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STUDY ON A NEW METHOD FOR REDUCING RADON LEVEL IN INDOOR AIR

Takao IIDA, Takayuki KATO and Hiroki MOCHIZUKI
Department of Nuclear Engineering, Graduate School of Engineering,
Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan
Tel:+81-52-789-3781; Fax:+81-52-789-3782
e-mail:t-iida@nucl.nagoya-u.ac.jp

The aim of this study is to develop a new technique for reducing high radon level in indoor air by
method of membrane permeation using a hollow fiber module. The experiment has been carried out
for MERASILOX-S module of fine hollow fibers of silicon rubber that has high permeability constant
and MHF hollow fiber module made of thin segment polyurethane membrane. The radon permeability
constants of hollow fiber membranes have been estimated from the decrease rate of radon
concentration in a radon permeation system. The apparent permeability constant depends on the flow
rate through the outside and the inside of hollow fibers. The apparent permeability constants of
MERASILOX-S and MHF module membranes were 3.9 ×10 -9 m 2. s -1 and 1.1 ×10 -9 m 2. s -1 at the flow
rate above 5.0 L . min -1 . However, the permeation velocity of MHF module is grater than that of
MERASILOX-S module. The radon concentration in a 50 m 3 room of concrete building could be
reduced to about 1/10 by using a MHF module with membrane area of 18 m 2 . The use of pressure
different between the inside and the outside of hollow fibers might be applied to reduce the
environmental radon concentration.
Key words: radon removal, hollow fiber, silicon rubber, permeability constant, polyurethane,
permeation velocity, radon concentration