Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B15/00—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons
  • G01B15/02—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons for measuring thickness
  • G01B15/025—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons for measuring thickness by measuring absorption
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
  • A61B6/48—Diagnostic techniques
  • A61B6/484—Diagnostic techniques involving phase contrast X-ray imaging
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C17/00—Monitoring; Testing ; Maintaining
  • G21C17/06—Devices or arrangements for monitoring or testing fuel or fuel elements outside the reactor core, e.g. for burn-up, for contamination
• • 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
  • G01N2223/615—Specific applications or type of materials composite materials, multilayer laminates
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
  • G21K2207/00—Particular details of imaging devices or methods using ionizing electromagnetic radiation such as X-rays or gamma rays
  • G21K2207/005—Methods and devices obtaining contrast from non-absorbing interaction of the radiation with matter, e.g. phase contrast
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E30/00—Energy generation of nuclear origin
  • Y02E30/30—Nuclear fission reactors

Definitions

• Non-destructive characterization method in particular for nuclear fuel particles for a high-temperature reactor
• the invention generally relates to non-destructive characterization methods, particularly for nuclear fuel particles for high temperature reactor.
• the invention relates to a method for characterizing an element comprising a plurality of superposed layers separated from one another by interfaces.
• the nuclear fuel particles for a high temperature nuclear reactor are substantially spherical and comprise a fissile core coated with layers of dense and porous pyrocarbon, and ceramic such as silicon carbide or zirconium carbide.
• the determination of the density of each layer composing the fuel particle is an essential parameter for the qualification of this fuel.
• the most commonly used method for this purpose is a flotation method.
• Several control particles are sampled in a batch of particles to be characterized. This particle is cut out, and pieces of each layer are separated for density measurements. These pieces are placed in turn in a liquid whose density varies greatly depending on the temperature. The temperature of the liquid is then varied, and the temperature at which the pieces float at the bottom of the liquid is noted. The density of the material constituting the piece corresponds to the density of the liquid at said temperature.
• This method has the defect of using toxic liquids. Moreover, this method of characterization is slow, and leads to the destruction of the characterized fuel particles. Finally, its implementation is extremely cumbersome since the pieces of each layer must be separated and identified one by one.
• the invention aims to propose a characterization method applicable to nuclear fuel particles for a high-temperature reactor, non-destructive, environmentally friendly, and faster to implement.
• the invention relates to a method of characterization of the aforementioned type, characterized in that it comprises at least the following steps: - illuminate the element with radiation emitted by a source;
• the determining step being ensured by minimizing the difference between the experimental image and a simulated image of at least part of the experimental image.
• the process may also have one or more of the following characteristics, considered individually or in any technically possible combination:
• the radiation is emitted by an X-ray source;
• the detector is a direct or indirect detection charge transfer camera;
• the physical characteristic to be determined is the density
• the physical characteristic to be determined is the thickness
• the method comprises a preliminary step of determining the impulse response of the detector, carried out in:
• control element is placed against the detector, the simulated image being made for at least one edge of the control element.
• the invention relates to the use of the above method for characterizing a substantially spherical particle comprising a plurality of substantially spherical layers, substantially concentric and superimposed.
• the use of the method may have one or more of the following characteristics:
• the experimental image is substantially circular, the simulated image being a line passing through a diameter of the experimental image; and the particle is a nuclear fuel particle.
• FIG. 1 is a schematic equatorial section illustrating an exemplary structure of a nuclear fuel particle for a high temperature reactor
• FIG. 2 is a schematic view illustrating an installation for implementing a characterization method according to the invention
• FIG. 3 illustrates the experimental image collected during the implementation of the method of the invention with a member consisting of a carbon fiber comprising a silicon carbide core;
• FIG. 4 is a graphical representation of the gray levels along a horizontal line L in FIG. 3;
• FIG. 5 is a schematic block representation of the step for calculating the thicknesses and densities of the various layers of the particle of FIG. 1, from the experimental image of this particle obtained with the installation of FIG. Figure 2.
• FIG. 1 schematically illustrates a particle 1 of nuclear fuel for a reactor at high or very high temperature (HTR ⁇ / HTR).
• this particle 1 is of generally spherical shape and comprises successively from inside to outside:
• nucleus of fissile material 3 for example based on UO 2 (it may be other types of fissile material such as UCO, ie a mixture of U 02 ⁇ t of UC2),
• the core 3 has a diameter of about 500 ⁇ m, the diameter may vary from 100 ⁇ m to 1000 ⁇ m, and the layers 5, 7, 9 and 11 have respective thicknesses of, for example, 95, 40, 35. and 40 ⁇ m.
• the layers, in particular layers of pyrocarbon 5, 7, 11, are deposited for example by a chemical vapor deposition process (Chemical Vapor Deposition) carried out in a fluidized bed furnace.
• the installation illustrated in FIG. 2 makes it possible to measure the density and the thickness of at least layers 5, 7, 9 and 11.
• the installation comprises:
• an X-ray source 13 capable of producing X-ray radiation forming a beam extending in a general direction represented by the arrow F of FIG. 2;
• a detector 17 sensitive to X-radiation and placed so as to intercept the radiation produced by the source 13;
• a unit 19 for processing information a unit 19 for processing information.
• the source 13 is preferably a point source emitting monochromatic radiation.
• the source 13 is for example a micro-focal or rotating anode X-ray tube, or a synchrotron associated or not with an optical instrument, for example a multilayer mirror or a hollow fiber network.
• a particle 21 to be characterized, of the type described above, is placed at a distance d1 from the source 13, so as to be illuminated by the radiation 15.
• a fraction 23 of the radiation 15 is transmitted through the particle 21 and strikes the detector 17.
• This fraction will be called radiation transmitted in the description which follows.
• the source 19, the particle 21 and the detector 17 are substantially aligned.
• the detector 17 is for example a charge transfer camera, known as a CCD camera, with direct detection, or with indirect detection, that is to say, preceded by a scintillator allowing the camera to be sensitive.
• the X-radiation delivered by the source 13. It is placed at a distance d2 from the particle 21 to be characterized.
• the transmitted radiation 23 forms on the detector 17 an experimental image of the particle 21.
• the detector may also be a non-digital detector such as a photostimulable screen, the experimental image being obtained via an additional scanning device.
• the experimental image collected on the detector 17 is typically a two-dimensional image, the different points constituting the experimental image being acquired simultaneously.
• the radiation 15 has, between the source 13 and the particle 21, substantially spherical wave fronts. These fronts are all the less spherical as the distance d1 is large.
• the X-rays constituting the transmitted radiation cut the particle 21 along directions in which this particle has different thicknesses and passes through different materials. They will undergo, as a result, variable phase shifts, depending on the wavelength, density, nature and thickness of the material traversed.
• the transmitted radiation 23 has a wavefront modified by the object.
• the distance d2 between the detector and the particle 21 is chosen so that interference fringes appear on the experimental image of the particle 21 collected on the detector 17. These interference fringes appear on the experimental image at less at the interfaces between the layers 5, 7, 9 and 11 of the particle, due to the variable phase shift experienced by the X-rays passing through the particle 21.
• the experimental image is an image collected by the known technique without the name of phase contrast radiography. It corresponds to the superposition of interference fringes on an image obtained by absorption of incident X-rays through the element to be characterized. Said image obtained by absorption is essentially formed by the radiation transmitted directly through the element to be characterized. The fraction of the incident radiation that is scattered or reflected only reaches the detector in a small proportion.
• the experimental image collected by the detector 17 is supplied to the information processing unit 19.
• the latter comprises, for example, a microcomputer provided, inter alia, display means in the form of a screen 25.
• the unit 19 is also connected to means 27 making it possible to support the particle 21 and to move it parallel to the radiation 15
• the unit 19 is, in addition, connected to means 29 making it possible to move the detector 17 also parallel to the radiation 15.
• FIG. 3 illustrates an example of an experimental image that can be collected by the detector 17.
• FIG. 3 represents the experimental image of a carbon fiber comprising a silicon carbide core. collected in the conditions illustrated in Figure 2.
• the computer means 19 extract a profile of the experimental image, taken here along the line L materialized in Figure 3.
• the fiber 31 in the image of Figure 3 is extended in a manner. vertical direction.
• the profile L is taken along a horizontal line in FIG.
• FIG. 4 represents the profile along the line L, expressed in gray scale in the image of FIG. 3 for each pixel of the detector placed along the line L.
• the profile exhibits variations of gray levels inherent to the presence of the fiber, the wavelength, the nature, the density and the thickness of the fiber.
• the processing unit 19 then calculates a simulated profile of the line L. As shown in FIG. 5, the unit 19 uses, for this purpose, input values for various parameters. These parameters are:
• the unit 19 compares the simulated profile with the experimental profile, and adjusts the densities and the thicknesses of the layers 5, 7, 9 and 11 iteratively, in order to to minimize the difference between experimental and simulated profiles.
• the iterative process is stopped when the difference stabilizes at a value close to zero, that is, when the iterative process has reached a point of convergence.
• the unit 19 provides as a result of the analysis the values of the densities and thicknesses of the layers 5, 7, 9 and 11 corresponding to the simulated profile towards which the iterative process has converged.
• the profile simulated by the unit 19 is calculated pixel by pixel along the line L.
• a coordinate system denoted x, y, z, where z is the coordinate along an axis parallel to the direction.
• F X ray beam propagation, x and y being the coordinates in a plane parallel to the photosensitive area of the CCD camera, said plane being perpendicular to the direction F.
• Unit 19 uses, for this purpose, the following general equation:
• P d (x. Y) is a term characterizing the propagation of radiation between the particle and the detector, that is, the wavefront evolution along the path from the particle to the detector. It is expressed by the following equation (2):
• the second term of the equation (1) characterizes the attenuation of an X-ray passing through the particle 21. This expression is integrated along the entire path that the radiation travels inside the particle 21. In this expression, ⁇ represents the linear attenuation coefficient of the material traversed by the radiation.
• ⁇ is the real part of the refractive index of the material crossed by the X-ray
• r c is the classical electron radius
• N is es t Avogadro's number
• p is the density of the material traversed by the radiation .
• q j is the mass fraction of this element in the material
• Z j is the atomic number of the element
• f ' j is the real part of the dispersion correction of the atomic scattering factor
• AJ is the atomic mass of the element.
• equation (3) the integral is along the entire length of the X-ray path through particle 21.
• PSF is the impulse response of the detector for the corresponding pixel.
• stars symbolize convolution products.
• the unit 19 first calculates, for each pixel along the profile, the imaginary and real parts of the propagation term, the attenuation term and the phase shift term. It then calculates the Fourier transforms of these three terms, and calculates, for each pixel, the product of the Fourier transforms of these three terms. It then determines the inverse Fourier transform of the product obtained. Then it calculates the modulus squared of the amplitude of the result of the inverse Fourier transform. This gives the energy of the simulated X-ray in front of each pixel of the detector. tor. Finally, the simulated profile is determined by convolving the energy obtained previously for each pixel by the PSF.
• the determination of the thickness and density values of the layers making it possible to minimize the difference between the simulated profile and the experimental profile can be achieved by using various algorithms known per se. For example, it is possible to use the so-called method of gradient descent. It is also possible to use other methods, such as stochastic methods or simulated annealing or genetic algorithms. Among these methods, one can use the so-called stochastic gradient algorithm, local random search or increased local random search.
• the sensor impulse response is determined according to the method which will be described below. This is done before determining the densities and thicknesses of the layers of the particle. It must be repeated each time one of the parameters of the measuring installation is modified, namely the distance d1 between the source 13 and the particle 21, the distance d2 between the particle 21 and the detector 17, the characteristics of the source, and the characteristics of the detector. On the other hand, it is not necessary to redetermine the PSF for each characterized particle, provided that the operating parameters of the installation are not modified.
• the impulse response of the detector is determined for example by:
• the control element is placed against the detector 17, and not remotely like the particle 21.
• This control element is typically a silicon wafer cleaved. It is placed in such a way that the line L intersects an outer edge of the plate.
• the impulse response of the detector along line L can be expressed as follows:
• PSF (x) 2 exp PsSfF - c ⁇ .
• t parameters whose values are determined by minimizing the difference between the simulated profile and the experimental profile of the control element. This determination is carried out, as mentioned above, using conventional iterative algorithms such as gradient descent, or stochastic algorithms such as stochastic gradient, local random search or increased local random search.
• the second image is made after rotating the particle 21 about 90 ° about a vertical axis on Figure 2, that is to say both perpendicular to the direction F and perpendicular to the line L.
• the unit 19 determines, from the second image, the thickness of material traversed by the X-rays in the first position of the particle 21.
• the determination of the densities of the layers is carried out using the first experimental image, taking into account the material thickness values determined from the second image. This is particularly useful for particles to be characterized which are not perfectly spherical.
• the method makes it possible to determine the thicknesses and the densities of the layers surrounding the nucleus of fissile material of the particle in a very precise manner. In particular, as shown in the table below, it makes it possible to determine the densities of the layers with an accuracy of less than 6%.
• the experimental image of the particle collected by the detector is used to determine the presence of structural anomalies within the layers 5, 7, 9 and 11 of the particle , or between the layers of the particle.
• the structural anomalies that can thus be detected are, among others, the following:
• the method can be used to determine the thicknesses and densities of all layers surrounding the fissile material core of the particle.
• the process is accurate, and allows to determine thicknesses and densities with an accuracy of less than 6%.
• the step of determining the sensor impulse response described above contributes significantly to the accuracy of the process.
• the process described above can have multiple variants. It can be applied to any type of elements with overlapping layers. These elements can have all kinds of shapes, different from the spherical shape mentioned above. These shapes can be regular or irregular.
• the layers can be made of all kinds of different materials, the process not being limited to the materials mentioned above.
• the method can in particular be used to characterize the fuel particles of all types of high temperature reactor, for example of the type known by the acronyms HTR (High Temperature Reactor), HTTR (High Temperature Engineering Test Reactor), VHTR (Very High Temperature Reactor), HTGR (High Temperature Gas-cooled Reactor), THTR (Thorium High Temperature Reactor), GT-MHR (Gas Turbine Modular Helium Reactor), MHTGR (Modular High Temperature Gas Reactor) and PBMR (Pebble Bed Modular Reactor) .
• HTR High Temperature Reactor
• HTTR High Temperature Engineering Test Reactor
• VHTR Very High Temperature Reactor
• HTGR High Temperature Gas-cooled Reactor
• THTR Thorium High Temperature Reactor
• GT-MHR Gas Turbine Modular Helium Reactor
• MHTGR Modular High Temperature Gas Reactor
• PBMR Packebble Bed Modular Reactor
• the physical characteristics of the layers are determined by minimizing the difference between a portion of the image, in this case a profile taken along a line, and a simulated profile. More generally, it is possible to extract from the experimental image and perform the deviation minimization operation not on a profile taken along a line but on all your kinds of areas of the experimental image. Thus, it is possible to extract several parallel lines between them or not parallel to each other. It is also possible to extract one or more two-dimensional areas of the screen. It is also possible to minimize the deviation by considering the entire experimental image. Of course, the larger the number of pixels considered in the selected area, the greater the accuracy of the result, but the longer the calculation time is.
• the impulse response of the detector used to calculate the simulated image can be determined in different ways. It can be determined as described above, minimizing the gap between the simulated and experimental images of a plate placed against the detector. It can also be determined similarly using a plate placed at a distance d2 from the detector. It is also possible to use a predetermined value, which is not reevaluated when the operational parameters of the characterization device are modified. It is also possible to determine the PSF for each particle characterized, from the experimental image of this particle. This operation is performed before the determination of the densities and thicknesses of the different layers of the particle to be characterized.

Landscapes

• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Medical Informatics (AREA)
• High Energy & Nuclear Physics (AREA)
• Heart & Thoracic Surgery (AREA)
• Animal Behavior & Ethology (AREA)
• Optics & Photonics (AREA)
• Pathology (AREA)
• Radiology & Medical Imaging (AREA)
• Biomedical Technology (AREA)
• Biophysics (AREA)
• Molecular Biology (AREA)
• Surgery (AREA)
• Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Plasma & Fusion (AREA)
• General Engineering & Computer Science (AREA)
• Electromagnetism (AREA)
• General Physics & Mathematics (AREA)
• Analysing Materials By The Use Of Radiation (AREA)
• Monitoring And Testing Of Nuclear Reactors (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=37625720

Family Applications (1)

Country Status (7)

Families Citing this family (11)

Family Cites Families (16)

• 2006
  • 2006-07-28 FR FR0606950A patent/FR2904421B1/fr not_active Expired - Fee Related
• 2007
  • 2007-07-18 EP EP07823300A patent/EP2047240A2/fr not_active Withdrawn
  • 2007-07-18 WO PCT/FR2007/001236 patent/WO2008012417A2/fr active Application Filing
  • 2007-07-18 JP JP2009522295A patent/JP5477900B2/ja not_active Expired - Fee Related
  • 2007-07-18 US US12/375,327 patent/US8160201B2/en not_active Expired - Fee Related
  • 2007-07-18 CN CN2007800348465A patent/CN101517401B/zh not_active Expired - Fee Related
• 2009
  • 2009-01-26 ZA ZA2009/00597A patent/ZA200900597B/en unknown

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events