Shock Compression, Adiabatic Expansion and Equation of State of Uranium Dioxide

Equation of state for matter over wide range of pressures and densities is interesting for modeling of physical phenomena in shock-compressed media. In the present study we have obtained data on the shock compressibility of porous uranium dioxide UO$_2$ samples with initial densities 4.25 and 2~g/cc up to pressures $P \approx 82$~GPa. We have also measured states of UO$_2$ samples in adiabatic release waves using barrier technique down to $P \sim 0.05$~GPa. We propose a semiempirical equation of state $E(P,V)$ for UO$_2$ optimally generalized the newly acquired and available at high energy densities experimental data. The equation of state obtained has a simple analytical form $P=P(E,V)$ and it can be used efficiently in numerical simulations of shock-wave processes.