Patent Number: 058624945
Section: summary

This is a provisional application of Ser. No. 60/003,115, filed Sep. 1, 1995. BACKGROUND OF THE INVENTION The present invention relates to a method for the entrapment and minimization of hazardous moisture bearing waste material, and more specifically, to a method for entrapping the hazardous components of moisture bearing low-level radioactive and mixed waste material and substantially reducing the volume of hazardous aqueous radioactive and mixed waste material. Various types of sorbent material are used for spill control and in the packaging of liquids, sludges, and other moisture-bearing low-level radioactive and mixed waste material. Mixed waste material is defined as waste containing both radioactive and hazardous components as defined by the Atomic Energy Act (ATEA) and the Resource Conservation and Recovery Act (RCRA). Low level waste is generally defined as waste that contains radioactivity and is not classified as high-level waste, transuranic waste ("TRU"), or spent nuclear fuel. The choice of acceptable sorbent material depends upon the characteristics and the manner of disposing of the waste material. Sorbents, such as loose clay chips, mineral silica, vermiculite, and diatomaceous earth have been used in the industry for a long time. Although relatively inexpensive, some mineral type sorbents absorb only 10 to 15 percent by weight. Many mineral sorbents are very heavy and considerably increase the volume of solid waste which must be stored or buried at designated sites that are rapidly being filled by the ever increasing volume of waste material generated each year. Other sorbents, such as vermiculite, are highly absorbent but much more compressible, making it unsuitable when compression loads must be considered. Moreover, the use of mineral sorbents is labor intensive and often creates dust problems which enhance the risk associated with handling hazardous waste materials. Cellulose and wood based sorbents, such as cotton fiber, sawdust, wood pulp, corn cob centers and other biodegradable materials, are very combustible and are suitable where the primary means of disposal is incineration. However, biodegradable sorbents may be banned from hazardous based landfills because of the potential release of dangerous chemicals to the environment. One of the most promising materials available today for aqueous based moisture bearing wastes are the polymer sorbents known as polyacrylates. Polyacrylate sorbents are non-biodegradable, lightweight, low volume, and are incinerable. Polyacrylates are generally available in granulated or powder forms which are activated by the water in the waste material. The polyacrylates chemically bind the liquids to the polymer molecules to form new molecules as a matrix which can hold the liquid in a very stable gel-like matrix at significantly higher pressures. Polyacrylates have a very high liquid to sorbent ratio, often up to a 200 to 1 ratio. Some polyacrylates react with remarkable speed to encapsulate and retain the hazardous component of the waste material within the matrix. However, until now, no effective devices or systems have been developed which offer the benefits of polyacrylate sorbents for wide-spread use in hazardous waste clean-up and disposal operations, and particularly for radioactive waste entrapment and minimization. In view of the foregoing, a need exists for a device and system for delivering polyacrylate sorbent material to hazardous waste spills and leaks so that the waste is contained quickly and safely. A further need exists for a system of treating contaminated soil and other moisture bearing waste material which significantly reduces the moisture content and provides a solid waste material having no free standing liquids. A need also exists for a system which stabilizes large volumes of aqueous radioactive waste material and substantially reduces the volume of the waste material to be buried or stored at waste disposal sites. SUMMARY OF THE INVENTION These and other needs are satisfied by the present invention which provides an encapment process for rapidly stabilizing and substantially reducing the volume of moisture bearing hazardous waste materials in a variety of applications. The encapment process effectively utilizes encapsulating material in combination with equipment or systems which deliver the encapsulates to the waste material being processed. The hazardous waste may be radioactive, non-radioactive or mixed waste material. The encapsulates are preferably chosen from polyacrylic acids and all salts thereof. Polyacrylates are particularly preferred as the encapsulating material used in the encapment process of the present invention. The encapsulating material is typically in a powder or granular form. When added to a moisture bearing waste product, the encapsulates react with the moisture in the waste material to form a stable gel-like matrix. In one embodiment of the present method, pressurized vessels are filled with polyacrylate encapsulates for use in containing hazardous aqueous based spills or leaks. The vessel may be any type of container which is designed to expel its contents under pressure from a gas or other substance, and may range in size from small aerosol containers to large commercial or industrial pressurized tanks. The pressurized vessel containment system expels the encapsulates directly onto the hazardous liquid to quickly stop the flow and contain the spill. The pressurized vessels may also be used to build dikes or barriers with polyacrylates which rapidly contain spilled or leaking radioactive liquid waste material in an isolated area. The pressurized encapsulate dispensing devices of the present invention are particularly useful for relatively small emergency containment applications. However, the pressurized vessel containment system also may be configured for large storage area applications as well. In another embodiment of the present invention, a system is provided which blends the polyacrylate sorbent material with soils, sludges or other moisture bearing solid waste material. The system includes a component for adding the polyacrylate sorbent to the solid waste at a predetermined rate and a fuser for homogeneously mixing the polyacrylate sorbent with the contaminated solid waste. In yet another embodiment of the present invention, a system is provided which includes a device for delivering the polyacrylate sorbent to the liquid waste material to encapsulate and retain the hazardous components of the waste in a stable gel-like matrix. A flash evaporator, industrial microwave device, or other means is then used to rapidly reduce the moisture content of the gel. After substantially all of the moisture is removed from the gel, the waste material is in the form of a crusty ash-like material which retains the radioactive contaminants within the gel matrix. The waste minimization process of the present invention reduces the final volume of aqueous waste material by up to 99% in a safe, self-contained system. The system may be either permanently installed in a manufacturing facility or other waste generating site for ongoing treatment of hazardous liquid waste material, or the system may be provided as a mobile waste treatment system which can be moved to various locations for short term or smaller waste treatment projects. The waste minimization process is particularly useful for the safe and cost effective disposal of nuclear waste material. The encapment process of the present invention may also include the use of pads, bags or socks filled with encapsulating material. The pads may be manufactured in a variety of shapes and sizes as required by a particular application. The pads are used alone or in combination with any of the systems of the present invention. For example, the pads may be placed inside, under, or around containers of nuclear waste to absorb condensation or provide additional protection from leaks or spills.