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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Development and Integration of a Stochastic Clad Damage Propagation Model into PRONGHORN-SC Subchannel Analysis Code

The failure of fuel pins in nuclear reactors is intrinsically stochastic. Typically, a combination of variation in manufacturing that affects the material characteristics and the fuel assembly dimensions, variation in operating conditions, such as local power, coolant flow rate, and irradiation induced changes in material properties lead to a large uncertainty in failure margin of the fuel pins. Failure, therefore, may occur in exceptional pins with adverse combinations of these variations. Upon a metal fuel pin (U-Pu-Zr/HT9) failure, depressurization of the fuel pin takes place by release of fission gas, liquid sodium bond, and potentially solid fuel particles or molten/eutectic fuel droplets through the hole in cladding. The effect of a fission gas jet on neighbor fuel pins and possible propagation of a clad damage during normal operation was studied experimentally in 1970s and it was found that the post-failure fission gas jet insulates the jet impingement area of the target fuel pin surface and could increase the target pin’s surface temperature by as much as 100 – 200 K during the failed pin depressurization. It was concluded that the effect should not lead to fuel pin failure propagation during normal operation. In accident scenarios of sodium and lead fast reactors such as Unprotected Loss-Of-Flow (ULOF) or Unprotected Transient Over Power (UTOP), the fuel pins can be subjected to higher clad temperatures and fuel pin pressures or fuel clad mechanical/chemical interaction where thermal creep margin becomes significantly lower compared to the normal operation conditions. Therefore, possible stochastic failure and the post-failure fission gas/fuel jet impingement could be critical in order to predict fuel pin failure propagation. Pin depressurization due to fission gas release may degrade the heat transfer by formation of a gas blanket on a neighboring pin surface, which is a local phenomenon, and by causing coolant flow deceleration and starvation, which could affect a surrounding region as well. Furthermore, the potential presence of solid fuel particles or molten fuel at the time of clad failure could boost post-failure jet induced degradation even further. The present study models the U-Pu-Zr/HT9 metal fuel pin failure and stochastic clad damage propagation by biased sampling based on a Cumulative Damage Fraction (CDF) type clad failure criterion and the normal distribution of fuel failure probability density as a function of logarithm of Cumulative Damage Fraction. In addition, the effect of post-failure fission gas jet on heat transfer degradation is modeled for the target pins. This model is called stochastic Clad Damage Propagation (CDAP). The CDAP model is now fully integrated into developmental version of PRONGHORN-SC subchannel analysis code, allowing for modeling local failures and its propagation potential. Section 2 describes the components of the CDAP models. Section 3 describes the model implementation to PRONGHORN-SC and input specifications. Section 4 describes the CDAP model validation coupled to PRONGHORN-SC.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2024

Efficient Reformulation and Optimization for SC-ACOPF with Line Switching

This project aims to develop efficient and robust computational methods for solving the security-constrained alternating current optimal power flow problem (SC-ACOPF). The SC-ACOPF problem is a central problem in operating the electric power grids in the United States. It determines the most economically efficient way to operate the generation and transmission system to meet daily electricity demand. The solution found by solving an SC-ACOPF problem must satisfy the physics of the alternating current (AC) power flows, various generator and network operational constraints, and must maintain secure operation under various contingency scenarios, where a generator, a transmission branch, or a transformer may unexpectedly trip offline.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1972

An EPR investigation of the dynamic Jahn-Teller effect in SrCl2:y(2 plus) and SrCl2:Sc(2 plus)

EPR spectra have been observed for SrCl2:Y(2+) and SrCl2:Sc(2+) at liquid helium temperatures. At 1.2 K the spectra were dominated by anisotropic hyperfine patterns whose lineshapes and angular dependences were explained using second order solutions of the effective Hamiltonian for an isolated 2Eg state split by large random internal strains. Pronounced asymmetries in some of the strin produced lineshapes for Srcl2:Sc(2+) are shown to result from second order terms in the solution of the effective Hamiltonian. Coexisting with the anisotropic hyperfine patterns are weak nearly isotropic hyperfine patterns with typical lineshapes. Variations in the apparent intensity of lines in these weak hyperfine patterns as functions of the applied magnetic field direction and temperature imply that these lines result from averaging by vibronic relaxation of a portion of the anisotropic pattern. The effective Hamiltonian parameters for SrCl2:La(2+), SrCl2:y(2+), and SrCl2:SC(2+) are analyzed in terms of crystal field theory modified to include a dynamic Jahn-Teller effect.

Herrington, J. R.↗
NASA NTRS1991

Theoretical study of the bonding of Sc, Y, and La singly charged and dipositive ions to C2H2, C2H4, and C3H6

The interaction of the Sc and Y singly-charged and dipositive ions with C2H2, C2H4, and C3H6 is studied using electronic structure calculations that include high levels of electron correlation. These results are compared with comparable calculations performed previously for La(+) and La(2+). For C2H2 and C2H4, all three metal ions insert into the C-C pi bond, making a three-membered ring. The optimal structures for the MC3H6(+) ions all involve rearrangement to make a four-membered ring. The strength of the metal-ligand bond for the singly charged ions follows the order La greater than Sc equal to about Y. In contrast, the bonds involving the dipositive ions are electrostatic, so that the binding energy increases as the size of the ion decreases, leading to the trend Sc greater than Y greater than La.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1994

Observations of enhanced sub-iron (Sc-Cr) to Iron abundance ratios in the low energy galactic cosmic rays in Spacelab-3 and their implications

The Anuradha cosmic ray experiment in Spacelab-3, flown in the orbit at 350 km with an inclination of 57 deg for about six days, was used to measure the low energy galactic cosmic ray (GCR) heavy ions using a specially designed CR-39 detector module incorporating the arrival time information of the particles. The abundances of sub-iron (Sc-Cr) and iron particles in the low energy interval of 30-300 MeV/N were determined from the measurements made in four different depths of the Cr-39 detector module of 150 layers. From these studies we obtained sub-iron (Sc-Cr) to iron abundance ratios of 0.8 to 1.2 in 30-300 MeV/N energy range. It is found that these ratios are enhanced by a factor of two as compared to interplanetary ratios of about 0.5. It is shown that the enhancement of the ratio inside the earth's magnetosphere is probably due to the degree of ionization of low energy Sc to Cr and Fe ions in the galactic cosmic rays and to the rigidity filtering effects of the geomagnetic field. Further studies are needed to understand fully the phenomena and their implications.

Biswas, S.↗
NASA NTRS1996

The Successive OH Binding Energies of Sc(OH)n+ for n=1-3

The geometries of Sc(OH)n+, for n = 1-3, have been optimized using density functional theory, in conjunction with the B3LYP hybrid functional. The zero-point energies are computed at the same level of theory. The successive OH bond energies have been computed at the CCSD(T) level for ScOH+ and Sc(OH)2+. The computed result for ScOD+ is in excellent agreement with the recent experiment of Armentrout and co-workers. There is a dramatic drop for the third OH, because Sc+ has only two valence electrons and therefore the bonding changes when the third OH is added. The difference between the B3LYP and CCSD(T) OH binding energies for the first two OH groups is discussed.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1999

A Further Study of the Products of Sc and Dioxygen Reactions

The products of the reaction of Sc and dioxygen have been reinvestigated. By adding the electron-trapping molecule CC14, additional information about the IR spectra has been obtained, as well as the observation of new bands. New ab initio calculations are also performed on possible products of the Sc plus O2 reaction. The previously observed band at 722.5 per cm is assigned as the b2 mode of ScO2(-). Bands arising from ScO(+), Sc(O2)(+), and(O2)ScO are also assigned. We are still unable to assign any bands to OScO. The problems associated with the computational study of ScO2 are discussed.

Bauschlicher, Charles W., Jr.↗
NASA NTRSDate not supplied

Design Concepts to Meet EASA SC-VTOL-01 Single Failure Criteria

The objective of the current work is to discuss European Union Aviation Safety Agency (EASA) SC-VTOL-01 single failure criteria, VTOL.2250(c). Prior studies have developed concept distributed propulsion and flight control (DPFC) system architectures and found they comply with EASA SC-VTOL-01 probabilistic failure criteria, VTOL.2510(a). Prior work developed two all-electric DPFC systems utilized in a quadrotor concept aircraft developed by the National Aeronautics and Space Administration (NASA); one uses interconnecting shafts and gearboxes to interconnect redundant motors with each rotor system and the other uses gearboxes to connect redundant motors locally, near each rotor. Common between the two electric DPFC systems were rotor shafts, epicyclic systems, and motors. The current work explores Category I failures in drive systems, relevant research to support fail-safe design practices for gear systems, research and adjacent industry trends in motor fail-safety and reliability, and proposed design concepts to comply with VTOL.2250(c). Continued research in fail-safe design concepts and design guidance will benefit eVTOL and conventional rotorcraft, alike. Continued research in these areas will benefit eVTOL certification against SC-VTOL-01, and could optimistically translate to more widespread adoption of similar fail-safe design concepts into new rotorcraft designs certified against CS-29.

Rotorcraft↗
DOE OSTI2026

$K^{*}(892)^0$ production and the time between freeze-outs in $^{40}$Ar+$^{45}$Sc collisions by NA61/SHINE at the CERN SPS

The analysis of the production of strange $K^{*}(892)^0$ resonances allows us to better understand the temporal evolution of high-energy nucleus--nucleus collisions. In particular, the ratio of $K^{*}(892)^0$ to charged kaon yields is used to determine the time interval between chemical and kinetic freeze-outs. In this paper, the first measurements of $K^{*}(892)^0$ production in central $^{40}$Ar+$^{45}$Sc collisions at the CERN Super Proton Synchrotron are reported. They were performed by NA61/SHINE at collision center-of-mass energies per nucleon pair $\sqrt{s_\mathrm{NN}}$ = 8.8, 11.9, 16.8 GeV. The obtained $\langle K^{*}(892)^0 \rangle/\langle K^{+} \rangle $ and $\langle K^{*}(892)^0 \rangle/\langle K^{-} \rangle$ mean multiplicity ratios are compared with corresponding results in $p$+$p$ collisions, allowing for an estimate of the time interval between chemical and thermal freeze-outs in the $^{40}$Ar+$^{45}$Sc system. These are the first such results reported for $^{40}$Ar+$^{45}$Sc collisions.

Adrich, P. [NCBJ, Warsaw] (ORCID:0000000270195451)↗
DOE OSTI2020

Materials Data on Sc(SiNi)2 by Materials Project

Sc(NiSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Sc3+ is bonded in a distorted body-centered cubic geometry to eight equivalent Si4- atoms. All Sc–Si bond lengths are 2.93 Å. Ni+2.50+ is bonded to four equivalent Si4- atoms to form a mixture of edge and corner-sharing NiSi4 tetrahedra. All Ni–Si bond lengths are 2.27 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Sc3+, four equivalent Ni+2.50+, and one Si4- atom. The Si–Si bond length is 2.32 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sc(CoSi)2 by Materials Project

Sc(CoSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Sc3+ is bonded in a distorted body-centered cubic geometry to eight equivalent Si4- atoms. All Sc–Si bond lengths are 2.92 Å. Co+2.50+ is bonded to four equivalent Si4- atoms to form a mixture of edge and corner-sharing CoSi4 tetrahedra. All Co–Si bond lengths are 2.24 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Sc3+, four equivalent Co+2.50+, and one Si4- atom. The Si–Si bond length is 2.38 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sc(FeSi)2 by Materials Project

Sc(FeSi)2 crystallizes in the orthorhombic Pbcm space group. The structure is three-dimensional. Sc3+ is bonded in a 6-coordinate geometry to eight Si4- atoms. There are a spread of Sc–Si bond distances ranging from 2.69–3.11 Å. There are two inequivalent Fe+2.50+ sites. In the first Fe+2.50+ site, Fe+2.50+ is bonded in a 5-coordinate geometry to five Si4- atoms. There are a spread of Fe–Si bond distances ranging from 2.26–2.43 Å. In the second Fe+2.50+ site, Fe+2.50+ is bonded to five Si4- atoms to form a mixture of distorted corner and edge-sharing FeSi5 trigonal bipyramids. There are a spread of Fe–Si bond distances ranging from 2.40–2.48 Å. There are two inequivalent Si4- sites. In the first Si4- site, Si4- is bonded in a 9-coordinate geometry to four equivalent Sc3+ and five Fe+2.50+ atoms. In the second Si4- site, Si4- is bonded in a 11-coordinate geometry to four equivalent Sc3+, five Fe+2.50+, and two equivalent Si4- atoms. Both Si–Si bond lengths are 2.49 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sc(PO3)3 by Materials Project

Sc(PO3)3 crystallizes in the cubic I-43d space group. The structure is three-dimensional. Sc3+ is bonded to six O2- atoms to form ScO6 octahedra that share corners with six equivalent PO4 tetrahedra. There are three shorter (2.09 Å) and three longer (2.10 Å) Sc–O bond lengths. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent ScO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 14–32°. There are a spread of P–O bond distances ranging from 1.49–1.62 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to one Sc3+ and one P5+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent P5+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Sc3+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sc(VN)9 by Materials Project

Sc(VN)9 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Sc3+ is bonded to six N3- atoms to form ScN6 octahedra that share corners with six VN5 square pyramids, edges with six VN6 octahedra, and edges with six VN5 square pyramids. There are four shorter (2.14 Å) and two longer (2.15 Å) Sc–N bond lengths. There are five inequivalent V+2.67+ sites. In the first V+2.67+ site, V+2.67+ is bonded to five N3- atoms to form VN5 square pyramids that share corners with two equivalent ScN6 octahedra, corners with seven VN5 square pyramids, an edgeedge with one ScN6 octahedra, edges with five VN6 octahedra, and edges with two VN5 square pyramids. The corner-sharing octahedra tilt angles range from 5–6°. There are a spread of V–N bond distances ranging from 2.00–2.13 Å. In the second V+2.67+ site, V+2.67+ is bonded to six N3- atoms to form VN6 octahedra that share corners with three VN6 octahedra, corners with three equivalent VN5 square pyramids, edges with two equivalent ScN6 octahedra, edges with two VN6 octahedra, and edges with eight VN5 square pyramids. The corner-sharing octahedra tilt angles range from 0–7°. There are a spread of V–N bond distances ranging from 2.01–2.17 Å. In the third V+2.67+ site, V+2.67+ is bonded to five N3- atoms to form VN5 square pyramids that share a cornercorner with one ScN6 octahedra, corners with eight VN5 square pyramids, an edgeedge with one ScN6 octahedra, edges with four VN6 octahedra, and edges with three VN5 square pyramids. The corner-sharing octahedral tilt angles are 5°. There are a spread of V–N bond distances ranging from 1.96–2.16 Å. In the fourth V+2.67+ site, V+2.67+ is bonded to five N3- atoms to form VN5 square pyramids that share corners with four VN6 octahedra, corners with five VN5 square pyramids, an edgeedge with one ScN6 octahedra, edges with three VN6 octahedra, and edges with four VN5 square pyramids. The corner-sharing octahedra tilt angles range from 1–7°. There are a spread of V–N bond distances ranging from 2.02–2.19 Å. In the fifth V+2.67+ site, V+2.67+ is bonded to six N3- atoms to form VN6 octahedra that share corners with four equivalent VN6 octahedra, corners with two equivalent VN5 square pyramids, edges with two equivalent ScN6 octahedra, edges with two equivalent VN6 octahedra, and edges with eight VN5 square pyramids. The corner-sharing octahedra tilt angles range from 4–7°. There are a spread of V–N bond distances ranging from 2.04–2.12 Å. There are five inequivalent N3- sites. In the first N3- site, N3- is bonded to one Sc3+ and five V+2.67+ atoms to form a mixture of corner and edge-sharing NScV5 octahedra. The corner-sharing octahedra tilt angles range from 0–6°. In the second N3- site, N3- is bonded to one Sc3+ and five V+2.67+ atoms to form a mixture of corner and edge-sharing NScV5 octahedra. The corner-sharing octahedra tilt angles range from 0–8°. In the third N3- site, N3- is bonded to six V+2.67+ atoms to form a mixture of corner and edge-sharing NV6 octahedra. The corner-sharing octahedra tilt angles range from 4–8°. In the fourth N3- site, N3- is bonded to one Sc3+ and five V+2.67+ atoms to form a mixture of corner and edge-sharing NScV5 octahedra. The corner-sharing octahedra tilt angles range from 0–6°. In the fifth N3- site, N3- is bonded to six V+2.67+ atoms to form a mixture of corner and edge-sharing NV6 octahedra. The corner-sharing octahedra tilt angles range from 0–8°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sc(CuSi)2 by Materials Project

Sc(CuSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Sc3+ is bonded in a distorted body-centered cubic geometry to eight equivalent Si4- atoms. All Sc–Si bond lengths are 2.93 Å. Cu+2.50+ is bonded to four equivalent Si4- atoms to form a mixture of corner and edge-sharing CuSi4 tetrahedra. All Cu–Si bond lengths are 2.36 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Sc3+, four equivalent Cu+2.50+, and one Si4- atom. The Si–Si bond length is 2.28 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sc(CuO2)2 by Materials Project

Sc(CuO2)2 crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. Sc3+ is bonded in a tetrahedral geometry to four equivalent O2- atoms. All Sc–O bond lengths are 2.02 Å. Cu+2.50+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.90 Å. O2- is bonded in a distorted trigonal planar geometry to one Sc3+ and two equivalent Cu+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sc(CuO2)2 by Materials Project

Sc(CuO2)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Sc3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Sc–O bond distances ranging from 2.23–2.31 Å. There are two inequivalent Cu+2.50+ sites. In the first Cu+2.50+ site, Cu+2.50+ is bonded in a square co-planar geometry to four O2- atoms. There is two shorter (1.89 Å) and two longer (1.92 Å) Cu–O bond length. In the second Cu+2.50+ site, Cu+2.50+ is bonded in a square co-planar geometry to four O2- atoms. There is two shorter (1.89 Å) and two longer (1.91 Å) Cu–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Sc3+ and two Cu+2.50+ atoms to form a mixture of distorted edge and corner-sharing OSc2Cu2 tetrahedra. In the second O2- site, O2- is bonded to two equivalent Sc3+ and two Cu+2.50+ atoms to form a mixture of distorted edge and corner-sharing OSc2Cu2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sc(VSi)5 by Materials Project

Sc(VSi)5 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Sc2+ is bonded to seven Si+2.40- atoms to form ScSi7 pentagonal bipyramids that share corners with two equivalent ScSi7 pentagonal bipyramids, corners with eight VSi7 pentagonal bipyramids, edges with three equivalent ScSi7 pentagonal bipyramids, and faces with six VSi7 pentagonal bipyramids. There are a spread of Sc–Si bond distances ranging from 2.64–2.79 Å. There are four inequivalent V2+ sites. In the first V2+ site, V2+ is bonded in a 8-coordinate geometry to two equivalent V2+ and six Si+2.40- atoms. There are one shorter (2.45 Å) and one longer (2.48 Å) V–V bond lengths. There are a spread of V–Si bond distances ranging from 2.45–2.62 Å. In the second V2+ site, V2+ is bonded to seven Si+2.40- atoms to form distorted VSi7 pentagonal bipyramids that share corners with three equivalent ScSi7 pentagonal bipyramids, corners with five VSi7 pentagonal bipyramids, edges with four VSi7 pentagonal bipyramids, faces with two equivalent ScSi7 pentagonal bipyramids, and faces with four VSi7 pentagonal bipyramids. There are a spread of V–Si bond distances ranging from 2.38–2.75 Å. In the third V2+ site, V2+ is bonded to seven Si+2.40- atoms to form distorted VSi7 pentagonal bipyramids that share a cornercorner with one ScSi7 pentagonal bipyramid, corners with seven VSi7 pentagonal bipyramids, edges with four VSi7 pentagonal bipyramids, faces with two equivalent ScSi7 pentagonal bipyramids, and faces with four VSi7 pentagonal bipyramids. There are a spread of V–Si bond distances ranging from 2.41–2.74 Å. In the fourth V2+ site, V2+ is bonded to seven Si+2.40- atoms to form VSi7 pentagonal bipyramids that share corners with four equivalent ScSi7 pentagonal bipyramids, corners with six VSi7 pentagonal bipyramids, edges with three equivalent VSi7 pentagonal bipyramids, faces with two equivalent ScSi7 pentagonal bipyramids, and faces with four VSi7 pentagonal bipyramids. There are a spread of V–Si bond distances ranging from 2.57–2.82 Å. There are five inequivalent Si+2.40- sites. In the first Si+2.40- site, Si+2.40- is bonded in a 10-coordinate geometry to seven V2+ and three Si+2.40- atoms. There are one shorter (2.49 Å) and two longer (2.79 Å) Si–Si bond lengths. In the second Si+2.40- site, Si+2.40- is bonded in a 9-coordinate geometry to three equivalent Sc2+ and six V2+ atoms. In the third Si+2.40- site, Si+2.40- is bonded in a 11-coordinate geometry to one Sc2+ and eight V2+ atoms. In the fourth Si+2.40- site, Si+2.40- is bonded in a 10-coordinate geometry to two equivalent Sc2+, six V2+, and two equivalent Si+2.40- atoms. There are one shorter (2.43 Å) and one longer (2.50 Å) Si–Si bond lengths. In the fifth Si+2.40- site, Si+2.40- is bonded in a 10-coordinate geometry to one Sc2+, six V2+, and three Si+2.40- atoms. The Si–Si bond length is 2.40 Å.

36 MATERIALS SCIENCE↗