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Radioactivity Group

The Radioactivity Group's mission is to develop, maintain, and disseminate radioactivity standards, develop and apply radioactivity measurement techniques, and engage in research to meet the requirements for new standards.

The principal mission of the Radioactivity Group is to realize and disseminate the Système International (SI) unit for activity, the becquerel (Bq). We support stakeholders in government, industry, and academia with standards and calibrations essential to applications in security, environmental monitoring, medicine, and basic scientific research.

We lead the National effort, in collaboration with the Department of Homeland Security, to develop standards and protocols for radiation instrumentation for early and emergency responders. We developed and administer the National Voluntary Laboratory Accreditation Program (NVLAP) for instrument testing. Our scientists also spearhead the development of ANSI standards and testing protocols for spectroscopic portal monitors, neutron detectors, x-ray and high energy gamma-ray interrogation methods, x-ray imaging, data formats for instrumentation data output, and training standards for responders.

The Radioactivity Group’s nuclear medicine program provides the National standards for radionuclides used in 13 million diagnostic procedures and 200,000 therapeutic nuclear medicine procedures annually in the US. Traceability to our standards has defined quantitative imaging endpoints for large multi-center clinical trials. Our standards enable precision medicine by defining accuracy in clinical administrations of radiopharmaceuticals, improving patient safety, and allowing absolute personalized dosimetry.

The Radioactivity Group's environmental program develops and disseminates reference materials for low-level and natural matrix radioactivity measurements. We are heavily involved in international comparisons and have supported international responses to high-impact events such as the Fukushima-Daiichi disaster.

Our work in basic radionuclide metrology is at the core of our programs. Our researchers are recognized internationally as leaders in the development and application of liquid scintillation counting techniques, coincidence counting techniques, and emerging methods involving cryogenic calorimetry. Regular participation in international comparisons and submissions to the International Reference System (SIR) demonstrates the equivalence of NIST standards with those of other metrology institutes. Our scientists further engage in the critical work of nuclear decay data acquisition and evaluation.

News and Updates

Spotlight: Radiometric Dating

Dating can be complicated. Our team uses this instrument — a live-timed anticoincidence counter — to figure the decay rate of an isotope, which we can then use

Projects and Programs


Primary standardization of 212Pb activity by liquid scintillation counting

Denis E. Bergeron, Jeffrey T. Cessna, Ryan P. Fitzgerald, Lizbeth Laureano-Perez, Leticia Pibida, Brian E. Zimmerman
An activity standard for 212Pb in equilibrium with its progeny was realized, based on triple-to-double coincidence ratio (TDCR) liquid scintillation (LS)

Toward a New Primary Standardization of Radionuclide Massic Activity Using Microcalorimetry and Quantitative Milligram-Scale Samples

Ryan P. Fitzgerald, Bradley Alpert, Dan Becker, Denis E. Bergeron, Richard Essex, Kelsey Morgan, Svetlana Nour, Galen O'Neil, Dan Schmidt, Gordon A. Shaw, Daniel Swetz, R. Michael Verkouteren, Daikang Yan
We present a new paradigm for the primary standardization of radionuclide activity per mass of solution (Bq/g). Two key enabling capabilities are 4π decay

Tools and Instruments



Group Leader

Group Secretary