Radon daughter considerations in a nuclear power plant

A boiling water reactor in the start-up phase experienced a significant number of personnel contamination monitor alarms caused by radon daughter plateout on hard hats, clothing, and shoes. Alarm frequencies were compared to environmental conditions and ventilation system operations to determine the effects of various factors on radon plateout. High normal ventilation, radon daughter concentrations in the plant were found to be similar to outdoor concentrations, and alarm frequencies were inversely related to relative humidity. When ventilation systems were shutdown, indoor radon levels and personnel contamination monitor alarm rates increased significantly. In this paper some suggestions for accounting for radon daughter contamination in monitoring and training programs are presented