[2F10-16] Thermal Hydraulics at Accidents

[2F16] Study on Air Ingress Phenomena during a Depressurization Accident of VHTR

(2)Discussion on Onset Time of Natural Circulation

*Tetsuaki Takeda¹ (1. University of Yamanashi)

Keywords:VHTR, depressurization accident, air ingress, natural circulation, molecular diffusion

A depressurization accident is the one of the design-basis accidents of a Very-High-Temperature Reactor (VHTR). When the depressurization accident occurs, air is expected to enter into the reactor pressure vessel from the breach and oxidize in-core graphite structures. In order to predict or analyze the air ingress phenomena during the depressurization accident, therefore, it is important to develop the method for prevention of air ingress during the accident. This paper describes the process of air ingress and the onset time of natural circulation of mixture gas during the depressurization accident.