Thermodynamics and transport processes in reactor fuel

Abstract

Chemical thermodynamics and transport processes are inextricably linked in light- water reactor fuel rods. Two regimes can be identified, separated by their temperatures. During normal operation, the temperature at the center of the UO2 pellet usually does not exceed 1000°C, and most of the important chemistry takes place at the periphery, which is separated from the Zircaloy cladding by a thin(tens of microns) gas-filled gap. The temperatures here are typically 350-600°C. In a serious accident resulting in loss of cooling water circulating in the reactor's primary circuit, severe fuel damage may occur. Conditions in this regime encompass temperatures from ~1000 to 3000°C, the state of water is steam rather than liquid, and the system total pressure may be as low as 1 atm. This paper reviews the important chemistry-transport phenomena that occur in the normal-operation and severefuel-damage regimes. © 1995 IUPAC