Use of broken charpy V-notch specimens from a surveillance program for fracture toughness determination

Broken Charpy specimens from the surveillance program of a Belgian nuclear power plant are used to obtain the fracture toughness in the transition regime using the master curve concept. Two approaches are used. The first one is based on the reconstitution of Charpy specimens that are subsequently precracked and tested in three-point bending. The second approach is an innovative one that makes use of miniature Compact Tension specimens, which are machined from the broken pieces of the original Charpy specimens. Both approaches lead to consistent results. The recently developed miniature Compact Tension design has the advantage to use less material and is less costly in terms of machining operation. For the material investigated in this research, the current regulation, based on a semi-empirical approach to obtain the lower bound fracture toughness, is demonstrated to be conservative as compared to the direct fracture toughness determination.