1. INTRODUCTION

The majority of radioactive nuclides (radionuclides) are man-made, created by transforming a stable nuclide into an unstable state by irradiation with neutrons, protons, deuterons, alphas, gammas or other nuclear particles. The source of these particles may be a radionuclide, a nuclear reactor, or a particle accelerator (Van de Graaff, cyclotron, linac, etc.). The tremendous variety of radionuclides discovered in this manner has given rise to many applications in physics, biology and, of course, medicine. The production of those medically useful radionuclides created by exposure to neutrons in a nuclear reactor is discussed in this chapter.

Soon after World War II the importance of the peaceful use of nuclear reactors for the production of radionuclides for biological research and clinical applications was foreseen. The Graphite Reactors at the Oak Ridge National Laboratory (ORNL) and Brookhaven National Laboratory (BNL) were the first full-scale operating reactor prototypes and were put to use immediately to investigate production of a variety of radionuclides. Carbon-14 was the first reactor-produced radionuclide for clinical use in nuclear medicine, and was produced at ORNL in 1946 for use at the Barnard Free Skin and Cancer Hospital in St. Louis, Missouri. In the first decade following World War II, a variety of reactor-produced radionuclides were distributed for research through the ORNL Radionuclide Development Center and BNL Hot Laboratory Division. This early work, which has been reviewed in a number of publications (see, e.g., Bizzell 1966), included production of carbon-14 and phosphorus-32 and radioisotopes of iodine ( ¹³⁰