7.1 yagnik effect of hydride distribution
TRANSCRIPT
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Effect of Hydride Distribution on the Mechanical Properties of Zirconium Alloy Fuel Cladding and
Guide Tubes
S. K. Yagnik1, J-H Chen2, and R-C Kuo21 EPRI (USA), 2 INER Taiwan
17th International Symposium on Zirconium in the Nuclear IndustryHyderabad (India)February 3-7, 2013
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Presentation outline
• IntroductionE i t l• Experimental– Hydride Distributions and Materials Tested
Specimen Geometry/Feasibility Study/Bending Effects– Specimen Geometry/Feasibility Study/Bending Effects– Validation of Test Procedure
• ResultsResults– Scope of Testing
• Data and Discussion– Elongation/Strength/Fractography/Effect of Material
processingC l i
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• Conclusions
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Introduction (1)Eff t f h d id th h i l i t it f Z• Effects of hydrides on the mechanical integrity of Zr-alloy fuel assembly components depend on three main characteristics:
– Concentration (ppm of H);
Morphology (orientation and spacing of hydride– Morphology (orientation and spacing of hydride platelets);
– Distribution/Localization– Distribution/Localization
• Re: hydride Distribution in fuel cladding, typically,
– Hydride rim (e.g., H migration down the temperature gradient);
Bli t /L ( d t id ll ti )
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– Blisters/Lens (e.g., due to oxide spallation)
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Introduction (2)• Typically, at comparable hydrogen contents, hydride
localization is more detrimental
Hydride
Hydride Rim
yLens
Present Study15th Symposium (2007); STP-1505
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Hydride Distributions in Materials Tested• Unirradiated SRA Zr- 4 Cladding:
Uniform Rimmed Layered
• Irradiated RXA Zr-4 Guide Tube:
• Uniform hydrides
• 7 x 1025 n/cm2
(E>1 MeV)
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Hydriding Procedures• Uniform: Gas phase charging; including temperature cycling• Rimmed: Uniform (~ 200 ppm) or rim hydriding followed by a
cathodic charging stepcathodic charging step• Layered: Uniform samples imposed with temperature gradient
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Test Samples and Loading Configuration
• Uniaxial tension Test (UTT)– Plane stress
• Slotted-Arc Test (SAT)– Plane strain
– Circumferential hydrides normal to loading direction
– Circumferential hydrides along loading direction
– Considerations for specimenConsiderations for specimen geometry and bending effects
14th Symposium (2005); STP- 1467
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Illustration of hydride distribution in UTT and ISATPISATP
UTT ISATP
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Bending Effects: Defined and FEM Analysis80
60
ect
(%) ISATP
ISATESAT
40
Ben
ding
Eff
0
20
ISATP: Best choice for avoiding bending effects while
0 0.02 0.04 0.06 0.08 0.1Displacement (mm)
0
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retaining interesting high [H] OD region
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Strain and Stress Distributions in one Quadrant of ISATPof ISATP
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ISATP Sample Fabrication
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Validation of Test Procedure
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Results: Ductility Data ObtainedF th th t f h d id di t ib ti d t• For the three types of hydride distributions and two types of loading configurations at RT and 300°C:– Uniform(UE) and Total Elongation (TE) as a functionUniform(UE) and Total Elongation (TE) as a function
of [H]• 3 distributions x 2 test type x 2 temps x 2 elongations = 24
data setsdata sets
– Plotted in this format (by linear regression)• Elongation = Constant − Slope * [H]g p [ ]
• Ultimate Tensile Strength (UTS) and Yield Strength (YS)– Compared for the three distributions– Compared for irradiated RXA GT vs irradiated SRA
cladding • Fractography (comparative fracture modes)
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• Fractography (comparative fracture modes)
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TE and UE at RT for UTT Geometry
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TE and UE at 300°C for UTT Geometry
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TE and UE at RT for ISATP Geometry
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TE and UE at 300°C for ISATP Geometry
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Summary Elongation Data (by Linear Regression)Regression)
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UTS and YS at 300°C
UTT ISATP
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UTT ISATP
Not affected by hydride distribution
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Fractography Compared Uniform vs Layered (following RT ISATP)( g )Uniform; [H] = 719 ppm Layered; [H] = 849 ppm
Fewer microcracks
Many microcracks
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Fewer microcracks
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Fractography Compared Uniform vs Layered (following 300°C ISATP)( g )Uniform; [H] = 842 ppm Layered; [H] = 778 ppm
Ductile dimples Ductile dimples Brittle microcracksand
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Fractography Compared Rim vs Layered (following RT UTT; longitudinal section)( g ; g )Rim = 60 μm Rim = 60 μm + hydride layering
Total [H] = 700ppm Total [H] = 843ppm
A combination of tesnile separation and shear fracturing
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A combination of tesnile separation and shear fracturing
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Fractography Compared Rim vs Layered (following RT ISATP; cross- section)( g ; )Rim = 40 μm Rim = 40 μm + hydride layeringTotal [H] = 2363ppm
Total [H] = 1020ppm
The width of tesnile separation increased
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TE and UE Compared at 300°C between Irradiated RXA and SRA Materials (from UTT)Irradiated RXA and SRA Materials (from UTT)
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Limited SRA Cladding data (ESAT)
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Conclusions (1)E t i h i l t ti h b f d• Extensive mechanical testing has been performed on small miniature specimens (cut-outs), emphasizing hydride localization, reaching the following conclusions:y , g g
1.Elongations decrease with increase in bulk [H] and hydride rim and layer thickness
2.Uniformly hydrided material sustains the largest deformation. At comparable [H], the ductility ranks (from good to best):g )
hydride layered < hydride rimmed < uniformly hydrided
3.Effective tensile strengths show little dependence on [H] and hydride rim thickness
4.Depending on [H], the fracture of uniformly hydrided material occurs by a shear process
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material occurs by a shear process.
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Conclusions (2)5 H d id i d d h d id l d i5. Hydride rimmed and hydride-layered specimens
fail by a combined process of tensile separation (rim and dense hydrides region) and shear ( y g )fracture (alloy matrix region)
6. Combination of [H] and hydride distribution governs the ductilitygoverns the ductility
– Elongations quantified by linear regression;– RXA and SRA Zr-4 compared (within limited [H])RXA and SRA Zr 4 compared (within limited [H])
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Together Shaping the Future of ElectricityTogether…Shaping the Future of Electricity
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