[2E09-14] Fast Reactor Thermal Hydraulics

[2E11] Study on coolant behavior in damaged core of sodium-cooled fast reactor

(6)Local void fraction measurement by using X-ray imaging in simulated debris bed

*Noriaki Yasugi¹, Naoya Odaira¹, Daisuke Ito¹, Kei Ito¹, Yasushi Saito¹, Yuya Imaizumi², Kenichi Matsuba², Kenji Kamiyama² (1. Kyoto Univ., 2. JAEA)

Keywords:debris bed, packed bed of spheres, sodium-cooled fast reactor, air-water two-phase flow, void fraction, X-ray imaging

In case of a severe accident in a sodium-cooled fast reactor, the fuel debris formed in the core should be cooled stably and in-vessel retention of the damaged core material is important. It is considered that a gas-liquid two-phase flow is generated by boiling of the sodium inside the high-temperature debris bed. However, the two-phase flow characteristics in the debris bed has not been understood enough. Therefore, in this study, the two-phase flow in a packed bed is measured to improve the prediction accuracy of the two-phase pressure drop in the porous media. The local void fraction distribution of gas-liquid two-phase flow in the packed bed was measured by X-ray transmission imaging, and the local two-phase flow structure was evaluated.