CFD investigating the air ingress accident occurred in a HTGR_simulation of thermal-hydraulic characteristics

The majority of this paper investigates thermal-hydraulic characteristics in a high-temperature gas-cooled reactor (HTGR) core under steady-state and accident conditions through a transient three-dimensional compressible CFD model. With the pebble-bed geometry, the HTR-10 core is selected for the present simulations. A loss-of-coolant accident (LOCA) with double-ended rupture of a gas duct tube is assumed and the core power would decay following this accident. In this LOCA, air in the steam generator cavity would enter the core via diffusion and natural convection mechanisms. Following air ingress into the core, O2 would react with graphite on pebble surface, causing the generation of CO2 and CO. The main thermal-hydraulic characteristics during this air ingress accident include O2 ingress into the core, CO2 and CO production histories, He concentration variations, and coolant temperature transient behavior, etc. Based on the present simulation results, the peak coolant temperature during the air ingress accident is slightly higher than that under the steady-state condition, revealing the safety of HTR-10 core in this postulated accident from the thermal point of view. In addition, corrosion phenomena related to the fuel pebbles are discussed and presented in the next paper.

► 3-D compressible CFD model is proposed to study air ingress phenomena for a HTR-10.
► A LOCA with a double-ended rupture of gas duck tube is assumed.
► In LOCA, air in the SG cavity enters the core via diffusion and natural convection.
► O2 will react with graphite on pebble surface, causing the generation of CO2 and CO.
► Peak coolant temperature during air ingress is slightly higher than that in the normal condition.