[en] Fluorimetry can possibly be used in the process of in-line uranium concentration monitoring in raffinate during the codecontamination process in nuclear fuel reprocessing plants, since it has an intrinsic high sensitivity and a capability for remote monitoring using fiber optics. Before its practical application, factors influencing UO₂²⁺ fluorescence, such as temperature, coexisting species, etc., must be examined. In this paper, the effect of temperature on UO₂²⁺ fluorescence was studied in a system without coexisting species