Reliability of the control rod drive mechanisms as a function of various types of their proof tests

This paper deals with the reliability of the control rod drive mechanisms as a function of various types of their proof tests. These testings can be categorized into two items, i.e. type approval test, or endurance limit test, and design basis (qualification) test. A prototype control rod drive mechanism was manufactured and tested on the rolling rig at the ''Geselschaft fuer Kernenergieverwertung in Schiffbau und Schiffahrt'' in Geesthacht, Federal Republic of Germany. In the endurance limit test the expected actuations during the total operating time are simulated in a compressed amount of time. It is almost impossible to get the data for the probabilistic analysis of the system failure by such tests. However, based one the knowledge of mode of failure obtained by the testing, the test made on a certain number of paptial structures can provide the information needed to estimate the damage accumulation law and the failure rate of the whole mechanism