title: 228Ra and226Ra measurement on a BaSO4co-precipitation source.
abstract: One of the most commonly-used methods for determination of226Ra, particularly in water samples, utilises co-precipitation of Ra with BaSO4, followed by microfiltration to produce a source for alpha counting. This paper describes two extensions to BaSO4co-precipitation methods which enable determination of228Ra using the same source. The adaptations presented here do not introduce any contaminants that will affect the separation of radium or alpha counting for226Ra, and can be used for re-analysis of already existing sources prepared by BaSO4co-precipitation. The first adaptation uses detection of228Ac on the source by gamma spectrometry. The detection efficiency is high, allowing analysis of water samples at sufficiently low activity to be suitable in testing for compliance with drinking water quality standards. As228Ac grows in quickly, taking less than 2 days to reach equilibrium with the228Ra parent, this can also be useful in radiological emergency response situations. The second adaptation incorporates a method for the digestion of BaSO4sources, allowing separation of thorium and subsequent determination of228Th activity. Although ingrowth periods for228Th can be lengthy, very low detection limits for228Ra can be achieved with this technique.
authors.affiliation: Environmental Research Institute of the Supervising Scientist (eriss), Darwin, NT 0810, Australia. Electronic address: peter.medley@environment.gov.au.
authors.forename: Peter
authors.initials: P
authors.lastname: Medley
authors.affiliation: Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), Yallambie, Vic. 3085, Australia.
authors.forename: Paul
authors.initials: P
authors.lastname: Martin
authors.affiliation: Environmental Research Institute of the Supervising Scientist (eriss), Darwin, NT 0810, Australia.
authors.forename: Andreas
authors.initials: A
authors.lastname: Bollhöfer
authors.affiliation: Charles Darwin University, Darwin, NT, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Parry
keywords: Alpha spectrometry; BaSO(4) co-precipitation; Drinking water; Gamma spectrometry; Radium-226; Radium-228