Development and test results of multi-axial stress testing machine for cladding

Fukuda, Takuji; Sugiyama, Tomoyuki ; Mihara, Takeshi  ; Amaya, Masaki  ; Nagase, Fumihisa 

The stress condition of the cladding tube of high burnup fuel is complicated under RIA (Reactivity Initiated Accident) condition because fuel pellet and cladding bond significantly in high burnup fuel. The stress condition becomes biaxial under such condition due to the isotropy of pellet thermal expansion. We have developed a biaxial stress testing machine which can control the axial and circumferential stresses independently and evaluate the mechanical and fracture behaviors of cladding tube under biaxial stress condition. This report describes the outline of the experiment using this equipment and the test results obtained under several biaxial stress conditions at room temperature.