The standardization of 188W/188Re by 4πβ liquid scintillation spectrometry with the CIEMAT/NIST 3H-standard efficiency tracing method

The massic activity of a solution containing 188W in equilibrium with its daughter, 188Re, has been standardized by the National Institute of Standards and Technology using 4πβ liquid scintillation counting with efficiency tracing using the CIEMAT/NIST method. Confirmatory measurements were carried out with γ-ray spectrometry using high purity germanium detectors and a 4πγ NaI(Tl) system. A calibration factor of 1.68MBqpA−1±0.03MBqpA−1 (expanded, k=2, uncertainty) for the 188W in the solution was determined, along with correction factors for activity determinations using Capintec dose calibrators. A half-life value of 69.78d±0.05d (standard uncertainty) was determined by measurement in the NIST 4πγ ionization chamber and is consistent with currently recommended values.