Cascade of a Gas Centrifuge Plant1
After chemical conversion of natural uranium ore concentrate
into uranium hexafluoride (UF6), the UF6 is put into standard containers and sent to
an enrichment plant. At the enrichment plant, the transport container
and its UF6 contents are put into a heating
chamber, or "autoclave," to vaporise the UF6.
After pressure reduction by control valves, the UF6
is fed into the cascades. A cascade is composed of centrifuges
connected by pipes both in series and in parallel. Inside the
cascade, the gas stream is divided into two output streams by
the centrifuges. One stream is enriched in uranium 235 (U-235)
and the other depleted in U-235.
The UF6 gas, which is at very low pressure,
is withdrawn from the cascade by compressors that raise the pressure
of the gas. It is piped to transportation containers in cooling
boxes, where the UF6 solidifies.
The separation effect of a cascade is expressed in separative
work units calculated by a standard formula. Seperative work is
defined as a measure of the effort required in an enrichment facility
to separate uranium of a given U-235 content into two fractions,
one with a higher percentage and one with a lower percentage of
U-235. The unit of separative work is the kilogram separative
work unit (kg SWU), or separative work unit (SWU) for short. The
initial material is called the "feed." The fraction
with a higher proportion of U-235 is called the "product,"
the other is called the "tails." The higher the U-235
content of the enriched uranium and the lower the U-235 content
of the depleted uranium, the more SWUs are required.
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