Thermalhydraulic and safety analysis of Uranium dioxide-Beryllium oxide composite fuel.

摘要

Addition of BeO to UO2 is known to enhance fuel thermal conductivity by a significant amount leading to drop in fuel temperatures. This study will focus on thermal hydraulic and safety analysis of the composite UO2 - 10% vol BeO. Fuel performance codes like FRAPTRAN and FRAPCON and thermal hydraulic code RELAP-5 are being used. FRAPTRAN is mainly used for transient analysis and it calculates parameters including fuel and cladding temperatures, cladding strain, rod gap pressures and energy stored in the fuel. FRAPCON is used mainly to study steady state long term behavior of fuels. It gives valuable information related to fission gas release and fuel creep. FRAPTRAN and FRAPCON calculate important material properties in subroutines and these properties are used for calculations involved in the analysis of fuel performance. To model performance of this composite, these material properties were modified for UO2-BeO based on data available and techniques used in literature along with few assumptions, due to limited availability of data. Modified codes were used to study behavior of the composite. Results reveal that significant reductions in fuel centerline temperatures, cladding strain, rod gas pressures and fission gas release are obtained for the composite fuel. This also helped in studying diffusion coefficient for the composite fuel. The thermalhydraulic code RELAP-5 was used to study temperature patterns, pressure, core water level and void fraction. Results from RELAP-5 show about 20% drop in fuel temperatures, which is in good agreement with those predicted by FRAPTRAN too. No major changes were observed in pressure and water levels, however, void fraction reduced by a small amount upon using the composite.