Development of disc compact tension specimens and test techniques for HFIR irradiations

Near term irradiation of candidate alloys being planned for the High Flux Isotope Reactor (HFIR) in support of ITER and isotope tailoring experiments necessitate the use of relatively small fracture toughness specimens, e.g. down to 12.5 mm in diameter. The specimens will also contain substantial amounts of helium. This paper describes the application of electropotential drop techniques to determine J-resistence curves for this purpose in HT-9 specimens with diameters of 40, 25 and 12.5 mm; in addition, the effects of side grooving were examined. Good agreement between J-resistance curves determined by the electropotential drop and by multiple specimen techniques were obtained for all specimen geometries and sizes. A systematic decrease in JIC with specimen thickness was observed for both side-grooved and smooth specimens with thicknesses below the validity criterion. The tearing modulus was reduced by side groving but was less dependent on specimen size. (orig.)