Determination of fracture strength of δ-zirconium hydrides embedded in zirconium matrix at high temperatures

A review on hydride precipitation in zirconium alloys

“…They came to the conclusion that improvement in fracture toughness of Zr-2.5 wt% Nb above 150 C is more related to the reduction in the yield stress of the Zr phase than to any improvement in the hydride phase; because, the lower yield stress of the Zr phase prohibits reaching any stress level large enough to fracture the hydride phase. A recent study by Kubo et al [63] found that ductile fracture occurs above 200 C, because of a lower ultimate tensile strength of the Zr matrix, which confirms the work done previously by Simpson and Cann [62]. The ductile to brittle transition temperature of Zr has been shown to be directly correlated to the precipitation of hydrides by Huang and Ho [64], and although brittle fracture at room temperature was only seen in Zr with over 2000 ppm of H, a noticeable loss of ductility was seen Fig.…”

Homogeneous hydride formation path in α-Zr: Molecular dynamics simulations with the charge-optimized many-body potential

“…The δ hydride has a face-centered-cubic (fcc) structure, with a stoichiometry close to ZrH 1. 6 . For the ǫ hydride, the structure is also fct but with c < a. we note that here the structures of hydrides are defined based on the Zr lattice.…”

“…Under tensile stress, hydrides precipitate into a geometry with the hydride/matrix interface normal to the principle stress direction. The interface can serve as an easy fracture path [6]. Even under stress levels much lower than the fracture stress, hydrides may still cause cladding failure via so-called delayed-hydride-cracking (DHC) [7], which is one of the primary concerns for the safety of fuel pins during used fuel disposition and transportation [1].…”

Anisotropic hydrogen diffusion in α-Zr and Zircaloy predicted by accelerated kinetic Monte Carlo simulations

“…Hydride formation can detrimentally affect the cladding integrity primarily in two ways. First, the formation of hydrides reduces the fracture toughness of the cladding matrix78, increasing the probability of fuel failure when fuel-cladding mechanical interaction (PCMI) occurs during fuel operation. Second, upon cyclic thermal and mechanical loadings, hydrides can dissolve and reorient.…”