Dispersions of undissolved palladium or ruthenium in nuclear glass can affect the glass flow during the vitrification process. As a consequence, one of the major challenges in nuclear glass elaboration is to understand and control the rheological behavior of glass melts. In this context, this work aims at describing accurately the rheological behavior of glass melts containing platinum group metals to better model the thermal hydraulics in vitrification process. A Searle viscometer has been used to characterize the non-Newtonian behavior of nuclear glass melt containing these noble metals versus temperature and shear rate. Obtained data have been compared to different reference models (Bingham, Ostwald ... ) in order to find the appropriate relation describing rheological behavior of nuclear glass melts. The specific role of low shear rates on viscosity measurements has been highlighted. Finally, another investigation under a constant low shear rate has been performed at high temperature during a few hours with the view to clarify this role and the associated physical phenomenon.