Tele-manipulation is indispensable for the nuclear industry, since teleoperated robots cancel the radiation hazard problem for the operator. However, the performance limitations of teleoperated robots for nuclear decommissioning tasks is not clearly answered in the literature. In this paper, we propose a task performance-based methodology to evaluate the performance of bilateral teleoperation of a robotic arm working inside a glovebox. A test based on radiation surveying is designed and the performances of manual task execution and tele-manipulation are compared. Our results show that the current commercial off-the-shelf (COTS) teleoperated robotic manipulation solutions are flexible, yet insufficient, as their task performance is significantly lower compared to manual operation and potentially hazardous for the equipment inside the glovebox. Finally, We present set of rules and solutions, which are deducted from our observations and expert interviews, for better performance in teleoperation in glovebox environments.