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94 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Cs3Zr7BCl20 by Materials Project

Cs3Zr7Cl20B crystallizes in the trigonal R-3c space group. The structure is three-dimensional and consists of six boron molecules and one Cs3Zr7Cl20 framework. In the Cs3Zr7Cl20 framework, Cs1+ is bonded to twelve Cl1- atoms to form distorted CsCl12 cuboctahedra that share corners with four equivalent CsCl12 cuboctahedra, corners with six equivalent ZrCl5 square pyramids, edges with four equivalent CsCl12 cuboctahedra, edges with two equivalent ZrCl5 square pyramids, edges with two equivalent ZrCl5 trigonal bipyramids, and faces with two equivalent ZrCl5 square pyramids. There are a spread of Cs–Cl bond distances ranging from 3.62–4.07 Å. There are two inequivalent Zr2+ sites. In the first Zr2+ site, Zr2+ is bonded to five Cl1- atoms to form ZrCl5 square pyramids that share corners with three equivalent CsCl12 cuboctahedra, corners with five equivalent ZrCl5 square pyramids, an edgeedge with one CsCl12 cuboctahedra, and a faceface with one CsCl12 cuboctahedra. There are a spread of Zr–Cl bond distances ranging from 2.56–2.81 Å. In the second Zr2+ site, Zr2+ is bonded to five Cl1- atoms to form ZrCl5 trigonal bipyramids that share edges with six equivalent CsCl12 cuboctahedra. There are three shorter (2.39 Å) and two longer (2.47 Å) Zr–Cl bond lengths. There are five inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 2-coordinate geometry to two equivalent Cs1+ and two equivalent Zr2+ atoms. In the second Cl1- site, Cl1- is bonded in a 2-coordinate geometry to one Cs1+ and two equivalent Zr2+ atoms. In the third Cl1- site, Cl1- is bonded in a distorted single-bond geometry to three equivalent Cs1+ and one Zr2+ atom. In the fourth Cl1- site, Cl1- is bonded in a 2-coordinate geometry to two equivalent Cs1+ and two equivalent Zr2+ atoms. In the fifth Cl1- site, Cl1- is bonded in a distorted single-bond geometry to two equivalent Cs1+ and one Zr2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SiB11H10C4F11 by Materials Project

BSiC3H9FB5CHF5(FB1)5 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of twenty boron monofluoride molecules, four B5CHF5 clusters, and four BSiC3H9F clusters. In each B5CHF5 cluster, there are five inequivalent B+1.91+ sites. In the first B+1.91+ site, B+1.91+ is bonded in a distorted bent 120 degrees geometry to one C4- and one F1- atom. The B–C bond length is 1.72 Å. The B–F bond length is 1.37 Å. In the second B+1.91+ site, B+1.91+ is bonded in a distorted bent 120 degrees geometry to one C4- and one F1- atom. The B–C bond length is 1.73 Å. The B–F bond length is 1.37 Å. In the third B+1.91+ site, B+1.91+ is bonded in a distorted bent 120 degrees geometry to one C4- and one F1- atom. The B–C bond length is 1.72 Å. The B–F bond length is 1.37 Å. In the fourth B+1.91+ site, B+1.91+ is bonded in a distorted bent 120 degrees geometry to one C4- and one F1- atom. The B–C bond length is 1.72 Å. The B–F bond length is 1.37 Å. In the fifth B+1.91+ site, B+1.91+ is bonded in a distorted bent 120 degrees geometry to one C4- and one F1- atom. The B–C bond length is 1.72 Å. The B–F bond length is 1.37 Å. C4- is bonded in a 1-coordinate geometry to five B+1.91+ and one H1+ atom. The C–H bond length is 1.09 Å. H1+ is bonded in a single-bond geometry to one C4- atom. There are five inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one B+1.91+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one B+1.91+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one B+1.91+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one B+1.91+ atom. In the fifth F1- site, F1- is bonded in a single-bond geometry to one B+1.91+ atom. In each BSiC3H9F cluster, B+1.91+ is bonded in a single-bond geometry to one F1- atom. The B–F bond length is 1.45 Å. Si4- is bonded in a trigonal pyramidal geometry to three C4- and one F1- atom. All Si–C bond lengths are 1.85 Å. The Si–F bond length is 1.96 Å. There are three inequivalent C4- sites. In the first C4- site, C4- is bonded to one Si4- and three H1+ atoms to form corner-sharing CSiH3 tetrahedra. All C–H bond lengths are 1.10 Å. In the second C4- site, C4- is bonded to one Si4- and three H1+ atoms to form corner-sharing CSiH3 tetrahedra. All C–H bond lengths are 1.10 Å. In the third C4- site, C4- is bonded to one Si4- and three H1+ atoms to form corner-sharing CSiH3 tetrahedra. All C–H bond lengths are 1.10 Å. There are nine inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. F1- is bonded in a bent 150 degrees geometry to one B+1.91+ and one Si4- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Post-closure Nuclear Criticality Safety Evaluations for Disposition of Criticality Control Overpacks at the Waste Isolation Pilot Plant

The Waste Isolation Pilot Plant (WIPP) is a geological repository in southern New Mexico that provides for disposal of transuranic (TRU) wastes from atomic energy defense activities. The Sandia National Laboratories (Sandia) Report, Consideration of Nuclear Criticality When Disposing of Transuranic Waste at the Waste Isolation Pilot Plant, addresses nuclear criticality safety based on the projected inventory characteristics for the initial compliance certification application of WIPP in 1996. As the inventory, waste forms, and disposal package designs change, revised or new analyses are necessary to demonstrate acceptability for these configurations within the WIPP safety basis and compliance with 10,000-year post-closure standards of the US Environmental Protection Agency (EPA). Saylor and Scaglione evaluated criticality control overpacks (CCOs) in 2017 based on conservative assumptions for post-closure repository structural conditions with resulting effects on containers and container spacing, The Saylor and Scaglione evaluation of CCOs addressed a single waste configuration that represents the Surplus Plutonium Disposition Program’s dilute and dispose waste form and composition. This initial CCO study demonstrated that 50 grams of boron carbide (B 4 C) per CCO is sufficient to ensure post-closure criticality safety based on a well-mixed waste composition, and Oak Ridge National Laboratory (ORNL) subsequently determined that this amount of B 4 C does not require constraints on moisture or plastic present as moderator. The Saylor and Scaglione analysis conservatively assumes repository room closure that eliminates all space between fissile gram equivalent (FGE) 239 Pu masses. The close-packed array was selected based on limited availability of repository salt creep modeling results at that time. In 2019, Brickner provided additional evaluations for pipe overpack containers (POCs), building on the conservative basis provided by Saylor and Scaglione. Brickner’s 2019 analysis made use of new geomechanical data for post-closure spacing that rely on advances in repository modeling as documented in the work by Reedlunn and Bean. This current CCO evaluation for generic waste materials expands on earlier work performed at ORNL and includes evaluation of CCOs across a much broader range of possible waste compositions and geometries. This evaluation is intended to provide input for the required feature, event and process (FEP) screening to determine if post-closure criticality must be included as an event in the 10,000-year regulatory evaluation. As such, the approach to modeling post-closure criticality presented in this report has been coordinated with the Sandia team responsible for FEP screening. The resulting analysis supports disposition of fissile materials in the CCO containing up to 380 FGE 239 Pu and expands conditions acceptable for disposal of fissile material in CCOs. This evaluation builds on the methodology of Saylor and Scaglione and Brickner, using the most recently available geomechanical data for CCO spacing under salt creep compaction scenarios provided by Reedlunn and Bean. The broad range of fissile material configurations analyzed in this report are intended to account for configurations that may occur during the post-closure disposal time period, and it also includes waste configurations that are not physically possible to support analysis of conditions that influence neutron fluence.

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

Materials Data on Mg(SiB6)2 by Materials Project

MgB12Si2 crystallizes in the orthorhombic Pnma space group. The structure is zero-dimensional and consists of sixteen boron molecules and four Mg(B4Si)2 clusters. In each Mg(B4Si)2 cluster, Mg2+ is bonded in a distorted bent 150 degrees geometry to two Si4- atoms. There are one shorter (2.45 Å) and one longer (2.64 Å) Mg–Si bond lengths. There are six inequivalent B+0.50+ sites. In the first B+0.50+ site, B+0.50+ is bonded in a single-bond geometry to one Si4- atom. The B–Si bond length is 2.08 Å. In the second B+0.50+ site, B+0.50+ is bonded in a single-bond geometry to one Si4- atom. The B–Si bond length is 2.07 Å. In the third B+0.50+ site, B+0.50+ is bonded in a single-bond geometry to one Si4- atom. The B–Si bond length is 2.17 Å. In the fourth B+0.50+ site, B+0.50+ is bonded in a single-bond geometry to one Si4- atom. The B–Si bond length is 2.00 Å. In the fifth B+0.50+ site, B+0.50+ is bonded in a single-bond geometry to one Si4- atom. The B–Si bond length is 2.00 Å. In the sixth B+0.50+ site, B+0.50+ is bonded in a single-bond geometry to one Si4- atom. The B–Si bond length is 2.07 Å. There are two inequivalent Si4- sites. In the first Si4- site, Si4- is bonded in a 5-coordinate geometry to one Mg2+ and four B+0.50+ atoms. In the second Si4- site, Si4- is bonded in a 4-coordinate geometry to one Mg2+ and four B+0.50+ atoms.

36 MATERIALS SCIENCE↗