First Principles Modeling on
Radiation Defects in W and Wbased Alloys
T. Suzudo1, T. Tsuru1,2
1Japan Atomic Energy Agency
2Kyoto University

Application of tungsten tonuclear fusion reactor
 High melting point High resistance to spattering Low hydrogen absorption

BlanketDiverter Block

Armoring of plasma facing materials
June 18-20, 2019, MoD-PMI 2019, Toki

CoolingIrradiation to fusionmaterials is severe
High-energy particle

Molecular dynamics byLAMMPS (BCC Fe)

Operational condition of materials in various
nuclear devices (IAEA GC51)

June 18-20, 2019, MoD-PMI 2019, TokiNeutron irradiation to W causes Re(and Os) through nuclear transmutation

Nuclear reaction of W under neutron irradiation

Pure W

W-6Re-3Os (end-of-service)
Cottrrel et al., Fusion Sci. Technol. 50(2006) 89.
June 18-20, 2019, MoD-PMI 2019, TokiRe causes radiation-induced
precipitation in W
W-Re phase diagram [1]Neutron-irradiated W-5Re 1.54dpa,
750℃ [2]BCC

Re in W (%)
Solubility limit of Re > 20%

Plate-like or needle-like
precipitates (χ-phase, Re3W)[1] Williams et al., Metallurgical Trans. A , 14A 655-666(1983)[2] Tanno et al., Mater. Trans. 49[10], 2259-2264(2008)
June 18-20, 2019, MoD-PMI 2019, Toki

Re in W reduce radiationinduced void swelling
Neutron irradiation
9.5 dpa, @EBR-II [1]Neutron irradiation
1.54dpa, 750℃@JOYO [2]WW-25Re[1] J. Matolich et al, Scr. Metall. 8 (1974) 837-841.
[2] T. Tanno et al., Mater. Trans. 49 (2008) 2259-2264.
June 18-20, 2019, MoD-PMI 2019, Toki

Goal of this study is :To explain the experimentally-discovered
Re-effects using the first-principles
calculations

June 18-20, 2019, MoD-PMI 2019, Toki

Modeling methodology
VASP（Vienna ab initio
Simulation Package）
Projected augmented wave
potential (PAW/PBE)
5a0×5a0×5a0 (250 lattice sites)super cellK-point (3×3×3)
Cutoff energy: 350eV
Nudged elastic band method to
calculate migration barrier
June 18-20, 2019, MoD-PMI 2019, Toki

Used super cellDisplaced W forms W-Re dumbbell,
which migrate and rotate
Eb=0.8 eV→+Eｍ=0.12 eV→

W-Re dumbbell can rotate easily
Er=0.03 eV<111><110><111>→T. Suzudo, M. Yamaguchi, A. Hasegawa, Modeling Simulation
Mater. Sci. Eng. 22 (2014) 075006.
June 18-20, 2019, MoD-PMI 2019, Toki

9

KMC simulation (PAKSS) of 1D
SIA and 3D W-Re dumbbell
SIA (1D)
Production bias
W-Re (3D)
SIAvacancy

Mixeddumbbell

Our results suggest:
 SIA (1D migration)→ Accumulation of vacancies
 Mixed (3D migration)→ Enhanced recombination to vacancy→ Suppression of radiation swelling
T. Suzudo, A. Hasegawa, Scientific Reports vol. 6, 36738 (2016).
June 18-20, 2019, MoD-PMI 2019, TokiEnhanced recombination also
explains the precipitation.
Binding energy

ReVacancy(eV)

SIA (eV)

0.22

0.79

Re atoms are dragged by vacancy and SIA
and aggregated through recombination.
SIA

Vacancy and SIA bind Re‘n’ irradiation
Vacancyβ decay Re

Our recombination scenario explains both radiation-induced
precipitation and suppression of swelling.
June 18-20, 2019, MoD-PMI 2019, Toki

Binding energy for othersolute atoms are calculated
Binding energy of solute elements and SIA/vacancy

June 18-20, 2019, MoD-PMI 2019, Toki

Ti, V, and Cr form mixed-dumbbells,
but not solute-vacancy complex
Binding energy of solute elements and SIA/vacancy

SIAVacancy

Recombination does notcause aggregation

June 18-20, 2019, MoD-PMI 2019, Toki

W-Ti, W-V, W-Cr dumbbells also
Have 3D motion<11h> dumbbell is the most favorable
The rotation is easy.

Migration energy ofmixed dumbbell

<111>

<111>

Em

<111>

<11h>

<11h>

<110>

<110>

<110>
Em=0.15 eV for Ti=0.13 eV for V=0.12 eV for CrT. Suzudo, T. Tsuru, A. Hasegawa, J. Nucl. Mater. 505 (2018) 15-21
June 18-20, 2019, MoD-PMI 2019, Toki

Summary DFT study predicts 3D migration of W-Re mixed
dumbbell, this seems a cause of swelling
suppression and radiation-induced precipitation.
 Ti, V, Cr may suppress radiation effect withoutcausing precipitate, but experimental verificationis required.

June 18-20, 2019, MoD-PMI 2019, Toki