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10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Understanding the high-temperature behavior and corrosion resistance of Cr-Nb coated cladding for BWRs

While Cr-coated Accident Tolerant Fuel has proven successful in Pressurized Water Reactors, its dissolution in high dissolved oxygen Boiling Water Reactor environments represents a major technological barrier. Here, this study presents a comprehensive evaluation of novel Cr-Nb alloys as a coating breakthrough solution for Accident Tolerant Fuel cladding in Boiling Water Reactors. We systematically investigated Physical Vapor Deposited Cr-Nb coatings with 13% and 24 at% Nb content on commercial Zr-based cladding through rigorous testing under both normal and accident conditions. Our results demonstrate Cr-Nb coatings remained completely intact during extended Boiling Water Reactor autoclave testing, while pure Cr coatings failed catastrophically due to oxide dissolution. Under Loss-of-Coolant Accident conditions at 1100°C, Cr-Nb coatings maintained protective capability for 45 min. At 800°C, the alloy coatings matched pure Cr's excellent corrosion resistance. Despite microstructural changes during prolonged high-temperature exposure, no coating delamination occurred, ensuring continued protection of the underlying Zr substrate. These findings establish Cr-Nb coatings as a viable Accident Tolerant Fuel solution for Boiling Water Reactors.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS2004

Effects of Initial Powder Size on the Mechanical Properties and Microstructure of As-Extruded GRCop-84

GRCop-84 was developed to meet the mechanical and thermal property requirements for advanced regeneratively cooled rocket engine main combustion chamber liners. It is a ternary Cu- Cr-Nb alloy having approximately 8 at% Cr and 4 at% Nb. The chromium and niobium constituents combine to form 14 vol% Cr2Nb, the strengthening phase. The alloy is made by producing GRCop-84 powder through gas atomization and consolidating the powder using extrusion, hot isostatic pressing (HIP) or vacuum plasma spraying (VPS). GRCop-84 has been selected by Rocketdyne, Ratt & Wlutney and Aerojet for use in their next generation of rocket engines. GRCop-84 demonstrates favorable mechanical and thermal properties at elevated temperatures. Compared to NARloy-Z, the currently used inaterial in the Space Shuttle, GRCop-84 has approximately twice the yield strength, 10-1000 times the creep life, and 1.5-2.5 times the low cycle fatigue life. The thermal expansion of GRCop-84 is 7515% less than NARloy-Z which minimizes thermally induced stresses. The thermal conductivity of the two alloys is comparable at low temperature but NARloy-Z has a 20-50 W/mK thermal conductivity advantage at typical rocket engine hot wall temperatures. GRCop-84 is also much more microstructurally stable than NARloy-Z which translates into better long term stability of mechanical properties. Previous research into metal alloys fabricated by means of powder metallurgy (PM), has demonstrated that initial powder size can affect the microstructural development and mechanical properties of such materials. Grain size, strength, ductility, size of second phases, etc., have all been shown to vary with starting powder size in PM-alloys. This work focuses on characterizing the effect of varying starting powder size on the microstructural evolution and mechanical properties of as- extruded GRCop-84. Tensile tests and constant load creep tests were performed on extrusions of four powder meshes: +140 mesh (great3er than l05 micron powder size), -140 mesh (less than or equal to 105 microns), -140 plus or minus 270 (53 - 105 microns), and - 270 mesh (less than or equal to 53 microns). Samples were tested in tension at room temperature and at 500 C (932 F). Creep tests were performed under vacuum at 500 C using a stress of 111 MPa (16.1 ksi). The fracture surfaces of selected samples from both tests were studied using a Scanning Electron Microscope (SEM). The as-extruded materials were also studied, using both optical microscopy and SEM analysis, to characterize changes within the microstructure.

Okoro, Chika L.↗
DOE OSTI2020

Materials Data on NbCr2 by Materials Project

Cr2Nb is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Nb is bonded in a 12-coordinate geometry to four equivalent Nb and twelve equivalent Cr atoms. All Nb–Nb bond lengths are 3.01 Å. All Nb–Cr bond lengths are 2.88 Å. Cr is bonded to six equivalent Nb and six equivalent Cr atoms to form a mixture of edge, face, and corner-sharing CrNb6Cr6 cuboctahedra. All Cr–Cr bond lengths are 2.46 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbCr3 by Materials Project

CrCr2Nb is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Nb is bonded in a distorted body-centered cubic geometry to fourteen Cr atoms. There are eight shorter (2.58 Å) and six longer (2.98 Å) Nb–Cr bond lengths. There are two inequivalent Cr sites. In the first Cr site, Cr is bonded in a distorted body-centered cubic geometry to four equivalent Nb and four equivalent Cr atoms. All Cr–Cr bond lengths are 2.58 Å. In the second Cr site, Cr is bonded in a distorted body-centered cubic geometry to six equivalent Nb and eight equivalent Cr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbCr3 by Materials Project

CrCr2Nb is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Nb is bonded to twelve Cr atoms to form distorted NbCr12 cuboctahedra that share corners with four equivalent NbCr12 cuboctahedra, edges with eight equivalent NbCr12 cuboctahedra, edges with sixteen equivalent CrNb4Cr8 cuboctahedra, faces with four equivalent NbCr12 cuboctahedra, and faces with eight equivalent CrNb4Cr8 cuboctahedra. There are four shorter (2.48 Å) and eight longer (2.83 Å) Nb–Cr bond lengths. There are two inequivalent Cr sites. In the first Cr site, Cr is bonded in a distorted square co-planar geometry to four equivalent Nb and eight equivalent Cr atoms. All Cr–Cr bond lengths are 2.83 Å. In the second Cr site, Cr is bonded to four equivalent Nb and eight Cr atoms to form distorted CrNb4Cr8 cuboctahedra that share corners with twelve equivalent CrNb4Cr8 cuboctahedra, edges with eight equivalent NbCr12 cuboctahedra, edges with eight equivalent CrNb4Cr8 cuboctahedra, faces with four equivalent NbCr12 cuboctahedra, and faces with ten equivalent CrNb4Cr8 cuboctahedra. All Cr–Cr bond lengths are 2.48 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbCr3 by Materials Project

CrCr2Nb is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Nb is bonded to twelve equivalent Cr atoms to form NbCr12 cuboctahedra that share corners with twelve equivalent NbCr12 cuboctahedra, edges with twenty-four equivalent CrNb4Cr8 cuboctahedra, faces with six equivalent NbCr12 cuboctahedra, and faces with twelve equivalent CrNb4Cr8 cuboctahedra. All Nb–Cr bond lengths are 2.69 Å. Cr is bonded to four equivalent Nb and eight equivalent Cr atoms to form CrNb4Cr8 cuboctahedra that share corners with twelve equivalent CrNb4Cr8 cuboctahedra, edges with eight equivalent NbCr12 cuboctahedra, edges with sixteen equivalent CrNb4Cr8 cuboctahedra, faces with four equivalent NbCr12 cuboctahedra, and faces with fourteen equivalent CrNb4Cr8 cuboctahedra. All Cr–Cr bond lengths are 2.69 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb3Cr by Materials Project

Nb3Cr is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent Nb sites. In the first Nb site, Nb is bonded in a distorted body-centered cubic geometry to four equivalent Nb and four equivalent Cr atoms. All Nb–Nb bond lengths are 2.79 Å. All Nb–Cr bond lengths are 2.79 Å. In the second Nb site, Nb is bonded in a distorted body-centered cubic geometry to eight equivalent Nb and six equivalent Cr atoms. All Nb–Cr bond lengths are 3.22 Å. Cr is bonded in a distorted body-centered cubic geometry to fourteen Nb atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb3Cr by Materials Project

Nb3Cr is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Nb sites. In the first Nb site, Nb is bonded in a distorted square co-planar geometry to eight equivalent Nb and four equivalent Cr atoms. All Nb–Nb bond lengths are 3.05 Å. All Nb–Cr bond lengths are 2.68 Å. In the second Nb site, Nb is bonded to eight Nb and four equivalent Cr atoms to form NbNb8Cr4 cuboctahedra that share corners with twelve equivalent NbNb8Cr4 cuboctahedra, edges with eight equivalent NbNb8Cr4 cuboctahedra, edges with eight equivalent CrNb12 cuboctahedra, faces with four equivalent CrNb12 cuboctahedra, and faces with ten equivalent NbNb8Cr4 cuboctahedra. All Nb–Nb bond lengths are 2.68 Å. All Nb–Cr bond lengths are 3.05 Å. Cr is bonded to twelve Nb atoms to form CrNb12 cuboctahedra that share corners with four equivalent CrNb12 cuboctahedra, edges with eight equivalent CrNb12 cuboctahedra, edges with sixteen equivalent NbNb8Cr4 cuboctahedra, faces with four equivalent CrNb12 cuboctahedra, and faces with eight equivalent NbNb8Cr4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb3Cr by Materials Project

Nb3Cr is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Nb is bonded to eight equivalent Nb and four equivalent Cr atoms to form NbNb8Cr4 cuboctahedra that share corners with twelve equivalent NbNb8Cr4 cuboctahedra, edges with eight equivalent CrNb12 cuboctahedra, edges with sixteen equivalent NbNb8Cr4 cuboctahedra, faces with four equivalent CrNb12 cuboctahedra, and faces with fourteen equivalent NbNb8Cr4 cuboctahedra. All Nb–Nb bond lengths are 2.92 Å. All Nb–Cr bond lengths are 2.92 Å. Cr is bonded to twelve equivalent Nb atoms to form CrNb12 cuboctahedra that share corners with twelve equivalent CrNb12 cuboctahedra, edges with twenty-four equivalent NbNb8Cr4 cuboctahedra, faces with six equivalent CrNb12 cuboctahedra, and faces with twelve equivalent NbNb8Cr4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb2Cr by Materials Project

Nb2Cr1 is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Nb is bonded to six equivalent Nb and six equivalent Cr atoms to form a mixture of corner, edge, and face-sharing NbNb6Cr6 cuboctahedra. All Nb–Nb bond lengths are 2.70 Å. All Nb–Cr bond lengths are 3.17 Å. Cr is bonded in a 12-coordinate geometry to twelve equivalent Nb and four equivalent Cr atoms. All Cr–Cr bond lengths are 3.31 Å.

36 MATERIALS SCIENCE↗