Best-estimate calculations of realistic source terms are presented that reduce uncertainties in predicting volatile fission product release from the UO2 fuel over the temperature range from 770 to 2500 K. The proposed method of correlation includes such fuel morphology effects as equiaxed fuel grain growth and fuel/cladding interaction. The method correlates the product of fuel release rate and equiaxed grain size with the inverse fuel temperature to yield a bulk mass transfer correlation. It is found that fewer and slower releases are predicted utilizing the bulk mass transfer correlation than with the steam oxidation model and the U.S. Nuclear Regulatory Commission’s NUREG-0956 correlation. Computational modules are developed to perform the thermal-hydraulic and fission product calculations needed to analyze the severe fuel damage tests. The predictions utilizing the bulk mass transfer correlations overall follow the experimental time-release histories during the heatup, power hold, and cooldown phases of the transients. Good agreements are achieved for the integral releases both in timing and in magnitude. The proposed bulk mass transfer correlations can be applied to both current and advanced light water reactor fuels.