Development and Validation of a New Gas Conductance Model

Abstract The analysis of fuel rod behavior has become increasingly important and reliable assessment of temperature distribution is vital. Gap conductance is a key parameter to calculate the heat transfer between fuel pellet and cladding, then fuel temperature and thermo-mechanical of fuel rods will be influenced. Gas conductance often plays the most important role comparing convective heat transfer, thermal radiation and solid contact conductance in fuel rod analysis. A new gas conductance model has been proposed, considering the effects of mixture gaseous component, the temperature discontinuity on the surfaces of pellet and cladding, and the roughness of solid surface, since the irregularity will become significant when the gap is closed at the extended burn-up. Moreover, the model has been calibrated with Modified Pulse Design (MPD) and Modified Longitudinal Design (MLD) experiment gas conductance data performed by John. E. Garnier and Stefan. Begej, and shown a good prediction accuracy at various experiment conditions. Furthermore, the model has been successfully implemented in fuel rod performance analysis code JASMINE to improving the temperature distribution prediction. Based on the comparison of code prediction of centerline temperature with HALDEN in-core irradiation tests data, the results show that the new gas conductance model has a decent suitability to JASMINE.