Mitigation of Hydrogen Gas Generation from the Reaction of Water with Uranium Metal in K Basins Sludge

Sinkov, Sergey I.; Delegard, Calvin H.; Schmidt, Andrew J.

doi:10.2172/973413

Cited by 3 publications

(4 citation statements)

References 52 publications

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“…In Tests S-5 and S-6, an opaque rustbrown and non-settling suspension formed in the supernatant. The color and the non-settling, very finely particulate character of the suspension is consistent with the hematite, Fe 2 O 3 , and goethite, FeOOH, present from the aging of the ferrihydrite component used to prepare the simulant sludge (see Appendix A of Sinkov et al 2010 for XRD analysis of the ferrihydrite starting material). (a) ~24 hr 96…”

Section: 25supporting

confidence: 62%

“…The ferrihydrite, identified as ferric oxide hydroxide (Shepherd Chemical Company), was analyzed by the vendor to be poorly crystalline 6-line ferrihydrite by X-ray diffractometry (XRD). Subsequent XRD analysis by PNNL showed that no observable 6-line ferrihydrite was present and that the solids had transformed to goethite and hematite (Sinkov et al 2010). Tests of the pH of slurries of this material have shown it to be alkaline (i.e., pH ~12).…”

Section: Ferrihydritementioning

confidence: 94%

“…The finely granular to powdery Hanford blow sand used in the testing was collected from the Fitzner-Eberhardt Arid Lands Ecology (ALE) Reserve in July 2007 between mileposts 9 and 10 on the south side of State Highway 240, about 12 miles south of the KW Basin. According to XRD analysis (Sinkov et al 2010), the sand contained quartz (SiO2), anorthite (CaAl 2 Si 2 O 8 ), microcline (KAlSi 3 O 8 ), mica [KFe 3 (Al 0.24 Fe 0.76 Si 3 )O 10 (OH) 2 ], and aegerine (Fe 0.5185 Al 0.4185 Ca 0.466 Na 0.534 Si 2 O 6 ). Non-crystalline or glassy phases found in basalt are ubiquitous in the Hanford soils but are not seen by XRD.…”

Section: Hanford (Ale) Sandmentioning

confidence: 99%

“…The sludge component quantities required to prepare the 2.277-g (dry basis) portions used in each KW containerized sludge test are shown in the right-most column. Note that the amounts of ion exchange media used in previous formulations of this simulated sludge (e.g., as used in Sinkov et al 2010) were lower. The OIER content increased to 7.5 wt% from the 2.0 wt% used in previous testing, the mordenite increased to 7.7 wt% from 2.0%, and ALE sand correspondingly decreased to 16.4 wt% from the 27.6 wt% used previously.…”

Section: Kw Containerized Simulant Sludge Preparationmentioning

confidence: 99%

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Effects of Time, Heat, and Oxygen on K Basin Sludge Agglomeration, Strength, and Solids Volume

Delegard¹,

Sinkov²,

Schmidt³

et al. 2011

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ph: (865) 576-8401 fax: (865) 576 5728 email: reports@adonis.osti.gov Available to the public from the National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Rd., Springfield, VA 22161 ph: (800) 553-6847 fax: (703) 605-6900 email: orders@nits.fedworld.gov online ordering: http://www.ntis.gov/ordering.htm Abstract viiThese findings indicate that for solids very rich in uranium (≳70 to 80 wt%, dry basis), long-term storage under aerated non-agitated conditions will form a thin metaschoepite crust that is readily broken. The underlying material may compact somewhat with time, but, because little appreciable change in settled solids strength was seen after nearly a year of settling at 51°C in laboratory tests, little increase in strength, beyond that associated with any compaction, is anticipated during lower temperature but longer term storage.The observations from the 28-month settling test with uranium-rich genuine sludge and the studies with the uraninite oxidation suggest that metaschoepite crystal ripening and intergrowth may have been responsible for the uncommon strength found in the genuine sludge. In this case, the presence of relatively high amounts of metaschoepite within the settled solids layer likely was necessary to produce the strong product material. Based on these findings, K Basin sludges rich in metaschoepite [≳70 to 80 wt% U as U(VI), dry basis] may self-cement by Ostwald ripening to produce strong agglomerates similar to the behavior shown by the 96-13 sludge in the 28-month settling tests. Because of the low solubility of UO 2 , similar gains in strength by Ostwald ripening for UO 2 -rich sludge cannot occur.  Under 51°C oxygenated conditions, a full KW containerized sludge simulant containing gibbsite, ferrihydrite, mordenite, organic ion exchange resin, Hanford sand, and ~50%/50% UO 2 /UO 3 ·2H 2 O decreased in settled solids volume by about 25% over 106 days while a parallel control test run in the absence of oxygen decreased only about 3%. The volume decrease coincided with the oxidation of UO 2 to UO 3 ·2H 2 O and may have been due to better solids packing or coagulation of non-uranium solids with the crystallizing UO 3 ·2H 2 O. However, even though the KW containerized sludge simulant compacted with time, the strength remained low. Under warm (30±5ºC) semi-oxic conditions, the uraninite in uranium-rich K Basin sludge samples oxidized to metaschoepite and other U(VI) phases after 9 years of hot cell storage (Delegard et al. 2007a).These findings mean that, unlike uraninite-rich sludges that form continuous layers or networks of product metaschoepite upon reaction with oxygen or which already have high metaschoepite concentrations, sludges more dilute in uraninite or metaschoepite likely will be unable to produce continuous metaschoepite layers that inhibit further oxidation or which self-cement to form highstrength agglomerates. Instead, the metaschoepite may act to coagulate non-uranium sludge solids and produce settled solids that are more tightly packed ...

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Section: 25supporting

confidence: 62%

Section: Ferrihydritementioning

confidence: 94%

Section: Hanford (Ale) Sandmentioning

confidence: 99%

Section: Kw Containerized Simulant Sludge Preparationmentioning

confidence: 99%

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Effects of Time, Heat, and Oxygen on K Basin Sludge Agglomeration, Strength, and Solids Volume

Delegard¹,

Sinkov²,

Schmidt³

et al. 2011

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Uranium Metal Oxidation, Grinding, and Encapsulation in BoroBond®: TRU Waste Management

Cook¹,

Addington²,

Utley³

2011

ASME 2011 14th International Conference on Environmental Remediation and Radioactive Waste Management, Parts a and B

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Hydrogen generation mitigation for K Basin sludge was examined by encapsulation of uranium metal in BoroBond®, pre-oxidation of uranium metal with Fenton’s reagent and grinding of Densalloy SD170, an irradiated uranium metal surrogate. Encapsulation in BoroBond® resulted in pressure increase rates at 60 °C ranging from 0.116 torr/h to 0.186 torr/h compared to 0.240 torr/h for a uranium metal in water standard. Samples cast with higher water content led to increased rates. A Fenton’s reagent system consisting of a simple reagent mix of FeSO4·7H2O, H2O2 and HCl effectively oxidized 1/4″ cubes of uranium metal in under four days at room temperature. Increased peroxide addition rate, increased FeSO4·7H2O concentration and low pH all increase the corrosion rate. Densalloy SD170 with an average particle size of 581 μm with 7.63% of particles less than 90 μm was milled so that over 90% of the Densalloy mass measured less than 90 μm in 6 hours of milling. Acceptable wear rates were seen on wear components that were from standard materials (Nitronic SS and 440SS).

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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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Mitigation of Hydrogen Gas Generation from the Reaction of Water with Uranium Metal in K Basins Sludge

Cited by 3 publications

References 52 publications

Effects of Time, Heat, and Oxygen on K Basin Sludge Agglomeration, Strength, and Solids Volume

Effects of Time, Heat, and Oxygen on K Basin Sludge Agglomeration, Strength, and Solids Volume

Uranium Metal Oxidation, Grinding, and Encapsulation in BoroBond®: TRU Waste Management

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

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