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EP3707500A1 - Procédé et dispositif d'analyse multiélémentaire sur la de base de l'activation neutronique et utilisation - Google Patents

Procédé et dispositif d'analyse multiélémentaire sur la de base de l'activation neutronique et utilisation

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Publication number
EP3707500A1
EP3707500A1 EP18729863.3A EP18729863A EP3707500A1 EP 3707500 A1 EP3707500 A1 EP 3707500A1 EP 18729863 A EP18729863 A EP 18729863A EP 3707500 A1 EP3707500 A1 EP 3707500A1
Authority
EP
European Patent Office
Prior art keywords
sample
neutron
energy
gamma radiation
irradiation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP18729863.3A
Other languages
German (de)
English (en)
Inventor
Kai KRYCKI
John Kettler
Andreas HAVENITH
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Aachen Institute for Nuclear Training GmbH
Original Assignee
Aachen Institute for Nuclear Training GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from EP17401060.3A external-priority patent/EP3410104B1/fr
Priority claimed from DE102017111935.3A external-priority patent/DE102017111935B4/de
Application filed by Aachen Institute for Nuclear Training GmbH filed Critical Aachen Institute for Nuclear Training GmbH
Publication of EP3707500A1 publication Critical patent/EP3707500A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • G01N23/22—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 measuring secondary emission from the material
    • G01N23/223—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 measuring secondary emission from the material by irradiating the sample with X-rays or gamma-rays and by measuring X-ray fluorescence
    • 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
    • G01N23/22—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 measuring secondary emission from the material
    • G01N23/221—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 measuring secondary emission from the material by activation analysis
    • G01N23/222—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 measuring secondary emission from the material by activation analysis using neutron activation analysis [NAA]
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T3/00—Measuring neutron radiation
    • G01T3/001—Spectrometry
    • 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
    • G01N2223/07—Investigating materials by wave or particle radiation secondary emission
    • G01N2223/074—Investigating materials by wave or particle radiation secondary emission activation analysis
    • G01N2223/0745—Investigating materials by wave or particle radiation secondary emission activation analysis neutron-gamma activation analysis

Definitions

  • the present invention relates to a method for multi-element analysis based on neutron activation by irradiating a sample with neutrons. Furthermore, the present invention relates to a corresponding
  • the present invention also relates to the use of a controller or a computer program product therefor.
  • the invention relates to a method and a device according to the preamble of the respective independent or
  • the analysis of substances or materials, in particular with regard to their element composition is of great importance, in particular with regard to hazardous goods or wastes or recycling materials or raw materials or the quality control of semi-finished products or industrial products.
  • One of the analysis methods carried out so far is the so-called multi-element analysis, by means of which individual elements of a sample are determined, without first having to know the exact composition of the sample.
  • the multi-element analysis can by means of neutron activation or for example by means of
  • Gamma radiation is evaluated after a certain time window depending on the manner of the pulsed irradiation.
  • the time window for the detection of the gamma radiation is started after a waiting time, which follows at the end of each neutron pulse, and ends before the next neutron pulse is emitted.
  • WO 2012/010162 A1 and DE 10 2010 031 844 A1 describe a method for the non-destructive elemental analysis of large-volume samples with neutron radiation and a device for carrying out the method.
  • the sample is pulsed with fast neutrons, wherein the gamma radiation emitted by the sample is measured after a certain time window after a neutron pulse before a new neutron pulse is emitted to the sample.
  • the measuring method is also based on the knowledge that the measurement can be made possible by a moderation process and by observing a time window after a respective neutron pulse.
  • Gamma radiation resulting from inelastic interactions, can be filtered out due to the time window after a respective neutron pulse and thus be hidden during the measurement. As gamma radiation, prompt gamma radiation is evaluated.
  • EP 1 882 929 B1 and WO 01/07888 A2 describe methods in which neutrons are pulsed onto the sample and after each pulse a time window is maintained until the prompt emitted by the sample Gamma radiation is measured. Comparable methods are also described, for example, in EP 0 493 545 B 1 and in DE 10 2007 029 778 B4.
  • Neutron activation analysis is also described in the following further publications: US 2015/0338356 AI, DE 603 10 118 T2, US 2005/0004763 A1, US 2012/046867 A1, DE 102 15 070 A1, DE 12 36 831 B.
  • the object is to provide a method and a device with which the multi-element analysis of samples can be facilitated by means of neutron activation. Also an object is to provide a method and an apparatus for
  • Multielement analysis by neutron activation in such a way that results in a wide range of applications.
  • the object can also be seen in providing a user-friendly, uncomplicated, fast measuring method which can be applied as independently as possible from the type or size or material composition of the sample to be analyzed.
  • a method of multi-element analysis based on neutron activation is performed with the following steps: generating fast neutrons with energy in the range of 10KeV to 20MeV; Irradiating a sample with the neutrons; Measuring the gamma radiation emitted from the irradiated sample to determine at least one element of the sample.
  • the irradiation of the sample takes place in an unpulsed, continuous manner, the measurement taking place irrespective of the irradiation time (irrespective of the time course of the irradiation), in particular without time intervals given by neutron pulses, during the irradiation, in particular simultaneously for the irradiation over the same period of time as the
  • a non-destructive multi-element analysis based on neutron activation can be provided for diverse types of samples and with high metrological flexibility and robust, reproducible, reliable results.
  • the sample is continuously irradiated with neutrons without individual pulses, for example continuously over a period of several seconds or minutes or hours, whereby the gamma radiation emitted / emitted by the sample can be measured simultaneously with the irradiation.
  • the neutrons can be generated in particular by means of a generator for the fusion of deuterons (deuterium nuclei), in particular with deuterium gas as gaseous target or as fuel.
  • the present invention enables measurement and evaluation based on comparatively low-energy irradiation over a long period of time, whereby the analysis can be carried out very accurately and reproducibly.
  • many metrological tasks have so far been irradiated in a pulsed manner, so far a waiting time after a respective neutron pulse has been required.
  • the pulse length used to be usually in the range of ten to several hundred micro seconds ⁇ sec.).
  • both the prompt and the emitted gamma radiation emitted by the sample are measured simultaneously with the irradiation, the energy resolution of the detector allowing the division into prompt and delayed gamma radiation.
  • Coordination with the end of a respective neutron pulse is no longer required, but it can be continuously irradiated and measured. This also makes it possible to reduce the measuring time for the analysis of the samples.
  • the measurement can be done completely without time window, or optionally partially with time window. At least part of the emitted gamma radiation is preferably at least time-independent measured without time window.
  • the method may include moderating the fast neutrons, at least temporarily.
  • the simultaneous measurement of the gamma radiation allows a high performance of the measuring system.
  • both prompt and delayed gamma radiation can be measured, with a focus on prompt gamma radiation.
  • the measurement simultaneously with the irradiation can take place in a continuous manner, in particular with the same timing as the irradiation, or in individual time windows irrespective of time specifications for the irradiation. For example, a continuous irradiation, but optionally a measurement takes place only at small intervals.
  • Measuring at the same time as continuous irradiation means that no time windows have to be taken into account, but that the measurement and evaluation can be carried out in a very flexible manner and both types of radiation, ie prompt and delayed gamma radiation, can be evaluated.
  • the measurement / detection of the gamma radiation can be emphasized independently of temporal relationships in the neutron irradiation.
  • the neutrons have been granted a certain time window for many metrological tasks in order to be able to carry out the measurement, in particular after the neutrons have been emitted.
  • this time window is at least 5 ⁇ 8 ⁇ ⁇
  • the probability for interactions in the sample increases, so that after a certain waiting time (or moderation time) after a respective neutron pulse with a sufficiently good signal to background ratio SNR could be measured.
  • the data acquisition took place in a time-shifted manner as a function of the neutron pulses.
  • the gamma radiation measured and evaluated according to the present method is, on the one hand, prompt gamma radiation which is emitted immediately after an interaction of the neutrons with the atomic nuclei of the sample.
  • the time to emission is about 10exp-16 to 10exp-12 seconds in the case of prompt gamma radiation, which period is so short that immediate / immediate emission can be used.
  • prompt gamma radiation there is no metrologically relevant time delay between neutron capture and emission of the gamma radiation.
  • delayed gamma radiation is also affected, which is emitted at the disintegration of the activated atomic nuclei with a time delay according to the characteristic half-life.
  • Delayed gamma radiation is emitted out of the atomic nucleus after a neutron capture according to the characteristic half-life of the formed radionuclide.
  • NAA classical neutron activation analysis
  • Half-life of the activated radionuclide influences the emitted radiation.
  • two measurement concepts can be interconnected: classical neutron activation analysis (NAA) on the one hand, and a prompt gamma NAA on the other hand (PGNAA).
  • NAA classical neutron activation analysis
  • PGNAA prompt gamma NAA
  • a distinction can be made between prompt and delayed gamma radiation based on the energy of the gamma radiation (in particular the position of the maximum of a peak) and the energy resolution of the detector.
  • the irradiation may optionally also be in a pulsed manner, at least temporarily, to measure only delayed gamma radiation.
  • only delayed gamma radiation may be measured, especially in an analysis for lead. The gamma radiation emitted from the sample is measured in an energy-resolved manner in one or more detectors.
  • a measured gamma spectrum in particular according to a record of the number of events detected in a gamma ray detector as a function of energy.
  • the energy of the gamma radiation is used to identify the elements of the sample.
  • the quantification of an element mass takes place.
  • the mass fraction of an element contained in the sample, after subtracting the background signal, is evaluated from the area of the photopeaks which the element produces in the gamma spectrum.
  • the analytical evaluation for mass determination in the multi-element analysis is based in particular on the calculation of energy-dependent photopeak efficiencies of gamma emissions from the sample and from individual partitions of the sample and the calculation of the neutron spectrum and the neutron flux within the sample and within partitions of the sample. For these calculations, initial assumptions about the elemental composition can be made, which are derived from the evaluation of the gamma spectrum. It has been shown that the results of the multielement analysis are the a priori made initials
  • the non-destructive method for multi-element analysis based on neutron activation is automatically possible by this type of analytical procedure, in particular iteratively, with only the shape of the specimen and the mass and the Neutronenquell shelves are required as input parameters in particular.
  • the neutron source intensity can be obtained from the measuring system or device as a controlled variable.
  • analyzable samples include soil samples, ashes, water samples, sewage sludge, electronic scrap, chemotoxic or radioactive waste.
  • the analysis of samples can be done in batch mode or online at a mass flow. The analysis of samples may be performed for purposes such as quality assurance, targeted sorting, process control and / or verification.
  • the method according to the invention is characterized in particular by the following properties: continuous emission of fast neutrons; Continuous measurement of
  • Partitions in particular, the sample is irradiated with 2.45 MeV neutrons ( ⁇ IOMeV, comparatively small starting energy); Gamma radiation is evaluated by evaluating the signal of each partition; the analytical evaluation for the determination of the element masses takes place in particular based on the simplified assumption that the element mass is homogeneously distributed in a partition; and / or there is a rotation and axial displacement of the specimen to the detector.
  • the fast neutrons can be moderated in a moderation chamber, in the sample chamber and / or in the sample itself until they are sufficiently thermalized.
  • the analysis has hitherto usually been carried out by a method having the following properties: pulsed irradiation with fast neutrons; Measurement of the gamma spectra in predefined time intervals or time windows after a respective neutron pulse or between the individual neutron pulses; the sample is measured integrally without defining a collimator; in particular, the sample is irradiated with 14.
  • IMeV neutrons > 10 MeV
  • there is a rotation of the specimen in front of the detector and the gamma radiation is measured as a function of a rotation angle of the irradiated sample
  • the analytical evaluation for the determination of inhomogeneously distributed element masses is based on the simplified assumption that the element mass is punctiform.
  • the integral neutron flux in the sample can be determined by means of a metallic coating of the sample.
  • a shielding is preferably a material or a unit to understand what / which encloses the device or measuring system and reduces the gamma and Neutronenortsdosis elaborate outside the measuring system.
  • irradiation it is preferable to understand an operation of a neutron generator and generation and emission of neutrons on at least one sample in order to control the emission of the neutron
  • the detector unit is preferably a unit or module of the measuring system, comprising one or more detectors, with which detector unit the gamma radiation emitted from the sample or from individual partitions of the sample is measured in high-resolution.
  • a respective detector may have an extension of e.g. 5 to 10cm in one spatial direction.
  • a collimator is preferably a unit or module of the measuring system which limits the field of view of a detector to a spatial area with a higher detection probability for gamma radiation. Collimation may also be specific to individual segments / partitions of the sample.
  • a measuring system is preferably a metrological system for generating ionizing radiation to understand the purpose of the multi-element analysis of samples.
  • the device described here can be used in one
  • Embodiment be referred to as a measuring system.
  • moderation chamber is preferably an assembly of the measuring system for the moderation of neutrons to understand, in particular by means of graphite or at least partially made of graphite.
  • the moderation can optionally be provided in the sample chamber, and / or in a separate moderation chamber.
  • a neutron generator is preferably an assembly of the measuring system which emits fast neutrons (in particular 2.45MeV neutrons or, more generally, also neutrons with ⁇ 10 MeV) and is arranged inside the shield.
  • the neutron generator may optionally be surrounded by a moderation chamber provided separately from the sample chamber.
  • the neutron flux is preferably a product of the neutron density (free neutrons per cm 3) and the mean amount of the speed of the neutrons (cm / sec).
  • a partition is preferably to be understood as a predefinable / predefined spatial area within the sample, the sum of all partitions resulting in the entire sample or defining the entire sample body.
  • a preferred number of partitions may be chosen depending on the size of the sample and the metrological task, for example between 1 and 60 partitions.
  • the volume of a Partition are in the range of a few cubic centimeters to liters. For very small samples, eg a few cubic centimeters, it may be advantageous to define only a single partition.
  • the photopeak efficiency is preferably a detection probability for the complete energy deposition of a gamma emission in the detector.
  • gamma emission gamma radiation can be understood regardless of their energy level. Specific gamma radiation has a specific energy. Gamma emission as such is the reaction after irradiation with neutrons. The analysis is therefore specific to individual species of
  • Gamma radiation is performed from the spectrum of a gamma emission.
  • the gamma emission spectrum is used to detect signals of prompt and delayed gamma radiation.
  • a solid or liquid amount of material which is selected for analysis and is the subject of the investigation, e.g. including soil samples, ashes, water samples,
  • Sewage sludge Sewage sludge, chemotoxic or radioactive waste.
  • the sample chamber is preferably an assembly of the measuring system in which the sample is placed during the irradiation, and in which the sample can optionally also be displaced, in particular during the irradiation.
  • sample carrier is preferably an assembly of the measuring system to understand, which receives the sample and which is arranged in the sample chamber. By means of the sample carrier, a local displacement of the sample can take place.
  • a sample within a measuring system is continuously irradiated with neutrons and measured simultaneously to the irradiation induced by the neutron interactions / emitted gamma radiation.
  • gamma radiation is, on the one hand, prompt gamma radiation emitted immediately after interaction of the neutrons with the atomic nuclei of the sample, and, on the other hand, delayed gamma radiation, which occurs upon decay of the activated atomic nuclei in accordance with
  • the characteristic half-life is emitted.
  • the gamma radiation emitted from the sample can be measured in an energy-resolved manner in one or more detectors. This results in a measured gamma spectrum, per detector.
  • the gamma spectrum is the recording of the number of events detected in a gamma detector as a function of energy.
  • the energy of the gamma radiation is used to identify the elements of the sample. By means of the measured energy-dependent radiation intensity, the quantification of an element mass can take place. Calculation of element masses for partitioned and non-partitioned measurements
  • the mass fraction of an element contained in the sample, after subtracting the background signal, is calculated from the area of the photopeaks produced by the element in the gamma spectrum.
  • Multi-element analysis registered net photopeak count rate is dependent on the following influencing parameters, which relationship was particularly considered in the following publication: GL Molnar (Ed.), Handbook of Prompt Gamma Activation Analysis with Neutron Beams, Kluwer Academic Publishers, ISBN 1-4020-1304-3 (2004).
  • x is the position in the sample space ' ⁇ ' ,
  • n ⁇ x) is the distribution function for the mass of the corresponding element in the sample void
  • the partial gamma-production cross-section is dependent on the considered element and includes both the intensity of the considered gamma line ⁇ and the natural frequency of the associated isotope of the element. Since the irradiated elements in the sample usually emit gamma radiation at different energies, all evaluable gamma energies Ey of an element in the analytical
  • the sample is divided into partitions and segmented measured / analyzed.
  • one or more partitions of the sample are located in the collimated field of view of the detector in a single gamma-spectrometric measurement (FIG. 4).
  • the field of view of the detector is the spatial region, which has an increased detection probability of gamma radiation due to the collimator geometry. So that the respective partitions can be aligned optimally to the field of view of the detector, the sample can be moved in front of the detector, in particular rotated and displaced.
  • the energy-dependent detection probabilities of emitted gamma radiation from the sample or from a respective partition are referred to as photopeak efficiencies.
  • the gamma radiation is attenuated so that partitions facing the detector and located within the field of view of the collimator have higher photopeak efficiencies than partitions outside the field of view of the detector.
  • the load capacity of a measurement result with respect to the elemental composition of a respective partition can be increased, in particular if several gamma-spectrometric measurements are taken into account.
  • the SNR for each partition can be improved. If gamma-spectrometric measurements of several partitions are evaluated in combination, any remaining uncertainty can be reduced. It has been found that special advantages arise from a number of four partitions, depending on the size of the specimen.
  • the geometry of the partition is preferably defined as a function of the geometry of the specimen and the metrological task.
  • the sample is divided into partitions for cylindrical samples, in particular according to layers and sectors (FIG. 4).
  • partitions are generated in the manner of cake pieces, ie as three-dimensional
  • Symmetry axis of a cylindrical sample is called a layer, and an angle-dependent partitioning is called an (angle) sector.
  • an angle-dependent partitioning is called an (angle) sector.
  • these partitions are referred to specifically as a radial sector.
  • a cubic or cuboid sample can be subdivided into individual voxels. Each voxel represents a partition. The respective voxel also has a cubic or cuboid geometry.
  • Equation (1) For K partitions, N gamma spectra are recorded in N measurements, where K is greater than or equal to N, and there are N net photopeak counts for each gamma energy. Equation (1) can now, for K or N partitions, be reduced to the following sum for a gamma energy on collimated measurement of the partition / ' , where the index K passes through the partitions, promising a simple, robust analysis:
  • ⁇ Y is the integral photopeak efficiency of partition k in the measurement / '
  • equation (2) results in a linear equation system of dimension NxN or NxK, which can be solved according to the element masses of the individual partitions.
  • A is a matrix of dimension NxN or NxK and m
  • b are vectors of dimension N 1 and Kxl, respectively.
  • the entries of the matrix .4 are given by
  • the entries of m are given by mi, and the entries of b are given by mi
  • Equation (2) then reduces to the following simple linear relationship:
  • This equation can be solved directly after the element mass m.
  • the corresponding parameters can be calculated in the same way for the segmented / partitioned as well as the non-segmented case.
  • a mass m of the corresponding element is calculated, be it in a partition or in the entire sample volume.
  • the uncertainty u (m) at this value is determined according to DIN ISO 11929, which can also be taken from the following publication published by the German Institute for Standardization: Determination of the characteristic limits (detection limit, detection limit and limits of the confidence interval) for measurements of ionizing radiation - basics and applications (ISO 11929: 2010) (2011).
  • the mass of the element is calculated as the weighted average of the individual specific masses. The weighting is based on the calculated uncertainties.
  • the elements contained in the sample can be automatically identified based on the recorded gamma spectra. For each element, a characteristic emission signature of the gamma energies with corresponding intensities can be created from a nuclear physics database. The signals at the known gamma energies of the elements in the spectrum are matched by means of a computer program with this signature. A statistical analysis of the degree of agreement provides a list of the largest
  • the determination of the energy-dependent photopeak efficiencies of an element takes place by means of the assumption of a homogeneous element and mass distribution in a partition of the sample or of the entire sample.
  • the mean density of a partition of the sample may be determined by the mass of the sample divided by the sample volume and / or by a transmission measurement by means of a gamma emitter, e.g. Co-60 or Eu-154 can be determined.
  • the transmission measurement can serve as an extended measurement to characterize the sample, for example, to determine the filling level of a fluid to be examined or a bed in a barrel (sample) can.
  • the neutron flux and the energy-resolved neutron spectrum within the sample or the individual partitions of the sample are determined by an analytical method.
  • a diffusion approximation of the linear Boltzmann equation can be solved numerically.
  • Input parameters for this system of equations are calculated from simulation calculations of the neutron flux and the neutron spectrum in the empty sample chamber and / or the metrologically detected neutron flux outside the sample.
  • the total or absolute neutron flux in each partition can optionally also be determined by one or more neutron detectors, which can be mounted outside the sample in the measuring chamber. From the measured data of the respective neutron detector, the total neutron flux in each individual partition can be reconstructed.
  • neutron detectors can be filled in particular with gas
  • Proportionalevenrohre with BF3 (BF 3 ) or 3He (He) are used, in particular as a neutron sensitive material, which is particularly suitable for the measurement of the thermal neutron flux.
  • the detector may have a cylindrical geometry, in particular with a useful length which corresponds to the height of the measuring plane. This facilitates the detection or measurement of the neutron flux of the entire plane.
  • the neutron detectors are preferably arranged within the measuring chamber at the points of the expected maximum and minimum thermal neutron flux and optionally also at additional locations, preferably adjacent to the openings of a / of the collimator, in particular in each case equidistant from the neutron source point (neutron source).
  • at least four neutron detectors are arranged in the measuring chamber at the level of the detectors.
  • Determination of the vertical distribution of the neutron flux can be provided in planes above and below the measurement plane the same arrangement of neutron detectors, in the sense of redundant Neutronendetektoren- levels.
  • the reconstruction or determination of the total neutron flux in the partitions from the measurement data obtained in this way can take place, in particular, taking into account the adjusted neutron source strength, the weight and volume of the sample and the (spatially resolved) material composition of the sample. In this case, recourse can be made to the material composition of the sample.
  • the reconstruction can be done as part of an iterative evaluation process of the measurement data.
  • a spatially resolved reconstruction takes place in particular taking into account a known attenuation behavior of the sample material (in particular taking into account attenuation coefficients) on the neutron flux and based on simulatively determined characteristics of the neutron flux at the respective measuring points in dependence of previously described influence or input parameters.
  • a neutron detection in the sample chamber in addition to the gamma ray detection, a neutron detection in the sample chamber, in particular for the purpose of measuring the total neutron flux integral over an energy range such that the respective neutron fluxes can be reconstructed in the respective partitions.
  • the respective element mass can be calculated from the total neutron fluxes and from the neutron spectra and the measured gamma spectra be quantified. This provides a good load capacity and validity of the measurement results.
  • Neutron generator can be used as input.
  • neutron flux in the sample has been determined by integrally determining energy-dependent correction factors for the entire sample. This manner of calculation has been particularly considered in the following paper: A. Trkov, G. Zerovnik, L. Snoj, and M. Ravnik: On the self-shielding factors in neutron activation analysis, Nuclear Instruments and Methods in Physics Research A , 610, pp. 553-565 (2009).
  • an approximate method for determining the neutron flux without energy dependence was proposed in the 1994 edition of R. Overwater, detailed below, in particular for special geometries that allow a reduction to two spatial dimensions.
  • the neutron flux and the neutron spectrum within the sample or within individual partitions of the sample can be determined automatically (by a computer program) in the method described here, whereby a diffusion approximation of the linear Boltzmann equation is spatially and energy-resolved (considering all three spatial dimensions) numerically can be solved and the input parameters for this system of equations from simulation calculations of the neutron flux and the neutron spectrum in the empty
  • Sample chamber and / or from the metrologically detected neutron flux outside the sample (material to be measured) can be calculated.
  • the spatially and energy-resolved neutron flux in the sample can be determined from the solution of the full Boltzmann transport equation for the neutrons:
  • Et denotes the total and Es the scattering cross section for neutron of the sample material, which consist of the individual cross sections of the elements contained in the sample.
  • Equation (6) is approximated by a coupled system of diffusion equations, according to the so-called SP3 approximation, which relationship was particularly considered in the following publication: PS Brantley and EW Larsen, The simplified P3 approximation, Nuclear Science and Engineering, 134, pp , 1-21 (2000).
  • This equation system is numerically in multigroup form by means of a
  • the parameters of the system of equations result from the elemental composition of the sample, wherein in the first step the Input parameters from the simulated neutron flux and the neutron spectrum in the empty sample chamber and / or from the metrologically detected neutron flux outside the sample are calculated, in particular under an assumption of homogeneity of the sample and the elemental composition of the sample or partitions.
  • the calculation and evaluation of the neutron flux and spectrum can each be done individually for a particular partition, in particular by defining the respective partition based on a virtual subdivision of the sample into spatial regions.
  • the result of the analytical evaluation, or the most important result, is the elemental composition of the sample.
  • the evaluation is preferably based on parameters relating to the energy-dependent photopeak efficiency, the neutron flux and the neutron spectrum within the sample or within the partitions of the sample.
  • shape / geometry and mass of the specimen and neutron source strength can thus take into account the three calculated parameters energy-dependent photopeak efficiencies, neutron flux and neutron spectrum within the sample and within the partitions of the sample a very comprehensive analysis.
  • These parameters are influenced by the elemental composition of the sample, so that the process is preferably carried out iteratively until the calculated elemental composition no longer or substantially does not change significantly. Referring to Fig. 3, a possible way of iteration will be described in more detail.
  • the input parameters become an initial
  • Neutron flux and an initial neutron spectrum calculated (step Sl).
  • the exact nature of the collimation and optionally the partitioning of the sample can additionally be taken into account, and furthermore also a translation and / or rotation of the sample which is advantageous for the course of the measurement can be taken into account (step S2).
  • the type of collimation and the partitioning of the sample can in particular be made dependent on the size and geometry of the sample. Larger samples and complex geometries are divided into more partitions than small samples.
  • the evaluation of the recorded gamma spectrum comprises the identification of the elements contained in the sample by an assignment of the measured peaks in the spectrum to individual elements, taking into account interferences between gamma peaks.
  • step S3 The net count rates for the individual gamma energies are preferably calculated only once and kept constant within the iterative method (step S3). From this, an initial elemental composition of the sample is calculated. Using the steps described below for calculating the photopeak efficiencies (step S4), the element masses in the individual partitions of the sample (step S5) and the neutron flux and the
  • Neutron Spectrum determines the elemental composition of the sample. This process is iterated until the elemental composition in the individual partitions does not change. By the iterative analytical procedure, a high accuracy is achieved. In particular, the net count rates at the individual gamma energies are calculated only once and kept constant during the iterative process. At the beginning, an initial assumption about the elementary
  • composition of the sample taken. Using the methods described in the previous sections to calculate the photopeak efficiencies, the neutron flux and the neutron spectrum and the elemental masses in the individual partitions of the sample, a new elemental composition of the Partition determined. This process can be iterated until the
  • the non-destructive method for multi-element analysis based on neutron activation described here is automatically or fully automated by this analytical procedure for the first time, especially over a longer period, especially for large-volume samples, especially already from about 1 liter.
  • Input parameters are only the shape of the specimen and the mass required, with the neutron source strength being taken into account in the calculation.
  • the neutron source intensity is determined from the operating parameters of the neutron generator or from the activity of the neutron source.
  • the respective sample is continuously irradiated with neutrons, and the gamma radiation emitted from the sample and the amount of an element contained in the sample are measured and evaluated after subtracting the background signal from the surface of the photopeak, the causes the element, especially in a count rate energy representation.
  • the composition of the sample is known for at least a portion of the sample.
  • Neutrons are to be understood as fast neutrons, which are fast when emitted from the source and which are then slowed down by a sample chamber and / or by a moderation chamber, in particular in order to be able to increase the probability of interaction with the sample.
  • Moderator slowed neutrons can be called thermalized neutrons.
  • Thermalized neutrons are slow or decelerated free neutrons, especially with a kinetic energy of less than 100 microvolts (milli-electron volts). In a classification for neutrons thermalized neutrons or thermal neutrons lie between the cold and the fast neutrons. The term
  • Thermalized indicates that the neutrons are scattered by repeated scattering in a medium
  • the irradiation or the irradiation and measuring take place over a period of at least one millisecond or at least one second.
  • the measurement of radiation emitted in response to the irradiation during irradiation occurs in a time window of less than 5 microseconds ⁇ sec.).
  • the irradiation takes place over a period of at least 10 minutes, or at least 30 minutes, or at least two hours, without interruption.
  • An optimal irradiation time is in
  • the continuous irradiation over such periods allows a reliable evaluation of the measurement data in a flexible manner, in particular also specifically with regard to individual sub-aspects.
  • the irradiation time can be particularly with regard to a required Sensitivity of the analysis task can be defined. It has been shown that the likelihood of detecting trace impurities (traces in the trace range) increases with increasing irradiation time.
  • the sensitivity of the measuring method according to the invention can be increased with increasing time. Irradiation time and iteration can be defined independently of each other.
  • the minimum irradiation duration can be defined as an irradiation time in the range of seconds.
  • the maximum irradiation duration can be defined as an irradiation time in the range of seconds, minutes, hours or even days.
  • neutrons are generated with the neutron energy value 2.45MeV or with at least one neutron energy value from the following group: 2.45MeV, 14.ImEV. It has been shown that with neutrons with 2.45MeV a particularly good signal can be obtained, thus a signal with favorable SNR.
  • neutrons are generated with a neutron energy having at least one value in the energy range 10KeV to 20MeV, in particular 10KeV to 10MeV.
  • neutrons are generated with a neutron energy of maximum lOMeV.
  • This provides in particular a high sensitivity.
  • neutron energies less than or equal to lOMeV, especially neutron energies of 2.45MeV, it has been found that many inelastic interactions do not occur as threshold responses with neutron energies of at least 3 to 4 MeV required. Such inelastic interactions degrade the SNR.
  • By keeping the energy of the neutron source as low as possible, such inelastic interactions below the selected neutron energy can be avoided.
  • only the neutron energies 2.45 MeV are used.
  • At least prompt or both prompt and delayed gamma radiation from continuous neutron irradiation is measured and evaluated.
  • the evaluation of both types of gamma radiation extends the analysis possibilities and increases the flexibility of the method. It has been shown that it is useful to evaluate the following reaction of an irradiated atomic nucleus without having to consider a time dependence of any neutron pulse: as soon as an atomic nucleus captures a neutron, gamma radiation is automatically emitted at different energies.
  • the atomic nucleus excites itself by emitting a cascade of gamma emissions.
  • the generated gamma radiation is characteristic for a respective element.
  • the gamma radiation emitted from the sample is measured in an energy-resolved manner, in particular by determining photopeak count rates, wherein the determining comprises an energy-resolved evaluation of the measured gamma radiation according to at least one of
  • Gamma spectrum comprises, in particular according to a detected with a respective detector gamma spectrum.
  • the same detector can be used for both prompt and delayed gamma radiation.
  • the energy-resolved analysis allows flexibility and robustness. As a result, a parallel analysis of almost all elements is made possible with one measurement.
  • the measured gamma spectrum is specific to a detector.
  • the respective detector may have a specific resolution each for a specific gamma spectrum.
  • the measuring / evaluating comprises an energy-resolved measurement / evaluation of the intensity of the gamma radiation emitted from the sample. This provides in particular in connection with the
  • the determining comprises evaluating the measured gamma radiation, wherein the evaluating comprises correlating at least one photopeak of a count rate energy representation based on its energy with an element of the sample. This provides a comprehensive analysis of both prompt and delayed radiation, particularly for a gamma spectrum measured with one of several detectors.
  • the detected photopeak may be a photopeak that characterizes a prompt or delayed gamma radiation.
  • a distinction between prompt and delayed gamma radiation in the evaluation can be made based on the respective energies, in particular also in photopeaks in which two gamma energies interfere.
  • a distinction between prompt and delayed peaks remains independent of such interference.
  • the determination of a respective photopeak efficiency can be carried out for both types of gamma radiation spatially and energy resolved by a numerical method in which the interactions from the location of the emission in the sample (source point) are imaged until absorption in the detector.
  • the evaluation comprises: quantifying the mass fraction of at least one element of the sample, in particular by evaluating the fraction of at least one element contained in the sample after subtracting a background signal from the net area of a photopeak which the element has detected in a count rate energy index. Representation causes.
  • the photopeak can be fitted in the spectrum.
  • the area under the photopeak can be considered
  • Underground / subsurface signal can be defined, and the net photo opaque area can be defined as a useful signal.
  • the sample in particular individual partitions of the sample, is / are measured collimated, in particular by means of at least one detector or by means of a plurality of detectors specific to the geometry of the partition collimated field of view.
  • This can increase accuracy and also allows focusing on portions of the sample, especially with good SNR.
  • two or more detectors there are advantages in particular with regard to the measuring time. It has been found that in the method described here, the measurement time can be selected the lower, the more detectors are provided, and / or that with the same measurement time, the sensitivity of the measurement can be increased.
  • the sample is divided into partitions and the emitted gamma radiation is measured and evaluated with respect to a respective partition using a collimator.
  • Embodiment takes place measuring, determining and / or evaluating individually with respect to individual partitions of the sample, which partitions are predefined or manually or automatically predetermined, in particular by collimation. This allows a focus on individual regions of the sample, or facilitates the evaluation of large-volume samples or samples with inhomogeneous composition.
  • Partitioning simplifies the analysis, especially with regard to a desired accuracy of the evaluation. Partitioning may, as a result, allow for spatially resolved elemental composition in the respective partitions. Partitioning also provides the advantage that assumptions can be made more easily or with less error. For example, in a cylindrical specimen eight or more partitions, in particular 12 partitions are formed, each as a cylindrical segment (cake piece).
  • the detector unit then comprises e.g. two detectors that are not opposite each other, but offset by an angle to each other
  • the collimation can take place in particular as a function of the selected partitioning.
  • a control device of the device can be set up to specify the collimation as a function of the selected partitioning.
  • the following relationship between collimation and partitioning then be given:
  • the entire partition is preferably in the collimated field of view of the detector. In this case, only the smallest possible proportion of space is available from other partitions, that is, from partitions that are not collimated to the target partition that is collimated, in the collimated field of view of the detector. Due to the optionally adjustable geometry of the collimator, the viewing area can be limited primarily to the target partition.
  • collimated measuring is to be understood as meaning, in particular, detection of the gamma radiation with at least one detector with a collimated field of vision. It has been shown that the method described here also thanks
  • Collimation can be carried out continuously over a long period of time with particularly advantageous SNR.
  • the determining comprises an evaluation of the measured gamma radiation, wherein the evaluation is based on the assumption of a homogeneous mass and / or element distribution in the sample, in particular a homogeneous mass and / or element distribution in at least one of several partitions the sample.
  • the element and mass distribution can be assumed to be homogeneous, so that the respective partition can be uniformly calculated / evaluated.
  • the measurement accuracy can also be increased by geometrically selecting the partitions so that the assumption of homogeneous mass distribution applies as well as possible, e.g. no pieces of cake instead of slices in the height direction one above the other.
  • previous methods often used the analytical approach that the elements are point sources.
  • one of two initial assumptions can be made: either point source or homogeneous element and mass distribution in a partition. It has been found that the assumption of a homogeneous element and mass distribution in connection with the method described here can lead to a very robust measurement with minimized uncertainty.
  • the determining comprises an evaluation of the measured gamma radiation, wherein the evaluation comprises: spatially and energy-resolved calculation of the neutron flux within the respective partition of the sample, in particular based on a diffusion approximation of the linear Boltzmann equation, in particular based on the following relationship:
  • the evaluation also includes calculating the neutron spectrum within the sample, in particular within a respective partition of the sample, in particular spatially and / or energy-resolved, in particular based on the following relationship:
  • the determining comprises evaluating the measured gamma radiation, wherein the evaluating comprises: calculating energy-dependent photopeak efficiencies as well as neutron flux and neutron spectrum within the sample or within a single partition of the sample, in particular calculating neutron flux and neutron spectrum by an approximate method, each based on the following relationship:
  • This provides the aforementioned advantages. It has been shown that the energy-dependent photopeak efficiencies, the neutron flux and the energy-resolved neutron spectrum within the sample or within the individual partitions of the sample provide a reliable basis for the evaluation.
  • the input parameters can be calculated from the neutron flux and the neutron spectrum in the empty sample chamber and / or the metrologically detected neutron flux outside the sample.
  • diffusion approximation enables calculation based on a small number of independent variables. This can also reduce the complexity of the analysis.
  • a very accurate alternative method would be a numerical solution of the full linear Boltzmann equation, either deterministically or by means of a Monte Carlo method. In both variants, however, the computational effort would be very high, especially during iteration would have to be calculated with a computing time in the range of hours or even days.
  • a diffusion approximation provides a simple mathematical structure, which allows the use of simple numerical methods.
  • the determining comprises evaluating the measured gamma radiation, the evaluation taking place at least partially with respect to the measured photopeak areas by detecting a plurality of photopeak areas, which are of a plurality of gamma energies respectively of at least one element in a respective partition Sample when quantifying the mass fraction of a particular element of the respective partition based on the following relationship (each for N or K partitions where the index K passes through the partitions):
  • a plurality of gamma energies of at least one element in each partition of the sample can be analyzed in quantifying the mass fraction of each element.
  • the neutron flux in the sample has so far been determined by determining energy-dependent correction factors integrally for the entire sample. It has been shown, in particular for large-volume samples, that an approximate method for determining the neutron flux without energy dependence and for specific geometries that allow a reduction to two spatial dimensions can also be used. Such a method is based in particular on a diffusion equation which is determined by only two parameters. In particular, aspects of a method can be applied, the relationships of which have already been considered in detail in the following publication: R. Overwater, The Physics of Big Sample Instrumental Neutron Activation Analysis, Dissertation, Delft University of Technology, Delft University Press, ISBN 90-407- 1048-1 (1994).
  • the neutron flux and neutron spectrum within the sample or individual partitions of the sample can be determined by a computer program according to the present method a diffusion approximation of the linear Boltzmann equation can be solved numerically in a spatially and energy-resolved manner, in particular taking into account all three spatial dimensions.
  • the boundary conditions for this system of equations can be calculated from simulation calculations of the neutron flux in the empty sample chamber and / or the metrologically detected neutron flux outside the sample. Energy-dependent correction factors are not required or need not be defined.
  • the calculation and evaluation of the neutron flux and spectrum can each be done individually for a particular partition, in particular by defining the respective partition based on a virtual subdivision of the sample into spatial regions.
  • the method is carried out based on the input parameters neutron source strength, sample geometry and sample mass, in particular exclusively based on these three
  • Input parameters This can automate the process to a high degree. There are then only three input parameters to specify. Further parameters can be determined numerically / automatically. As a result, the effort on the part of a user can be minimized.
  • Other input parameters may e.g. by nuclear physics data or by the simulative computation of the input parameters for neutron flux and neutron spectrum calculations.
  • a monitor, or a calibration material of prior art composition may be analyzed along with the sample. This can increase the measurement accuracy or the load capacity of the measurement, in particular at
  • the use of a monitor and the evaluation of gamma radiation emitted by the monitor may optionally be done independently of the aspects of the method and apparatus described herein.
  • a material can be used which is certainly not found in the sample, for example, gold in the form of a very thin gold foil, which is placed on the sample.
  • the method is carried out automatically, in particular by evaluating the measured gamma radiation based on apart from the three parameters neutron source intensity in the irradiation, sample geometry and sample mass, exclusively numerically determined parameters. This provides autarky and the ability to easily iterate. The process becomes more robust. In this case, a neutron flux can also be detected by means of neutron detectors outside the sample.
  • Sample geometry can be detected autonomously by a camera unit, and the sample mass by a
  • the device may have a measuring station for sample specification, at which measuring station the sample can be automatically characterized.
  • the neutron source intensity can be obtained directly as a controlled variable from the neutron generator.
  • the neutron source strength is directly dependent on the high voltage and the current intensity of the neutron generator.
  • At least one measurement from the following group is carried out to characterize the sample: transmission measurement, sample weighing, optical detection of the sample geometry. On the one hand this facilitates the handling of the measuring method for the user, and on the other hand it also facilitates the subsequent measurement, in particular also with regard to a partitioning.
  • the method is carried out iteratively, in particular in each case with regard to individual elements or with respect to the complete composition of the sample or with respect to individual partitions
  • Sample and / or the complete composition of the sample This provides good accuracy, especially in an easy-to-use process. This also provides a method with a high degree of autarchy.
  • the spatially and energy-resolved determination of the neutron flux takes place within the sample chamber (outside or) externally of the sample, in particular by means of at least one neutron detector arranged within the sample chamber.
  • This also facilitates the determination of the absolute or total neutron flux, be it in addition, be it alternative to a determination with respect to a respective partition.
  • the invention also relates to a method for multi-element analysis based on neutron activation, comprising the steps of: generating fast neutrons with energy in the range of 10KeV to 10MV; Irradiating a sample with the neutrons;
  • Gamma radiation from continuous neutron irradiation is measured and evaluated, wherein the evaluation is based on the assumption of a homogeneous mass and / or element distribution in the sample or in at least one of several partitions of the sample. This results in many of the aforementioned advantages.
  • the measurement / evaluation can take place independently of the time course of the irradiation or independently of individual phases of an irradiation.
  • At least one of the aforementioned objects is also achieved by using a detector unit having at least one detector in the multi-element analysis of a sample based on neutron activation configured to continuously measure both prompt and delayed gamma radiation due to continuous irradiation of the sample with neutrons, the gamma radiation at least partially also continuously, ie independent of the time of irradiation and independent of any neutron pulses, in particular without time window, and is measured simultaneously for continuous irradiation, wherein the field of view of the detector unit to the respective partition of the sample by means of at least one
  • Collimator is limited, in particular use of the detector unit with a plurality of detectors each collimated or partition collimated or adjustably collimated with respect to at least one partition or with respect to at least one predefinable geometry of a partition, preferably with a collimator of lead or bismuth.
  • the invention also relates to the use of at least one neutron source for multi-element analysis of a sample based on neutron activation for generating fast neutrons for continuously irradiating the sample with first neutrons having at least one neutron energy value from the following group: 2.45MeV, 14.ImEV; and / or with second neutrons having a neutron energy of at least one value in
  • the emitted gamma radiation is detected with a detector with a collimator of lead or bismuth.
  • At least one of the abovementioned objects is also achieved by a control device configured to control at least one neutron generator of a device for multi-element analysis based on neutron activation, in particular a device described here, wherein the neutron generator is set up to generate fast neutrons with energy in the range of 10 kV to 20 MeV , In particular LOkeV to lOMeV, wherein the control device is adapted to drive the
  • a neutron generator for generating the neutrons and irradiating the sample in an unpulsed continuous manner, particularly during at least a first time window, and wherein the controller is further adapted to drive at least one detector for continuously and / or temporarily measuring from the sample or a single partition Sample emitted gamma radiation simultaneously to the irradiation, in particular during at least a second time window independent of the first time window, continuously simultaneously to the continuous irradiation and / or time-independent thereof.
  • the first and second time windows can be different or can be predefined or set independently of one another.
  • Control means is further arranged to restrict the field of view of the detector to the respective partition of the sample by means of at least one collimator.
  • the control device is in particular configured to control a previously described method.
  • the control device can synchronize at least the irradiation, measuring and optionally also the positioning of the sample (in particular by activating / controlling a rotary / lifting device) and thus control the actual measuring method of the measuring system, in particular the way and the period of data collection.
  • the irradiation and measuring in particular over a period of, for example, at least 20 or 50 seconds. take place, or even over several hours or days.
  • the control device can be coupled to a rotary / lifting device and further be set up for positioning a sample arranged on a sample carrier by means of the rotary / lifting device, in particular according to or in dependence on the geometry of partitions of the sample.
  • parameters such as the neutron source intensity can be specified for the neutron generator, and the Rotary / lifting device position data or displacement paths and displacement speeds can be specified.
  • the controller may be configured to control the operation of a neutron generator configured to merge deuterons to generate fast neutrons for multi-element analysis of a sample by continuous, unpulsed irradiation of the sample.
  • the device or the controller may be an input mask (user interface) or
  • Input unit for manual input of the following three parameters: neutron source intensity in the irradiation, sample geometry and sample mass. These parameters can also be stored in a data memory and read out by the control device and transferred to a computer program product.
  • At least one of the aforementioned objects is also achieved by a computer program product for multi-element analysis based on neutron activation, and arranged to determine at least one element of an unpulsed continuously neutrally irradiated sample by evaluating emitted from the sample gamma radiation, namely prompt and / or delayed gamma radiation, based on
  • This system of formulas relates to the determination according to the invention of elemental masses in the individual partitions (evaluation of the formulas for all masses of the individual partitions, in particular simultaneously).
  • This computer program product allows a high degree of automation or autarky, in conjunction with a high accuracy of the analysis.
  • the computer program product is in particular set up for automatically carrying out a previously described type of evaluation.
  • partition collimated evaluation an evaluation is to be understood individually with regard to individual partitions of the sample, which partitions were previously geometrically defined and delimited from each other.
  • the computer program product can also be set up for specifying a desired position of the sample, in particular as a function of a detected or entered sample geometry, in particular based on setpoint positions stored in a position database as a function of the sample geometry and / or sample size, the positioning being determined in particular by activation / Rules of a rotary / lifting device can be done.
  • the computer program product can be set up to calculate different variants of a partitioning for a respective sample geometry and to propose a partitioning identified as optimally or to select it directly autonomously.
  • the computer program product can carry out a rough uncertainty analysis as a function of the number and configuration of the partitions and determine or autonomously determine the partitioning as a function of the accuracy required by the user. With this procedure, a configurable collimator can be set specifically with regard to the selected partitions.
  • the invention also relates to a data carrier with such a computer program product deposited thereon, or a computer or a computer system or a virtual machine or at least one hardware element with it.
  • the invention also relates to a computer program configured to provide the manner and manner of evaluation described herein or the method steps described herein.
  • the computer program product is configured to evaluate an integral measurement, in particular with respect to a non-partitioned sample based on a single gamma spectrum, in particular based on the following relationship:
  • the respective sample is continuously irradiated with fast neutrons, the gamma radiation emitted by the sample being measured simultaneously with the irradiation, the quantity of an element contained in the sample, after subtraction of the background signal, being evaluated from the net surface of the photopeak, which the element causes in a count rate energy representation.
  • the quantification of the elemental masses of a sample can be automated, and the parameters required for the analysis, except for the neutron source intensity in the irradiation and the geometry and total mass of the sample, can be calculated numerically.
  • a monitor for the neutron flux or a sample internal or external calibration standard is not required.
  • the sample can be decomposed into areas of space (partitions) and each partition of the sample can be measured in color.
  • the determination of the element masses of the sample can be based on the fact that the elemental and mass distribution in individual partitions of the sample is assumed to be homogeneous.
  • the average density of a partition can be measured by a transmission measurement with a radioactive gamma emitter.
  • the neutron flux within the partitions of the sample can be determined by an analytical method which numerically solves a diffusion approximation of the linear Boltzmann equation and boundary conditions for this system of equations from simulation calculations of the
  • Neutron flux in the empty sample chamber and / or the metrologically detected neutron flux outside the sample calculated.
  • the determination of photopeak efficiencies can be spatially and energy resolved by a numerical method in which the interactions of the emission in the sample (source point) to the absorption in the detector are mapped.
  • the process can iteratively with respect to Composition of the sample are carried out until the calculated composition of the sample stabilizes.
  • all detected photopeak areas which are produced by different gamma emissions of an element in the sample can be taken into account in the analytical evaluation. In doing so, the results of the measurement of each partition can be taken into account in the analytical evaluation, whereby the sensitivity and the accuracy of the measurement procedure for the entire sample can be improved.
  • the neutron source and the sample may be located in a sample chamber made of graphite as a moderation chamber.
  • an effective shield for neutron radiation can be located directly around a moderation chamber or around the sample chamber.
  • the detector or the detector unit may be located in a collimator of gamma-rays shielding material.
  • the geometry of the sample and moderation chamber and / or the sample carrier reduce the Neutronenhnegradienten within the sample, which in particular by means of variable moderation lengths (distance between
  • Neutron source / neutron source point and sample can be achieved, with the effect that the
  • Neutron flux gradient is reduced or changed. At least one of the aforementioned objects is also achieved by a device for multi-element analysis based on neutron activation, comprising:
  • a neutron generator adapted to generate fast neutrons
  • a detector unit having at least one detector configured to measure gamma radiation emitted from an irradiated sample to determine at least one element of the sample; wherein the device is arranged for unpulsed continuous irradiation of a sample arranged on the sample carrier and is arranged to measure prompt and / or delayed light emitted from the irradiated sample
  • the device has at least one collimator which limits the field of view of the detector to a respective partition of the sample and is arranged for subdividing the sample into individual partitions, and is furthermore designed to measure emitted from the continuously irradiated sample at least more promptly or both prompter and delayed gamma radiation with respect to a respective partition of the sample during irradiation.
  • the apparatus further comprises: a control device configured for automated continuous irradiation and arranged for controlling an automated measurement of continuously applied neutron irradiation during the irradiation.
  • the apparatus is further configured for spatially and energy resolved determination of the neutron flux within the respective partition of the sample and arranged to evaluate the measurements of the partitions by quantifying the mass fraction of the at least one element of the sample.
  • a semiconductor or scintillation detector is preferably used, ie a detector with high energy resolution, which is set up for the measurement of the prompt and delayed gamma radiation.
  • the method is varied by means of a moderation chamber provided independently of the sample chamber.
  • the moderation chamber can be provided / installed in the device in a stationary manner.
  • the process of moderation can be performed in the desired manner in the sample chamber, in the moderation chamber and / or in the sample itself.
  • the respective detectors of the device can be focused by at least one collimator.
  • a collimator adapted to predetermining or narrowing or adjusting the field of view of the detector provides in particular the advantage of an improved SNR, especially in connection with continuous irradiation.
  • the sample can be measured partition collimated.
  • a plurality of detectors are arranged in the same height level, in particular in the height level of the neutron source or the neutron source point.
  • the detector or detectors are arranged as close as possible to the neutron source point. This provides good measurement results or allows minimizing
  • the detectors are preferably offset by less than 90 ° in the circumferential direction relative to the neutron source point, for example by 60 or 75 °.
  • the neutron source point here is preferably the location or the position at which the neutrons are emitted, in particular emitted into the sample chamber onto the sample.
  • the neutron generator can be arranged independently of the position of the neutron source point, or the position of the neutron source
  • the collimator as well as a moderation chamber, can be permanently installed in a single predefined setting or configuration.
  • the collimator may also have multiple settings, each for a predefinable field of view, e.g. a first setting with a relatively wide / wide field of view, a second setting with a medium field of view, and a third setting with a relative
  • the collimator can be switched between the settings.
  • the device comprises at least one component which attenuates a background signal of the device from the following group: at least one collimator which limits the field of vision of the (respective) detector to a partition of the sample, preferably a collimator of lead or bismuth.
  • the device may further comprise: a graphite moderation chamber, and / or a borated polyethylene shield, and / or a sample chamber and / or a sample carrier, each at least partially made of graphite or fully fluorinated plastics or beryllium. In this way, in particular, an improved SNR can be achieved.
  • the collimator preferably has a wall thickness of at least 5 cm.
  • the device can sample nondestructively analyze the emitted gamma radiation with regard to numerous aspects.
  • the device is not limited to the evaluation of a particular type of gamma radiation or in a specific time window. It has been shown that an advantageous angle between neutron generator and detector is between 50 and 90 °, in particular since this can prevent the detector from being exposed to too high a neutron flux.
  • the detector can be focused in this angular range to a spatial area in which the neutron flux in the sample is maximally high.
  • gamma radiation from inelastic interactions (scattering processes) in previously used systems had produced such a strong background signal that the detection of gamma radiation was only possible after a certain waiting time (time window) after a neutron pulse.
  • the apparatus further includes a computer program product or data store therewith, wherein the computer program product is configured to determine at least one element of the sample by evaluating the measured gamma radiation based on energy dependent ones
  • Photopeak efficiencies as well as neutron flux and neutron spectrum within the sample or within a single partition of the sample in particular based on at least one of the above with respect to the
  • Multi-element analysis in particular in connection with a control device for controlling neutron emission, detectors and / or a rotary / lifting device.
  • the device further comprises a rotating and / or lifting device arranged for translational and / or rotational displacement of the sample carrier or the sample, preferably a decoupled from a / of the sample chamber of the device rotating and / or lifting device, wherein at least one electrical Drive the rotating / lifting device outside of a shield (in particular outside a borated polyethylene screen) of the device is arranged.
  • a shield in particular outside a borated polyethylene screen
  • the device further comprises a unit for measuring transmission, which is set up for determining the average density of the sample or the respective partition.
  • Transmission unit comprises a radioactive gamma emitter, in particular Eu-154 or Co-60, and a detector for measuring the attenuation of the gamma radiation after penetration of the sample.
  • the detector for measuring the attenuation of the gamma radiation may be one of the detectors for the prompt and delayed gamma radiation, or may also be a detector provided specifically for this transmission measurement.
  • the sample is not irradiated with neutrons. This allows the
  • the device comprises at least two detectors, in particular in a symmetrical arrangement relative to the neutron generator and / or relative to at least one neutron source or at least one neutron source point of the device.
  • the respective partition can be optimally positioned or aligned in front of a respective detector.
  • the partitions may be defined geometrically depending on the geometry of the sample, and the sample may be aligned accordingly, e.g. be completely turned in six steps.
  • the device further comprises a control device configured for automated continuous irradiation and / or set up for controlling automatic measurement with continuously applied neutron irradiation time-independent of the neutron irradiation simultaneously to the continuous irradiation, in particular adapted for iterative automated evaluation of the emitted and measured gamma radiation time independent from the neutron irradiation based on the three manually or automatically definable parameters neutron source strength at the
  • the neutron generator comprises at least one neutron source or a neutron source point configured for the fusion of deuterons (deuterium nuclei), in particular with deuterium gas as gaseous target or gaseous operating substance. It has been shown that a sufficiently high swelling strength can also be ensured by the fusion of deuterons. The use of this energy range provides advantages in continuous irradiation and also in measuring and evaluating, on the one hand due to low neutron energy, on the other hand with regard to a long irradiation time.
  • the neutron generator is an electrically operated neutron generator or comprises at least one radionuclide neutron source, such as e.g. an AmBe source. Preference is given to
  • Neutron generator which fuses deuterons and emits neutrons with a starting energy of 2.45 MeV by means of this fusion reaction.
  • a pulsed irradiation can be carried out especially at 2.45MeV.
  • previous pulsed irradiation is often a neutron generator for
  • the at least one detector is a semiconductor or scintillation detector. This allows accurate evaluation of both prompt and delayed gamma radiation in a wide range of energies.
  • the invention also relates to a device for multi-element analysis based on neutron activation, comprising: a neutron generator configured to generate fast neutrons;
  • a detector unit having at least one detector configured to measure gamma radiation emitted from an irradiated sample to determine at least one element of the sample; wherein the apparatus is arranged for unpulsed continuous irradiation of a sample and is adapted to measure prompt and / or delayed gamma radiation emitted from the irradiated sample, independently of the irradiation during irradiation, the apparatus comprising at least one sub-component signal attenuating component of the following group comprises at least one collimator restricting the field of view of the detector to the sample or partition, and / or a graphite moderation chamber, and / or a screen of borated polyethylene, and / or a sample chamber and / or a sample carrier in each case at least partially of graphite or completely fluorinated plastics or beryllium, wherein the device further comprises a control device configured for automated continuous irradiation and / or set up to control / regulate an automated measurement with continuously applied
  • Figure 1 is a perspective view in a schematic representation of a device for non-destructive multi-element analysis according to an embodiment
  • 2A, 2B, 2C each show in a sectional view a sample chamber with one or two detectors and in detail a detector of a device for non-destructive multi-element analysis according to an embodiment
  • FIG. 3 is a schematic representation of a flowchart of individual steps of a method according to an embodiment
  • Figure 4 shows a cylindrical sample with a partitioning in the form of disk segments, as a
  • FIG. 5 shows a sectional view of a sample chamber with a rotating and lifting device, arranged outside a shield, of a device according to one exemplary embodiment
  • Figure 6 is a schematic representation of a sample chamber with arranged therein
  • Neutron detectors of a neutron detector unit of a nondestructive multi-element analysis apparatus according to an embodiment.
  • FIG. 1 shows an assembly of a device 10 for non-destructive multi-element analysis, specifically in the manner of a measuring system for carrying out the method described here for multi-element analysis based on neutron activation.
  • a sample 1 is continuously irradiated with neutrons and measured simultaneously to the irradiation induced thereby / emitted gamma radiation.
  • the device / measuring system 10 together with sample 1 consists in particular of the following assemblies:
  • Neutron generator 11 comprises at least one electrically operated neutron source, in particular one
  • Neutron source which at least deuterium and deuterium (or deuterons) fused, and optionally allows another type of fusion, in particular tritium and deuterium.
  • the deuteron fusion reaction emits fast neutrons with an energy of 2.45MeV.
  • Deuterium gas is preferably used as target (non-radioactive).
  • at least one further energy value, in particular 14 IMeV, can also be provided by means of the neutron generator.
  • the neutron generator 11 is located within a moderation chamber 12 and is surrounded by a shield 19.
  • the moderation chamber 12 is made of a material which moderates fast neutrons as effectively as possible and which at a
  • Moderation process emitted as little gamma radiation, preferably graphite.
  • Gamma radiation that is not emitted from the sample and yet registered by the detector is defined as an active background signal.
  • the device 10 described herein advantageously provides a very weak, minimized background signal so that gamma radiation can be measured in a very flexible manner.
  • the sample 1 is located during the irradiation on a sample carrier 14 in the interior of a sample chamber 15.
  • the sample carrier may be, for example, a turntable, a box, a can or a bottle.
  • the sample carrier 14 and the sample chamber 15 are designed such that the neutrons irradiate the sample as homogeneously as possible (ie with a low local neutron flux gradient), and that neutrons which escape from the sample are effectively reflected back into the sample.
  • a possibly weak active background signal should be produced. This can be ensured in particular by using as material for the Sample carrier 14 and the sample chamber 15 preferably graphite, beryllium and fully fluorinated or carbon fiber reinforced plastics are used.
  • the gamma spectrum measured simultaneously for the irradiation is recorded by a detector unit 16 or by one or more detectors 16A, 16B.
  • a detector unit 16 can be both one and several detectors 16A, 16B.
  • Detectors are understood. Several detectors can be used to reduce the measuring time of a sample or, with the same measuring time, the sensitivity and accuracy of the multi-element analysis method can be increased.
  • the detector unit 16 registers the energy of the gamma radiation emitted from the sample and counts the energy depositions in the detector.
  • a collimator 17 is located around a respective detector 16.
  • the "field of vision" of the detectors used can be restricted in such a way that mainly gamma radiation is emitted which is emitted from the specimen
  • the space region with increased detection probability for gamma radiation points out the detector is in particular in the form of a cone or a pyramid
  • the collimator 17 is made of a material which shields gamma radiation as effectively as possible, preferably lead
  • the sample can be measured segmented / partitioned. These are located at a single
  • Field of view of the detector is for rotation and / or translation of sample and sample carrier a rotary and
  • Lifting device 18 is provided.
  • the rotary and lifting device and the sample carrier are connected to each other in particular by force and / or positive locking. Since the components of the rotating and lifting device could increase the active background signal, these assemblies are preferably outside the sample and
  • Moderation chamber 15, 12 and positioned outside the shield 19 (Fig. 5).
  • a shaft, chain or a toothed belt can be used for power transmission between the rotary and lifting device and the sample carrier 14.
  • the shield 19 is arranged around the moderation and sample chamber 12, 15 as well as around the detector unit 16 and around the collimator 17.
  • the shield 19 encloses the measuring system and reduces the neutron and gamma local dose rate outside the measuring system.
  • Shielding which primarily shields neutron radiation
  • borated polyethylene used as materials for the part of the shield which primarily reduces or attenuates gamma radiation.
  • concrete and high atomic number and high density elements such as steel or lead may be used. It has been found that borated polyethylene in the area of the moderation and sample chamber 12, 15 or around it, as well as around the detector unit 16 and around the collimator 17, can significantly improve the SNR.
  • Fig. 1 is further indicated that at the input mask 23 at least one of at least three
  • Variables / parameters vi, v2, v3 can be entered or retrieved, in particular the neutron source strength, the sample geometry, and / or the sample mass. These three parameters can also be determined fully automatically by the device 10 according to a variant.
  • a moderation in the separate moderation chamber 12 outside of the sample chamber 15 can be performed.
  • Moderation can generally be carried out in the moderation chamber 12, in the sample chamber 15 and / or in the sample 1 itself.
  • a transmission measuring unit 24 is further shown, by means of which optionally an additional
  • Characterization of a sample can be made, in particular based on gamma irradiation.
  • FIG. 1 Also indicated in FIG. 1 are components for automating the measurement or evaluation, in particular a control device 20 which is coupled to a data memory 21, to a nuclear physical database 22, to an input optical mask 23, to a transmission measuring unit 24, to a camera unit 25, to a weighing unit 27, and / or to a computer program product 30, wherein the latter can also be stored in the control device 20.
  • a control device 20 which is coupled to a data memory 21, to a nuclear physical database 22, to an input optical mask 23, to a transmission measuring unit 24, to a camera unit 25, to a weighing unit 27, and / or to a computer program product 30, wherein the latter can also be stored in the control device 20.
  • 2A, 2B, 2C show a device for non-destructive multi-element analysis, by means of which a collimated measurement of partitions of a sample takes place.
  • the two detectors 16A, 16B are arranged symmetrically relative to a neutron source or to a neutron source 11.1 of the neutron generator 11.
  • 2A, 2B, 2C show in detail also the preferably usable materials, in particular materials for ensuring a weak background signal, in particular borated polyethylene Ml (in particular 5 or 10%) for the shield 19 of neutron radiation (sometimes also concrete for the shield 19 of Gamma radiation), lead or bismuth M2 for the collimator 17 or for the purpose of shielding gamma radiation, graphite M3 for the moderation chamber 12 or the sample carrier 14 or the sample chamber 15, lithium-6-polyethylene or lithium-6-silicone M6 for a shielding of the detector , Germanium MIO for the crystal 16.1.
  • a region between individual components of the detector 16, in particular between a detector end cap 16.2 and the crystal 16.1, is filled with air M4, in particular in the interior of the collimator.
  • adequate materials M7, M8 can be selected for individual further components, in particular from the list comprising copper, aluminum, plastic (in particular
  • FIG. 2A shows by way of example two partitions P 1, P 2 of n partitions Pn in the form of cylinder segments
  • FIG. 2A also shows the orientation of the individual components according to the longitudinal axis x, the transverse axis y and the vertical axis or vertical axis z.
  • the sample is at least partially cylindrical or formed as a barrel and extends along the vertical axis z, in particular rotationally symmetrical about the z-axis. Positioning in different z-height positions is possible by means of the aforementioned lifting device 18.
  • Fig. 2B shows a variant with only one detector 16, which is collimated on a cylinder segment. This arrangement can also be provided in a cost-optimized manner. In the arrangement shown in each case in FIGS. 2A, 2B, moderation can also be carried out exclusively within the sample chamber 15.
  • Fig. 2C further shows a detector end cap 16.2 and a crystal holder 16.3, by means of which elements the crystal 16.1 can be positioned and aligned.
  • Control points R1 to R5 can be provided between the individual steps, be it for a user query or for an automatic, computer-controlled query.
  • a first step S 1 neutrons are generated and irradiation of a sample with neutrons takes place, wherein the first step may comprise at least one of the following sub-steps: setting (controlling or regulating) the neutron source intensity (Sl.1), moderation (S1.2 ), simulative calculation of the neutron spectrum (S1.3), simulative calculation of the neutron flux (S1.4).
  • an optionally repeated query can be made with regard to the neutron source intensity, be it an automated data query, be it in the context of user input / user guidance.
  • a sample specification and measurement is performed, wherein the second step may comprise at least one of the following substeps: detecting the sample mass and optionally also the
  • the step S2.1 can be carried out in conjunction with a transmission measurement, in particular by emitting radioactive gamma radiation to the sample, for example for detecting a filling level in a drum (sample), or for determining a matrix density.
  • the transmission measurement can therefore be understood as an extended measurement for characterizing the sample, and can provide further data, in particular also with regard to partitioning which is as expedient as possible.
  • an optionally repeated query regarding the sample mass, sample geometry and partitioning can take place, be it an automated data query in communication with a camera unit and / or a weighing unit, be it within the framework of a
  • a detection or measurement of emitted gamma radiation takes place, wherein the third step may comprise at least one of the following substeps: detection / measurement of gamma radiation and evaluation of the gamma spectrum (S3.1), element / peak identification (S3.2 ), Interference analysis (S3.3),
  • control point R3 in particular a transfer and ⁇ ⁇ ⁇ made of intermediate results.
  • the control point R3 include a plausibility check, in particular in the context of a statement about the homogeneous element and mass distribution in the sample or in a respective partition, optionally (for example, with a deviation greater than a maximum threshold) an iteration back to step S2 especially to measure based on a new collimated approach.
  • a fourth step S4 measured gamma radiation is evaluated, in particular for calculating the energy-dependent photopeak efficiency, wherein the fourth step may comprise at least one of the following substeps: Evaluating interactions within the sample (S4.1) to calculate the
  • a fifth step S5 the mass of at least one element is determined, wherein the fifth step may comprise at least one of the following sub-steps: determining at least one element mass or determining element mass ratios (S5.1), determining at least one cross-section (S5.2), in particular in each case either from step S 1 or step S4.
  • a transfer and checking of intermediate results can take place in a fifth control point R5.
  • the control point R5 may include a plausibility check, in particular a comparison or comparison of quantified elemental masses and the total mass of the sample.
  • a sixth step S6 the calculation of the neutron is carried out, wherein the sixth step may comprise at least one of the following sub-steps: evaluation of interactions, in particular
  • Control point Rl to R5 may each include an optional feedback (control loop) to the previous step, in particular as part of a review of a user input or a
  • the steps S4 to S6 can be carried out iteratively, independently of the individual control points, in particular continuously during the evaluation of gamma radiation from continuously irradiated samples.
  • the iteration is aborted if the element mass to be determined no longer changes, or at least no longer changes significantly, for example, from a predefinable threshold value for a difference.
  • FIG. 4 shows the field of view of a respective detector 16A, 16B using the example of a cylindrical sample 1 partitioned into slices and circle segments PI, P2, Pn.
  • the field of view of the respective detector 16A, 16B does not necessarily have to coincide with a respective partition.
  • each partition in each height position.
  • the entire sample can then be analyzed by six rotations and by the corresponding number of translational height displacement steps (in this case five levels, ie four displacement steps in the z direction).
  • Each partition is, for example, irradiated and measured over a period of a few seconds to minutes.
  • a device 10 is shown in which the sample carrier 14 in height by a considerable distance (dotted line) can be moved upwards.
  • the sample chamber 15 is delimited by material M3, which material M3 can be displaced together with the sample 1 into an air-filled cavity above the sample 1.
  • the rotating and lifting device 18 is connected by means of a coupling comprising a shaft 18.1 with the sample carrier 14, but apart from that arranged outside the neutron shield and sealed off from the sample chamber. This can ensure that the neutrons do not reach the turning and lifting device. A Wegsamkeit the neutrons to the rotating and lifting device is prevented.
  • the material in which the shaft 18.1 is guided is preferably graphite. As indicated in Fig. 5, in a graphite block a
  • the rotating and lifting device 18 is preferably connected exclusively to the sample carrier 14 by means of the shaft 18.1.
  • the neutron shield is then broken only by the wave.
  • the turning and lifting device is sealed behind the effective
  • Neutron shield arranged.
  • a device 10 for non-destructive multi-element analysis is shown, in which four
  • Neutron detectors 28A, 28B, 28C, 28D of a neutron detector unit 28 are arranged in the sample chamber 15.
  • the neutron detectors arranged here by way of example are equally distributed over the circumference of the
  • Sample chamber 15 is arranged.
  • more than four neutron detectors can be provided.
  • the neutron detectors are preferably arranged at the mounting height of the gamma detectors.
  • a location-resolved and energy-resolved determination of the neutron flux in particular of the absolute or total neutron flux of a respective partition, can take place externally of the sample.
  • Ml material 1 in particular borated polyethylene and / or concrete
  • M2 material 2 in particular lead and / or bismuth
  • M6 material 6 in particular lithium polyethylene and / or lithium silicone
  • M7 material 7 in particular aluminum and / or carbon fiber reinforced plastic
  • M8 material 8 in particular copper or plastic
  • MIO material 10 especially germanium
  • R5 fifth control point S 1 first step in particular generation of neutrons and irradiation with neutrons
  • S3 third step in particular detection of emitted gamma radiation and evaluation of measured gamma radiation

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Abstract

L'invention concerne un procédé d'analyse multi-élémentaire sur la base de l'activation neutronique, comportant les étapes suivantes : générer des neutrons rapides comportant une énergie dans la gamme de 10keV à 20MeV ; irradier un échantillon (1) desdits neutrons ; mesurer le rayonnement gamma émis par l'échantillon irradié pour déterminer au moins un élément dudit échantillon ; selon l'invention, l'irradiation de l'échantillon a lieu sans pulsation de manière continue, la mesure ayant lieu pendant l'irradiation, pour déterminer au moins un élément, au moins un rayonnement gamma prompt ou à la fois prompt et retardé est mesuré et évalué, l'échantillon étant subdivisé en partitions individuelles et la mesure étant réalisée à l'aide d'un collimateur, le flux neutronique étant déterminé par résolution spatiale et énergétique dans la partition (P1, P2, Pn) correspondante de l'échantillon (1). Cela permet d'approfondir l'analyse et d'obtenir un procédé flexible. L'invention concerne également un dispositif correspondant et l'utilisation d'une unité de détection destinée à l'analyse multi-élémentaire.
EP18729863.3A 2017-05-31 2018-05-28 Procédé et dispositif d'analyse multiélémentaire sur la de base de l'activation neutronique et utilisation Withdrawn EP3707500A1 (fr)

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EP17401060.3A EP3410104B1 (fr) 2017-05-31 2017-05-31 Procédé et dispositif d'analyse multi-élément basé sur l'activation par neutrons et utilisation
DE102017111935.3A DE102017111935B4 (de) 2017-05-31 2017-05-31 Verfahren und Vorrichtung zur Multielementanalyse basierend auf Neutronenaktivierung sowie Computerprogrammprodukt dafür
PCT/DE2018/100516 WO2018219406A1 (fr) 2017-05-31 2018-05-28 Procédé et dispositif d'analyse multiélémentaire sur la de base de l'activation neutronique et utilisation

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US20200132613A1 (en) 2020-04-30
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WO2018219406A1 (fr) 2018-12-06
RU2751586C2 (ru) 2021-07-15
KR102442077B1 (ko) 2022-09-08
JP7104780B2 (ja) 2022-07-21
CN111801571B (zh) 2023-10-17
US11408838B2 (en) 2022-08-09
RU2019143155A3 (fr) 2021-06-30
BR112019025088B1 (pt) 2023-12-19
BR112019025088A2 (pt) 2020-06-23
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CA3065628A1 (fr) 2018-12-06

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