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A simulation model has been developed for transient response of a gas separation module using a hollow fiber membrane for the removal of tritium from the atmosphere of the confinement space. The mass transfer process such as sorption and desorption of gases at the surface of the dense layer and the porous support layer, diffusive transfer in the both layers are treated in the model. Sorption isotherm, mass transfer rate and permeance are estimated through step-wise transient response experiments. The present model represents well not only separation factors and recovery ratio at the steady state but also responses to the multi-step wise change in the sweep gas rate.

For future fusion reactors, where a huge amount of tritium will be handled, it is necessary to establish the technology for the removal of tritium from the atmosphere of the confinement space. A conventional method is to oxidize tritium by a catalytic reactor and to remove tritium by a molecular sieve bed [1]. Some dozens of molecular sieve beds and a complex switching control are required for continuous processing with a large throughput because molecular sieve beds need desorption treatment before the breakthrough time. In addition, desorption process consumes enormous energy. These problems will be fatal defects for a future fusion reactor which needs a quite large confinement space. One of the alternatives is a gas separation system using a hollow fiber membrane. The advantages of the membrane system are compact scale, low energy consumption, and high reliability for operation without a complex switching control. A number of studies have been presented in order to apply gas separation membranes to tritium removal and confinement systems of fusion reactors [2], [3], [4] and [5]. Separation factor and recovery ratio of water vapor from the air at steady state were mainly reported. Although it is very important to investigate transient responses of such membrane systems in practical use, the simulation method has not been established yet. The concentration of water vapor at the outlet and the permeated flow rate of the membrane module are very slow to respond against the change in humidity at the inlet or any other operational conditions of the module. These slow responses cannot be simulated by the conventional model which does not take into account transient phenomena such as the change of liquid-holdup in the membrane material.

A simulation model was developed to simulate transient responses of the water vapor permselective membrane module for the removal of tritium from the atmosphere of the confinement space. The mass transfer processes such as sorption and desorption of gases, diffusive transfer, competitive sorption and change of liquid-holdup in the membrane are incorporated in the model. Sorption isotherm, mass transfer rate and permeability were estimated through step-wise transient response experiments. The present model represented well not only separation factors and recovery ratio of water vapor at the steady state but also multi-step wise responses of the module.