Laboratory Testing of Bulk Vitrified and Steam Reformed Low-Activity Waste Forms to Support A Preliminary Risk Assessment for an Integrated Disposal Facility

Abstract

Low-activity tank wastes will be generated during cleanup of high-level radioactive tank wastes on the Hanford site. The low-activity tank waste will be among the largest volumes of radioactive waste within the U.S. Department of Energy (DOE) complex and is one of the largest inventories of long-lived radionuclides planned for disposal in a low-level waste facility. The Department of Energy's Office of River Protection is evaluating several options for immobilization of low-activity tank wastes for eventual disposal in a shallow subsurface facility at the Hanford Site. A significant portion of the waste will be converted into low-activity waste (LAW) glass with a conventional Joule-heated ceramic melter. In addition, three supplemental treatment processes are presently under consideration by the DOE to treat wastes in selected tanks with the goal of accelerating the overall cleanup mission at the Hanford site. These are: 1) bulk vitrification (BV), 2) cementation or the cast stone (CS) process, and 3) steam reformation (SR). The DOE is expected to select by October 2003 one or more of these supplemental treatment technologies for more detailed evaluation. As part of the selection process, a preliminary risk assessment is being performed to evaluate the impacts of the disposal facility on public health and environmental resources. The purpose of this report is to document the laboratory testing that was conducted on BV and SR waste forms to supply the input parameters needed for reactive chemical transport calculations with the Subsurface Transport Over Reactive Multiphases (STORM) code. This same code was used to conduct the 2001 ILAW performance assessment. The required input parameters for BV and SR waste forms are derived from a mechanistic model that describes the effect of solution chemistry on contaminant release rates. The single-pass flow-through test is the principal method used to obtain these input parameters, supplemented by product consistency test measurements and physical property measurements. v 2.1.1.1 X-ray Microtomagraphy (XMT) X-ray microtomography provided a novel way to characterize the froth layer glass properties. Characterization was principally done on a piece of froth-layer glass broken off the sample shown in Figure 2. This sampled was labeled BKV5. The XMT system at PNNL, shown in Figure 5, is an ACTIS 200/160 KXR unit manufactured by Bio-Imaging Research, Inc. The x-ray generator is a Kevex KM16010E-A X-ray tube with spot sizes of 10, 20, 65, 250 µm at power levels 5, 10, 50, and 160 watts. The microfocus X-ray source allows variable slice widths over a nominal range of 10 to 150 µm and can achieve resolution in the focal plane of one one-thousandth of the object diameter. A computer-controlled sample manipulator with a 75-mm diameter turntable allows 365° of continuous rotation and a maximum vertical travel of 150 mm The detection system is a BIR RLS 2048-100 discrete element solid-state detector system consisting of gadolinium oxysulfide scintillator and EG & G Reticon photodiodide...

Strong-Sludge Gas Retention and Release Mechanisms in Clay Simulants

“…In recent years, scientists have used these systems to investigate geologic materials, with the technology rapidly becoming a part of routine sample characterization (Ketcham and Carlson 2001). For example, imaging with x-rays was used to support studies in site remediation for heavy-metal contaminants and in the evaluation of bulk vitrification processing of low-level tank waste (Wellman et al 2005;McGrail et al 2003).…”

Radioactive Demonstration Of Mineralized Waste Forms Made From Hanford Low Activity Waste (Tank SX-105, Tank AN-103, And AZ-101/102) By Fluidized Bed Steam Reformation (FBSR)

“…The release of radionuclides Tc-99 and I-129 from granular NAS waste forms was hypothesized during the preliminary RA to be limited by nosean solubility as the rhenium releases during durability testing tracked the sulfate releases. [36,37,39] The predicted performance of the granular NAS waste form was found to be comparable to the glass waste form in the initial supplemental LAW treatment technology risk assessment (Figure 1-2) [39].…”

Radionuclide and Contaminant Immobilization in the Fluidized Bed Steam Reforming Waste Product

“…Large uncertainties associated with the porosity of the FBSR granular product gives a large discrepancy between a calculated geometric surface area and the measured surface area of the material using Brunauer, Emmett, and Teller (BET) (Brunauer et al, 1938) surface area measurements. Using the smaller surface area from the geometrical value would lead to an underestimation in dissolution rates used for product durability studies therefore it has been recommended to use the surface area obtained from BET measurements (McGrail et al, 2003a).…”

“…Table 6 gives data on the density, particle size, and surface area of the FBSR granular product from the early FBSR campaigns with INEEL SBW and the Hanford LAW campaign . The measured BET surface areas were measured in this study on a carbon-free basis (coal removed by roasting), and the value measured by McGrail et al (2003a) (coal removed manually) was obtained for comparison. The geometric surface area is from Lorier et al (2005).…”