Radioactive and hazardous contaminants

DOE — Organics, PCBs, petroleum/fuel hydrocarbons, solvents, TCE, unspecified VOCs, and unspecified SVOCs are among the contaminants found. Metals cited most often include lead, beryllium, mercury, arsenic, and chromium. Radioactive contaminants are present at most installations the most frequently cited are uranium, tritium, thorium, and plutonium. In addition, mixed waste containing both radioactive and hazardous contaminants is of particular concern to the DOE because of the lack of an acceptable treatment technology. 

The modification of mineral structure by substitutions is, in fact, the strength of practical CBPCs. With substitution, one can trap radioactive and hazardous contaminants in... 

The Advanced Recovery Systems, Inc. (ARS) developed the patented, ex situ DeCaF hydrometallurgical technology to decontaminate fluoride by-products and to recover recyclable metals. The technology uses a proprietary acid mixture to digest the fluoride matrix, freeing radioactive contaminants (e.g., uranium, thorium, or radium) and hazardous contaminants (e.g., lead, arsenic, or chromium). Radioactive elements are recycled or disposed. Metals are also recycled, and fluoride is recovered as a high-value salt for aluminum smelting. 

Chemical contaminants for which full-scale treatment data exist include primarily volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs). These SVOCs include polychlorinated biphenyls (PCBs), pentachlorophenol (PCP), pesticides, and herbicides. Extremely volatile metals, such as mercury and lead, can be removed by higher temperature thermal desorption systems. The technology has been applied to refinery wastes, coal tar wastes, wood-treating wastes, creosote-contaminated soils, hydrocarbon-contaminated soils, mixed (radioactive and hazardous) wastes, synthetic mbber processing wastes, and paint wastes. 

As in the case of hazardous contaminants discussed in Chapter 16, CBPC treatment converts radioactive constituents of waste streams into their nonleachable phosphate mineral forms. It follows the philosophy [7] that, if nature can store radioactive minerals as phosphates (apatite, monozites, etc.) without leaching them into the environment, researchers should be capable of doing the same by converting radioactive and hazardous... 

There are currently thousands of sites in the U.S.A. containing soil contaminated with volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), pesticides, mercury, and mixed waste (radioactive and hazardous waste). One method used frequently to remediate these sites is thermal desorption. 

The net effect on the environment is 109 discrete sources of known environmental contamination. The soil is the medium that received most of the radioactive and hazardous waste at N Reactor through direct disposal of... 

DeCaF treats soil, sludges, solids (e.g., slag), residues, and sediments contaminated with radioactive elements and other hazardous constituents. The technology has potential applications in the treatment of heavy metals. The technology can treat uranium-contaminated calcium fluoride matrices, rare-earth ore residues, and fluorspar contaminated with uranium. The technology can also extract more complex fluoride by-products. 

Ceramicrete is an ex situ stabilization technology that uses chemically bonded phosphate ceramics to stabilize low-level radioactive waste and hazardous waste containing radionuclides and heavy metals. The technology mixes phosphates with acidic solution, causing an exothermic reaction similar to that used in forming concrete. But while concrete is based on relatively weak hydrogen and van der Waals bonding, Ceramicrete uses a combination of ionic, covalenf and van der Waals bonds to stabilize contaminants. 

Following biological degradation, the extract is exposed to photochemical degradation, which removes uranium from solution as polyuranate. The metals and uranium are captured in separate treatment steps, allowing for the separation of wastes into radioactive and nonradioactive waste streams. This treatment process does not create additional hazardous wastes and allows for the reuse of the contaminated soil. The technology has been the subject of bench-scale tests and is not currently commercially available. 

CORPEX Technologies, Inc., offers CORPEX technology for the decontamination of undesirable and toxic ions or radionuclides from contaminated surfaces and coatings. The vendor states that the process can operate as either a batch or semicontinuous process. The commercially available CORPEX technology uses patented, innovative chelation chemicals to control and recover radioactive and other types of hazardous metal ions from soils, concrete, steel, and other materials. 

Polymer-based stabilization/solidification (S/S) is a technology for the ex situ treatment of radioactive, mixed, and hazardous wastes. It is a process in which polymers are created within the waste matrix to solidify and physically immobilize the hazardous constituents of contaminated materials. The goal is to prevent the migration of contaminants into the environment by forming a solid mass. 

The PO WW ER system was developed by Wheelabrator Clean Air Systems, Inc., a subsidiary of U.S. Filter Corporation, to reduce the volume of aqueous waste and catalytically oxidize volatile contaminants. PO WW ER is used to treat complex industrial and hazardous wastewaters containing mixtures of organic, inorganic, and radioactive contaminants. This proprietary, commercial technology combines evaporation with catalytic oxidation to concentrate and remove contaminants, producing a high-quality product water. 

Atoms with the same number of protons, but different numbers of neutrons in their nuclei are chemically identical atoms of the same element, but have different masses and may differ in their nuclear properties. Such atoms are isotopes of the same element. Some isotopes are radioactive isotopes, or radionuclides, which have unstable nuclei that give off charged particles and gamma rays in the form of radioactivity. Radioactivity may have detrimental, or even fatal, health effects a number of hazardous substances are radioactive, and they can cause major environmental problems. The most striking example of such contamination resulted from a massive explosion and fire at a power reactor in the Ukrainian city of Chernobyl in 1986. 

Again, as in the case of hazardous contaminants discussed in Chapter 16, the solubility of a radioactive contaminant plays a major role in its stabilization in a phosphate matrix. Therefore, one needs to understand the aqueous behavior of a radioactive contaminant prior to selecting the acid-base reaction that will form the CBPC used for fabricating the waste form matrix. In this respect, actinides, fission products, and salts have unique solubility behavior. This behavior is discussed below. 

As in all the waste forms discussed above, the TCLP results showed excellent retention of the hazardous contaminants in the matrix (Cd, Cr, Ag, Pb, and Zn) for both waste forms. The leaching levels for these contaminants were either below the detection limit or well below the UTS limits. While conducting this test for the sludge waste form, the investigators also tested leaching of Na, which is a bulk component, and Cs and Re, which are used as surrogates of radioactive Cs and Tc. 

Psychometric studies of public perception of risk have shown that dangers associated with radioactive contamination are considered the most dreaded and among the least understood hazards (Slovic, 1987). Fear of the risks associated with nuclear power and associated contamination has had important effects on pohcy and commercial decisions in the last few decades. In the US, no... 

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