Equation of state of non irradiated UO2

UO2 saturated vapour pressure curve points (P versus T) have been determined by in-pile experiments. An UO2 disk with a few tenths mm thickness is heated by fissions in a pressure cell. The power generated in the sample is proportional to the reactor one, measured by an ionization chamber, and the total energy deposition during the transient is measured on the fuel by γ spectrometry with a Ge-Li detector counting the fission products after the experiment. The experiments have been interpreted by using the assessed equilibrium value of specific heat. The results are consistent with the literature data for pressures less than 10 bars and lead to higher boiling temperatures than previous measurements of Ohse, Benson and Reil in the 20 - 250 bars pressure range