Below a few eV, interactions of neutrons with zircaloy-4 depend on the structure of the material and of the dynamics of each atom in the crystal, which are described by the lattice parameters and the phonon density of states, respectively. Despite the numerous works performed on zircaloy-4, the systematic variation of the lattice parameters up to normal pressurized water reactor (PWR) operating conditions was never explicitly reported in the literature. Similarly, it was not possible to find studies reporting any theoretical of experimental phonon density of states for zircaloy-4. The goal of this study is to provide the variation of the lattice parameters of α-Zr in zircaloy-4 as a function of nuclear fuel burnup in the temperature range over which the hexagonal phase exists. For that purpose, lattice parameters for low-hydrogenated Zy4 samples have been determined thanks to new diffraction experiments performed with the D1B instrument of the Institut Laue-Langevin (ILL, Grenoble, France) from 2 to 300 K. Past neutron diffraction experiments carried out with the D20 instrument were used to provide consistent lattice parameters from 300 to 700 K. Then, irradiation growth of zircaloy-4 under neutron irradiation was added as correction factors by using results reported in the literature. Parallel inelastic neutron scattering experiments were also performed on the IN5 and IN6 time-of-flight spectrometers in order to measure the phonon density of states of zircaloy-4 at room temperature for its subsequent use in the calculation of the Debye-Waller coefficient and Debye temperature which are involved in the determination of the lattice parameters.