Diagnostics of control rod drive. Possibilities to extend its lifetime at NPP's

According to specifications, lifetime of a linear stepping electromagnetic drive in WWER1000 nuclear reactors is limited by the pre-assigned lifetimes of the drive components such as electromagnets, a latch assembly, drive rack, and control rod position sensor. The lifetime of the drive components is from 7 to 20 years. On the basis of diagnostics of these components under real conditions, actual lifetimes of the components at nuclear power plant (NPP) were forecasted. It is shown that in order to extend the lifetime of the drive components up to the reactor lifetime (60 years), it is necessary to replace the sensor of the DPL-type by the new one (of the DPL-KV type) and to decrease the electromagnet temperature. The Measuring and Diagnostic System with the DPL-KV sensor enables diagnosing the sensor, electronic processing unit and drive. Economic effect due to the cumulative technical decisions is estimated to be 7 mln.euro per NPP unit.