Critical analysis of the mini-CT geometry for fracture toughness characterization of the 73W high-copper submerged-arc weld in the unirradiated and irradiated condition

Fracture toughness measurement using miniaturized specimens such as the mini-CT is gaining a lot of acceptance worldwide. This was recently acknowledged by the multiple organizations participating to the EU H2020 FRACTESUS project that SCK CEN is coordinating. One of the key materials used within this project and that will serve as a benchmarking material is the 73W weld of the 5th HSSI program performed at ORNL in the late 90′s for an extensive well-controlled characterization in both unirradiated and irradiated condition. From the remaining broken specimens, a large number of mini-CT specimens were fabricated and tested. This paper addresses a number of key questions, among which the effect of geometry, testing conditions and master curve evaluation as compared to the original data obtained on large CT specimens at ORNL. The test results are analyzed for master curve evaluation according to the ASTM E1921-22 standard and further discussed to assess the applicability of this mini-CT geometry as an irradiation damage metrics but also for evaluating the lower bound fracture toughness curve.