amplitude analyzer 11 to be converted into first square wave signals of the nuclear fuel rods to be detected, the first data acquisition card 12 acquires the first square wave signals of the nuclear fuel rods to be detected, so as to obtain initial characteristic gamma ray counting curves (i.e., third counting curves) of a plurality of nuclear fuel rods to be detected before activation of the nuclear fuel rods to be detected, and transmits the third counting curves to the calculation module 5;
the second signals of the nuclear fuel rods to be detected, which are detected by the second detectors, are amplified by the second amplifiers 16 and then transmitted to the second pulse amplitude analyzer 17 to be converted into second square wave signals of the nuclear fuel rods to be detected, the second data acquisition card 9 acquires the second square wave signals of the nuclear fuel rods to be detected, so as to obtain initial characteristic gamma ray counting curves (i.e. fourth counting curves) of the multiple nuclear fuel rods to be detected after pellet activation, and the fourth counting curves are transmitted to the calculation module 5.
And (3) data processing: firstly, the calculation module 5 respectively carries out shift accumulation on the received first counting curve to obtain a characteristic gamma ray counting curve before the standard nuclear fuel rod pellet is activated; shifting and accumulating the received second counting curve to obtain a characteristic gamma ray counting curve of the standard nuclear fuel rod after pellet activation; shifting and accumulating the received third counting curve to obtain a characteristic gamma ray counting curve of the nuclear fuel rod to be detected before pellet activation; and shifting and accumulating the received fourth counting curve to obtain a characteristic gamma-ray counting curve of the nuclear fuel rod to be detected after pellet activation.
Then, the calculation module 5 calculates an age correction coefficient based on the characteristic gamma-ray counting curve before the standard nuclear fuel rod pellet is activated and the characteristic gamma-ray counting curve after the standard nuclear fuel rod pellet is activated, or based on the characteristic gamma-ray counting curve before the nuclear fuel rod pellet to be detected is activated and the characteristic gamma-ray counting curve after the nuclear fuel rod pellet to be detected is activated, specifically:
respectively determining the head end and the tail end of a standard/to-be-detected nuclear fuel rod corresponding to the standard/to-be-detected nuclear fuel rod on a characteristic gamma-ray counting curve before the standard/to-be-detected nuclear fuel rod pellet is activated and a characteristic gamma-ray counting curve after the standard/to-be-detected nuclear fuel rod pellet is activated, setting the point corresponding to the head end of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve before the standard/to-be-detected nuclear fuel rod pellet is activated as the starting point of the characteristic gamma-ray counting curve before the standard/to-be-detected nuclear fuel rod pellet is activated and the point corresponding to the head end of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve after the standard/to-be-detected nuclear fuel rod pellet is activated, calculating the age correction coefficient based on the counting values of any two time points of the same position of the same standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve before the standard/to-be-detected nuclear fuel rod pellet is activated, and calculating the formula as follows:
F＝(C A1 -C A2 )/(C B1 -C B2 )
wherein F is an age correction factor, C A1 Is the count value of the first time point on the characteristic gamma ray count curve after pellet activation of the standard/to-be-tested nuclear fuel rod, C A2 Is the count value of the second time on the characteristic gamma-ray counting curve after pellet activation of the standard/nuclear fuel rod to be tested, C B1 Is the count value of the first time point on the characteristic gamma ray count curve before the pellet activation of the standard/to-be-tested nuclear fuel rod, C B2 Is the count value of the second time point on the characteristic gamma ray count curve before the pellet activation of the standard/to-be-tested nuclear fuel rod.
Then, the calculation module 5 calculates to obtain the final count curve of the standard nuclear fuel rod and the final count curve of the nuclear fuel rod to be detected based on the age correction coefficient, and specifically includes:
subtracting the product of the counting value of the same position of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve of the standard/to-be-detected nuclear fuel rod before the standard/to-be-detected nuclear fuel rod pellet is activated and the age correction coefficient from the counting value of each position of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve of the standard/to-be-detected nuclear fuel rod after the standard/to-be-detected nuclear fuel rod pellet is activated respectively to obtain the final counting value of the counting curve of each position of the standard/to-be-detected nuclear fuel rod, wherein the calculation formula of the final counting value of the counting curve is as follows:
C F ＝C AA －F×C BA
in the formula, C F Is the final count value of the count curve, C AA Is the count value on the characteristic gamma ray counting curve of the standard/nuclear fuel rod to be tested after pellet activation, C BA The counting value is the counting value on the characteristic gamma ray counting curve of the standard/nuclear fuel rod to be detected before pellet activation, and F is an age correction coefficient;
and respectively obtaining the final counting curve of the standard nuclear fuel rod and the final counting curve of the nuclear fuel rod to be detected based on the final counting value of the counting curve of each position of the standard/nuclear fuel rod to be detected.
Finally, the calculation module 5 calculates the pellet abundance of the nuclear fuel rod to be measured based on the final count curve of the standard nuclear fuel rod and the final count curve of the nuclear fuel rod to be measured, and specifically includes:
fitting the pellet abundance values of different positions of the standard nuclear fuel rod with a final counting curve of the standard nuclear fuel rod to obtain an abundance-counting relation equation of the standard nuclear fuel rod;
substituting each count value on the final count curve of the nuclear fuel rod to be detected into the abundance-count relation equation of the standard nuclear fuel rod to obtain an abundance curve of the nuclear fuel rod to be detected;
obtaining the abundance of the pellets at different positions of the nuclear fuel rod to be detected based on the abundance curve of the nuclear fuel rod to be detected;
comparing the abundance of the pellets at different positions of the nuclear fuel rod to be detected with the nuclear fuel rod detection technical indexes, and judging whether the abundance of the pellets of the fuel rod to be detected is qualified or not according to the comparison result.
The nuclear fuel rod active detection system of the embodiment can correct the pellet age of the nuclear fuel rod, eliminate the misjudgment caused by different pellet ages and prolong the service life compared with the prior art 252 Service life (more than 3 years) or reduction of Cf neutron source 252 The initial loading of the Cf neutron source is reduced to 1/4 of the original loading, so that the cost is reduced.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.

Claims (17)

1. An active detection method for a nuclear fuel rod, comprising:
obtaining a characteristic gamma-ray counting curve before the standard nuclear fuel rod pellet is activated and a characteristic gamma-ray counting curve after the standard nuclear fuel rod pellet is activated,
acquiring a characteristic gamma ray counting curve before the nuclear fuel rod to be detected is activated and a characteristic gamma ray counting curve after the nuclear fuel rod to be detected is activated;
calculating the characteristic gamma ray counting curve before the standard nuclear fuel rod pellet is activated and the characteristic gamma ray counting curve after the standard nuclear fuel rod pellet is activated to obtain the final counting curve of the standard nuclear fuel rod,
calculating a characteristic gamma ray counting curve before the nuclear fuel rod pellet to be detected is activated and a characteristic gamma ray counting curve after the nuclear fuel rod pellet to be detected is activated to obtain a final counting curve of the nuclear fuel rod to be detected;
and calculating to obtain the pellet abundance of the nuclear fuel rod to be detected based on the final counting curve of the standard nuclear fuel rod and the final counting curve of the nuclear fuel rod to be detected, and judging whether the pellet abundance of the nuclear fuel to be detected is qualified.
2. The nuclear fuel rod active detection method according to claim 1, wherein obtaining a characteristic gamma ray count curve before and after activation of a standard nuclear fuel rod pellet specifically comprises:
respectively collecting the characteristic gamma ray characteristic information of the standard nuclear fuel rod before pellet activation detected by a single detector to obtain a plurality of first counting curves,
respectively acquiring characteristic gamma ray characteristic information of the standard nuclear fuel rod after pellet activation, which is detected by a single detector, to obtain a plurality of second counting curves;
shifting and accumulating the first counting curves to obtain a characteristic gamma-ray counting curve of the standard nuclear fuel rod before pellet activation,
shifting and accumulating the plurality of second counting curves to obtain a characteristic gamma ray counting curve of the standard nuclear fuel rod after pellet activation;
the method for obtaining the characteristic gamma ray counting curve of the nuclear fuel rod to be detected before pellet activation and the characteristic gamma ray counting curve of the nuclear fuel rod to be detected after pellet activation specifically comprises the following steps:
respectively collecting the characteristic gamma ray characteristic information of the nuclear fuel rod to be detected before pellet activation detected by a single detector to obtain a plurality of third counting curves,
respectively collecting characteristic gamma ray characteristic information of the nuclear fuel rod to be detected after pellet activation detected by a single detector to obtain a plurality of fourth counting curves;
shifting and accumulating the third counting curves to obtain a characteristic gamma ray counting curve of the nuclear fuel rod to be tested before pellet activation,
and shifting and accumulating the plurality of fourth counting curves to obtain a characteristic gamma ray counting curve of the nuclear fuel rod to be detected after pellet activation.
3. The active nuclear fuel rod detection method according to claim 2, wherein the step of calculating a characteristic gamma ray count curve before the standard nuclear fuel rod pellet is activated and a characteristic gamma ray count curve after the standard nuclear fuel rod pellet is activated to obtain a final count curve of the standard nuclear fuel rod, and the step of calculating a characteristic gamma ray count curve before the nuclear fuel rod pellet to be detected is activated and a characteristic gamma ray count curve after the nuclear fuel rod pellet to be detected is activated to obtain a final count curve of the nuclear fuel rod to be detected includes:
calculating to obtain an age correction coefficient based on a characteristic gamma-ray counting curve before the standard nuclear fuel rod pellet is activated and a characteristic gamma-ray counting curve after the standard nuclear fuel rod pellet is activated, or based on a characteristic gamma-ray counting curve before the nuclear fuel rod pellet to be detected is activated and a characteristic gamma-ray counting curve after the nuclear fuel rod pellet to be detected is activated;
and calculating to obtain a final counting curve of the standard nuclear fuel rod and a final counting curve of the nuclear fuel rod to be detected based on the age correction coefficient.
4. The nuclear fuel rod active detection method according to claim 3, wherein the age correction coefficient is calculated based on a characteristic gamma ray count curve before activation of a standard nuclear fuel rod pellet and a characteristic gamma ray count curve after activation of the standard nuclear fuel rod pellet, or based on a characteristic gamma ray count curve before activation of a nuclear fuel rod pellet to be detected and a characteristic gamma ray count curve after activation of the nuclear fuel rod pellet to be detected, and specifically includes:
respectively determining the head end and the tail end of a standard/to-be-detected nuclear fuel rod corresponding to the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve before the standard/to-be-detected nuclear fuel rod pellet is activated and the characteristic gamma-ray counting curve after the standard/to-be-detected nuclear fuel rod pellet is activated, setting the point corresponding to the head end of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve before the standard/to-be-detected nuclear fuel rod pellet is activated as the starting point of the characteristic gamma-ray counting curve before the standard/to-be-detected nuclear fuel rod pellet is activated and setting the point corresponding to the head end of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve after the standard/to-be-detected nuclear fuel rod pellet is activated as the starting point of the characteristic gamma-ray counting curve after the standard/to-be-detected nuclear fuel rod pellet is activated,
based on the count values of any two time points of the same position of the same standard/nuclear fuel rod to be detected on the characteristic gamma-ray counting curve before the pellet activation of the standard/nuclear fuel rod to be detected and the characteristic gamma-ray counting curve after the pellet activation of the standard/nuclear fuel rod to be detected respectively, the age correction coefficient is obtained by calculation, and the calculation formula is as follows:
F＝(C A1 -C A2 )/(C B1 -C B2 )
wherein F is an age correction factor, C A1 Is the count value of the first time point on the characteristic gamma-ray count curve after the pellet activation of the standard/nuclear fuel rod to be tested, C A2 Is the count value of the second time on the characteristic gamma-ray counting curve after pellet activation of the standard/nuclear fuel rod to be tested, C B1 Is the count value of the first time point on the characteristic gamma ray count curve before the pellet activation of the standard/to-be-tested nuclear fuel rod, C B2 Is the count value of the second time point on the characteristic gamma ray count curve before the pellet activation of the standard/to-be-tested nuclear fuel rod.
5. The active nuclear fuel rod detection method according to claim 4, wherein obtaining the final count curve of the standard nuclear fuel rod and the final count curve of the nuclear fuel rod to be detected based on an age correction factor specifically includes:
subtracting the product of the counting value of the same position of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve of the standard/to-be-detected nuclear fuel rod before the standard/to-be-detected nuclear fuel rod pellet is activated and the age correction coefficient from the counting value of each position of the standard/to-be-detected nuclear fuel rod on the characteristic gamma-ray counting curve of the standard/to-be-detected nuclear fuel rod after the standard/to-be-detected nuclear fuel rod pellet is activated respectively to obtain the final counting value of the counting curve of each position of the standard/to-be-detected nuclear fuel rod, wherein the calculation formula of the final counting value of the counting curve is as follows:
C F ＝C AA －F×C BA
in the formula, C F To count the final count value of the curve, C AA Is the count value on the characteristic gamma ray counting curve of the standard/nuclear fuel rod to be tested after pellet activation, C BA The counting value is the counting value on the characteristic gamma ray counting curve of the standard/nuclear fuel rod to be detected before pellet activation, and F is an age correction coefficient;
and respectively obtaining the final counting curve of the standard nuclear fuel rod and the final counting curve of the nuclear fuel rod to be detected based on the final counting value of the counting curve of each position of the standard/nuclear fuel rod to be detected.
6. The active detection method of a nuclear fuel rod according to claim 5, wherein the calculating of the pellet abundance of the nuclear fuel rod to be detected based on the final count curve of the standard nuclear fuel rod and the final count curve of the nuclear fuel rod to be detected specifically includes:
fitting the pellet abundance values of different positions of the standard nuclear fuel rod with a final counting curve of the standard nuclear fuel rod to obtain an abundance-counting relation equation of the standard nuclear fuel rod;
substituting each count value on the final count curve of the nuclear fuel rod to be detected into an abundance-count relation equation of the standard nuclear fuel rod to obtain an abundance curve of the nuclear fuel rod to be detected;
obtaining the abundance of the pellets at different positions of the nuclear fuel rod to be detected based on the abundance curve of the nuclear fuel rod to be detected;
comparing the pellet abundance of the nuclear fuel rod to be detected at different positions with the nuclear fuel rod detection technical indexes, and judging whether the pellet abundance of the nuclear fuel rod to be detected is qualified or not according to the comparison result.
7. An active detection system of a nuclear fuel rod is characterized by comprising a neutron activation unit, a detection unit and a data acquisition and processing unit,
the neutron activation unit is used for performing neutron activation on the nuclear fuel rod pellets;
the detection unit comprises a first detector unit (8) and a second detector unit (3),
the first detector unit is arranged at the inlet end of the neutron activation unit, is connected with the data acquisition and processing unit and is used for detecting gamma ray characteristic information before the nuclear fuel rod pellet activation to obtain a first signal and transmitting the first signal to the data acquisition and processing unit,
the second detector unit is arranged at the outlet end of the neutron activation unit, is connected with the data acquisition and processing unit, and is used for detecting gamma ray characteristic information of the nuclear fuel rod after pellet activation to obtain a second signal and transmitting the second signal to the data acquisition and processing unit;
the data acquisition and processing unit is used for receiving the first signal and the second signal and determining a characteristic gamma-ray counting curve before the nuclear fuel rod pellet is activated and a characteristic gamma-ray counting curve after the nuclear fuel rod pellet is activated according to the first signal and the second signal, and,
calculating the characteristic gamma-ray counting curve before the nuclear fuel rod pellet is activated and the characteristic gamma-ray counting curve after the nuclear fuel rod pellet is activated to obtain the final counting curve of the nuclear fuel rod,
and calculating the pellet abundance of the nuclear fuel rod based on the final counting curve, and judging whether the pellet abundance of the nuclear fuel rod is qualified or not.
8. The nuclear fuel rod active detection system according to claim 7, characterized in that the data acquisition processing unit comprises an acquisition module (4) and a calculation module (5), the acquisition module comprising a first pulse amplitude analyzer (11), a first data acquisition card (12), a second pulse amplitude analyzer (17), and a second data acquisition card (9),
the first pulse amplitude analyzer is connected with the first detector unit and used for converting the first signal into a first square wave signal;
the first data acquisition card is respectively connected with the first pulse amplitude analyzer and the computing module and is used for acquiring a first square wave signal converted in the first pulse amplitude analyzer to obtain a characteristic gamma ray counting curve before the nuclear fuel rod pellet is activated and transmitting the characteristic gamma ray counting curve before the nuclear fuel rod pellet is activated to the computing module;
the second pulse amplitude analyzer is connected with the second detector unit and is used for converting the second signal into a second square wave signal;
the second data acquisition card is respectively connected with the second pulse amplitude analyzer and the computing module and is used for acquiring a second square wave signal converted in the second pulse amplitude analyzer to obtain a characteristic gamma ray counting curve of the activated nuclear fuel rod pellets and transmitting the characteristic gamma ray counting curve of the activated nuclear fuel rod pellets to the computing module;
the computing module is preset with the nuclear fuel rod detection technical index data and is used for computing a characteristic gamma ray counting curve before the nuclear fuel rod is activated and a characteristic gamma ray counting curve after the nuclear fuel rod is activated to obtain a final counting curve of the nuclear fuel rod, computing the pellet abundance of the nuclear fuel rod based on the final counting curve, comparing the pellet abundance of the nuclear fuel rod with the nuclear fuel rod detection technical index, and judging whether the pellet abundance of the nuclear fuel rod is qualified or not according to the comparison result.
9. The nuclear fuel rod active detection system of claim 8 wherein the acquisition module further comprises a first amplifier (10) and a second amplifier (16),
the first amplifier is respectively connected with the first detector unit and the first pulse amplitude analyzer and is used for amplifying the first signal detected by the first detector unit and transmitting the first signal to the first pulse amplitude analyzer, and the first pulse amplitude analyzer converts the amplified first signal into the first square wave signal;
the second amplifier is connected with the second detector unit and the second pulse amplitude analyzer respectively, and is used for amplifying the second signal detected by the second detector unit and transmitting the second signal to the second pulse amplitude analyzer, and the second pulse amplitude analyzer converts the amplified second signal into the second square wave signal.
10. The nuclear fuel rod active detection system of claim 8 wherein the first pulse amplitude analyzer (11) and the second pulse amplitude analyzer (17) are one of a comparator, a single pass pulse amplitude analyzer, and a multi pass pulse amplitude analyzer,
wherein, when the first pulse amplitude analyzer is a single-channel pulse amplitude analyzer, the lower threshold of the single-channel pulse amplitude analyzer is a signal generated by 250keV gamma rays, and the upper threshold of the single-channel pulse amplitude analyzer is a signal generated by 1.1MeV gamma rays,
when the second pulse amplitude analyzer is a single-channel pulse amplitude analyzer, the lower threshold of the single-channel pulse amplitude analyzer is a signal corresponding to the maximum noise of the second detector unit, the upper threshold of the single-channel pulse amplitude analyzer is a signal generated by 2.5MeV gamma rays,
the multichannel pulse amplitude analyzer can receive gamma rays with energy range larger than 2.5MeV.
11. The nuclear fuel rod active detection system of claim 7 wherein the first detector cell includes a number of first detectors, the second detector cell includes a number of second detectors, the first and second detectors each include a scintillation crystal (13), a photoelectric conversion device, a preamplifier, and a housing (14),
the scintillation crystal and the photoelectric conversion device are both arranged in the shell, through holes are formed in the scintillation crystal and the shell, the through holes are used for nuclear fuel rods to pass through, the scintillation crystal is used for absorbing gamma rays emitted by nuclear fuel rod pellets when the nuclear fuel rods pass through the through holes and then emitting optical signals, and the photoelectric conversion device is used for converting the optical signals emitted by the scintillation crystal into electrical signals and outputting the electrical signals;
the preamplifier is connected to the photoelectric conversion device, and is configured to receive and amplify the electrical signal to obtain the first signal/the second signal.
12. The active nuclear fuel rod testing system of claim 11, wherein the number of the first probes is two or more, each of the first probes is arranged in a straight line at an inlet end of the neutron activation cell, each of the first probes is used for detecting gamma-ray characteristic information of the nuclear fuel rod before pellet activation, and the first signal includes the gamma-ray characteristic information of the nuclear fuel rod before pellet activation detected by each of the first probes;
the number of the second detectors is more than two, each second detector is linearly arranged at the outlet end of the neutron activation unit and is respectively used for detecting gamma-ray characteristic information of the activated nuclear fuel rod pellets, and the second signals comprise the gamma-ray characteristic information of the activated nuclear fuel rod pellets, which is respectively detected by each second detector.
13. The nuclear fuel rod active detection system of claim 12, wherein the scintillation crystal has a detection efficiency of not less than 75% for 1.1MeV gamma rays, and the thickness of the scintillation crystal is 1-2.5 times the height of the nuclear fuel rod pellet in the length direction of the nuclear fuel rod;
the photoelectric conversion device is a photomultiplier or a silicon photomultiplier.
14. The nuclear fuel rod active detection system of claim 13, wherein the scintillation crystal is made of one of Bismuth Germanate (BGO), cesium iodide (CsI), sodium iodide (NaI), and Cadmium Zinc Telluride (CZT).
15. The nuclear fuel rod active detection system of claim 13 wherein the first and second probes each further comprise a first shield (15),
the first shielding body is arranged outside the shell and used for shielding gamma rays below 1.1MeV,
the first shielding body is provided with an opening, and the position of the opening is concentric with the through hole in the scintillation crystal.
16. Nuclear fuel rod active detection system according to claim 15, wherein the neutron activation unit comprises a neutron source (1), a neutron shield (2),
the neutron source is arranged in the neutron shielding body, an activation channel is arranged on the neutron shielding body, and the position of the activation channel is concentric with the through holes of the scintillation crystals in the first detector unit and the second detector unit.
17. The nuclear fuel rod active detection system of claim 16, wherein the number of the activation channels is a plurality of the sets, the number of the probe cells is a plurality of sets equal to the number of the activation channels,
a plurality of sets of detection units are arranged in parallel, and a first detector unit and a second detector unit in each set of detection units are respectively arranged at the inlet end and the outlet end of the same activation channel;
and second shielding bodies are respectively arranged between the first detector unit and between the second detector unit and the second detector unit in the two adjacent sets of detection units, and are used for shielding mutual interference of gamma rays between the activation channels.
CN202210811234.9A 2022-07-11 2022-07-11 Nuclear fuel rod active detection method and system Pending CN115144426A (en)

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