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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
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
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:
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
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
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
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
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
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
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
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
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
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
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
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
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