ORNL-5388 - the Molten Salt Energy Technologies Web Site

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Fig. A-3. Becker Separating Element With Ten Slits
The South African Helikon Process
DWG. NO. G-69643
The South Africanlo (or UCOR) process is of an aerodynamic type whose separating
element is described by the developers as a high-performance stationary-walled centri-
fuge using UF6 in hydrogen as process fluid.
All process pressures throughout the system
will be above atmospheric and, depending on the type of "centrifuge" used, the maximum
process pressure will be in a range of up to 6 bar. The UF6 partial pressure will,
however, be sufficiently low to eliminate the need for process heating during plant
operation, and the maximum temperature at the compressor delivery will not exceed 75°C.
The process is characterized by a high separation factor over the element, namely
from 1.025 to 1 .030, depending on economic considerations.
Furthermore, it has a high
degree of asymmetry with respect to the UF, flow in the enriched and depleted streams,
which emerge at different pressures. The feed-to-enriched streams pressure ratio is
typically 1.5, whereas the feed-to-depleted streams pressure ratio is typically only 1.12.
To deal with the small UF6 cut, a new cascade technique was developed--the so-called
"helikon" technique, based on the principle that an axial flow compressor can simul-
taneously transmit several streams of different isotopic composition without there being
significant mixing between them. The UCOR process must, therefore, be regarded as a
combination of the separation element and this technique, which makes it possible to
achieve the desired enrichment with a relatively small number of large separation units
by fully utilizing the high separation factor available. A further feature of the helikon