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Y. Nagai 1 , A. Kuramoto 1 , T. Toyama 1 , T. Takeuchi 2 , M. Hasegawa 3

PPC-10 Smolenice Castle, Slovakia Sept. 5 - 9, 2011. Positron annihilation study of neutron-irradiated nuclear reactor pressure vessel (RPV) steels and their model alloys. Y. Nagai 1 , A. Kuramoto 1 , T. Toyama 1 , T. Takeuchi 2 , M. Hasegawa 3

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Y. Nagai 1 , A. Kuramoto 1 , T. Toyama 1 , T. Takeuchi 2 , M. Hasegawa 3

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  1. PPC-10 Smolenice Castle, Slovakia Sept. 5 - 9, 2011 Positron annihilation study of neutron-irradiated nuclear reactor pressure vessel (RPV) steels and their model alloys Y. Nagai1, A. Kuramoto1, T. Toyama1, T. Takeuchi2, M. Hasegawa3 1The OaraiCenter,Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313, Japan 2Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan 3Institute for Materials Research, Tohoku University, Sendai, Miyagi 980-8577, Japan hasegawa@imr.tohoku.ac.jp

  2. Outline 1) Backｇround 2) Fe-Cu Model Alloys: Cu Nano-Clusters (Precipitates) a) Size: 2D-ACAR Momentum Smearing b) Number Density: AMOC 3) RPV Steel: Surveillance Test SpecimenMaterials Mechnisms: Nanostructural Features Irradiation Embrittlement & Hardening 1st & 2nd Generation A533B Post Irradiation Annealing (PIA) Experiments

  3. Nuclear Reactor Pressure Vessel (RPV) Steel Origin of irradiation-induced embrittlement 1) Solute Nano-Clusters 2) Matrix Defects (vacancy-type defects, dislocation loops, ···) dislocation Grain boundary 3) P Segregation at Grain Boundary

  4. Laser-Assisted Local Electrode Atom Probe Position sensitive ion detector Z Y X Local electrode Laser Vtotal Needle sample Vextraction ～100nm Time of Flight Mass 4 Energy-compensated type (with “Reflectron”)

  5. Positron Quantum-Dot Confinement in a Precipitate of 59 Cu Atoms LEAP 3D-Atom Probe 2x107 Atoms,1hour e+Self-Searching: Cu Nano-Particlesin Fe 1nm Density isosurface ofa quantum-dot confined positron in a Cu59 in Fe matrix. The isodensity value is 0.5% of the maximum. 60x60x170 nm

  6. 2a) Cu Nano-Precipitates (Clusters) : Size2D-ACAR: Momentum Smearing Z. Tang et al.: J. Phys.: Condens. Matter 20 (2008) 445203, Size-dependent momentum smearing effect of positron annihilation radiation in embedded nano Cu clusters

  7. 2b) Cu Nano-Precipitates (Clusters) : Number DensityAMOC: Time Evolution of HMCF (W-Parameter) Trapping Model A. Inoue et al.: Phys. Rev. B83 (2011) 115459

  8. Fe-0.88at.%Cu: Thermal Aging @550˚C 0.1h CDB Ratio Curve 3D-AP 0.2h 2h 10nm 30nm 2h: Complete e+ Quantum-Dot Confinement Fig.1

  9. Time Evolution of CDB HMCF (W-Parameter) Pure Cu Pure Fe

  10. Positron Age-Momentum Correlation(AMOC) Using digital oscilloscope：Time resolution ~170ps Number density estimated by positron annihilation Time dependent HMCF　（W-parameter) Positron trapping rate Number density Aging Time (h) Number Density (×1017 cm-3) Size Diameter (nm) 3D-AP e+ 0.1 0.61 0.15 0.9 1.2 1.4 0.2 1.1 2.5 1.8 1.9 2

  11. 3) RPV Steel: Surveillance Test SpecimenMaterials1St & 2nd Generation A533B Irradiation –Induced Embrittlement (Hardening) MechanismsPost Irradiation Annealing (PIA) Experiments PIA: 1st Gen A533B Kuramoto et al.: Submitted to J. Nucl. Mater. Fluence Dependence Takeuchi et al. : J. Nucl. Mater. 402 (2010) 93.

  12. A533B P S C Si Mn Mo Cu Cr Ni 0.19 0.30 1.30 0.53 0.17 0.68 0.015 1st. Gen. 0.16 0.010 2nd. Gen. 0.001 0.004 0.19 0.19 1.43 0.50 0.13 0.65 0.04 Reactor Pressure Vessel (RPV) Steel: A533B Chemical Composition wt.% Purified: Cu, P, S JMTR Irradiation Fluence: 3.9x1019n/cm2 (0.061dpa) Flux: 1.8x1013n/cm2・sec Temperature: 2902C

  13. Annealing Behavior of Average Positron Lifetime 1st. Gen.(0.16Cu)&2nd.Gen.(0.04Cu) A533B, 3.9×1019 n/cm2 180 V 1 st. 1 Gen. (0.16Cu) nd. 160 2 Gen. (0.04Cu) Positron Lifetime [ps] Average 140 • Unirrad. (2nd. Gen.) • Unirrad. (1st. Gen.) 120 Fe bulk 100 200 300 400 500 600 Annealing Temperature [ ] ℃ As-irrad.

  14. CDB HMCF-LMCF Correlations 1st. Gen. (0.16Cu) &2nd. Gen. (0.04Cu) A533B,3.9×1019 n/cm2 450 °C 400 °C 300 °C As-irrad. (1st. Gen. ) 550 °C Unirrad. (1st. Gen. ) 600 °C As-irrad. (2nd. Gen. ) 600 °C Unirrad. (2nd. Gen. ) 450 °C 300 °C

  15. 0.014 0.012 0.01 HMCF 0.008 0.006 0.004 0.5 0.55 0.6 0.65 LMCF Neutron Irradiation: 8.3×1018n/cm2 (1.2×10-2dpa, ~100ºC) Fe-Cu Model Alloys ( 0.3wt.%Cu, 0.05wt.%Cu ) Pure Cu 500 0.3Cu 500 0.05Cu As-irrad. Pure Fe Unirrad. Unirrad. As-irrad.

  16. Atom Maps of the Solutes: Annealing Behavior (As-irrad.~400℃) 1st. Gen. (0.16Cu) A533B, 3.9×1019n/cm2 As-irrad. 350 °C 400 °C Cu Si Mn P Ni 10nm

  17. Atom Maps of the Solutes: Annealing Behavior (As-irrad.~350 ℃) 2nd.Gen. (0.04Cu) A533B, 3.9×1019n/cm2 As-irrad. 300 ℃ 350 ℃ Si Mn Ni P Cu 10nm

  18. Average Chemical Compositions of Solute Clusters 3.9×1019n/cm2 1st. Gen. (0.16Cu) A533B 2nd. Gen. (0.04Cu) A533B Cu Mn Si Composition [%] Ni Composition [%] Fe Annealing Temperature [°C] Annealing Temperature [°C]

  19. Radius of Gyration (rg), Number Density (Nd) & Volume Fraction (Vf) A533B, 3.9×1019 n/cm2 rg Radius of Gyration 1st. Gen.(0.16Cu) CuMnSiNi Clusters 1st. Gen. 2nd. Gen. (0.04Cu) MnSiNi Clusters Nd Number Density 2nd. Gen. Hardening Russell-Brown Model Vf Volume Fraction

  20. Annealing Behavior of Irradiation Hardening (∆Hv) 1st.Gen. (0.16Cu) A533B, 3.9×1019 n/cm2 e+ : Vac-Defects 3D-AP:CuMnSiNi Clusters As-irrad.

  21. Av 1st. Gen. (0.16Cu) 2nd. Gen. (0.04Cu) 3.9×1019n/cm2 LMCF HMCF Hv As-irrad. Annealing Temperature [°C]

  22. What & How Positron Annihilation Can Say on RPV-EmbrittlementMechnisms ? Unique Nano-Features 1) Cu-Rich Nano-Clusters Evolution, Recovery: Clear-Cut Info. Size, Number Density: Not Easy 2) Vacancy-Related Defects Correlation: Mech. Properties Integration: Other Methods, such as 3D-AP, SANS,TEM Quantative !!

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