TWRS privatization process technical baseline

Orme, Richard

doi:10.2172/658905

Cited by 25 publications

(36 citation statements)

References 3 publications

(5 reference statements)

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“…Caustic leaching is the baseline method for pretreating Hanford tank sludges (Orme et al 1996). Caustic leaching is expected to remove a large fraction of the Al, which is present in large quantities in Hanford tank sludges, by converting poorly soluble Al oxides/hydroxides to the more soluble sodium aluminate, NaAl(OH) 4 .…”

Section: Selective Chromium Removal Under Alkaline Conditionsmentioning

confidence: 99%

Selective Leaching of Chromium from Hanford Tank Sludge 241-U-108

Rapko

Vienna²

2002

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SummaryPretreatment approaches are planned to improve the effectiveness of vitrifying Hanford tank wastes. The presence of chromium in Hanford waste tank solids can interfere with the efficient vitrification of this waste. Therefore, an important pretreatment objective is to remove excess chromium from Hanford tank sludges. A proposed approach to increase the effectiveness of chromium removal from Hanford tank sludge is through oxidative alkaline leaching.Chromium in tank sludge exists in both the +3 and +6 oxidation states. Chromium, when initially present in the +6 oxidation state, is effectively removed from the Hanford tank sludge solids by alkaline washing and caustic leaching. When present in the +3 oxidation state, however, chromium often dissolves poorly in simple alkaline-wash and caustic-leach solutions. Even when initially present in its +3 oxidation state, prior studies have shown that chromium exists only in caustic-leach solutions in its +6 oxidation state. Therefore, adding an oxidant to the sludge might be expected to facilitate conversion of chromium(III) to its more alkaline-soluble form (chromate [CrO 42-]) and so enhance its leaching from the sludge.This study evaluated the oxidants permanganate, MnO 4 -, and peroxynitrite, ONOO -, as selective chromium-leaching agents from washed 241-U-108 tank sludge under varying conditions of hydroxide concentration, temperature, and time. and 85°C in the absence of any added oxidant generated relatively low amounts of chromate in solution by the end of the 24-h contact time. Contacting the sludge with peroxynitrite under conditions of low-hydroxide concentration and low temperature generated chromate more rapidly than in the absence of added oxidant and also did not appear to be complete at the end of the 24-h contact time. Under conditions of high hydroxide and high temperature, peroxynitrite generated a rapid initial formation of chromate followed by a slower increase in the solution's chromate concentration. Permanganate solutions appear to generate chromate extremely rapidly, both under high temperature/high hydroxide and low temperature/low hydroxide leach conditions, with chromate formation complete within 2 hours.The total chromium concentrations in the leach solutions as measured by inductively couple plasmaatomic emission spectroscopy (ICP-AES) were compared with the chromate generated as measured by ultraviolet-visible (UV-vis) spectroscopy. Chromate and total chromium concentrations in the leachates were found to be identical within the reported ± 15% experimental error for the ICP-AES measurements.It is also desirable that transuranic elements not be leached out of the sludge, so the effectiveness of the oxidants at dissolving transuranic elements was also examined. Only the leach solution with added permanganate at 3 M [OH -] and 85°C showed a dramatic increase in plutonium dissolution. No evidence for either americium or curium in any leach solution was detected.Finally, the mass changes and final sludge compositions were evaluated using gl...

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Section: Selective Chromium Removal Under Alkaline Conditionsmentioning

confidence: 99%

Selective Leaching of Chromium from Hanford Tank Sludge 241-U-108

Rapko

Vienna²

2002

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“…However, the tank farm contents are re-distributed between phases to be consistent with 1997 mass-weighted wash factors (Colton 1997). This simulation with new inventory updates the previous TWRS Process Flowsheet simulation of Phase I1 (Orme 1996).…”

Section: Resultsmentioning

confidence: 81%

“…The methodology used to generate the TWRS inventory is similar to that used for earlier TWRS inventory development work (Orme 1996 andCerta 1996) and documented in Shelton 1996a and 1996b. The SST estimates are based on the results of the Hanford Defined Waste (HDW) model developed at the Los Alamos National Laboratory (LANL) and normalized so that the sum of component masses in the SSTs and DSTs agree with current global inventory assumptions (Kupfer et al 1997).…”

Section: Tank Waste Inventorymentioning

confidence: 99%

“…Last year's evaluation of ESW data raised a question about the capability of ESW to reduce glass volumes (Orme et al 1996).…”

Section: Sludge Wash Factorsmentioning

confidence: 99%

“…This section documents the selected SST retrieval sequence and provides a process summary which is a high-level roll-up of the TWRS Process Flowsheet (Orme et al 1996). The process summary features the recently completed standard inventory (Kupfer et al 1997) and updated water solubility and leach factors (Colton 1997).…”

Section: Privatization Phase IImentioning

confidence: 99%

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Tank waste remediation system operation and utilization plan,vol. I {ampersand} II

Kirkbride¹

1997

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An updated cost study for enhanced sludge washing of radioactive waste

DeMuth

Thayer

2003

Federal Facilities Envir J

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INTRODUCTIONThere exists approximately 100 million gallons of radioactive waste in underground storage tanks (USTs) at Department of Energy (DOE) sites across the United States. Approximately 54 million gallons are stored at the Hanford Site. The DOE is responsible for immobilization and permanent disposal of this tank waste. The Hanford tank waste is currently classified as high-level waste (HLW). While low-level waste (LLW) can generally be disposed of subsurface on-site, HLW must be disposed of in an underground repository such as that planned for Yucca Mountain. Since LLW disposal is obviously much less expensive than HLW, the plan for remediation at Hanford is to separate the UST waste into a small volume of HLW and a large volume of LLW.Of the 54 million gallons of UST waste at Hanford, approximately 20 volume-percent is solids-based, consisting primarily of sludge, and

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TWRS privatization process technical baseline

Cited by 25 publications

References 3 publications

Selective Leaching of Chromium from Hanford Tank Sludge 241-U-108

Selective Leaching of Chromium from Hanford Tank Sludge 241-U-108

Tank waste remediation system operation and utilization plan,vol. I {ampersand} II

An updated cost study for enhanced sludge washing of radioactive waste

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