Recently, the new generation of AUMA SAI and SAN electric actuators for nuclear service have successfully passed demanding type tests. SAI 07.2 – 16.2 and SAI 25.1 – 35.1 (“inside containment”) actuators are now approved to IEEE 382:2006 for use within the reactor building. The SAN 07.2 – 16.2 and SAN 25.1 – 35.1 (“outside containment”) series are qualified for slightly less demanding service in secondary water, steam, and ventilation systems.
The new actuators offer performance to match the longer service life and higher outputs required of modern NPPs, which in turn mean higher steam pressures, larger pipe sizes, higher valve torques, and shorter operating times. The new nuclear actuators are based on AUMA’s latest SA multi-turn design, modified for the demanding environment of a nuclear plant. Plastics used for switches, cables, connectors and sealing elements, for instance, must withstand high temperatures and radiation doses.
For the SAI actuators that are qualified to operate within the reactor containment vessel, ductile (SG) cast iron replaces grey cast iron and aluminium as the material for the actuator housing. The qualification process for NPP actuators is stringent, whether they are designed to operate inside or outside the containment vessel. NPPs are required to withstand severe incidents such as steam and coolant leaks, floods, and earthquakes. Following such incidents, key valves must remain operable to prevent further damage to the plant.
