Patent Number: 043371671
Section: description

DETAILED DESCRIPTION During the metamorphic alteration of ultramafic rocks to form serpentine, native nickel-iron alloys are often produced under thermodyanmically stable conditions. These alloys constitute the mineral awaruite and are composed mainly of nickel (60 to 90 percent) and iron (10 to 40 percent), together with small amounts of cobalt and copper (less than 5 percent each). The most common composition corresponds to the formula Ni.sub.3 Fe, which is that of an ordered stoichiometric phase. Awaruite has been produced at elevated temperatures, probably exceeding 300.degree. C., during serpentinization of periodotite. In some examples, serpentinization has been caused by circulating sea water. In both cases, it can be demonstrated that occurrences of awaruite have survived for periods exceeding tens of millions of years. Another natural alloy which is found in serpentinized periodotite in large lumps is josephinite, which has a chemical composition similar to awaruite. The origin of josephinite is unclear, but it can be demonstrated that this alloy has also survived in association with serpentine and periodotite for periods exceeding tens of millions of years. Both awaruite and josephinite are thermodynamically stable over wide ranges of Eh, pH, temperature, pressure, and in the presence of ground waters containing substantial amounts of chloride ions and other solutes in the natural geochemical environment. Moreover, these alloys have a high melting point, high mechanical strength, and can be cast, fabricated, and machined. Because of these properties, it has become apparent to us that these alloys make ideal containers for solid nuclear waste materials which are to be buried underground in the natural geochemical environment. This is the essence of our invention. Both minerals are known per se, and we of course do not claim to have discovered or invented the minerals as such. Similarly, our invention is not a new structural design for nuclear waste containers, nor is it limited to any particular waste container structure.