Radiation Effects in Zirconium Alloys

Irradiation Induced Defect Clustering in Zircaloy-2

“…Alloying elements Zircaloy-2 contains 1.5 wt % Sn, 0.15% Fe, 0.1% Cr, and 0.05% Ni and 1000 wppm oxygen. From EDS element maps (Cr, Fe, Ni, O, Sn, Zr, and Cr + Ni) in Figure 1, Sn mostly remains in solid solution in the α-phase, O in the α-phase, and slightly enriched in intermetallics, whereas the other alloying elements are mostly contained in intermetallic precipitates: Zr(Fe,Cr) 2 and Zr 2 (Fe,Ni). Figure 1 indicates these precipitates mostly with irregular shape, in sizes from 100 nm to~1 µm.…”

“…The fundamental mechanism of these degradations is neutron induced atomic displacement in alloys. One of most important damage microstructures is called a "dislocation loop", which evolves from atomic displacement cascades [2]. The study of the dislocation loop evolution of Zr alloys under irradiation is of active interest.…”

“…Compared to the pure Zr composition, it is reasonable to assume that Sn is the most important alloying element causing the differences observed between the defect nucleation in pure Zr and Zirclaoy-2 at lower doses where irradiation induced dissolution of Fe and Cr from the intermetallics will be negligible. At higher doses, both Fe and Cr diffuse from the intermetallic precipitates into the alpha Zr matrix through an interstitial diffusion mechanism at similar diffusion rates and can alter the microstructural evolution mechanisms significantly [2,10].…”

“…The study of the dislocation loop evolution of Zr alloys under irradiation is of active interest. In Zr alloys, prismatic (<a>-type) dislocation loops are the basic and most well-known component of radiation damage structures and are observed in a wide range of irradiation temperatures (80-500 • C) [2]. These loops are visible at lower to higher neutron doses, with densities saturating at relatively low doses, and have been extensively studied by neutron, charged particle irradiation, and MD simulations [2][3][4][5][6][7][8].…”

“…In Zr alloys, prismatic (<a>-type) dislocation loops are the basic and most well-known component of radiation damage structures and are observed in a wide range of irradiation temperatures (80-500 • C) [2]. These loops are visible at lower to higher neutron doses, with densities saturating at relatively low doses, and have been extensively studied by neutron, charged particle irradiation, and MD simulations [2][3][4][5][6][7][8]. It has been reported that the point-defect clusters formed in Zircaloy-2 at temperatures between 250 and 400 • C and for irradiation doses lower than 5 × 10 25 nm −2 (E > 1 MeV), which can be observed by using transmission electron microscopy (TEM) (>2 nm), and consist of perfect dislocation loops, either of vacancy or interstitial nature, with Burgers vector of temperature [9,10].…”