A long-term performance evaluation of the gamma-ray activity measurement laboratory in CPST, Lithuania.

Abstract The quality control procedures used for two HPGe detectors (a well-type and a GAMMA-X coaxial) are described. Since 2001, check sources containing 137 Cs have been measured weekly for 7200s each, and the gamma-ray spectrometry system background was determined once per month for an acquisition time of 100,000 s. The laboratory participated in the international comparisons at environmental radioactivity level organized by the IAEA, Riso National Laboratory and NPL.