Performance analysis of thoria based AHWR fuel

A major consideration in fuel design is to ensure clad integrity during its life. Fuel burnup and its linear power are the two most important parameters, which have an influence on its performance. Fission gas release is one of the most important life limiting phenomena, especially among those affecting extended fuel burnup. It is a complex phenomenon that is governed by various fuel related parameters like temperature, grain size, density, burnup, rim-effect, homogeneity etc. There are two major aspects, which provide thoria-based fuels an inherent advantage in terms of fission gas release over urania-based fuels. Thoria has a higher thermal conductivity resulting in lower fuel temperatures and a lower diffusion coefficient. Both these factors aid in lowering fission gas release. Thoria being a fertile material, requires addition of fissile material in the form of U233, U235 or Pu. Advance Heavy Water Reactor (AHWR) is a thoria based reactor with (Th-Pu) MOX and (Th-U233) MOX fuels. This paper brings out the performance analysis carried out for the thoria based fuels used in AHWR from fission gas release point of view. (author)