Performance of IRD-WBC HPGe detection system for low energy photon emitters in lungs.

The Whole Body Counter Facility (WBC) of IRD-CNEN in Brazil has been operating since 1986. The first system installed to perform in vivo measurements of low energy photon emitters radionuclides used Phoswich detectors. In 1998, the WBC unit was upgraded by the installation of an array of four low energy high purity germanium detectors. The performance and suitability of the detection system for lung measurements were evaluated by comparison with the annual dose limits and the detection limits obtained for 238U, 235U, 226Ra and 241Am. This evaluation determined whether the in vivo measurements are adequate. In order to compare the dose limit of 20 mSv y(-1), recommended by the International Commission on Radiological Protection (ICRP), with the in vivo monitoring technique, the minimum detectable intake (MDI) was calculated using the appropriate biokinetic models described in the ICRP Publications. The results were obtained for a single intake through inhalation. The AMAD considered was 5 microm.