The Separation of Hydrogen and Deuterium by the Reaction of Iron with Water

Abstract

In the decomposition of water bY reaction with iron, as in the electrolysis of water, the residual water is enriched in deuterium. Since the separation factor is an inverse function of the temperature, an attempt was made to increase the reaction rate at low temperatures. Introduction of cathodic surfaces by partial plating of cathodic impurities on steel increased the reaction rate by a factor of 2 to 4 at 98~176 Separation factors from 4.8 to 6.1 were observed for the chemical reaction of these partially plated samples with water. In electrolysis experiments vigorous agitation of the electrolyte caused an increase in the separation factor.An important part of the development of nuclear power is the procurement of heavy water which is used as a moderator in some types of nuclear reactors (1). Since the natural concentration of deuterium in water is approximately 1 part in 7000 and since separation factors are generally small for isotope separation processes, it is necessary in the initial concentration stages to process very large quantities of water (2). One of the largest separation factors is obtained in the electrolysis of water. However, the energy cost is high, and the method is practical economically only when a market exists for electrolytic hydrogen or when the method is used for the final concentration of water which has been enriched by a less expensive process (2).Separation of the isotopes is obtained in the direct chemical reaction of a variety of metals with water or steam (3-5). Smith and Posey (6) reported separation factors of 3.2 to 1.4 for the reaction between iron and steam at 118~176The reaction rate in this temperature range is low for a practical production technique. Moreover, the commercial production of hydrogen by the reaction between iron and steam requires temperatures of 800~176 (7). Since the separation factor is an inverse function of the temperature (8), temperature requirements for a useful separation factor and a useful rate in the reaction of metals with water or steam appear to be mutually exclusive. The principle of sacrificial corrosion protection suggested the possibility that the reaction rate might be increased without increasing the temperature, so that the advantage of the larger separation factor at the lower temperatures could be retained. The present paper discusses reaction rates and separation factors in the direct chemical reaction of water with iron samples some of which had plated on a portion of their surfaces a variety of cathodic materials. The effect of vigorous stirring on the concentration gradient at the cathode also is discussed.