JP2009175065A - Simultaneous three-dimensional distribution-visualization observation-measurement method of a plurality of elements by neutron prompt gamma-ray analysis, and device thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simultaneously and three-dimensionally observe and measure the element distribution of a plurality of elements in a target material, by combining the CT technique and neutron prompt gamma-ray analysis. <P>SOLUTION: In this measuring technology, an object is scanned by utilizing a neutron beam of high parallelism, cut into beam shape responsive to a required spatial resolution; a prompt gamma ray spectrum responsive to each scanning is measured or recorded, and the recorded prompt gamma-ray spectrum for each scanning position is processed by a computer, thereby measuring the three-dimensional element distribution inside the object. By performing computer processing for each gamma-ray peak from a plurality of isotopes in the prompt gamma-ray spectrum for each recorded scanning position, the three-dimensional element distribution of many elements inside the object is measured simultaneously. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a measurement technique for simultaneously observing and measuring a plurality of elements by three-dimensional element distribution by neutron prompt gamma ray analysis and an apparatus therefor.

  As soon as the measurement sample is irradiated with a neutron beam, prompt gamma rays are emitted from the target substance. Prompt gamma ray analysis is an analysis method that measures prompt gamma rays, identifies isotopes or elements from gamma ray energy, and quantifies the amount of elements from gamma ray intensity. Both neutrons and prompt gamma rays are highly permeable to matter, enabling accurate nondestructive and multielement simultaneous analysis of the entire solid sample.

  As a three-dimensional non-destructive visualization method, a CT technique is used which visualizes the inside of an object by transmitting X-rays or neutrons while rotating the object and processing a transmission image obtained at each rotation angle by a computer. In addition, the density distribution of the constituent materials inside the object is observed.

Furthermore, a three-dimensional mapping method that enables measurement including orientation information of crystal particles or magnetic domains in a substance in addition to the density distribution of constituent substances inside the object has been proposed (Patent Document 1).
In addition, the present inventors conducted neutron prompt gamma ray analysis (PGA), and conducted prompt non-destructive multi-element analysis by measuring prompt gamma rays emitted when a sample was irradiated with neutrons. Then, it was examined that it is effective for analysis of many elements including light elements such as H, B, and Si, which are difficult to analyze (research on neutron prompt gamma ray analysis based on the k ₀ method).
Japanese Patent Application No. 2004-255146 (Japanese Patent Laid-Open No. 2006-71449) “Structural Mapping Method Using Neutron Scattering”

  However, according to the above technique, it is difficult to simultaneously observe and measure a three-dimensional element distribution of a plurality of elements in a target substance.

  It is an object of the present invention to simultaneously observe and measure a three-dimensional element distribution of a plurality of elements in an object target material by combining CT technique (computer tomography technique) and neutron prompt gamma ray analysis.

  In order to solve the above problems, the first invention scans an object using a highly parallel neutron beam cut into a beam shape corresponding to the required spatial resolution, and prompt gamma ray spectra corresponding to each scan. Is a measurement technique characterized by measuring the element distribution in three dimensions inside the object by computer processing the prompt gamma ray spectrum for each scan position recorded.

  The second invention is characterized in that the three-dimensional element distribution in the object is simultaneously measured by performing computer processing for each gamma ray peak from a plurality of isotopes in the prompt gamma ray spectrum for each recorded scanning position. Measurement technology.

  According to the third aspect of the present invention, a monitor element is placed before and after the sample on the neutron beam line in order to correct attenuation due to self-absorption and scattering when the neutron beam passes through the object, and the gamma ray intensity is measured. This is a correction method for correcting neutron self-absorption.

  According to the first invention, an object is scanned using a highly parallel neutron beam cut into a beam shape corresponding to a required spatial resolution, and an prompt gamma ray spectrum corresponding to each scan is measured and recorded. It is possible to measure the three-dimensional distribution of the specific element inside the object by computer processing the prompt gamma ray spectrum for each scanning position. Moreover, since almost all elements generate neutron prompt gamma rays, the target is all elements. Also, trace distribution analysis is possible for hydrogen, boron, cadmium, mercury, samarium, gadolinium, etc., which can be analyzed with high sensitivity by neutron prompt gamma ray analysis.

  According to the second invention, if a computer process is performed for each of a plurality of gamma ray peaks in the prompt gamma ray spectrum recorded at each scanning position, a three-dimensional element distribution inside the object can be obtained simultaneously with multiple elements.

  According to the third invention, attenuation due to self-absorption and scattering when a neutron beam passes through an object is a large uncertainty factor in computed tomography. In order to correct these uncertain factors, a monitor element that is not subject to analysis is placed before and after the sample on the neutron beam, and the gamma ray intensity is measured simultaneously to correct the neutron self-absorption by the sample. Thereby, it is possible to measure the three-dimensional distribution of the specific element inside the object in which the uncertain element is corrected.

  FIG. 1 shows an outline of an apparatus for simultaneous three-dimensional distribution, visualization observation and measurement of a plurality of elements by neutron prompt gamma ray analysis according to the present invention. A neutron beam from a neutron source such as a nuclear reactor is cut out by a neutron collimator 1 and collimated to a high parallelism and a spatial resolution required for measurement, and irradiated to a measurement sample (triangular pyramid composed of cadmium wires) 2 To do. The measurement sample is placed on a 2D (two-dimensional) + rotation stage 3 that can be driven and rotated in the XY direction perpendicular to the neutron beam. The measurement sample 2 is irradiated with a collimated neutron beam, detected at each (X, Y, rotation angle φ) coordinate through a neutron shield 5 and a gamma ray collimator 6 by a gamma ray detector 7, and prompt gamma ray spectrum by a gamma ray spectrometer 8. 9 is measured and recorded.

  As shown in FIG. 1, by specifying ROI (Region of Interest) for prompt gamma rays specified for each element in the prompt gamma ray spectrum 9, count information of specific gamma ray peaks for each element can be obtained. . The ROI can be specified before measurement if the target element is clear in advance. If unknown, it is possible even after measurement.

  By performing computer tomography processing from gamma ray peak information for each element obtained for each (X, Y, rotation angle φ) coordinate, a three-dimensional element distribution inside the object can be obtained at the same time.

Hereinafter, embodiments will be described with reference to the drawings, and a method and apparatus for simultaneous three-dimensional distribution / visualization observation / measurement of a plurality of elements by neutron prompt gamma ray analysis will be described in more detail. A 2D + rotating stage 3 as shown in Fig. 1 was installed in the prompt gamma ray analyzer of the Japan Atomic Energy Agency JRR-3 research reactor, and it was created with a 0.25mmφ cadmium wire with a side of 1cm on each stage. Triangular pyramid sample 2 was installed. This triangular pyramid sample is one in which three 1 cm long wire wires are joined at the apex in a triangular pyramid shape.
The neutron beam was collimated to 1 × 1 mm ² by the neutron collimator 1 and irradiated to the triangular pyramid sample 2. A Ge semiconductor attached to the JRR-3 prompt gamma ray analyzer while driving the sample in 1 mm, 1.5 mm, and 10 degree increments in the X, Y, and φ (lateral X, height Y, and rotation) directions by the stage, respectively. Prompt gamma-ray spectra were measured with a detector. ROI was set to 558 keV prompt gamma ray of cadmium in the prompt gamma ray spectrum, and the gamma ray count in the ROI region was recorded for each measurement position. The measurement data and measurement coordinate data were subjected to computer tomography processing by measurement analysis software (NIPPON) developed by the Japan Atomic Energy Agency, and the three-dimensional element mapping of the cadmium element shown in FIG. 2 was obtained. Although the three-dimensional element mapping image can be imaged from any designation, FIG. 2 shows a CT image 10 viewed from directly above and a CT image 11 viewed from the side. The image of the photographic diagram in the images 10 and 11 is the gamma ray intensity of the ROI of the gamma ray peak derived from the designated element, and correlates with the abundance of the designated element. The gamma ray intensity is indicated based on the color density of the map in the figure.
That is, the color densities of 10 and 11 in FIG. 2 represent the gamma ray intensity, that is, a numerical value representing the abundance of the cadmium element, expressed by the color intensity. The portion of the measurement sample that shows the brightness that appears near the end of the wire line is one in which the cadmium lines overlap and the intensity of the gamma rays increases, so that the density of the displayed color changes accordingly. Each number shown on the left represents the intensity of gamma rays in terms of color intensity.

It is the figure which showed the outline | summary of the simultaneous three-dimensional distribution, visualization observation, measurement method of multiple elements by the neutron prompt gamma-ray analysis of this invention, and its apparatus. It is the three-dimensional element mapping image of the cadmium element obtained by the method of the present invention.

Explanation of symbols

1: neutron collimator, 2: measurement sample or triangular pyramid sample, 3: 2D + rotation stage, 4: prompt gamma ray, 5: neutron shield, 6: gamma ray collimator, 7: gamma ray detector, 8: gamma ray spectrometer, 9: Gamma ray spectrum, 10: CT analysis result (viewed from directly above), 11: CT analysis result (viewed from the side)

Claims (5)

  By applying a neutron beam to a target material that has been rotated and driven vertically and horizontally, a neutron beam is emitted from the neutron beam that passes through the target material, and different neutron capture prompt gamma rays (hereinafter referred to as prompt gamma rays) The energy spectrum and the irradiation position information of the neutron beam on the target substance are recorded, and the three-dimensional space for each isotope or element in the target substance using the computer tomography technique (CT technique) from the recorded information. A method of observing and measuring information.   The peak information in the energy spectrum of a plurality of prompt gamma rays different for each isotope or element is analyzed using the recorded information obtained by the method according to claim 1, and the plurality of isotopes or elements in the target substance are analyzed. A method for observing and measuring three-dimensional spatial information for each isotope or element.   In order to improve the measurement accuracy of the method according to claim 1 or 2, an indicator element for measuring the incident neutrons forward in the field of view of the prompt gamma ray detector of the target substance on the irradiation beam of the neutron beam, A correction method for correcting a phenomenon of self-absorption in a target substance by installing an indicator element for measuring transmitted neutrons and measuring the intensity of prompt gamma rays from these elements simultaneously with the target substance.   In order to improve the measurement accuracy of the method according to claim 1 or 2, a neutron detector for measuring incident neutrons in front of the prompt gamma-ray detector of the target substance on the irradiation beam of the neutron beam, A correction method that corrects the phenomenon of self-absorption by installing a neutron detector for measuring transmitted neutrons behind and recording the neutron intensity from these simultaneously with the prompt gamma ray measurement of the substance.   A tomography mechanism for fixing, rotating, vertically and horizontally driving the target material on the irradiation beam of the target material and the neutron beam derived from the reactor or accelerator neutron source, gamma ray detector, correction indicator element, and correction neutron An apparatus for simultaneously visualizing, observing and measuring three-dimensional spatial information of a plurality of isotopes or elements in the target substance, which is constituted by a detector.

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