The WWER-440 V-213 type RPVs are equipped with the surveillance specimens used to predict the embrittlement of the RPV material. These specimens are located near the core, resulting in accelerated irradiation. After four years of operation only one overexposed set remains in each unit. To obtain a more extensive database for life time calculation and life time management, a new, more extended surveillance program has been elaborated and implemented. Due to the limited availability of archive materials reconstructed Charpy V specimens and small size smooth and notched tensile bars were used in the program. To develop this surveillance extension, an extensive laboratory study on use of reconstructed Charpy and subsize tensile specimens was performed. Methods for K1a measurements on small size specimens were also studied.
The results of experiments on Society of Automotive Engineers (SAE) 1043 steel show that the cyclic stress-strain response in small regions of a notched specimen is not necessarily the same as that obtained in tests on smooth specimens of the same metal. At the roots of notches (two different notch radii were used) plastic flow occurs at the same cyclic lives as in unnotched specimens, when the longitudinal total strains are similar. Cyclic plasticity develops in many fewer cycles near the notches than in smooth specimens under the same longitudinal total strains. The more sharply notched specimens soften more rapidly at locations near the notches than the less severely notched ones under identical longitudinal strains.
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