Byung Jun Kim

Evaluation of impact properties of weld joint of reactor pressure vessel steels with the use of miniaturized specimens

The effects of specimen size and location of V-notch on the Charpy impact properties were investigated with different sizes of specimens, standard, CVN-1/2, CVN-1/3, and CVN-1.5 mm, for A533B steel, low Mn, high Cu, high phosphorus (P), and high Cu/P steel weld joint. A part of the specimens was irradiated with neutron at 563 K up to 8 × 1019 n/cm2. The heat affected zone (HAZ) specimen is the best in the impact properties among the specimens of base metal, HAZ, and weld metal in the steels with 0.003 wt.% P, while it is the worst in the steels with ∼ 0.3 wt.% P. This indicates that the surveillance test of HAZ specimen can be represented by base metal in the case of A533B steels with lower P content (∼ 0.003 wt.%). The effects of notch location and chemical contents on ductile to brittle transition temperature (DBTT) are almost independent of specimen size within an error of ±5 K, indicating that the miniaturized Charpy specimens are applicable and effective in the surveillance tests of reactor pressure vessel steel of extended operation period. After irradiation, the highest DBTT was observed for the specimen with V-notch in base metal in the case of A533B steel and high Cu steel with 0.003 wt.% P.

Specimen Size Effects on Fracture Toughness of F82H Steel for Fusion Blanket Structural Material

Fusion energy has been considered to contribute to reducing emission of carbon dioxide effectively. Understanding and evaluating the fracture toughness behavior of neutron-irradiated reduced-activation ferritic (RAF) steels are essential in the design and operation of fusion reactor. In order to produce an enough database of irradiation effects on materials, the reduction of the specimen volume is required to acquire an enough number of data points. In the ITER Broader Approach (BA) project, applicability of small specimen test techniques (SSTT) has been examined to evaluate irradiation-induced degradation of fracture toughness of F82H steel. The master curve method, which was provided by the American Society for Testing and Materials (ASTM), is specified as a standard test method for determination of reference temperature for ferritic steels in the transition range. Fracture toughness tests were carried out for F82H steel in order to evaluate the effects of specimen size on the shift of transition curve using the various sizes of specimens (1 CT, 1/2 CT and 1/4 CT). The master curve approach was made for evaluation of fracture toughness of F82H with subsized specimens with constraint loss by referring to the ASTM E1921. Small specimen tests can be applicable to evaluate the fracture toughness of F82H steel with no substantial effect of specimen size.

Development of Small Specimen Technique to Evaluate Ductile–Brittle Transition Behavior of a Welded Reactor Pressure Vessel Steel

Small specimen test techniques (SSTT) for the evaluation of irradiation embrittlement of reactor pressure vessel steel (RPVS) is considered to be essential to operate light water reactors over 40 years old. In this research, specimen size effects were investigated for RPVS to apply small specimen test technique to surveillance test method. Specimens used in this study were machined from a welded A533B steel plate for RPV. Different size of specimens, Standard, CVN-1/2, CVN-1/3, and CVN-1.5 mm were fabricated from the weld bond. It was found that the ductile-to-brittle transition temperature (DBTT) and upper shelf energy (USE) were reduced by decreasing specimen size. The effect of notch position on DBTT was independent of specimen size.