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Proceedings of the 27th National and 5th International ISHMT-ASTFE Heat and Mass Transfer Conference December 14-17, 2023, IIT Patna, Patna-801106, Bihar, India
December, 14-17, 2023, Bihar, India

Evaluation of Molten Fuel Droplets Size Distribution in a Fuel Bubble under Energetic CDA in SFR

Get access (open in a dialog) DOI: 10.1615/IHMTC-2023.2020
pages 1237-1242


In the event of energetic core disruptive accident (CDA) in Sodium Fast Reactor (SFR), a high-enthalpy meta-stable molten fuel pool is formed. The fuel pool expands into the overlaying sodium pool as a two-phase bubble, and transports radioactive fragmented fuel particles from the disrupted core, contributing to the radiological source term. In this regard, the two phase flow regimes and the fuel droplet size distribution inside the expanding meta-stable fuel bubble are evaluated. The two-phase flow regime transition criteria are based on the fuel bubble-sodium pool peak interface velocity. The fuel droplet size distribution is evaluated using a tri-linear model. The tri-linear model evaluates the droplet Sauter Mean Diameter (SMD) by accounting for both mechanical and thermal fragmentation mechanisms and describes the particle sizes of a superheated liquid using the Rosin-Rammler size distribution. Results show that the minimum bubble interface velocity required for the existence of droplet regime inside the expanding fuel bubble is 10 ms-1, which is significantly lesser than the peak bubble-coolant interface velocity when the initial fuel bubble temperatures are between 4200 K and 4700 K. The SMD of fuel droplets for the above temperature range is between 370 µm and 25 µm. These results are an essential consideration in the analysis of fuel dispersion related to the analysis of in-vessel actinide radiological source term under energetic CDA conditions in SFR.