This paper describes the outline of a model-based remote maintenance robot system for nuclear facilities such as nuclear power plants and nuclear fusion reactors. This robot system aims at autonomously carrying out maintenance tasks when the operator directs by task level commands: for example, `set flange' and `set valve'. This time, the robot system was applied to fundamental tasks for maintenance work, `insert a bolt' and `set a nut' on a flange. This robot system is composed of an environment measuring device for measuring the position of the object to be handled, a task planner which generates the robot control program from the task level command, and an arm controller which moves the arm under either position or stiffness control according to the generated program. In the experiments, the robot system carried out inserting a bolt and setting a nut on the flange.