Numerical analysis on thermal-hydraulic and dust transport behavior in fusion reactors at loss-of-vacuum events

Thermal-hydraulic and dust transport behavior in a fusion reactor during a loss-of-vacuum (LOVA) event was analyzed numerically using a newly developed 3-D analysis code under a compressible flow and 3-D cylindrical coordinates conditions from the viewpoint of the thermofluid safety of the fusion experimental reactors. After the LOVA event occurs, air will flow from the outside of a vacuum vessel (VV) through a breach into the inside and the activated dust accumulated in the VV may be blown up from the floor and spread throughout the whole area of the VV. From the predicted results, velocity, pressure and temperature distributions in the VV at the LOVA event were clarified quantitatively by 3-D computations. The predicted average pressures inside the VV were in good agreement with the experimental results from vacuum to atmospheric pressure. In addition, the dust transport behavior in the VV at LOVA conditions was visualized numerically. A cluster of dust particles was initially set on the floor of the VV and the breach was suddenly opened. The dust particles were transported from the floor to the inside of the VV by the external fluid through the breach. Almost all of the dust were deposited on the wall over a long period of time, but some of those were entrained to the outside of the VV as a result of the exchange flow and the rest was deposited onto the side walls and penetrations in the VV.