A two-dimensional experimental investigation on debris bed formation behavior

Studies on debris bed formation behavior are of crucial importance for the improved evaluation of Core Disruptive Accidents (CDA) that could occur for Sodium-cooled Fast Reactors (SFR). In this work, to clarify the mechanisms underlying this behavior, a series of experiments was performed by discharging solid particles into two-dimensional rectangular water pools. To obtain a comprehensive understanding, various experimental parameters, including particle size (0.256∼8 mm), particle density (glass, alumina, zirconia, steel and lead), particle shape (spherical and irregularly-shaped), water depth (0-60 cm), particle release pipe diameter (10-30 mm), particle release height (110-130 cm) as well as the gap thickness of water tank (30-60 mm), were varied. It is found that due to the different interaction mechanisms between solid particles and water pool, four kinds of regimes, termed respectively as the particle-suspension regime, the pool-convection dominant regime, the transitional regime and the particle-inertial dominant regime, are identified. The performed analyses in this work also suggest that under present experimental conditions, the particle size, particle density, particle shape, particle release pipe diameter and water depth are observable to have remarkable impact on the above regimes, while the role of particle release height and gap thickness of water tank seems to be less prominent. Knowledge and data from this work might be utilized for the improved design of core catcher as well as analyses and verifications of SFR severe accident analysis codes in China in the future.