A Novel In-situ Miniature Creep Tester for Evaluation of New Cladding Alloys

The next generation of nuclear reactors aims to enhance the efficiency of thermal power generation. However, the high temperatures and radiation levels within the reactor require the development of new cladding alloys with good mechanical properties at elevated temperatures. In particular, understanding the creep and creep-fatigue performance and the associated damage mechanisms is paramount for ensuring structural safety. Despite significant advancements in cladding alloy design, progress in developing new alloys is slow due to the limited availability of materials during the development phase for performance evaluation. This scarcity restricts the number of testing samples obtained from a single batch, hindering the evaluation and rapid enhancement of material design and performance. Employing miniature sample testing addresses the limitations of available material volume during alloy development. Additionally, the small specimens can undergo irradiation experiments to investigate damage effects. However, a critical impeding is the lack of specialized equipment to conduct mechanical tests on small samples. No commercially available test system can perform in-situ SEM high-temperature creep tests on miniature samples for real-time characterization. To address this gap, a novel creep tester capable of performing in-situ tests within an SEM is developed. This presentation discusses the challenges in developing the miniature test equipment and highlights its capabilities. The results of ex-situ and in-situ tests on small-scale samples of SS316 and alloy Kanthal APMT are presented, emphasizing efforts to bridge the gap between small and conventional specimen data. In addition, we discuss material characterization and computational models used to simulate the viscoplastic response.