Patent Number: 054024552
Section: summary

FIELD OF THE INVENTION The present invention relates to a composite material having use in containment systems and container vessels for storage of waste materials. More specifically, the invention relates to containment systems and container vessels for storage of hazardous, radioactive, or mixed wastes wherein the system or vessel is fabricated with a multilayered structure including a fibrous mat layer. BACKGROUND OF THE INVENTION Containment systems employing various composite structures have been developed to handle waste materials. The waste materials to which this invention is concerned are primarily hazardous, radioactive, and mixed, that is both hazardous and radioactive, wastes. These containment systems must meet rigid governmental safety standards set for structural stability and strength, along with those for its shielding characteristics. Conventionally, these containment systems have been made with composite materials having concrete layers, optionally reinforced with metal bars such as a rebar construction to improve the strength of the container. Examples of such systems are generally shown in U.S. Pat. Nos. 4,950,246 and 4,845,372. These systems have been widely used and accepted by the industry, however improvements upon these designs can be made to improve their strength and shielding capacity. SUMMARY OF THE INVENTION The present invention provides an improved shielding composite material having a multiple layered construction. The composite contains a fibrous mat layer that has a first and a second face. The mat layer contains a mat that is made from interwoven fibers, preferably metallic fibers, and these fibers are encased within a concrete-based material. A first concrete-based layer is located proximate to at least one face, and optionally both faces, of the mat layer. The concrete-based layer preferably contains at least one shielding additive such as barite, magnetite, taconite, depleted uranium, vitrified glass-like materials manufactured from thermal treatment of wastes, and mixtures thereof. An impermeable coating layer is optionally placed on the exposed face of either concrete-based layer to prevent liquids and other fluids from contacting the concrete-based layers. The mat layer, composed of the fibrous mat and solidified in the concrete-based material, improves both the strength of the layered storage composite, but also improves its shielding capacity in comparison to a similar composite made with concrete, or concrete with a rebar construction. The present invention also provides methods for constructing the multi-layered storage structure composite. The fibrous mat containing the interwoven fibers is provided such that a first and second face are exposed. A concrete-based mixture is then poured into and adjacent to the mat to encase the fibers of the mat in the concrete-based mixture and to provide a first concrete-based layer proximate to the first face of the mat. The concrete-based mixture preferably contains at least one shielding additive.