Laboratory Intercomparison of Radon-in-water Standards

The standardization of instruments used for radon-in-water measurements typically involves handling and disposal of Ra in solution. To avoid contact with the Class A carcinogen, radium-free solutions were prepared and tested for use as radon-in-water standards. Filters containing known amounts of Ra were sealed in polyethylene and placed in vials filled with distilled water for >30 days to allow the decay products to establish secular equilibrium. Voluntary intercomparisons of the radon-in-water standards were conducted to investigate the accuracy of analyses by commercial, government, and private companies. Various analytical methods were utilized by the participants. Result show that, at radon concentrations of 18,700 and 3850 pCi/L (693 and 143 Bq/L, respectively), most participants reported concentrations within 25% of the known amounts.