TrueBq: A multidisciplinary project called True Becquerel (TrueBq) was launched at NIST in fiscal year 2021 to help the agency standardize radionuclides. A team of NIST researchers has just published its results on the primary activity measurement of an americium-241 solution in the journal Metrologia.
Their work was innovative because the solution samples tested were first applied by inkjet—in precisely measured microgram quantities—onto a gold foil surface with nanopores. Because a precision mass balance system measures the mass of the substance that is applied to the film, the researchers know exactly how much material is contained in each tiny, dried inkjet drop of material.
NIST expects the TrueBq approach to reduce analysis time and simultaneously increase accuracy by replacing traditional workflows that involve multiple methods and chemical processing.
Testing near absolute zero: Key to the new technique is a transition-edge sensor (TES) used to measure radiation signatures at temperatures near absolute zero. When a radioactive decay occurs, the energy released is absorbed by the TES, causing a change in the electrical resistance of the device. That change is the “signature” of the decay event. By accumulating data from a series of decay events, the researchers build a detailed energy spectrum to identify radionuclides.
Because the researchers know the precise mass of the substance tested, they can calculate the radioactivity per unit mass, or “massic activity,” of the sample with unprecedented accuracy.
“The TES is much more advanced than a familiar Geiger counter or other detectors used today,” said NIST physicist Ryan Fitzgerald. “It gives us a detailed fingerprint of what’s there.”
He added, “Instead of waiting months for results, we can now get a full radioactivity profile in just a few days from a tiny sample.”
Applications and limitations: According to NIST, the technology could one day help ensure the purity and potency of radiopharmaceuticals for cancer treatments, and it could quickly identify the radioactive composition of reprocessed used fuel, speeding the development of advanced reactors and the fuel they will require.
TrueBq’s current focus is on improving measurements at NIST—including the measurements the agency carries out for customers, such as calibrations and the production of standard reference materials. But in the future, according to NIST, researchers “hope to develop more portable and user-friendly versions of the system that could be deployed outside of NIST for critical applications in fields such as medicine, environmental cleanup, and nuclear waste management.”
