Lumped and distributed models for The study of thermal behavior of nuclear fuel rods

This work focuses on the proposition and analysis of simplified methodologies and formulations to transient temperature field determination in nuclear fuel pellets, emphasizing the use of nonlinear thermophysical properties identified in the characterization of this class of material. The main objective of the work is to offer more accurate analytical and computational alternatives than the Classical Lumped System Analysis (CLSA) but with similar computational costs. The CLSA is usually applied in research simulations and even in commercial computational codes in the study of nuclear reactors. A distributed parameter model is proposed applying the Generalized Integral Transform Technique (GITT), offering hybrid numerical-analytical solutions. Different procedures of integral transform application were proposed and reviewed, after nonlinearity concentration on the transient term by Kirchhoff transformation. The results of the proposed models were bench marked by a numerical solution of the distributed parameter formulation and applied in nuclear reactor engineering cases. (author)