Study of Graphite Dust Releasing Behavior in a Depressurization Accident of HTR

The behavior of the graphite dust has an important effect on the safety analysis of High Temperature Gas-cooled Reactors. The graphite dust with the large size will deposit at the bottom of the reactor core by gravity, while the graphite dust with the small size will flow in the primary circuit by carrying of helium. These suspended dusts can deposit in primary loop surface and influence the surface’s feature such as fouling resistance. Moreover, fission products released by fuel elements would enter primary loop and combine with dust, resulting in making the maintenance and repair of steam generator difficult. On the other hand, in the loss-of-coolant accident, when the discharge pipe of fuel pellets was broken, helium will be rejected with the speed of sound. The graphite dust with radioactive contamination will be carried by helium into the environment. The present study experimentally investigates the resuspension of graphite dust in the process of depressurization accident. The effect of both the initial pressure and the velocity of the gas on the resuspension of graphite dust were studied.