BS-ISO-11929-6-2005.pdf
BRITISH STANDARD BS ISO 11929-6:2005 Determination of the detection limit and decision threshold for ionizing radiation measurements Part 6: Fundamentals and applications to measurements by use of transient mode ICS 17.240 ? Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:52:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 11929-6:2005 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 23 February 2005 © BSI 23 February 2005 ISBN 0 580 45550 5 National foreword This British Standard reproduces verbatim ISO 11929-6:2005 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee NCE/2, Radiation protection and measurement, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to v, a blank page, pages 1 to 16, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:52:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Reference number ISO 11929-6:2005(E) © OSI 5002 INTERNATIONAL STANDARD ISO 11929-6 First edition 2005-02-15 Determination of the detection limit and decision threshold for ionizing radiation measurements Part 6: Fundamentals and applications to measurements by use of transient mode Détermination de la limite de détection et du seuil de décision des mesurages de rayonnements ionisants Partie 6: Principes fondamentaux et leurs applications aux mesurages réalisés en mode transitoire BS ISO 119296:2005 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:52:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS-92911 O6:(5002E) DPlcsid Fremia ihTs PDF file may ctnoian emdebt dedyfepcaes. 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The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 11929-6 was prepared by Technical Committee ISO/TC 85, Nuclear energy, Subcommittee SC 2, Radiation protection. ISO 11929 consists of the following parts, under the general title Determination of the detection limit and decision threshold for ionizing radiation measurements: Part 1: Fundamentals and application to counting measurements without the influence of sample treatment Part 2: Fundamentals and application to counting measurements with the influence of sample treatment Part 3: Fundamentals and application to counting measurements with high resolution gamma spectrometry, without the influence of sample treatment Part 4: Fundamentals and applications to measurements by use of linear-scale analogue ratemeters, without the influence of sample treatment Part 5: Fundamentals and applications to counting measurements on filters during accumulation of radioactive material Part 6: Fundamentals and applications to measurements by use of transient mode Part 7: Fundamentals and general applications Part 8: Fundamentals and applications to unfolding of spectrometric measurements without the influence of sample treatment BS ISO 119296:2005 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:52:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS-92911 O6:(5002E) I ©SO 5002 All irthgs ersedevr v Introduction This part of ISO 11929 gives basic information on the statistical principles for the determination of the detection limit and decision threshold (and directives for specification of the confidence limits) for nuclear radiation measurements. This part of ISO 11929 applies to monitoring systems for checking materials moved on vehicles, lorries, ships, in containers, on moving belts, etc. for hidden radioactivity (contamination, activation products, radioactive sources), while passing gates, borders or other check points. The purpose of the measurement is to detect suspicious goods or vehicles and to stop them for a more detailed inspection. Whereas the earlier parts 1 to 4 were elaborated for special measuring tasks in nuclear radiation measurements based on the principles defined by Altschuler and Pasternack 1, Nicholson 2, Currie 3, this restriction does not apply to this part, or to parts 5, 7 and 8. The determination of the characteristic limits mentioned above is separated from the evaluation of the measurement. Consequently, this part of ISO 11929 is generally applicable and can be applied to any suitable procedure for the evaluation of a measurement. Since the uncertainty of measurement plays a fundamental role in this part of ISO 11929, evaluations of measurements and the determination of the uncertainties of measurement have to be performed according to the Guide for the Expression of Uncertainty in Measurement. This part, as well as parts 5, 7 and 8, of ISO 11929 is based on methods of Bayesian statistics (see 4 to 6) in the Bibliography in order to be able to account also for such uncertain quantities and influences which do not behave randomly in repeated or counting measurements. For this purpose, Bayesian statistical methods are used to specify the following statistical values, called “characteristic limits”. The decision threshold, which allows a decision to be made for a measurement with a given probability of error as to whether the result of the measurement indicates the presence of the physical effect quantified by the measurand. The detection limit, which specifies the minimum true value of the measurand which can be detected with a given probability of error using the measuring procedure in question. This consequently allows a decision to be made as to whether or not a measuring method checked using this part of ISO 11929 satisfies certain requirements and is consequently suitable for the given purpose of measurement. The limits of the confidence interval, which define an interval which contains the true value of the measurand with a given probability, in the case that the result of the measurement exceeds the decision threshold. BS ISO 119296:2005 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:52:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI blank 5002:692911 OSI SB Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:52:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI INTENRATIONAL TSANDADR IS-92911 O6:(5002E) I ©SO 5002 All irthgs ersedevr 1 Determination of the detection limit and decision threshold for ionizing radiation measurements Part 6: Fundamentals and applications to measurements by use of transient mode 1 Scope This part of ISO 11929 specifies suitable statistical values which allow an assessment of the detection capabilities in ionizing radiation measurements by use of a transient mode. For this purpose, statistical methods are used to specify two statistical values characterizing given probabilities of error. This part of ISO 11929 deals with fundamentals and applications to measurements by use of transient mode. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. BIPM/IEC/IFCC/ISO/IUPAC/IUPAP/OIML, Guide to the Expression of Uncertainty in Measurement, Geneva, 1993 ISO 11929-7:2005, Determination of the detection limit and decision threshold for ionizing radiation measurements Part 7: Fundamentals and general applications 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 measuring method any logical sequence of operations, described generically, used in the performance of measurements NOTE 1 Adapted from the International Vocabulary of Basic and General Terms in Metrology:1993. NOTE 2 In this part of ISO 11929, the measuring method is the application of any radiation detection systems suitable for measuring the radiation emitted from materials while transported on vehicles, lorries, ships, moving belts or in containers, and its evaluation. 3.2 measurand particular quantity subject to measurement International Vocabulary of Basic and General Terms in Metrology:1993 BS ISO 119296:2005 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:52:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS-92911 O6:(5002E) 2 I ©SO 5002 All irthgs ersedevr NOTE In this part of ISO 11929, a measurand is non-negative and quantifies a nuclear radiation effect. The effect is not present if the value of the measurand is zero. It is a characteristic of this part of ISO 11929 that it can be applied to any measurand suitable to indicate radioactivity of the materials investigated. 3.3 uncertainty (of measurement) parameter, associated with the result of a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurand Guide for the Expression of Uncertainty in Measurement:1993 NOTE The uncertainty of a measurement derived according to the ISO Guide for the Expression of Uncertainty in Measurement comprises, in general, many components. Some of these components may be evaluated from the statistical distribution of the results of series of measurements and can be characterized by experimental standard deviations. The other components, which also can be characterized by standard deviations, are evaluated from assumed or known probability distributions based on experience and other information. 3.4 mathematical model of the evaluation a set of mathematical relationships between all measured and other quantities involved in the evaluation of measurements 3.5 decision quantity random variable for the decision whether the physical effect to be measured is present or not 3.6 decision threshold fixed value of the decision quantity by which, when exceeded by the result of an actual measurement of a measurand quantifying a physical effect, one decides that the physical effect is present NOTE The decision threshold is the critical value of a statistical test to decide between the hypothesis that the physical effect is not present and the alternative hypothesis that it is present. When the critical value is exceeded by the result of an actual measurement, this is taken to indicate that the hypothesis should be rejected. The statistical test will be designed such that the probability of wrongly
