A fast neutron multiplicity measuring device with active and passive measuring functions

Abstract

The application relates to the field of non-destructive measurement and verification and authentication of nuclear material properties, and particularly relates to a fast neutron multiplicity measuring device with active and passive measuring functions. The fast neutron multiplicity measuring device with active and passive measuring functions comprises a fast neutron detector, a sample container, a neutron generator and a neutron source shielding cone. The fast neutron detector is in a ring array structure. The sample container is arranged in a central measuring area. The neutron generator is arranged at the end of the ring array. The neutron generator has an alpha timing function. The neutron source shielding cone is arranged between the neutron generator and the fast neutron detector. The fast neutron multiplicity measuring device can realize the functions of active and passive fast neutron multiplicity measurement without changing the existing components of the device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of non-destructive measurement and verification of nuclear material properties, and particularly relates to a fast neutron multiplicity measurement device with active and passive measurement functions. BACKGROUND

[0002] A fast neutron multiplicity measurement device generally comprises a plurality of fast neutron detectors (such as liquid scintillation detectors) with neutron gamma discrimination arranged in a ring or spherical array to form a detector array, and the measurement device can measure the fast neutron multiplicity of a nuclear material sample at the center of the array. According to the fast neutron multiplicity measurement data, the mass properties of the measured nuclear material can be further analyzed.

[0003] From the measurement method, there are active and passive methods. The active method requires an external neutron source (such as an Am-Li neutron source) to inject a nuclear material sample and induce nuclear material fission, and the measurement device measures the neutron multiplicity of the external source induced fission, mainly for measuring uranium materials. The passive method directly measures the neutron multiplicity of the spontaneous fission of the nuclear material, mainly for measuring plutonium materials.

[0004] Corresponding to fast neutrons, there is also a thermal neutron multiplicity measurement device, which has the significant feature of using polyethylene or other slowing-down materials to slow down the leakage neutrons of the nuclear material, and arranging He-3 or similar thermal neutron detectors in the slowing-down material to measure the thermal neutron multiplicity after slowing down.

[0005] The existing active fast neutron multiplicity measurement device is based on an Am-Li neutron source. Due to the deep penetration characteristics of the neutron source, it cannot be effectively shielded in the limited space of the fast neutron multiplicity measurement device. The interference of the Am-Li neutron source cannot be directly used for passive measurement, so the Am-Li neutron source needs to be removed when passive measurement is performed. SUMMARY

[0006] The purpose of the present application is to provide a fast neutron multiplicity measurement device with active and passive measurement functions, which can simultaneously have active and passive measurement functions without increasing or reducing the components of the measurement device.

[0007] To solve the above problems, the present application provides a fast neutron multiplicity measurement device with active and passive measurement functions, comprising a fast neutron detector, a sample container, a neutron generator, and a neutron source shielding cone.

[0008] The fast neutron detector is in a ring array structure; the sample container is arranged in the center measurement area.

[0009] The neutron generator is arranged at the end of the ring array; the neutron generator has an alpha timing function.

[0010] The neutron source shielding cone is arranged between the neutron generator and the fast neutron detector.

[0011] In some embodiments, the annular array structure of the fast neutron detector is a single ring arrangement or a multi-ring arrangement, each ring being composed of a plurality of detectors arranged uniformly.

[0012] In some embodiments, the number of rings and the number of detectors in each ring of the annular array structure of the fast neutron detector are determined by the total neutron detection efficiency.

[0013] In some embodiments, the inner cavity diameter of the annular array structure of the fast neutron detector is determined by the maximum outer diameter of the sample to be measured.

[0014] In some embodiments, the neutron generator is a DD reaction neutron generator or a DT reaction neutron generator, and has an alpha timing function.

[0015] In some embodiments, the neutron generator is arranged at one end of the annular array.

[0016] In some embodiments, the target point of the neutron generator is arranged on the central axis of the annular array.

[0017] In some embodiments, the distance between the target point and the center of the detector array is determined by the following equation: h = d / arctg (θ1) / 2;

[0018] where h is the distance between the target point and the center of the detector array, θ1 is the angle of the neutron emission region associated with time space, and d is the maximum outer diameter of the sample to be measured.

[0019] The fast neutron multiplicity measuring device with active and passive measuring functions of the present application can simultaneously realize the functions of active and passive fast neutron multiplicity measurement without changing the existing components of the device, avoiding additional structural adjustments, simplifying the operation of the equipment, improving the flexibility and efficiency of the measurement, and reducing the complexity and cost of the device. BRIEF DESCRIPTION OF DRAWINGS

[0020] Fig. 1 is a schematic diagram of the overall fast neutron multiplicity measuring device of the present application;

[0021] Fig. 2 is a schematic diagram of the layout of the components of the fast neutron multiplicity measuring device of the present application. DETAILED DESCRIPTION

[0022] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application but not all of them. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort should fall within the scope of the present application.

[0023] It is to be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0024] The relative arrangement of parts and steps, numerical expressions, and numerical values set forth in the examples are not intended to limit the scope of the present application, unless otherwise specifically stated. It is to be understood that the drawings are not necessarily to scale as the dimensions of the parts shown are for the purpose of providing an appropriate understanding. Technical, methods, and apparatuses known to those of ordinary skill in the relevant art can not be discussed in detail herein, but should be considered as if the discussion were incorporated herein and be considered a part of the detailed description. In all examples shown and discussed herein, any specific values are to be interpreted as illustrative only and not limiting. Thus, other examples of example embodiments can have different values. It is to be noted that like reference numerals and letters refer to like items in the drawings, and once an item is defined in one drawing, it need not be discussed further in subsequent drawings.

[0025] In the description of the present application, it needs to be understood that the orientation words such as "front, back, up, down, left, right", "transverse, vertical, perpendicular, horizontal" and "top, bottom" and the like indicated orientation or position relationship are generally based on the orientation or position relationship shown in the drawings, only for the convenience of describing the present application and simplifying the description, without the opposite indication, these orientation words do not indicate and imply that the indicated device or element must have a particular orientation or be constructed and operated in a particular orientation, therefore, it cannot be understood as a limitation on the scope of protection of the present application; the orientation words "inner, outer" refer to the inner and outer relative to the contour of each component.

[0026] For the purposes of this description, spatially relative terms, such as "above", "below", "up", "down", "between", "within", "left", "right", "front", "back", "upper", "lower", "horizontal", "vertical", "above", "below", "up", "down", "top", "bottom", "side", "end", etc., are intended to describe the orientation of one device or feature relative to another device or feature as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. The devices can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. For example, if a device is described as "above" or "upward" from another device or structure, it can be oriented "below" or "downward" from the other device or structure when placed in another orientation. Similarly, if a device is described as "below" or "downward" from another device or structure, it can be oriented "above" or "upward" from the other device or structure when placed in another orientation. Thus, the exemplary spatially relative descriptors used herein are intended to encompass all such orientations.

[0027] In addition, it should be noted that the use of "first", "second", and the like words of similar meaning in connection with a particular feature is used for convenience only and is not intended to limit the scope of the present application to the features described with such terminology. Unless otherwise stated, these words are not intended to convey any special meaning or significance.

[0028] In the present application, unless otherwise clearly specified and limited, if the terms "mounting", "connection", "connecting", "fixing" and the like are used, these terms should be interpreted in a broad sense. For example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0029] In order to realize the simultaneous possession of active method measurement function and passive method measurement function without increasing or reducing the components of the measuring device, the present application provides a fast neutron multiplicity measuring device with active and passive measurement functions, as shown in Figs. 1-2 .

[0030] The fast neutron multiplicity measuring device of the present application comprises a fast neutron detector 1, a sample container 2, a neutron generator 3, and a neutron source shielding cone 4.

[0031] The fast neutron detector 1 is in a ring array structure. The sample container 2 is arranged in the central measurement area.

[0032] The neutron generator 3 is arranged at the end of the ring array. The neutron generator 3 has an alpha timing function.

[0033] The neutron source shielding cone 4 is arranged between the neutron generator 3 and the fast neutron detector 1.

[0034] The neutron generator 3 with alpha timing function is integrated in the passive fast neutron multiplicity measurement device, realizing the active and passive dual-mode measurement capability, and the two measurement modes have no physical interference and no need for any mechanical structure layout adjustment.

[0035] In active measurement, the neutron generator emits neutrons according to the set parameters, and the alpha timing signal is used as the opening coincidence signal. Only the neutron signals measured by the fast neutron detector within the coincidence window are subjected to coincidence and fast neutron multiplicity measurement, greatly suppressing the measurement interference of the non-associated neutrons and environmental scattered and reflected neutrons of the neutron generator 3. In passive measurement, the neutron generator does not work, and only the neutron signals measured by the fast neutron detector are subjected to self-coincidence and fast neutron multiplicity measurement.

[0036] The arrangement of the neutron generator 3 with alpha timing function can be located at one end of the ring-shaped detector axis, or alpha timing neutron generators 3 can be arranged at both ends of the ring-shaped detector axis, realizing the spatial uniformity of the active neutron source irradiation of the measured sample and improving the measurement accuracy of the quality attributes of uranium materials.

[0037] The fast neutron multiplicity measurement device of this application simultaneously has active and passive measurement functions without increasing or reducing the components of the measurement device. It can measure samples containing plutonium materials, samples containing uranium materials, and samples containing uranium-plutonium material mixtures. The interference problem of the Am-Li neutron source to the detector in passive measurement is solved, the integration and user convenience of the fast neutron multiplicity measurement device are improved, and the measurement application scenarios of the fast neutron multiplicity measurement device are broadened.

[0038] The neutron generator 3 is used as the driving source, which can be a DD reaction neutron generator 3 or a DT reaction neutron generator 3, replacing the conventional Am-Li neutron source. In passive measurement, the neutron generator 3 does not work, i.e., does not produce neutrons. In active measurement, the neutron generator 3 works according to the set parameters to produce neutrons as the driving source.

[0039] Since the neutron source 5 produced by the neutron generator 3 is emitted in 4π direction, in order to reduce the interference problem of the invalid neutrons (neutrons emitted by the neutron generator that cannot directly irradiate the measured sample) of the neutron generator 3 to the fast neutron multiplicity detector, a neutron source shielding cone 4 is arranged between the target point 31 of the neutron generator 3 and the detector, shielding the neutrons directly emitted by the neutron generator 3 to the detector and reducing the background signal strength of the fast neutron multiplicity detector.

[0040] The neutron generator 3 adopts a neutron generator with alpha timing function. The alpha timing detector marks the space-time correlated neutrons and gives a high-precision timing signal. Only the time-space correlated neutrons are shot through the central through hole of the neutron source shielding cone 4 to the nuclear material detection area of the fast neutron multiplicity detector array as the active method neutron source 5.

[0041] Specifically, the structure and layout of the fast neutron multiplicity measurement device with active and passive measurement functions are as shown in Fig. 1 The fast neutron multiplicity measurement device is composed of a ring array of fast neutron detectors 1, a central measurement area sample container 2, a neutron generator 3 with alpha timing function, and a neutron source shielding cone 4 with a central through hole. It also includes the support structure of the fast neutron detector 1 and the support structure of the sample container 2. The fast neutron multiplicity measurement device adopts a ring-cylindrical arrangement of detector arrays, which can be single ring or multiple rings. The axial ends of the ring array are left empty, one end is arranged with the neutron generator 3, and the central through hole of the neutron source shielding cone 4 is arranged between the neutron generator 3 and the fast neutron detector 1 array to shield the neutrons directly emitted from the neutron generator 3 to the fast neutron detector 1.

[0042] The positional relationship of the fast neutron detector 1, the target point 31 and direction of the neutron generator 3, and the neutron source shielding body 4 is as shown in Fig. 2

[0043] The ring array of the fast neutron detector 1 can be single ring or multiple ring arrangement, each ring is composed of multiple detectors arranged uniformly. The number of rings and the number of detectors per ring are determined by the total neutron detection efficiency. The inner cavity diameter D of the ring-shaped fast neutron detector 1 is determined by the maximum outer diameter d of the sample to be measured. The axial ends of the ring array are left empty for arranging the neutron generator 3 with alpha timing function. The neutron generator 3 can be arranged only at one end or at both ends.

[0044] The target point 31 of the neutron generator 3 is arranged on the ring-shaped central axis, and the distance h from the center of the detector array is determined by the time-space correlated neutron emission area angle θ1 and the maximum outer diameter d of the sample to be measured. The formula is as follows:

[0045] h = d / arctg (θ1) / 2

[0046] The neutron source shielding body 4 is arranged between the neutron generator 3 and the detector array. The projection area angle θ2 of the neutron source shielding cone 4 along the axial direction effectively covers the detectors of the detector array, avoiding strong background interference of the non-associated neutrons of the neutron generator 3 on the detectors. The central cone-shaped through hole is used for the direct emission of the space-time correlated neutrons of the neutron generator 3 to the sample area to be measured. The included angle of the cone-shaped through hole is slightly larger than the correlated neutron emission area angle θ1.

[0047] ​The working procedure of the measuring device measured by different methods is as follows:

[0048] (1) Passive method fast neutron multiplicity measurement procedure: for example, when the measurement object is plutonium material, the neutron generator 3 does not work, at this time the fast neutron multiplicity measurement device with passive measurement function of the application can realize passive method fast neutron multiplicity measurement.

[0049] S1 The multi-channel fast signal acquisition and analysis equipment measures the pulse signals of all detectors of the fast neutron detector 1 array, and calculates and analyzes the characteristic information of the pulse signals and distinguishes neutron gamma signals.

[0050] S2 The multiplicity of all neutron signals is measured and analyzed to obtain the neutron multiplicity result.

[0051] S3 The mass properties of the measured object part material are obtained according to the set parameters and algorithms.

[0052] (2) Active method fast neutron multiplicity measurement procedure: for example, when the measurement object is uranium material, the neutron generator 3 works according to the set parameters, at this time the fast neutron multiplicity measurement device can realize active method fast neutron multiplicity measurement.

[0053] S1 The multi-channel fast signal acquisition and analysis equipment measures the pulse signals of all detectors of the fast neutron detector 1 array and the α detector pulse signals of the neutron generator 3, calculates and analyzes the characteristic information of the detector pulse signals and distinguishes neutron gamma signals, and calculates and analyzes the characteristic information of the α detector pulse signals to obtain effective α timing signals.

[0054] S2 The α timing signal is used as a gate signal to measure and analyze the multiplicity of the neutron signals in the coincidence window after the timing signal, and the neutron multiplicity result is obtained.

[0055] S3 The mass properties of the measured object uranium material are obtained according to the set parameters and algorithms.

[0056] (3) Active and passive method fast neutron multiplicity measurement procedure: for example, when the measurement object is a mixed uranium-plutonium material, the active method and the passive method can be used for composite fast neutron multiplicity measurement in sequence.

[0057] S1 Passive method fast neutron multiplicity measurement procedure is performed for measurement.

[0058] S2 Active method fast neutron multiplicity measurement procedure is performed for measurement.

[0059] S3 The mass properties of the measured object plutonium and uranium are obtained according to the set parameters and algorithms based on the joint measurement results of the passive method and the active method.

Claims

1. A fast neutron multiplicity measuring device, characterized by: The application relates to a fast neutron detector, which comprises a fast neutron detector, a sample container, a neutron generator and a neutron source shielding cone. The fast neutron detector is in a ring array structure; the sample container is arranged in a central measurement area; The neutron generator is arranged at one end of the ring array; the neutron generator has an alpha timing function; the neutron source shielding cone is arranged between the neutron generator and the fast neutron detector.

2. The fast neutron multiplicity counting device of claim 1, wherein: The ring array structure of the fast neutron detector is single-ring arrangement or multi-ring arrangement, and each ring is composed of a plurality of detectors uniformly arranged.

3. The fast neutron multiplicity counting device of claim 2, wherein: The specific number of rings and the number of detectors in each ring of the ring array structure of the fast neutron detector are determined by the total neutron detection efficiency.

4. The fast neutron multiplicity counting device of claim 1, wherein: The inner cavity diameter of the ring array structure of the fast neutron detector is determined by the maximum outer diameter of the measured sample.

5. The fast neutron multiplicity counting device of claim 1, wherein: The neutron generator is a DD reaction neutron generator or a DT reaction neutron generator, and has an alpha timing function.

6. The fast neutron multiplicity counting device of claim 1, wherein: The neutron generator is arranged at one end of the ring array.

7. The fast neutron multiplicity counting device of claim 1, wherein: The target point of the neutron generator is arranged on the central axis of the ring array.

8. The fast neutron multiplicity counting device of claim 7, wherein: The distance between the target point and the center of the detector array is determined by the following equation: h=d / arctg(theta1) / 2; Wherein, h is the distance between the target point and the center of the detector array; theta1 is the angle of the time-space correlated neutron emission area; d is the maximum outer diameter of the measured sample.

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