TECHNOLOGICAL DRIVERS & OPERATIONAL WINDOW OF AN … Meeting... · Armor material Material...
Transcript of TECHNOLOGICAL DRIVERS & OPERATIONAL WINDOW OF AN … Meeting... · Armor material Material...
TECHNOLOGICAL DRIVERS & OPERATIONAL WINDOW OF AN ACTIVELY COOLED DIVERTOR
SEPTEMBER 2015
First IAEA Technical Meeting on Divertor Concepts | Mehdi Firdaouss
| PAGE 1CEA | 10 AVRIL 2012
OUTLINE
Introduction Physics requirements General material requirements
Present water cooled divertor Water cooled divertor concepts Limits of the main concept Integration issues Industrialization issues
Summary
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ITER-GRADE DIVERTOR: TECHNOLOGICAL REQUIREMENTS COME FROM PLASMA PHYSICS
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Main role of the divertor is to sustain power coming from the plasma: Steady state: 10MW/m² Slow transient: 20MW/M² ELMS/disruptions
Other requirements come also from this interaction with the plasma Sputtering cause by particles impact Misalignment due to low incidence angle
These requirements coming from the plasma physics have a direct effect on the divertor concepts
Thermal properties
Erosion sensitivity & thicknessMachinability
MATERIAL REQUIREMENTS FOR ACTIVELY COOLED ITER-GRADE DIVERTOR
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No single material can endorse the three roles -> need for an assembly
Armor materialMaterial properties• high melting temperature • good bonding
characteristics• high thermal conductivity• resilience to thermal shock • machinability
Vacuum and plasma compatibility• low tritium retention• low chemical and
sputtering erosion• low hydrogen
embrittlement• low affinity to hydrogen /
oxygen• low plasma perturbation
Heat sink materialMaterial properties• compatibility with water
cooling• low corrosion• high thermal conductivity• low electric conductivity• good bonding
characteristics
Structural materialMaterial properties• high mechanical properties• low electric conductivity• availability
EXAMPLE OF THE HEAT SINK MATERIAL REQUIREMENTS
A simple 1D thermo-mechanical model is used to sort different material heat removal capability
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Li-Puma et al., Fus. Eng. Des. 88 (2013) 1836-1843
* heat removal capability = heat flux density * thickness
Operating temperatures ranges also indicated for Cu alloys and Eurofer Lower limit is the DBTT of the material Max limit is strength loss due to thermal softening, overaging and irradiation creep (in
particular for CuCrZr) Temperature of the coolant has also to be limited to keep margin to the critical heat flux
WATER COOLED DIVERTOR CONCEPTS
Best compromise: W as plasma facing material CuCrZr as heat sink material 316L IG as structural material
Three main concepts, showing the trade-off between W thickness and erosion / surface temperature:
Coating W Compatible with any shape of PFC Very sensitive to erosion
Flat tile / EAST Good bonding
Monoblock / ITER / EAST / WEST Minimization of the CuCrZr quantitiy
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Technology difficultyPerform
ancesD
esign constrains
THERMAL PERFORMANCE OF THE MONOBLOCK: PRESENT STATUS
Considering the requirements (in particular with 8mm W thickness), the geometry is optimized as its best in terms of manufacturability and thermal lifetime
From the HHF tests on different supplier (from Europe, China, Japan…) 10 MW/m² is achievable At 15MW/m² surface modification without loosing the power
handling capabilities The 20 MW/m² limit is more challenging, as a macro crack (“self-
castellation”) appears for some of the tested monoblocks
However synergistic effects (impact of transients and plasma wall interactions) might decrease these operational limits.
Lower mechanical stress and therefore better thermal lifetime may only come with changing requirements (W thickness) and/or material (cooling tube / compliance layer / W alloy)
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W thickness8mm
M. Merola et al., Fus. Eng. Des. 2015
INTEGRATION BRINGS ADDITIONAL CONSTRAINS
The PFC has to be connected to the water cooling circuit an heterogeneous bonding between CuCrZr and Stainless steel has to be done (generally by electron beam welding).
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10mm
~0.3mm grainsize
> 1mm grainsize
Specifity of ITER/DEMO: Need of having inspectable welding (including in service) Wide use of remote handling Maintenance will have to be done in a harsh environment
In order to avoid creating leading edges (gaps, grazing incidence angle), assembly tolerances are very strict (±0.3mm in some case), which lead to demanding manufacturing tolerances ( down to ±0.1mm )
TPL of Tore SupraFlat-Tile concept with CFC-armoured
Divertor of W7-X Flat-Tile concept with CFC-armoured
622 Fingers, ~13000 tiles 890 Targets , ~18000 tiles
TOWARDS THE INDUSTRIALIZATION: CLOSE LINK WITH INDUSTRY REQUIRED
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Examples of a manufacturing of water cooled PFC
Series Expected Realized Modification
TPL 6 batches / 4 years 6 batches / 5 years Acceptance criteriarelaxed after 3 batches
Divertor W7-X 6 batches / 4 years Pre-series 60 fingers / 4 years6 batches / 5 years
Re-validation of the process
For divertor manufacturing, technological difficulty is associated with a small market. Industrial involvement is required. Coming from past experience, a close work with Industry is required to improve this involvement and decrease the risks of delay / failure.
WEST: A PROJECT IN SUPPORT TO THE ITER DIVERTOR
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ITER DivertorTechnology
WEST vs ITER
Monoblockgeometry and shape Identical
Assembling technology Identical
Thermal hydraulic conditions Identical
Test of scale 1 target (~14% monoblockstotal ) in a tokamak with relevant heat loads under plasma conditions.Test the industrialization capabilities of several supplier, in close link with the DAs in charge of procuring the ITER divertor targets (EU, Japan).WEST will benefit to both industrial and DA toward the success of ITER
More than 1E5 individual monoblocks to be manufactured and assembled (rejection rates of the process around 5% as of now)
Testing 100% of the PFC has a strong impact on cost and delay
DEVELOPMENT OF QUALIFICATION AND CONTROL FACILITIES
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M. Missirlian et al., proceedings of ISFNT-12
Optimization of the qualification tests and reception controls to be used is required US tests for bonding inspection Hot He leak test HHF test Non destructive thermal tests
A consequence to this approach is the need to have access to repairing process
SUMMARY
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ITER-grade divertor requirements can be reached with the W monoblock concept in its present prototype state with a good level of thermal performance
However, challenging issues remains on several aspects: Integration of the individual components Large scale industrialization
From the past experience, it is necessary to work in close link with Industry to optimize the manufacturing process as well as the test and control processes.
The operational window of the ITER-grade divertor is well qualified at lab-scale, and only few optimization can be expected. DEMO will bring additional constraints mainly due to nuclear environment. The use of an ITER-grade Cu-W monoblock at the same operational windows seems very challenging.
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SPARE SLIDES
OPERATING TEMPERATURE RANGE – DEMO AND BEYOND
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S.J. Zinkle & J.T. Busby, Mater. Today 12 (2009) 12-19
KNOWLEDGE DATABASE REQUIREMENT – DEMO AND BEYOND
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Data base need <20 dpa ~50 dpa >100 dpa
Mater
ials
RAFM
FM-O
DSW Si
CBe Li
cera
mic
RAFM
FM-O
DSW Si
CBe Li
cera
mic
RAFM
FM-O
DSW Si
CBe Li
cera
mic
Irradiation effectsHardening/EmbrittlementPhase stabilitiesCreep & fatigueVolumetric swellingHigh T He & H effects
Adv. DEMO2nd DEMO Blanket1st DEMO Blanket
Adequate knowledge base existsPartial knowledge base existsNo knowledge base
Note: He levels are only for FM steels
Complimentary: R. Kurtz, PNNLA. Möslang, KIT
EFFECTS ON MATERIAL UNDER NEUTRON IRRADIATION – DEMO AND BEYOND
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Neutron irradiation affecting Consequences on plasma-material interaction
Thermal conductivity Temperature operation window, less tolerance to transient heat loads, erosion yield
Chemical composition (transmutation) Hydrogen retention, thermal conductivity indirectly
Interstitials, vacancies, dislocations, voids Hydrogen retention
Swelling and irradiation creep at intermediate temperatures
Tolerance in PFC alignment will become larger, hence power handling capability lower
Loss of high-temperature creep strength Reduced temperature operation window
Ductile to Brittle Transition Temperature Reduced temperature operation window
He, H embrittlement Erosion and dust production will be enhanced
Under neutron irradiation, the temperature operation window will reduce, retention and erosion will increase
CU ALLOYS UNDER NEUTRONS – DEMO AND BEYOND
Neutron irradiation causes hardening andloss of elongation
Other properties also degrades quickly withneutrons, although stabilization seems toappear at ~10dpa
It could be replaced by a RAFM steel, likeEurofer, with a strong impact on theacceptable temperature range and also themaximal heat flux (<10MW/m²).
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M. Li et al., J. Nucl. Mater. 393 (2009) 36
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CEA | 10 AVRIL 2012