SUMMARY

Methods of isotope enrichment and isotope separation are reviewed. Several examples of commercially important or historically important separative processes are discussed.

1. INTRODUCTION

The small differences in chemical and physical properties of the isotopes of all but the lightest elements make their separation from each other unusually difficult. That difficulty is often compounded by the fact that the desired isotopic molecules (isotopologues) ^[1] is often present at low or very low concentration in the starting material. These factors, taken together, imply the processing of very large amounts of feedstock, at high reflux, through many, many separative stages. This, in barest outline, accounts for the high cost of samples of most separated isotopes.

Over the past fifty or more years the nuclides of greatest industrial and/or military importance have been ²³⁵U, the heavy isotopes of hydrogen, ²H(D) and ³H(T), and in greatly reduced amount, ⁶Li and ⁷Li, ¹⁰B, ¹³C, ¹⁵N, and ¹⁸O. Samples of many other enriched isotopes, chiefly for medical or research use, have been or are available. Very often these have been obtained by electromagnetic separation, a process which is too expensive for large scale separations.

During peak production, on the order of 1 billion dollars of ²³⁵U was enriched per year from the natural abundance level (0.7%) to 1.5 to 4% for use in graphite or water moderated power reactors, or at higher enrichment...