Secondary pre-diffraction high-precision X-ray fluorescence analysis system

Abstract

The utility model discloses a secondary pre-diffraction high-precision X-ray fluorescence analysis system which comprises an X-ray tube used for generating an X-ray source, a detector and a measuring cell used for storing feed liquid to be measured, a first collimator is arranged between the X-ray tube and the measuring cell, a first diffraction crystal is arranged below the measuring cell, and a second collimator is arranged below the first diffraction crystal. A second diffraction crystal is arranged obliquely above the first diffraction crystal, a second collimator is arranged between the second diffraction crystal and the detector, and the signal output end of the detector is connected with a computer system used for X-ray tube power control and measurement result analysis and calculation. According to the utility model, the characteristic X-ray of Pu in the material liquid to be detected is subjected to monochromaticity through secondary diffraction of the first diffraction crystal and the second diffraction crystal, so that the detection limit of the concentration of Pu in the material liquid of the spent fuel post-treatment process can be delayed by one order of magnitude, high-precision analysis is realized, the problem of analysis of the concentration of Pu in the spent fuel post-treatment process is solved, the use effect is good, and the popularization and the use are convenient.

Description

Technical Field

[0001] The utility model belongs to the technical field of spent fuel post-processing radiochemical analysis, and in particular relates to a secondary pre-diffraction high-precision X-ray fluorescence analysis system. Background Art

[0002] In spent fuel reprocessing, Pu is an important nuclear material, and it needs to be accurately measured in process control analysis and nuclear material accounting. Radiochemical analysis technology is usually used to perform non-destructive analysis on low-content Pu liquid, and X-ray fluorescence analysis technology is commonly used. The principle is to use the X-rays emitted by the X-ray tube to stimulate the Pu element in the process liquid to emit characteristic X-rays, and then measure the intensity of the Lα1 characteristic X-rays (energy of 14.279keV) in the characteristic X-rays through the detector to calculate and determine the plutonium concentration in the process liquid. Since the liquid to be measured is the waste liquid of Pu product purification, the Pu content is very low, and the liquid itself has a high radioactivity, which interferes greatly with the measurement of low-energy X-rays, making its measurement very difficult.

[0003] The current detection limit of Pu concentration in process liquid by X-ray fluorescence analysis technology is 1 mg / L. When the concentration is lower, the error is large and the confidence is low. The reason is that the characteristic X-ray energy of uranium, neptunium, americium, strontium and yttrium is very close to that of plutonium, and the energy resolution of the SDD detector used for measurement has reached its limit at low-energy X-rays, and there is no detector with better resolution. Other methods with lower detection limits require offline sampling and sample preparation, which cannot meet the requirements of non-destructive testing. Utility Model Content

[0004] The technical problem to be solved by the utility model is to provide a secondary pre-diffraction high-precision X-ray fluorescence analysis system in view of the deficiencies in the above-mentioned prior art. The system has a simple structure, a reasonable design, and is easy to implement. The characteristic X-rays of Pu in the measured liquid are monochromated by the secondary diffraction of the first diffraction crystal and the second diffraction crystal, so that the detection limit of Pu concentration in the liquid of the spent fuel post-processing process can be extended by 1 order of magnitude, high-precision analysis can be achieved, the problem of Pu concentration analysis in the spent fuel post-processing process is solved, the use effect is good, and it is easy to promote and use.

[0005] In order to solve the above technical problems, the technical solution adopted by the utility model is: a secondary pre-diffraction high-precision X-ray fluorescence analysis system, including an X-ray tube for generating an X-ray source, a detector and a measuring cell for storing a measured liquid, a first collimator is arranged between the X-ray tube and the measuring cell, a first diffraction crystal is arranged below the measuring cell, a second diffraction crystal is arranged obliquely above the first diffraction crystal, a second collimator is arranged between the second diffraction crystal and the detector, and a signal output end of the detector is connected to a computer system for X-ray tube power control and measurement result analysis and calculation.

[0006] The above-mentioned secondary pre-diffraction high-precision X-ray fluorescence analysis system also includes a power supply for supplying power to the X-ray tube and the computer system.

[0007] In the above-mentioned secondary pre-diffraction high-precision X-ray fluorescence analysis system, the tube voltage range of the X-ray tube is 50kV to 100kV, the tube current range is 1mA to 5mA, and the focal spot size range is 0.1mm to 2mm.

[0008] In the above-mentioned secondary pre-diffraction high-precision X-ray fluorescence analysis system, the incident angle of the X-rays emitted by the X-ray tube relative to the plane of the material liquid to be measured in the measuring cell is 60°.

[0009] In the above-mentioned secondary pre-diffraction high-precision X-ray fluorescence analysis system, the first collimator is made of copper, and the diameter of the collimation hole of the first collimator is 4 mm to 10 mm.

[0010] In the above-mentioned secondary pre-diffraction high-precision X-ray fluorescence analysis system, a measuring window for X-ray transmission is arranged at the bottom of the measuring cell, the measuring window is made of boron carbide or carbon fiber, and the thickness of the measuring window is 2 mm.

[0011] In the above-mentioned secondary pre-diffraction high-precision X-ray fluorescence analysis system, the first diffraction crystal and the second diffraction crystal are both made of lithium fluoride crystal, germanium crystal or graphite crystal.

[0012] In the above-mentioned secondary pre-diffraction high-precision X-ray fluorescence analysis system, the second collimator is made of polytetrafluoroethylene, nylon or organic glass.

[0013] In the above-mentioned secondary pre-diffraction high-precision X-ray fluorescence analysis system, the detector adopts a FAST SDD detector.

[0014] Compared with the prior art, the utility model has the following advantages: the utility model has a simple system structure, a reasonable design, and is easy to implement. The characteristic X-rays of Pu in the measured liquid are monochromated through the secondary diffraction of the first diffraction crystal and the second diffraction crystal, so that the detection limit of Pu concentration in the liquid of the spent fuel post-processing process can be extended by 1 order of magnitude, high-precision analysis can be achieved, and the problem of Pu concentration analysis in the spent fuel post-processing process can be solved. The use effect is good and it is easy to promote and use.

[0015] The technical solution of the utility model is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the system composition of the utility model;

[0017] Figure 2This is a schematic diagram of the characteristic X-ray diffraction monochromaticity of the utility model.

[0018] Description of reference numerals:

[0019] 1—X-ray tube; 2—measuring cell; 3—first collimator;

[0020] 4—first diffraction crystal; 5—second diffraction crystal; 6—second collimator;

[0021] 7—Detector; 8—Computer system; 9—Power supply. DETAILED DESCRIPTION

[0022] like Figure 1 As shown, the secondary pre-diffraction high-precision X-ray fluorescence analysis system of the utility model comprises an X-ray tube 1 for generating an X-ray source, a detector 7 and a measuring cell 2 for storing a measured liquid, a first collimator 3 is arranged between the X-ray tube 1 and the measuring cell 2, a first diffraction crystal 4 is arranged below the measuring cell 2, a second diffraction crystal 5 is arranged obliquely above the first diffraction crystal 4, a second collimator 6 is arranged between the second diffraction crystal 5 and the detector 7, and a signal output end of the detector 7 is connected to a computer system 8 for power control of the X-ray tube 1 and analysis and calculation of measurement results.

[0023] In this embodiment, a power supply 9 for supplying power to the X-ray tube 1 and the computer system 8 is also included.

[0024] During specific implementation, since the influence of voltage change on the primary spectrum intensity and distribution is greater than that of current, the optimal working voltage and optimal working current of the power supply 9 should be determined first.

[0025] In this embodiment, the tube voltage of the X-ray tube 1 ranges from 50 kV to 100 kV, the tube current ranges from 1 mA to 5 mA, and the focal spot size ranges from 0.1 mm to 2 mm.

[0026] In specific implementation, the X-rays emitted by the X-ray tube 1 are continuous in energy, and the L-layer absorption limit of Pu is 23.1 keV. A verified target material should be selected, and the target material characteristic energy is close to the absorption limit. The target material should be adjusted through the filament current and tube voltage. When determining the optimal operating voltage and current, the bremsstrahlung continuous spectrum and the characteristic spectrum should be used to jointly excite the element to be measured to obtain high excitation efficiency. The target material is rhodium, palladium or silver.

[0027] In this embodiment, the incident angle of the X-rays emitted by the X-ray tube 1 relative to the plane of the measured liquid in the measuring pool 2 is 60°.

[0028] In this embodiment, the first collimator 3 is made of copper, and the diameter of the collimation hole of the first collimator 3 is 4 mm to 10 mm.

[0029] In specific implementation, the first collimator 3 is used to concentrate the X-ray beam and enhance the fluorescence intensity, and is made of copper with high purity.

[0030] In this embodiment, a measuring window for X-ray transmission is provided at the bottom of the measuring pool 2 . The measuring window is made of boron carbide or carbon fiber, and the thickness of the measuring window is 2 mm.

[0031] In specific implementation, the measuring cell 2 is provided with a measuring window on the measuring surface, and the measuring window is made of a light material with low blocking power to low-energy X-rays and a small atomic number. The measured liquid is a nitric acid solution or a 30% TBP-kerosene solution, and the measuring window should be resistant to nitric acid and organic solvents. The measured liquid itself has high radioactivity, and the measuring window should have a certain radiation resistance.

[0032] In this embodiment, the first diffraction crystal 4 and the second diffraction crystal 5 are both made of lithium fluoride crystal, germanium crystal or graphite crystal.

[0033] In specific implementation, the first diffraction crystal 4 and the second diffraction crystal 5 are both crystals that can cause Pu characteristic X-rays to undergo intercrystalline diffraction, and the X-rays are split into monochromatic colors by utilizing the property that X-rays that conform to the Bragg equation can diffract on crystals.

[0034] In this embodiment, the second collimator 6 is made of polytetrafluoroethylene, nylon or organic glass.

[0035] In a specific implementation, the second collimator 6 is made of a light material with a low atomic number, which shields low-energy X-rays and reduces interference to the detector 7 .

[0036] In this embodiment, the detector 7 is a FAST SDD detector.

[0037] In specific implementation, the FAST SDD detector has a high resolution for low-energy X-rays and excellent resolution indicators.

[0038] When the utility model is used, the X-ray tube 1 emits an X-ray beam, which is concentrated by the first collimator 3, and after the fluorescence intensity is enhanced, it is incident on the measured liquid. The characteristic X-ray energies of the interfering elements in the measured liquid are: uranium 13.613keV, neptunium 13.945keV, americium 14.618keV, strontium 14.164keV, and yttrium 14.957keV. The characteristic X-ray closest to the Pu characteristic X-ray is strontium, with a spacing of 0.115keV, the spacing between neptunium and americium is 0.334keV, and the spacing between yttrium is 0.678keV. Figure 2As shown, the X-rays emitted by the measured liquid are divergent in the 4π direction, and only the X-rays that meet the Bragg angle and enter the first diffraction crystal 4 can enter the detector 7. In the figure, the incident angles θ1 and θ2 are X-rays that meet the Bragg angle. The incident angle θ1 is the incident angle of the Pu characteristic X-ray, and the incident angle θ2 is the incident angle of other interfering X-rays that meet the Bragg angle. The first diffraction crystal 4 performs the first diffraction on the incident X-rays. Due to the different diffraction angles, the interfering X-rays and the characteristic X-rays to be measured are separated in space after diffraction, which plays a monochromatic role. Since the energy of the interfering X-rays and the characteristic X-rays to be measured is very close, the Bragg angle of the Pu characteristic X-rays is 7.45°, and the Bragg angle of the neptunium characteristic X-rays is 7.63°, one diffraction is not enough to separate them in space. The second diffraction crystal 5 performs a second diffraction on the X-rays diffracted from the first diffraction crystal 4 to further separate them in space. Finally, the X-rays enter the detector 7, and the detection limit of the Pu concentration in the spent fuel reprocessing process liquid is extended by at least one order of magnitude to 0.1 mg / L, which solves the problem of non-destructive analysis of the Pu concentration in the waste liquid and improves the analysis accuracy.

[0039] The above is only a preferred embodiment of the present invention and does not constitute any limitation to the present invention. Any simple modification, change and equivalent structural change made to the above embodiments according to the technical essence of the present invention shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A secondary pre-diffraction high-precision X-ray fluorescence analysis system, characterized in that: The invention comprises an X-ray tube (1) for generating an X-ray source, a detector (7) and a measuring pool (2) for storing a measured liquid, wherein a first collimator (3) is arranged between the X-ray tube (1) and the measuring pool (2), a first diffraction crystal (4) is arranged below the measuring pool (2), a second diffraction crystal (5) is arranged obliquely above the first diffraction crystal (4), a second collimator (6) is arranged between the second diffraction crystal (5) and the detector (7), and a signal output end of the detector (7) is connected to a computer system (8) for power control of the X-ray tube (1) and analysis and calculation of measurement results.

2. A secondary pre-diffraction high-precision X-ray fluorescence analysis system according to claim 1, characterized in that: It also includes a power supply (9) for supplying power to the X-ray tube (1) and the computer system (8).

3. A secondary pre-diffraction high-precision X-ray fluorescence analysis system according to claim 1, characterized in that: The tube voltage of the X-ray tube (1) ranges from 50 kV to 100 kV, the tube current ranges from 1 mA to 5 mA, and the focal spot size ranges from 0.1 mm to 2 mm.

4. A secondary pre-diffraction high-precision X-ray fluorescence analysis system according to claim 1, characterized in that: The incident angle of the X-rays emitted by the X-ray tube (1) relative to the plane of the material liquid to be measured in the measuring pool (2) is 60°.

5. A secondary pre-diffraction high-precision X-ray fluorescence analysis system according to claim 1, characterized in that: The first collimator (3) is made of copper, and the diameter of the collimation hole of the first collimator (3) is 4 mm to 10 mm.

6. A secondary pre-diffraction high-precision X-ray fluorescence analysis system according to claim 1, characterized in that: A measuring window for X-ray transmission is arranged at the bottom of the measuring pool (2); the measuring window is made of boron carbide or carbon fiber; and the thickness of the measuring window is 2 mm.

7. A secondary pre-diffraction high-precision X-ray fluorescence analysis system according to claim 1, characterized in that: The first diffraction crystal (4) and the second diffraction crystal (5) are both made of lithium fluoride crystal, germanium crystal or graphite crystal.

8. A secondary pre-diffraction high-precision X-ray fluorescence analysis system according to claim 1, characterized in that: The second collimator (6) is made of polytetrafluoroethylene, nylon or organic glass.

9. A secondary pre-diffraction high-precision X-ray fluorescence analysis system according to claim 1, characterized in that: The detector (7) adopts a FAST SDD detector.

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