BASIC SEPARATION THEORY
DOE-HDBK-1015/1-93
Appendix A
CH-01
Rev. 0
Page A-6
Figure A-2
Variation of Permeability with the Slope Factor and Change in Pressure
It should be noted that in practice, permeability is expressed in two different ways;
design and actual. Design permeability is expressed as a ratio as previously stated. It
is usually determined by testing the barrier with a non-toxic gas such as nitrogen. Actual
permeability is expressed as a percentage of the design permeability and is determined
from tests with the barrier in actual operation in the cascade. Its primary value is in
determining the performance of a barrier after being in use for a period of time.
Cascade Theory
In the operation of a diffusion cascade, it is often necessary to charge the plant with feed
material of different assays or concentrations of U F . This feed must be fed into the cascade
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at a point where the assay of the gas already being processed is the same as that of the feed to
be charged.
