DEPENDENCE OF TLD THERMOLUMINESCENCE YIELD ON ABSORBED DOSE IN A THERMAL-NEUTRON FIELD

The emission from (LiF)-Li-6 and (LiF)-Li-7 thermoluminescence dosimet ers (TLDs) exposed to the mixed field of thermal neutrons and gamma-ra ys of the thermal facility of a TRIGA MARK II nuclear reactor has been investigated for various thermal neutron fluences of the order of mag nitude of those utilised in radiotherapy, with the purpose of investig ating the reliability of TLD readouts in such radiation fields and of giving some information for better obtainment of the absorbed dose val ues. The emission after exposure in this mixed field is compared with the emission after gamma-rays only. The glow curves have been deconvol uted into gaussian peaks, and the differences in the characteristics o f the peaks observed for the two radiation fields; having different li near energy transfers, and for different doses are shown. Irreversible radiation damage in dosimeters having high sensitivity to thermal neu trons is also reported, showing a memory effect of the previous therma l neutron irradiation history which is not restored by anneal treatmen t. (C) 1997 Published by Elsevier Science Ltd. All rights reserved.