Effect of temperature and hydrogen concentration on the threshold stress intensity factor of radial delayed hydride cracking in fuel cladding

Three-point bending tests provide the ability to measure propagation of axially oriented cracks in thin-walled fuel cladding a radial outside-in direction. Via three-point bending, unirradiated Zircaloy-2 containing 155 and 305 wppm hydrogen was mechanically loaded at different temperatures, sufficient initiate delayed hydride cracking (DHC) whereupon unloading rate fast enough arrest further propagation. The crack front dimensions were measured through fractography implemented with final load into finite element model (FEM). Given average length load, FEM able back-calculate stress intensity factor. Over temperature range 210–330 °C, around 6 MPa√m calculated as minimum threshold factor for DHC. trend shows that ideal DHC lowest factors may depend on concentration, quickly increase higher test temperatures. It has also been shown creep affects optimal less lower concentrations than concentrations. At low terminal solid solubility precipitation (TSSP) is so creep-induced tip rounding plays significant role compared kinetics.