CN110320224B - Concrete flaw detector and flaw detector - Google Patents
Concrete flaw detector and flaw detector Download PDFInfo
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- CN110320224B CN110320224B CN201910730053.1A CN201910730053A CN110320224B CN 110320224 B CN110320224 B CN 110320224B CN 201910730053 A CN201910730053 A CN 201910730053A CN 110320224 B CN110320224 B CN 110320224B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/20—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
- G01N23/20008—Constructional details of analysers, e.g. characterised by X-ray source, detector or optical system; Accessories therefor; Preparing specimens therefor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/20—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
- G01N23/203—Measuring back scattering
- G01N23/204—Measuring back scattering using neutrons
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2223/00—Investigating materials by wave or particle radiation
- G01N2223/05—Investigating materials by wave or particle radiation by diffraction, scatter or reflection
- G01N2223/053—Investigating materials by wave or particle radiation by diffraction, scatter or reflection back scatter
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2223/00—Investigating materials by wave or particle radiation
- G01N2223/10—Different kinds of radiation or particles
- G01N2223/106—Different kinds of radiation or particles neutrons
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2223/00—Investigating materials by wave or particle radiation
- G01N2223/60—Specific applications or type of materials
- G01N2223/646—Specific applications or type of materials flaws, defects
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Abstract
The invention discloses a concrete flaw detection device, which comprises a neutron source (1), four detectors (2) and a shielding body (3); the neutron source (1) is arranged in the center of the shielding body (3), the shielding body (3) is coated on the periphery of the neutron source, and the four detectors (2) are uniformly distributed on the outer side of the shielding body (3) at equal intervals along the circumferential direction of the center of the neutron source (1); the radius of the shielding body (3) is 15-20 cm, the height of the shielding body is 10-15 cm, and the distance from the front surface of the neutron source (1) to the front detection surface of the shielding body (3) is 1-2 cm; the shielding body (3) is made of polyethylene doped with boron carbide, and the mass content of the boron carbide is 10-15%; the shielding body (3) is coated with a lead protective layer (4), and the thickness of the lead protective layer (4) is 1-2 cm; a movable cover (5) is arranged on the lead protection layer (4) of the front detection surface of the shielding body (3). The detection efficiency is improved, and the depth and transverse position information of the defects in the concrete inner area can be obtained through data analysis of the detection result.
Description
Technical Field
The invention relates to a nuclear technology, belongs to the technical field of nondestructive testing, and particularly relates to a concrete flaw detection device and a flaw detector for nondestructive testing of reinforced concrete structures by using a neutron backscattering method.
Background
Because neutron rays have stronger penetrating power than X and gamma rays to most metal materials and have strong scattering performance to hydrogen-containing materials. Neutron rays have many applications: such as inspection of internal defects of the material by neutron radiography, measurement of water content in the heat insulating material, measurement of hydrogen content in the steel, measurement of the gap inside the steel, and measurement of residual stress by neutron analysis.
At present, the technology for reinforced concrete by utilizing a neutron backscattering method is not mature, the shielding and detection schemes for generating neutrons are not perfect, and the concrete flaw detection device provided by the patent researches the shielding and detection schemes and provides a solution.
Disclosure of Invention
The invention aims to provide a concrete flaw detection device, which improves the detection efficiency, and can obtain the information of the depth and the transverse position of the defect in the concrete internal area by analyzing the data of the detection result.
The purpose of the invention is realized by the following technical scheme:
a concrete flaw detection device comprises a neutron source 1, four detectors 2 and a shielding body 3;
the neutron source 1 is arranged in the center of the shielding body 3, the shielding body 3 is coated on the periphery of the neutron source 1, and the four detectors 2 are uniformly distributed on the outer side of the shielding body 3 along the circumferential direction of the center of the neutron source 1 at equal intervals;
the radius of the shielding body 3 is 15-20 cm, the height of the shielding body is 10-15 cm, and the distance from the front surface of the neutron source 1 to the detection surface in front of the shielding body 3 is 1-2 cm;
the shielding body 3 is made of polyethylene doped with boron carbide, and the mass content of the boron carbide is 10-15%;
the shielding body 3 is coated with a lead protection layer 4, and the thickness of the lead protection layer 4 is 1-2 cm; a movable cover 5 is arranged on the lead protection layer 4 of the detection surface in front of the shielding body 3.
Preferably, a collimator 6 is arranged in front of the shielding body 3.
Preferably, the neutron source 1 adopts an americium beryllium neutron source, the nominal activity is 1.85GBq, and the neutron emissivity is 1.00 multiplied by 10^5 n/s.
Preferably, the detector 2 adopts a BF3 proportional counter tube.
Preferably, the radius of the shielding body 3 is 15cm, the height of the shielding body is 10cm, and the distance from the front surface of the neutron source 1 to the detection surface in front of the shielding body 3 is 1 cm.
Preferably, the content of the boron carbide is 10% by mass.
A flaw detector comprises the concrete flaw detection device.
According to the technical scheme provided by the invention, the concrete flaw detection device provided by the embodiment of the invention improves the detection efficiency, and the data analysis of the detection result can obtain the depth and transverse position information of the defects in the concrete inner area.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a schematic front view of a concrete inspection apparatus according to an embodiment of the present invention;
fig. 2 is a schematic bottom view of a concrete inspection apparatus according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a neutron source of a concrete inspection apparatus according to an embodiment of the present invention;
FIG. 4 is a diagram showing the influence of the specific gravity of backscattered particles of a flaw detector according to an embodiment of the present invention;
FIG. 5 is a diagram showing the relationship between the detector count and the cavity depth of the flaw detector according to the embodiment of the present invention;
FIG. 6 is a diagram illustrating a general relationship between the detector count and the lateral position of a cavity of a flaw detector according to an embodiment of the present invention;
FIG. 7 is a first diagram of the relationship between the reading of the detector array of the flaw detector and the position of the cavity according to the embodiment of the present invention;
fig. 8 is a second diagram illustrating a relationship between a reading of a detector array of the flaw detector and a position of a cavity according to the embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
Embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
In the aspect of a concrete structure with a metal material covered on the surface, because of strong penetrating power, neutron rays firstly penetrate through a steel plate on the surface and enter concrete, then scatter with hydrogen atoms of crystal water in the concrete, and are backscattered to enter a detector to be detected, and the internal defects of the concrete can be detected through the reading of the detector.
Example one
As shown in fig. 1 and 2, a concrete flaw detector as a probe installed on a flaw detector and suitable for detecting flaws in a concrete structure with a surface covered with a steel plate with a certain thickness comprises a neutron source 1, four detectors 2 and a shielding body 3; the neutron source 1 is arranged at the center of the shielding body 3, the shielding body 3 is coated on the periphery of the shielding body, and the four detectors 2 are uniformly distributed on the outer side of the shielding body 3 along the central circumference of the neutron source 1 at equal intervals. In particular, the probe can be mounted in a base body 7, and the base body 7 can be a shell of the probe and the like. The flaw detector also comprises a plurality of lines 8, a data acquisition interface and the like, data are transmitted to a computer and analyzed through software, the known technology is adopted, details are not described, and the protection scope of the embodiment lies in a concrete flaw detection device serving as a probe.
The neutron source 1 adopts an americium beryllium neutron source 241Am-Be, the nominal activity is 1.85GBq, and the neutron emissivity is 1.00 multiplied by 10^5 n/s.
A specific americium-beryllium neutron source may have a suitable specification selected according to national standards, as shown in fig. 3:
φ1＝16mm；φ2＝10.4mm；h1＝19mm；h2＝10mm；
Φ1the outside diameter of the neutron source shell;
Φ2inner diameter of the neutron source emission area;
h1neutron source housing height;
h2the height of the emission region of the neutron source;
in fig. 3, the lower face is the front face of the neutron source 1, pointing towards the object to be tested, for flaw detection.
Meanwhile, when the neutron emissivity control device is used, the appropriate neutron emissivity can be selected according to actual conditions. An americium-beryllium neutron source is approved and supervised by relevant national departments for production, the neutron source 1 is positioned at the center of a concrete flaw detection device, and the concrete flaw detection device is of a central symmetrical structure.
The radius of the shielding body 3 is 15-20 cm, the height is 10-15 cm, the radius is 15cm, and the height is 10cm, so that the requirements of the patent can be met. The distance between the front surface of the neutron source 1 and the detection surface in front of the shielding body 3 is 1-2 cm; and a collimator 6 is arranged in front of the shielding body 3. I.e. a circular hole may be left in front of the shield 3 for the collimator 6. The function of the collimator 6 is to emit the neutrons emitted by the neutron source in a narrow beam towards the inspected area, and the presence of the collimator reduces the shielding of the neutrons entering the concrete side. This is a common general structure of the prior art, and can be used when various particle sources are involved, and will not be described in detail.
The shielding body 3 is made of polyethylene doped with boron carbide, and the mass content of the boron carbide is 10-15%; in this example, the shield 3 is also called a preliminary shield, in order to make the neutron count obtained by the detector from the defect of the concrete structure have a higher proportion and make the detector count sufficiently, the axial thickness of the shield is about 15cm, the height can be controlled to be about 10cm according to actual needs, and the higher the boron content of the material is, the larger the proportion of the backscattered neutrons obtained by the detector is, but the influence of the boron content on the proportion is smaller than the influence of the thickness of the shield, and considering the cost, the optimal material has a boron carbide mass content of 10%. The whole transverse section of the shield 3 is circular ring-shaped, and the neutron source is contained in the inner circle.
The shielding body 3 is coated with a lead protection layer 4, and the thickness of the lead protection layer 4 is 1-2 cm; usually 1cm can suffice. A movable cover 5 is arranged on the lead protection layer 4 of the detection surface in front of the shielding body 3. The movable cover 5 is opened or taken down when the device works, and the movable cover 5 is closed or covered when the device does not work. The removable cover 5 is also lead and is part of the lead shielding layer 4, which protects the human body from radiation.
The four detectors 2 are uniformly distributed on the outer side of the shielding body 3 along the central circumference of the neutron source 1 at equal intervals; the detector 2 adopts a BF3 proportional counter tube. The BF3 proportional counting detector array is formed, BF3 proportional counting tubes are sold in the market and placed in four directions of the periphery of the shielding body 3, the number of the counting tubes in each direction can be adjusted, and the detection effect is better.
Example two
A flaw detector comprising the concrete flaw detection apparatus according to the first embodiment.
The working process of the flaw detector is as follows: the concrete flaw detector of the flaw detector is arranged on the surface of a detected object (concrete), flaw detection is started, neutrons detected by the four groups of detectors within a period of time are counted by a computer, the result is finally counted and analyzed, and whether the detected object has defects or not can be analyzed according to the counting of the detectors and the response graph of the depth and the position of the cavity. The neutron backscatter inspection instrument is suitable for inspection of concrete structures covered with steel plates of a certain thickness on the surface.
As shown in FIG. 4, the initial shield design with a radius of 15cm and a B4C mass content of 0.1 was chosen to achieve a 20% backscatter particle specific weight, which makes the response of the detector readings for neutron backscatter inspection to defects more pronounced.
The special characteristics of the invention in the field of neutron backscatter inspection of reinforced concrete are that the proper thickness and boron content ratio of a primary shield made of boron-doped polyethylene are selected and designed, the BF3 proportional counter detector is arranged at equal intervals in four circumferential directions, and finally Monte Carlo software is used for simulating the response of the detector array under different defects, so that the reading result of the detector corresponds to the specific position of the defect finally obtained by detection. Wherein: the transverse thickness of a relatively proper primary shielding body is about 15cm, the mass content of boron carbide in the material is 0.1, the corresponding relation graph of the detector array to the defect position is shown in fig. 5 and 6, the counting result of the detector simulated by the Monte Carlo program in the graph is presented in the form of normalized flux density, and the size of the counting result represents the counting size of the detector.
For the arrangement design of four detectors at equal intervals on the outer circumference of the primary shielding body, the detector responses to the oblique change and the transverse change of the horizontal position of the defect are shown in fig. 7 and fig. 8.
Most of neutrons emitted by the neutron source 1 enter the detector through the flaw detection area in a back scattering mode, the neutrons record information of the flaw detection area, and part of the neutrons do not enter the flaw detection area and are directly received by the detector, so that the correlation between the indication number of the detector and whether holes exist in the flaw detection area or not can be improved by improving the specific gravity of the back scattering neutrons, and the effect of improving the efficiency of the whole flaw detection process is achieved.
Through simulation of Monte Carlo software on actual flaw detection conditions, a relational graph of backscatter particles and a shielding body and a relational graph of concrete defects and detector data under the flaw detection conditions are obtained. As shown in fig. 4 and 5, as can be seen from the specific gravity influence graphs of the backscatter particles, when the inner diameter of the shield is gradually increased, the specific gravity of the backscatter particles is increased first, and when the inner diameter is larger, the specific gravity of the backscatter particles is increased slowly and tends to be stable; the specific gravity of the back scattering particles is in an increasing state along with the increase of the boron content, but the influence degree of the boron content on the specific gravity of the back scattering particles is smaller; however, the shield radius is too large, which reduces the total particle count entering the detector. By combining the analysis and according to the data of the backscatter particle specific gravity image, a shield with a radial thickness of 15cm and a boron content of about 10% is selected, thereby achieving the effect of improving the efficiency of the flaw detection process.
After the detector data is obtained, the data needs to be analyzed to obtain a result. As can be seen from the graph of the relationship between the detector count of the flaw detector and the depth of the cavity, as shown in fig. 5: under the same condition, when the radius of the cavity is increased, the number of the detectors is reduced along with the increase of the depth of the cavity and tends to be in an exponential decay trend, and when the depth of the defect of the cavity is larger, the speed of reducing the number of the detectors is slower. Therefore, if a large defect or a deep cavity exists in the inspected area, the number of the probe is small, and vice versa, and the corresponding relationship is shown in a graph of the relationship between the probe count and the depth of the cavity, as shown in fig. 5.
In order to locate the defect region, the position of the lower cavity needs to be analyzed through data information of the detector, and through a general relation graph between the count of the detector and the transverse position of the cavity, as shown in fig. 6, the position information of the cavity displayed by the number of a single detector can be seen: when a hole is detected below the flaw detector, the reading of the detector is gradually increased and then gradually decreased along with the gradual increase of the distance between the position of the hole and the source. When the position of the hollow hole is in the middle of the position of the hollow hole and the position of the detector, the counting number of the detector reaches the highest value, and the specific change relationship is shown in the relationship graph.
Through two graphs of the relationship between the reading of the detector array and the position of the cavity, as shown in fig. 7 and 8, the data information of the whole detector can be analyzed: when the cavity is located in the included angle area of two adjacent detectors, the counts of the two detectors are generally higher than those of the other two detectors, and as the position of the cavity is gradually far away from the neutron source, the readings of the two detectors in the area are not generally monotonously increased like the readings of the other detectors, but are increased and then decreased; when a hole is located beneath four detector arrays, the size of each detector reading is substantially inversely proportional to the distance of the hole from the detector.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (6)
1. A concrete flaw detection device is characterized in that: comprises a neutron source (1), four detectors (2) and a shielding body (3);
the neutron source (1) is arranged in the center of the shielding body (3), the shielding body (3) is coated on the periphery of the neutron source, and the four detectors (2) are uniformly distributed on the outer side of the shielding body (3) at equal intervals along the circumferential direction of the center of the neutron source (1);
the radius of the shielding body (3) is 15-20 cm, the height of the shielding body is 10-15 cm, the distance between the front surface of the neutron source (1) and the front detection surface of the shielding body (3) is 1-2 cm, the neutron source (1) adopts an americium-beryllium neutron source, the nominal activity is 1.85GBq, and the neutron emissivity is 1.00 multiplied by 10^5 n/s;
the shielding body (3) is made of polyethylene doped with boron carbide, and the mass content of the boron carbide is 10-15%;
the shielding body (3) is coated with a lead protective layer (4), and the thickness of the lead protective layer (4) is 1-2 cm; a movable cover (5) is arranged on the lead protection layer (4) of the front detection surface of the shielding body (3).
2. The concrete testing apparatus according to claim 1, wherein a collimator (6) is provided in front of the shield (3).
3. The concrete testing apparatus according to claim 1 or 2, characterized in that the detector (2) adopts BF3 proportional counter tube.
4. The concrete testing apparatus according to claim 1 or 2, wherein said shield (3) has a radius of 15cm and a height of 10cm, and the distance from the front of said neutron source (1) to the front detection surface of said shield (3) is 1 cm.
5. The concrete testing apparatus according to claim 1 or 2, wherein the boron carbide is 10% by mass.
6. A flaw detector is characterized in that: including a concrete inspection apparatus according to any one of claims 1 to 5.
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