Patent Number: 042697280
Section: description

DETAILED DESCRIPTION OF THE INVENTION The repositories used in accordance with the invention may be of conventional design. For example, tanks or other suitable containers to be used for the storage of nuclear waste, conventionally have diameters of from 6 to 18 feet. In most cases, containers with diameters of 15 or 16 feet are used. The spent radioactive fuel elements from nuclear reactors are introduced into the above-described repositories. Subsequently, these fuel elements are in their entirety surrounded by sulfur. Sulfur has the advantage that it is non-corrosive and is not subject to radiation damage. As a result, sulfur is an extremely stable material under radioactive conditions. Since the sulfur is non-corrosive, it does not effect dissolution of the metallic parts of the fuel elements or the repositories. Thus, the sulfur itself does not represent a radiation hazard. Moreover, of course, in the event of a leak, the sulfur is not absorbed either into the ground or the atmosphere and since it does not contain radioactive salts in any event, the danger of a radioactive contamination is minimized. In a preferred embodiment according to the present invention, the sulfur in which the fuel elements are stored is continuously kept at a temperature of more than about 112.degree. C. to maintain the sulfur in the liquid state. Accordingly, should a leak occur, the sulfur will immediately solidify at the leakage point where it is exposed to ambient temperatures below 112.degree. C. As a result, it is ensured that the liquid sulfur will not escape from the container and the radioactive fuel elements are not exposed to the atmosphere. In accordance with another feature of the present invention, the decay heat given off by the spent fuel is utilized to maintain the temperature of the sulfur at a level above the melting point of the sulfur. For this purpose, the fuel elements are spaced within the repository in which they are stored sufficiently close so that the temperature in the sulfur which surrounds the fuel elements is kept at a level of at least 112.degree. C. throughout the repository and the sulfur is constantly maintained in the molten state. The method of the present invention may be implemented in a variety of ways. Generally, the spent fuel elements can be introduced into a cylinder which is usually made of metal. The sulfur is then added to the cylinder in either the molten or solid particulate form so as to completely surround the fuel elements. If the sulfur is in the form of a solid particulate, the cylinder may be heated to make the sulfur molten. Thereafter, it may be necessary to add additional particulate sulfur in order to make certain that the elements are totally immersed. Also, it may be desirable to continue the heating of the molten sulfur for a period of time sufficient to make certain that there are no air bubbles entrapped in the molten sulfur. Thereafter, the molten sulfur can be allowed to solidify about the elements. As noted hereinabove, depending on the placement of the elements, when the individual cylinders containing the elements are placed into the final repository, they may be spaced at an appropriate distance so that any decay heat given off by the elements may be sufficient to keep the sulfur in the molten state.