In situ vitrification pilot-scale radioactive test

Pacific Northwest Laboratory (PNL) is developing in situ vitrification (ISV) as an in-place stabilization technique for selected liquid radioactive waste disposal sites. The process melts the wastes and surrounding soil to produce a durable glass and crystalline waste form. These ISV process development testing and evaluation studies are being conducted for the US Department of Energy. The results of an ISV pilot-scale test conducted in June of 1983 in which soils contaminated with actual radioactive transuranic and mixed fission product elements were vitrified are discussed. The primary objectives of the radioactive test were to: demonstrate containment and confinement of the radioactive material; verify equipment performance of the power and off-gas systems; identify losses to the off-gas system; and characterize the behavior of the radioactive material in the vitrified soil. The test successfully demonstrated the processing containment of radionuclides both within the vitrified mass and in the off-gas system. No environmental release of radioactive material was measured during testing operations. The vitrified soil had a greater than 99% retention of all radionuclides. Losses to the off-gas system varied from less than or equal to 0.03% for particulate materials (plutonium and strontium) to 0.8% for cesium which is a more volatile element. The off-gas system effectively contained both volatile and entrained radioactive materials. Analysis of the vitrified soil revealed that all radionuclides were distributed throughout the vitrified zone, some more uniformly than others. No migration of radionuclides outside the vitrification zone occurred, as indicated by analysis of soil samples from around the block. Previous waste form leaching studies indicate an acceptable durability of the ISV product. 8 references, 34 figures, 8 tables

Coated particle waste form development

Coated particle waste forms have been developed as part of the multibarrier concept at Pacific Northwest Laboratory under the Alternative Waste Forms Program for the Department of Energy. Primary efforts were to coat simulated nuclear waste glass marbles and ceramic pellets with low-temperature pyrolytic carbon (LT-PyC) coatings via the process of chemical vapor deposition (CVD). Fluidized bed (FB) coaters, screw agitated coaters (SAC), and rotating tube coaters were used. Coating temperatures were reduced by using catalysts and plasma activation. In general, the LT-PyC coatings did not provide the expected high leach resistance as previously measured for carbon alone. The coatings were friable and often spalled off the substrate. A totally different concept, thermal spray coating, was investigated at PNL as an alternative to CVD coating. Flame spray, wire gun, and plasma gun systems were evaluated using glass, ceramic, and metallic coating materials. Metal plasma spray coatings (Al, Sn, Zn, Pb) provided a two to three orders-of-magnitude increase in chemical durability. Because the aluminum coatings were porous, the superior leach resistance must be due to either a chemical interaction or to a pH buffer effect. Because they are complex, coated waste form processes rank low in process feasibility. Of all the possible coated particle processes, plasma sprayed marbles have the best rating. Carbon coating of pellets by CVD ranked ninth when compared with ten other processes. The plasma-spray-coated marble process ranked sixth out of eleven processes

Treatment alternatives for non-fuel-bearing hardware

This evaluation compared four alternatives for the treatment or processing of non-fuel bearing hardware (NFBH) to reduce its volume and prepare it for disposal. These treatment alternatives are: shredding; shredding and low pressure compaction; shredding and supercompaction; and melting. These alternatives are compared on the basis of system costs, waste form characteristics, and process considerations. The study recommends that melting and supercompaction alternatives be further considered and that additional testing be conducted for these two alternatives

Support for the in situ vitrification treatability study at the Idaho National Engineering Laboratory: FY 1988 summary

The objective of this project is to determine if in situ vitrification (ISV) is a viable, long-term confinement technology for previously buried solid transuranic and mixed waste at the Radioactive Waste Management Complex (RWMC). The RWMC is located at the Idaho National Engineering Laboratory (INEL). In situ vitrification is a thermal treatment process that converts contaminated soils and wastes into a durable glass and crystalline form. During processing, heavy metals or other inorganic constituents are retained and immobilized in the glass structure, and organic constituents are typically destroyed or removed for capture by an off-gas treatment system. The primary FY 1988 activities included engineering-scale feasibility tests on INEL soils containing a high metals loading. Results of engineering-scale testing indicate that wastes with a high metals content can be successfully processed by ISV. The process successfully vitrified soils containing localized metal concentrations as high as 42 wt % without requiring special methods to prevent electrical shorting within the melt zone. Vitrification of this localized concentration resulted in a 15.9 wt % metals content in the entire ISV test block. This ISV metals limit is related to the quantity of metal that accumulates at the bottom of the molten glass zone. Intermediate pilot-scale testing is recommended to determine metals content scale-up parameters in order to project metals content limits for large-scale ISV operation at INEL

Vitrification technologies for Weldon Spring raffinate sludges and contaminated soils: Phase I report: Development of alternatives

This engineering evaluation was conducted to evaluate vitrification technologies for remediation of raffinate sludges, quarry refuse, and contaminated soils at the Weldon Spring site in St. Charles County, Missouri. Two technologies were evaluated: in situ vitrification (ISV) and the joule-heated ceramic melter (JHCM). Both technologies would be effective at the Weldon Spring site. For ISV, there are two processing options for each type of waste: vitrify the waste in place, or move the waste to a staging area and then vitrify. The total time required to vitrify raffinate sludges, quarry refuse, and contaminated soil is estimated at 5 to 6 years, with operating costs of $65.7M for staged operations or$110M for in-place treatment. This estimate does not include costs for excavation and transportation of wastes to the staging location. Additional tests are recommended to provide a more in-depth evaluation of the processing options and costs. For the JHCM process, about 6.5 years would be required to vitrify the three waste types. Total operating costs are estimated to be $73M if the glass is produced in granular form, and$97M if the glass is cast into canisters. Costs for the excavation and transportation of wastes are beyond the scope of this study and are not included in the estimates. Additional tests are also recommended to better define technical issues and costs. 10 refs., 2 figs., 5 tabs

Evaluation of alternative treatments for spent fuel rod consolidation wastes and other miscellaneous commercial transuranic wastes

Eight alternative treatments (and four subalternatives) are considered for both existing commercial transuranic wastes and future wastes from spent fuel consolidation. Waste treatment is assumed to occur at a hypothetical central treatment facility (a Monitored Retrieval Storage facility was used as a reference). Disposal in a geologic repository is also assumed. The cost, process characteristics, and waste form characteristics are evaluated for each waste treatment alternative. The evaluation indicates that selection of a high-volume-reduction alternative can save almost $1 billion in life-cycle costs for the management of transuranic and high-activity wastes from 70,000 MTU of spent fuel compared to the reference MRS process. The supercompaction, arc pyrolysis and melting, and maximum volume reduction alternatives are recommended for further consideration; the latter two are recommended for further testing and demonstration

In-situ vitrification of transuranic wastes: systems evaluation and applications assessment

Major advantages of in-situ vitrification (ISV) as a means of stabilizing radioactive waste are: long term durability of the waste form; cost effectiveness; safety in terms of minimizing worker and public exposure; and applicability to different kinds of soils and buried wastes. This document describes ISV technology that is available as another viable tool for in place stabilization of waste sites. The following sections correspond to the chapters in the body of this document: description of the ISV process; analysis of the performane of the ISV tests conducted thus far; parameters of the ISV process; cost analysis for the ISV process; analysis of occupational and public exposure; and assessment of waste site applications