Molten salt reactors (MSR) produce off-gases containing chemically reactive and radioactive species necessitating effective

treatment to ensure operational safety and compliance with environmental regulations. This study examines the hydrodynamic

behavior and HCl capture performance of a bubble column-type molten salt scrubber designed for MSR off-gas treatment.

Flow regime transition from homogeneous to heterogeneous was identified at a gas velocity of 0.025 m/s in NaOH (51 mol%)-

KOH molten salt at 250 °C through gas holdup and drift flux analyses. HCl capture efficiency was assessed at 100 ppm HCl

inlet concentrations over gas velocities of 0.01–0.03 m/s and temperatures of 250–300 °C. In the homogeneous flow regime,

capture efficiency reached approximately 97% at 0.03 m/s, with minimal temperature dependence. Thermodynamic analysis

using HSC Chemistry indicated slight Gibbs free energy changes across the tested temperature range, with sequential formation

of KCl and NaCl as reaction products. Operating the bubble column-type molten salt scrubber in the homogeneous flow

regime optimizes capture efficiency and minimizes aerosol generation, enhancing nuclear safety and off-gas management

for sustainable MSR operations.