A Modal Method for Transient Thermal Analysis of CANDU Fuel Channel

Abstract

The classical modal expansion technique has been applied to predict transient fuel and coolant temperatures under on-power conditions in a CANDU fuel channel. The temperature profile across the fuel pellet is assumed to be parabolic and fuel and coolant temperatures are expanded with Fourier series. The coefficient derivatives are written in stare space form and solved by the Runge-Kutta method of fifth order. To validate the present mode!. the calculated fuel temperatures for several sample cases were compared with HOTSPOT-II. which employs a more rigorous finite-difference model. The agreement was found to be reasonable for the operational transients simulated. The advantage of the modal method is the fast computation speed for application to a real-time system such as the CANDU simulator which is being currently developed at the Institute for Advanced Engineering (IAE).