Isotope effects on the physicochemical properties of zirconium hydride

Temperature dependence of misfit strains of δ-hydrides of zirconium

“…where, a and c are the lattice parameter in nm, the superscript over a and c represent the phase, T is temperature in K, x is the atomic fraction of hydrogen or deuterium with 1.5 ≤ x ≤ 1.7 and the symbols H and D representing the corresponding hydride , fcc ␦-ZrH 1.66 [15] and fcc ␦-ZrD 1.66 [16].…”

“…The polynomial expression, represented by Eqs. (1)- (4), describes the variation in lattice parameter of ␣-Zr [11,14], fcc ␦-ZrH x [15] and fcc ␦-ZrD x [16] with temperature in the temperature range of 298-773 K.…”

“…Using room temperature lattice parameter of hexagonal close packed (hcp) ␣-Zr [11] and face centered cubic (fcc) ␦-ZrH 1.66 [12], Carpenter [13] calculated the dilatational misfit strains of zirconium hydride precipitated in zirconium. However, the lattice parameter of both ␣-Zr [14] and ␦-ZrH x [15] is reported to be influenced by temperature and composition [15,16], and hence is likely to influence the stress free transformation strains. Also, for a given concentration of hydrogen isotope, the lattice parameter of ␦-ZrD x [16] is reported to be smaller than that of ␦-ZrH x [15], suggesting that the misfit strains associated with accommodation of ␦-ZrD x [16] could be smaller than that for ␦-ZrH x [15].…”

“…Though under normal operating condition Zr-alloy components are exposed to temperatures around 573 K, under accidental condition it may be exposed to higher temperatures. Also, misfit strains at higher temperature are required to rationalize the threshold stress for reorientation of hydrides [7] and DHC velocity data [17] reported in literature at temperatures higher than 573 K. It may be noted that the lattice parameter of ␦-ZrH x [15] and ␦-ZrD x [16] are available only in the temperature range of 298-573 K and hence were extrapolated in order to determine the misfit strains at higher temperatures. The misfit strain data reported in the present work is valid for the temperature range of reactor operation and can be used in refining various hydride embrittlement models [8][9][10], i.e.…”

“…The temperature dependence of misfit strains of ␦-ZrH x and ␦-ZrD x were determined from the lattice parameters of ␣-Zr [14], ␦-ZrH x [15] and ␦-ZrD x [16] in the temperature range of 298-773 K and for 1.5 ≤ x ≤ 1.7. We have used the methodology proposed by Carpenter [13] to compute the mis-fit strains.…”