Neutron irradiation device for 40Ar-39Ar dating sample

Abstract

The invention discloses a neutron irradiation device for 40Ar-39Ar dating samples, and relates to the technical field of research reactor irradiation, the neutron irradiation device comprises an aluminum pot, the aluminum pot is a full solid aluminum pot body, one end face of the aluminum pot is provided with a plurality of blind holes along the axial direction, and the blind holes are parallel to the axis of the aluminum pot and are used for placing quartz tubes; the aluminum cover is used for sealing one end of the aluminum pot; the size of the quartz tube is matched with that of the blind hole; a plurality of positioning heat conduction pieces are arranged in the quartz tube along the length direction of the quartz tube and are used for positioning and mounting samples; the positioning heat conduction pieces are aluminum columns, the multiple aluminum columns are all placed in the quartz tube, and samples are clamped between the adjacent aluminum columns. The 40Ar-39Ar dating sample neutron irradiation device can be used for performing neutron irradiation on the 40Ar-39Ar dating sample in a research reactor, not only can meet the irradiation temperature range required by irradiation of the 40Ar-39Ar dating sample, but also can ensure the stability and accuracy of the dating sample in the axial and radial positions.

Description

Technical Field

[0001] The present invention relates to the field of research reactor irradiation technology, and in particular to a method for 40 Ar- 39 Neutron irradiation device for Ar dating samples. Background Art

[0002] As an important technical means to study the earth's historical evolution, geological structure and other geological activities, high-precision potassium-containing minerals 40 Ar- 39 Argon dating is one of the most important research issues in isotope geochronology. This dating method involves placing potassium-containing samples in a nuclear reactor and irradiating them with fast neutrons. 39 K undergoes a nuclear reaction to transform into 39 Ar in the irradiated sample was measured by mass spectrometry. 40 Ar / 39 The Ar ratio can be used to calculate the geological age of the sample. 40 Ar- 39 Compared with other dating methods, Ar dating technology has the advantages of only needing to determine isotope ratios without requiring isotope content, being able to complete the measurement on a single machine, and obtaining sufficient information. It has been widely and deeply used in the fields of isotope geochronology, geochemistry, mineralogy, magma dynamics, and oil and gas exploration.

[0003] exist 40 Ar- 39 During the in-pile irradiation of Ar dating samples, neutrons and gamma photons in the nuclear reactor interact with the dating samples and the irradiator, depositing energy in them and causing them to heat up. In order to prevent the samples and irradiators from melting or breaking due to excessive temperatures, which may lead to failure of the irradiation test and adverse effects on the safety of reactor operation, the irradiation temperature needs to be controlled.

[0004] The neutron flux in the reactor irradiation channel is different in both the axial and radial directions. This difference causes certain differences in the neutron flux received by samples placed at different positions. In the axial direction, the neutron flux in the irradiation channel is distributed in a cosine curve. The area with the highest axial neutron flux is generally the middle area of ​​the active section, and decreases towards the two ends of the active section. In the radial direction, the neutron flux in the reactor is distributed in a zero-order Bessel function. This non-uniformity will inevitably have an adverse effect on the uniformity of the neutron flux received by samples at different axial positions and different positions in the same radial plane in the sample irradiation device. Usually, standard materials of known age are placed at different axial positions and different radial positions to monitor the neutron flux, obtain the neutron flux change curve, and then calculate the neutron flux actually received by the sample to be tested. Therefore, the accuracy of the measurement of the axial and radial positions of the sample and the standard material will affect the calculation error of the neutron flux received by the sample, so it is necessary to study the irradiation device that can obtain the precise axial and radial positions of the sample and the standard material. Summary of the invention

[0005] The present invention aims to solve the deficiencies of the prior art and to provide a 40 Ar- 39 Argon dating sample neutron irradiation device can be used in research reactors 40 Ar- 39 Neutron irradiation of Ar dating samples, the present invention can not only meet 40 Ar- 39 The irradiation temperature range required for Ar dating samples can also ensure the stability and accuracy of the dating samples in the axial and radial positions.

[0006] The present invention is achieved through the following technical solutions:

[0007] A kind of 40 Ar- 39 Neutron irradiation device for Ar dating samples, including:

[0008] An aluminum can, wherein the aluminum can is a fully solid aluminum can body, and a plurality of blind holes are opened along the axial direction on one end surface of the aluminum can, wherein the blind holes are parallel to the axis of the aluminum can and are used to place quartz tubes;

[0009] An aluminum cover, which is used to close one end of the aluminum can;

[0010] A quartz tube, wherein the sizes of the quartz tube and the blind hole are matched; a plurality of positioning heat-conducting parts are placed in the quartz tube along its length direction, and the positioning heat-conducting parts are used to position and install the sample.

[0011] Compared with the prior art, 40 Ar- 39During the in-pile irradiation of Ar dating samples, neutrons and gamma photons in the nuclear reactor interact with the dating samples and the irradiation device, depositing energy therein and causing them to heat up. In order to avoid the samples and irradiation devices from melting or breaking due to excessive temperatures, thereby causing more serious situations such as failure of the irradiation test and adverse effects on the safety of reactor operation, it is necessary to control the irradiation temperature; and the neutron flux in the reactor irradiation channel is different in both the axial and radial directions. This difference causes certain differences in the neutron flux received by samples placed at different positions. In the axial direction, the neutron flux in the irradiation channel is distributed in a cosine curve. The area with the highest axial neutron flux is generally the middle area of ​​the active section, and decreases towards the two ends of the active section. In the radial direction, the neutron flux in the reactor is distributed in a zero-order Bessel function. This non-uniformity will inevitably have an adverse effect on the uniformity of the neutron flux received by samples at different axial positions at the same radial position and at different positions in the same radial plane in the sample irradiation device. The present invention provides a method for 40 Ar- 39 Argon dating sample neutron irradiation device can be used in research reactors 40 Ar- 39 Neutron irradiation of Ar dating samples, the present invention can not only meet 40 Ar- 39 The irradiation temperature range required for Ar dating samples can also ensure the stability and accuracy of the dating samples in the axial and radial positions.

[0012] In the specific scheme, a cylindrical aluminum can and an aluminum cover are included, which can be assembled together to form the main body of the irradiation device, which is used to contain the quartz tube and the sample / standard substance inside it, and to separate the sample / standard substance from the water environment in the irradiation channel. The aluminum can is a solid cylindrical aluminum block, and a plurality of blind holes are dug out on its end surface. A plurality of quartz tubes can be arranged through the blind holes, wherein the number of blind holes is equal to the number of quartz tubes, and the radius of the blind holes matches the radius of the quartz tubes, and the number and arrangement position of the quartz tubes can be determined according to the irradiation needs. Since both the aluminum can and the aluminum cover are made of aluminum, this is because the neutron scattering cross-section and neutron absorption cross-section of aluminum are very small, and the interference and impact on the neutron field in the reactor are very small. At the same time, the thermal conductivity of aluminum is large, which can effectively reduce the irradiation temperature and realize the control of the irradiation temperature. A number of positioning heat-conducting parts are arranged inside the quartz tube along its length direction. Through the heat conduction and positioning functions of the positioning heat-conducting parts, the sample can be positioned and installed in the axial direction of the quartz tube. In this way, by accurately determining the axial position of the sample and the standard material, it is conducive to more accurate research on the neutron flux distribution characteristics, and it also plays a heat conduction role.

[0013] The above scheme aims to achieve: the cylindrical aluminum can and the aluminum can cover can be assembled together to form the main body of the irradiation device, which is used to accommodate the quartz tube and the sample / standard material inside, and separate the sample / standard material from the water environment in the irradiation channel. The use of aluminum metal parts such as the fully solid aluminum can and aluminum cover can improve the thermal conductivity of the device, reduce the irradiation temperature, and reduce the disturbance of the neutron field in the reactor caused by the irradiation device. In addition, the radial position of the sample and the standard material can be accurately determined through the several blind holes inside the aluminum can, and the axial position of the sample and the standard material can be accurately determined through the several positioning heat-conducting parts arranged inside the quartz tube along its length. Therefore, by accurately positioning the axial position and radial position of the sample and the standard material, the standard material of known age can be placed at different axial positions and different radial positions to monitor the neutron flux, obtain the neutron flux change curve, and then accurately calculate the neutron flux actually received by the sample to be tested.

[0014] As a method to facilitate rapid positioning of samples and improve the accuracy of irradiation temperature control, the positioning heat-conducting member is an aluminum column, the diameter of the aluminum column is compatible with the inner diameter of the quartz tube, and a number of the aluminum columns are placed in the quartz tube and arranged in sequence along the axial direction of the quartz tube; the adjacent aluminum columns are used to clamp the sample. Among them, when installing, the sample and the aluminum column can be directly placed in sequence, and the heat conduction and irradiation temperature control can be further achieved through the aluminum column, and the height of the aluminum column, the height of the sample / standard material, the number of stacking, the arrangement order, etc. can be determined according to the irradiation needs.

[0015] In order to realize the detection of multiple data and improve its functional diversity, at least one layer of samples is set between adjacent aluminum columns; for example, K2SO4 and CaF2 can be placed between adjacent aluminum columns, and K2SO4 and CaF2 are used to measure and obtain 40 K(n,p) 40 Ar, 40 Ca(n,nα) 36 Correction factor for side reactions of Ar.

[0016] In order to achieve stable installation of the quartz tube and reduce the shaking of the quartz tube in the axial direction, the quartz tube is placed in the blind hole with its opening facing downward, and the gap between the end of the quartz tube and the end of the blind hole is filled with quartz wool. The aluminum can is used to control the position of the quartz tube in the axial and radial directions to ensure that the quartz tube is located in the same radial plane and does not tilt.

[0017] In order to ensure the stability of the internal sample and aluminum column and improve the thermal conductivity, the end of the quartz tube away from the tube mouth is filled with quartz wool; the sample is wrapped and compacted with high-purity aluminum foil. In this solution, in addition to the containment function, the aluminum foil can also play a good thermal conductivity role; quartz wool can reduce the axial shaking of the sample / standard substance. The sample / standard substance is wrapped and compacted with high-purity aluminum foil, stacked together with the aluminum column in the quartz tube, and the upper gap in the quartz tube is filled with quartz wool. Finally, the quartz tube is sealed under vacuum conditions.

[0018] Because in 40 Ar- 39 During the in-pile irradiation of Ar dating samples, in addition to the target nuclear reaction 39 K(n,p) 39 In addition to Ar, there are also side reactions that can interfere with the dating results. 40 K(n,p) 40 Ar, 40 Ca(n,nα) 36 Ar, the side reaction 40 K(n,p) 40 Ar has a large absorption cross section for thermal neutrons with energy E < 0.01 MeV; and the target reaction 39 K(n,p) 39 Ar can occur when the neutron energy is >1MeV. Therefore, in order to ensure 39 In order to increase the yield of Ar and reduce the interference of side reactions, it is necessary to shield thermal neutrons with energy E<0.01MeV, and the setting is: the outer sides of the aluminum can and the aluminum cover are covered with a layer of cadmium. Cadmium has a large absorption cross section for thermal neutrons with energy less than 0.414eV, thereby shielding thermal neutrons and reducing side reactions. 40 K(n,p) 40 Interference from Ar.

[0019] Since the irradiation device and samples have high radioactivity after irradiation, it is necessary to cut and disassemble the irradiation device in the hot room and take out the quartz tube containing the sample / standard substance for subsequent 40 Ar / 39Ar ratio measurement. The cutting and disintegration in the hot chamber needs to be observed through a shielded window and operated by a manipulator, which increases the difficulty of operation and reduces the accuracy of operation compared with the operation outside the hot chamber. In order to facilitate cutting and disintegration after irradiation and reduce or even avoid the damage of the quartz tube caused by cutting and disintegration, it is necessary to carry out design research on the irradiation device. It is set as follows: a gap is left between the end face of the aluminum can at the opening of the blind hole and the bottom plane of the aluminum cover. And there is a certain distance between the end face of the aluminum can at the opening of the blind hole and the bottom plane of the aluminum cover. In this way, compared with the absence of a gap, the gap helps to find the lower knife position for cutting and disintegration after irradiation when cutting and disintegrating in the hot chamber, reduce the cutting area, shorten the cutting time, and reduce or even avoid the damage of the quartz tube caused by cutting and disintegration.

[0020] In order to improve the connection strength, the aluminum can and the aluminum cover are sealed and welded. During installation, the aluminum can and the aluminum can cover are welded and sealed and leak-detected to confirm that the welding is intact, and then placed in the irradiation channel for irradiation.

[0021] In order to facilitate the lifting operation when entering and exiting the pile, a lifting piece is welded on the top of the aluminum cover. The lifting piece can be a lifting ring or a long rod welded on the aluminum cover for lifting and grabbing.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] 1. The present invention provides a method for 40 Ar- 39 The neutron irradiation device for Ar dating samples adopts the design of covering the outer wall of the device with cadmium, which can effectively absorb thermal neutrons with energy E<0.414eV and reduce side reactions 40 K(n,p) 40 The occurrence of Ar and its interference on dating results.

[0024] 2. The present invention provides a method for 40 Ar- 39 The neutron irradiation device for Ar dating samples uses aluminum metal parts such as aluminum cans, aluminum can covers, aluminum foil, and aluminum columns. While improving the thermal conductivity of the device and reducing the irradiation temperature, it also reduces the disturbance caused by the irradiation device to the neutron field in the reactor.

[0025] 3. The present invention provides a method for 40 Ar- 39 The neutron irradiation device for Ar dating samples uses an aluminum can with a blind hole and fills the upper gap in the blind hole with quartz wool to reduce shaking and effectively control the radial and axial positions of the quartz tube arrangement.

[0026] 4. The present invention provides a method for 40 Ar- 39The neutron irradiation device for Ar dating samples uses an aluminum column to stack the sample / standard material in a quartz tube, and fills the upper gap in the quartz tube with quartz wool to reduce shaking and achieve precise control of the axial position of the sample / standard material.

[0027] 5. The present invention provides a method for 40 Ar- 39 In the neutron irradiation device for Ar dating samples, a certain gap is left between the upper plane of the blind hole of the aluminum can and the lower plane of the aluminum can cover, which is conducive to finding the correct cutting position for cutting and disintegration, shortening the cutting time, and reducing or even avoiding the damage of the quartz tube caused by cutting and disintegration.

[0028] 6. The present invention provides a method for 40 Ar- 39 The neutron irradiation device for Ar dating samples can weld a lifting ring or a long rod on the aluminum can cover to facilitate lifting and grabbing during operations in and out of the pile. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0030] Figure 1 A cross-sectional view of an aluminum can according to an embodiment of the present invention;

[0031] Figure 2 A cross-sectional view of an aluminum cover according to an embodiment of the present invention;

[0032] Figure 3 A schematic diagram of a quartz tube and internal stacking according to an embodiment of the present invention;

[0033] Figure 4 A top view of an aluminum can according to another embodiment of the present invention;

[0034] Figure 5 Another embodiment of the present invention is Figure 4 Middle AA section view;

[0035] Figure 6 A schematic diagram of the aluminum cover structure of another embodiment of the present invention;

[0036] Figure 7 A schematic diagram of assembling an aluminum can and an aluminum cover according to another embodiment of the present invention;

[0037] Figure 8A schematic diagram of a quartz tube and internal stacking according to another embodiment of the present invention.

[0038] Marks and corresponding parts names in the attached drawings:

[0039] 1-aluminum can, 2-blind hole, 3-quartz tube, 4-aluminum cover, 5-positioning heat conductor, 6-cadmium skin, 7-quartz wool. DETAILED DESCRIPTION

[0040] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that these specific details are not necessarily employed to practice the present invention. In other embodiments, in order to avoid obscuring the present invention, well-known structures, circuits, materials, or methods are not specifically described.

[0041] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. In addition, it will be appreciated by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0042] In the description of the present invention, the directions or positional relationships indicated by terms such as “front”, “rear”, “left”, “right”, “up”, “down”, “vertical”, “horizontal”, “high”, “low”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the scope of protection of the present invention.

[0043] Embodiment 1:

[0044] This embodiment 1 provides a method for 40 Ar- 39 Neutron irradiation device for Ar dating samples, such as Figure 1-Figure 3 As shown, Figure 1 A cross-sectional view of an aluminum can 1 provided by the present invention; Figure 2 A cross-sectional view of the aluminum cover 4 provided by the present invention; Figure 3 The quartz tube 3 provided by the present invention and the internal stacking diagram are not shown in Figure 3In the figure, the left side shows a stacking method of stacking one sample / standard substance between adjacent aluminum columns, and the right side shows a stacking method of stacking two samples / standard substances between adjacent aluminum columns; specifically, it includes:

[0045] An aluminum can 1, wherein the aluminum can 1 is a fully solid aluminum can body, and a plurality of blind holes 2 are opened along the axial direction of one end surface of the aluminum can 1, wherein the blind holes 2 are parallel to the axis of the aluminum can 1 and are used to place a quartz tube 3;

[0046] An aluminum cover 4, the aluminum cover 4 is used to seal one end of the aluminum can 1;

[0047] The quartz tube 3 has sizes matching those of the blind hole 2; a plurality of positioning heat-conducting members 5 are placed in the quartz tube 3 along its length, and the positioning heat-conducting members 5 are used to position and install the sample.

[0048] Compared with the prior art, 40 Ar- 39 During the in-pile irradiation of Ar dating samples, neutrons and gamma photons in the nuclear reactor interact with the dating samples and the irradiation device, depositing energy therein and causing them to heat up. In order to avoid the samples and irradiation devices from melting or breaking due to excessive temperatures, thereby causing more serious situations such as failure of the irradiation test and adverse effects on the safety of reactor operation, it is necessary to control the irradiation temperature; and the neutron flux in the reactor irradiation channel is different in both the axial and radial directions. This difference causes certain differences in the neutron flux received by samples placed at different positions. In the axial direction, the neutron flux in the irradiation channel is distributed in a cosine curve. The area with the highest axial neutron flux is generally the middle area of ​​the active section, and decreases towards the two ends of the active section. In the radial direction, the neutron flux in the reactor is distributed in a zero-order Bessel function. This non-uniformity will inevitably have an adverse effect on the uniformity of the neutron flux received by samples at different axial positions at the same radial position and at different positions in the same radial plane in the sample irradiation device. The present invention provides a method for 40 Ar- 39 Argon dating sample neutron irradiation device can be used in research reactors 40 Ar- 39 Neutron irradiation of Ar dating samples, the present invention can not only meet 40 Ar- 39 The irradiation temperature range required for Ar dating samples can also ensure the stability and accuracy of the dating samples in the axial and radial positions.

[0049] In the specific scheme, a cylindrical aluminum can 1 and an aluminum cover 4 are included. The cylindrical aluminum can 1 and the aluminum cover 4 can be assembled together to form the main body of the irradiation device, which is used to accommodate the quartz tube 3 and the sample / standard substance inside it, and separate the sample / standard substance from the water environment in the irradiation channel. The aluminum can 1 is a solid cylindrical aluminum block, and a plurality of blind holes 2 are dug out on its end surface. A plurality of quartz tubes 3 can be arranged through the blind holes 2, wherein the number of blind holes 2 is equal to the number of quartz tubes 3, and the radius of the blind hole 2 matches the radius of the quartz tube 3. The number and arrangement position of the quartz tubes 3 can be determined according to the irradiation needs. Since the aluminum can 1 and the aluminum cover 4 are both made of aluminum, this is because the neutron scattering cross-section and neutron absorption cross-section of aluminum are very small, and the interference and influence on the neutron field in the reactor are very small. At the same time, the thermal conductivity of aluminum is large, which can effectively reduce the irradiation temperature and realize the control of the irradiation temperature; a plurality of positioning heat-conducting parts 5 are arranged inside the quartz tube 3 along its length direction. Through the heat conduction and positioning effects of the positioning heat-conducting parts 5, the sample can be positioned and installed in the axial direction of the quartz tube 3. In this way, by accurately determining the axial position of the sample and the standard material, it is beneficial to more accurately study the neutron flux distribution characteristics, and it also plays a heat conduction role.

[0050] The above scheme aims to achieve: the cylindrical aluminum can 1 and the aluminum can 1 cover can be assembled together to form the main body of the irradiation device, which is used to accommodate the quartz tube 3 and the sample / standard material inside, and separate the sample / standard material from the water environment in the irradiation channel. The use of aluminum metal parts such as the fully solid aluminum can 1 and the aluminum cover 4 can improve the thermal conductivity of the device, reduce the irradiation temperature, and reduce the disturbance of the neutron field in the reactor caused by the irradiation device. In addition, the radial position of the sample and the standard material can be accurately determined through the several blind holes 2 inside the aluminum can 1, and the axial position of the sample and the standard material can be accurately determined through the several positioning heat-conducting parts 5 arranged inside the quartz tube 3 along its length direction. Therefore, by accurately positioning the axial position and radial position of the sample and the standard material, the standard material of known age can be placed at different axial positions and different radial positions to monitor the neutron flux, obtain the neutron flux change curve, and then accurately calculate the neutron flux actually received by the sample to be tested.

[0051] As a method of facilitating rapid positioning of samples and improving the control accuracy of irradiation temperature, the positioning heat-conducting member 5 is an aluminum column, the diameter of which is compatible with the inner diameter of the quartz tube 3, and a plurality of the aluminum columns are placed in the quartz tube 3 and arranged in sequence along the axial direction of the quartz tube 3; the adjacent aluminum columns are used to clamp the sample. During installation, the sample and the aluminum column can be directly placed in sequence, and the heat conduction and irradiation temperature control can be further achieved through the aluminum column, and the height of the aluminum column, the height of the sample / standard material, the number of stacking, the arrangement order, etc. can be determined according to the irradiation needs.

[0052] In order to realize the detection of multiple data and improve its functional diversity, at least one layer of samples is set between adjacent aluminum columns; for example, K2SO4 and CaF2 can be placed between adjacent aluminum columns, and K2SO4 and CaF2 are used to measure and obtain 40 K(n,p) 40 Ar, 40 Ca(n,nα) 36 Correction factor for side reactions of Ar.

[0053] In order to achieve stable installation of the quartz tube 3 and reduce the shaking of the quartz tube 3 in the axial direction, the quartz tube 3 is placed in the blind hole 2 with its opening facing downward, and the gap between the end of the quartz tube 3 and the end of the blind hole 2 is filled with quartz wool 7. The aluminum can 1 is used to control the position of the quartz tube 3 in the axial and radial directions to ensure that the quartz tube 3 is located in the same radial plane and is not tilted.

[0054] In order to ensure the stability of the internal sample and aluminum column and improve the thermal conductivity, the end of the quartz tube 3 away from the tube mouth is filled with quartz wool 7; the sample is wrapped and compacted with high-purity aluminum foil. In this solution, in addition to the containment function, the aluminum foil can also play a good thermal conductivity role; the quartz wool 7 can reduce the axial shaking of the sample / standard substance. The sample / standard substance is wrapped and compacted with high-purity aluminum foil, stacked together with the aluminum column in the quartz tube 3, and the upper gap in the quartz tube 3 is filled with quartz wool 7, and finally the quartz tube 3 is sealed under vacuum conditions.

[0055] Because in 40 Ar- 39 During the in-pile irradiation of Ar dating samples, in addition to the target nuclear reaction 39 K(n,p) 39 In addition to Ar, there are also side reactions that can interfere with the dating results. 40 K(n,p) 40 Ar, 40 Ca(n,nα) 36 Ar, the side reaction 40 K(n,p) 40 Ar has a large absorption cross section for thermal neutrons with energy E < 0.01 MeV; and the target reaction 39 K(n,p) 39 Ar can occur when the neutron energy is >1MeV. Therefore, in order to ensure 39 In order to increase the yield of Ar and reduce the interference of side reactions, it is necessary to shield thermal neutrons with energy E<0.01MeV, and the configuration is as follows: the outer sides of the aluminum can 1 and the aluminum cover 4 are covered with a layer of cadmium skin 6. Cadmium has a large absorption cross section for thermal neutrons with energy less than 0.414eV, thereby shielding thermal neutrons and reducing side reactions. 40 K(n,p) 40Interference from Ar.

[0056] Since the irradiation device and the sample have high radioactivity after irradiation, it is necessary to cut and disassemble the irradiation device in the hot room and take out the quartz tube 3 containing the sample / standard substance for subsequent 40 Ar / 39 Ar ratio measurement. The cutting and disintegration in the hot chamber needs to be observed through a shielded window and operated by a manipulator, which increases the difficulty of operation and reduces the accuracy of operation compared with the operation outside the hot chamber. In order to facilitate cutting and disintegration after irradiation and reduce or even avoid the damage of the quartz tube 3 caused by cutting and disintegration, it is necessary to carry out design research on the irradiation device. It is set as follows: a gap is left between the end face of the aluminum can 1 at the opening of the blind hole 2 and the bottom plane of the aluminum cover 4. And there is a certain distance between the end face of the aluminum can 1 at the opening of the blind hole 2 and the bottom plane of the aluminum cover 4. In this way, compared with the absence of a gap, the presence of a gap helps to find the lower knife position for cutting and disintegration after irradiation when cutting and disintegrating in the hot chamber, reduce the cutting area, shorten the cutting time, and reduce or even avoid the damage of the quartz tube 3 caused by cutting and disintegration.

[0057] To improve the connection strength, the aluminum can 1 and the aluminum cover 4 are sealed and welded. During installation, the aluminum can 1 and the aluminum can 1 cover are welded and sealed and leak-detected to confirm that the welding is intact, and then placed in the irradiation channel for irradiation.

[0058] In order to facilitate the hoisting operation when entering and exiting the pile, a hoisting piece is welded on the top of the aluminum cover 4. The hoisting piece can be a hoisting ring or a long rod welded on the aluminum cover 4 for hoisting and grabbing.

[0059] In summary, the present invention provides a method for 40 Ar- 39 Ar neutron irradiation device for dating samples can be used in research reactors 40 Ar- 39Neutron irradiation test of Ar dating samples; the device can provide functions such as absorbing thermal neutrons, reducing irradiation temperature, accurately controlling the axial and radial positions of samples and standard materials, and improving the convenience of cutting and disintegration after irradiation and entering and exiting the pile. The device of the present invention is composed of an aluminum can 1, a cadmium skin 6, an aluminum cover 4, a quartz tube 3, a sample to be tested, a standard material, an aluminum column, and quartz wool 7; the cadmium skin 6 is covered on the outer side wall of the aluminum can 1 and the cover of the aluminum can 1; a blind hole 2 is dug in the aluminum can 1 for placing the quartz tube 3; the aluminum foil wraps the sample / standard material and is stacked in the quartz tube 3 together with the aluminum column. The present invention uses cadmium skin 6 to shield thermal neutrons, thereby reducing the interference of side reactions on the dating results; aluminum metal parts are used to reduce the interference of the irradiation device on the neutron field in the reactor, and to improve the thermal conductivity of the device and control the irradiation temperature; aluminum cans 1 and aluminum columns with blind holes 2 are used, and the gaps are filled with quartz wool 7 to control the axial and radial positions of samples and standard materials; a certain gap is left between the aluminum can 1 and the cover of the aluminum can 1, which is conducive to finding the cutting position for cutting and disintegration, shortening the cutting time, and reducing or even avoiding the damage of the quartz tube 3 caused by cutting and disintegration; a lifting ring or a long rod can be welded on the cover of the aluminum can 1 to facilitate the lifting and grabbing of the operation of entering and exiting the pile. The present invention can not only achieve 40 Ar- 39 The shielding of thermal neutrons during the irradiation of Ar dating samples meets the requirements. 40 Ar- 39 The irradiation temperature range required for Ar dating sample irradiation can also ensure the stability and accuracy of the dating samples in the axial and radial positions, and improve the convenience of cutting, disassembly, and entering and exiting the pile after irradiation.

[0060] Embodiment 2:

[0061] This embodiment 2 further defines the embodiment 1 and provides a specific implementation method. Figure 4 -Attached Figure 8 shown.

[0062] The size of the cylindrical aluminum can 1 is 32mm in outer diameter and 115mm in height. The outer wall of the aluminum can 1 is covered with a 0.5mm thick cadmium skin 6 to shield thermal neutrons. A C tube and 7 M tubes are arranged in the aluminum can 1, of which the C tube is located at the center of the aluminum can 1, that is, on the axis. The 7 M tubes are evenly distributed along the C tube, and the center of the M tube is 10.6mm away from the center of the C tube. 8 quartz tubes 3 are fixed by the aluminum can 1, and the aluminum can 1 is made of a whole cylindrical aluminum block with 8 evenly distributed Φ8.5mm blind holes 2. After the quartz tube 3 is inserted into the blind hole 2 in the aluminum can 1, quartz wool 7 is filled in the upper gap of the blind hole 2. Then the aluminum can 1 and the aluminum cover 4 are welded and sealed and X-ray flaw detection is performed to confirm that the welding is intact, and then it is placed in the reactor irradiation channel for irradiation. The inner diameter of the upper part of the aluminum can 1 is 30.4mm, and the inner diameter of the lower part of the aluminum cover 4 is 30.5mm, so that they can fit each other. The upper space of the aluminum can 1 is 10 mm high, and the lower part of the aluminum cover 4 is 5 mm thick. After welding and sealing, a 5 mm gap is formed, which is convenient for disassembly and cutting after irradiation. A lifting ring is welded on the aluminum cover 4 to facilitate lifting and grabbing when entering and exiting the pile.

[0063] After the sample / standard substance is wrapped and compacted with high-purity aluminum foil, it is sealed in a quartz tube 3 under vacuum conditions. The outer diameter of the quartz tube 3 is 8 mm and the inner diameter is 6 mm. The aluminum column is 5052 aluminum, which is used to fix the sample / standard substance and accurately control its axial position in the quartz tube 3. Figure 8 As shown, the left side is C tube, with K2SO4 and CaF2 sandwiched between adjacent aluminum columns, and the right side is M tube, with feldspar, muscovite and biotite sandwiched between adjacent aluminum columns. The standard material is biotite mineral, which is used to monitor the axial and radial neutron injection rate distribution. K2SO4 and CaF2 are used to measure and obtain 40 K(n,p) 40 Ar, 40 Ca(n,nα) 36 The side reaction correction factor of Ar. The size of the biotite, K2SO4 and CaF2 samples is Φ6mm×2mm, the size of the C tube aluminum column is Φ6mm×10mm, and the size of the M tube aluminum column is Φ6mm×7mm.

[0064] The irradiation device was placed in the 1# irradiation channel of the Minjiang Test Reactor MJTR for irradiation. According to calculations, the cadmium skin 6 in the irradiation device can absorb up to 95% of thermal neutrons; after changing from an empty aluminum can 1 to an integrated aluminum can 1, the sample temperature in the C tube dropped from ~350℃ to ~120℃, the standard material temperature in the M tube dropped from ~320℃ to ~150℃, the quartz tube 3 temperature dropped from ~350℃ to 90℃, and the aluminum column temperature in the quartz tube 3 dropped from ~350℃ to ~140℃, indicating that the integrated aluminum can 1 can effectively improve the thermal conductivity of the irradiation device and control the irradiation temperature.

[0065] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for 40 Ar- 39 The neutron irradiation device for Ar dating samples is characterized by: include: An aluminum can (1), wherein the aluminum can (1) is a fully solid aluminum can body, and a plurality of blind holes (2) are opened along the axial direction of one end surface of the aluminum can (1), wherein the blind holes (2) are parallel to the axis of the aluminum can (1) and are used to place a quartz tube (3); An aluminum cover (4), the aluminum cover (4) being used to seal one end of the aluminum can (1); A quartz tube (3), wherein the sizes of the quartz tube (3) and the blind hole (2) are matched; a plurality of positioning heat-conducting members (5) are placed inside the quartz tube (3) along its length direction, and the positioning heat-conducting members (5) are used to position and install the sample.

2. A method for 40 Ar- 39 The neutron irradiation device for Ar dating samples is characterized by: The positioning heat-conducting member (5) is an aluminum column, the diameter of which is matched to the inner diameter of the quartz tube. A plurality of the aluminum columns are placed in the quartz tube and are arranged in sequence along the axial direction of the quartz tube (3); adjacent aluminum columns (5) are used to clamp samples.

3. A method for 40 Ar- 39 The neutron irradiation device for Ar dating samples is characterized by: At least one layer of samples is arranged between adjacent aluminum columns (5).

4. A method for 40 Ar- 39 The neutron irradiation device for Ar dating samples is characterized by: The quartz tube (3) is placed in the blind hole (2) with its opening facing downward, and the gap between the end of the quartz tube (3) and the end of the blind hole (2) is filled with quartz wool (7).

5. A method for 40 Ar- 39 The neutron irradiation device for Ar dating samples is characterized by: The end of the quartz tube (3) away from the tube opening is filled with quartz wool (7).

6. A method for 40 Ar- 39 The neutron irradiation device for Ar dating samples is characterized by: The sample was wrapped and compacted with high purity aluminum foil.

7. A method for use according to any one of claims 1 to 6. 40 Ar- 39 The neutron irradiation device for Ar dating samples is characterized by: The outer sides of the aluminum can (1) and the aluminum cover (4) are both covered with a layer of cadmium skin (6).

8. A method for use according to any one of claims 1 to 6 40 Ar- 39 The neutron irradiation device for Ar dating samples is characterized by: A gap is left between the end surface of the aluminum can (1) at the opening of the blind hole (2) and the bottom plane of the aluminum cover (4).

9. A method for use according to any one of claims 1 to 6 40 Ar- 39 The neutron irradiation device for Ar dating samples is characterized by: The aluminum can (1) and the aluminum cover (4) are sealed and welded.

10. A method for use according to any one of claims 1 to 6 40 Ar- 39 The neutron irradiation device for Ar dating samples is characterized by: A hanging piece is welded to the top of the aluminum cover (4).

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