Development of a radioxenon measurement system and its application in monitoring Fukushima nuclear accident

An HPGe gamma-ray spectrometry system for radioxenon isotopes detection has been developed. The system was comprised of two low-energy planar HPGe detectors that were horizontally and oppositely placed, and a gas source cell made of carbon fiber in both sides was used. The spectra obtained simultaneously by the two HPGe detectors were analyzed by summing spectrum method. After the radioactive concentration of 133Xe was determined with three internal gas proportional counters, the efficiency of 81 keV gamma-ray for 133Xe was calibrated to be 0.50 (1), and the Minimum Detectable Activity (MDA) for 133Xe detection was determined to be 10 mBq during 1 day measurement time. Finally, the system was applied in atmospheric 133Xe monitoring at Xi'an of China after the Fukushima nuclear accident.