阅读说明：本技术 一种堆外探测器中子灵敏度校准装置及方法 (Device and method for calibrating neutron sensitivity of out-of-pile detector ) 是由 任敏 杨毓枢 王旭 张劲松 钟军 陈嘉浪 刘吉珍 漆明森 程瑛 江常玉 王军成 于 2021-10-14 设计创作，主要内容包括：本发明公开了一种堆外探测器中子灵敏度校准装置及方法,该装置包括线中子源、贮源容器、屏蔽体、慢化体、探测器定位孔和校准孔道；线中子源用于产生快中子；屏蔽体用于该装置在工作状态时屏蔽线中子源；慢化体用于将线中子源产生的快中子慢化成热中子；校准孔道作为热中子形成的热中子场所在的空间,用于反射热中子提高热中子注量率；堆外探测器通过探测器定位孔放置于该校准装置的热中子场中,且探测器根据检定人员通过控制系统发出的指令可沿探测器孔道上下移动。本发明装置操作简便,是目前国内唯一堆外探测器中子灵敏度校准装置,可以产生符合要求的热中子场用于中子灵敏度的校准,为反应堆的安全运行提供了可靠的计量保证。(The invention discloses a neutron sensitivity calibration device and method for an out-of-pile detector, wherein the device comprises a linear neutron source, a source storage container, a shielding body, a moderating body, a detector positioning hole and a calibration pore channel; the linear neutron source is used for generating fast neutrons; the shielding body is used for shielding the line neutron source when the device is in a working state; the moderating body is used for moderating fast neutrons generated by the line neutron source into thermal neutrons; the calibration pore channel is used as a space where a thermal neutron field formed by thermal neutrons is located and used for reflecting the thermal neutrons to improve the thermal neutron fluence rate; the out-of-pile detector is placed in a thermal neutron field of the calibrating device through a detector positioning hole, and the detector can move up and down along a detector pore channel according to an instruction sent by a verification person through a control system. The device is simple and convenient to operate, is the only neutron sensitivity calibration device for the detectors outside the reactor at home at present, can generate thermal neutron fields meeting the requirements for calibrating the neutron sensitivity, and provides reliable measurement guarantee for the safe operation of the reactor.)

1. An off-stack detector neutron sensitivity calibration device, characterized in that, this calibration device includes: the device comprises a linear neutron source (12), a source storage container (13), a shielding body (2), a slowing body (3), a detector positioning hole (5) and a calibration pore channel; when the calibration device is in a non-working state, the line neutron source (12) is positioned in the source storage container (13); the storage source container (13) is arranged in the underground deep pit; the detector positioning hole (5) is formed in the top of the calibration pore channel;

the line neutron source (12) is used for generating fast neutrons;

the shielding body (2) is used for shielding the line neutron source (12) when the calibration device is in a working state, and reducing the neutron radiation level;

the moderating body (3) is used for moderating fast neutrons generated by the line neutron source (12) into thermal neutrons;

the calibration pore channel is used as a space where a thermal neutron field formed by thermal neutrons is located and used for reflecting the thermal neutrons to improve the thermal neutron fluence rate;

the out-of-pile detector is placed in a thermal neutron field of the calibration device through a detector positioning hole (5), and the detector can move up and down along a detector pore channel according to an instruction sent by a control system; the calibration device realizes that the uniformity of the thermal neutron field fluence rate in the axial 1-meter range of the detector is less than 20%, and the thermal neutron fluence rate at the position of the detector is changed by automatically changing the distance between the detector and the linear neutron source (12).

2. The device for calibrating the neutron sensitivity of the out-of-pile detector according to claim 1, characterized by further comprising a neutron source lifting device (1), wherein the neutron source lifting device (1) is used for lifting the linear neutron source (12), lifting the linear neutron source (12) to a working position when working, and lowering the linear neutron source (12) into the source storage container (13) after the working is completed.

3. The off-stack detector neutron sensitivity calibration device according to claim 1, wherein the calibration tunnel comprises a calibration channel upper plate (4), a calibration channel side plate (8), a calibration channel bottom plate (11) and a detector back plate (9), and a cavity formed by the calibration channel upper plate (4), the calibration channel side plate (8), the calibration channel bottom plate (11) and the detector back plate (9) is used for reflecting thermal neutrons.

4. The off-stack detector neutron sensitivity calibration device according to claim 1, further comprising a detector fixing device and a guide groove (7), wherein the detector fixing device is used for fixing the detector; the detector fixing device comprises a detector positioning slide block (6) and a detector displacement positioning device (10), and the detector positioning slide block (6), the detector displacement positioning device (10) and the detector positioning hole (5) are on the same vertical line;

the guide groove (7) is arranged on the side edge of the detector fixing device, and the detector moves up and down along the detector pore channel on the guide groove (7).

5. The off-stack detector neutron sensitivity calibration device according to claim 4, characterized in that the displacement precision of the detector displacement positioning device (10) is less than or equal to 0.5 mm.

6. The off-stack detector neutron sensitivity calibration device of claim 1, wherein the moderator is cylindrical.

7. The device of claim 1, wherein the linear neutron source comprises 20 linear neutron sources with an activity of 1.85 x 10¹⁰Of Bq²⁴¹Am-Be point neutron sources are arranged in a straight line, and²⁴¹the Am-Be point neutron source adopts a 'middle sparse and two dense ends' arrangement mode in a source tube.

8. The device for calibrating neutron sensitivity of an out-of-pile detector according to claim 1, wherein the calibration pore is used as a space where a thermal neutron field formed by thermal neutrons is located, and the space is cylindrical in shape and has the size of phi 80mm x 1000 mm.

9. The neutron sensitivity calibration device of claim 1, wherein the thermal neutron field fluence rate is (8.91-1.12 x 10)⁴)cm^-2·s^-1Wherein the energy of thermal neutrons is less than or equal to 0.5 eV.

10. A method for calibrating the neutron sensitivity of an out-of-stack detector, which is applied to the device for calibrating the neutron sensitivity of the out-of-stack detector as claimed in any one of claims 1 to 9; the calibration method comprises the following steps:

s1: measuring the thermal neutron fluence value phi at the calibration position by a gold activated sheet method;

s2: placing the detector on a detector displacement positioning device, and moving the detector to a calibration position to obtain a reading N of the detector at the moment;

s3: sensitivity by neutronsA calculation formula is used for calculating the neutron sensitivity S of the detector at the thermal neutron fluence rate value; wherein, the neutron sensitivity calculation formula is as follows:

s4: repeating the steps S1-S3 at other calibration positions can obtain the neutron sensitivity of the detector at other thermal neutron fluence values.

Technical Field

The invention relates to the technical field of ionizing radiation measurement, in particular to a neutron sensitivity calibration device and method for an out-of-pile detector.

Background

In the design of nuclear reactor, the radiation detector (or called out-of-core detector) of nuclear measurement system is arranged at different positions outside the reactor to monitor the state of the reactor core, which is also a common method for on-line measurement of the neutron fluence rate level in the reactor core. It has two main functions: an operation function and a safety function. The operation function means that the neutron fluence rate level and the variation condition of the fluence rate in the nuclear reactor can be given at any time to guide the startup and the operation of the nuclear reactor. The safety function is to provide accident shutdown and alarm signals, so that the nuclear reactor control operators can take effective measures in time, abnormal operation or accident enlargement of the nuclear reactor is prevented, and the safety of the nuclear reactor operation, personnel and environment is ensured. Therefore, the accuracy of the measurement by the out-of-pile detector will have a great influence on the safety of the reactor.

For the development and production of radiation detectors for nuclear detection systems, the standards which are already established in China comprise: the radiation detector for the nuclear test system of the GJB3613-99 submarine nuclear power device is in a general specification, the radiation detector for the nuclear test system of the GJB3613/1-99 submarine nuclear power device is in a general specification and the neutron proportional counter tube is in a detailed specification, the radiation detector for the nuclear test system of the GJB3613/2-99 submarine nuclear power device is in a general specification and the neutron ionization chamber is in a detailed specification, and the radiation detector for the nuclear test system of the GJB3613/3-99 submarine nuclear power device is in a general specification and the fission ionization chamber is in a detailed specification. These standards specify radiation detectors for nuclear power plant nuclear measurement systems: technical requirements, quality assurance regulations, delivery preparation and precautions for neutron proportional counter tubes, neutron ionization chambers, fission ionization chambers, and the like. For neutron sensitivity, only providing neutron sensitivity parameters when the detector is shipped from the factory is provided, and how to calibrate the neutron sensitivity is not described. Because the current country does not establish the calibration standard of neutron sensitivity of the detector, in the XX in the active generation, the detectors of the same type have great difference (about several times) of measurement results under the same use condition, which brings difficulty for operating personnel to correctly judge the operation condition of the reactor, thereby influencing the fighting capacity of XXX and being not beneficial to the safety of the nuclear reactor. Therefore, it is necessary to develop a neutron sensitivity calibration technology research of the radiation detector for the XX nuclear power plant nuclear measurement system, establish a neutron sensitivity calibration standard of the out-of-pile detector, and ensure the accuracy, reliability and uniformity of the measurement data of the XX nuclear power plant nuclear measurement system.

Radiation detectors for nuclear instrumentation systems need to be replaced periodically during the service life of the reactor. Due to the fact that the sensitivity calibration standards of the detectors are not available, when the detectors are replaced, the sensitivity data of the detectors cannot be provided, and the detectors cannot display accurate values of thermal neutron fluence rates outside the reactor. Therefore, it is necessary to design a calibration device to calibrate the neutron sensitivity of the detector, so as to provide a metering guarantee for the safe operation of the reactor.

Disclosure of Invention

The invention aims to provide a device and a method for calibrating neutron sensitivity of an out-of-reactor detector, wherein the device can generate a thermal neutron field with a certain thermal neutron fluence rate and certain uniformity meeting certain requirements, and provides a metering guarantee for safe operation of a reactor.

The invention is realized by the following technical scheme:

in a first aspect, the present invention provides an off-stack detector neutron sensitivity calibration apparatus, comprising: the device comprises a linear neutron source, a source storage container, a shielding body, a slowing body, a detector positioning hole and a calibration pore channel; when the calibration device is in a non-working state, the line neutron source is positioned in the source storage container; the storage source container is arranged in the underground pit, and concrete around the pit can be used for radiation protection; the detector positioning hole is formed in the top of the calibration pore channel;

the line neutron source is used for generating fast neutrons;

the shielding body is used for shielding the line neutron source when the calibration device is in a working state, so that the neutron radiation level is reduced;

the moderating body is used for moderating fast neutrons generated by the line neutron source into thermal neutrons;

the calibration pore channel is used as a space where a thermal neutron field formed by thermal neutrons is located and used for reflecting the thermal neutrons to improve the thermal neutron fluence rate;

the ex-pile detector is placed in a thermal neutron field (namely a calibration pore channel) of the calibration device through a detector positioning hole, and the detector can move up and down along the detector pore channel according to an instruction sent by a verification personnel through a control system;

the calibration device realizes that the uniformity of the thermal neutron field fluence rate in the axial 1 meter (m) range of the detector is less than 20%, and the thermal neutron fluence rate at the position can be changed by automatically changing the distance between the detector and the linear neutron source.

The working principle is as follows: the calibration device comprises a linear neutron source, a source storage container, a shielding body, a slowing body, a calibration pore channel, a neutron source lifting device, a detector displacement positioning device, a computer, a control system and the like. Under the front dike which ensures the radiation safety and convenient operation, the uniformity of the thermal neutron field fluence rate within 1m of the axial direction of the detector is less than 20 percent, and the thermal neutron fluence rate at the position of the detector can be changed by automatically changing the distance between the detector and the linear neutron source.

The calibration device of the invention has the following characteristics:

(1) thermal neutron field fluence rate: (8.91-1.12X 10⁴)cm^-2·s^-1(neutron energy is less than or equal to 0.5 eV);

(2) displacement precision of the detector displacement positioning device: less than or equal to 0.5 mm;

(3) in the case of a loaded line neutron source, the laboratory radiation level is less than 1.5 μ Sv/h.

The calibrating device can generate a low-fluence-rate thermal neutron field which is very similar to the working environment of the detector outside the reactor, realizes the calibration of the neutron sensitivity of the detector outside the reactor for the first time in China, and can utilize the device to carry out deep research on phenomena such as thermal neutron field distortion and the like, so that the measuring result of the detector is more accurate, and reliable metering guarantee is provided for the safe operation of the reactor.

The system further comprises a neutron source lifting device, wherein the neutron source lifting device is used for lifting a linear neutron source, lifting the linear neutron source to a working position during working, and lowering the linear neutron source into a source storage container after working is finished; ensuring that the line neutron source is located in the source container when the calibration device is in a non-working state.

Further, the calibration pore comprises a calibration channel upper plate, a calibration channel side plate, a calibration channel bottom plate and a detector back plate, wherein a cavity formed by the calibration channel upper plate, the calibration channel side plate, the calibration channel bottom plate and the detector back plate is used for reflecting thermal neutrons.

The device further comprises a detector fixing device and a guide groove, wherein the detector fixing device is used for fixing the detector; the detector fixing device comprises a detector positioning slide block and a detector displacement positioning device, and the detector positioning slide block, the detector displacement positioning device and the detector positioning hole are on the same vertical line;

the guide groove is arranged on the side edge of the detector fixing device, and the detector moves up and down along the detector pore channel on the guide groove.

Furthermore, the displacement precision of the detector displacement positioning device is less than or equal to 0.5mm (namely less than or equal to 0.5 mm).

Further, the moderator is cylindrical.

Further, the line neutron source consists of 20 particles with the activity of 1.85 multiplied by 10¹⁰Of Bq²⁴¹Am-Be point neutron sources are arranged in a straight line, and²⁴¹the Am-Be point neutron source adopts a 'middle sparse and two dense ends' arrangement mode in a source tube.

Furthermore, the calibration pore channel is used as a space where a thermal neutron field formed by thermal neutrons is located, the space is cylindrical in shape, and the size is phi 80mm multiplied by 1000 mm.

Further, the fluence rate of the thermal neutron field is (8.91-1.12 multiplied by 10)⁴)cm^-2·s^-1Wherein the energy of thermal neutrons is less than or equal to 0.5 eV.

Furthermore, the moderating body, the component (the upper plate of the calibration channel, the bottom plate of the calibration channel, the side plate of the calibration channel and the back plate of the detector) for reflecting thermal neutrons and the shielding body are made of polyethylene materials, moderating and absorption effects of polyethylene and water on neutrons are similar, the mechanical performance is good, and maintenance cost of the device can be greatly reduced.

In a second aspect, the present invention further provides a method for calibrating the neutron sensitivity of an out-of-reactor detector, which is applied to the device for calibrating the neutron sensitivity of an out-of-reactor detector; the calibration method comprises the following steps:

s1: the thermal neutron fluence value phi (unit: cm) at the position of the calibration position is accurately measured by a gold activation sheet method^-2·s^-1)；

S2: placing the detector on a detector displacement positioning device, and moving the detector to a calibration position to obtain the reading N (unit: A or cps) of the detector at the moment;

s3: calculating the neutron sensitivity S (unit: cps/cm) of the detector at the thermal neutron fluence value by using a neutron sensitivity calculation formula^-2·s^-1Or A/cm^-2·s^-1) (ii) a Wherein, the neutron sensitivity calculation formula is as follows:

s4: repeating the steps S1-S3 at other calibration positions can obtain the neutron sensitivity of the detector at other thermal neutron fluence values.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. the invention has the advantages that: (1) thermal neutron field fluence rate: (8.91-1.12X 10⁴)cm^-2·s^-1(neutron energy is less than or equal to 0.5 eV); (2) displacement precision of the detector displacement positioning device: less than or equal to 0.5 mm; (3) in the case of a loaded line neutron source, the laboratory radiation level is less than 1.5 μ Sv/h.

2. The calibration device can generate a low-fluence rate thermal neutron field which is very similar to the working environment of the off-reactor detector, the neutron sensitivity calibration device of the off-reactor detector is created, the neutron sensitivity calibration of the off-reactor detector is realized for the first time domestically by using the calibration device, and the phenomena of thermal neutron field distortion and the like can be deeply researched by using the device, so that the measurement result of the detector is more accurate, and reliable measurement guarantee is provided for the safe operation of a reactor.

3. The calibration device is simple and convenient to operate, is the only neutron sensitivity calibration device for the detectors outside the reactor at present, and tests prove that the device can generate thermal neutron fields meeting requirements for calibrating the neutron sensitivity, thereby providing reliable measurement guarantee for the safe operation of the reactor.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

fig. 1 is a schematic structural diagram of a neutron sensitivity calibration device of an out-of-pile detector according to the invention.

Reference numbers and corresponding part names:

the method comprises the following steps of 1-a neutron source lifting device, 2-a shielding body, 3-a slowing body, 4-a calibration channel upper plate, 5-a detector positioning hole, 6-a detector positioning slide block, 7-a guide groove, 8-a calibration channel side plate, 9-a detector back plate, 10-a detector displacement positioning device, 11-a calibration channel bottom plate, 12-a line neutron source and 13-a source storage container.

Detailed Description

Hereinafter, the term "comprising" or "may include" used in various embodiments of the present invention indicates the presence of the invented function, operation or element, and does not limit the addition of one or more functions, operations or elements. Furthermore, as used in various embodiments of the present invention, the terms "comprises," "comprising," "includes," "including," "has," "having" and their derivatives are intended to mean that the specified features, numbers, steps, operations, elements, components, or combinations of the foregoing, are only meant to indicate that a particular feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as first excluding the existence of, or adding to the possibility of, one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing.

In various embodiments of the invention, the expression "or" at least one of a or/and B "includes any or all combinations of the words listed simultaneously. For example, the expression "a or B" or "at least one of a or/and B" may include a, may include B, or may include both a and B.

Expressions (such as "first", "second", and the like) used in various embodiments of the present invention may modify various constituent elements in various embodiments, but may not limit the respective constituent elements. For example, the above description does not limit the order and/or importance of the elements described. The foregoing description is for the purpose of distinguishing one element from another. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of various embodiments of the present invention.

It should be noted that: if it is described that one constituent element is "connected" to another constituent element, the first constituent element may be directly connected to the second constituent element, and a third constituent element may be "connected" between the first constituent element and the second constituent element. In contrast, when one constituent element is "directly connected" to another constituent element, it is understood that there is no third constituent element between the first constituent element and the second constituent element.

The terminology used in the various embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the various embodiments of the invention. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments of the present invention belong. The terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning that is consistent with their contextual meaning in the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein in various embodiments of the present invention.

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.

Example 1

As shown in fig. 1, the present invention provides a neutron sensitivity calibration apparatus for an out-of-stack detector, which includes: the detector comprises a linear neutron source 12, a source storage container 13, a shielding body 2, a slowing body 3, a detector positioning hole 5 and a calibration pore channel; in the rest state of the calibration device, the line neutron source 12 is located in the source container 13; the storage source container 13 is arranged in the underground pit, and concrete around the pit can be used for radiation protection; the detector positioning hole 5 is arranged at the top of the calibration pore channel;

the line neutron source 12 is used for generating fast neutrons;

the shielding body 2 is used for shielding the line neutron source 12 when the calibration device is in a working state, so that the neutron radiation level is reduced;

the moderating body 3 is used for moderating fast neutrons generated by the line neutron source 12 into thermal neutrons;

the calibration pore channel is used as a space where a thermal neutron field formed by thermal neutrons is located and used for reflecting the thermal neutrons to improve the thermal neutron fluence rate;

the ex-pile detector is placed in a thermal neutron field (namely a calibration pore channel) of the calibration device through a detector positioning hole 5, and the detector can move up and down along the detector pore channel according to an instruction sent by a verification worker through a control system;

the calibration device realizes that the uniformity of the thermal neutron field fluence rate in the axial 1 meter (m) range of the detector is less than 20%, and the thermal neutron fluence rate at the position can be changed by automatically changing the distance between the detector and the linear neutron source 12.

In order to further explain the embodiment, the system further comprises a neutron source lifting device 1, wherein the neutron source lifting device 1 is used for lifting the linear neutron source 12, lifting the linear neutron source 12 to a working position during working, and lowering the linear neutron source 12 into a source storage container 13 after working is finished; to ensure that the line neutron source 12 is located in the source container 13 when the calibration apparatus is not in operation.

For further explanation of the present embodiment, the calibration tunnel includes a calibration channel upper plate 4, a calibration channel side plate 8, a calibration channel bottom plate 11, and a detector back plate 9, and a cavity formed by the calibration channel upper plate 4, the calibration channel side plate 8, the calibration channel bottom plate 11, and the detector back plate 9 is used for reflecting thermal neutrons.

For further explanation of the present embodiment, the present invention further includes a probe fixing device for fixing the probe and a guide groove 7; the detector fixing device comprises a detector positioning slide block 6 and a detector displacement positioning device 10, and the detector positioning slide block 6, the detector displacement positioning device 10 and the detector positioning hole 5 are on the same vertical line;

the guide groove 7 is arranged on the side edge of the detector fixing device, and the detector moves up and down on the guide groove 7 along the detector pore channel.

The calibration device aims to establish a thermal neutron field with a fluence rate and uniformity meeting certain requirements. Thermal neutron source (20 activity is 1.85X 10)¹⁰Of Bq²⁴¹Am-Be point neutron sources are arranged in a straight line) to generate fast neutrons passing through a circleAnd (4) obtaining the columnar moderator after moderating. The thermal neutron field is positioned in the sleeve of the detector positioning device, the space shape is a cylinder, and the size is phi 80mm multiplied by 1000 mm.²⁴¹The half-life of the Am-Be neutron source is 432 years, and the stability of the thermal neutron field in the service period of the device can Be ensured. The moderating body, the component (the upper plate of the calibration channel, the bottom plate of the calibration channel, the side plate of the calibration channel and the back plate of the detector) for reflecting thermal neutrons and the shielding body are made of polyethylene materials, moderating and absorption effects of polyethylene and water on neutrons are similar, the mechanical performance is good, and the maintenance cost of the device can be greatly reduced. The moderator has two specifications of 5cm thickness and 8cm thickness, and is used for increasing the upper limit of the heat middle field fluence rate and reducing the lower limit thereof. In order to improve the axial uniformity of the thermal neutron field, the following measures are mainly adopted: firstly, the²⁴¹The Am-Be point neutron source adopts a 'middle sparse two ends dense' arrangement mode in a source tube, and reflects thermal neutrons through a calibration channel upper plate and a calibration channel bottom plate. The reflecting action of the side plates of the calibration channel and the back plate of the detector on neutrons can obviously improve the thermal neutron fluence rate level and improve the circumferential thermal neutron field uniformity of the detector, so that the actual working environment of the thermal neutron field is more similar to that of the detector. The source container is located in an underground pit, and concrete around the pit can be used for radiation protection. Half of the calibrating device is positioned in the pit, so that the distance between the top and the ground is 90cm, and a worker can conveniently load and unload the detector. The neutron source lifting device is used for lifting the linear neutron source to a working position during working and lowering the linear neutron source into the source storage container after the work is finished. The detector displacement positioning device is used for automatically changing the distance between the detector and the linear neutron source, so that the size of the thermal neutron field is changed.

The calibration device comprises a linear neutron source, a source storage container, a shielding body, a slowing body, a calibration pore channel, a neutron source lifting device, a detector displacement positioning device, a computer, a control system and the like. Under the front dike which ensures the radiation safety and convenient operation, the uniformity of the thermal neutron field fluence rate within 1m of the axial direction of the detector is less than 20 percent, and the thermal neutron fluence rate at the position of the detector can be changed by automatically changing the distance between the detector and the linear neutron source.

The calibration device of the invention has the following characteristics:

(1) thermal neutron field fluence rate: (8.91-1.12X 10⁴)cm^-2·s^-1(neutron energy is less than or equal to 0.5 eV);

(2) displacement precision of the detector displacement positioning device: less than or equal to 0.5 mm;

(3) in the case of a loaded line neutron source, the laboratory radiation level is less than 1.5 μ Sv/h.

The calibration device can generate a low-fluence rate thermal neutron field which is very similar to the working environment of the off-reactor detector, the neutron sensitivity calibration device of the off-reactor detector is created, the neutron sensitivity calibration of the off-reactor detector is realized for the first time domestically by using the calibration device, and the phenomena of thermal neutron field distortion and the like can be deeply researched by using the device, so that the measurement result of the detector is more accurate, and reliable measurement guarantee is provided for the safe operation of a reactor.

The calibrating device is simple and convenient to operate, is the only off-reactor detector neutron sensitivity calibrating device in China at present, and tests prove that the device can generate a thermal neutron field meeting requirements for calibrating the neutron sensitivity, so that reliable metering guarantee is provided for safe operation of a reactor.

Example 2

As shown in fig. 1, the present embodiment is different from embodiment 1 in that the present embodiment provides a method for calibrating neutron sensitivity of an out-of-stack detector, and the method is applied to a device for calibrating neutron sensitivity of an out-of-stack detector described in embodiment 1; the calibration method comprises the following steps:

s1: the thermal neutron fluence value phi (unit: cm) at the position of the calibration position is accurately measured by a gold activation sheet method^-2·s^-1)；

S2: placing the detector on a detector displacement positioning device, and moving the detector to a calibration position to obtain the reading N (unit: A or cps) of the detector at the moment;

s3: calculating the neutron sensitivity S (unit: cps/cm) of the detector at the thermal neutron fluence value by using a neutron sensitivity calculation formula^-2·s^-1Or A/cm^-2·s^-1) (ii) a Wherein, the neutron sensitivity calculation formula is as follows:

s4: repeating the steps S1-S3 at other calibration positions can obtain the neutron sensitivity of the detector at other thermal neutron fluence values.

The calibration device of the embodiment 1 is simple and convenient to operate, is the only off-reactor detector neutron sensitivity calibration device in China at present, and tests prove that the device can generate a thermal neutron field meeting requirements for calibrating the neutron sensitivity.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.