Leakage testing of medical radium sources

The results of leakage tests on approximately 2000 clinical radium sources in current use in several hospitals are presented. The tests were carried out using a liquid scintillation immersion method. Less than 1% of the sources leaked radon gas (222Rn) to an extent greater than 1 nCi/24 h. The consequences of a small leakage of radon from a source while implanted in tissue are considered and compared with the hazards and problems created when sources leak during storage. A leakage rate of 1 nCi/24 h is suggested as an appropriate limit beyond which sources should be removed from use.