A partial body counter for incorporated low level actinides

Abstract

A new partial body counter has been installed and calibrated at the Institute of Radiation Hygiene of the Federal Office for Radiation Protection, Munich, Bavaria. The system is especially designed for radionuclides emitting low energy photons such as²⁴¹ Am and²¹⁰Pb. In addition, thorium, uranium and daughter products,⁶⁰Co,¹³⁷Cs and⁴⁰K can be detected. The main components of the system are a shielding chamber, 4 high purity low-energy germanium detectors with beryllium windows and the corresponding electronics and software. A LLNL Realistic Phantom is used to calibrate the system. Inactive organs and organs loaded with a known amount of²⁴¹Am (right lung, left lung, liver) are available to quantify the response of each detector separately. Detector efficiencies are given as function of chest wall thickness (1.7 to 3.4 cm). Lower limits of detection for²⁴¹Am using a measurement time of 3600 seconds are 6, 7 and 7 Bq for right lung, left lung and liver, respectively. In order to estimate skeleton activities, a skull phantom loaded with²⁴¹Am is available. For one detector, the lower limit of detection for the skull is 2 Bq.