Multi-component diffusion analysis and assessment of GAMMA code and improved RELAP5 code

Development and validation of a model for the chemical kinetics of graphite oxidation

“…1 can form a hexagonal d-lactone ring with an embedded oxygen atom between carbon atoms (1) and (2) [30]. The carbonyl complexes of ketones, aldehydes, carboxylic acids and acid anhydrides would form on the conventional zig-zag sites (3) and (4), or on the corner sites (10) and (11) (Figs. 1 and 2).…”

“…Several oxidation models have been developed for the analysis of steam ingress [3][4][5][6] and air ingress accidents in HTRs [7][8][9][10][11][12]. These models typically employ control-volume or finite-elements techniques to solve the multi-dimensional flow, mass transport and energy equations.…”

Scaling and design analyses of a scaled-down, high-temperature test facility for experimental investigation of the initial stages of a VHTR air-ingress accident

“…Initially, the air-ingress mechanism was considered to be controlled by molecular diffusion when a one-dimensional (1D) numerical tool was used in the analysis (Oh et al, 2006;Hishida and Takeda, 1991;Takeda and Hishida, 1996;Kim et al, 2008;No et al, 2008). According to these studies, when the air-ingress speed is controlled by molecular diffusion, governed by Fick's law, the onset of global natural circulation in the reactor vessel takes on the order of 100 hours to occur after the break is initiated.…”

Computational Fluid Dynamics Analyses on Very High Temperature Reactor Air Ingress

“…The scenario is depicted in Figure 1. Earlier studies of the mechanisms leading to air ingress into the reactor vessel were focused on diffusion [2,3,4,5] as described by Fick's Law and ignored the effects of density gradients on the interactions between helium (low density) and air or helium-laced air (high density) flow.…”

“…If the stratified air flow induces the natural circulation flow to begin earlier than previously thought, the time frame for graphite oxidation will occur earlier and at a more rapid rate. Earlier predictions from the GAMMA code [5] predict oxidation between 150 and 200 hours following pipe rupture, depending on the initial air volume in the containment. Calculations using MELCOR predict that oxidation begins at 220 hours [7] following pipe rupture.…”