Interpretation of crack propagation events on the basis of acoustic emission signals and other non-destructive test results concerning cracks in a RPV nozzle under cycle thermal shock loading

Cyclic thermal shock tests have been performed on a RPV nozzle (HDR) with cracks in order to apply and to assess techniques available for the description of real cracks (non-destructive testing, fracture mechanics calculation). In this paper the application of dye penetrant testing, potential drop testing and acoustic emission measurements on the nozzle is considered. Some experimental results are described in detail; assessments have been possible on the basis of destructive testing (fractography). The determination of crack parameters for correlating these NDT results with fracture mechanics data are discussed such as crack depth, a, cracklength, crack area and crack growth. Crack growth is considered over a period of cycles, a(N), per cycle, da/dN, and during a cycle, da/dt. A selection of numerical NDT findings is presented and compared with the results of fracture mechanics calculations