Mechanical strength testing of irradiated HTR graphite grades M.C.R. Heijna, J.A. Vreeling NRG,...
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Transcript of Mechanical strength testing of irradiated HTR graphite grades M.C.R. Heijna, J.A. Vreeling NRG,...
![Page 1: Mechanical strength testing of irradiated HTR graphite grades M.C.R. Heijna, J.A. Vreeling NRG, Petten The Netherlands INGSM-14 18 September 2013 Seattle.](https://reader036.fdocuments.us/reader036/viewer/2022081420/56649dc65503460f94aba74a/html5/thumbnails/1.jpg)
Mechanical strength testing of irradiated
HTR graphite gradesM.C.R. Heijna, J.A. Vreeling
NRG, Petten
The Netherlands
INGSM-14
18 September 2013
Seattle
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Outline
• Introduction– HTR graphite– INNOGRAPH irradiation programme
• Tensile strength from diametric compression– Why?– How?
• Results– Movies!– Trends for coke, grain size, production process
• Conclusions
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HTR Graphite• Two types of (V)HTR:
• pebble bed• prismatic block
• Graphite as moderator• Structural material
Images from Wikipedia
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INNOGRAPH programme
European Commission Framework Programmes:• Retain (V)HTR knowledge• Screen properties of modern graphite grades
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INNOGRAPH programme
INNOGRAPH-1A: 750°C, 5-10 dpa
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INNOGRAPH programme
INNOGRAPH-1B: 750°C, 10-25 dpaINNOGRAPH-2A: 950°C, 4-8 dpaINNOGRAPH-2B: 950°C, 8-15 dpa
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INNOGRAPH programme
INNOGRAPH-1B: 750°C, 10-25 dpaINNOGRAPH-2A: 950°C, 4-8 dpaINNOGRAPH-2B: 950°C, 8-15 dpa
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INNOGRAPH programme
INNOGRAPH-1C: 750°C, 1-2 dpaIrradiation will be concluded this month
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INNOGRAPH design
• Selected irradiated samples from “1A”and “2A” were further irradiated in “1B” and “2B”
• INNOGRAPH-1B and -2B have been assembled in the NRG hot-cells
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INNOGRAPH design• Each experiment contains 24 thermocouples and
9 dosimeter sets
• Temperature controlled by gas mixture
• Temperature control within ±30°C
• In the order of 180-220 samples per experiment
• Sample geometry:
• 6 mm high, 8 mm diameter
• Flat side with sample coding
• Samples in inert environment
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Graphite grades
Manufacturer Grade Coke Process
IG-110 petroleum iso-moulding
IG-430 pitch iso-mouldingNBG-10 pitch extrusionNBG-17 pitch vibro-mouldingNBG-18 pitch vibro-mouldingNBG-25 petroleum iso-moulding
PCEA petroleum extrusionPCIB petroleum iso-mouldingPPEA pitch extrusionLPEB Needle extrusionLPIB Needle iso-moulding
GrafTech
Toyo Tanso
SGL
Major grades for this programme
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Irradiation in HFR, Petten
• Tank-in-pool type MTR• 40 MW thermal• Operated by NRG
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Post Irradiation Examination
Data on 800 graphite samples• Dimensional change• Density• Young’s modulus• Coefficient of Thermal Expansion• Thermal conductivity• Electrical resistivity
sample recovery
measurements
data set
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Test matrix strength measurements
• Irradiation temperature 750°C
• Fine grains and coarse grains
• Pet & pitch coke• Various production
processes• Different levels of dpa’s /
volume change
• Sample selection limited by:
• Reloaded samples• Microscopy samples
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Diametric compression
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Why diametric compression?
Typical tensile test geometry INNOGRAPH geometry
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Tensile strength from diametric compression
S.P. Timoshenko, J.N. Goodier, “Theory of elasticity”, 1970H. Awaji, J. Soc. Mat. Sci. Jap. 27 (1987)C. Berre et al., unpublished
Tensile strength < Compressive strength
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Tensile strength from diametric compression
z = unique direction
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Experiment! Coarse grain graphite
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Experiment! Fine grain graphite
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Strength vs dpa; Grain size
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Strength vs dpa; Grain size
DV/V0
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Scanning Electron Microscopy
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Fine grain, 0 dpaGrade C
Coarse grain, 0 dpaGrade A
Fine grain, 13.4 dpaGrade C
Coarse grain, 12.8 dpaGrade A
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Strength vs dpa; Coke
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Strength vs dpa; Process
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Conclusions
• Successful irradiation and PIE campaign concluded by demolishing samples
• Tensile strength vs. dpa trends derived from diametric compression
• At turn-around, strength doubles– Regardless of grain size, coke, production process
• Fine grained graphite stronger than coarse grained– Regardless of irradiation
• Coke and process have negligible effect on tensile strength
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Conclusions
• Successful irradiation and PIE campaign concluded by demolishing samples
• Tensile strength vs. dpa trends derived from diametric compression
• At turn-around, strength doubles– Regardless of grain size, coke, production process
• Fine grained graphite stronger than coarse grained– Regardless of irradiation
• Coke and process have negligible effect on tensile strength
Thank you for your attention!