shuhei nogami tohoku university, japan 3/2. nogami.pdfembrittlement low temperature brittleness....

$: Shuhei Nogami Tohoku University, Japan 3/2. Nogami.pdfembrittlement Low temperature brittleness. Rieth et al., JNM, 2019. Low temperature brittleness (low fracture toughness and high$
Shuhei NogamiTohoku University, Japan

AcknowledgementM. Rieth, P. Lied (KIT), G. Pintsuk (FZJ), T. Hirai (IO), J.H. You (IPP),

M. Fukuda (QST), R. Kasada, A. Hasegawa (Tohoku U.), Y. Hatano (U. Toyama)

1

Outline

1. Introduction

2. Tungsten-based materials as an armor

3. Copper-based materials as heat sink and cooling pipe

4. Irradiation projects of materials for divertors

5. Issues for evaluation and prediction of structural strength and lifetime

6. Summary and Conclusion

Introduction

3

Requirements of Divertors

n Requirementsü Removal of waste material (helium) from plasmaü Cooling capability --- thermal conductivity (W, Cu, etc.), coolant (water, etc.) ü Structural reliability --- strength, ductility, corrosion resistance, etc.ü Long-term operation for DEMOü Assessment of time-dependent degradation (neutron irradiation damage, etc.)

for DEMO

You et al., DVM, Mittweida, 2017

4

Damage and Degradation of Divertors

n Damage and degradation of materials and jointsü Degradation of physical and mechanical properties by

--- surface modification (melting and fuzz, etc.)--- macro-, micro-cracking (thermal fatigue, etc.)--- displacement damage (embrittlement, etc.)--- transmutation (Re, Os, and He, etc.)

Pintsuk et al., FED, 2013

Wirtz et al., NME, 2016

5

Damage and Degradation of Divertors

n Damage and degradation of materials and jointsü Volume change

- plastic strain accumulation (ratcheting, etc.)- creep deformation- swelling (voids, bubbles etc.)

ü Tritium issues- accumulation in materials and interfaces- interaction with defects by neutron irradiation

Merola et al., FED, 2015

Ogorodnikova et al., JNM, 2018

6

Neutron Irradiation Effects

ü Heat--- Steady state (stationary): 10 MW/m2

--- Slow transient: 20 MW/m2

--- ELM (fast transient): a few ten GW/m2

ü Neutron --- 15 dpa in W and 60 dpa in Cu (after 5 years)ü Ions (D, T, He) --- 1023 ions/m2/s

Reactor ITER DEMO

Material W Cu W Cu

Component replacements up to 3 5 year cycle

Av. neutron fluence [MWa/m2] Max. 0.15 5

Displacement damage [dpa] 0.7 1.7 15 60

TransmutationHe [appm] negligible 16 10 600

Re [%] 0.15 3Bolt et al., JNM, 2002 & JNM, 2004 and Robinson et al., UWFDM-1378, 2010

Acceptable or negligible

in ITER

7

OFHC-CuCuCrZr

W-based

Limitation of Structural Strength and LifetimeDetermined by Synergistic Loads

Helium(transmutation)

Helium(from plasma)

Sputtering

Solidtransmutation

Hydrogen(transmutation)

Tritium(from plasma)

Irradiationdamage

Oxidation(Accident)

Fatigue

Strength

Ductility

Recrystallization

Creep

Plastic deform.Ratcheting

Thermalconductivity

CorrosionErosion

Surfacemodification

8

Issues on Assessment of Structural Strength and Lifetime

ü DEMO needs an assessment of long-term structural reliability and lifetime.

ü Synergistic loads, time-dependent phenomena, gradient, distribution, and anisotropy of loads and material properties, should be considered.

ü Especially, consideration of neutron irradiation effects is important.

ü Material properties database and handbook and criteria and rules for the assessment of structural strength and lifetime are required.

ü However, lack of enough (experimental) data and knowledge is significant issue at present.

Tungsten-based materialsas an armor

10

Lifetime Limitation due to Degradation of W

20 MW/m2

10 s

1800oC x 1 h

1500oC x 1 h

1300oC x 1 h

1100oC x 1 h

As-received

Longitudinal cracks

Grain ejection (only near large cracks)

Cracks around resolidified layer

Before HHF load

After HHF load

Recrystallizationembrittlement

Low temperaturebrittleness

Rieth et al., JNM, 2019

Low temperature brittleness (low fracture toughness and high DBTT), recrystallization embrittlement, and neutron-irradiation-induced embrittlement will limit the lifetime.

DBTT and TRxx will be a critical factor for the

operation window

Neutronirradiation

embrittlement

11

Development of Tungsten Materials for DEMO

Stre

ss, σ

Test temperature, Tt [oC]

Yield stress (Unirradiated)

Fracture stress(Unirradiated, Irradiated)

Yield stress (Irradiated)

DBTT(Unirradiated)

DBTT(Irradiated)

--- need to increase recrystallization resistance--- need to increase fracture toughness and to lower DBTT

à need to increase strength and ductility--- need to increase neutron irradiation tolerance

12

Operation Window Determined by DBTT and TRxx

Nogami et al., FED, 2018, Bonk et al., IJRMHM, 2016, and Bonnekoh et al., IJRMHM, 2018

Increase in deformation ratio can make the DBTT lower.

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

200 300 400 500 600 700 800 900 1000 1100

Char

py a

bsor

bed

ener

gy [J

]

Test temperature [oC]

Pure WAs-received

L-S direction

Plate, 4 mm thick, (Rieth, Reiser)Plate, 7 mm thickRound-blank, 175 mm dia. x 29 mm thick, (Rieth)

t = 4 mm à ds = 19 μmt = 7 mmà ds = 22 μm

t = 29 mmà ds = 63 μm

13


300

350

400

450

500

550

600

650

700

0 300 600 900 1200 1500 1800

Vick

ers h

ardn

ess

Annealing temperature [oC]

Annealing time = 1 h

Pure W foil(t = 0.2 mm)

Pure W plate（t = 7 mm）

Pure W platet = 6 mm）

Warm-rolled foil w/o SRHot-rolled plate with SR

Nogami et al., ISFNT-14, 2019 and to be published in the FED

High DBTTHigh TRxx

Low DBTTLow TRxx

Increase in deformation ratio can sometimes make the TRxx lower.

DBTT TRxx

14


ü Optimization of deformation ratio is required to obtain acceptable combination of DBTT and TRxx.

ü A method with no increase in the deformation ratio should be considered.


Second-phaseDispersion

Alloying

Grain Refining

15

Modification of Tungsten Materials


ü There are a lot of approaches to modifytungsten.

• Doped W (dispersion-strengthened W,grain-stabilized W)

• W binary alloys by solid solute elements• Ternary and multi-component W alloys• W composites

16

Potassium Doped Tungsten-Rhenium Alloy

200 400 600 800 1000 1200 1400

T / oC

Pure WDBTT TRxx

K-doped W

K-doped W-3%Re

W-3%Re

1600

Reduction of DBTT and increase in TRxx were simultaneously achieved by K-doping and Re-additionwith no increase in the deformation ratio

Nogami et al., FED, 2019

Still

brit

tle

350

400

450

500

550

900 1100 1300 1500 1700 1900 2100 2300

Vick

ers

hard

ness

, HV


As-received, L x S surfacePure W, Plate, 7 mmK-doped W, Plate, 7 mmW-3%Re, Plate, 7mmK-doped W-3%Re, Plate, 7mm

As-received

Higher TRxx

Lower DBTTHigher USE

17

Tungsten Fiber Reinforced Tungsten

Mao et al., Composites Part A, 2018

Wf/W compositewith Y2O3 interfaceby FAST

MatrixInterfaceFiber

Elastic deformation

Matrix crackingPropagation of cracks to interface

Rupture of fibersPull-out of fibersFriction at interface

(c) Ultimate strength (fiber bridging)

(d)

PseudoDuctility

Mass Production à ?

19

Development of Tungsten Materials for DEMO

--- need to increase recrystallization resistance--- need to increase fracture toughness and to lower DBTT

à need to increase strength and ductility--- need to increase neutron irradiation tolerance

Stre

ss, σ

Test temperature, Tt [oC]

Yield stress (Unirradiated)

Fracture stress(Unirradiated, Irradiated)

Yield stress (Irradiated)

DBTT(Unirradiated)

DBTT(Irradiated)

20

Irradiation Effects on Tungsten

Microstructural Change

Koyanagi et al., JNM, 2017

ü Irradiation-induced microstructure dependent on the irradiation conditions (temperature, dose, dose rate, and transmutation etc.)

ü The lack of data from high temperature and high dose neutron irradiation tests

21


Irradiation Hardening

Fukuda et al., JNM, 2014

ü No positive and negative effects of the K-doping and dispersion of La2O3 particlesü Suppression of hardening by Re-addition due to the suppression of formation of

voids and dislocation loopsü Significant hardening after the formation of precipitation

Hasegawa et al., JNM, 2016 & Fukuda et al., Mater. Trans., 2012

22


Irradiation Hardening

ü Significant hardening caused by irradiation-induced precipitation in W-26%Re (χ-phase and σ-phase)

ü Effect of Re on the irradiation hardening could be positive and negative, which is dependent on the irradiation conditions.

Nemoto et al., JNM, 2000, Hasegawa et al., JNM, 2011, Hasegawa et al., JNM, 2016

23


Swelling

W-25%Re

Pure W

ü No voids in W-25%Re induced suppression of swelling, although a large fraction of second phase precipitate was observed.

EBR-IITirrad = 430-1100 oCφt = 1 x 1022 n/cm2 (9.5 dpa) (E > 1 MeV)

Matolich et al., Scr. Metal, 1974

24


Effect of Neutron Spectrum

Hasegawa et al., JNM, 2016 and Katoh et al., JNM, 2019

ü Thermal neutrons cause solid transmutations via (n, γ) neutron capture reactions, resulting in accumulation of Re, Os, and Ta, etc.

ü Higher energy neutrons like 14 MeV neutrons cause gas transmutationsvia (n, α) and (n, p) reactions, resulting in accumulation of He and H.

25



Hasegawa et al., JNM, 2016 and Katoh et al., JNM, 2019

26



Fukuda et al., JNM, 2016Dickinson, Trans. Am. Soc. Met., 1959

ü Significant hardening by precipitation in the non-irradiated conditionsü Higher irradiation hardening produced in the mixed-spectrum fission reactors, HFIR

and JMTR, compared to the fast breeder reactor JOYO

27


Strength and Ductility

EBR-IITirrad = 371-388 oC

φt = 0.4-0.9 x 1022 n/cm2

(E > 1 MeV)

Steichen et al., JNM, 1976

ü Increase in the strength and decrease in the ductility (elongation and reduction in area), especially at low temperature range

28


Strength and Ductility

ü As a recent result from the J-US PHENIX project, K-doping and Re-addition showed a positive effect on the suppression of ductility loss, even at low temperature, accompanied by the positive effects on the non-irradiated thermo-mechanical properties.

Miyazawa et al.,ICFRM-19, 2019

29

Pure W

W-10%Re


DBTT

FRJ2 and HFRTirrad = 252-302 oC

(1 dpa ~ 5 x 1025 n/m2)

Krautwasser et al., 12th International PLANSEE Seminar, 1989

ü Lower DBTT of W-10%Re in the non-irradiated condition compared to the pure Wü Increase in DBTT with increase in irradiation doseü Higher DBTT of W-10%Re in the non-irradiated condition compared to the pure W

30


Thermal Properties

JMTRTirrad = 57 oCφt = 3.37 x 1019 n/cm2

(E > 1 MeV)

Fujitsuka et al., JNM, 2000

Pure W

W-5%Re

W-10%Re

W-25%Re

ü Change in thermal diffusivity was dependent on the content of Re and temperature

31


Effects of Helium by Transmutation

Annealed at 1250 oC for 1 hà Nano bubbles (1 nm) in matrix

Annealed at 1300 oC for 1 hà Nano bubbles (4 nm) at dislocation loops and sub-grain boundaries

Annealed at 1800 oC for 1 hà Nano bubbles (10 nm) at sub-grain boundaries

Annealed at 2100 oC for 1 hà Nano bubbles (10 nm) in matrix after recrystallization

Cyclotron12 MeV alpha with degraderTirrad = 52 oCφt = 600 appm

Chernikov et al., JNM, 1994

DislocationHe bubble

Grainboundary

Helium implantation at 52 oC to 600 appm

ü No significant swellingü No segregation of helium to grain boundaries

32

Neutron Irradiation Effects

ü Heat--- Steady state (stationary): 10 MW/m2

--- Slow transient: 20 MW/m2

--- ELM (fast transient): a few ten GW/m2

ü Neutron --- 15 dpa in W and 60 dpa in Cu (after 5 years)ü Ions (D, T, He) --- 1023 ions/m2/s

Reactor ITER DEMO

Material W Cu W Cu

Component replacements up to 3 5 year cycle

Av. neutron fluence [MWa/m2] Max. 0.15 5

Displacement damage [dpa] 0.7 1.7 15 60

TransmutationHe [appm] negligible 16 10 600

Re [%] 0.15 3Bolt et al., JNM, 2002 & JNM, 2004 and Robinson et al., UWFDM-1378, 2010

33


Retarded Recrystallization

350

400

450

500

550

900 1100 1300 1500 1700 1900 2100 2300

Vick

ers

hard

ness

, HV



As-received

ü Dislocation cell structure in the grain of He-implanted pure W was retained even after the at 1500 oC.

ü Only 20 appm He suppressed the recovery and recrystallization of pure W.

Annealedat 1500 oC

HRed and SRedAs-produced

HRed and SRedHe-implanted

HRed and SRedAs-produced

Hasegawa et al., Phys. Scr., accepted


34

Irradiation Effects on Tungsten1. Neutron irradiation effects must be considered both in the design

and operation phases of DEMO to manage the structural strengthand lifetime under long term operation.

2. Database of neutron irradiation response of W materials arelimited, even for the pure W (baseline material). Especially, thelack of data from high temperature and high dose neutronirradiation tests is an issue.

3. As a recent result from the J-US PHENIX project, K-doping and Re-addition indicated a positive effect on the suppression of ductilityloss, even at low temperature, accompanied by the positiveeffects on the non-irradiated thermo-mechanical properties.

4. Fusion-relevant neutron sources are necessary to confirm theresponse to the 14 MeV neutron irradiation includingtransmutation.

Copper-based materialsas heat sink and cooling pipe

36

Copper-based Materials for DEMO

uMaterials

ü Oxide Dispersion Strengthened Cupper Alloys (ODS-Cu, DS-alloy)--- Cu-Al2O3 (CuAl25-IG, GLIDCOP)

ü Precipitation hardened Cupper Alloys (PH-alloy)--- CuCrZr à CuCrZr-IG for ITER --- CuNiBe

u Issues--- need to increase strength and toughness--- need to decrease CTE mismatch to W-based material--- need to implement corrosion protection--- need to increase neutron irradiation tolerance

37

Lifetime Limitation due to Degradation of Copper-based Materials

Thermal Fatigue of Pipes and Interfaces20 MW/m2 x 1000 cycles

Pintsuk et al., ICFRM-17, 2015void / crack formation in OFCu

Deformationà crack/pore formation & modification of round shaped geometry

Deformation à local reduction of CuCrZr thickness

38


Corrosion of CuCrZr

reducing: without active plasmaoxidizing: with active plasma (neutron induced radiolysis)cyclic: radiolysis is partially suppressed

Pintsuk et al., ICFRM-17, 2015

Corrosion rates of CuCrZr was higher than the structural materials of LWR (< 1 μm/year).

39


Irradiation Damages of PH & DS Cu Alloys

Fabritsiev et al., FED, 1998

ü Irradiation hardeningbelow 300 oC and softening above 300 oC for both PH and DS alloys

Ø PH: Precipitation hardenedØ DS: Dispersion strengthened

40


Irradiation Damages of PH & DS Cu Alloys

Fabritsiev et al., FED, 1998

ü Ductility loss accompanied by the irradiation hardening with decrease in the irradiation temperature for both PH and DS alloys(<1% by below 0.1 dpa)

ü Irradiation-tolerant Cu-based materials

ü Alternative (non Cu-based) materials

are required for heat sink and cooling pipe.

41

Hybrid Cooling Channel Concept using CuCrZr (High-λ) and RAFM Steel (Irradiation Tolerance)

Asakura et al., Nucl. Fusion, 2017

Target

BaffleDome and Reflector

Irradiation projectsof materials for divertors

43

Irradiation Studies in Japan

JAEA JMTR : Japan Materials Testing Reactor 50MW / 7 x 1014 n/cm2/s

Irradiation temperature control rigCan control the irradiation temperature within ±10 degree C

Specimen Type : Miniature Tensile (SS-J, SS-3) , CVN, PCCVN, DCT, Creep,

Heater

TC

Specimens

Gas gap

Outer canister

Inner canister

Heater line

TC line

Vacume temperature control line

Guide tube

JAEA JOYO : Experimental Fast reactor 140MW / 5.7 x 1015 n/cm2/s

Core map of JOYO

Shielding SubassemblyIrradiation Rig (for fuel)

Inner Reflector

Control Rod

ReflectorOuter Core Fuel

Inner Core Fuel

Irradiation Rig (for material)

MARICO : Material Testing Rig with Temperature ControlThe MARICO is being developed to obtain real time irradiation data，such as swelling，creep and rupture strength，on core materials．Specimen temperatures are controlled with an accuracy of ±4℃ by use of combined gas gap and electrical heater control methods．In the gas gap method the composition of a mixture of helium and argon fill gases is modified to increase or decrease the conductance of the gas between the double-wall cannister．

Schedule ofresuming operation

is uncertain.

Shut-down has been decided and no alternative

is uncertain.

Irradiation studies in Japan promoted by IMR-Tohoku university

HFIR : High Flux Isotope Reactor in ORNL BR2 : Belgian Reactor 2 in SCK•CEN

44

Irradiation Projects of Japan-US Collaboration

Task 3Plasma-Surf. Interac.

Tritium Behavior(TPE, Idaho NL)

Task 2Neutron-irrad. Effects

MicrostructurePhysical Properties

(HFIR, ORNL)

Task 1Heat Load Tests

Heat TransferSystem Evaluation

Material Properties

Tritium Behavior

Neutron-irradiatedsamples

2013 2014 2015 2016 2017 2018

Task 1

Task 2

Task 3

Heat transfer tests & turbulence modeling New divertor design

Heat load tests for non-irradiated samples n-irr. samples

Material selectionCapsule design

Low dose non-shielded n-irr.High dose n-irr. with thermal

neutron shielding

Post-irr.Examination

Device modifications

Retention & permeation meas. of non-irr. samples

Retention & permeation meas. of n-irr. samples

Japan USA

Representative Y. Ueda（Osaka U.） D. Clark (DOE)

Coordinator Y. Hatano （U. Toyama） D. Clark (DOE)

Task 1T. Yokomine（Kyoto U.）

Y. Ueda（Osaka U.）A. Sabau (ORNL)

M. Yoda (GIT)

Task 2T. Hinoki （Kyoto U.）

A. Hasegawa（Tohoku U.）Y. Katoh(ORNL)

L. Garrison (ORNL)

Task 3Y. Oya（Shizuoka U.）

Y. Hatano （U. Toyama）M. Shimada (INL)

D. Buchenauer (SNL)

Japan-US PHENIX Project (2013-2018)PFC evaluation by tritium Plasma, HEat and Neutron Irradiation eXperiments

45


Stainless steel

Gadolinium

Aluminum

Garrison et al., FST, 2019

46


1200°CSubcapsule

Garrison et al., FST, 2019

Japan-US Collaboration, PHENIX (~2018) and FRONTIER (2019~), will reveal the irradiation response of both

baseline and advanced W materials developed recently.

Issues for evaluation and prediction of structural strength and lifetime

50

Evaluation and prediction of structural strength and lifetime

Key Factors for DEMO

1. Synergistic Loads

2. Time-dependent

3. Gradient, Distribution, and Anisotropy

4. Material Properties Database and Handbook

5. Prediction and Validation, and Criteria and Rules

51


Key Factors for DEMO1. Synergistic Loadsü Synergistic loads (heat, neutron,

and ions) result in the complicated degradations and damages.

ü Integrated experiments and calculations are required.

HHF Tests after Neutron Irradiation0.2 dpa in C and 0.15 dpa in W (irradiation campaign PARIDE 3)1 dpa in C and 0.6 dpa in W (irradiation campaign PARIDE 4)Irradiation temperatures were 200 C

Roedig et al., JNM, 2004

Neutron HHF

Creep Fatigue Test Module for IFMIFhttps://www.ifmif.org/

Neutron Creep-Fatigue

52


Key Factors for DEMO2. Time-dependentü Degradations and damages caused by cyclic fatigue, creep, ratcheting,

recrystallization, displacement damage, transmutation are time-dependent phenomena.

Merola et al., FED, 2015You et al., FED, 2016 Nogami et al., Phys. Scr., 2017

53

350

400

450

500

550

900 1100 1300 1500 1700 1900 2100 2300

Vick

ers

hard

ness

, HV



As-received

1100

o C

Annealing time [h]

550

500

450

400

350

Vick

ers h

ardn

ess,

HV

0 1 10 100 1000 10000

Pure WK-doped WK-doped W-3%Re

Annealing temp. = 1100 oC




Tsuchida et al., NME, 2018Nogami et al., FED, 2019

54




Hasegawa et al., JNM, 2016

Fukuda et al., JNM, 2016

55


Key Factors for DEMO


3. Gradient, Distribution, and Anisotropyü Gradient, distribution, and anisotropy of applied

heat and temperature, neutron irradiation damage, material properties should be considered.

ZX

Y

W-monoblock

Cooling channel

Plasma facing surfaceR

.D.

Fukuda et al., FST, 2015

56


Typical Issues for DEMO4. Material Properties Database and Handbookü Authorized material properties databases and handbooks are required.ü Definition and licensing of materials are required.

57


Key Factors for DEMO5. Prediction and Validation, and Criteria and Rulesü Integrated experiments and calculations are required to evaluate the structural

strength and lifetime under synergistic loads.

ü It will be required to additionally apply theoretical predictions and calculation-based predictions.

ü Fusion neutron source are required to clarify the effects of 14 MeV neutron irradiation, including transmutation effects.

ü In service condition monitoring, surveillance, and inspection will be important because all degradations and damages cannot be completely predicted before design and operation.

ü Criteria and rules for design and operation, including for maintenance and replacement, etc., should be established.

58

Summary and Conclusion

1. For a long-term structural reliability and lifetime, synergistic loads, time-dependent phenomena, gradient, distribution, and anisotropy of loads andmaterial properties, material properties database and handbook, predictionand validation, and criteria and rules are the key factors.

2. Neutron irradiation effects must be considered both in the design andoperation phases to manage the structural strength and lifetime under longterm operation.

3. Database of neutron irradiation response of W materials are limited, even forthe pure W (baseline mateiral). The irradiation projects under J-UScollaboration (PHENIX (~2018) and FRONTIER (2019~)) and EUROfusion willreveal the irradiation response of both baseline and advanced W materialsdeveloped recently.

4. Neutron irradiation response of Cu-based materials are severe for long termoperation of DEMO. Drastic modification or alternative materials are required.

5. Fusion-relevant neutron sources are necessary to confirm the response tothe 14 MeV neutron irradiation.

shuhei nogami tohoku university, japan 3/2. nogami.pdfembrittlement low temperature brittleness....

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