Radon tightness of different sample sealing methods for gamma spectrometric measurements of 226Ra

Different methods for sealing sample containers for 222Rn when measuring 226Ra through its progenies 214Pb and 214Bi using gamma-ray spectrometry have been investigated. Results show that a method consisting of vacuum packaging of the sample container in a sealed aluminium lined bag gives excellent results for ensuring radon tightness. However, care should be taken to fill the sample container completely in order to avoid systematic errors due to radon accumulating in the void volume.