Radiochemical analysis of a wide range of 131 I activities in water and milk using well-type germanium detector

We report a study of a fast radiochemical method to determine the activity of 131I via the radiochemical recovery obtained with a 129I tracer. Previous methods were valid for low levels of 131I activities. In the new method, we developed a correction using the 29.7-keV X-ray peak from Xe, taking into consideration that this peak originates from both and 131I decay. This enables quantitation of high levels of 131I activity. Furthermore, for a very high 131I activity, one can use the 39.6-keV gamma peak which is unique to 129I. Combining both approaches enables quantitation of 131I activities up to 200 times that of the 129I recovery tracer.