Methods for Determining Radon‐222 and Radium‐226

Abstract

The purpose of this study was to develop a simple, reliable, and reproducible field method for the analysis of certain of the naturally occurring radioisotopes in water. The procedures were applied to the analysis of water supplies, particularly groundwaters, during a relatively extensive field sampling program. The requirements, therefore, differed from those of many existing analytic methods in that equipment had to be compact and portable. In order to achieve significant results during a limited and expensive field survey, it was desirable that the analytic procedures be as rapid as possible without loss of accuracy. The analytic procedure studied involved the de‐emanation of Rn222 from solution and the collection of the gases in an erlenmeyer flask coated with a powdered, silver‐activated zinc sulfide screen, followed by alpha scintillation counting. Water samples were collected in specially designed glass bubblers. De‐emanation was achieved by means of an evacuated erlenmeyer flask connected to a bubbler. The vacuum was used to produce an upward flow of air through the bubbler, resulting in radon removal from the water and collection in the flask. The analysis was completed by alpha scintillation counting of the flask, with the use of a specially designed detection unit. Ra226 was also analyzed with the use of a simple modification of the de‐emanation procedure. After de‐emanation for radon analysis, the water sample was thoroughly purged of any remaining radon. The bubbler was then sealed for 8‐12 days to allow the buildup of radon from the radium in the sample. A second radon analysis was performed on the sample, and the radium content was calculated with the use of the known state of partial equilibrium between the two radioelements.