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

Abstract

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-energy spectrometry using chip-scale sub-Kelvin microcalorimeters and direct realization of mass by gravimetric inkjet dispensing using an electrostatic force balance. In contrast to traditional traceability, which typically relies on chemical separation of single-radionuclide samples, 4π integral counting, and additional spectrometry methods to verify purity, the system described here has both 4π counting efficiency and spectroscopic resolution sufficient to identify multiple radionuclides in the same sample at once. This enables primary standardization of activity concentrations of mixed-radionuclide samples. A major benefit of this capability, beyond metrology, is in assay of environmental and forensics samples, for which the quantification of multiplenuclide samples can be achieved where presently inhibited by interferences. This can be achieved without the need for chemical separations or efficiency tracers, thereby vastly reducing time, radioactive waste, and resulting measurement uncertainty.

Development of a high precision electrostatic force balance for measuring quantity of dispensed fluid as a new calibration standard for the becquerel

“…radionuclide per mass of the aqueous sample, typically expressed in units of becquerel per gram [1]. A complicated procedure involving multiple steps of sample preparation and characterization are required to certify SRMs, and in some cases, current methods do not provide low enough uncertainty for end applications [2,3]. The true becquerel project at National Institute of Standards and Technology (NIST) aims for a new paradigm to realize and disseminate radionuclide activity using decay energy spectroscopy.…”

“…The true becquerel project at National Institute of Standards and Technology (NIST) aims for a new paradigm to realize and disseminate radionuclide activity using decay energy spectroscopy. This method, illustrated in figure 1, uses a superconducting transition edge sensor which is a cryogenic calorimeter measuring heat energy in the pico-Joule range [3,4]. This allows simultaneous counting and energy measurement of individual decay events.…”

“…Standard Reference Materials (SRMs) are usually supplied as aqueous solutions of specific radionuclides with a known massic activity specified in becquerel per gram of solution. A complicated procedure involving multiple steps of sample preparation and characterization are required to certify SRMs, and in some cases, current methods do not provide low enough uncertainty for end applications [4] [5]. The True Becquerel project at NIST aims for a new paradigm to realize and disseminate radionuclide activity using Decay Energy Spectroscopy.…”