A compact neutron conduit shielding device and method of installation thereof

Abstract

The application discloses a compact neutron conduit shielding device and a mounting method thereof. The compact neutron conduit shielding device comprises a neutron conduit supporting device, a neutron conduit, a conduit shielding body main body, and a conduit shielding body supporting device. The neutron conduit is arranged as an independent vacuum tube without a stainless steel vacuum cover. An outer layer of the vacuum tube is provided with a layer of glass. Two ends of each independent neutron conduit are sealed by aluminum windows. The conduit shielding body main body comprises, from inside to outside, a neutron absorbing layer, a gamma radiation protection layer, and a stray neutron absorbing layer. The conduit shielding body supporting device is used for supporting the conduit shielding body main body and comprises a conduit shielding body support body and two C-shaped cross beams. The C-shaped cross beams are arranged on the top of the conduit shielding body support body. The neutron conduit shielding body is non-magnetic, easy to install and maintain, and can be used for the collimation, installation and maintenance of the neutron conduit. The application is suitable for shielding the neutron conduit in a conduit hall. The mounting method effectively avoids the influence of the deformation of the neutron shielding body caused by its own weight on the collimation performance of the neutron conduit.

Description

Technical Field

[0001] This invention relates to a compact neutron conduit shielding device and its installation method. Background Technology

[0002] In recent years, with the development of large scientific facilities in China, the rapid development of neutron sources such as the China Advanced Research Reactor (CARR), the China Mianyang Research Reactor (CMRR), and the China Spallation Neutron Source (CSNS) has led to an increasing number of neutron scattering spectrometers being built, which in turn increases the demand for biological shielding walls.

[0003] Neutron scattering spectrometers typically use neutron conduits to guide the neutron beam into the conduit hall, with spectrometers set up at the openings of each conduit. Neutron transmission through the neutron conduit is achieved through multiple reflections of the neutron beam by a highly reflective coating on its inner surface. Neutrons that are not reflected during transmission are either scattered or interact with elements such as B, Si, Na, and K within the neutron conduit, producing gamma radiation, which is the primary source of radiation from the neutron conduit. Simultaneously, a large number of stray neutrons and gamma rays are generated during neutron scattering experiments. Effective shielding measures not only ensure the safety of experimental personnel but also reduce the impact on adjacent instruments. Furthermore, to accommodate as many instruments as possible within the conduit hall, compact and effective shielding is essential.

[0004] Furthermore, with the development of modern science, neutron scattering experiments are increasingly used in extreme sample environments (especially strong magnetic field sample environments) and polarized neutron experiments. When using a strong magnetic field sample environment, stray magnetic fields are generated around the magnet, requiring that there be no magnetic materials around the sample environment; when conducting polarized neutron scattering experiments, a guiding magnetic field is needed to polarize the neutrons, requiring that the surrounding environment be non-magnetic.

[0005] Heavy concrete, capable of shielding both neutrons and gamma rays, is widely used in neutron shielding materials. Existing neutron biological shielding walls typically employ a method of first welding thick steel plates into a mold, then pouring heavy concrete into the welded module. This heavy concrete often contains a large amount of magnetic elements and is bulky, occupying considerable space for the spectrometer and compressing its takeoff angle range. Generally, neutron conduits and neutron scattering spectrometers have service lives of several decades, while neutron conduits require extremely high precision, typically exceeding ±0.02 mm. The heavy shielding structure can easily cause deformation of the support structure and ground subsidence, leading to reduced collimation of the neutron conduit and consequently affecting transmission efficiency.

[0006] Therefore, it is necessary to separate the support structure of the neutron conduit and the neutron conduit shield to prevent them from interfering with each other, ensure high alignment of the neutron conduit during service, and minimize the weight and volume of the shield while ensuring the shielding effect, so as to design a neutron conduit shield structure that is easy to install and maintain. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a compact neutron conduit shielding device and its installation method.

[0008] This invention designs a non-magnetic, easy-to-install, and easy-to-maintain neutron conduit shield, taking into account the alignment, installation, and maintenance of the neutron conduit, and is suitable for shielding neutron conduits in conduit halls. The shield adopts a modular form, which can be combined and matched according to the neutron conduit situation for better cyclic reuse. The neutron conduit shield is sealed with boron-containing polyethylene plate, so that the neutron conduit shield can also serve as a biological shielding wall, which can effectively reduce the background of the experiment, reduce the influence between adjacent instruments, and protect the staff outside the experimental area. The conduit shield and the conduit support are grouted separately, and the load-bearing of the two is cut and separated, which effectively avoids the impact of ground deformation caused by the weight of the shield on the alignment of the neutron conduit. At the same time, this invention proposes a new installation method, namely, the independent installation of the load-bearing base of the neutron conduit and the neutron conduit shield, thereby effectively avoiding the impact of deformation caused by the weight of the neutron shield on the alignment performance of the neutron conduit.

[0009] This invention provides a compact neutron conduit shielding device, comprising:

[0010] A neutron conduit support device is used to install neutron conduits and ensure installation accuracy without damage. The neutron conduits are set as independent vacuum tubes without stainless steel vacuum shrouds. The outer layer of the vacuum tube is covered with a layer of glass, and both ends of each independent neutron conduit are sealed with aluminum windows.

[0011] The main body of the duct shield consists of, from the inside out, a neutron absorbing layer, a gamma radiation shielding layer, and a stray neutron absorbing layer;

[0012] A catheter shielding support device is used to support the main body of the catheter shielding body. It includes a catheter shielding support body and two C-shaped crossbeams. The C-shaped crossbeams are C-shaped. The C-shaped crossbeams are located on the top of the catheter shielding support body.

[0013] In the aforementioned compact neutron conduit shielding device, the neutron conduit support device includes a neutron conduit support body, an I-shaped beam, and a neutron conduit clamp. The I-shaped beam has an I-shaped structure. The neutron conduit clamp is used to fix the neutron conduit and is installed on the I-shaped beam. The neutron conduit support body supports the I-shaped beam.

[0014] In the aforementioned compact neutron conduit shielding device, the conduit shielding body is supported by two C-shaped crossbeams located on both sides of the neutron conduit.

[0015] The two C-shaped crossbeams and the conduit shield support structure are arranged in a U-shape, such that the I-shaped crossbeam used to support the neutron conduit passes through the middle of the two C-shaped crossbeams.

[0016] In the aforementioned compact neutron conduit shielding device, after the compact neutron conduit shielding device is installed, the top surface of the C-shaped crossbeam is higher than the I-shaped crossbeam; thus, a certain space is left between the neutron conduit and the gamma radiation protection layer to facilitate the alignment of the neutron conduit.

[0017] In the aforementioned compact neutron conduit shielding device, both the I-shaped crossbeam and the C-shaped crossbeam are made of 304 stainless steel.

[0018] In the aforementioned compact neutron conduit shielding device, the neutron absorbing layer is made of boron-containing rubber; the boron-containing rubber includes rubber with a boron mass percentage of 3% to 5%.

[0019] In the aforementioned compact neutron conduit shielding device, the gamma radiation protection layer is made of a lead-antimony alloy block; the lead-antimony alloy block comprises a lead-antimony alloy with an antimony mass percentage of 3% to 5%.

[0020] In the aforementioned compact neutron conduit shielding device, the stray neutron absorbing layer is made of boron-containing polyethylene board. The boron-containing polyethylene board is a black board with a high boron content, and the boron content is 5% to 20% by mass. It can effectively absorb scattered neutrons and reduce the generation of high-energy gamma rays.

[0021] The present invention also provides an installation method for the above-mentioned compact neutron conduit shielding device, comprising the following steps:

[0022] 1) The center line along the beam direction is engraved on the duct shield support. The bottom of the duct shield support is positioned 25-35mm (specifically 30mm) from the ground to ensure installation accuracy. During installation, first locate the installation point and drill holes in the ground. Use chemical rivets to initially fix the load-bearing duct shield support. Then, insert three aluminum plates in a triangular arrangement between the bottom of the duct shield support and the ground. Each aluminum plate has a screw connected to the bottom of the duct shield support. The horizontal height of the duct shield support is adjusted using these three screws. Using the horizontal height of the neutron beam's central axis as a reference, the laser level ultimately measures the horizontal height of the support with an error of less than ±0.5mm. After adjusting the horizontal height, fine adjustments are made in the horizontal plane using a theodolite and the markings on the support to align the markings on the duct shield support to the vertical central axis of the beam, achieving a final accuracy of ±0.5mm. After alignment, all bolts are tightened, and high-strength, non-shrink grout is used to fill the space between the duct shield support and the ground.

[0023] The neutron conduit support is installed according to the above method; the grouting material below the conduit shield support is completely separate from the grouting material below the neutron conduit support.

[0024] The C-shaped crossbeams are disposed on both sides of the catheter shield support, and the two C-shaped crossbeams and the catheter shield support structure are arranged in a U-shape; the main body of the catheter shield is supported by the two C-shaped crossbeams.

[0025] 2) During installation, after the neutron conduit support is aligned, the I-shaped beam is first installed on the neutron conduit support. The I-shaped beam passes between the two C-shaped beams, and the top surface of the C-shaped beam is higher than the I-shaped beam, so that there is space between the neutron conduit and the gamma radiation shielding layer. The I-shaped beam is aligned with the vertical central axis of the beam as a reference, with an accuracy within ±0.5mm, and the installation of the I-shaped beam and the C-shaped beam is completed.

[0026] 3) The gamma radiation shielding layer is processed into two layers of lead-antimony alloy blocks. The edges of the lead-antimony alloy blocks are processed into 90° steps offset by 20-30mm (specifically 25mm), so that adjacent lead-antimony alloy blocks are joined in a stepped manner. The bottom lead-antimony alloy block is installed first, and then the neutron conduit is installed. The neutron conduit is fixed by a neutron conduit clamp and installed on the I-shaped crossbeam. The neutron conduit is collimated using a total station and a laser tracker. The installation accuracy of the neutron conduit relative to the beam center axis can reach ±0.01mm. After the neutron conduit is collimated, the gamma radiation shielding layers on the left and right sides and the top are installed. The neutron absorption layer is directly attached to the neutron conduit, and the stray neutron absorption layer is installed around the neutron conduit, thus completing the installation of the compact neutron conduit shielding device.

[0027] The beneficial effects of this invention are:

[0028] 1. The neutron conduit shield of the present invention adopts a layered structure with an inner layer wrapped with boron-containing rubber, an outer layer spliced ​​with lead-antimony alloy blocks, and an outer perimeter sealed with boron-containing polyethylene sheet. This layered structure can not only effectively shield the neutron and gamma radiation generated during the internal reflection process of the neutron conduit, but also serve as a biological shielding wall to reduce the radiation level outside the experimental area and reduce mutual interference between adjacent instruments.

[0029] 2. The main component of the neutron conduit shielding body in this invention, the lead-antimony alloy layer, exists in the form of unit blocks. Adjacent unit blocks are joined by a stepped joint, with small joint gaps, which can effectively prevent radiation leakage. The mass of each unit block is limited, making it easy to install and disassemble. It can also be combined and installed according to the length of the conduit, which facilitates the maintenance and repair of the conduit. After the spectrometer is decommissioned, it can also be combined and reused according to the needs of building a new spectrometer.

[0030] 3. The neutron conduit shield and all supports in this invention are made of non-magnetic materials, making them suitable for neutron spectrometers with strong magnetic field sample environments and polarized neutron experiments.

[0031] 4. The neutron guide shield in this invention has high efficiency and small size, and is especially suitable for spectrometers that use monochromators, such as triaxial spectrometers. The instrument has a large range of takeoff angles and a wide range of initial energies.

[0032] 5. In this invention, the neutron conduit and its shielding body adopt independent load-bearing bases. Even if the self-weight of the shielding body causes ground deformation, it will not directly affect the support of the neutron conduit or the straightness of the neutron conduit. In other words, it can effectively avoid the influence of the strain of the base caused by the weight of the neutron conduit shielding body on the straightness of the neutron conduit.

[0033] 6. The neutron conduit shield in this invention has a compact structure, which occupies less space than the traditional concrete shield, leaving more space for the neutron spectrometer. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the compact neutron conduit shielding device of the present invention.

[0035] Figure 2 yes Figure 1 AA sectional view.

[0036] Figure 3 This is an installation view of the sub-conduit in this invention.

[0037] The markings in the diagram are as follows:

[0038] 1. Lead-antimony alloy block; 2. Neutron conduit; 3. C-shaped crossbeam; 4. I-shaped crossbeam; 5. Conduit shield support; 6. Neutron conduit support; 7. Boron-containing polyethylene plate mounting rail; 8. Calibration line; 9. Neutron conduit clamp. Detailed Implementation

[0039] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0040] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0041] To facilitate understanding of this technical solution by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings in the embodiments. The embodiments described are not intended to limit the present invention. All other embodiments obtained by those skilled in the art based on the present invention without inventive effort are within the scope of protection of the present invention.

[0042] like Figure 1-2 As shown, a compact neutron conduit shielding device provided by the present invention includes:

[0043] The neutron conduit support device is used to install the neutron conduit 2 and ensure installation accuracy without damage. The neutron conduit is set as an independent vacuum tube without a stainless steel vacuum cover. The outer layer of the vacuum tube is covered with a layer of glass. Both ends of each independent neutron conduit are sealed with aluminum windows. The neutron conduit support device includes a neutron conduit support body 6, an I-shaped crossbeam 4 and a neutron conduit clamp 9. The I-shaped crossbeam 4 has an I-shaped structure. The neutron conduit clamp 9 is used to fix the neutron conduit 2 and is installed on the I-shaped crossbeam 4. The neutron conduit support body 6 supports the I-shaped crossbeam 4.

[0044] The main body of the conduit shield consists of, from the inside out, a neutron absorption layer (made of boron-containing rubber and directly wrapped around the outside of the neutron conduit), a gamma radiation protection layer (made of lead-antimony alloy block 1), and a stray neutron absorption layer (not shown in the figure, made of boron-containing polyethylene plate, and its mounting rail 7 is shown in the figure).

[0045] The catheter shielding support device, used to support the main body of the catheter shield, includes a catheter shielding support 5 and two C-shaped crossbeams 3. The C-shaped crossbeams 3 are C-shaped in structure and are located on top of the catheter shielding support 5. The main body of the catheter shield is supported by the two C-shaped crossbeams 3 located on both sides of the neutron catheter 2. The two C-shaped crossbeams 3 and the catheter shielding support 5 are arranged in a U-shape, so that the I-shaped crossbeam 4 used to support the neutron catheter 2 passes through the middle of the two C-shaped crossbeams 3.

[0046] Furthermore, after the compact neutron conduit shielding device is installed, the top surface of the C-shaped crossbeam 3 is higher than that of the I-shaped crossbeam 4, so that there is a certain space between the neutron conduit 2 and the gamma radiation protection layer (i.e., lead-antimony alloy block 1) to facilitate the alignment of the neutron conduit.

[0047] Furthermore, both the I-shaped crossbeam 4 and the C-shaped crossbeam 3 are made of 304 stainless steel.

[0048] Furthermore, boron-containing rubber includes rubber with a boron mass percentage of 3% to 5%.

[0049] Furthermore, the lead-antimony alloy block 1 comprises a lead-antimony alloy with an antimony mass percentage of 3% to 5%.

[0050] Furthermore, the boron-containing polyethylene board is a black board with a high boron content, ranging from 5% to 20% by mass. It can effectively absorb scattered neutrons and reduce the generation of high-energy gamma rays.

[0051] The installation method of the compact neutron conduit shielding device of the present invention includes the following steps:

[0052] 1) The center line along the beam direction is marked on the duct shield support 5. The bottom of the duct shield support 5 is set about 30mm from the ground to ensure its installation accuracy. During the installation process, the installation point is first located and holes are drilled in the ground. The duct shield support 5 for load-bearing is initially fixed with chemical rivets. Then, three aluminum plates are inserted between the bottom of the duct shield support 5 and the ground in a triangular arrangement. Each aluminum plate is pressed with a screw connected to the bottom of the duct shield support 5. The horizontal height of the duct shield support 5 is adjusted using these three screws. With the horizontal height of the neutron beam center axis as the reference, the laser level instrument finally measures the horizontal height of the support with an error of less than ±0.5mm. After the horizontal height adjustment is completed, the theodolite and the markings on the support are used for fine-tuning in the horizontal plane to align the markings of the duct shield support 5 with the vertical center axis of the beam. The final accuracy can reach ±0.5mm. After alignment is completed, all bolts are tightened and high-strength non-shrink grout is used to fill the space between the duct shield support 5 and the ground.

[0053] Install the neutron conduit support 6 according to the above method; the grouting material below the conduit shield support 5 is completely separate from the grouting material below the neutron conduit support 6.

[0054] C-shaped crossbeams 3 are arranged on both sides of the catheter shield support 5, and the two C-shaped crossbeams 3 and the catheter shield support 5 are arranged in a U-shape; the main body of the catheter shield is supported by the two C-shaped crossbeams.

[0055] 2) During the installation process, after the neutron conduit support is aligned, the I-shaped beam 4 is first installed on the neutron conduit support 6. The I-shaped beam 4 passes between the two C-shaped beams 3, and the top surface of the C-shaped beam 3 is higher than the I-shaped beam 4, so that there is space between the neutron conduit 2 and the gamma radiation shielding layer (lead-antimony alloy block 1). The I-shaped beam 4 is aligned with the vertical central axis of the beam as the reference, with an accuracy within ±0.5mm, and the installation of the I-shaped beam 4 and the C-shaped beam 3 is completed.

[0056] 3) The gamma radiation shielding layer is processed into two lead-antimony alloy blocks 1. The edges of the lead-antimony alloy blocks 1 are processed into a 90° step shape offset by 25mm, so that the two adjacent lead-antimony alloy blocks 1 are joined in a step shape. First, the bottom lead-antimony alloy block 1 is installed, and then the neutron conduit 2 is installed. The neutron conduit clamp 9 fixes the neutron conduit and is installed on the I-shaped crossbeam 4. The neutron conduit 2 is collimated using a total station and a laser tracker. The installation accuracy of the neutron conduit 2 relative to the beam center axis can reach ±0.01mm. After the neutron conduit 2 is collimated, the gamma radiation shielding layers on the left and right sides and the top are installed. The neutron absorption layer is directly attached to the neutron conduit 2. A stray neutron absorption layer is installed on the periphery of the neutron conduit 2, thus completing the installation of the compact neutron conduit shielding device.

[0057] In the description of this invention, it should be understood that the terms "upper", "lower", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

Claims

1. A compact neutron conduit shielding device, characterized in that, It includes: A neutron conduit support device is used to install neutron conduits, wherein the neutron conduits are configured as independent vacuum tubes without stainless steel vacuum shrouds, the outer layer of the vacuum tubes is covered with a layer of glass, and both ends of each independent neutron conduit are sealed with aluminum windows. The main body of the duct shield consists of, from the inside out, a neutron absorbing layer, a gamma radiation shielding layer, and a stray neutron absorbing layer; A catheter shielding support device is used to support the main body of the catheter shielding body, including a catheter shielding support body and two C-shaped crossbeams, wherein the C-shaped crossbeams are C-shaped in structure; the C-shaped crossbeams are disposed on the top of the catheter shielding support body. The neutron conduit support device includes a neutron conduit support body, an I-shaped crossbeam, and a neutron conduit clamp. The I-shaped crossbeam has an I-shaped structure. The neutron conduit clamp is used to fix the neutron conduit and is installed on the I-shaped crossbeam. The neutron conduit support body supports the I-shaped crossbeam. The main body of the conduit shield is supported by two C-shaped crossbeams located on both sides of the neutron conduit. The two C-shaped crossbeams and the conduit shield support are arranged in a U-shape, such that the I-shaped crossbeam used to support the neutron conduit passes through the middle of the two C-shaped crossbeams; The gamma radiation shielding layer is processed into two lead-antimony alloy blocks, the edges of which are processed into 90° steps offset by 20~30mm, so that adjacent lead-antimony alloy blocks are joined in a stepped manner.

2. The compact neutron conduit shielding device according to claim 1, characterized in that, After the compact neutron conduit shielding device is installed, the top surface of the C-shaped crossbeam is higher than that of the I-shaped crossbeam.

3. The compact neutron conduit shielding device according to claim 1 or 2, characterized in that, Both the I-shaped beam and the C-shaped beam are made of 304 stainless steel.

4. The compact neutron conduit shielding device according to claim 1, characterized in that, The neutron absorbing layer is made of boron-containing rubber; the boron-containing rubber has a boron content of 3% to 5% by mass.

5. The compact neutron conduit shielding device according to claim 1, characterized in that, The gamma radiation shielding layer is made of a lead-antimony alloy block; the lead-antimony alloy block comprises a lead-antimony alloy with an antimony mass percentage of 3% to 5%.

6. The compact neutron conduit shielding device according to claim 1, characterized in that, The stray neutron absorbing layer is made of boron-containing polyethylene board, which is a black board with high boron content and a boron mass percentage of 5% to 20%.

7. A method for installing the compact neutron conduit shielding device according to any one of claims 1-6, comprising the following steps: 1) The center line along the beam direction on the duct shield support is used to ensure installation accuracy by setting the bottom of the duct shield support 25-35mm above the ground. During installation, the installation point is first located and holes are drilled in the ground. The duct shield support for load-bearing is initially fixed with chemical rivets. Then, three aluminum plates are inserted between the bottom of the duct shield support and the ground in a triangular arrangement. Each aluminum plate is secured with a screw connected to the bottom of the duct shield support. These three screws are used to adjust the horizontal height of the duct shield support. Using the horizontal height of the neutron beam center axis as a reference, the laser level instrument ultimately measures the horizontal height of the support with an error of less than ±0.5 mm. After the horizontal height adjustment is completed, fine adjustments are made in the horizontal plane using a theodolite and the lines on the support to align the duct shield support lines with the vertical center axis of the beam, achieving a final accuracy of ±0.5 mm. After alignment, all bolts are tightened, and high-strength non-shrink grout is used to fill the space between the duct shield support and the ground. The neutron conduit support is installed according to the above method; the grouting material below the conduit shield support is completely separate from the grouting material below the neutron conduit support. The C-shaped crossbeams are disposed on both sides of the catheter shield support, and the two C-shaped crossbeams and the catheter shield support structure are arranged in a U-shape; the main body of the catheter shield is supported by the two C-shaped crossbeams. 2) During installation, after the neutron conduit support is aligned, the I-shaped beam is first installed on the neutron conduit support. The I-shaped beam passes between the two C-shaped beams, and the top surface of the C-shaped beam is higher than the I-shaped beam, so that there is space between the neutron conduit and the gamma radiation shielding layer. The I-shaped beam is aligned with the vertical central axis of the beam as a reference, with an accuracy within ±0.5 mm, and the installation of the I-shaped beam and the C-shaped beam is completed. 3) The gamma radiation shielding layer is processed into two lead-antimony alloy blocks. The edges of the lead-antimony alloy blocks are processed into 90° steps offset by 20~30mm, so that adjacent lead-antimony alloy blocks are joined in a stepped manner. The bottom lead-antimony alloy block is installed first, and then the neutron conduit is installed. The neutron conduit is fixed by a neutron conduit clamp and installed on the I-shaped crossbeam. The neutron conduit is collimated using a total station and a laser tracker. The installation accuracy of the neutron conduit relative to the beam center axis can reach ±0.01 mm. After the neutron conduit is collimated, the gamma radiation shielding layers on the left and right sides and the top are installed. The neutron absorption layer is directly attached to the neutron conduit. The stray neutron absorption layer is installed around the neutron conduit, thus completing the installation of the compact neutron conduit shielding device.

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