Basic Properties of a Zirconia-Based Fuel Material for Light Water Reactors

Abstract

The properties of zirconia cubic solid solutions doped with yttria, erbia, and ceria or thoria are investigated with emphasis on the potential use of this material as an inert matrix for Pu incineration in a light water reactor. The material is selected on the basis of its neutronic and chemical properties; Zr and Y are not neutron absorbers. Among the rare-earth elements, Er was identified as a suitable burnable poison and was found to be the best among the rare-earth elements. The high-density cubic solid solution is stable for a rather large range of compositions and from room temperature up to ~3000 K. The selected zirconia-based material has rather low heat conductivity (~2 W·m-1·K-1) compared to UO2, and the annular pellet design was consequently suggested to overcome this low-energy transfer characteristic. Samples irradiated with low- and high-energy Xe ions up to a fluence of 1.8 × 1016 Xe·cm-2 were investigated by transmission electron microscopy. Low-energy (60-keV) Xe ions did not produce amorphization. From the observed bubble formation, swelling values during irradiation at room temperature and at high temperature (925 K) were estimated to be 0.19 and 0.72% by volume, respectively. Furthermore, no amorphization was obtained by Xe irradiation under extreme conditions such as high-energy (1.5-MeV) Xe ion irradiation and low temperature (20 K). This confirms the robustness of this material and argues in favor of the selection of a zirconia-based material as an advanced nuclear fuel for Pu incineration.