DIN ISO 11929-4:2021-06: determination of the characteristic limits (decision threshold, detection limit and limits of the coverage interval) for measurements of ionizing radiation - fundamentals and application - Pt. 4: guideline to applications (ISO 11929-4:2020)

Measurement uncertainties and characteristic limits, i.e. characteristic limits such as the detection limit, the detection limit and the limits of the coverage interval as well as the best estimate and its associated standard uncertainty) are of particular importance in metrology in general and in radiation protection. - DIN ISO 11929-1 deals with elementary applications of counting measurements as they frequently occur in the field of metrology of ionising radiation; - DIN ISO 11929-2 extends DIN ISO 11929-1 to the evaluation of measurements where the measurement uncertainties are determined according to ISO/IEC Guide 98-3:2008/Supplement 1. ISO 11929-2 also contains explanations on general aspects of counting measurements and on the application of Bayes statistics to measurements; - ISO 11929-3 covers the evaluation of measurements using deconvolution methods and counting multichannel measurements insofar as they are evaluated using deconvolution methods, in particular alpha and gamma spectrometric measurements. In addition, DIN ISO 11929-3 gives instructions on how to proceed with correlations and covariances. After a brief description of the procedure, DIN ISO 11929-4 provides instructions for the application of ISO 11929 with a total of 13 numerical examples. The quantification of the uncertainty that can be assigned to a measurement result represents a basis for the confidence that an individual can place in the measurement result. ISO 11929 addresses the characteristic limits for a non-negative measurand in the measurement of ionising radiation. However, it is applicable to a wide range of measurement methods that go far beyond the measurement of ionising radiation: - the simple model of a counting measurement with low or moderate relative uncertainties used in the vast majority of laboratory measurements; - an example of the measurement of alpha particles with few counting events; - a counting measurement with uncertain measurement geometry where the uncertainties of the calibration factor are large and, as a consequence, a dominant uncertainty occurs in the numerator of the calibration factor; - a counting measurement in the form of a wipe test, where the uncertainties are generally large and a dominating uncertainty occurs in the denominator of the calibration factor; - a measurement where large uncertainties occur as a consequence of screening of the zero effect, as is the case, for example, in measurements with a gantry monitor; - a clearance measurement of a composite sample of concrete with a special measuring device, taking into account the natural radioactivity of the sample in the zero effect deduction; - the general model for gamma spectrometry of U-235 taking into account an interference of Ra-226; - a measurement of an ambient dose equivalent rate with a measurement set-up of unknown functionality and algorithms, i.e. a so-called black box measurement where no information on the measurement procedure is available and only the readings of a display are available; - the case of counting measurements with random influences of the sample treatment; - a counting measurement with known influence of the sample treatment procedure; - the case of an active personal dosimeter where the standard uncertainty associated with the gross quantity is constant and thus allows the calculation of the standard uncertainty as a function of the true value of the measurand; - a measurement of the dose rate with a neutron site dosimeter where the actual counts of the gross and background measurements are unknown; - a simple example for the calculation of the calibration factor.