Activities of 203Hg and other in duced radionuclides were
measuredusing an absolutely calibrated gamma spectrometric
assembly(Canberra)with an HPGe detector with relative efficiency
of 18% and FWHM¼ 1.8keV for energy of 1332 keV.The
detector is placed in a shielding box with lead walls 5cm thick.For
calibration,point radionuclide standards were used.The distance
bet ween the sample and the detector head was 30cm.During
decay of the 203Hg radionuclide,gamma photons with energy of
279.2keV and X-ray photons with energies from 70keV to 83keV
are emitted.For activity evaluation,only the gamma line was used,
because the X-ray signal for the samples was below the detection
limit even when a special X-ray detector was used. Activity was
adjusted for non-point geometry(afactorof1.1)and gamma self-
absorption(afactorof1.05)for the 279.2keV line.The main
problem during 203Hg activity measurement is the presence of
radionuclide sinduced in luminescent material like 152Eu, 122Sb
and 124Sb with high activities,which leads to longer measuring
times – typically5–20 h.The optimum start time for measurement
was determined to be 20 to 40 days after irradiation, when
activities of shorter half-life radionuclides have declined, and 203Hg
activity has not yet declined significantly.