Abstract: An improved robotic arm for effecting a tube plugging operation is disclosed herein. The improvement generally comprises the provision of a compliance coupling between the plugging tool and the guidance mechanism of the robotic arm that is compliant in three dimensions, thereby allowing the plugging tool to smoothly insert tube plugs into the mouths of heat exchanger tubes despite inaccuracies in alignment caused by sag and other factors. The improvement further comprises a length adjustment assembly for allowing the length of the base arm of the robotic arm to be easily and conveniently changed so that the robotic arm can service more than one particular type of nuclear steam generator, as well as an emergency release mechanism for remotely detaching the tool from the arm in the event of a jam.