Book Description

The importance of prevention of fires and explosions involving uranium, zircomum, plutonium, and thorium, which are of particular interest to the nuclear energy program, made imperative the study of their ignition behavior and oxidation kinetics. Methods of measurements of ignition characteristics of uranium and zirconium were developed and used to determine the effects of variables, such as surface preparation, metallurgical history, specific area (sample size), additives to the metal, and oxygen content and presence of moisture in the oxidizing gas. The study of ignition characteristics was supported by study of the effects of similar variables on the kinetics of oxidation of uranium and zirconium and binary alloys of each. The oxidation of uranium always proceeded in two linear stages over the temperature range of 125 to 295 deg C at pressures of 20, 50, 200, and 800 mm of oxygen. The temperature dependences of both stages indicate an activation energy dependent on pressure. The presence of ten additive elements in uranium metal caused only very small effects on the oxidation. The oxidation of zirconium was independent of pressure and proceeded according to a cubic rate law over the temperature range from 400 to 900 deg C, with an activation energy of 42.7 kcal per mole. For those additives soluble in zirconium at 700 deg C, the effects on the initial cubic rate law for oxidation are explained in terms of valency according to the Wagner- Hauffe Theory. For those additives insoluble in alpha zirconium, no single theory is felt to be adequate. The breakaway phenomena observed for many of the twenty alloys is explained in terms of a 15 per cent deviation of the additive ionic radius from the ionic radius of zirconium. Surveys of the literature on the oxidation of plutonium and thorium are presented in preparation for the study of their behavior. (auth).