Weighing uncertainties in quantitative source preparation for radionuclide metrology

Abstract

In radionuclide metrology, the assessment of activity concentrations is directly related to the mass determination in quantitative source preparation. As far as primary measurements are concerned, the associated weighing uncertainty has a non-negligible contribution in the uncertainty budget. Several parameters influencing the mass determination have to be considered in source preparation and for the evaluation of the weighing uncertainty: technical specifications of calibrated balances, environmental quantities such as air buoyancy and other disturbance sources like electrostatic effects. The accuracy of mass determination is also conditioned by good practices in source preparation. This article reviews the different parameters in the evaluation of the weighing uncertainty. Its aim is also to give some guidance on how to achieve the smallest uncertainty.

Methodology for preparing a reference sample in the air filter matrix

“…The cocktails were prepared gravimetrically by differential weighing, using the pycnometer method [8] and [9] on a Mettler Toledo model XP-56 micro-analytical balance. The activities of each cocktail and their associated uncertainties are described in…”

“…Cocktails were added to each filter gravimetrically by differential weighing using the pycnometer method [8] and [9] on a Mettler Toledo model AX-205. Each cocktail was distributed in three filters with 19 (nineteen) drops (each drop with approximate mass of 0.01g), totaling about 0.190g of the solution in each filter, using a pantograph, as shown in figure 3, where the geometry used for Deposition of each drop of solution is shown in Figure 2.…”

Standardisation of 241Am activity for a key comparison

“…This led to the second largest uncertainty component of 0.06%. The third significant contribution of 0.05% came from weighing [26], based on an estimate of about 0.12% uncertainty per source. The background rate was 4.3 s −1 , accounting to a 0.1%-1% correction, and the imposed dead time was 2-20% at count rates of 500-5000 s −1 .…”

A Practical Way to ISO/GUM Measurement Uncertainty for Analytical Assays Including In-House Validation Data

“…Flicker and Tran, 2016 [92] Weighing uncertainties in quantitative source preparation for radionuclide metrology. Lourenço and Bobin, 2015 [93] Influencing factors in uncertainty measurement that affect mass and volume determination. Technical specification of an analytical balance: readability, repeatability, linearity, off-center loading and hysteresis and for volumetric glassware: repeatability, readability, temperature coefficient of sensitivity, temperature scattering, meniscus reading and environmental conditions (temperature and humidity).…”