Surrogate waste form

The acid-base reaction that forms the Ceramicrete waste forms also creates an oxidizing environment in which species of lower oxidation states are automatically converted to their fully oxidized states. Hence, pyrophoric components (such as PU2O3) should be converted to their most stable and fully oxidized forms (such as PUO2) that are no longer pyrophoric. Wagh et al. [10] have demonstrated such transformations in the Ceramicrete process by using surrogates of Pu (see the case study in Section 17.5.4). 

As mentioned in Section 17.3.1, retention of quadrivalent actinide oxides within the phosphate matrix is not a major issue because these oxides are insoluble in water, and all that is needed is their microencapsulation by the phosphate components of the matrix. This was demonstrated in a number of studies on UO2 and PUO2 and their surrogate Ce02. If the actinides are found in a trace amount in the waste, their chemical form is not so important because the phosphate matrix immobilizes them very efiectively. For example, the wastewater in the case study given in Section 16.3.2.2 contained 32 pCi/ml of and 0.6 pCi/ml of The ANS 16.1 tests conducted on the waste forms with 18.6pCi/g loading of combined U in the waste form showed that the leaching index was 14.52. XCLP tests also showed that levels in the leachate were below the detection limit of 0.2 pCi/ml. This implies that microencapsulation of trace-level U is very efiective in the Ceramicrete matrix. 

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. 

Formaldehyde and formic acid are the two primary intermediates formed during the conversion of EG to CO2. Phenol, hydroquinone, benzoquinone, and benzoquinone epoxide arc a few of the intermediates formed during the initial stage of BZ oxidation. EG has been used as a surrogate waste in detailed investigations of the MEO process [13] since studies of its partial oxidation by Ag(n) had been previously published [22-24], BZ has been studied [ 13] since it will be aprimary constituent of mixed waste generated by the DWPF [17]. 

Computational Results Equilibrium thermochemical calculations (using STANJAN [35] and SOLGASMIX [36] codes) of a mixture of nonplastic and plastic surrogate solids were carried out under conditions of pyrolysis and combustion see Table 15.9. A large thermodynamic data file compiled from JANAF tables is used in these codes [37]. The nonplastic material is assumed to be cellulose while the plastic material may contain any or all of the following plastics polyethylene, polyvinyl chloride, polystyrene, polypropylene, polyethylene ter-aphathalic, nylon, latex in the form of rubber, polyurethane, and acetate. Cellulose represents the organic portion of the waste such as paper and cardboard. 

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