ORNL-5388 - the Molten Salt Energy Technologies Web Site

I]
1-
$i
ill
8
LI
b'
The Gas Centrifuge Process
A- 5
The countercurrent gas centrifuge separation of uranium isotopes is based on
processes developed more or less independently in the U.S. at the University of Virginia,3
in germ an^,^ and in Russia5 during World War 11. Much of this work was reported at the
1958 Geneva Conference.
In the U.S. this work was continued at the University of
Virginia and reported in 1960.6 The machine developed is shown in Fig. A-1.
The theory4s7 for operation of the gas centrifuge shows that the maximum separative
capacity of a gas centrifuge is proportional to:
a. The fourth power of the peripheral speed,
b. the length, and
c. the square of the difference in molecular weights.
Thus, it is evident that one should make the peripheral speed and the length of the
centrifuge as large as possible. The peripheral speed is limited by the bursting strength
of the material of the rotor wall. A long rotor of small diameter is comparatively
flexible and will pass through a series of resonant mechanical vibration frequencies while
being accelerated to high peripheral speed. Unless provided with special damping bearings,
a centrifuge would destroy itself while passing through one of these resonant speeds. Much
of the world's effort in advanced centrifuge development has been designed to keep below
the first resonant frequency. As a result, they are comparatively short and have relatively
low separative capacity.
Some of the differences between gas centrifuge and gaseous diffusion technologies
should perhaps be noted.
Gaseous diffusion requires fabrication of permeable barriers
with a very small pore size; the manufacture of these barriers is a difficult process
and a closely guarded secret. Gas centrifugation requires manufacture of high-speed
rotating equipment. While such manufacture is certainly not trivial, it basically
requires a well-equipped precision machine shop that may well be within the technical
capabilities of many nations. The technology of rotating machinery is widespread and
designs for gas centrifuges are in the open literature.
The power requirements for a centrifuge facility are much less than for a
diffusion facility of the same size.
separative capacity, gas centrifugation requires about 7% of the power needed for gaseous
diffusion.
For U.S. plants of economic scale and of the same
Following the early work in the U.S., further research on the centrifuge process
was undertaken for the USAEC by the University of Virginia, Union Carbide Corporation
Nuclear Division and Garrett Corporation-AiResearch Manufacturing Co., and Dr. Lars
Onsager. The current status of the U.S. program can best be indicated by a brief
description of the operating and planned faci1ities:l