Abstract
Experiments on direct probe measurements and smear tests were performed on various surface materials contaminated with alpha emitters, with a view to make clear the relations between the measurement effectiveness and the nature of surface. Uranium and 241Am were used for low and high specific activity contaminants, respectively. Main observations for direct measurements are: 1. For low specific activity alpha emitters, alpha probe measurements are unsuitable. Beta-gamma probes should be used, since the response is fairly constant on surfaces and compares well with that obtained from a thin alpha calibration source. 2. For high specific activity alpha emitters, the sensitivity of alpha probe measurements confirms the level of the derived limit of alpha surface contamination for controlled areas (3.7Bq/cm2), although the response varies with the nature of surface by factors less than 5.
Per cent activity transferred to smear from surfaces are presented for low and high specific activity nuclides.
