A Spatial Convergence Study for Flows and Hydrogen Distribution in the CANDU 6 Reactor Vault following a Loss of Coolant Accident using the Gothic Containment Analysis Code

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Tuan H. Nguyen
W.M. Collins

Abstract

During a LOCA (Loss of Coolant Accident) coincident with Loss of Emergency Core Cooling OX)ECC) hydrogen can be generated in the fuel channels by the metal water reaction due to fuel channel heat up. The generated hydrogen subsequently flows out of the break and into containment. It is important to predict the ensuing hydrogen concentration in containment in order to identify potential flammable mixtures and to identify locations of possible mitigation devices. As a starting point, a 3D model of the reactor vault is required to properly capture the thermal hydraulic behaviour in this area especially the predicted flows in the area where the break is postulated to occur. In this study only the accident vault was represented in 3D with the remainder of containment being treated as a lumped node connected to the accident vault. This work is the second of four integrated tasks leading to the development of a hybrid containment model for the CANDU 6 reactor. A spatial convergence study is performed to ensure the validity of the selected 3D grid. Flows and hydrogen concentrations at various locations were compared for the two grids and conclusions have been drawn regarding the adequacy of the grids employed.

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