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Summary
Nearly every measurement or calculation in nuclear science relies on nuclear data to obtain a final result. Decay corrections for radioactivity measurements require accurate half-lives and are needed for yield calculations in isotope production. Gamma-ray, x-ray, beta-particle, and alpha-particle energies and emission probabilities are important for radionuclide identification and in calculating the dose rates from radioactive sources. All these quantities are used as input to dosimetry calculations for radionuclide therapy treatment planning, and to many of the models used in radionuclide metrology for calculating detection efficiencies.
Description
Spectrum showing the annihilation photon peak and bremsstrahlung background resulting from the very weak pair-production branch in the decay of a source of 90Y.
The Radioactivity Group is an active contributor to the nuclear data community through the measurement of absolute gamma-ray emission probabilities and half-lives. In fact, the measurement or re-measurement of these data forms a part of nearly every primary standardization that is undertaken by the Group. Recent work has focused on the determination of these quantities for many of the alpha-emitting radionuclides currently being studied for use in radionuclide therapy and includes 212Pb, 223Ra, 224Ra, 225Ac, and 227Th. Measurements have also been reported for nuclides of interest in other areas of nuclear medicine and nuclear energy, and include published data for 90Y, 124I, and 153Gd, with work on 89Zr underway.
The Radioactivity Group also contributes to the evaluation of nuclear data through participation in the Decay Data Evaluation Project (DDEP), which is an international collaboration aimed at providing critically evaluated nuclear data relevant to radioactivity measurements. Recent evaluations carried out by Group staff include those for 124I, 166Ho, and 212Pb. Evaluations for 224Ra and 225Ac are underway. Additionally, DDEP members are asked to provide peer reviews of evaluations performed by evaluators at other institutes. Such peer reviews have recently been undertaken by Radioactivity Group staff for 40K, with reviews in progress for 68Ga and 229Th.
Staff of the Radioactivity Group also serve as the NIST representative to the Interagency Nuclear Data Working Group, which seeks to promote and coordinate nuclear data activities in general (not just decay data) across all Federal agencies.
Future plans call for the construction of a new gamma-ray detection system that will allow for the measurement of gamma-gamma angular correlations that permit mixing ratio determinations. We also hope to investigate the potential to use Decay Energy Spectrometry for the measurement of internal conversion and Auger electron spectra.