On low-level tritium measurements with LSC Quantulus

Low-level measurements of H-3 have been made with the Quantulus liquid scintillation counter (LSC) using different scintillation cocktails together with selected types of counting vials. Comparisons were made between counters at the underground laboratory Felsenkeller (110 m water equivalent) and in an above ground laboratory (0 m water equivalent) of the TU Freiberg. In the underground laboratory, the background is strongly influenced by the beta-decay of the Rn-220-daughter Pb-212 (T-1/2 = 10.6 h) from the laboratory air, stimulating luminescence irradiation in the vial. The effective background count rate in the H-3-window (having subtracted the luminescence effect) in the underground laboratory is two times lower than that in the above ground laboratory due to the better shielding of cosmic rays. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.