Control of technical safety during normal reactor operation

In this report the possibilities and limitations of noise diagnosis at nuclear power reactors are outlined, the status of application and research work in this field is reviewed. Due to the fact, that noise diagnosis is principally suited to shut a gap in the system of technical safety assurance in nuclear power stations, a growing interest exists for this field of investigation. The gap consists in the practical lack of control of technical safety during the normal plant operation. It has been drastically demonstrated by some accidents that malfunctions can rise unnoticed and cause damages which need long down times of the plant for repair. It is well known, that the noise part of different reactor signals contains information about certain processes, as for example mechanical vibrations of reactor components, which may cause damages. Controlling these processes the detection of malfunctions in an early stage is possible and their further development may be prevented. In the last years some remarkable results are gained concerning the diagnosis of certain malfunctions, in first line the detection of core barrel movements and of loose parts in the coolant circuits. First experiences with complex systems for early detection of malufnctions are very encouraging too. The control of technical safety during normal reactor operation by means of noise diagnosis has come near at hand