Post Graduation Diploma in Techniques in Chemical Industry

The methods for separating, collecting, and detecting radionuclides are similar to ordinary analytical procedures and employ many of the chemical and physical principles that apply to their nonradioactive isotopes. However, some important aspects of the behavior of radionuclides are significantly different, resulting in challenges to the radiochemist to find a means for isolation of a pure sample for analysis (Friedlander et al., 1981). While separation techniques and principles may be found in standard textbooks, Chapter 14 addresses the basic chemical principles that apply to the analysis of radionuclides, with an emphasis on their unique behavior. It is not a comprehensive review of all techniques. This chapter provides: (1) a review of the important chemical principles underlying radiochemical separations, (2) a survey of the important separation methods used in radiochemistry with a discussion of their advantages and disadvantages, and (3) an examination of the particular features of radioanalytical chemistry that distinguish it from ordinary analytical chemistry. Extensive examples have been provided throughout the chapter to illustrate various principles, practices, and procedures in radiochemistry. Many were selected purposely as familiar illustrations from agency procedural manuals. Others were taken from the classical and recent radiochemical literature to provide a broad, general overview of the subject. This chapter integrates the concepts of classical chemistry with those topics unique to radionuclide analysis. The first eight sections of the chapter describe the bases for chemical separations involving oxidation-reduction, complex-ion formation, distillation/volatilization, solvent extraction, precipitation and coprecipitation, electrochemistry, and chromatography. Carriers and tracers, which are unique to radiochemistry, are described in Section 14.9 together with specific separation examples for each of the elements covered in this manual. Section 14.10 also provides an overview of the solution chemistry and appropriate separation techniques for 17 elements. An attachment at the end of the chapter describes the phenomenon of radioactive equilibrium, also unique to radioactive materials. Because the radiochemist detects atoms by their radiation, the success or failure of a radiochemical procedure often depends on the ability to separate extremely small quantities of radionuclides (e.g., 10!6 to 10!12 g) that might interfere with detection of the analyte. For example, isolation of trace quantities of a radionuclide that will not precipitate on its own with a counter-ion requires judicious