Validation of CATHENA Fuel Channel Model for Post Blowdown Analysis Against CS28-1 Experiment, II - Transient

Abstract

To form a licensing bases for the new methodology of fuel channel safety analysis code system for CANDU-6, a CATHENA model for the post-blowdown fuel channel analysis has been developed, and tested for a high temperature thermal-chemical experiment CS28-1[1].

Pursuant to the objective of this study the current study has focused on understanding the involved phenomena, their interrelations, and how to maintain good accuracy in the temperature and H₂ generation rate prediction without losing the important physics of the involved phenomena.

The transient simulation results for the FESs of three fuel rings and the pressure tube were quite good as proven in the Figs. 3~6. However this raises a question how the transient FES and pressure tube temperature can be predicted so well in spite of the insufficient justification of using the “non-participating medium assumption” for the CO₂ gas gap. Through this study, it was found that the radiation heat transfer model of CATHENA among FES of three rings and the pressure tube aa well as the exothermic metal-water reaction model based on the Urbanic-Heidrick correlation are quite accurate and sound. Also it was found that an accurate prediction of the initial condition of the experiment is very important for the accurate prediction of the whole transient as it serves as the starting point of the transient.