Uranium Metal Reaction Behavior in Water, Sludge, and Grout Matrices

Delegard, Calvin H.; Schmidt, Andrew J.

doi:10.2172/957367

Cited by 4 publications

(5 citation statements)

References 22 publications

(40 reference statements)

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“…This initial delay is possibly due to a surface corrosion layer on the iron particles. Similar delays in gas generation have been observed during the corrosion of uranium metal (Delegard and Schmidt 2009). Once gas generation began, the volume of generated gas was larger with progressively higher concentrations of iron.…”

Section: Role Of Gas Generation Rate and Methods On Gas Retentionsupporting

confidence: 68%

“…It is suspected that the older material that had been in the laboratory probably had a surface layer of corrosion that delayed the onset of additional corrosion and hydrogen generation. Studies of hydrogen generation from corroding uranium metal show similar delays in onset of gas generation (Delegard and Schmidt 2009). During the initial studies with the iron particles, it appeared that there was some biological activity in the clay and a small amount of biocide (100 ppm of Mt.…”

Section: 5mentioning

confidence: 90%

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Strong-Sludge Gas Retention and Release Mechanisms in Clay Simulants

Gauglitz¹,

Buchmiller²,

Probert³

et al. 2012

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Executive SummaryThe Hanford Site has 28 double-shell tanks (DSTs) and 149 single-shell tanks (SSTs) containing radioactive wastes that are complex mixes of radioactive and chemical products. The mission of the Department of Energy's River Protection Project is to retrieve and treat the Hanford tank waste for disposal and close the tank farms. A key aspect of the mission is to retrieve and transfer waste from the SSTs, which are at greater risk for leaking, into DSTs for interim storage until the waste is transferred to and treated in the Hanford Waste Treatment and Immobilization Plant. There is, however, limited space in the existing DSTs to accept waste transfers from the SSTs, and approaches to overcoming the limited DST space will benefit the overall mission.The current safety basis for managing the waste in the tank farms provides controls to prevent spontaneous buoyant-displacement gas release events (BDGREs) and provide for ongoing safe storage of the waste. The current mission plan for future waste transfers assumes a relaxed set of BDGRE controls for selected wastes and DSTs based on a new experimental finding that shows relatively low gas retention for sediment materials that are sufficiently strong (shear strengths greater than about 1000 Pa). Based on these relaxed controls, waste from additional SSTs could be retrieved and transferred to DSTs while still avoiding the potential for BDGREs.The purpose of this study is to summarize and analyze the key previous experiment that forms the basis for the relaxed controls and to summarize progress and results on new experiments focused on understanding the conditions that result in low gas retention. The previous large-scale test used about 50 m 3 of sediment, which would be unwieldy for doing multiple parametric experiments. Accordingly, experiments began with smaller-scale tests to determine whether the desired mechanisms can be studied without the difficulty of conducting very large experiments.The previous large-scale gas retention test was conducted in a 3.5 m diameter test vessel with a sediment layer about 5 m deep. The average retained-gas volume fraction grew over a 25 day period to a peak value of about 7% and then decreased to about 5%. This is much lower than in previous small-scale tests.A key objective for the current gas-retention tests is to conduct tests that have slower gas generation rates and are larger than the previous small-scale tests. In the current study, small-scale tests were conducted with various mixtures of kaolin clay and Min-U-Sil 30 ®1 , which is finely ground silica with a median diameter of about 8 microns, in primarily 12.7 cm diameter test vessels with gas generation provided either by the decomposition of hydrogen peroxide to form oxygen bubbles or by the corrosion of iron to form hydrogen bubbles. The gas generation rates varied and resulted in gas retention that peaked after about 1 to 10 days. The volumes of retained gas and total generated gas were measured over time to determine the retained-gas fraction. Tests we...

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Section: Role Of Gas Generation Rate and Methods On Gas Retentionsupporting

confidence: 68%

Section: 5mentioning

confidence: 90%

Strong-Sludge Gas Retention and Release Mechanisms in Clay Simulants

Gauglitz¹,

Buchmiller²,

Probert³

et al. 2012

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“…All but two experiments contained 30 uranium metal beads of roughly 700-μm diameter weighing ~0.1 g in total. These beads are near in size to the ~560-μm uranium metal particle size observed in earlier analyses of K Basin sludge (Delegard and Schmidt 2009). The testing was performed in closed vessels designed to collect and contain the starting air and product gases with the test materials held at thermostatically controlled temperatures.…”

Section: Experimental Materials and Methodssupporting

confidence: 53%

“…The effect of decreased temperature could be inferred based on the known published rates of uranium metal reaction with water (Delegard and Schmidt 2009). Of the remaining three approaches, hydrogen scavenging appeared to be the most promising for laboratory testing, but experimental effort into reactant isolation and corrosion inhibition was also conducted and reported.…”

Section: Discussionmentioning

confidence: 99%

“…Four means to decrease the H 2 evolution rate were identified for further experimental consideration: 1) decreased temperature; 2) reactant isolation (separation of the uranium metal from the water); 3) corrosion inhibition; and 4) hydrogen scavenging. The effect of decreased temperature could be inferred based on the known published rates of uranium metal reaction with water (Delegard and Schmidt 2009). Of the remaining three approaches, hydrogen scavenging appeared to be the most promising and testing of this alternative was performed (Sinkov et al 2010).…”

Section: Introductionmentioning

confidence: 99%

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Mitigation of Hydrogen Gas Generation from the Reaction of Uranium Metal with Water in K Basin Sludge and Sludge Waste Forms

Sinkov¹,

Delegard²,

Schmidt³

2011

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Sludge formed and reposing in the K East (KE) and K West (KW) fuel storage basins on the Hanford Site has been a subject of concern since extended storage of metallic fuel from the N Reactor began in the 1980s. Although the last of the fuel was removed from the basins in 2004 and transport of sludge from the KE Basin to the KW Basin was completed in 2007, sludge still remains in the KW Basin stored in engineered containers. Sludge will be recovered from the engineered containers into Sludge Transport and Storage Containers and stored at an interim storage location on the Central Plateau. The stored sludge ultimately will be processed for disposal to the Waste Isolation Pilot Plant (WIPP) as remote-handled transuranic waste. However, before the sludge can go to WIPP, it must be processed and packaged into WIPP-acceptable forms. The presence of uranium metal fuel particles in the sludge poses problems to these operations because uranium metal reacts with water to form flammable hydrogen gas.Activities surrounding the storage, transport, treatment, and disposition of the K Basin sludge are currently administered under the Sludge Treatment Project (STP) managed by CH2M Hill Plateau Remediation Company (CHPRC) operating under contract to the U.S. Department of Energy. Investigative studies in this report were conducted by Pacific Northwest National Laboratory (PNNL) under contract to CHPRC for the STP.The reaction of uranium metal with water to form diatomic hydrogen gas (H 2 ) and uranium dioxide or uraninite (UO 2 ) proceeds by way of uranium hydride (UH 3 ). Mechanistic studies show that hydrogen radicals (H) and UH 3 serve as intermediates in the reaction of uranium metal with water to produce H 2 and UO 2 . Because H 2 is flammable, its release into the gas phase above K Basin sludge during sludge storage, processing, immobilization, shipment, and disposal is a concern to operational safety. PNNL conducted literature reviews and laboratory studies to identify methods that could be used to decrease the rate of H 2 gas generation from uranium metal corrosion in water present in sludge (Sinkov et al. 2010). Four means to decrease the H 2 evolution rate were identified for further experimental consideration:1. decreased temperature 2. reactant isolation (separation of the uranium metal from the water) 3. corrosion inhibition 4. hydrogen scavenging.The effect of decreased temperature could be inferred based on the known published rates of uranium metal reaction with water (Delegard and Schmidt 2009). Of the remaining three approaches, hydrogen scavenging appeared to be the most promising for laboratory testing, but experimental effort into reactant isolation and corrosion inhibition was also conducted and reported.Laboratory testing identified nitrate, NO 3 -, and nitrite, NO 2 -(added as their sodium salts) to be the most promising agents to minimize H 2 generation in prospective K Basin sludge operations because of their demonstrated high-attenuation factors, decreasing hydrogen generation rates hundreds-to thousan...

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