EP1256018A1 - Assembly and method for measuring ionising radiation with background noise correction - Google Patents

Assembly and method for measuring ionising radiation with background noise correction

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Publication number
EP1256018A1
EP1256018A1 EP01907808A EP01907808A EP1256018A1 EP 1256018 A1 EP1256018 A1 EP 1256018A1 EP 01907808 A EP01907808 A EP 01907808A EP 01907808 A EP01907808 A EP 01907808A EP 1256018 A1 EP1256018 A1 EP 1256018A1
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EP
European Patent Office
Prior art keywords
radiation
measurement
measuring
detector
source
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Withdrawn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
EP01907808A
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German (de)
French (fr)
Inventor
Jean-François PINEAU
Michel Janot
Nicolas Vandeven
Philippe Eydoux
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.)
Societe Auxiliaire du Tricastin SARL SOCRATI
Original Assignee
Societe Auxiliaire du Tricastin SARL SOCRATI
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Application filed by Societe Auxiliaire du Tricastin SARL SOCRATI filed Critical Societe Auxiliaire du Tricastin SARL SOCRATI
Publication of EP1256018A1 publication Critical patent/EP1256018A1/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/167—Measuring radioactive content of objects, e.g. contamination
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T7/00—Details of radiation-measuring instruments

Definitions

  • the field of this invention is the measurement of ionizing radiation emitted by a source, and here we are concerned with correcting the measurement by overcoming the influence of background noise.
  • the term “detector” has a broad meaning and can be translated in reality by a set of several detection sets. Attempts have already been made to avoid the effect of the background noise produced by this surrounding radioactivity. It is therefore common for the main detector, responsible for measuring the radiation from the source, to be supplemented by an auxiliary detector specifically responsible for measuring background noise. When it detects background noise of a level deemed to be excessive, the measurement of the radiation from the source is not undertaken and we can wait for more favorable circumstances for the which, however, is not convenient.
  • the auxiliary detector completely envelops the main detector and the source when it is present: it then measures the ambient radiation originating from all directions in a uniform manner, but it does not prevent part of the ambient radiation to cross it and reach the main detector, which further falsifies the measurement.
  • This radiation can be transmitted directly or after having been diffused and affected by the Compton effect, that is to say supplied at a different energy, which makes it difficult to evaluate according to the part of the radiation that the auxiliary detector has stopped.
  • auxiliary detector is also sensitive to radiation originating from the source, transmitted directly or after passing through the main detector, it can be understood that these correction calculations are difficult to apply and require a complicated electronic operating system (anti-Compton devices) .
  • the object of the invention is therefore to correct the influence of background noise, in the particular case of ionizing radiation measurements where it is very difficult to distinguish the influence of the various origins of the radiation, by means of a set detection and a process each improved.
  • the invention consists in correcting the measurements of the main detector, responsible for evaluating the radiation from the source, estimating the background noise it records and subtracting it from these measurements; it relates to a unit for measuring ionizing radiation, comprising a main detector responsible for measuring radiation emitted by a determined source and an auxiliary detector responsible for measuring ambient radiation, characterized in that it comprises means for correlating the measurements made by the two detectors and the correction of the measurements made by the primary detector as a function of the results of the correlation; as well as a method for measuring ionizing radiation, comprising a main measurement of a main radiation emitted by a determined source and an auxiliary measurement of ambient radiation, as well as corrections of the main measurement as a function of the auxiliary measurement, characterized in that the main measurement begins before bringing the source and is compared with the auxiliary measurement to obtain a correlation, and in that, when the source has been brought, the main measurement is corrected according to the correlation and simultaneous auxiliary measurement.
  • Figure 1 is a schematic view of the detection assembly
  • Figures 2 and 3 are graphs of raw and corrected measurements.
  • the whole of the invention which in a particular form can constitute an assembly called a portal for detection in specialized language, is in this case intended primarily to measure the activity of radioactive objects of various natures which pass in front of it. It comprises at least one main detector or measurement detector 1 responsible for measuring the activity of an irradiating source, and at least one auxiliary detector or guard detector 2 responsible for measuring the ambient radiation responsible for the background noise.
  • Detectors 1 and 2 can be placed side by side at a greater or lesser distance from each other, or possibly, what is shown here, on either side of a location 3 occupied the source S.
  • the source S is any object, of undetermined size and often of low activity in practice, such as the loading of a truck, a concrete block, a barrel of waste, etc.
  • Detectors 1 and 2 which are only shown here, conventionally include a number of radiation detectors which receive ionizing radiation and convert it into electrical signals.
  • the measurement detector 1 is of course sensitive to radiation from location 3, while the guard detector 2 can be made sensitive to radiation from all directions except location 3, from which it is separated by a shielding 4. These conditions are general enough for a large number of arrangements of detectors 1 and 2 to be possible.
  • the application of the invention is not limited to gamma radiation, but is also possible for other types of radiation: alpha, beta, and X, in particular configurations of the main detector and the auxiliary detector.
  • the work required of the detection unit generally includes relatively short measurement periods separated by much longer periods of inactivity and which can reach several hours. However, these periods of inactivity are used to make measurements of ambient radioactivity.
  • the measured values alo-r-s by the two detectors 1 and 2 are recorded separately and compared.
  • the inventors made the important observation that the measurements were correlated with one another and could therefore be deduced from each other by a regression operation.
  • the counters 5 and 6 to which the detectors 1 and 2 are respectively connected and which serve to simultaneously record their measurements are read by a computer 7 which calculates the coefficients of the correlation curve, which in practice is sufficiently approximated by a straight line.
  • the guard detector 2 continues to measure the ambient radiation.
  • the computer 7 deduces therefrom the effect of this radiation on the measurement detector 1, that is to say the intensity of the background noise which it must restore and subtracts it from the total provided by the counter 5 to obtain the value of the radiation from source S. The results currently obtained have demonstrated the validity of the process.
  • FIG. 2 shows, in addition to the corap-tage rates g and m for acquisition periods T of 10 min, measurements m X ⁇ , m x and m x3 carried out in a measurement period P3 with three successive sources.
  • Line L is the detection limit, below which it is estimated that radiation can no longer be measured properly: “reduced” noise is still below this limit and the results appear suitable even for the third source, whose activity is barely above this limit.
  • the invention does not only facilitate the detection of radiation, but also its measurement; it can therefore be applied to devices other than detection gates.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Molecular Biology (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Measurement Of Radiation (AREA)

Abstract

The invention concerns a method which consists in deducting the noise originating from ambient radiation from the measurement of a radiation from a source (S) by a preliminary correlation calculated between the measurements of the main sensor (1) and of at least an auxiliary sensor (2): when the radiation source (S) is present, the auxiliary sensor (2) which continues to measure ambient radiation, is used to estimate the part of the measurement of the main sensor (1) which can be attributed to ambient radiation. The invention is useful for verifying the activity of various objects, often having low emissivity.

Description

ENSEMBLE ET PROCÉDÉ DE MESURE DE RAYONNEMENT IONISANT AVEC CORRECTION DE BRUIT DE FOND ASSEMBLY AND METHOD FOR MEASURING IONIZING RADIATION WITH CORRECTION OF BACKGROUND NOISE
DESCRIPTIONDESCRIPTION
Le domaine de cette invention est la mesure du rayonnement ionisant émis par une source, et on se préoccupe ici de corriger la mesure en s ' affranchissant de l'influence du bruit de fond.The field of this invention is the measurement of ionizing radiation emitted by a source, and here we are concerned with correcting the measurement by overcoming the influence of background noise.
Les spécialistes n'ignorent pas que le rayonnement nucléaire d'origine naturelle, originaire du cosmos, du sol ou du radon présent dans l'atmosphère n'est pas négligeable et peut affecter fortement la mesure du rayonnement d'une source de faible activité. Une autre cause d'erreur de la mesure provient de sources supplémentaires qui peuvent s'approcher de manière imprévue.Specialists are aware that nuclear radiation of natural origin, originating from the cosmos, soil or radon present in the atmosphere is not negligible and can greatly affect the measurement of radiation from a source of low activity. Another cause of measurement error comes from additional sources which may approach unexpectedly.
Dans le texte qui suit, le terme « détecteur » s'entend au sens large et peut se traduire dans la réalité par un ensemble de plusieurs ensembles de détection. Des tentatives ont déjà été entreprises pour ne pas subir l'effet du bruit de fond produit par cette radio-activité environnante. Il est ainsi fréquent que le détecteur principal, chargé de mesurer le rayonnement de la source, soit complété par un détecteur auxiliaire spécifiquement chargé de la mesure du bruit de fond. Quand il détecte un bruit de fond d'un niveau jugé comme excessif, la mesure du rayonnement de la source n'est pas entreprise et on peut attendre des circonstances plus propices pour la faire, ce qui n'est cependant pas commode. Dans une conception perfectionnée de ce genre, le détecteur auxiliaire enveloppe complètement le détecteur principal et la source quand elle est présente : il mesure alors le rayonnement ambiant originaire de toutes les directions de manière uniforme, mais il n'empêche pas une partie du rayonnement ambiant de le traverser et d'atteindre le détecteur principal, ce qui fausse encore la mesure. Ce rayonnement peut être transmis directement ou après avoir été diffusé et aff-ecté par l'effet Compton, c'est-à-dire fourni à une énergie différente, ce qui le rend difficile à évaluer d'après la partie du rayonnement que le détecteur auxiliaire a arrêtée. On procède en utilisant diverses discriminations spatiales et temporelles des rayonnements en fonction de leurs directions respectives estimées et de leurs instants d'arrivée sur les détecteurs. Comme le détecteur auxiliaire est aussi sensible au rayonnement originaire de la source, transmis directement ou après avoir traversé le détecteur principal, on conçoit que ces calculs de correction soient difficiles à appliquer et nécessitent un système électronique d'exploitation compliqué (dispositifs anti-Compton) . L'objet de l'invention est donc de corriger l'influence du bruit de fond, dans le cas particulier des mesures de rayonnement ionisant où il est très difficile de distinguer l'influence des diverses origines du rayonnement, au moyen d'un ensemble de détection et d'un procédé chacun perfectionnés. Pour résumer, l'invention consiste à corriger les mesures du détecteur principal, chargé d'évaluer le rayonnement de la source, en estimant le bruit de fond qu'il enregistre et en le soustrayant de ces mesures ; elle concerne un ensemble de mesure de rayonnement ionisant, comprenant un détecteur principal chargé de mesurer un rayonnement émis par une source déterminée et un détecteur auxiliaire chargé de mesurer un rayonnement ambiant, caractérisé en ce qu'il comprend des moyens de corrélation des mesures faites par les deux détecteurs et de correction des mesures faites par le détecteur primcipal en fonction de résultats de la corrélation ; ainsi qu'un procédé de mesure de rayonnement ionisant, comprenant une mesure principale d'un rayonnement principal émis par une source déterminée et une mesure auxiliaire d'un rayonnement ambiant, ainsi que des corrections de la mesure principale en fonction de la mesure auxiliaire, caractérisé en ce que la mesure principale commence avant d'apporter la source et est comparée à la mesure auxiliaire pour obtenir une corrélation, et en ce que, lorsque la source a été apportée, la mesure principale est corrigée en fonction de la corrélation et de la mesure auxiliaire simultanée .In the text which follows, the term “detector” has a broad meaning and can be translated in reality by a set of several detection sets. Attempts have already been made to avoid the effect of the background noise produced by this surrounding radioactivity. It is therefore common for the main detector, responsible for measuring the radiation from the source, to be supplemented by an auxiliary detector specifically responsible for measuring background noise. When it detects background noise of a level deemed to be excessive, the measurement of the radiation from the source is not undertaken and we can wait for more favorable circumstances for the which, however, is not convenient. In an advanced design of this kind, the auxiliary detector completely envelops the main detector and the source when it is present: it then measures the ambient radiation originating from all directions in a uniform manner, but it does not prevent part of the ambient radiation to cross it and reach the main detector, which further falsifies the measurement. This radiation can be transmitted directly or after having been diffused and affected by the Compton effect, that is to say supplied at a different energy, which makes it difficult to evaluate according to the part of the radiation that the auxiliary detector has stopped. One proceeds by using various spatial and temporal discriminations of the radiation as a function of their respective estimated directions and of their arrival times on the detectors. As the auxiliary detector is also sensitive to radiation originating from the source, transmitted directly or after passing through the main detector, it can be understood that these correction calculations are difficult to apply and require a complicated electronic operating system (anti-Compton devices) . The object of the invention is therefore to correct the influence of background noise, in the particular case of ionizing radiation measurements where it is very difficult to distinguish the influence of the various origins of the radiation, by means of a set detection and a process each improved. To summarize, the invention consists in correcting the measurements of the main detector, responsible for evaluating the radiation from the source, estimating the background noise it records and subtracting it from these measurements; it relates to a unit for measuring ionizing radiation, comprising a main detector responsible for measuring radiation emitted by a determined source and an auxiliary detector responsible for measuring ambient radiation, characterized in that it comprises means for correlating the measurements made by the two detectors and the correction of the measurements made by the primary detector as a function of the results of the correlation; as well as a method for measuring ionizing radiation, comprising a main measurement of a main radiation emitted by a determined source and an auxiliary measurement of ambient radiation, as well as corrections of the main measurement as a function of the auxiliary measurement, characterized in that the main measurement begins before bringing the source and is compared with the auxiliary measurement to obtain a correlation, and in that, when the source has been brought, the main measurement is corrected according to the correlation and simultaneous auxiliary measurement.
Ces caractéristiques et avantages ressortiront plus clairement de la description détaillée de l'invention qui suit en référence aux figures suivantes :These characteristics and advantages will emerge more clearly from the detailed description of the invention which follows with reference to the following figures:
• la figure 1 est une vue schématique de l'ensemble de détection, " et les figures 2 et 3 sont des graphiques de mesures brutes et corrigées. L'ensemble de l'invention, qui sous une forme particulière peut constituer un ensemble appelé portique de détection en langage spécialisé, est dans ce cas destiné avant tout à mesurer l'activité d'objets radioactifs de diverses natures qui passent devant lui. Il comprend au moins un détecteur principal ou détecteur de mesure 1 chargé de mesurer l'activité d'une source irradiante, et au moins un détecteur auxiliaire ou détecteur de garde 2 chargé de mesurer le rayonnement ambiant responsable du bruit de fond. Les détecteurs 1 et 2 peuvent être placés côte à côte à une distance plus ou moins importante l'un de l'autre, ou éventuellement, ce qu'on représente ici, de part et d'autre d'un emplacement 3 qu'occupe la source S. La source S est un objet quelconque, de taille indéterminée et souvent de faible activité en pratique, tel que le chargement d'un camion, un bloc de béton, un fût de déchets, etc. Les détecteurs 1 et 2 , qui ne sont que figurés ici, comprennent classiquement un certain nombre de détecteurs de rayonnement qui reçoivent les rayonnements ionisants et les convertissent en signaux électriques. Le détecteur de mesure 1 est bien entendu sensible aux rayonnements provenant de l'emplacement 3, alors que le détecteur de garde 2 peut être rendu sensible aux rayonnements provenant de toutes les directions, sauf de l'emplacement 3, dont il est séparé par un blindage 4. Ces conditions sont assez générales pour qu'un grand nombre de dispositions des détecteurs 1 et 2 soit possible. En particulier, l'application de l'invention ne se limite pas aux rayonnements gamma, mais est aussi envisageable pour les autres types de rayonnements : alpha, beta, et X, dans des configurations particulières du détecteur principal et du détecteur auxiliaire.• Figure 1 is a schematic view of the detection assembly, "and Figures 2 and 3 are graphs of raw and corrected measurements. The whole of the invention, which in a particular form can constitute an assembly called a portal for detection in specialized language, is in this case intended primarily to measure the activity of radioactive objects of various natures which pass in front of it. It comprises at least one main detector or measurement detector 1 responsible for measuring the activity of an irradiating source, and at least one auxiliary detector or guard detector 2 responsible for measuring the ambient radiation responsible for the background noise. Detectors 1 and 2 can be placed side by side at a greater or lesser distance from each other, or possibly, what is shown here, on either side of a location 3 occupied the source S. The source S is any object, of undetermined size and often of low activity in practice, such as the loading of a truck, a concrete block, a barrel of waste, etc. Detectors 1 and 2, which are only shown here, conventionally include a number of radiation detectors which receive ionizing radiation and convert it into electrical signals. The measurement detector 1 is of course sensitive to radiation from location 3, while the guard detector 2 can be made sensitive to radiation from all directions except location 3, from which it is separated by a shielding 4. These conditions are general enough for a large number of arrangements of detectors 1 and 2 to be possible. In particular, the application of the invention is not limited to gamma radiation, but is also possible for other types of radiation: alpha, beta, and X, in particular configurations of the main detector and the auxiliary detector.
Le travail demandé à l'ensemble de détection comprend en général des périodes de mesure relativement brèves séparées par des périodes d'inactivité beaucoup plus longues et qui peuvent atteindre plusieurs heures. Ces périodes d'inactivité sont pourtant mises à profit pour effectuer des mesures de la radioactivité ambiante. Les valeurs mesurées alo-r-s par les deux détecteurs 1 et 2 sont enregistrées séparément et comparées. Les inventeurs ont fait la constatation importante que les mesures étaient corrélées entre elles et pouvaient donc se déduire l'une de l'autre par une opération de régression. Ainsi, les compteurs 5 et 6 auxquels les détecteurs 1 et 2 sont respectivement reliés et qui servent à enregistrer simultanément leurs mesures sont lus par un ordinateur 7 qui calcule les coefficients de la courbe de corrélation, qui en pratique est suffisamment approchée par une droite.The work required of the detection unit generally includes relatively short measurement periods separated by much longer periods of inactivity and which can reach several hours. However, these periods of inactivity are used to make measurements of ambient radioactivity. The measured values alo-r-s by the two detectors 1 and 2 are recorded separately and compared. The inventors made the important observation that the measurements were correlated with one another and could therefore be deduced from each other by a regression operation. Thus, the counters 5 and 6 to which the detectors 1 and 2 are respectively connected and which serve to simultaneously record their measurements are read by a computer 7 which calculates the coefficients of the correlation curve, which in practice is sufficiently approximated by a straight line.
Quand une source de radioactivité arrive à l'emplacement 3 et que le détecteur de mesure 1 évalue le rayonnement qu'elle émet, le détecteur de garde 2 continue de mesurer le rayonnement ambiant. L'ordinateur 7 en déduit l'effet de ce rayonnement sur le détecteur de mesure 1, c'est-à-dire l'intensité du bruit de fond qu'il doit restituer et la soustrait du total fourni par le compteur 5 pour obtenir la valeur du rayonnement de la source S. Les résultats actuellement obtenus ont démontré la validité du procédé .When a source of radioactivity arrives at location 3 and the measurement detector 1 assesses the radiation it emits, the guard detector 2 continues to measure the ambient radiation. The computer 7 deduces therefrom the effect of this radiation on the measurement detector 1, that is to say the intensity of the background noise which it must restore and subtracts it from the total provided by the counter 5 to obtain the value of the radiation from source S. The results currently obtained have demonstrated the validity of the process.
Quelques précautions doivent pourtant être prises pour s'assurer de la validité de la corrélation. En particulier, les coefficients de régression varient quelque peu avec le temps, si bien qu'il convient de n'exploiter que des mesures suffisamment récentes et de renouveler périodiquement les calculs de corrélation. De plus, toutes les mesures ne sont pas utiles au même degré : l'étude de l'évolution des bruits de fond montre qu'il existe de longues périodes pendant lesquelles il reste à peu près constant et n'évolue que faiblement, et sans corrélation entre les mesures des deux détecteurs. C'est pourquoi de telles périodes de fluctuations de la mesure devraient être exclues au profit de celles qui voient les valeurs de mesure varier continuellement dans une même direction à une vitesse suffisante. Une période de mesure propice aux calculs de corrélation est notée par PI à la figure 2, une période de fluctuations faibles par P2.However, some precautions must be taken to ensure the validity of the correlation. In particular, the regression coefficients vary somewhat over time, so that only sufficiently recent measurements should be used and the correlation calculations should be repeated periodically. In addition, not all measurements are useful to the same degree: the study of the evolution of background noises shows that there are long periods during which it remains roughly constant and evolves only slightly, and without correlation between the measurements of the two detectors. This is why such periods of measurement fluctuations should be excluded in favor of those which see the measurement values continuously varying in the same direction at a sufficient speed. A measurement period conducive to correlation calculations is denoted by PI in Figure 2, a period of small fluctuations by P2.
Si donc les valeurs de comptage des détecteurs de mesure 1 et de garde 2 sont M et G pendant une durée d'acquisition T fixée, les taux deIf therefore the count values of measurement detectors 1 and guard 2 are M and G during a fixed acquisition time T, the rates of
M G comptage sont calcules par m = — et g = — . Si laM G counts are calculated by m = - and g = -. If the
T T corrélation est linéaire, on pourra écrire m'=p.g+q, où p et q sont les coefficients de la droite de corrélation et m' un taux de comptage restitué pour le détecteur de mesure 1.T T correlation is linear, we can write m '= p.g + q, where p and q are the coefficients of the correlation line and m' a counting rate restored for the measurement detector 1.
Pendant les périodes de mesure, le taux de comptage du détecteur de mesure 1 sera appelé mx et celui du détecteur de garde 2 restera appelé g puisque ce détecteur est blindé vers l'emplacement 3 de la source et reste donc sensible aux mêmes phénomènes qu'auparavant. Le rayonnement de la source sera évalué d'après le taux de comptage corrigé (mx-m' ) . Il est manifeste que d'autres corrélations que linéaires peuvent être envisagées et exploitées de la même façon, et que certaines hypothèses peuvent faciliter l'obtention des résultats : le coefficient q sera ainsi égal à zéro dans bon nombre de situation pratique. La figure 2 montre, outre les taux de corap-tage g et m pour des périodes d'acquisition T de 10 mn, des mesures mXι, mx et mx3 conduites dans une période de mesure P3 avec trois sources successives. Ces mesures furent fortement affectées par une augmentation notable du bruit de fond, la courbe du taux de comptage du détecteur de garde g ayant atteint un maximum qu'on retrouve sur la courbe du bruit de fond estimé m' pour le détecteur de mesure 1. L'application de l'invention conduit aux résultats de la figure 3, où on donne les taux de comptage corrigés (mxι-m' ) , (mx2-m' ) et (mx3-m' ) et le bruit de fond « réduit » par la corrélation et égal à (m-m' ) . Celui- ci est de beaucoup plus faible que m, alors que les taux de comptage corrigés sont plus cohérents que les taux bruts mxχ, mx2 et mx3 pour chacune des sources, et certainement proches des valeurs idéales qu'on aurait dû trouver, quoique le bruit de fond ait été considérable ici, plus de 20 fois la valeur du signal. La ligne L est la limite de détection, au-dessous de laquelle on estime qu'on ne peut plus mesurer un rayonnement convenablement : le bruit « réduit » est toujours sous cette limite et les résultats paraissent convenables même pour la troisième source, dont l'activité est à peine supérieure à cette limite.During the measurement periods, the counting rate of the measurement detector 1 will be called m x and that of the guard detector 2 will remain called g since this detector is shielded towards location 3 of the source and therefore remains sensitive to the same phenomena as before. The radiation of the source will be evaluated according to the corrected counting rate (m x -m '). It is obvious that correlations other than linear can be envisaged and exploited in the same way, and that certain assumptions can facilitate the obtaining of the results: the coefficient q will thus be equal to zero in many practical situations. FIG. 2 shows, in addition to the corap-tage rates g and m for acquisition periods T of 10 min, measurements m X ι, m x and m x3 carried out in a measurement period P3 with three successive sources. These measurements were strongly affected by a notable increase in the background noise, the curve of the counting rate of the guard detector g having reached a maximum which is found on the curve of the estimated background noise m 'for the measurement detector 1. The application of the invention leads to the results of FIG. 3, where we give the corrected counting rates (m x ι-m '), (m x2 -m') and (m x3 -m ') and the noise "reduced" by the correlation and equal to (mm '). This is much lower than m, while the corrected count rates are more consistent than the raw rates m x χ, m x2 and m x3 for each of the sources, and certainly close to the ideal values that should have been find, although the background noise was considerable here, more than 20 times the signal value. Line L is the detection limit, below which it is estimated that radiation can no longer be measured properly: “reduced” noise is still below this limit and the results appear suitable even for the third source, whose activity is barely above this limit.
Un avantage important est donc que la gamme d'intensité de rayonnement dont la détection est rendue possible est beaucoup plus grande.An important advantage is therefore that the range of radiation intensity whose detection is made possible is much greater.
Enfin, l'invention ne facilite pas seulement la détection d'un rayonnement, mais aussi sa mesure ; elle peut donc être appliquée à d'autres appareils que les portiques de détection. Finally, the invention does not only facilitate the detection of radiation, but also its measurement; it can therefore be applied to devices other than detection gates.

Claims

REVENDICATIONS
1. Ensemble de mesure de rayonnement ionisant, comprenant au moins un détecteur principal ( 1 ) chargé de mesurer un rayonnement émis par une source (S) déterminée et au moins un détecteur auxiliaire (2) chargé de mesurer un rayonnement ambiant, caractérisé en ce qu'il comprend des moyens (7) de corrélation de mesures faites par les deux détecteurs et de correction de mesures faites par le détecteur principal en fonction de résultats de la corrélation .1. Assembly for measuring ionizing radiation, comprising at least one main detector (1) responsible for measuring radiation emitted by a determined source (S) and at least one auxiliary detector (2) responsible for measuring ambient radiation, characterized in that that it comprises means (7) for correlating measurements made by the two detectors and for correcting measurements made by the main detector as a function of the results of the correlation.
2. Ensemble de mesure de rayonnement ionisant selon la revendication 1, caractérisé en ce que les détecteurs sont disposés de part et d'autre d'un emplacement (3) destiné à la source ou côte à côte près de cet emplacement, le détecteur auxiliaire (2) étant blindé (4) vers cet emplacement.2. ionizing radiation measuring assembly according to claim 1, characterized in that the detectors are arranged on either side of a location (3) intended for the source or side by side near this location, the auxiliary detector (2) being shielded (4) towards this location.
3. Procédé de mesure de rayonnement ionisant, comprenant une mesure principale d'un rayonnement principal (m) émis par une source (S) déterminée et une mesure auxiliaire (g) d'un rayonnement ambiant, ainsi que des corrections de la mesure principale en fonction de la mesure auxiliaire, caractérisé en ce que la mesure principale commence avant d'apporter la source et est comparée à la mesure auxiliaire pour obtenir une corrélation, et en ce que, lorsque la source a été apportée, la mesure principale est corrigée en fonction de la corrélation et de la mesure auxiliaire simultanée. 3. Method for measuring ionizing radiation, comprising a main measurement of a main radiation (m) emitted by a determined source (S) and an auxiliary measurement (g) of ambient radiation, as well as corrections of the main measurement as a function of the auxiliary measurement, characterized in that the main measurement begins before bringing the source and is compared with the auxiliary measurement to obtain a correlation, and in that, when the source has been brought, the main measurement is corrected depending on the correlation and the simultaneous auxiliary measurement.
4. Procédé de mesure de rayonnement ionisant selon la revendication 3, caractérisé en ce que les mesures sont comparées à une série d'instants plus récents qu'un laps de temps déterminé.4. A method of measuring ionizing radiation according to claim 3, characterized in that that the measurements are compared to a series of times more recent than a specified period of time.
5. Procédé de mesure de rayonnement ionisant selon la revendication 3, caractérisé en ce que les mesures sont comparées pendant des périodes de variation continue des mesures. 5. A method of measuring ionizing radiation according to claim 3, characterized in that the measurements are compared during periods of continuous variation of the measurements.
EP01907808A 2000-02-16 2001-02-15 Assembly and method for measuring ionising radiation with background noise correction Withdrawn EP1256018A1 (en)

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FR0001900 2000-02-16
FR0001900A FR2805048B1 (en) 2000-02-16 2000-02-16 ASSEMBLY AND METHOD FOR MEASURING IONIZING RADIATION WITH CORRECTION OF BACKGROUND NOISE
PCT/FR2001/000448 WO2001061378A1 (en) 2000-02-16 2001-02-15 Assembly and method for measuring ionising radiation with background noise correction

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EP2771718B1 (en) * 2011-10-27 2019-09-11 Atomic Energy of Canada Limited/ Énergie Atomique du Canada Limitée Portable detection apparatus and method
FR3011340B1 (en) * 2013-10-01 2017-01-06 Commissariat Energie Atomique SYSTEM FOR MEASURING RADIOACTIVITY IN A GAMMA BACKGROUND NOISE
FR3086764B1 (en) * 2018-09-27 2020-12-25 Commissariat Energie Atomique SPECTROMETRY SYSTEM, SPECTROMETRY PROCESS AND ASSOCIATED COMPUTER PROGRAM PRODUCT

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WO2001061378A1 (en) 2001-08-23

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