Development and intercomparison of a reusable radon-in-water standard

摘要

Radium-free standards are not readily available for proficiency testing of laboratories that conduct radon (Rn-222) analyses of water. For this study, 33 identical, reusable, radon-in-water standards were prepared using a Ra-226-loaded filter sandwiched in polyethylene sheeting. The Rn-222 concentrations in the Ra-226-free standards were measured by liquid scintillation counting and compared to 10 reference solutions containing Ra-226. The Rn-222 concentrations measured in the standards were consistent (standard deviation of <2%), but averaged substantially less than concentrations determined in the Ra-226 reference standards. At full ingrowth, 86% of the Rn-222 produced by the sandwiched Ra-226 sources emanated into the water. An intercomparison of radon-in-water standards, performed to examine the accuracy of analyses by commercial, government, and private companies, showed that 18 of the 21 participants reported concentrations within 25% of the known (693 Bq l(-1)).