Page 47 - Radiochemistry and nuclear chemistry

36 Radiochemistry and Nuclear Chemistry

the former Soviet Union and a few other countries. Gram amounts of electromagnetically
separated stable isotopes of most dements are commercially available on the world market
in high isotopic purity. Electromagnetic separators are also used for on-line separation of
nuclear reaction products (Ch. 15).

2.8.6. Gas centrifugation

Though gas diffusion is the dominating process for 235U enrichment, its small separation
factor, large energy consumption, and secrecy about the technique have encouraged interest
in finding other and more advantageous processes. Most effort has been put into developing
centrifugal processes because of the large separation factors achievable.
In a gas centrifuge, light molecules are enriched at the center and heavy molecules at the
periphery (Fig. 2.10). It can be shown that the ratio of radial concentration to the axial
concentration for isotopic molecules under equilibrium conditions and at low pressure
(avoiding remixing due to the Brownian movement) is given approximately by

xplx F -~ e 6n (2.58)

for n centrifuges (stages) connected in series. Here

= (MH-ML)10 -3 Vr 2 r 2/2RT (2.59)

FIG. 2.10. Gas centrifuge for 235UF6 enrichment. Right shows centrifuge cascade in
operation at Almelo.