Development of a Demister for a Waste Evaporator Using a Hydrophobic Membrane Filter

A demister using a hydrophobic porous membrane made from polytetrafluoroethylene was developed to improve the decontamination factor (DF) of a waste evaporator. The demister removes the radioactive mist in steam generated from the evaporator. A large-scale membrane module (membrane surface area: 3 m¹) for the demister was newly designed, and its steam permeation rate and DF were experimentally examined using steam containing simulated mist (5 wt% Na₂SO₄ solution). The steam permeation rate decreases due to adhesion of removed mist on the membrane surface, but it is maintained at ∼0.35 of the initial value through falling of the mist from the membrane surface due to the mist particles’ own weight. The DF of the demister, using a membrane having less than a 0.7-μm pore diameter, is >5 × 10³. The total DF of the evaporator with the new demister is estimated to be >5 × 10⁷.