Bulk-nanocrystalline oxide nuclear fuels – An innovative material option for increasing fission gas retention, plasticity and radiation-tolerance

• Published in: Journal of nuclear materials Vol. 422; no. 1-3; pp. 27 - 44
• Main Authors: Spino, J., Santa Cruz, H., Jovani-Abril, R., Birtcher, R., Ferrero, C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.2012; Elsevier
• Subjects: Applied sciences; Controled nuclear fusion plants; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Fuels; Installations for energy generation and conversion: thermal and electrical energy; Kapitza resistance; Nanostructure; Nuclear fuels; Plasticity; Porosity; Preparation and processing of nuclear fuels; Stresses; Thermal properties; Zirconium dioxide; Grain size; Swelling; Nuclear fuel; X ray; Clad; Light water reactor; Thermal stability; Grain boundary; Nuclear reactor; Thermal properties; Radiation resistance; Ion irradiation; Thorium oxide; Synchrotrons; Tomography; Porosity; Uranium dioxide; Fission gas; Melting point
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2011.11.056

Advantages and disadvantages of bulk nanocrystalline (nc)-oxides (UO2, ZrO2, ThO2) and suggestions for their potential use as nuclear fuels and inert matrix carriers are described in this work on the basis of a study with nc-4mol% Y2O3–ZrO2 bodies, which are envisaged to behave akin to highly exposed LWR-fuels with the High Burn-up Structure (HBS) also known as rim transformation. The main attributes of nc-fuels in-pile compared to conventional fuels will be the capacity to develop closed porosity retaining most of the fission gases, the ability to relax more efficiently the interaction stresses with the cladding (through much higher plasticity) and the enhanced resistance against radiation-damage thanks to their nanostructure. The present analysis comprises the long-term thermal stability of a porous nc-material, its property vs. porosity relations, the topology of the pore phase via X-ray synchrotron tomography, the behaviour under compressive stress and the performance under intense Xe-ions irradiation. Salient outcomes are the non-connectivity of the pore phase, the superplasticity of the nc-bodies and their high radiation–amorphisation resistance with negligible swelling under Xe-bombardment. Another important outcome of the present study is that deterioration of the thermal properties due to grain boundary effects (Kapitza resistance, melting point depression) can likely be avoided if the grain size is kept above 100nm and, emulating the real HBS material, preferably in the range between 200 and 300nm.