[en] Experiments were performed in the irradiation tunnel of the 100 kW research reactor of the Institute of Nuclear Technics of the Technical University of Budapest. Dose rates were measured in a straight cylindrical duct and in ducts with bends of 30, 60 and 90 deg. Al₂O₃:Mg,Y ceramic TL detectors type D-2, developed at the Institute of Isotopes, were found to be better or measuring gamma ray dose than TLD-700, not only because of their linearity over a fairly wide dose range (10^-1-10³Gy) but also their lower sensitivity (3.4 mGy per 10¹⁰ n.cm^-2) to thermal neutrons. (author)