Radionuclide metrology: confidence in radioactivity measurements

Abstract

Radionuclides, whether naturally occurring or artificially produced, are readily detected through their particle and photon emissions following nuclear decay. Radioanalytical techniques use the radiation as a looking glass into the composition of materials, thus providing valuable information to various scientific disciplines. Absolute quantification of the measurand often relies on accurate knowledge of nuclear decay data and detector calibrations traceable to the SI units. Behind the scenes of the radioanalytical world, there is a small community of radionuclide metrologists who provide the vital tools to convert detection rates into activity values. They perform highly accurate primary standardisations of activity to establish the SI-derived unit becquerel for the most relevant radionuclides, and demonstrate international equivalence of their standards through key comparisons. The trustworthiness of their metrological work crucially depends on painstaking scrutiny of their methods and the elaboration of comprehensive uncertainty budgets. Through meticulous methodology, rigorous data analysis, performance of reference measurements, technological innovation, education and training, and organisation of proficiency tests, they help the user community to achieve confidence in measurements for policy support, science, and trade. The author dedicates the George Hevesy Medal Award 2020 to the current and previous generations of radionuclide metrologists who have devoted their professional lives to this noble endeavour.

Ambient humidity, the overlooked influencer of radioactivity measurements

“…The inside temperature remains relatively stable during colder days, but there is a slight positive quadratic trend overall. Despite the strong correlation between activity measurements in the ionisation chamber IC1 [1,2,46,47] and outside temperature, they are only weakly correlated with the inside temperature. Therefore, the inside temperature is not the main driving force behind IC1's seasonal effect, and air humidity in the room is more likely the culprit.…”

“…Science-based decision making crucially depends on the quality of the metrology from which it derives its information [1,2]. Measurements with incomplete uncertainty budgets can lead to misinterpretations of the phenomena under investigation, possibly with fundamental implications in science and policy making [3].…”

“…Some authors are adamant in their claims that observed violations of the exponentialdecay law cannot be attributed to environmental conditions in the laboratory [5,6]. However, using historical weather data available on meteorological websites, a link with terrestrial weather could be established for several infamous experiments [1,2,4,[7][8][9][10][11][12][13][14][15][16][17][18][19].…”