5. CHEMICAL PROCESSING

In order to achieve high specific activity, radionuclides require chemical separation from the target material and induced radioactive byproducts. This is not feasible for (n, ?) reactions when isotope separation techniques are called for (see Chapter 5 in Volume 5) that are based on subtle differences between the properties of different isotopes (see Chapter 4 in Volume 2). Standard techniques of analytic separation chemistry are used, such as chromatography, solvent extraction, distillation and precipitation. Other techniques include electrolysis and electro-deposition, and separations based on sublimation. These processing techniques must then be adapted to the unique requirements of radiochemistry the hazards of radiation exposure and contamination, rapid separation times in order to minimize decay losses, and the separation of essentially massless (carrier-free) amounts of product from bulk target. A great deal of effort has gone into developing processes suitable for each application. For example, solvent extraction is commonly used for purification of reactor- produced ¹⁹¹Os in the form of OsO ₄ which is trapped as perosmate in a NaOH solution (Brihaye et al. 1989). With the proper choice of conditions, ion exchange is very useful for separating carrier-free radionuclides from bulk target (mass ratio>10 ⁸) having significantly lower affinity toward the resin. This method has been particularly successful in separating transition metals from each other and from the rare earth elements. A relevant example is the separation of ⁵⁵Co from an Fe target (Lagunas-Solar and Jungerman 1979). It can be combined with...