Monte Carlo determination of the characteristic limits in measurement of ionising radiation—fundamentals and numerics
a Parkstr. 11, D-38179 Schwülper, Germany
b Johann-Heinrich-von-Thünen-Institut, Institut für Fischereiökologie, Marckmannstr. 129b, Haus 4, D-20539 Hamburg, Germany
c Zentrum für Strahlenschutz und Radioökologie, Leibniz-Universität Hannover, Herrenhäuser Str. 2, D-30419 Hannover, Germany
d Forschungszentrum Jülich, S-BP, D-52425 Jülich, Germany
e Forschungszentrum Karlsruhe, Fortbildungszentrum für Technik und Umwelt (FTU), D-76021 Karlsruhe, Germany
* Corresponding author: michel{at}zsr.uni-hannover.de
Received October 17, 2008, amended May 21, 2009, accepted May 25, 2009
It is shown how the decision threshold, the detection limit and the limits of a coverage interval — summarily called the characteristic limits — and, in addition, the best estimate and the associated standard uncertainty of a non-negative radiation measurand are to be calculated by using the Monte Carlo (MC) method in ionising-radiation measurements. The limits are mathematically defined by means of quantiles of the Bayesian distributions of the possible measurand values. The MC-induced uncertainties of the limits and typical problems connected with MC application are also treated. The paper can serve as a bridge between the ISO Guide to the Expression of Uncertainty in Measurement (GUM), Supplement 1 applying the MC method and ISO/FDIS 11929 (at present in preparation) dealing with the characteristic limits. As an illustration, a net count rate measurand, being the difference of a gross and a background count rate, is treated theoretically and numerically. More complex examples deal with the wipe test for surface contamination and with a linear multi-channel spectrum unfolding.