Studies on the primary pipe rupture accident of a high-temperature gas cooled reactor

In order to investigate the air ingress process during the early stage of the primary pipe rupture accident, experimental and analytical studies are performed on the conjugate phenomenon of transient molecular diffusion and natural convection of two component gas mixtures. The studies are carried out in two test sections, a reverse U-shape tube and a test model simulating simply the reactor of HTTR, which is being developed in Japan. The calculation is in good agreement with the experiment on gas concentration change and the initiation time of ordinary natural convection of pure N2 gas in the reverse U-shape tube. Mass transfer between a high temperature graphite tube and a stream of He-O2 gas mixture is experimentally studied in order to investigate the corrosion phenomenon of graphite structures in a high temperature regime during the later stage of the accident. (orig.)