Soviet Atomic Energy

During cyclic heat-treatment in the temperature range 100–550 °C with cycles of 50 second duration, recrystallization resulting in a refinement of the original microstructure occurs in uranium quenched from the γ-phase region, as well as in uranium annealed in the γ-phase and in cast uranium, not subjected to additional deformation. Recrystallization commences at places with maximum distortion of the crystal lattice.

The article describes the main methods of applying isotopic indicators in studying the problems of chemical structure and the mechanisms of chemical reactions by: 1) using isotopes as labeled atoms, 2) investigating isotope exchange, 3). using isotope dilution and 4) measuring the kinetic isotope effect. Each one of these methods is illustrated by characteristic examples from various fields of chemistry mainly concerned with fundamental problems which could not be solved without the application of isotopic indicators. A number of these examples are taken from work done in the author's laboratory.