Final Report - Gas Generation Testing of Uranium Metal in Simulated K Basin Sludge and in Grouted Sludge Waste Forms

Delegard, Calvin H.; Schmidt, Andrew J.; Sell, Rachel L.; Sinkov, Sergei I.; Bryan, Samuel A.; Gano, Sue; Thornton, Brenda M.

doi:10.2172/15008844

Cited by 12 publications

(16 citation statements)

References 21 publications

(29 reference statements)

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“…Methane (CH 4 ) produced by the reaction with water of uranium carbide (UC) present in the uranium metal Ferris 1962 and1964), was observed in many of the tests and C 2 H x (i.e., ethane, ethylene, acetylene), also from hydrolysis of UC, was observed in fewer tests. Methane and C 2 H x were observed in products of prior tests of K Basin sludge (Delegard et al 2000), metallic uranium fuel (Schmidt et al 2003), and uranium metal beads (from the same source as used in the present tests: Delegard et al 2004 andSinkov et al 2010). However, the absolute quantities of methane or C 2 H x were low in all cases.…”

Section: Effects Of Experimental Variables On Hydrogen Generation Ratmentioning

confidence: 71%

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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Section: Effects Of Experimental Variables On Hydrogen Generation Ratmentioning

confidence: 71%

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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“…Non-irradiated uranium metal corrosion has been studied for the K Basins Project (Delegard et al 2004b). …”

Section: Correspondence Of Non-irradiated Uranium Metal Corrosion Ratmentioning

confidence: 99%

“…Grout-type solidification matrices have been evaluated by PNNL for their potential to fix drainable liquid and to inhibit the reaction of water with uranium metal in simulated K Basin sludge (Delegard et al 2004b). The tests done by PNNL examined four grout formulations based on Portland cement and two formulations based on a magnesium phosphate cement called Tectonite™.…”

Section: Pnnl Grouting Studiesmentioning

confidence: 99%

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

Delegard

Schmidt²

2008

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This report was originally published in September 2008. In May 2009, it was discovered that, in the introductory paragraphs of Section 2.1, the units for the reaction enthalpy of uranium metal with water to form uranium dioxide and hydrogen and the reaction enthalpy of hydrogen with oxygen to form water were incorrectly given as kcal/mole rather than kJ/mole. This version of the report, Revision 1, corrects the units for both enthalpies to kJ/mole. Other small editorial changes also were made.iii SummaryThis report summarizes information and data on the reaction behavior of uranium metal in water, in water-saturated simulated and genuine K Basin sludge, and in grout matrices. This information and data are used to establish the technical basis for metallic uranium reaction behavior for the K Basin Sludge Treatment Project (STP). The specific objective of this report is to consolidate the various sources of information into a concise document to serve as a high-level reference and road map for customers, regulators, and interested parties outside the STP (e.g., external reviewers, other DOE sites) to clearly understand the current basis for the corrosion of uranium metal in water, sludge, and grout.The generation of hydrogen gas through oxidation/corrosion of uranium metal by its reaction with water can potentially create a flammable atmosphere during sludge handling, grouting, or subsequent transport and storage operations. Consequently, a thorough understanding of the uranium metal content and its reaction behavior, both in sludge and in grouted sludge matrices, is essential to the process designs and for management of sludge. Results of studies of this reaction and its characteristics have been reported in the technical literature for over 60 years. More focused studies of the reaction in simulated and genuine K Basin sludge and in grout matrices have been conducted in the past 10 years. The outcomes of these studies, provided in the present review, show that: The reaction of uranium metal with anoxic liquid water is highly exothermic and produces stoichiometric uranium dioxide (UO 2 ) and hydrogen. The reaction apparently proceeds through a uranium hydride intermediate that can sequester part of the hydrogen during the initial reaction. The corrosion reaction occurs isotropically such that the uranium particle size decreases at a constant rate at a given temperature. Based on a survey of 32 studies giving 128 data points, the corrosion rate follows an Arrhenius dependence on temperature (i.e., the logarithm of the rate is proportional to the inverse absolute temperature) from at least 24°C to 350°C. The rate law was adopted for the STP. A 95% confidence level on the predicted rate is plus/minus about a factor of three. The STP rate law is essentially the same as used in the application to license the Yucca Mountain repository. Dissolved oxygen inhibits the reaction of uranium metal with liquid water, but the more rapid anoxic reaction can follow the lower oxic rates at times that are difficult to predict...

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“…Estimates of uranium metal corrosion rate, using a published empirical equation [7] to account for the effects of pH and complexing agents, yields values ranging from 0.5 to 0.7 g cm −2 h −1 , corresponding to the increase of the electrolyte pH from 5.0 to 9.0, contradicting the estimates using the equation presented in [6]. Determination of uranium metal corrosion rates using the quantitative determination of H 2 formed during a fixed period of time [8,9] results in rates consistent with those obtained by WG or ML techniques.…”

Section: Introductionmentioning

confidence: 99%

“…The composition of corrosion products formed by 30-year storage of 115,000 Al-clad and, primarily, Zr-clad U metal fuel elements (2100 tonnes) in water-cooled K East and West fuel storage basins (US Department of Energy Hanford Site) [9,18] differed from those expected in light of fundamental corrosion studies of reactor-grade uranium metal and its binary alloys [1,2,6]. The presence of uranium hydride (UH 3 ) and U(VI) compounds, including U(VI) peroxide (UO 4 ·2H 2 O), in the product sludge was demonstrated by XRD analysis [16].…”

Section: Introductionmentioning

confidence: 99%