Radiative Heat Transfer in CANDU Channels Under Coolant Stratification Conditions

Abstract

A model is presented for performing radiative heat transfer calculations in a stratified CANDU reactor channel during accident conditions. A simple, but accurate, method for calculating and continuously updating radiative view factors between exposed fuel elements at varying coolant depletion levels is introduced. These view factors are incorporated into a first-neighbours matrix, which allows for simultaneous calculation of the temperature of all uncovered fuel elements exposed to steam in a small loss of coolant accident combined with loss of circulation. It is shown that a significant reduction in estimating the amount of radioactivity release (source term) is obtained by accurately performing the radiative heat transfer calculations.