γ-ray spectrometry for determination of radium-228 and radium-226 in natural waters

A technique has been developed for the measurement of 228Ra and 226Ra in both fresh- and seawater using Ge(Li) γ-ray spectrometry. Radium isotopes are preconcentrated in the field from 100 to 1000 L onto Mn-impregnated acrylic fiber cartridges, leached from the fiber and coprecipitated with BaSO4. Lower limits of detection are controlled by the volume of water processed through the Mn fibers. In a 1-day count, samples as low as 10 dpm are measured to +-10% uncertainty. This Mn-fiber-γ-ray technique is shown to be more accurate than the 228Ac methods recommended by the Environmental Protection Agency and as accurate but more rapid than the 228Th-Ingrowth procedure