A radium assay technique using hydrous titanium oxide adsorbent for the Sudbury Neutrino Observatory

As photodisintegration of deuterons mimics the disintegration of deuterons by neutrinos, the accurate measurement of the radioactivity from thorium and uranium decay chains in the heavy water in the Sudbury Neutrino Observatory (SNO) is essential for the determination of the total solar neutrino flux. A radium assay technique of the required sensitivity is described that uses hydrous titanium oxide adsorbent on a filtration membrane together with beta - alpha delayed coincidence counting system. For a 200 tonne assay the detection limit for Th-232 is a concentration of similar to3 x 10(-16) g Th/g water and for U-238 of similar to3 x 10(-16) g U/g water. Results of assays of both the heavy and light water carried out during the first 2 years of data collection of SNO are presented. (C) 2002 Elsevier Science B.V. All rights reserved.