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All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

A microstructure-based modeling approach to predict the mechanical properties of Zr alloy with hydride precipitates

In nuclear reactors, hydrides can form in fuel cladding due to hydrogen absorption in ZIrcaloy and cause embrittlement. This work presents a microstructure-based finite element model to predict the stress-strain response of Zircaloy containing hydrides. Quantitative microstructural details extracted from scanning electron microscopy (SEM) images were used to generate heterogeneous microstructures including the morphology and spatial distribution of hydrides. The constitutive material model for zircaloy in this study is based on crystal plasticity theory which considers the hexagonal close-packed (HCP) atomic structure of Zircaloy material. The hydrides were modeled as brittle material along with a damage model. Hydride formation inside the zircoloy matrix results in residual stress. This phenomenon is also captured in this model. A parametric study has been conducted to understand the effect of volume fraction, orientation, and lamellae thickness of the hydride phase on the mechanical properties of the overall material.

Kulkarni, Shank S.↗
DOE OSTI2022

Capability to Process and Characterize Uranium-Zirconium (U-Zr) and Uranium-Zirconium-Plutonium (U-Zr-Pu) Alloys

This work investigated co-reduction of anhydrous compounds of uranium, zirconium, and plutonium to produce uranium rich ternary nuclear fuel alloys. Metallothermic co-reduction is a novel method to produce all-metal nuclear fuels. Metal fuels offer thermal, fissility, compatibility, and security benefits over oxide fuels. Alloys of uranium–10% zirconium with plutonium contents of 0%, 2.5%, 5%, and 10% were produced, with yields of 60–85% of theoretical values in a traditional calciothermic bomb reduction apparatus. Microstructural analysis indicated transformation of uranium phase from gamma to beta and then alpha, in alternating lamellar plates typical of alpha phase uranium and delta phase uranium-zirconium, with zirconium and carbides at prior grain boundaries. Some of the analyses were inconclusive in their results and therefore require additional testing. Successful ternary co-reduction would simplify production of homogeneous feedstock and thereby streamline manufacture of homogeneous ternary metallic fuel.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2026

Improving creep resistance of Al-0.27Zr-0.08Sn (wt%) via cold swaging while maintaining high electrical conductivity

This study investigates the effect of mechanical cold work (0, 50, and 90% cross-sectional area reduction via swaging) on the creep properties of cast aluminum alloys with high electrical conductivity including high-purity Al (HP-Al), Al-0.15Zr (Al-Zr), and Al-0.27Zr-0.08Sn (Al-Zr-Sn, wt%). The Al-Zr alloy is strengthened by Zr in solid solution while the Al-Zr-Sn alloy is additionally strengthened by Al3Zr nanoprecipitates (8 nm diameter). After 90% cold swaging, the alloys exhibit grains elongated along the swaging direction with their widths ranging between 8 and 152 μm perpendicular to the swaging direction. Creep testing at 200 °C shows that the minimum creep rate of all 90% swaged alloys shows high sensitivity to stress, which can be modeled via a threshold stress σth. Increasing swaging magnitude from 0 to 50 to 90% in Al-Zr-Sn improves the creep resistance without reducing electrical conductivity. The formation of subgrains, increased dislocation density, and columnar grain structure in swaged alloys all enhance creep resistance. HP-Al swaged to 90% exhibits much lower creep resistance (σth = 18 MPa) due to subgrain coarsening and the absence of precipitates compared to Al-Zr (σth = 40 MPa) and Al-Zr-Sn (σth = 40 MPa), which maintain stable subgrain structures and benefit from solid solution strengthening and Al3Zr nanoprecipitates, respectively. Although Al3Zr precipitates are known to stabilize the deformed microstructure by pinning grain-boundaries, this work demonstrates that Zr in solid solution alone can effectively stabilize the deformed microstructure resulting in enhanced creep resistance. This effect of Zr solute on stabilizing grain boundaries for creep performance was not previously well-defined in the literature. Despite similar creep performances of Al-Zr and Al-Zr-Sn, the latter shows 70% higher room-temperature microhardness and slightly improved electrical conductivity (56%IACS (International Annealed Copper Standard) vs. 57%IACS, respectively). This work provides new insights into creep mechanisms of cold-worked Al–Zr alloys that will guide the design of heat-resistant Al conductors for high-demand applications.

Coello ramirez, Ismael [Northwestern University,]↗
DOE OSTI2023

Zirconium Nuclear Data Campaign: Measurement of 90 Zr ( n, γ ) Cross Section

The isotopes of Zr with A = [90, 91, 92, 94] make up more than 97% of naturally occurring Zr and are important to many nuclear applications such as nuclear reactors. One of the attractive qualities of naturally occurring Zr isotopes is that they have a low σ γ /σ t ratio at most neutron energies. Thus, they improve the neutron economy in reactors by preferentially scattering neutrons rather than absorbing them. This same quality also presents a challenge to measuring the capture cross section, σ γ , of Zr isotopes. The ENDF/B VIII.0 library has a relative uncertainty of approximately 10–20% for incident neutron energies < 0.1 MeV and an uncertainty greater than 20% for energies > 0.1 MeV for the majority of natural Zr isotopes. This motivated the Nuclear Criticality Safety Program to embark on a campaign to accurately measure and evaluate these Zr isotopes. In this work, we demonstrate energy-dependent neutron capture cross section measurements for the first enriched sample to be measured: 90 Zr.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2020

Materials Data on Zr(ClO4)4 by Materials Project

Zr(O4Cl)4 is alpha oxygen structured and crystallizes in the monoclinic Cc space group. The structure is zero-dimensional and consists of four Zr(O4Cl)4 clusters. Zr is bonded to eight O atoms to form distorted ZrO8 hexagonal bipyramids that share edges with four ClO4 tetrahedra. There are a spread of Zr–O bond distances ranging from 2.21–2.26 Å. There are fifteen inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.42 Å. In the second O site, O is bonded in a water-like geometry to one Zr and one Cl atom. The O–Cl bond length is 1.53 Å. In the third O site, O is bonded in a water-like geometry to one Zr and one Cl atom. The O–Cl bond length is 1.53 Å. In the fourth O site, O is bonded in a water-like geometry to one Zr and one Cl atom. The O–Cl bond length is 1.54 Å. In the fifth O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.42 Å. In the sixth O site, O is bonded in a water-like geometry to one Zr and one Cl atom. The O–Cl bond length is 1.54 Å. In the seventh O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.42 Å. In the eighth O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.42 Å. In the ninth O site, O is bonded in a water-like geometry to one Zr and one Cl atom. The O–Cl bond length is 1.53 Å. In the tenth O site, O is bonded in a water-like geometry to one Zr and one Cl atom. The O–Cl bond length is 1.54 Å. In the eleventh O site, O is bonded in a water-like geometry to one Zr and one Cl atom. The O–Cl bond length is 1.54 Å. In the twelfth O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.42 Å. In the thirteenth O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.42 Å. In the fourteenth O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.42 Å. In the fifteenth O site, O is bonded in a water-like geometry to one Zr and one Cl atom. The O–Cl bond length is 1.53 Å. There are four inequivalent Cl sites. In the first Cl site, Cl is bonded to four O atoms to form ClO4 tetrahedra that share an edgeedge with one ZrO8 hexagonal bipyramid. In the second Cl site, Cl is bonded to four O atoms to form ClO4 tetrahedra that share an edgeedge with one ZrO8 hexagonal bipyramid. In the third Cl site, Cl is bonded to four O atoms to form ClO4 tetrahedra that share an edgeedge with one ZrO8 hexagonal bipyramid. In the fourth Cl site, Cl is bonded to four O atoms to form ClO4 tetrahedra that share an edgeedge with one ZrO8 hexagonal bipyramid.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr by Materials Project

Zr crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Zr sites. In the first Zr site, Zr is bonded in a 10-coordinate geometry to ten Zr atoms. There are a spread of Zr–Zr bond distances ranging from 3.10–3.14 Å. In the second Zr site, Zr is bonded in a 9-coordinate geometry to nine Zr atoms. There are a spread of Zr–Zr bond distances ranging from 3.01–3.24 Å.

36 MATERIALS SCIENCE↗