THE GREAT PROMISE OF ISOTOPES
The world is made of atoms, comprising the periodic table of elements. Many elements have
multiple isotopes, which only differ by the number of neutrons in the nucleus. These isotopes occur naturally with varying relative abundances. They can also be made artificially, leading to short-lived radioisotopes. Isotopes are a great resource for humanity. In medicine, therapy with radioactive seeds shows great promise in treating tumors. Radio-immunotherapy, where cancer cells are directly targeted and destroyed, offer a long-sought treatment for certain aggressive forms of cancer. Medical imaging with radioisotopes provides diagnosis of illness. Stable isotopes can be used as tracers for metabolism of minerals crucial for our health. It is clear that we are just on the threshold of finding many exciting new uses of isotopes that will benefit our lives.
SHORTAGE OF ISOTOPES
The starting point for isotope separation was the Calutron; it was developed in 1930 by the renowned scientist Ernest Lawrence as a machine to separate stable isotopes of the elements. The Calutron relies on ionization of neutral atoms that are then accelerated with an electric field and their trajectories bent by a large magnetic field. The Calutron is a general-purpose machine that can separate most isotopes of the elements in the periodic table, but it is very energy-intensive and thus expensive to operate. The Calutron was combined with the parallel development of the ability to transmute stable isotopes into radioisotopes with a Cyclotron, also developed by Lawrence, and used today in most major hospitals for nuclear medicine. Nuclear reactors and other accelerators are now used in addition to the Cyclotron to produce radioisotopes. They are then purified and prepared for use by advanced methods of radiochemistry.
The large-scale Calutrons in the U.S. and elsewhere were eventually shut down due to their very high operating costs, leaving only Russia as the global source. Near total dependence on Russian Calutrons created a fragile supply chain, now broken by the recent war in Ukraine. This creates an urgent need for a new domestic and efficient method for isotope production.