A Numerical Investigation of Coolant Thermal Mixing within 28-Element CANDU Fuel Bundles using ASSERT-PV

Abstract

This paper presents the results of a study of the thermal mixing of single-phase coolant in 18-element CANDU fuel bundles under steady-state conditions. The study, which is based on simulations performed using the ASSERT-PY thermal hydraulic code, consists of two main parts. In the first part the various physical mechanisms that contribute to coolant mixing are identified and their impact is isolated via ASSERT-PV simulations. The second part is concerned with development of a preliminary model suitable for use in the fuel and fuel channel code FACTAR to predict the thermal mixing that occurs between flow annuli.