USE OF MINI-CT SPECIMENS FOR FRACTURE TOUGHNESS CHARACTERIZATION OF LOW UPPER-SHELF LINDE 80 WELD

Any fracture toughness specimen that can be made out of the broken halves of standard Charpy specimens may have exceptional utility for evaluation of reactor pressure vessels since it would allow one to determine and monitor directly actual fracture toughness instead of requiring indirect predictions using correlations established with impact data. The Charpy V-notch specimen is the most commonly used specimen geometry in surveillance programs and most likely to be used in advanced reactors as per ASME code. The advantage of the Mini-CT specimen technique is that multiple specimens can be machined from one half of a broken Charpy specimen, used in a standard surveillance capsule of a reactor pressure vessel. Up to now, most of the work on validation of this type of the specimens has been performed on base metal. In this study, Mini-CT specimens were used to perform fracture toughness characterization of low upper-shelf Linde 80 weld, designated WF-70. This weld was utilized in the Midland beltline weld and has been previously well characterized at ORNL with various,types and sizes of fracture toughness specimens. The Mini-CT specimens were machined from broken previously tested Charpy V-notch specimens. Despite very small size and relatively small number of Mini-CT specimen tested, the transition fracture toughness temperature, To, derived from these Mini-CT specimens is in very good correspondence with To reported from analysis of a large number of larger fracture toughness specimens.