A review of acoustic emission for pressurised water reactor applications

Abstract

The nuclear core of a pressurised water reactor (PWR) is contained in a thick-walled ductile steel pressure vessel which is manufactured and maintained at a very high standard of structural integrity. Manufacturing defects are detected and monitored by non-destructive examination techniques, like ultrasonics and radiography, but at considerable cost and with some difficulty. Since its inception in the early 1960s, acoustic emission has offered potential as an additional technique for this work, with attractions of relative simplicity and cheapness. A large part of the early development of acoustic emission was aimed at nuclear applications, in particular monitoring for defects in pressure vessels during periodic over-pressure test and during service. In later years it was realised that ductile steels are poor emitters and it became apparent that early claims for the technique had been over-optimistic. This review considers the current understanding of the fundamental aspects of acoustic emission and of the available instrumentation and techniques for the following potential applications: (1) detection of manufacturing defects during pre-service inspection; (2) continuous monitoring for crack growth; (3) continous monitoring for coolant leakage; (4) fabrication weld monitoring.It is concluded that the first and second applications are unlikely to be successful in the near future, largely because of the quiet nature of ductile steel, the problems of plant-noise and the difficulties in interpretation of signals received. The third and fourth applications require further development but already show significant promise of helping to establish and maintain pressure vessel integrity.