Chemical Environment at Waste Package Surfaces in a High-Level Radioactive Waste Repository

Carroll, Susan; Alai, Maureen; Craig, Laura; Gdowski, G.E.; Hailey, P; Nguyen, Que Anh S.; Rard, J; Staggs, K J; Sutton, Mark A.; Wolery, T

doi:10.2172/877844

Cited by 6 publications

(15 citation statements)

References 19 publications

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“…However our experiments show that KNO 3 -NaNO 3 salt mixtures absorb water at 180˚C (Figure 2.3). This observation was also made in preliminary experiments (Carroll et al, 2005a). It is possible that the observed one to two decade drop in impedance at 180˚C reflects absorption of monolayers of water rather than full thermodynamic deliquescence observed in boiling point and solubility experiments (Carroll et al, 2005c, Rard 2004).…”

Section: Resultssupporting

confidence: 59%

“…The length of the electrodes exposed to the solution was about 2.5cm. Comparison of experiments conducted with a quartz slide as inert surface and PPS suggest that PPS is also inert to brine chemistry with no sorption of water at low relative humidity and high temperature (Carroll et al, 2005a). Resistance was monitored by an automated data acquisition system with a Gamry PCI4/300 Potentiostat in which one Pt-electrode was the working electrode and the other was the reference electrode.…”

Section: Methodsmentioning

confidence: 99%

“…The modeling results predict that mixtures of NaCl, KNO 3 , NaNO 3 and/or Ca(NO 3 ) 2 are the most prevalent mineral assemblages. Preliminary results from FY04, showed that three salt mixtures of NaCl, KNO 3 , and NaNO 3 produced brines at temperatures exceeding 190ºC (Carroll et al, 2005a;Rard 2004). This discovery raised the concern for corrosion in the first 1000 -2000 years well above 160ºC in brine compositions for which corrosion had not been previously investigated.…”

Section: Introductionmentioning

confidence: 99%

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Brines formed by multi-salt deliquescence

Carroll¹,

Rard²,

Alai³

et al. 2005

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Section: Resultssupporting

confidence: 59%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Brines formed by multi-salt deliquescence

Carroll¹,

Rard²,

Alai³

et al. 2005

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“…In this study, weightloss measurements were complemented by an array of surface analyses to measure the chemical composition, homogeneity, and thickness of the oxide layers, so as to yield a better understanding of the relationship between passive film stability and net corrosion rate in these environments. These environments are important to the Yucca Mountain safety case because recent dust deliquescence studies show that brines with high nitrate concentrations are likely to be stable on waste package surfaces at temperatures well above 150°C (Carroll et al, 2005).…”

Section: General Corrosion Of Alloy 22 From 60 To 220°cmentioning

confidence: 99%

“…Further work is needed to determine if NO 3 contributes to Alloy 22 dissolution in concentrated solutions. Recent work shows that very concentrated brines with high NO 3 /Cl solutions are stable to temperatures above 180°C (Carroll et al, 2005).…”

Section: Implications To the General Corrosion Modelmentioning

confidence: 99%

General Corrosion and Passive Film Stability

Orme¹,

Gray²,

Hayes³

et al. 2005

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Boiling Temperature and Reversed Deliquescence Relative Humidity Measurements for Mineral Assemblages in the NaCl + NaNO3 + KNO3 + Ca(NO3)2 + H2O System

et al. 2006

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+ H 2 O over the full composition range, along with those of the single salt systems.Boiling temperatures were also measured for the four component NaCl + NaNO 3 + KNO 3 + H 2 O and five component NaCl + NaNO 3 + KNO 3 + Ca(NO 3 ) 2 + H 2 O mixtures, where the solute mole fraction of Ca(NO 3 ) 2 , x{Ca(NO 3 ) 2 }, was varied between 0 and 0.25. The maximum boiling temperature found for the NaCl + KNO 3 + H 2 O system is ≈134.9 °C; for the NaNO 3 + KNO 3 + H 2 O system is ≈165.1 °C at x(NaNO 3 ) ≈ 0.46 and x(KNO 3 ) ≈ 0.54; and for the NaCl + Ca(NO 3 ) 2 + H 2 O system is 164.7 ± 0.6 °C at x{NaCl} ≈ 0.25 and x{Ca(NO 3 ) 2 } ≈ 0.75. The NaCl + NaNO 3 + KNO 3 + Ca(NO 3 ) 2 + H 2 O system forms molten salts below their maximum boiling temperatures, and the temperatures corresponding to the cessation of boiling (dry out temperatures) of these liquid mixtures were determined. These dry out temperatures range from ≈300 °C when x{Ca(NO 3 ) 2 } = 0 to ≥ 400 °C when x{Ca(NO 3 ) 2 } = 0.20 and 0.25. Mutual deliquescence/efflorescence relative humidity (MDRH/MERH) measurements were also made for the NaNO 3 + KNO 3 and NaCl + NaNO 3 + KNO 3 salt mixture from 120 to 180 °C at ambient pressure.The NaNO 3 + KNO 3 salt mixture has a MDRH of 26.4% at 120 °C and 20.0% at 150 °C.This salt mixture also absorbs water at 180 °C, which is higher than expected from the boiling temperature experiments. The NaCl + NaNO 3 + KNO 3 salt mixture was found to have a MDRH of 25.9% at 120 °C and 10.5% at 180 °C. The investigated mixture compositions correspond to some of the major mineral assemblages that are predicted to control brine composition due to the deliquescence of salts formed in dust deposited on waste canisters in the proposed nuclear repository at Yucca Mountain, Nevada. 2KEY WORDS: Boiling temperature; deliquescence relative humidity; efflorescence relative humidity; saturated solutions; sodium chloride; sodium nitrate; potassium nitrate; calcium nitrate; aqueous solutions.

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Chemical Environment at Waste Package Surfaces in a High-Level Radioactive Waste Repository

Cited by 6 publications

References 19 publications

Brines formed by multi-salt deliquescence

Brines formed by multi-salt deliquescence

General Corrosion and Passive Film Stability

Boiling Temperature and Reversed Deliquescence Relative Humidity Measurements for Mineral Assemblages in the NaCl + NaNO3 + KNO3 + Ca(NO3)2 + H2O System

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