Mechanical strength testing of irradiated HTR graphite grades
description
Transcript of Mechanical strength testing of irradiated HTR graphite grades
Mechanical strength testing of irradiated
HTR graphite gradesM.C.R. Heijna, J.A. Vreeling
NRG, Petten
The Netherlands
INGSM-14
18 September 2013
Seattle
2
Outline
• Introduction– HTR graphite– INNOGRAPH irradiation programme
• Tensile strength from diametric compression– Why?– How?
• Results– Movies!– Trends for coke, grain size, production process
• Conclusions
3
HTR Graphite• Two types of (V)HTR:
• pebble bed• prismatic block
• Graphite as moderator• Structural material
Images from Wikipedia
4
INNOGRAPH programme
European Commission Framework Programmes:• Retain (V)HTR knowledge• Screen properties of modern graphite grades
5
INNOGRAPH programme
INNOGRAPH-1A: 750°C, 5-10 dpa
6
INNOGRAPH programme
INNOGRAPH-1B: 750°C, 10-25 dpaINNOGRAPH-2A: 950°C, 4-8 dpaINNOGRAPH-2B: 950°C, 8-15 dpa
7
INNOGRAPH programme
INNOGRAPH-1B: 750°C, 10-25 dpaINNOGRAPH-2A: 950°C, 4-8 dpaINNOGRAPH-2B: 950°C, 8-15 dpa
8
INNOGRAPH programme
INNOGRAPH-1C: 750°C, 1-2 dpaIrradiation will be concluded this month
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
10
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
11
Graphite grades
Manufacturer Grade Coke Process
IG-110 petroleum iso-mouldingIG-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
12
Irradiation in HFR, Petten
• Tank-in-pool type MTR• 40 MW thermal• Operated by NRG
13
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
14
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
15
Diametric compression
16
Why diametric compression?
Typical tensile test geometry INNOGRAPH geometry
17
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
18
Tensile strength from diametric compression
z = unique direction
19
Experiment! Coarse grain graphite
20
Experiment! Fine grain graphite
21
Strength vs dpa; Grain size
22
Strength vs dpa; Grain size
DV/V0
Scanning Electron Microscopy
23
Fine grain, 0 dpaGrade C
Coarse grain, 0 dpaGrade A
Fine grain, 13.4 dpaGrade C
Coarse grain, 12.8 dpaGrade A
24
Strength vs dpa; Coke
25
Strength vs dpa; Process
26
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
27
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!