ABSTRACT
References ................................................................................................................ 15
The idea of applying membranes in nuclear technology came from the work of Graham, who, in the middle of the nineteenth century, reported the possibility of separating gaseous mixtures by molecular diffusion. Later, the process was studied for the separation of isotopes of light elements such as neon, hydrogen, nitrogen, or carbon. During the 1940s and 1950s, the method was employed in the United States for the enrichment of 235U, the ssionable natural uranium isotope. Since the concentration of 235U in natural uranium is very low (0.711 wt%), the separation of this isotope is only possible by the application of a multistage process and a separation cascade with a large number of separating units. The crucial element of the system for isotopic enrichment is a membrane or porous barrier, the characteristics of which in›uence the stage separation factor and the size of the stage required to handle the desired stage ›ows. The preparation of such a material with ne pores of size range 6-40 nm, and a high bulk and surface porosity, presents a difcult technological problem.
