[en] The general trends which relate changes in thermal conductivity of UO₂ fuel as a function of temperature and burnup can be summarized as follows: (1) At temperatures below 500⁰C, reductions in UO₂ thermal conductivity relative to the unirradiated values can be expected up to a saturation level of approximately 10¹⁹ fissions/cc. (2) At temperatures above 500⁰C, the thermal conductivity will undergo little change at low burnups, (less than 10¹⁹ fissions/cc) but at higher exposures some decrease can be expected which should, in turn, diminish with increasing temperature. (3) A review of the data reported by Berman on the ThO₂--UO₂ fuel indicates that the basic behavior is the same as for UO₂ in the temperature range of major interest. The applicability of this data to LWR UO₂ fuel is somewhat questionable because of basic physical property differences, and limited data on irradiation effects, and would not seem to support concerns that the effects of burnup on thermal conductivity for LWR fuel may be of more significance than currently believed. (4) A mathematical expression of the type proposed by Daniel and Cohen seems to provide a reasonable approximation for the behavioral trends reported in the literature which relate changes in thermal conductivity to increasing burnup in certain temperature regimes. Calculations indicate that only small incremental increases in the fuel centerline temperature might be expected if burnup effects are taken into account