Hafnium dioxide for porous and dense high-temperature refractories (2600 °C)

Abstract

The VERDON project is devoted to the studies of fission products release in a hypothetical case of severe accident in a pressurized water reactor (PWR). The experiments will be performed on irradiated nuclear fuels: the fuel rod is heated with an induction furnace up to the melting point of the irradiated fuel (about 2600 °C). This furnace must be thermally isolated and some parts must resist to interaction with corium (magma of nuclear fuel and cladding) during a limited time. The refractory pieces needed to VERDON facility (dense and porous) are the subject of this work. The dense pieces are made of hafnium dioxide doped with yttrium oxide in order to avoid cracking due to a phase transition which generates an important volumetric expansion. The ceramics obtained after sintering are dense (90%) and present mainly closed porosity. The porous pieces are prepared from a mixture of hafnium dioxide and a porous agent. After sintering, these pieces keep a satisfactory porosity (30–50 vol%) and do not crack during the phase transition.