PURPOSE: To efficiently remove the sodium mist by a method wherein impactors having nozzles and buffle plates are installed in a metal container and cover gas is flowed at a specified rate or higher.

CONSTITUTION: In a sodium mist remove for a sodium coolant type fast reactor, the metal container 10 is provided, in its circulation channel, with a mist trap 9 having plural steps of the impactors consisting of the buffle 11 and the nozzles 12. When the cover gas 2 is flowed into the mist trap 9, the gas flow speeds up at the part of nozzles 12 and is jetted to the buffle plates 11. This causes the mist 7 in the gas to inertially collide against the buffle plates 11 and be collected. Thus, the process prevents clogging due to sodium in the trap and ensures a stable gas flow.