simulating fusion neutron damage using protons in ods steels jack haley
TRANSCRIPT
1. Fusion Power and radiation damage
2. Simulating neutron damage
3. Simulating with protons
4. Project plan
Fusion Power
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• Deuterium and Tritium fuse to produce a 3.5MeV alpha particle and 14.1MeV neutron
• Neutrons cause hardening, embrittlement and swelling in components.
• Enormous demands placed on the structural steels
• ODS steels are excellent at handling the radiation
• ODS precipitates pin dislocations and act as sinks for defects and Helium [1]
Fusion Power
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[1] Brodrick, J., Hepburn, D. J., & Ackland, G. J. (2014). Mechanism for radiation damage resistance in yttrium oxide dispersion strengthened steels. Journal of Nuclear Materials, 445(1-3), 291–297. doi:10.1016/j.jnucmat.2013.10.045
Simulating the neutrons
• Closest thing to fusion neutrons available fission neutronsLower energy (~2MeV)Takes a long timeMakes samples radioactive
• Self ion irradiation is widely used High dose rateMany facilities available, eg JANNUS, MIAMIMulti beam energiesIn situ with TEM, Helium implantation
• Self ions irradiation behave like the primary knock on atom in neutron irradiation
Fission neutron PKA up to 200keV
Fusion neutron PKA up to 1MeV [2]
[2] Dierckx, R. (1987). The importance of the pka-energy for damage simulation spectrum. Journal of Nuclear Materials, 144, 214–227.
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Simulating with self-ions
-0.10 0.10 0.30 0.50 0.70 0.90 1.10 1.30 1.50
SRIM damage calculation as a function of depth in Fe
Depth (μm)
Dos
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2.9MeV Fe ions @ 2.2nA
Simulating with self-ions
Size effect in micromechanical testing
• As sample size decreases, yield strength increases
[3] Taken from Chris Hardie’s Dphil thesis, 2012Oxford University
Fe-6Cr
[3]
Simulating with protons
0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00
SRIM damage calculation as a function of depth in Fe
Depth (μm)
Dos
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Smooth Damage Re-gion
2.9MeV protons @ 100μA
Simulating with protons
• Higher dose rate than neutrons, but much lower than heavy ions – need higher currents
• Very different recoil energy (PKA <0.5keV) than fusion neutrons
Simulating with protons
• Dominant energy loss mechanism of proton is by ionization
• May be a problem with ODS steels – oxide precipitates could be degraded due to the ionization
0.0E+00 2.0E+03 4.0E+03 6.0E+03 8.0E+03 1.0E+04 1.2E+04 1.4E+041.0E-06
1.0E-04
1.0E-02
1.0E+00
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Energy Loss of 2.9MeV Fe ions in Fe
Energy Loss by Ionization
Energy Loss by Phonons
Depth (Ang)
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Ang
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0.00E+00 1.00E+05 2.00E+05 3.00E+05 4.00E+051.0E+00
1.0E+02
Energy Loss of 2.9MeV protons in Fe
Energy Loss by Ionization
Energy Loss by Phonons
Depth (Ang)
Ener
gy L
oss (
eV/A
ng/I
on)
• Gary Was et al – Emulation of neutron irradiation effects with protons: Validation of principle [4]
2002 paper studied:
Radiation Induced Segregation Microstructure (dislocation loops) Irradiation hardening Susceptibility to IASCC
Found excellent agreement between fission neutrons irradiated at 275oC and 3.2MeV protons at 360oC
• Higher temperature proton irradiation balances the increased displacement rate by enhancing diffusion kinetics.
[4] Was, G. S. et. Al. (2002). Emulation of neutron irradiation effects with protons : validation of principle, 300, 198–216.
Protons in the literature
• Still no proton studies on martensitic FeCr and ODS steel
• Recoil energy influence on the radiation induced damage is dependent on
Composition Irradiation temperature Lattice structure
• There is no magic formula (yet!) for determining appropriate proton irradiation conditions to reliably mimic neutron damage
Simulating with protons
• University of Birmingham has two particle accelerators available for proton irradiation of materials
Simulating with protons
Accelerator facilities are housed in the Medical Physics Building
at the University
Image Copyright Phil Champion. This work is licensed under the Creative Commons Attribution-Share Alike 2.0 Generic Licence. To view a copy of this licence, visit http://creativecommons.org/licenses/by-sa/2.0/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.
Cyclotron1-9MeV protons – 2.9MeV preferred set up~10μA beam current up to 2cm diameter beam sizeCapable of ~10-6 dpa/s in Iron which translates as ~0.05
dpa/dayTemperature control up to 600oC available now
Dynamitron 1-3MeV protons100s of μA beam current easily possible, absolute
maximum 2mAUp to 2cm diameter beam size
~10-5 - 10-4 dpa/s~1 dpa/day at 100 μA Temperature control in the works
Project plan
Key questions:
• How is the microstructural damage produced by proton, heavy ion and fission neutrons different?
• What are the differences in mechanical properties?
• Is the proton damage representative of neutron damage under any irradiation conditions?
Project plan
Next Steps
• Start work initially on FeCr binary alloys 0-15% Cr content
• ODS steels later
• Heavy ion irradiation at JANNUS in May
• Use Cyclotron in the summer for first proton irradiations, up to 0.6dpa to match neutron specimens at CCFE at same temperature
• Once Dynamitron is ready, use to irradiate at higher doses