Thermodynamic and transport properties of thoria-urania fuel of Advanced Heavy Water Reactor

High temperature thermochemistry of thoria-urania fuel for Advanced Heavy Water Reactor was investigated. Oxygen potential development within the matrix and distribution behaviors of the fission products (fps) in different phases were worked out with the help of thermodynamic and transport properties of the fps as well as fission generated oxygen and the detailed balance of the elements. Some of the necessary data for different properties were generated in this laboratory while others were taken from literatures. Noting the behavior of poor transports of gases and volatile species in the thoria rich fuel (thoria-3 mol% urania), the evaluation shows that the fuel will generally bear higher oxygen potential right from early stage of burnup, and Mo will play vital role to buffer the potential through the formation of its oxygen rich chemical states. The problems related to the poor transport and larger retention of fission gases (Xe) and volatiles (I, Te, Cs) are discussed.