Optimum use of broken Charpy specimens from surveillance programs for the application of the master curve approach

Broken Charpy specimens can be used in various ways to determine the reference temperature. T₀, as defined in the Master Curve approach. Reconstitution and machining of subsize specimens are two solutions for direct toughness evaluation. The optimum technique and specimen geometry preferentially: use a minimum number of broken half Charpy's, have a small uncertainty on the reference temperature, have the widest valid test temperature window, have a reasonable cost, and are easy to perform into hot cells. In this study, the use of various miniature specimen types such as Compact (C(T)), Single Edge notch Bend, (SE(B)), or Miniature Precracked Charpy (MPCCv), and Circumferentially Cracked Round Bars (CRB), is investigated. As this study deals with small specimens, the problem of loss of constraint is also addressed. Taking all constraints into account, a 0.16T-C(T) specimen is found to be the more promising geometry. This work is supported by experimental data generated on various specimen types and sizes on the well-characterised reactor pressure vessel steels 22NiMoCr37, 20MoNiCr55 and JRQ.