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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Y(Al5Re)2 by Materials Project

Y(ReAl5)2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Y sites. In the first Y site, Y is bonded in a 10-coordinate geometry to four Re and sixteen Al atoms. There are two shorter (3.40 Å) and two longer (3.52 Å) Y–Re bond lengths. There are a spread of Y–Al bond distances ranging from 3.06–3.50 Å. In the second Y site, Y is bonded in a 4-coordinate geometry to fourteen Al atoms. There are a spread of Y–Al bond distances ranging from 3.07–3.28 Å. There are two inequivalent Re sites. In the first Re site, Re is bonded in a 10-coordinate geometry to one Y and ten Al atoms. There are a spread of Re–Al bond distances ranging from 2.55–2.79 Å. In the second Re site, Re is bonded in a 10-coordinate geometry to two equivalent Y and ten Al atoms. There are a spread of Re–Al bond distances ranging from 2.57–2.74 Å. There are twelve inequivalent Al sites. In the first Al site, Al is bonded in a 2-coordinate geometry to two equivalent Y, two equivalent Re, and four Al atoms. There are two shorter (2.74 Å) and two longer (3.07 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 12-coordinate geometry to one Y, two equivalent Re, and nine Al atoms. There are a spread of Al–Al bond distances ranging from 2.66–3.14 Å. In the third Al site, Al is bonded in a 2-coordinate geometry to two equivalent Y, two equivalent Re, and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.67–3.05 Å. In the fourth Al site, Al is bonded in a 2-coordinate geometry to one Y, two equivalent Re, and nine Al atoms. There are a spread of Al–Al bond distances ranging from 2.80–3.10 Å. In the fifth Al site, Al is bonded in a 12-coordinate geometry to two Y, two equivalent Re, and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.62–3.00 Å. In the sixth Al site, Al is bonded in a 2-coordinate geometry to two Y, two equivalent Re, and six Al atoms. There are a spread of Al–Al bond distances ranging from 2.66–2.96 Å. In the seventh Al site, Al is bonded in a 2-coordinate geometry to one Y, two equivalent Re, and eight Al atoms. There are two shorter (2.77 Å) and two longer (3.04 Å) Al–Al bond lengths. In the eighth Al site, Al is bonded in a 12-coordinate geometry to one Y, two equivalent Re, and nine Al atoms. There are a spread of Al–Al bond distances ranging from 2.67–2.89 Å. In the ninth Al site, Al is bonded in a 12-coordinate geometry to two Y, two equivalent Re, and eight Al atoms. The Al–Al bond length is 2.70 Å. In the tenth Al site, Al is bonded in a 11-coordinate geometry to one Y, two equivalent Re, and eight Al atoms. Both Al–Al bond lengths are 2.97 Å. In the eleventh Al site, Al is bonded in a distorted linear geometry to two equivalent Y, two Re, and four Al atoms. In the twelfth Al site, Al is bonded in a 2-coordinate geometry to one Y, two Re, and four Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(FeSn)6 by Materials Project

YFe6Sn6 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are two inequivalent Y sites. In the first Y site, Y is bonded to twelve Fe and eight Sn atoms to form distorted YFe12Sn8 hexagonal bipyramids that share faces with eight FeY2Fe4Sn6 cuboctahedra and faces with six YFe12Sn8 hexagonal bipyramids. There are four shorter (3.49 Å) and eight longer (3.51 Å) Y–Fe bond lengths. There are a spread of Y–Sn bond distances ranging from 3.02–3.17 Å. In the second Y site, Y is bonded to twelve Fe and eight Sn atoms to form distorted YFe12Sn8 hexagonal bipyramids that share corners with four equivalent YFe12Sn8 hexagonal bipyramids, faces with sixteen FeY2Fe4Sn6 cuboctahedra, and faces with four YFe12Sn8 hexagonal bipyramids. There are a spread of Y–Fe bond distances ranging from 3.49–3.53 Å. There are a spread of Y–Sn bond distances ranging from 3.03–3.17 Å. There are four inequivalent Fe sites. In the first Fe site, Fe is bonded to two equivalent Y, four equivalent Fe, and six Sn atoms to form distorted FeY2Fe4Sn6 cuboctahedra that share corners with six FeY2Fe4Sn6 cuboctahedra, edges with three equivalent FeY2Fe4Sn6 cuboctahedra, a faceface with one FeY2Fe4Sn6 cuboctahedra, and faces with four YFe12Sn8 hexagonal bipyramids. All Fe–Fe bond lengths are 2.72 Å. There are a spread of Fe–Sn bond distances ranging from 2.72–2.82 Å. In the second Fe site, Fe is bonded to two equivalent Y, four Fe, and six Sn atoms to form distorted FeY2Fe4Sn6 cuboctahedra that share corners with eight FeY2Fe4Sn6 cuboctahedra, edges with four FeY2Fe4Sn6 cuboctahedra, faces with eight FeY2Fe4Sn6 cuboctahedra, and faces with four equivalent YFe12Sn8 hexagonal bipyramids. There are two shorter (2.70 Å) and two longer (2.72 Å) Fe–Fe bond lengths. There are a spread of Fe–Sn bond distances ranging from 2.73–2.83 Å. In the third Fe site, Fe is bonded to two equivalent Y, four Fe, and six Sn atoms to form distorted FeY2Fe4Sn6 cuboctahedra that share corners with ten FeY2Fe4Sn6 cuboctahedra, edges with five FeY2Fe4Sn6 cuboctahedra, faces with five FeY2Fe4Sn6 cuboctahedra, and faces with four YFe12Sn8 hexagonal bipyramids. Both Fe–Fe bond lengths are 2.70 Å. There are a spread of Fe–Sn bond distances ranging from 2.71–2.82 Å. In the fourth Fe site, Fe is bonded in a 12-coordinate geometry to two Y, four Fe, and six Sn atoms. There are one shorter (2.70 Å) and one longer (2.71 Å) Fe–Fe bond lengths. There are a spread of Fe–Sn bond distances ranging from 2.71–2.83 Å. There are nine inequivalent Sn sites. In the first Sn site, Sn is bonded in a 8-coordinate geometry to one Y, six Fe, and one Sn atom. Both Sn–Fe bond lengths are 2.82 Å. The Sn–Sn bond length is 2.95 Å. In the second Sn site, Sn is bonded in a 6-coordinate geometry to six Fe atoms. In the third Sn site, Sn is bonded in a 12-coordinate geometry to three Y and six Fe atoms. In the fourth Sn site, Sn is bonded in a 8-coordinate geometry to two equivalent Y and six Fe atoms. In the fifth Sn site, Sn is bonded in a 12-coordinate geometry to three Y and six Fe atoms. In the sixth Sn site, Sn is bonded in a 6-coordinate geometry to six Fe atoms. In the seventh Sn site, Sn is bonded in a 7-coordinate geometry to one Y and six Fe atoms. In the eighth Sn site, Sn is bonded in a 8-coordinate geometry to one Y, six Fe, and one Sn atom. The Sn–Sn bond length is 2.94 Å. In the ninth Sn site, Sn is bonded in a 8-coordinate geometry to one Y, six Fe, and one Sn atom. The Sn–Y bond length is 3.02 Å. All Sn–Fe bond lengths are 2.83 Å. The Sn–Sn bond length is 2.95 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(CO3)2 by Materials Project

Y(CO3)2 crystallizes in the orthorhombic C222_1 space group. The structure is three-dimensional. there are two inequivalent Y sites. In the first Y site, Y is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of Y–O bond distances ranging from 2.38–2.50 Å. In the second Y site, Y is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of Y–O bond distances ranging from 2.37–2.46 Å. There are two inequivalent C sites. In the first C site, C is bonded in a distorted bent 120 degrees geometry to two O atoms. Both C–O bond lengths are 1.25 Å. In the second C site, C is bonded in a trigonal planar geometry to three O atoms. There is two shorter (1.29 Å) and one longer (1.30 Å) C–O bond length. There are seven inequivalent O sites. In the first O site, O is bonded in a 1-coordinate geometry to two Y and one C atom. In the second O site, O is bonded in a distorted T-shaped geometry to two Y and one C atom. In the third O site, O is bonded in a 1-coordinate geometry to two Y and one C atom. In the fourth O site, O is bonded in a single-bond geometry to one Y atom. In the fifth O site, O is bonded in a single-bond geometry to one Y atom. In the sixth O site, O is bonded in a bent 120 degrees geometry to one Y and one C atom. In the seventh O site, O is bonded in a bent 120 degrees geometry to one Y and one C atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Groundwater Monitoring Report, U.S. Department of Energy Y-12 National Security Complex, Oak Ridge, Tennessee

This report contains the groundwater and surface water monitoring data obtained during calendar year (CY) 2019 at the U.S. Department of Energy (DOE) Y-12 National Security Complex (Y-12) on the DOE Oak Ridge Reservation (ORR) in Oak Ridge, Tennessee. The monitoring data were obtained from wells, springs, and surface water sampling locations in three hydrogeologic regimes at Y-12. The Bear Creek Hydrogeologic Regime (Bear Creek Regime) encompasses a section of Bear Creek Valley (BCV) between the west end of Y-12 and the west end of the Bear Creek Watershed (directions are in reference to the Y-12 grid system, shown as Plant North. The Upper East Fork Poplar Creek Hydrogeologic Regime (East Fork Regime) encompasses the Y-12 industrial facilities and support structures in BCV. The Chestnut Ridge Hydrogeologic Regime (Chestnut Ridge Regime) encompasses a section of Chestnut Ridge directly south of Y-12. Background information in Section 2 of this report outlines the hydrogeologic framework for groundwater and surface water quality monitoring at Y-12 and includes an overview of the groundwater contamination in each hydrogeologic regime. Section 3 provides details regarding the groundwater and surface water sampling and analysis activities implemented under the Y-12 GWPP, including sampling locations and frequency, sample collection and handling, field measurements and laboratory analytes, quality assurance (QA)/quality control (QC) sampling, data management, and data quality assessment (DQA). However, the equivalent QA/QC or DQA information for the groundwater and surface water data associated with the monitoring programs implemented by UCOR are not included in this report and instead are deferred to referenced programmatic plans and reports issued by OREM and UCOR. Section 4 of this report presents a summary evaluation of the CY 2019 monitoring data with regard to the respective objectives of surveillance monitoring and exit pathway/perimeter monitoring. The evaluation is based primarily on the analytical results for the following principal groundwater contaminants at Y-12: nitrate, uranium, gross alpha activity, gross beta activity, and volatile organic compounds (VOCs). Section 5 summarizes the most significant findings with respect to the principal contaminants along with recommendations for any proposed changes to the ongoing groundwater and surface water quality monitoring performed under the Y-12 GWPP. Technical reports and plans cited in the narrative sections of the report are listed in Section 6. Narrative sections of this report reference several appendices. Figures (maps and diagrams) and data tables (excluding data summary tables incorporated in the narrative sections) are in Appendix A and Appendix B, respectively. Appendix C contains construction details for each well sampled during CY 2019 by either the Y-12 GWPP or UCOR, along with schematic diagrams for wells equipped with Westbay™ multiport sampling equipment or Barcad® pump systems. Appendix D supports the background summary discussion in Section 2 and provides more detailed information about the hydrogeologic framework for groundwater and surface water monitoring at Y-12, including the primary sources of groundwater contamination in each hydrogeologic regime. Results for all field measurements and laboratory analyses obtained by the Y-12 GWPP and UCOR are presented in Appendix E, which also includes the sample numbers for the QA/QC samples associated with groundwater and surface water monitoring performed by the Y-12 GWPP.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Materials Data on Y by Materials Project

Y is alpha La structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Y sites. In the first Y site, Y is bonded to twelve Y atoms to form a mixture of face, edge, and corner-sharing YY12 cuboctahedra. There are six shorter (3.56 Å) and six longer (3.59 Å) Y–Y bond lengths. In the second Y site, Y is bonded to twelve Y atoms to form a mixture of face, edge, and corner-sharing YY12 cuboctahedra. All Y–Y bond lengths are 3.59 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(Mg4Al3)4 by Materials Project

Y(Mg4Al3)4 is gamma-brass-derived structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are five inequivalent Mg sites. In the first Mg site, Mg is bonded in a 10-coordinate geometry to four Mg and six Al atoms. There are a spread of Mg–Mg bond distances ranging from 3.05–3.16 Å. There are a spread of Mg–Al bond distances ranging from 3.07–3.12 Å. In the second Mg site, Mg is bonded in a 3-coordinate geometry to five Mg, one Y, and five Al atoms. There are two shorter (3.16 Å) and two longer (3.18 Å) Mg–Mg bond lengths. The Mg–Y bond length is 3.59 Å. There are a spread of Mg–Al bond distances ranging from 2.87–3.20 Å. In the third Mg site, Mg is bonded in a 9-coordinate geometry to three equivalent Mg, one Y, and twelve Al atoms. The Mg–Y bond length is 3.32 Å. There are a spread of Mg–Al bond distances ranging from 3.19–3.24 Å. In the fourth Mg site, Mg is bonded in a 1-coordinate geometry to four equivalent Mg, one Y, and five Al atoms. There are two shorter (3.12 Å) and two longer (3.14 Å) Mg–Mg bond lengths. The Mg–Y bond length is 3.11 Å. There are a spread of Mg–Al bond distances ranging from 2.82–3.16 Å. In the fifth Mg site, Mg is bonded in a 12-coordinate geometry to seven Mg and five Al atoms. Both Mg–Mg bond lengths are 3.07 Å. There are a spread of Mg–Al bond distances ranging from 2.94–3.29 Å. Y is bonded in a 12-coordinate geometry to seven Mg and nine Al atoms. There are six shorter (3.22 Å) and three longer (3.25 Å) Y–Al bond lengths. There are three inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to eight Mg, one Y, and three Al atoms. There are one shorter (2.68 Å) and two longer (2.77 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 11-coordinate geometry to eight Mg and three Al atoms. Both Al–Al bond lengths are 2.77 Å. In the third Al site, Al is bonded in a distorted q6 geometry to seven Mg, one Y, and three Al atoms. There are one shorter (2.71 Å) and one longer (2.80 Å) Al–Al bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Selective butene formation in direct ethanol-to-C3+-olefin valorization over Zn-Y/Beta and single-atom alloy composite catalysts using in situ generated hydrogen

The selective production of C3+ olefins from renewable feedstocks, especially via C1 and C2 platform chemicals, is a critical challenge for obtaining economically viable low-carbon middle distillate transportation fuels (i.e., jet and diesel). Here, we report a multifunctional catalyst system composed of Zn-Y/Beta and “single-atom” alloy (SAA) Pt-Cu/Al2O3 which selectively catalyzes ethanol-to-olefins (C3+, ETO) valorization in the absence of cofed hydrogen, forming butenes as the primary olefin products. Beta zeolites containing predominately isolated Zn and Y metal sites catalyze ethanol upgrading steps (588 K, 3.1 kPa ethanol, ambient pressure) regardless of cofed hydrogen partial pressure (0-98.3 kPa H2), forming butadiene as the primary product (60% selectivity at 87% conversion). The Zn-Y/Beta catalyst possesses site-isolated Zn and Y Lewis acid sites (at ~7 wt% Y) and Brønsted acidic Y sites, the latter of which has been previously uncharacterized. A secondary bed of SAA Pt-Cu/Al2O3 selectively hydrogenates butadiene to butene isomers at a consistent reaction temperature using hydrogen generated in situ from ethanol-to-butadiene (ETB) conversion. This unique hydrogenation reactivity at near-stoichiometric hydrogen and butadiene partial pressures is not observed over monometallic Pt or Cu catalysts, highlighting these operating conditions as a critical SAA catalyst application area for conjugated diene selective hydrogenation at high reaction temperatures (>573 K) and low H2/diene ratios (e.g., 1:1). Single-bed steady state selective hydrogenation rates, associated apparent hydrogen and butadiene reaction orders, and DFT calculations of the Horiuti-Polanyi reaction mechanisms indicate that the unique butadiene selective hydrogenation reactivity over SAA Pt-Cu/Al2O3 reflects lower hydrogen scission barriers relative to monometallic Cu surfaces and limited butene binding energies relative to monometallic Pt surfaces. DFT calculations further indicate the preferential desorption of butene isomers over SAA Pt-Cu(111) and Cu(111) surfaces while Pt(111) surface favors subsequent butene hydrogenation reactions to form butane over butene desorption events. Under operating conditions without of hydrogen cofeeding, this combination of Zn-Y/Beta and SAA Pt-Cu catalysts can selectively form butenes (65% butenes, 78% C3+ selectivity at 94% conversion) and avoid butane formation using only in situ generated hydrogen, avoiding costly hydrogen cofeeding requirements that hinder many renewable energy processes.

Cordon, Michael↗
DOE OSTI2022

Thermal properties of field-assisted-sintered SiCN–Y 2 O 3 composites

Polymer-derived amorphous SiCN has excellent high-temperature stability and properties. To reduce the shrinkage during pyrolysis and to improve the high-temperature oxidation resistance, Y 2 O 3 was added as a filler. In this study, polymer-derived SiCN–Y 2 O 3 composites were fabricated by mixing a polymeric precursor of SiCN with Y 2 O 3 submicron powders in different ratios. The mixtures were cross-linked and pyrolyzed in argon. SiCN–Y 2 O 3 composites were processed using field-assisted sintering technology at 1350°C for 5 min under vacuum. Dense SiCN–Y 2 O 3 composite pellets were successfully made with relative density higher than 98% and homogeneous microstructure. Due to low temperature and short time of the heat-treatment, the grain growth of Y 2 O 3 was substantially inhibited. The Y 2 O 3 grain size was ~1 μm after sintering. The composites’ heat capacity, thermal diffusivity, and thermal expansion coefficients were characterized as a function of temperature. The thermal conductivity of the composites ceramics decreased as the amount of amorphous SiCN increased and the coefficient of thermal expansion (CTE) of the composites increased with Y 2 O 3 content. However, the thermal conductivity and CTE did not follow the rule of mixture. This is likely due to the partial oxidation of SiCN and the resultant impurity phases such as Y 2 SiO 5 , Y 2 Si 2 O 7 , and Y 4.67 (SiO 4 ) 3 O.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(Al5Ru)2 by Materials Project

Y(RuAl5)2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Y is bonded in a 10-coordinate geometry to four equivalent Ru and fourteen Al atoms. All Y–Ru bond lengths are 3.46 Å. There are a spread of Y–Al bond distances ranging from 3.16–3.34 Å. Ru is bonded in a 10-coordinate geometry to two equivalent Y and ten Al atoms. There are a spread of Ru–Al bond distances ranging from 2.57–2.76 Å. There are five inequivalent Al sites. In the first Al site, Al is bonded in a 2-coordinate geometry to one Y and two equivalent Ru atoms. In the second Al site, Al is bonded in a distorted linear geometry to two equivalent Y and two equivalent Ru atoms. In the third Al site, Al is bonded in a 2-coordinate geometry to two equivalent Y and two equivalent Ru atoms. In the fourth Al site, Al is bonded in a distorted bent 120 degrees geometry to one Y and two equivalent Ru atoms. In the fifth Al site, Al is bonded in a 12-coordinate geometry to one Y and two equivalent Ru atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(GeRh2)2 by Materials Project

Y(Rh2Ge)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Y is bonded in a 2-coordinate geometry to eleven Rh and five Ge atoms. There are a spread of Y–Rh bond distances ranging from 2.81–3.21 Å. There are a spread of Y–Ge bond distances ranging from 3.05–3.29 Å. There are four inequivalent Rh sites. In the first Rh site, Rh is bonded in a 12-coordinate geometry to three equivalent Y, five Rh, and four Ge atoms. There are a spread of Rh–Rh bond distances ranging from 2.73–2.99 Å. There are a spread of Rh–Ge bond distances ranging from 2.45–2.66 Å. In the second Rh site, Rh is bonded in a 5-coordinate geometry to three equivalent Y, four Rh, and three Ge atoms. There are two shorter (3.01 Å) and one longer (3.02 Å) Rh–Rh bond lengths. There are one shorter (2.51 Å) and two longer (2.55 Å) Rh–Ge bond lengths. In the third Rh site, Rh is bonded in a 6-coordinate geometry to two equivalent Y, five Rh, and four Ge atoms. There are two shorter (2.87 Å) and one longer (2.92 Å) Rh–Rh bond lengths. There are a spread of Rh–Ge bond distances ranging from 2.41–2.65 Å. In the fourth Rh site, Rh is bonded in a 4-coordinate geometry to three equivalent Y, six Rh, and four Ge atoms. There are a spread of Rh–Ge bond distances ranging from 2.50–2.71 Å. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to three equivalent Y and seven Rh atoms. In the second Ge site, Ge is bonded in a 8-coordinate geometry to two equivalent Y and eight Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Inhomogeneous Distribution and Coarsening of y″ Precipitates in a Ni-Based Superalloy and Their Effect on Creep

It has been reported that the addition of Nb or Ta in the high Ti/Al ratio alloys promotes the formation of y″ precipitates solely and greatly contributes to the elevated temperature strength and resistance to creep deformation. In this study, the y''-dominant INCONEL alloy 725 (IN725) variants (named M725-Nb/Ta) modified with a high level of Nb/Ta additions and high Ti/Al ratio was chosen as a model alloy for microstructural observation of y'' variants upon creep. Following the high temperature aging (HTA), y'' was found to be the main strengthening precipitate with no detectable y’ in both M725 alloys. After creep, the grip/gage sections of the crept M725-Nb/Ta exhibited preferential coarsening and inhomogeneous distribution of y''. That is, one or two of the variants were preferentially coarsened at the expense of another variant, and sandwich-like structures, comprising of cubic y′ precipitates with small y″ discs on each face, were formed. This variant selection behavior taking place in the grip section with no stress applied was different from the typical stress-induced variant selection in previous literature. However, the sample with prior high temperature exposure (700 °C for 500 hours) with varying y″ characteristics demonstrated a similar trend of creep when compared with those in the HTA sample, suggesting that the coarsening and the inhomogeneous distribution of y'' was not the determinant of creep life in bulk M725-Nb/Ta alloys.

Hung, Chang-Yu↗
DOE OSTI2020

Y-12 Groundwater Protection Program Monitoring Well Inspection and Maintenance Plan

This plan describes the systematic approach for: inspecting the physical condition of monitoring wells at Y-12, determining maintenance needs that extend the life of a well, and identifying those wells that no longer meet acceptable monitoring well design or well construction standards and require plugging and abandonment. The inspection and maintenance of groundwater monitoring wells is one of the primary management strategies of the Y-12 Groundwater Protection Program (GWPP) Management Plan, that is, the “proactive stewardship of the extensive monitoring well network at Y-12" (Consolidated Nuclear Security, L.L.C. [CNS], 2018). Effective stewardship, and a program of routine inspections of the physical condition of each monitoring well, ensures that representative water-quality samples and hydrologic data are obtained from the well network and protects the subsurface environment. In accordance with the Y-12 GWPP Monitoring Optimization Plan (MOP) for Groundwater Monitoring Wells at the Y-12 National Security Complex, Oak Ridge, Tennessee (CNS, 2017), the status designation (active or inactive) for each well determines the scope and extent of well inspections and maintenance activities. This plan, in conjunction with the above document, formalizes the GWPP approach to focus available resources on monitoring wells which provide the most useful data, and for that reason the GWPP inspects and performs maintenance on the wells sampled by the GWPP. This plan applies to groundwater monitoring wells installed at Y-12 and the related waste management facilities located within the three hydrogeologic regimes: (1) the Bear Creek Hydrogeologic Regime (Bear Creek Regime), (2) the Upper East Fork Poplar Creek Hydrogeologic Regime (East Fork Regime), and (3) the Chestnut Ridge Hydrogeologic Regime (Chestnut Ridge Regime). The Bear Creek Regime encompasses the section of Bear Creek Valley (BCV) immediately west of Y-12. The East Fork Regime encompasses most of the Y-12 process, operations, and support facilities in BCV west of Scarboro Road. The Chestnut Ridge Regime is directly south of Y-12 and encompasses a section of Chestnut Ridge that is bounded to the west by a surface drainage feature (Dunaway Branch, located immediately west of Industrial Landfill II) and by Scarboro Road to the east. The GWPP maintains an extensive database of geographic and construction details and related information for the monitoring wells in each hydrogeologic regime in the Updated Subsurface Database for Bear Creek Valley, Chestnut Ridge, and Parts of Bethel Valley on the U.S. DOE Oak Ridge Reservation (CNS, 2019). A detailed description of the hydrogeologic framework at Y-12 can be found in the GWPP Management Plan (CNS, 2018).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Conceptual Model Update of Mercury Sources and Flux at Y-12 and Upper East Fork Poplar Creek, Oak Ridge,Tennessee

The interactions between the key processes that control the fate and transport of mercury (Hg) in the sediments, groundwater, and stream water within the Y-12 National Security Complex (Y-12) in Oak Ridge, Tennessee are complex, and many aspects are not well understood. In contaminated environments such as Y-12, conceptual models are frequently developed to aid in visualizing and understanding the dynamic nature of the hydrologic, geochemical, and physical environment. These conceptual models integrate data in an internally consistent manner to understand processes that control the fate and transport of contaminants. Over the past few decades of environmental investigation at Y-12, a number of conceptual models have been developed to identify and define various technical processes at various scales. The main purpose of the activities described in this report is to update the 2011 conceptual model for Upper East Fork Poplar Creek using the most recent Hg concentration and flux data and informed scientific interpretation. Emphasis was placed on improving the previous model by implementing a more detailed spatial and temporal approach to visualize transport pathways in the watershed and trends in flux and concentration over time, and to compare baseflow and stormflow system dynamics. Detailed descriptions of historical and current Hg sources and transport pathways are also provided for the east and west ends of the facility. This conceptual model will allow the US Department of Energy to evaluate past and present remedial activities and provide a strong technical basis for prioritizing and optimizing remedial responses in a cost-effective and efficient manner. Twenty years ago, Hg flux from Outfall (OF) 200 at the headwaters of East Fork Poplar Creek represented approximately 20% of the overall flux leaving Y-12. By the time of the 2011 conceptual model report, that percentage had increased to 70%–80%. Flux estimates compiled for this report using data from 2009 to 2018 show that OF200 accounted for roughly 60% of the flux leaving Y-12. The relative role of the four storm drain conduits to OF200 appeared similar to 2011, with OF163 being the greatest contributor to downstream flux. An increase in Hg concentrations and flux occurred throughout and downstream of west end storm drains in 2011 in response to a storm drain cleanout. Leading up to the 2011 storm drain cleanout, annual baseflow flux was higher at OF200A6 than at Station 17. From 2011 to 2018, the trend reversed with concentrations and flux being higher at Station 17 than at OF200A6. A spike in concentrations occurred in July 2018, potentially due to a one-time influx of Hg that occurred during COLEX decontamination and decommissioning activities at Y-12. This report includes recommendations for improving our conceptual understanding of Hg sources, transport pathways, and flux at Y-12. Important recommendations include further evaluation of transport pathways, concurrent measurement of Hg concentration and flux under baseflow and stormflow conditions at multiple sites, and research to understand the connections among periphyton and methylmercury concentration, bioavailability, and bioaccumulation. Ongoing facility decontamination and decommissioning efforts, site characterization, remedial actions, and research are facilitating the collection of new Hg data at Y-12. The conceptual model update provided herein takes advantage of the extensive recent Hg sampling to provide an updated assessment of Hg mass balance and support a refined understanding of Hg behavior at or near Y-12. This assessment should assist in future environmental management decisions and in mitigating the impacts of Hg on the surrounding environment.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Materials Data on Y(TiGa2)2 by Materials Project

Y(TiGa2)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Y is bonded in a distorted square co-planar geometry to twelve Ga atoms. There are four shorter (2.90 Å) and eight longer (3.33 Å) Y–Ga bond lengths. Ti is bonded in a 10-coordinate geometry to two equivalent Ti and eight Ga atoms. Both Ti–Ti bond lengths are 2.74 Å. All Ti–Ga bond lengths are 2.80 Å. There are six inequivalent Ga sites. In the first Ga site, Ga is bonded in a 11-coordinate geometry to three equivalent Y, four equivalent Ti, and four Ga atoms. There are two shorter (2.66 Å) and two longer (2.93 Å) Ga–Ga bond lengths. In the second Ga site, Ga is bonded in a 11-coordinate geometry to three equivalent Y, four equivalent Ti, and four Ga atoms. There are one shorter (2.66 Å) and two longer (2.93 Å) Ga–Ga bond lengths. In the third Ga site, Ga is bonded in a 11-coordinate geometry to three equivalent Y, four equivalent Ti, and four Ga atoms. There are one shorter (2.66 Å) and two longer (2.93 Å) Ga–Ga bond lengths. In the fourth Ga site, Ga is bonded in a 11-coordinate geometry to three equivalent Y, four equivalent Ti, and four Ga atoms. Both Ga–Ga bond lengths are 2.66 Å. In the fifth Ga site, Ga is bonded in a 11-coordinate geometry to three equivalent Y, four equivalent Ti, and four Ga atoms. The Ga–Ga bond length is 2.66 Å. In the sixth Ga site, Ga is bonded in a 11-coordinate geometry to three equivalent Y, four equivalent Ti, and four Ga atoms. The Ga–Ga bond length is 2.66 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(Al5Fe)2 by Materials Project

YFe2Al10 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Y is bonded in a 10-coordinate geometry to four equivalent Fe and sixteen Al atoms. All Y–Fe bond lengths are 3.41 Å. There are a spread of Y–Al bond distances ranging from 3.10–3.65 Å. Fe is bonded in a 10-coordinate geometry to two equivalent Y and ten Al atoms. There are a spread of Fe–Al bond distances ranging from 2.51–2.71 Å. There are five inequivalent Al sites. In the first Al site, Al is bonded in a 2-coordinate geometry to two equivalent Y, two equivalent Fe, and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.59–2.82 Å. In the second Al site, Al is bonded to one Y, two equivalent Fe, and nine Al atoms to form a mixture of distorted corner and face-sharing AlYAl9Fe2 cuboctahedra. There are a spread of Al–Al bond distances ranging from 2.70–3.00 Å. In the third Al site, Al is bonded in a 2-coordinate geometry to two equivalent Y, two equivalent Fe, and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.56–2.74 Å. In the fourth Al site, Al is bonded in a 2-coordinate geometry to one Y, two equivalent Fe, and eight Al atoms. There are one shorter (2.69 Å) and two longer (2.78 Å) Al–Al bond lengths. In the fifth Al site, Al is bonded in a 2-coordinate geometry to two equivalent Y, two equivalent Fe, and eight Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(AlCu)6 by Materials Project

Y(CuAl)6 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Y is bonded in a 12-coordinate geometry to twelve Cu and eight Al atoms. There are four shorter (3.21 Å) and eight longer (3.31 Å) Y–Cu bond lengths. There are a spread of Y–Al bond distances ranging from 2.97–3.10 Å. There are two inequivalent Cu sites. In the first Cu site, Cu is bonded in a 12-coordinate geometry to two equivalent Y, four Cu, and six Al atoms. There are two shorter (2.52 Å) and two longer (2.54 Å) Cu–Cu bond lengths. There are a spread of Cu–Al bond distances ranging from 2.53–2.65 Å. In the second Cu site, Cu is bonded to two equivalent Y, four equivalent Cu, and six Al atoms to form a mixture of distorted edge, face, and corner-sharing CuY2Al6Cu4 cuboctahedra. There are a spread of Cu–Al bond distances ranging from 2.64–2.74 Å. There are three inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to one Y, six Cu, and three Al atoms. There are one shorter (2.62 Å) and two longer (2.84 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 8-coordinate geometry to one Y, six Cu, and three Al atoms. There are one shorter (2.64 Å) and two longer (2.90 Å) Al–Al bond lengths. In the third Al site, Al is bonded in a 12-coordinate geometry to two equivalent Y, six Cu, and four Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Experimental characterization and atomistic simulation of grain boundary segregation in Mg-Y alloys

As a rare earth solute element in Mg alloys, Y has the beneficial effects of increasing both the strength and the ductility as well as weakening the crystallographic texture. To achieve a more fundamental understanding on how Y addition affects the microstructural evolution and mechanical properties, the Y segregation behavior at grain boundaries was investigated in Mg-1wt.%Y and Mg-7wt.%Y alloys at different conditions. The segregation intensity and its dependence on the grain boundary misorientation angle were experimentally characterized and computationally predicted. Strong segregation at grain boundaries was observed in both low and high Y-containing alloys. Y segregation was found to remain in alloy Mg-7Y after high-temperature annealing heat treatment at 540 °C. No direct correlation between the Y segregation intensity and the grain boundary misorientation angle could be established based on either the experimental characterization or the atomistic simulation with a spectral model. We thus conclude that grain boundary segregation of Y is independent of grain boundary misorientation angle.

Grain boundary↗
DOE OSTI2022

Y(III) Sorption at the Orthoclase (001) Surface Measured by X-ray Reflectivity

Interactions of heavy metals with charged mineral surfaces control their mobility in the environment. Here, we investigate the adsorption of Y(III) onto the orthoclase (001) basal plane, the former as a representative of rare earth elements and an analogue of trivalent actinides and the latter as a representative of naturally abundant K-feldspar minerals. In this study, we apply in situ high-resolution X-ray reflectivity to determine the sorption capacity and molecular distribution of adsorbed Y species as a function of the Y 3+ concentration, [Y 3+ ], at pH 7 and 5. With [Y 3+ ] ≥ 1 mM at pH 7, we observe an inner-sphere (IS) sorption complex at a distance of ~1.5 Å from the surface and an outer-sphere (OS) complex at 3–4 Å. Based on the adsorption height of the IS complex, a bidentate, binuclear binding mode, in which Y 3+ binds to two terminal oxygens, is proposed. In contrast, mostly OS sorption is observed at pH 5. The observed maximum Y coverage is ~1.3 Y 3+ /A UC (A UC : area of the unit cell = 111.4 Å 2 ) for all the investigated pH values and Y concentrations, which is in the expected range based on the estimated surface charge of orthoclase (001).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗