Denis E. Bergeron is a NIST research chemist in its Radioactivity Group whose work concerns physical radioactive activity measurements and standards. His official profile identifies his work in that group; an author account in the Journal of Research of NIST documents the comparison of primary activity standards over several decades.[ref][ref]
In the 2014 coauthored review, Bergeron and colleagues examined ten fluorine-18 standardizations from 1982 to 2013. A new standard differed by about 4 percent from results obtained in1998–2008. The authors compared multiple primary measurement methods and possible sources of bias, while explicitly reporting that the older discrepancy was not fully explained.[ref]
A Review of NIST Primary Activity Standards for 18F: 1982 to 2013 by Denis E. Bergeron and others. Abstract; §4 Discussion, comparison of techniques and unresolved bias
A simple ionization chamber example shows why a calibration difference matters. Suppose measured electric current is and the response model is . A hypothetical factor gives activity . Replacing it by gives approximately for the same current, an increase of about .
These numbers are invented, not the review's calibration table. They separate the detector observation from the inferred radioactive activity. Bergeron's standards work demonstrates why cross-method comparisons and an explicit measurement uncertainty budget matter even when repeated readings are consistent.
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