self-passivating smart tungsten alloys as an intrinsic ... meeting... · a. litnovsky et al., smart...
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A. Litnovsky et al., Smart alloys, First IAEA TM on the Safety, Design and Technology of Fusion Power Plants, Vienna, Austria, May 3-5, 2016
Self-passivating smart tungsten alloys as an intrinsic safety for the future fusion
power plant
A. Litnovsky, T. Wegener, F. Klein, Ch. Linsmeier, M. Rasinski and J.W. Coenen
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Slide 2 of 15A. Litnovsky et al., Smart alloys, First IAEA TM on the Safety, Design and Technology of Fusion Power Plants, Vienna, Austria, May 3‐5, 2016
0 20 40 60 80 100Time, days
Temperature*,oC
200
400
600
800
1000
1200
Motivation
*Final Report of the European Fusion Power Plant Conceptual Study, EFDA RP-RE 5.0, 2005
Conceptual study of the fusion power plant
Mobilization of radioactive elements must be prevented
Accidental loss of coolant:
peak temperatures of first wall
up to 1200 °C due to nuclear decay heat
Additional air ingress: formation of highly
volatile WO3 (Re, Os)
>1000°C in a reactor
1000 m2 surface
Evaporation rate: 10 -100 kg/h
Radioactive WO3 may leave hot vessel
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A. Litnovsky et al., Smart alloys, First IAEA TM on the Safety, Design and Technology of Fusion Power Plants, Vienna, Austria, May 3-5, 2016 Slide 3 of 15
Intrinsic safety
Picture is the courtesy of DIFFER NL
Intrinsic safety is the most reliable measure
No immediate access to water and/or coolant No electricity Difficult logistics Lack of manpower
In case of major accident:
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A. Litnovsky et al., Smart alloys, First IAEA TM on the Safety, Design and Technology of Fusion Power Plants, Vienna, Austria, May 3-5, 2016 Slide 4 of 15
Smart tungsten alloysAdjust their properties to the environment conditions1
Normal operation (730°C->550°C2):Formation of tungsten surface bydepletion of alloying element(s)
due to preferential sputtering by plasma
structural material
W & alloying element(s)
Tungsten
Accidental conditions:(air ingress, up to 1200°C)
Formation of protective barrier layer
Tungsten-based “smart” alloys
Behave like tungsten during plasma operation
Suppress oxidation during accident
structural material
W & alloying element(s)
Protective layer
PlasmaAtmosphere
2Yu. Igitkhanov et all, Design Strategy for the PFC in DEMO Reactor, Report-Nr. KIT-SR 7637.
1F. Koch and H. Bolt, Phys. Scr. 128(2007)100
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A. Litnovsky et al., Smart alloys, First IAEA TM on the Safety, Design and Technology of Fusion Power Plants, Vienna, Austria, May 3-5, 2016 Slide 5 of 15
Choice of alloying elements
+ Low volume increase by oxidation
Good adhesion of the oxide to the alloy
High melting point of alloys and oxides
Cr, Ti, Mn, Y
Requirements Low neutron activation
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A. Litnovsky et al., Smart alloys, First IAEA TM on the Safety, Design and Technology of Fusion Power Plants, Vienna, Austria, May 3-5, 2016 Slide 6 of 15
Yttrium as an active element
[1] K. Przybylski, A. J. Garratt-Reed, and G. J. Yurek. Grain boundary segregation of yttrium in chromia scales. Journal of The Electrochemical Society, 135(2):509517, 1988.
[2] M.F. Stroosnijder, et al. The inuence of yttrium ion implantation on the oxidation behaviour of powder metallurgically produced chromium. Surface and Coatings Technology, 83:205 211, 1996. 9th International Conference on Surface Modication of Metals by Ion Beams.
[3] N. Birks, G.H. Meier, and F.S. Pettit, Introduction to the High-Temperature Oxidation of Metals. Cambridge University Press, 2006.[4] R. Buergel, H. J. Maier, and T. Niendorf. Handbuch Hochtemperatur-Werkstofftechnik. PRAXIS, 2011[5] I. A. Kvernes, The Role of Yttrium in High-Temperature Oxidation Behaviour of Ni-Cr-Al Alloys, Oxidation of Metals, Vol. 6, No. 1, 1973
Y at the grain boundaries1,2
Y at the oxide-alloy interface2,3
Reactivity towards impurities3
Smaller grains1,3,4
Thinner oxide layer
Oxidation pegs, good adhesion1,3,4
Oxidation inwards to the surface3
Less pores5
More stable oxide
Y
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A. Litnovsky et al., Smart alloys, First IAEA TM on the Safety, Design and Technology of Fusion Power Plants, Vienna, Austria, May 3-5, 2016 Slide 7 of 15
High temperature oxidation: tungsten vs. smart alloys
Best passivation behavior of W-Cr-Y alloy
0 20 40 60 80 100 1200,0
0,1
0,2
2,0
2,51000oCW: Oxidation and evaporation
W-Cr-Y:• Even lower oxidation rate • No delamination/evaporation
W-Cr-Ti:Performance improvementW-Cr:
• Reduced oxidation rate • Delamination after 15´
Mass change, mg/cm2
Exposure time, min.
Oxidation constants:
W:
0.52
W-Cr-Y:
3*10-6
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A. Litnovsky et al., Smart alloys, First IAEA TM on the Safety, Design and Technology of Fusion Power Plants, Vienna, Austria, May 3-5, 2016 Slide 8 of 15
Structure of protective layer
W-Cr W-Cr-Y
Smooth thin oxide layer in W-Cr-Y
No visible pores
Pores
Cr2O3
Cr2WO6
Internal oxidation
80 vol.% Ar + 20 vol.% O2 1 bar 1000oC 15’
No W-containing oxides
Suppressed internal oxidation
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A. Litnovsky et al., Smart alloys, First IAEA TM on the Safety, Design and Technology of Fusion Power Plants, Vienna, Austria, May 3-5, 2016 Slide 9 of 15
High temperature oxidation of smart alloys: first results
Oxidation time, minutes
W-Cr fails
Mass change, mg2*cm-4
W-Cr-Y oxidizes faster
at 1200oC
Still parabolic behavior of W-Cr-Y after 15 minutes@1200oC
1000oC and 1200oC
4 6 8 10 12 140,00
0,05
0,10
0,15
0,20 W-Cr W-Cr-Y@1200C W-Cr-Y@1000C
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A. Litnovsky et al., Smart alloys, First IAEA TM on the Safety, Design and Technology of Fusion Power Plants, Vienna, Austria, May 3-5, 2016 Slide 10 of 15
Oxidation in steam and humid air
W oxidizes immediately
W remains rather inert in humid argon
Smart alloy reacts with water No water cooling in DEMO?
No pure tungsten in DEMO?
0 20 40 60 80 1000,0
0,1
0,2
0,8
1,0
W in humid air W with steam Smart alloy in humid air Smart alloy with steam
Exposure time, min.
Mass change, mg/cm2
Pure W vs.
W-Cr-Y smart alloy
Steam:Ar + 70%
humidity@40oC
Humid air:80 vol.% Ar
+ 20% vol.% O2+70% humidity
@40oC
Exposure at 1000oC, 1 bar
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A. Litnovsky et al., Smart alloys, First IAEA TM on the Safety, Design and Technology of Fusion Power Plants, Vienna, Austria, May 3-5, 2016 Slide 11 of 15
Smart alloys: future challenges
Technology
Smart alloys
Mechanical properties
Plasma performance*
Engineering constraints
Other safety interfaces
* A. Litnovsky et al., "Smart alloys for a future fusion power plant: first studies under stationary plasma load and in accidental conditions“, 22nd PSI, Rome, Italy, May 30 - June 3, 2016
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A. Litnovsky et al., Smart alloys, First IAEA TM on the Safety, Design and Technology of Fusion Power Plants, Vienna, Austria, May 3-5, 2016 Slide 12 of 15
Safety interfaces: examples
Power plant integrity Reliability of structural elements Stability of PFCs
This presentationCorrosion of coolant pipes3
In-vessel and
ex-vessel LOCA in DEMO1,2
Possible hazards Tritium in VV and in coolant W-dust Activated corrosion products Volatile radioactive rests of PFCs
Joint effort required
[1] M. Nakano et al., Fus. Eng. And Design 89 (2014) 2028[2] M. Nakano et al., Nucl. Fus. 55 (2015) 123008[3] S. Wikman et al. 25 IAEA FEC St. Petersburg, 2014 MPT/P4-23
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A. Litnovsky et al., Smart alloys, First IAEA TM on the Safety, Design and Technology of Fusion Power Plants, Vienna, Austria, May 3-5, 2016 Slide 13 of 15
Summary
New advanced materials are required for future power plant
Safety aspect is of prime importance
Tungsten-based smart alloys: a promising combination
of intrinsic safety and plasma performance
Further qualification is underway
First results are encouraging:
Suppressed oxidation of tungsten
Stability of smart alloy system
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A. Litnovsky et al., Smart alloys, First IAEA TM on the Safety, Design and Technology of Fusion Power Plants, Vienna, Austria, May 3-5, 2016 Slide 14 of 15
Outlook
Manufacture of bulk samples
Tests of plasma performance
Mechanical properties: optimization
Implementation of advanced technologies: Wf/W
Working on safety interfaces
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A. Litnovsky et al., Smart alloys, First IAEA TM on the Safety, Design and Technology of Fusion Power Plants, Vienna, Austria, May 3-5, 2016 Slide 15 of 15
Thank you