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13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on NaNO3 by Materials Project

NaNO3 is Calcite structured and crystallizes in the trigonal R-3c space group. The structure is three-dimensional. Na1+ is bonded to six equivalent O2- atoms to form corner-sharing NaO6 octahedra. The corner-sharing octahedral tilt angles are 64°. All Na–O bond lengths are 2.45 Å. N5+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All N–O bond lengths are 1.27 Å. O2- is bonded in a trigonal planar geometry to two equivalent Na1+ and one N5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaNO3 by Materials Project

NaNO3 is Calcite-like structured and crystallizes in the trigonal R32 space group. The structure is three-dimensional. Na1+ is bonded to six equivalent O2- atoms to form distorted corner-sharing NaO6 pentagonal pyramids. All Na–O bond lengths are 2.45 Å. N5+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All N–O bond lengths are 1.27 Å. O2- is bonded in a trigonal planar geometry to two equivalent Na1+ and one N5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaNO3 by Materials Project

NaNO3 is Calcite-like structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six O2- atoms to form distorted corner-sharing NaO6 octahedra. The corner-sharing octahedra tilt angles range from 62–67°. There are a spread of Na–O bond distances ranging from 2.44–2.64 Å. In the second Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.43–2.79 Å. In the third Na1+ site, Na1+ is bonded to six O2- atoms to form corner-sharing NaO6 octahedra. The corner-sharing octahedra tilt angles range from 62–66°. There are a spread of Na–O bond distances ranging from 2.32–2.47 Å. In the fourth Na1+ site, Na1+ is bonded to six O2- atoms to form corner-sharing NaO6 octahedra. The corner-sharing octahedra tilt angles range from 64–67°. There are a spread of Na–O bond distances ranging from 2.39–2.52 Å. There are four inequivalent N5+ sites. In the first N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.26 Å) and two longer (1.27 Å) N–O bond length. In the second N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. All N–O bond lengths are 1.27 Å. In the third N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. All N–O bond lengths are 1.27 Å. In the fourth N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. All N–O bond lengths are 1.27 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two Na1+ and one N5+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two Na1+ and one N5+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two Na1+ and one N5+ atom. In the fourth O2- site, O2- is bonded in a trigonal planar geometry to two Na1+ and one N5+ atom. In the fifth O2- site, O2- is bonded in a trigonal planar geometry to two Na1+ and one N5+ atom. In the sixth O2- site, O2- is bonded in a trigonal planar geometry to two Na1+ and one N5+ atom. In the seventh O2- site, O2- is bonded in a trigonal planar geometry to two Na1+ and one N5+ atom. In the eighth O2- site, O2- is bonded in a trigonal planar geometry to two Na1+ and one N5+ atom. In the ninth O2- site, O2- is bonded in a trigonal planar geometry to two Na1+ and one N5+ atom. In the tenth O2- site, O2- is bonded in a trigonal planar geometry to two Na1+ and one N5+ atom. In the eleventh O2- site, O2- is bonded in a trigonal planar geometry to two Na1+ and one N5+ atom. In the twelfth O2- site, O2- is bonded in a trigonal planar geometry to two Na1+ and one N5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na3MoNO3 by Materials Project

Na3MoNO3 is Stannite-like structured and crystallizes in the orthorhombic Pmn2_1 space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to one N3- and three O2- atoms to form NaNO3 tetrahedra that share corners with four equivalent MoNO3 tetrahedra and corners with eight equivalent NaNO3 tetrahedra. The Na–N bond length is 2.39 Å. There are one shorter (2.37 Å) and two longer (2.39 Å) Na–O bond lengths. In the second Na1+ site, Na1+ is bonded to one N3- and three O2- atoms to form NaNO3 tetrahedra that share corners with four equivalent MoNO3 tetrahedra and corners with eight NaNO3 tetrahedra. The Na–N bond length is 2.36 Å. There are a spread of Na–O bond distances ranging from 2.32–2.35 Å. Mo6+ is bonded to one N3- and three O2- atoms to form MoNO3 tetrahedra that share corners with twelve NaNO3 tetrahedra. The Mo–N bond length is 1.75 Å. There is one shorter (1.86 Å) and two longer (1.87 Å) Mo–O bond length. N3- is bonded to three Na1+ and one Mo6+ atom to form NNa3Mo tetrahedra that share corners with twelve ONa3Mo tetrahedra. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to three Na1+ and one Mo6+ atom to form distorted ONa3Mo tetrahedra that share corners with four equivalent NNa3Mo tetrahedra and corners with eight ONa3Mo tetrahedra. In the second O2- site, O2- is bonded to three Na1+ and one Mo6+ atom to form distorted ONa3Mo tetrahedra that share corners with four equivalent NNa3Mo tetrahedra and corners with eight equivalent ONa3Mo tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Reactions during conversion of simplified low-activity waste glass feeds

The mechanisms that affect the incorporation of 99Tc, a volatile radioactive component of concern, into glass melt during vitrification of low-activity waste (LAW) are being investigated to develop the method to increase the retention of 99Tc in glass waste form. Previous studies with simulated LAW glass feeds (slurry mixture of liquid waste and chemical/mineral additives) demonstrated that the early stage feed-to-glass conversion reactions below 800°C are critical for the Re (used as a nonradioactive surrogate of 99Tc) retention in glass. To examine the effect of feed composition on the feed-to-glass conversion reactions, simplified systems containing major LAW components (NaNO3 and NaOH) and representative additive components (SiO2 and H3BO3) were designed and tested. The ratio of H3BO3 to NaNO3 was varied in three-component system without NaOH and that of NaOH to NaNO3 was varied in the four-component system at a fixed H3BO3 to NaNO3 ratio. As a first step of testing with simplified feeds, this study applied thermal analyses and phase characterization of the reacting feeds, which were performed without the addition of Re, to investigate the evolution of salt phases during slurry drying process and upon heating of dried feeds.

Jin, Tongan↗
DOE OSTI2020

Materials Data on Na4Al3Si3CNO13 by Materials Project

Na4Al3Si3CNO13 crystallizes in the orthorhombic Ccc2 space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 tetrahedra that share a cornercorner with one NaO4 tetrahedra, corners with three AlO4 tetrahedra, and corners with three SiO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.36–2.50 Å. In the second Na1+ site, Na1+ is bonded to one N3- and three O2- atoms to form distorted NaNO3 tetrahedra that share a cornercorner with one NaNO3 tetrahedra, corners with three AlO4 tetrahedra, and corners with three SiO4 tetrahedra. The Na–N bond length is 2.48 Å. There are a spread of Na–O bond distances ranging from 2.36–2.39 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four NaO4 tetrahedra and corners with four SiO4 tetrahedra. There is one shorter (1.75 Å) and three longer (1.76 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four NaO4 tetrahedra and corners with four equivalent SiO4 tetrahedra. All Al–O bond lengths are 1.76 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four NaO4 tetrahedra and corners with four AlO4 tetrahedra. All Si–O bond lengths are 1.64 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four NaO4 tetrahedra and corners with four equivalent AlO4 tetrahedra. All Si–O bond lengths are 1.64 Å. C4+ is bonded in a linear geometry to one N3- and one O2- atom. The C–N bond length is 1.20 Å. The C–O bond length is 1.23 Å. N3- is bonded in a 3-coordinate geometry to two equivalent Na1+ and one C4+ atom. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Na1+ and one C4+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Nitrate and Nitrite Incompatibility with Hydroxide Ions in Concentrated NaOH Solutions: Implications for Hydroxide and Gibbsite Reactivity in Alkaline Nuclear Waste

Electrolyte solutions in alkaline nuclear waste contain aluminate, hydroxide, nitrate and nitrite with sodium as the predominant counterion. The salts of these ions are highly soluble, so the liquids are highly concentrated. This study found that there is a substantial incompatibility between the hydroxide and nitrate and/or nitrate ions. This was determined by the observations that adding just one molal of NaNO2 or NaNO3 to saturated NaOH solution precipitation of 12 moles of NaOH·H2O salt, whereas the common ion effect would have expected only about 1 mole to precipitate. Further analysis indicates that the presence of nitrate and nitrite drastically increases the reactivity of sodium hydroxide ions in solution, which likely influences the reactivity of other hydroxide-mediated reactions. This enhanced reactivity is likely because it disrupts large Na+-OH- ion networks because nitrate and nitrite do not fit in those ion networks similarly to how some ions cannot substitute into a foreign crystal lattice. In contrast, the aluminate ion did not have the same large incompatibility with hydroxide.

Nitrite, Nitrate, Aluminate, NaOH*H2O, Ion-aggrega↗
DOE OSTI2022

Corrosion resistance of high nickel alloys in solar salt at 600 °C for up to 4000 h

This study focuses on the time dependent performance of the corrosion resistance of IN625, H230 and 740H alloys in the solar salt (60 wt% NaNO3, 40 wt% KNO3, at 600 °C) for up to 4000 h. Alloy IN625 showed the lowest mass change with parabolic oxidation kinetics that tends to stabilize with exposure time. Both 740H and H230 alloys deviated from the parabolic oxidation behavior beyond the 3000 h of exposure. Alloy 740H showed the highest mass loss due to the nonuniform surface oxidation and the high chromium dissolution rate. Internal oxidation was noticed with Alloy H230 due to the high tungsten concentrations.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Plutonium Retention by Crystalline Silicotitanate under Hyperalkaline Conditions Relevant to Tank-Side Cesium-Removal at the Hanford Site

Crystalline silicotitanate (CST) is used in Hanford’s Tank-Side Cesium-Removal (TSCR) process to selectively remove Cs-137 from highly caustic, nitrate-rich tank supernatants. Recent testing with actual waste samples suggests that CST can also retain measurable plutonium (Pu), which could affect radiological classification and disposal pathways for spent CST. To quantify this behavior, Pu partitioning to CST was studied under Hanford-relevant conditions using batch-contact experiments in a representative simulant (2 M NaNO3, 0.7 M NaOH). Isotherm data were measured and distribution ratios calculated, with Cs+ uptake used as benchmark. Under low-carbonate conditions, Pu was retained strongly by CST in systems initially contacted with either PuO2 nanoparticles (Pu(IV)) or aqueous Pu(VI), with distribution ratios of ~2,200–3,700 mL/g, generally exceeding those for Cs+ (~400–1,000 mL/g). Increasing carbonate concentration strongly reduced PuO2 nanoparticle retention; at [Na2CO3] = 1 M, distribution ratios decreased by up to one order of magnitude to roughly 100–300 mL/g. Electron microscopy suggests that Pu retention involves a combination of mechanisms such as PuO2 NP aggregation induced by CST leachate components, and association with CST bead surfaces.

Neumann, J.↗
DOE OSTI2020

Materials Data on Na8NO3 by Materials Project

Na8NO3 is Fluorite-derived structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Na1+ is bonded to one N2- and three equivalent O2- atoms to form a mixture of edge and corner-sharing NaNO3 tetrahedra. The Na–N bond length is 2.47 Å. All Na–O bond lengths are 2.44 Å. N2- is bonded in a body-centered cubic geometry to eight equivalent Na1+ atoms. O2- is bonded in a body-centered cubic geometry to eight equivalent Na1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Radiolytic Gas Generation and Pressure Buildup in a Closed System Containing Mo-99 Solution

This study measured radiolytic gas generation and pressure buildup in a sealed stainless-steel system containing alkaline Mo-99 solution with added sodium nitrate as a hydrogen suppressant. In each of two experiments, approximately 200 Ci of Mo-99 solution was transferred into a closed experimental vessel inside a hot cell, isolated, and monitored for pressure rise caused by gas generation during radioactive decay. After pressure buildup, headspace gas samples were collected and analyzed by mass spectrometry to determine hydrogen and oxygen concentrations. The purpose was to quantify the magnitude of pressure buildup in a closed system and to characterize the gas composition produced by radiolysis of the Mo-99 target solution under representative handling and storage conditions. The two experiments used similar total Mo-99 activity but differed in solution volume, headspace volume, and leak integrity. In the first experiment, 197.5 Ci of Mo-99 in 16.92 mL of solution was loaded into a vessel with a 31.1-mL headspace; a small leak was later identified, and the measured peak pressure of 46 psig was extrapolated to about 70 psig in the absence of leakage. The headspace gas from this experiment contained about 21.4% H2 and 63.4% O2, but the composition was influenced by preferential hydrogen loss through the leak. In the second experiment, 193 Ci of Mo-99 in 5.41 mL of solution with 0.46 g NaNO3 was loaded into a vessel with a larger 42.61 mL headspace, and no detectable leak was observed. This experiment reached a peak pressure of 38 psig, and the measured gas composition was approximately 28.2% H2 and 51.5% O2. Because the second experiment was leak-free, it is considered the more reliable indicator of the true pressure buildup and intrinsic radiolytic gas composition of the Mo-99 solution.

Chemerisov, Sergey D.↗
DOE OSTI2025

Colloidal Behavior of Plutonium Oxide in Concentrated Electrolyte Solutions

The Hanford Site in Washington State manages legacy high-level radioactive waste streams that display major chemistry and engineering challenges, including the high salt levels and pH values that correspond to conditions under which many classical concepts describing chemical reactivity cannot be applied. One particular challenge that needs to be tackled at Hanford is that Pu concentrations, [Pu], in the soluble phases of the tank wastes are higher than expected based on the solubility of crystalline PuO2, which is widely accepted to be caused by the formation of PuO2 colloid, consisting of nano- to submicron-sized particles (PuO2 NPs). Fundamental research underpinning the behavior of PuO2 NPs under conditions not only relevant to the Hanford tank waste but at high ionic strength in general is needed to reliably predict the chemical reactivity of PuO2 NPs and develop engineering solutions to safely and efficiently process high-level radioactive waste into forms suitable for long-term storage. In this work, we study the behavior of PuO2 NPs (particle size ~100 nm) under high ionic strength conditions by reacting it with highly concentrated (up to 5 M) salt solutions. We explore different electrolyte compositions to elucidate the impact of different anions (NO3-, Cl-, ClO4-, SO42-, C2O42-, CO32-) on the stability of PuO2 NP in the acidic and alkaline pH regime. PuO2 NP aggregation and precipitation as function electrolyte concentration is tracked by a combination of liquid scintillation counting, dynamic light scattering for determination of particle size distributions, and zeta potentials as a proxy for particle charge. At acidic pH, electrolytes containing non-coordinating anions, such as NaNO3, NaCl, and NaClO4 mostly stabilize PuO2 NPs over a large electrolyte concentration range, showing only subtle differences in their reactivity. Other electrolyte anions show a more pronounced effect on the PuO2 NP stability: SO42-, binds directly to the particles’ surface, reverses the particle charge, and precipitates the PuO2 NPs efficiently even at intermediate sulfate concentrations (>0.1 M). In contrast, C2O42- is found to lead to high [Pu] in solution, in the milli-molar range, even at mildly acidic pH (~4). Thermodynamic modeling of the dissolved Pu concentrations using PHREEQC is unable to predict the observed [Pu] in the acidic pH regime, supporting the influence of colloids in maintaining elevated [Pu]. It is noteworthy that the current thermodynamic databases do not include constants for colloidal Pu phases and cannot accurately predict many of the high ionic strength solutions relevant to this work. The mechanisms and models responsible for these observations will need further investigation in the future. At high pH values (~12), PuO2 NPs exhibits classical sol-gel chemistry, meaning that upon destabilization of the colloidal sol, for example by addition of concentrated NaOH, highly porous and viscid PuO2 coagulates are formed that consist of a three-dimensional network likely held together by physical interactions. The PuO2 NP coagulate shows no significant reversibility of the aggregation when contacted with concentrated brines; however, PuO2 NPs can be efficiently resuspended in solution by addition of diluted electrolytes, alkaline solutions containing high amounts of carbonate, or simple addition of water. Especially carbonate is shown to stabilize PuO2 NPs in solution at high pH, characterized by stable colloidal suspensions that are resistant against sedimentation during centrifugation. Thermodynamic modeling of the carbonate system was able to predict an increasing dissolved Pu concentration with increasing carbonate concentration. However, the model was profoundly sensitive to the fixed redox potential and does not include any thermodynamic constants for colloidal Pu species.

Neumann, Julia↗