The National Institute of Standards and Technology (NIST) has developed a new standardization for radium-228 (Ra-228), a key isotope used in various geochemical applications. Ra-228, with a half-life of 5.75 years, is a product of the thorium-232 decay series and is primarily used as a monitoring tracer in water quality assessment and estimating the age of radiobarite contaminants.
The Ra-228 used for this new standard was separated from a thorium nitrate solution that was last milked in 1982. The separation process involved several complex steps, including co-precipitation, precipitation, filtration, and gas bubbling. The resulting solution was then filtered, evaporated, and dissolved in nitric acid before being passed through an anion exchange column to remove any remaining thorium residue.
NIST has standardized this Ra-228 as Standard Reference Material (SRM) 4339B, certifying its accuracy through gamma-ray spectrometry confirmation by alpha spectrometry using silicon surface barrier detectors and liquid scintillation measurements. These techniques ensure precise measurement of the dilution factor, providing a reliable standard for various geochemical applications.
Source: https://www.nist.gov/programs-projects/basic-metrology-archive-new-standardization-ra-228
Keywords: Radium, Isotopes, Half-life
