부산대학교 도서관

Comprehensive crack initiation and crack arrest tests were performed, up to neutron fluences far beyond the end of life range, on irradiated original reactor pressure vessel (RPV) steel specimens from German pressurized water reactors (PWR). The neutron fluences applied to the specimen materials under light water reactor conditions were between 5.44 × 1018n/cm2 and 7.67 × 1019n/cm2 (E > 1 MeV) with a neutron flux from 2.64 × 1010n/cm2s to 2.55 × 1012n/cm2s. The objective was to extend the already existing experimental database to reach a final comparative assessment of both the RTNDT and the RTT0 (Master Curve) concepts for proof of sufficient margin against RPV brittle fracture and to assess the impact of important factors such as neutron flux, manufacturing effects and specific irradiation effects such as late blooming effects. The test data show that most of the measured fracture toughness data are enveloped by the “lower bound” ASME KIc-curve for crack initiation and that the RTT0 concept compared to the RTNDT concept leads to lower reference temperatures for the base materials. However, for the weld materials, the general trend of RTNDT > RTT0 is less or not at all pronounced. It was also found that the measured ΔT41 and ΔT0 data show a good correlation and that the RTT0 of heat affected zone (HAZ) materials is lower compared to the base materials. Finally, the applicability of both the RTNDT and the Master curve concepts for crack arrest was confirmed, except the alternative use of RTT0 for indexing of the KIa fracture toughness curve could not be confirmed by the measured data. The application of a so-called duplex specimen geometry for crack arrest testing led to essential improvements; however, further optimizations of the specimens’ fabrication process are still recommended. Finally, the complete database is assessed with respect to benefits for future RPV safety analyses.