Irradiation experiments in the testing nuclear power plant VAK

The first two capsules were irradiated in the Testing Nuclear Power Reactor VAK. The materials are of the 22NiMoCr37 and 20MnMoNi55 types and represent the lower bound of the base material regarding upper shelf energy and chemical composition (Cu, S, P) as well as a state of material which does not meet both chemical and toughness requirements (low upper shelf test melt). Tensile, Charpy, drop-weight, and fracture mechanics specimens were irradiated up to a range of 1 x 5 to 2 x 1019 cm-2 (>1 MeV). Despite the materials being at or beyond the specification limits, the results show irradiation sensitivity which can be predicted from the US Reg. Guide Trend Curves (1.99) and KWU Trend Curves in a conservative manner. The procedure to determine the adjusted reference temperature RT/sub NDT/ (adj.) on the basis of ΔT41J (following ASTM E 185) could also be confirmed as conservative by comparing the different criteria derived from Charpy and drop weight tests in the unirradiated and irradiated condition. The results of fracture mechanics testing in the linear elastic range show a remarkable temperature margin to the K/sub Ic/-curve of ASME XI /6/. Prestrained compact tension specimens CT 40 mm made of 22NiMoCr37 material with an upper shelf energy of approximately 100 J were wedge loaded in a range up to 30 MPa √m and exposed to the water environment during irradiation. Macroscopic examination gave no indications of stress corrosion cracking. From tests of these specimens in the linear elastic range, a fracture toughness K/sub Ic/, which was not affected by the prestrain and environment history, was found depending only on the overload applied during the prestraining procedure