The use of high-security valves in nuclear power plants requires special actuators equipped with direct-current (DC) motors and, in most cases, worm gearboxes as drive unit. These actuators can be connected directly to a battery without a rectifier. In case of a loss-of-coolant accident (LOCA), the control and regulation systems in the actuator may fail. A LOCA scenario can occur at any time during the service life of a nuclear power plant, which is why the actuator, and thus the worm gear, may be subjected to mechanical and thermal overloads. Similarly, the safety functions of nuclear power plants are tested at regular intervals, during which the worm gear is also subjected to mechanical overload. The research project NEWTOSC aims to investigate the effects of this mechanical overload on the load-carrying capacity and efficiency of the worm gear. 
At present, it is unclear to what extent the timing of a mechanical overload affects the loadcarrying capacity and remaining service life of the drive unit, and thus a safe operation in case of a malfunction. Such overload scenarios cause significant fluctuations in the efficiency of the worm gear, which significantly alter the required drive power and can lead to safety-critical malfunctions in the event of an uncontrolled accident. Therefore, a reliable assessment of the efficiency of the worm gear during an overload scenario worm gear is necessary. A reliable estimate of efficiency forms the basis for the design of the worm gear and enables a precise evaluation of the changes that occur during operation. However, in case of an overload, temperatures and loads occur that are significantly higher than the usual parameters of a worm gear and lead to plastic deformation. Investigations and targeted measures are therefore necessary to make reliable remarks about efficiency and load-carrying capacity in such extreme situations.