Validation of RTTO for German reactor pressure vessel steels

For the introduction of the new reference temperature RTTo of the ASME Code Cases N-629 and N-631 into the German KTA rules the equation RTTo = T0 + 19,4°C (35°F) was validated by the re-evaluation of the existing fracture toughness data base of German RPV steels, including unirradiated and irradiated base material and weld metal data. The test temperatures of the data base were standardized to the reference temperature T0 of the Master Curve of the data sets and the data base was compared with the ASME KIc-curve as adjusted by RTTo. The KIc-curve adjusted by RTTo enveloped both, the 1T-size adjusted data base and also the as measured data base, corresponding with the definition of RTTo. Thus the results also prove the validity of the KIc(RTTo)-curve for allowable flaw sizes and up to the crack length spectrum of the ASME KIC-data base without size adjustment of T0. The results of both investigations confirmed the validity of RTTo for German RPV steels.