The AGC-1 Creep Experiment - Results and Analysis

INGSM-15HANGZHOU, CHINASept 15-18, 2015

Tim Burchell Fusion Materials & Nuclear Structures GroupMaterials Science & Tech. Division

andWill WindesIdaho National Laboratory

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Acknowledgements

This work is sponsored by the

U.S. Department of Energy, Office of Nuclear Energy Science and Technology under contract DE-AC05-00OR22725 with Oak Ridge National

Laboratory, managed by UT-Battelle, LLC.

The author wishes to acknowledge the contributions of Ashli Clark (ORNL)

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The AGC-1 Graphite Creep ExperimentOutline of Presentation

•The AGC Graphite Creep Experiment•The AGC-1 Graphite Creep Capsule•AGC-1 Graphite Graphites & Specimens•Graphite Post Irradiation Examination (PIE) Testing

• Creep Strain Analysis• (all data analyzed, no data rejected)• Comparison with H-451 and IG-110 ”historical” data for dimensions &

volume change• Creep Coefficient, K

•Other Grades in AGC-1: NBG17; NBG-18; PCEA; IG-430• Dimensions• Creep Coefficient, K

•Comparison of second stage creep coefficients, K, for the various grades examined with literature data•KE0 Comparison for all six grades in AGC-1•Conclusions

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The AGC Graphite Creep Experiment

• The AGC Creep experiment comprises six ATR irradiation capsules that shall provide data over the reactor design envelope

• AGC-1 was the first of these capsules (prototype) and shall provide design data (at Tirr ~ 600°C) on:

o Effect of neutron Irradiation on the dimensions and key physical properties of graphite

o Graphite creep strain and creep rate data

o Effect of neutron Irradiation induced creep strain on key physical properties of graphite

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The AGC-1 Graphite Creep Capsule

Experimental Variables (Creep/Control Specimen)

•Specimen Orientation: WG/AG

•Graphite Grades: NBG-18, NBG-17, H-451, PCEA, IG-110, IG-430

•Irradiation Dose Range: 2.8 – 6.9 DPAo Measured with flux wires

•Irradiation Temperature Range: Approximately 472-710 °Co Measured with TC’s and SiC temperature monitors

•Applied Stress (nominal): o 2 channels @ 2 ksi (13.8 MPa)

o 2 channels @ 2.5 ksi (17.3 MPa)

o 2 channels @ 3 ksi (20.7 MPa)

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The AGC Graphite Creep Experiment

The major Grades in the AGC series*

Graphite Grade Forming Method Intended Purpose AGC Code Letter

NBG-17 Vibrational molded AREVA NGNP Design A

NBG-18 Vibrational molded PBMR (not currently being pursued) B

H-451 Extruded Historical Grade (REF) C

PCEA Extruded AREVA NGNP Design D

IG-110 Isostatically Pressed PMBR-DM (China) – Under construction

E

IG-430 Isostatically Pressed Candidate Graphite F

*GRADE 2114 (MERCEN) ADDED IN AGC-2 ONWARDS

Specimen quantities: NBG-17 = 34; NBG-18 = 34; H-451 (Reference Grade) = 20; PCEA = 34; IG-110 (Reference Grade) = 20; IG-430 =32. Total = 174 SPECIMENS

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The AGC-1 Graphite Creep Experiment

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The AGC-1 Graphite Creep Experiment

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The AGC-1 Graphite Creep Experiment

Transient Creep

Steady State or “Linear” Creep

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The AGC-1 Graphite Creep Experiment

Creep and Control Specimen Volume Change Similar (especially at lower doses).

All six graphites observed to have similar creep and control volume change curves!

CREEP AT CONSTANT VOLUME

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The AGC-1 Graphite Creep Experiment

H-451 dimensional change,%

Specimen Length (WG)

Specimen Diameter (AG)

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The AGC-1 Graphite Creep Experiment

Longitudinal (WG) creep strain plots for grade H-451

Normalized creep strain (WG)

Coefficient, K = -0.0203 %/DPA·MPa or 0.138 x 10-30 cm2/n·Pa

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The AGC-1 Graphite Creep Experiment

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The AGC-1 Graphite Creep Experiment

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The AGC-1 Graphite Creep Experiment

Creep coefficients summary

Grade Code

Secondary creep strain coefficient,K,

%/DPA.MPa

Total creep strain coefficient

micron/DPA

Creep strain Ratio

Secondary creep strain coefficient, K,10-30cm2/n.Pa

Longitudinal Lateral Longitudinal Lateral Longitudinal Lateral NBG-17 A 0.015 0.025 -72.541 17.602 -0.243 0.099 0.170NGB-18 B 0.014 0.021 -70.968 15.281 -0.215 0.096 0.145H-451 C 0.020 0.026 -102.18 18.11 -0.177 0.138 0.176PCEA D 0.018 0.022 -90.927 15.823 -0.174 0.124 0.151IG-110 E 0.020 0.044 -101.49 20.583 -0.203 0.137 0.195IG-430 F 0.032 0.041 -75.431 19.561 -0.259 0.219 0.281

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The AGC-1 Graphite Creep Experiment

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The AGC-1 Graphite Creep Experiment

H-451 total creep strain in microns

Creep strain ratio = Ɛ(lat)/Ɛ(long) = (18.11/-102.18) = -0.18

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The AGC-1 Graphite Creep Experiment

Mean ± 1Standard Deviation

H-451 Poisson's Ratio (unirradiated), ν = -0.31 ± 0.01

H-451 Poisson's Ratio (irradiated unstressed or control specimen), νirr = -0.29 ± 0.03 H-451 Poisson's Ratio (irradiated stressed or crept specimens), νirr = -0.28 ± 0.04

H-451 Creep strain ratio ƐC(lat)/ƐC(long) = -0.18

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A Comparison of Poisson's Ratio (irradiated and Unirradiated and The Creep Strain Ratio for the Six Graphites in AGC-1

Graphite Grade

Grade Letter

Piosson's RatioCreep Strain

RatioUnirradiated Control Creep

NBG-17 A 0.33 0.26 0.24 0.24

NGB-18 B 0.32 0.27 0.25 0.20

H-451 C 0.31 0.28 0.27 0.18

PCEA D 0.25 0.27 0.25 0.17

IG-110 E 0.25 0.20 0.17 0.20

IG-430 F 0.17 0.19 0.19 0.26

The AGC-1 Graphite Creep Experiment

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The AGC-1 Graphite Creep Experiment

NBG-17 and IG-430 ARE SUSPECT!

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The AGC-1 Graphite Creep Experiment

CONCLUSIONS

1. The AGC-1 creep capsule has completed its irradiation, it has been dismantled, the specimens & Tmonitors shipped to ORNL. PIE (except strength testing) has been completed.

2. Grades NBG-17, NBG-18, H-451, PCEA, IG-110 and IG-430 were examined3. Initial analysis of dimensional change and creep strain data for all graphites

completed4. Thermal design/control/operation of AGC-1 was not optimal and made the

analysis more challenging5. The dimensional behavior of H-451 and IG-110 compare favorably with

previous data6. The volume change behavior of the creep and control samples were seen to

be similar, especially at lower doses, for all six grades7. The creep strain data are linear and lend themselves to analysis using the

simple “linear” creep law.

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The AGC-1 Graphite Creep Experiment

CONCLUSIONS (continued)8. Creep strain was normalized to applied stress and plotted against dose,

creep strain data falls on common line9. The use of the linear creep model is justified at the low doses encountered in

AGC-110.K for all graphites compares favorably with literature data11.Comparing K.E0 for all six graphites (longitudinal and lateral) revealed NBG-

17 and IG-430 data to be suspect

Next Steps: Eliminate dimensional/creep data from AGC-1 analysis where Tirr >500°C but <700°C, and the temperature difference between creep and control specimen pairs is > 100°C