DKE German Commission for Electrical, Electronic & Information Technologies of DIN and VDE
DIN ISO 11929 Beiblatt 1
Determination of the characteristic limits (decision threshold, detection limit and limits of the confidence interval) for measurements of ionizing radiation - Fundamentals and application; Supplement 1: Examples
Bestimmung der charakteristischen Grenzen (Erkennungsgrenze, Nachweisgrenze und Grenzen des Vertrauensbereichs) bei Messungen ionisierender Strahlung - Grundlagen und Anwendungen; Beiblatt 1: Beispiele
Overview
DIN ISO 11929:2011-01 describes the procedures to be used for determining the characteristic limits (decision threshold, detection limit and limits of confidence interval) for measurements of ionizing radiation. The standard is based on Bayesian statistics. This means that its application allows the consideration of both standard uncertainties of measurement as wells as quantities and influences which do not behave randomly during measurements repeated several times or during counting measurements. Due to their particular national importance, applications during measurements with albedo dosimeters have already been addressed in National Annex NC of DIN ISO 11929. The application of the standard indicated the need of describing further typical examples on the basis of which the user can easily understand the procedures to be applied. This supplement complies with this need. The examples start with simple measuring tasks which illustrate the general approach. The complexity of the examples increases with advancing numbering of the clauses. They cover counting measurements with and without calibration, measurements of environmental radioactivity, excretion analytics and monitoring of radioactivity in exhaust air. Finally, the rather academic issue of radiometric potassium determination is addressed since it represents an easily displayable example for the application of adjustment calculations and the employment of matrix notations. Each example is divided into 13 subclauses which can be used in practice as a general process scheme. In each case, the first six subclauses provide an introduction and a task, followed by the introduction of the model of evaluation, the preparation of input data and specifications, the background measurement and the calculation of the primary measurement result and its associated standard uncertainty. The evaluation of measurements and the treatment of standard uncertainties are performed in compliance with the general method according to ISO/IEC Guide 98-3:2008, Uncertainty of measurement - Part 3: Guide to the expression of uncertainty in measurement (in short, GUM). This allows the separation into the evaluation of measurements on the one hand and the specification and calculation of characteristic limits on the other hand. The responsible committee is Joint Subcommittee GUK 967.2 "Aktivitätsmessgeräte für den Strahlenschutz" ("Activity meters for radiation protection") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE, Joint Committee with the Radiology Standards Committee (NAR) at DIN. The supplement has been prepared by Joint Working Group GAK 967.2.1 "Nachweis- und Erkennungsgrenzen bei Kernstrahlungsmessungen" ("Detection limits and decision thresholds in nuclear radiation measurements") which, at the same time, acts as Working Group AK SIGMA of the Radiation Protection Association.
