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33 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ca(SiPd)2 by Materials Project

Ca(PdSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca2+ is bonded to eight equivalent Si4- atoms to form CaSi8 hexagonal bipyramids that share corners with sixteen equivalent PdSi4 tetrahedra, edges with four equivalent CaSi8 hexagonal bipyramids, edges with eight equivalent PdSi4 tetrahedra, and faces with four equivalent CaSi8 hexagonal bipyramids. All Ca–Si bond lengths are 3.24 Å. Pd3+ is bonded to four equivalent Si4- atoms to form PdSi4 tetrahedra that share corners with eight equivalent CaSi8 hexagonal bipyramids, corners with four equivalent PdSi4 tetrahedra, edges with four equivalent CaSi8 hexagonal bipyramids, and edges with four equivalent PdSi4 tetrahedra. All Pd–Si bond lengths are 2.47 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Ca2+, four equivalent Pd3+, and one Si4- atom. The Si–Si bond length is 2.39 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(SiPd)2 by Materials Project

Sr(PdSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Sr2+ is bonded to eight equivalent Si4- atoms to form SrSi8 hexagonal bipyramids that share corners with sixteen equivalent PdSi4 tetrahedra, edges with four equivalent SrSi8 hexagonal bipyramids, edges with eight equivalent PdSi4 tetrahedra, and faces with four equivalent SrSi8 hexagonal bipyramids. All Sr–Si bond lengths are 3.31 Å. Pd3+ is bonded to four equivalent Si4- atoms to form PdSi4 tetrahedra that share corners with eight equivalent SrSi8 hexagonal bipyramids, corners with four equivalent PdSi4 tetrahedra, edges with four equivalent SrSi8 hexagonal bipyramids, and edges with four equivalent PdSi4 tetrahedra. All Pd–Si bond lengths are 2.50 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Sr2+, four equivalent Pd3+, and one Si4- atom. The Si–Si bond length is 2.49 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La3(SiPd)4 by Materials Project

La3Pd4Si4 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are two inequivalent La+2.67+ sites. In the first La+2.67+ site, La+2.67+ is bonded in a 6-coordinate geometry to six Si4- atoms. There are two shorter (3.24 Å) and four longer (3.28 Å) La–Si bond lengths. In the second La+2.67+ site, La+2.67+ is bonded to eight equivalent Si4- atoms to form a mixture of edge and face-sharing LaSi8 hexagonal bipyramids. All La–Si bond lengths are 3.25 Å. There are two inequivalent Pd2+ sites. In the first Pd2+ site, Pd2+ is bonded to four equivalent Si4- atoms to form a mixture of edge and corner-sharing PdSi4 tetrahedra. There are two shorter (2.47 Å) and two longer (2.53 Å) Pd–Si bond lengths. In the second Pd2+ site, Pd2+ is bonded in a trigonal planar geometry to three Si4- atoms. All Pd–Si bond lengths are 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 La+2.67+ and five Pd2+ atoms. In the second Si4- site, Si4- is bonded in a 2-coordinate geometry to six La+2.67+, two equivalent Pd2+, and one Si4- atom. The Si–Si bond length is 2.39 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm(SiPd)2 by Materials Project

Tm(PdSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Tm is bonded in a 8-coordinate geometry to eight equivalent Pd and eight equivalent Si atoms. All Tm–Pd bond lengths are 3.24 Å. All Tm–Si bond lengths are 3.14 Å. Pd is bonded to four equivalent Tm and four equivalent Si atoms to form a mixture of distorted corner, edge, and face-sharing PdTm4Si4 tetrahedra. All Pd–Si bond lengths are 2.46 Å. Si is bonded in a 9-coordinate geometry to four equivalent Tm, four equivalent Pd, and one Si atom. The Si–Si bond length is 2.30 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(SiPd)2 by Materials Project

Np(PdSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np4+ is bonded to eight equivalent Si4- atoms to form NpSi8 hexagonal bipyramids that share corners with sixteen equivalent PdSi4 tetrahedra, edges with four equivalent NpSi8 hexagonal bipyramids, edges with eight equivalent PdSi4 tetrahedra, and faces with four equivalent NpSi8 hexagonal bipyramids. All Np–Si bond lengths are 3.11 Å. Pd2+ is bonded to four equivalent Si4- atoms to form PdSi4 tetrahedra that share corners with eight equivalent NpSi8 hexagonal bipyramids, corners with four equivalent PdSi4 tetrahedra, edges with four equivalent NpSi8 hexagonal bipyramids, and edges with four equivalent PdSi4 tetrahedra. All Pd–Si bond lengths are 2.49 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Np4+, four equivalent Pd2+, and one Si4- atom. The Si–Si bond length is 2.32 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LaCe(SiPd)4 by Materials Project

CeLa(PdSi)4 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Ce3+ is bonded to eight equivalent Si4- atoms to form CeSi8 hexagonal bipyramids that share corners with sixteen equivalent PdSi4 tetrahedra, edges with four equivalent CeSi8 hexagonal bipyramids, edges with eight equivalent PdSi4 tetrahedra, and faces with four equivalent CeSi8 hexagonal bipyramids. All Ce–Si bond lengths are 3.22 Å. La3+ is bonded to eight equivalent Si4- atoms to form LaSi8 hexagonal bipyramids that share corners with sixteen equivalent PdSi4 tetrahedra, edges with four equivalent LaSi8 hexagonal bipyramids, edges with eight equivalent PdSi4 tetrahedra, and faces with four equivalent LaSi8 hexagonal bipyramids. All La–Si bond lengths are 3.23 Å. Pd+2.50+ is bonded to four Si4- atoms to form PdSi4 tetrahedra that share corners with four equivalent CeSi8 hexagonal bipyramids, corners with four equivalent LaSi8 hexagonal bipyramids, corners with four equivalent PdSi4 tetrahedra, edges with two equivalent CeSi8 hexagonal bipyramids, edges with two equivalent LaSi8 hexagonal bipyramids, and edges with four equivalent PdSi4 tetrahedra. There are two shorter (2.49 Å) and two longer (2.50 Å) Pd–Si bond lengths. There are two inequivalent Si4- sites. In the first Si4- site, Si4- is bonded in a 9-coordinate geometry to four equivalent Ce3+, four equivalent Pd+2.50+, and one Si4- atom. The Si–Si bond length is 2.34 Å. In the second Si4- site, Si4- is bonded in a 9-coordinate geometry to four equivalent La3+, four equivalent Pd+2.50+, and one Si4- atom. The Si–Si bond length is 2.39 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm3(SiPd)2 by Materials Project

Sm3Pd2Si2 crystallizes in the orthorhombic Pbcm space group. The structure is three-dimensional. there are two inequivalent Sm sites. In the first Sm site, Sm is bonded in a 9-coordinate geometry to four equivalent Pd and five Si atoms. There are two shorter (3.07 Å) and two longer (3.13 Å) Sm–Pd bond lengths. There are a spread of Sm–Si bond distances ranging from 3.07–3.29 Å. In the second Sm site, Sm is bonded in a 7-coordinate geometry to four equivalent Pd and four Si atoms. There are a spread of Sm–Pd bond distances ranging from 3.00–3.19 Å. There are a spread of Sm–Si bond distances ranging from 3.02–3.40 Å. Pd is bonded in a 10-coordinate geometry to six Sm, one Pd, and three Si atoms. The Pd–Pd bond length is 2.84 Å. There are one shorter (2.52 Å) and two longer (2.65 Å) Pd–Si bond lengths. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to seven Sm and two equivalent Pd atoms. In the second Si site, Si is bonded in a 12-coordinate geometry to six Sm and four equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SiPd by Materials Project

PdSi crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Pd4+ is bonded in a distorted pentagonal planar geometry to five equivalent Si4- atoms. There are four shorter (2.46 Å) and one longer (2.47 Å) Pd–Si bond lengths. Si4- is bonded in a 5-coordinate geometry to five equivalent Pd4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(SiPd)6 by Materials Project

Sr(PdSi)6 crystallizes in the orthorhombic Ibam space group. The structure is three-dimensional and consists of four strontium molecules and one PdSi framework. In the PdSi framework, there are two inequivalent Pd+2.33+ sites. In the first Pd+2.33+ site, Pd+2.33+ is bonded in a 5-coordinate geometry to five Si+2.67- atoms. There are a spread of Pd–Si bond distances ranging from 2.45–2.62 Å. In the second Pd+2.33+ site, Pd+2.33+ is bonded in a 7-coordinate geometry to seven Si+2.67- atoms. There are a spread of Pd–Si bond distances ranging from 2.44–2.98 Å. There are two inequivalent Si+2.67- sites. In the first Si+2.67- site, Si+2.67- is bonded in a 5-coordinate geometry to six Pd+2.33+ atoms. In the second Si+2.67- site, Si+2.67- is bonded in a 4-coordinate geometry to five Pd+2.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce3(SiPd)4 by Materials Project

Ce3Pd4Si4 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are two inequivalent Ce sites. In the first Ce site, Ce is bonded to four equivalent Pd and eight equivalent Si atoms to form a mixture of face and edge-sharing CeSi8Pd4 cuboctahedra. All Ce–Pd bond lengths are 3.16 Å. All Ce–Si bond lengths are 3.18 Å. In the second Ce site, Ce is bonded in a 12-coordinate geometry to eight Pd and six Si atoms. There are a spread of Ce–Pd bond distances ranging from 3.18–3.31 Å. There are two shorter (3.17 Å) and four longer (3.19 Å) Ce–Si bond lengths. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded in a 3-coordinate geometry to six Ce and three Si atoms. There are two shorter (2.43 Å) and one longer (2.44 Å) Pd–Si bond lengths. In the second Pd site, Pd is bonded to four equivalent Ce and four equivalent Si atoms to form a mixture of distorted face and edge-sharing PdCe4Si4 tetrahedra. There are two shorter (2.43 Å) and two longer (2.50 Å) Pd–Si bond lengths. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to four equivalent Ce and five Pd atoms. In the second Si site, Si is bonded in a 2-coordinate geometry to six Ce, two equivalent Pd, and one Si atom. The Si–Si bond length is 2.39 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr(SiPd)3 by Materials Project

Zr(PdSi)3 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Zr4+ is bonded to eight equivalent Si4- atoms to form distorted ZrSi8 hexagonal bipyramids that share corners with four equivalent PdSi4 tetrahedra, edges with four equivalent ZrSi8 hexagonal bipyramids, edges with two equivalent PdSi4 tetrahedra, and faces with four equivalent ZrSi8 hexagonal bipyramids. There are four shorter (2.81 Å) and four longer (2.95 Å) Zr–Si bond lengths. There are two inequivalent Pd+2.67+ sites. In the first Pd+2.67+ site, Pd+2.67+ is bonded to four Si4- atoms to form PdSi4 tetrahedra that share corners with four equivalent ZrSi8 hexagonal bipyramids, corners with two equivalent PdSi4 tetrahedra, and edges with two equivalent ZrSi8 hexagonal bipyramids. There are two shorter (2.43 Å) and two longer (2.50 Å) Pd–Si bond lengths. In the second Pd+2.67+ site, Pd+2.67+ is bonded in a 5-coordinate geometry to five Si4- atoms. There are a spread of Pd–Si bond distances ranging from 2.51–2.58 Å. There are two inequivalent Si4- sites. In the first Si4- site, Si4- is bonded in a 8-coordinate geometry to four equivalent Zr4+, three Pd+2.67+, and one Si4- atom. The Si–Si bond length is 2.36 Å. In the second Si4- site, Si4- is bonded in a 8-coordinate geometry to eight Pd+2.67+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K(SiPd)4 by Materials Project

K(PdSi)4 crystallizes in the tetragonal I4 space group. The structure is three-dimensional. K is bonded in a 4-coordinate geometry to eight equivalent Pd and four equivalent Si atoms. There are four shorter (3.24 Å) and four longer (3.47 Å) K–Pd bond lengths. All K–Si bond lengths are 3.51 Å. Pd is bonded in a 9-coordinate geometry to two equivalent K and five equivalent Si atoms. There are a spread of Pd–Si bond distances ranging from 2.44–2.54 Å. Si is bonded in a 5-coordinate geometry to one K and five equivalent Pd atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1997

The Algorithm for MODIS Wavelength On-Orbit Calibration using the SRCA

The Spectro-Radiometric Calibration Assembly (SRCA) provides on-orbit spectral calibration of the MODerate resolution Imaging Spectroradiometer (MODIS) reflected solar bands and this paper describes how it is accomplished. The SRCA has two adjacent exit slits: 1) Main slit and 2) Calibration slit. The output from the main slit is measured by a reference silicon photo-diode (SIPD) and then passes through the MODIS. The output from the calibration slit passes through a piece of didymium transmission glass and then it is measured by a calibration SIPD. The centroids of the sharp spectral peaks of a didyrnium glass are utilized as wavelength standards. After normalization using the reference SIPD signal to eliminate the effects of the illuminating source spectra, the calibration SIPD establishes the relationship between the peaks of the didymium spectra and the grating angle; this is accomplished through the grating equation. In the grating equation the monochromator parameters, beta (half angle between the incident and diffractive beams) and theta(sub ff) (offset angle of the grating motor) are determined by matching, in a least square sense, the known centroid wavelengths of the didymium peaks and the calculated centroid grating angles from the calibration SIPD signals for the peaks. A displacement between the calibration SIPD and the reference SIPD complicates the signal processing. The response of the MODIS bands to the SRCA output is also normalized by the reference SIPD signal to eliminate the effect of the source spectrum. That response differs from what is measured by MODIS using the Spectral Measurements Assembly (SpMA), a laboratory double-monochromator, due to the wider slit width of the SRCA. The SRCA slit function, calculated using measurements by the SPMA and the SRCA at the same MODIS temperature, will be used to recover the MODIS spectral response using the SRCA data measured on-orbit.

Montgomery, Harry↗
NASA NTRS1998

The Algorithm for MODIS Wavelength On-Orbit Calibration Using the SRCA

The Spectro-Radiometric Calibration Assembly (SRCA) provides on-orbit spectral calibration of the MODerate resolution Imaging Spectroradiometer (MODIS) reflected solar bands and this paper describes how it is accomplished. The SRCA has two adjacent exit slits: 1) Main slit and 2) Calibration slit. The output from the main slit is measured by a reference silicon photo-diode (SIPD) and then passes through the MODIS. The output from the calibration slit passes through a piece of didymium transmission glass and then it is measured by a calibration SIPD. The centroids of the sharp spectral peaks of a didymium glass are utilized as wavelength standards. After normalization using the reference SIPD signal to eliminate the effects of the illuminating source spectra, the calibration SIPD establishes the relationship between the peaks of the didymium spectra and the grating angle; this is accomplished through the grating equation. In the grating equation the monochromator parameters, Beta (half angle between the incident and diffractive beams) and Theta(sub off) (offset angle of the grating motor) are determined by matching, in a least square sense, the known centroid wavelengths of the didymium peaks and the calculated centroid grating angles from the calibration SIPD signals for the peaks. A displacement between the calibration SIPD and the reference SIPD complicates the signal processing.

Montgomery, Harry↗
DOE OSTI2020

Large Volume Airborne Contamination Monitoring To Support Nuclear Processes' Deactivation and Decommissioning

Current D and D operations at Hanford have demonstrated a flaw in the current state of the art capability of defining airborne contamination boundaries - Airborne particulate emissions of Pu-239 from CM2H operations on the Hanford Pu Finishing Plant were detected well beyond areas controlled for airborne Pu, putting numerous workers at risk for radiological assimilations - Current air samplers and CAM systems were surveying insufficient volumes of air to accurately predict where respiratory protection was required - Hanford is located in a high radon environment, making air monitoring for alpha emitting actinides challenging in high alpha radon induced backgrounds. - Inexpensive HEPA based home and industrial air purifiers filter significantly higher volumes of air than commercially available continuous-air monitoring (CAM) systems. - Inexpensive models capable of filtered air volumes exceeding 1000 times that of a CAM. - Detector system can be built to detect x-rays generated from actinide decay. - Branching ratios of x-rays are 4 orders of magnitude more intense from Plutonium decay than its gamma emissions. - Detector system can be a low resolution systems, as x-ray region of interest is not terribly congested. - Detection systems evaluated will be designed based on slabs of NaI or pixelated NaI or CsI panels. - Simple graphical user interface software will be developed to operate the detection system. - Concept is to deploy some of these air-purifying systems in nonradiological areas around SRNL to confirm radon can be rejected with confidence. - Generate some filters contaminated with plutonium via electroplated Pu or lab generated simulated particles. - then deploy units in known airborne radiological environments to establish systems ability to accurately measure actinide based hot particles Lab analyses will follow up the system analyses to ensure hot particles were correctly identified. Analysis by Scintillation: - Application of scintillation media to the surface of the filters is being explored. - Evaluating slabs of ZnS(Ag), application of powdered ZnS(Cu) and spray on Perkin Elmer Enhance. - Scintillation events would then be digitized with a digital camera and quantified. - Comparing against sensitivity of a PMT or SiPD readout. - Currently evaluating a Thorlabs 8 Megapixel Monochrome Scientific CCD Camera, hermetically sealed cooled package with a wide angle lens. - Wide angle lens allows complete view of HEPA filter from 7 inches away. - Images taken of glow in the dark paint, as well as plutonium-induced fluorescence. - Plutonium was flamed mounted on a 1 inch diameter stainless steel planchet, covered with a layer of mylar and a section of scintillating ZnS obtained from Eljon. - Currently working on reducing signal-to-noise levels to boost sensitivity. - Dark box to hold contaminated or electroplated source covered filters under fabrication. Analysis by x-ray Spectroscopy: - Branching ratios for x-ray emissions from Plutonium isotopes are orders of magnitude more intense than gamma-ray emissions. - The nuclear databases are incomplete on the branching ratios of some of the isotopes. - Evaluating some custom built SrI2 x-ray spectrometers vs a conventional windowed NaI detector. - SrI2 detectors are carbon-composite-windowed 51 mm x 51 mm. - MCNP calculations to establish self absorbance of filter media on 17 keV x-ray. Radon Rejection: - Activated charcoal pre-filter acts as a Radon trap. - Adding a time lapse feature to camera to aid in radon rejection. SRS Plutonium Fuel Form D and D Operations: Currently deploying air sampler to D and D operation of Pu-238 facility at SRS to generate some field samples to analyze.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗