TRANSIENT FUEL PIN TEMPERATURE CALCULATIONS USING DESCRIBING FUNCTIONS.
Academic Article

Overview

Overview

abstract

An analytically based method is presented in which the transient temperature profiles are calculated using describing functions to characterize the system nonlinearities. The solution is a three step process. First, definitions are made of the integral conductivity and the integral heat capacity. This permits the governing equation to be recast as a linear partial differential equation in which the integral thermal properties are the two dependent variables. Second, mathematical integral transforms are used to obtain an algebraic equation in the transformed time-space domain. Because the resulting algebraic equation is still in terms of the two dependent variables, the third step is to relate these variables to each other using the describing function approach. Using this technique, a factor of 40 reduction in computer time was achieved over a similar finite element calculation for the study of fuel temperature response following a reactor scram. In addition, the approach is general and can be applied to other nonlinear partial differential equation systems.