Hanford Waste Physical and Rheological Properties: Data and Gaps

Abstract

Executive SummaryThe Hanford Site in Washington State manages 177 underground storage tanks containing approximately 250,000 m 3 of waste generated during past defense reprocessing and waste management operations. These tanks contain a mixture of sludge, saltcake and supernatant liquids. The insoluble sludge fraction of the waste consists of metal oxides and hydroxides and contains the bulk of many radionuclides such as the transuranic components and 90 Sr. The saltcake, generated by extensive evaporation of aqueous solutions, consists primarily of dried sodium salts. The supernates consist of concentrated (5-15 M) aqueous solutions of sodium and potassium salts. The 177 storage tanks include 149 single-shell tanks (SSTs) and 28 double-shell tanks (DSTs).Ultimately the wastes need to be retrieved from the tanks for treatment and disposal. The SSTs contain minimal amounts of liquid wastes, and the Tank Operations Contractor is continuing a program of moving solid wastes from SSTs to interim storage in the DSTs. The Hanford DST system provides the staging location for waste feed delivery to the Department of Energy (DOE) Office of River Protection's (ORP) Hanford Tank Waste Treatment and Immobilization Plant (WTP). The WTP is being designed and constructed to pretreat and then vitrify a large portion of the wastes in Hanford's 177 underground waste storage tanks.The retrieval, transport, treatment and disposal operations involve the handling of a wide range of slurries. Solids in the slurry have a wide range of particle size, density and chemical characteristics. Depending on the solids concentration the slurries may exhibit a Newtonian or a non-Newtonian rheology.The extent of knowledge of the physical and rheological properties is a key component to the success of the design and implementation of the waste processing facilities. These properties are used in engineering calculations in facility designs. Knowledge of the waste properties is also necessary for the development and fabrication of simulants that are used in testing at various scales. The expense and hazards associated with obtaining and using actual wastes dictates that simulants be used at many stages in the testing and scale-up of process equipment. The results presented in this report should be useful for estimating process and equipment performance and provide a technical basis for development of simulants for testing.The purpose of this document is to provide an updated summary of the Hanford waste characterization data pertinent to safe storage, retrieval, transport and processing operations for both the tank farms and the WTP and thereby identify gaps in understanding and data. Important waste parameters for these operations are identified by examining examples of relevant mathematical models of selected phenomena including: The data sets in (UDS composition and particle density, UDS primary particle size and shape, UDS particle size distributions [PSDs], and estimated particle size and density distributions [PSDDs]) and Poloski et al. (2007) ...

Small-Scale Spray Releases: Orifice Plugging Test Results

“…Simulants representing the washed and leached process stream were included because this stream is expected to present a relatively high spray release hazard. Wells et al (2011) provides composite combined PSDs for both unprocessed sludge and unprocessed saltcake waste. Given the expected dilutions required for the waste retrieval and feed operations, only sludge waste (i.e., waste in which greater than 75 vol% of the solid phase is insoluble) was considered appropriate for the waste as-received by the WTP.…”

“…Because waste feed and retrieval operations may potentially break up flocs or soft agglomerates, the set of PSDs referred to as "Sludge, Flowing Sonicated" (Wells et al 2011) were used because they best represented the size distribution expected in the shear conditions in turbulent pipe flow and spray leaks. In addition, it is known that the PSDs measured with the sample flowing and with sonication used in the instrument often give the smallest PSDs for a given sample.…”

“…Because a slurry with the smallest particle size is least likely to plug a breach, using the flowing-sonicated PSDs should provide conservative simulant for testing. Figure 3.1 shows the specific PSDs from Wells et al (2011) considered most appropriate for spray leak behavior of as-received waste as described above. As shown, significant variation exists between the PSDs of wastes from different tanks.…”

“…The sludge composite, Flowing Sonicated PSD was developed by Wells et al (2011) based on data from actual waste testing. If a tank waste is considered to be "represented" with respect to particle size regardless of the number of measurements for a given tank, then PSDs for approximately 6 percent of the Hanford waste UDS volume and 30 percent of the Hanford waste sludge UDS volume are represented by the Sludge Composite, Flowing Sonicated PSD.…”

“…The 5 th and 95 th percentile PSDs were obtained by using a volume-weighted combination of the individual PSDs in Figure 3.1 and determining the appropriate particle sizes representing the 5 th and 95 th percentiles for the full distribution. Wells et al (2011). Because the treatment of the samples removed the solids that were susceptible to leaching and washing, all samples for which there were data, including the saltcake groups, were considered.…”