Understanding on the Mechanisms of Irradiation Embrittlement of RPV Steels and Development of Embrittlement Correlation Method

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1 IAEA Training Workshop on Assessment of Degradation Mechanisms of Primary Components in Water Cooled Nuclear Reactors: Current Issues and Future Challenges Understanding on the Mechanisms of Irradiation Embrittlement of RPV Steels and Development of Embrittlement Correlation Method Akiyoshi Nomoto Central Research Institute of Electric Power Industry (CRIEPI) 1

2 Embrittlement Mechanism : General Consensus Formation of Cu-enriched clusters (CEC, CRP) in Cu-containing materials Cu core associated with Ni, Mn and Si 2~3 nm in diameter obstacle to dislocation motion dose rate effect exists Formation of matrix damage (MD) point defect clusters such as dislocation loops or vacancy clusters, or point defect solute atom complexes. main contributor to the embrittlement of low Cu materials P MD CEC Cu Dislocation G.B. Phosphorus segregation on grain boundary P segregation weakens grain boundaries. 2

3 Outline Part I Irradiation-induced features that cause embrittlement Effect of solute element Effect of temperature Effect of neutron fluence Effect of neutron flux Part II Embrittlement correlation methods Development of Japanese embrittlement correlation Known unknows and unknown unknows 3

4 Outline Part I Irradiation-induced features that cause embrittlement Effect of solute element Effect of temperature Effect of neutron fluence Effect of neutron flux Part II Embrittlement correlation methods Development of Japanese embrittlement correlation Known unknows and unknown unknows 4

5 APT characterization of irradiated RPV steel High impurity (Cu) weld metal irradiated to high fluence Cu P Si 232nm EW-P2 R : 30x29x232 nm 3, 6.4M atoms 30nm Clusters consist of Cu, Ni, Mn, Si and P. Cu atoms are at the center. Ni, Mn and Si atoms are around the Cu core, and P atoms are at the periphery. 5

6 Nature of Cu-enriched clusters High Cu steel 0.12Cu, 4x10 19 n/cm 2, E>1MeV Cu-Ni-Si-Mn cluster High Cu steel0.12cu, 4x10 19 n/cm 2, E>1MeV 35 x 41 x 491 nm 3 :13.7M atoms Medium Cu steel 0.07Cu, 6x10 19 n/cm 2, E>1MeV Cu P Si 33 x 38 x 284 nm 3 : 8.1M atoms Low Cu steel 0.03Cu, 6x10 19 n/cm 2, E>1MeV 41 x 49 x 264 nm 3 : 11.2M atoms Ni-Si-Mn cluster 6

7 Contribution of SC to embrittlement RT NDT ( o C) T41J RT NDT ( o C) NDT ( o C) V f 1/2 Surveillance data (N. Soneda et al. CRIEPI Q06019, 2007) V f 1/2 V f 1/2 V f 1/2 MTR irradiated data (JNES PRE Project, N. Soneda et al. JAI , 2009.) Transition temperature shift is almost proportional to V f 1/2 of solute atom clusters. This relationship between RT NDT and V 1/2 f is independent of chemical compositions of the clusters. Slight difference in the slopes is observed between the surveillance data and MTR data. 7

8 TEM Observation : Surveillance Materials 0.12Cu : 4x10 19 n/cm Cu : 6x10 19 n/cm 2 B=[011], 3g (g=21-1) 50nm B=[133], 3g (g=-110) 50nm Mean size: 2.6 nm Mean size: 2.3 nm Number density: 1.8x10 22 m -3 Number density: 1.9x10 22 m -3 Dislocation loops are observed in the RPV materials irradiated in commercial reactors. Number densities of the loops are relatively low. 8

9 TEM Observation : MTR irradiated materials B9-2 (0.04Cu, 6x10 19 n/cm 2 ) B9-3 (0.04Cu, 12x10 19 n/cm 2 ) g g Dislocation loop are observed. Number density is ~10 22 m -3, and the diameter is 4~5 nm. Some of the loops are formed near one side of the line dislocations. 9

10 Dislocation loop formation near line dislocations B9-3 g Clusters are preferentially formed near one side of dislocation. Some clusters are the rings that lie on the same plane, suggesting dislocation loops. Some of the other clusters may be small dislocation loops with solute atom segregation. Cu, Si, P B9-3: R7_02618, 42.9x49.4x265nm, 12.0M Presented at ASTM Symposium in B9-3: R7_02571, 35.7x41.6x235nm, 8.05M 10

11 TEM Observation Number density (m -3 (m ) -3 ) B1 S1 1.0E+22 B9 P1B 7.5E E E+21 Mean diameter (nm) Mean diameter (nm) E E E E E+20 Fluence (n/cm 2, E>1MeV) Fluence (n/cm 2, E>1MeV) 0 0.0E E E E+20 Fluence (n/cm 2, E>1MeV) Fluence (n/cm 2, E>1MeV) Both number density and mean diameter increases with increasing fluence. Number density can be larger because of resolution limit of our TEM measurement. 11

12 Estimates of T due to dislocation loops Orowan model: Estimated T due to disl loop ( o C) B1 S1 B9 P1B RT NDT ( o C) M RT NDT b N d : 0.4 M : 2 12

13 Embrittlement mechanism: revised P CRP G.B SC G.B. Cu Solute atom MD Disl. MD Disl. Copper-enriched cluster Matrix damage Phosphorus segregation on grain boundary Solute atom cluster Dislocation loop 13

14 Outline Part I Irradiation-induced features that cause embrittlement Effect of solute element Effect of temperature Effect of neutron fluence Effect of neutron flux Part II Embrittlement correlation methods Development of Japanese embrittlement correlation Known unknows and unknown unknows 1 4

15 Effect of solute element Copper is the most harmful element. Synergetic effect of copper and nickel has been well recognized since the work by Hawthorne (1982). Phosphorus? Manganese? 15

16 Effect of Ni : IVAR Materials Chemical composition ID CM15 CM16 CM17 Type A533B Plate A533B Plate A533B Plate Composition / wt% Cu Ni Mn Cr Mo P C Si S Fe Bal Bal Bal. Irradiation Condition ID Flux (x10 12 n/cm 2 /s, E>1MeV) Fluence (x10 19 n/cm 2, E>1MeV) Temperature () T

17 Ni Effect of Ni on 0.22Cu-xNi-1.6Mn alloys Cu Si P Dislocation 0.02wt%Ni(CM15) (85x85x260nm, 41M atoms) 0.82wt%Ni(CM16) (89x88x230nm, 41M atoms) 20nm 1.59wt%Ni(CM17) (78x80x220nm, 31M atoms) φt=1.6x10 19 n/cm 2, φ=3x10 11 n/cm 2 /s, T=290 o C 17

18 Effect of Ni on 0.22Cu-xNi-1.6Mn alloys Number density (m -3 ) Cluster Number Density (m -3 ) Volume fraction Cluster Volume Fraction 5.E+23 4.E+23 3.E+23 2.E+23 1.E+23 0.E Ni content (wt%) Ni content (wt.%) 1.2E E E E E E E Ni content (wt%) Ni content (wt.%) Composition (at.%) Guinier diameter (nm) Cluster Composition (at.%) Cluster Diameter(nm) Ni content (wt%) 100% Ni content (wt.%) 80% 60% 40% 20% 0% Ni content (wt%) Ni content (wt.%) C P Si Cu Ni Cr Mn Fe 18

19 Effect of Ni on Hardening G.R. Odette, G.E. Lucas, ASTM STP 1046 (1990) 323. H. Shibamoto, et al., ASTM STP 1405 (2001) 722. Increase in nickel content causes hardening even in very low or no copper materials. Number density of dislocation loops increases and loop size decreases in nickel containing materials. 19

20 Effect of Phosphorus Effect of P has been widely accepted, but the mechanism has not been identified yet. Non hardening embrittlement due to P segregation on grain boundaries is a possibility, but it seems that this is not the mechanism of P effect in western-type RPV materials. There is a data indicating that P plays a role in low Cu materials but not in high Cu materials. P contributes to hardening by forming precipitates. Recent US correlation method P atoms are found mostly on dislocation lines and solute atom clusters (APT). They agglomerate to such features very quickly. 20

21 Effect of P in low and high Cu materials P effect is evident only in low Cu materials. Very little data are available in the surveillance database for low Cu & high P materials. It is not easy to separate the effect of P from that of Cu. Hawthorne,

22 Effect of Mn on Hardening Mn effect may exist in RPV materials. Fe-Mn model alloy also shows larger embrittlement than pure Fe. (A. Kimura, et al.) Mn clusters are also observed in Fe-Mn model alloy. (Y. Nagai, et al.) Fe-ion irradiation of Fe-Mn alloy shows similar results. Fe-ion irradiation RT, 0.3dpa, 3.8x10-5 dpa/s 22

23 Nominal Mn vs LEAP Mn x y z Direction of composition profile Mn Content by LEAP (wt.%) Mn 1:1 line Bulk Mn Content (wt.%) Carbide includeing Mn Composition (at.%) Fe C Mn Cr Ni Cu Si P Distance (nm) The Mn contents measured by APT is far less than the nominal bulk Mn contents, and there is non trivial scatter. Carbides detected by LEAP contain a lot of Mn atoms. 23

24 Outline Part I Irradiation-induced features that cause embrittlement Effect of solute element Effect of temperature Effect of neutron fluence Effect of neutron flux Part II Embrittlement correlation methods Development of Japanese embrittlement correlation Known unknows and unknown unknows 2 4

25 Effect of temperature Low temperature irradiation causes larger shifts in both high and low Cu materials. Empirical linear correlation has been proposed by Jones and Williams for low Cu materials. DBTT ( o C) A533B Shift at Charpy 41J Fluence : 1.7x10 19 n/cm 2, E>1MeV J. Ahlf, F.J. Schmitt, IAEA Specialists Meeting on Irradiation Embrittlement and Surveillance of Reactor Pressure Vessels, IAEA, Vienna, 19-21, Oct Weld: 0.25wt.%Cu Weld: 0.15wt.%Cu Irradiation Temp. ( o C) Base metal: 0.04wt.%Cu 25

26 Effect of temperature : IVAR materials Chemical composition ID LI LH Type A533B Plate A533B Plate Composition / wt% Cu Ni Mn Cr Mo P C Si S Fe Bal Bal. Irradiation Condition ID Flux (x10 12 n/cm 2 /s, E>1MeV) Fluence (x10 19 n/cm 2, E>1MeV) Temperature () T T T

27 Atom Maps : LI (high Cu) materials 270 o C 290 o C 310 o C Cu Si P LI-T18 70x70x270nm, 26M atoms LI-T16 79x79x220nm, 29M atoms 20nm LI-T20 90x93x210nm, 39M atoms 27

28 Atom Maps : LH (low Cu) materials 270 o C 290 o C 310 o C Cu Si P LH-T18 91x91x210nm, 39M atoms LH-T16 20nm 79x79x220nm, 29M atoms LH-T20 91x95x310nm, 58M atoms 28

29 Temperature Effect Cluster Number Density (m -3 ) Number density (m -3 ) Cluster Volume Fraction Volume fraction 8.E+23 7.E+23 6.E+23 5.E+23 4.E+23 3.E+23 2.E+23 1.E+23 0.E+00 1.E-02 8.E-03 6.E-03 4.E-03 2.E IrradiationTemperature () 0.E IrradiationTemperature () LI LH LI LH Square root of cluster Volume Fraction Square root of V f Guinier diameter (nm) Cluster Diameter(nm) IrradiationTemperature () 1.E-01 8.E-02 6.E-02 4.E-02 2.E-02 0.E+00 LI LH IrradiationTemperature () LI LH 29

30 Outline Part I Irradiation-induced features that cause embrittlement Effect of solute element Effect of temperature Effect of neutron fluence Effect of neutron flux Part II Embrittlement correlation methods Development of Japanese embrittlement correlation Known unknows and unknown unknows 3 0

31 Effect of fluence The amount of embrittlement is predicted as a power function of fluece with the exponent of 0.15~0.35 for the fluences up to 1x10 20 n/cm 2, E>1MeV. RG1.99 : logf JEAC4201 : logf (base metal), logf (weld) FIS : 0.35 VVER : logf (VVER-440), 0.33 (VVER-1100) Recent mechanism-guided correlation equations predict that different fluence functions for CRP and MD. T CRP T MD = A (f) 0.5 T CRP = B (1+tanh((log f -C)/D Late Blooming Phase High Ni and high fluence log f MD 31

32 Fluence effect on the volume fraction of SC JNES PRE Project Volume fraction B1 (0.21/0.63) B4 (0.17/0.62) B5 (0.10/0.59) B9 (0.04/0.62) B6 (B5+0.92Ni) B7 (B P) B8 (B5+0.32Si) S1 (0.09/0.62) S1s (0.09/0.62) S2s P1B (0.06/0.58) P2B (0.25/0.59) P3B (P1B+0.018P) P4B (P1B+1.78Ni) Volume fraction N. Soneda et at., J. of ASTM International, Vol. 6, No. 7, Paper ID JAI W1 (0.20/0.88) W2 (0.13/0.86) W3 (0.10/0.88) W4 (0.02/0.84) Fluence (x10 19 n/cm 2, E>1MeV) Fluence (x10 19 n/cm 2, E>1MeV) Volume fractions of solute atom clusters keep increasing with fluence. This is primarily due to the growth of clusters. Number density does not increase very much with fluence. 32

33 Composition change in high-cu material Number of Cu atoms in a cluster Cu G1 G3 Number of Si atoms in a cluster Si G1 G Number of Ni atoms in a cluster Ni Cluster size G1 G3 Number of Mn atoms in a cluster Mn Cluster size G1 G Cluster size Cluster size φt=1.6(g3), 13(G1) x10 19 n/cm 2, φ=1x10 14 n/cm 2 /s, T=290 o C 33

34 Outline Part I Irradiation-induced features that cause embrittlement Effect of solute element Effect of temperature Effect of neutron fluence Effect of neutron flux Part II Embrittlement correlation methods Development of Japanese embrittlement correlation Known unknows and unknown unknows 3 4

35 Dose Rate Effect in Low Cu Material Comparison of French surveillance data and test reactor irradiation data Comparison of test reactor data irradiated at different fluxes Transition temperature shift ( o C) Fluence (x10 19 n/cm 2 ) P. Petrequin, ASMES:1996. Report Number 6 EUR EN Increase in yield stress (MPa) Fluence Low High CRIEPI/UCSB Joint Program Dose rate (n/cm 2 -s) No clear dose rate effect is observed in low Cu materials. 35

36 Low flux irradiation data in Japan SP1 Cu: 0.24 wt.% 60 RT NDT ( o C) Delta Tr30 ( o C) SPT1 ~10 9 n/cm 2 -s SPT2 Surveillance (A) Surveillance (W) ~10 10 n/cm 2 -s MTR ~10 12 n/cm 2 -s 0 0.0E E E E E E E+18 Neutron fluence Fluence (n/cm 2 ) 2, E>1MeV) Very low flux irradiation causes larger shifts. 36

37 Surveillance materials study (2) SP1 Cu: 0.24 wt.% Low flux Irradiation (BWR) RT NDT ( o C) Delta Tr30 ( o C) SPT1 SPT2 ~10 9 n/cm 2 -s Surveillance (A) ~10 10 n/cm 2 -s Surveillance (W) MTR ~10 12 n/cm 2 -s Counts Guinier diamter (nm) SP1 Cu 0.24 wt.% t 9x10 17 n/cm 2 N d 4.32 x m -3 V f 4.39 x 10-3 d G 2.58 nm 0 0.0E E E E E E E+18 Fluence (n/cm 2 ) Neutron fluence ( o C) 30 High flux Irradiation (MTR) Very low flux irradiation causes larger shifts. Lower flux irradiation makes Cuenriched clusters much larger. Count Counts SPT1 Cu 0.24 wt.% t 1.3x10 19 n/cm 2 N d 2.94 x m -3 V f 1.25 x 10-3 d G 1.96 nm Guinier Clusterdiameter(nm) diameter (nm) 37

38 Outline Part I Irradiation-induced features that cause embrittlement Effect of solute element Effect of temperature Effect of neutron fluence Effect of neutron flux Part II Embrittlement correlation methods Development of Japanese embrittlement correlation Known unknows and unknown unknows 3 8

39 39

40 IAEA Training Workshop on Assessment of Degradation Mechanisms of Primary Components in Water Cooled Nuclear Reactors: Current Issues and Future Challenges Understanding on the Mechanisms of Irradiation Embrittlement of RPV Steels and Development of Embrittlement Correlation Method Akiyoshi Nomoto Central Research Institute of Electric Power Industry (CRIEPI) 4 0

41 Outline Part I Irradiation-induced features that cause embrittlement Effect of solute element Effect of temperature Effect of neutron fluence Effect of neutron flux Part II Embrittlement correlation methods Development of Japanese embrittlement correlation Known unknows and unknown unknows 4 1

42 Embrittlement correlations US NRC RG1.99r1 (1977) T 41J KTA 3203 (3/84) (1984) FIS/FIM (1987) US NRC RG1.99r2 (1988) JEAC (1991) WWER-440 (1993) Statistics based CF FF KTA 3203 (6/01) (2001) WWER-1000 (2002) WR-C(5)Rev.1 (2010) T 41 J Williams et al. (1988) Fisher et al. (1983, 1985, 1987) Odette, Lucas (1983, 1985) T MD Mechanism based T EWO (1996) CRP 2010 JEAC (2013) Margolin et al. (2012) Ahlstrand et al. (2012) Williams et al. (2010) EDF (2010) EONY (2007) JEAC (2007) Debarberis et al. (2005, 2006) E (2002) Williams et al. (2001,2002) Revised EWO (2000) 42

43 Statistics based correlations US NRC RG1.99r1 (1977) 5 9 FIS (1987) P Cu 0. f T41 J 08 TT US NRC RG1.99r2 (1988) T 41 J 5 ) P Cu Ni Cu log f CF ( Cu, Ni f JEAC (1991) T T log f P 215Cu Ni Cu f 41J log f Si 61 Ni Ni Cu f 41J 301 T 41J CFFF 43

44 Mechanism based correlationusa EWO (1996) T 41 J T T41 J SMD CRP f SMD log A exp P f 9 T c x CRP B Ni FCu Gf A 8.98x x10 0, Cu wt % 209, FCu (Cu 0.072), Cu wt % B 135, 0.367, Cu wt% 172, log f t Gf tanh f MD T 7 8 7,,, welds forgings plates CRP welds forgings plates 44

45 Mechanism of embrittlementewo CRP SMD SMD CRP : Copper Rich Precipitate : Stable Matrix Damage 2~3 nanometers RTNDT ( C) RT NDT ( C) E+19 4E+19 6E+19 8E+19 1E+20 Fluence (n/cm², E>1MeV) Total MD CEC/CRP Fluence (n/cm 2, E>1MeV) Cupper enriched clusters and matrix damage cause embrittlement CRP formation is a function of Copper content, Nickel content and irradiation time and will be saturated. Effect of temperature and P on MD 45

46 Mechanism based correlationusa EONY (2007) TTS MF C MF term CRP term 2.47 term A Ti P Mn te RP term B Ni f Cue, P gcue, Ni, te t e B 10 t for t for f Cu P Cu P g e e 1 1 log t e Cu Ni, t tanh e Cu e 0 for Cu wt.% min e Max Cu e , Cu, MaxCu for Cu wt.% for typical (Ni 0.5) Linde 80 welds for all other materials Cue 0.448Ni , e for forgings 7 A for plates for welds for forgings for plates in non - CE mfg. vessels for plates in CE mfg. vessels for welds for SRM plates Based on EWO Effective fluence t e Effect of Mn 46

47 RussiaVVER WWER-440 (1993) T k P 0.07Cu F 1 3 WWER-1000 (2002) 800 R T k F R Debarberis et al. (2005, 2006) DBTT shift a n b start 1 e c tanh sat d Matrix damage CEC P segregation 47

48 France FIS/FIM (1987) TT TT Ni Cu Ni Cu P Cu 0.08 P Cu 0.08 FIM FIS EDF (2010) TT A Ni Cu P Cu 0.08 Low copper content in French RPV steels 48

49 USA 49 B M Cu T ,0.31 MIN MAX 30 WR-C(5)Rev.1 (2010) ,613.3,0 10 ln ln MIN MAX P Ni T M M M M F P W Mn Ni P T B B B B F P W

50 WR-C(5) Rev-1 Statistics based correlation Not only US surveillance data but also non-us data and MTR data are used for the development ~2400 data The formula is similar to EONY as a result Developed by Dr. Mark Kirk (NRC) 50

51 Outline Part I Irradiation-induced features that cause embrittlement Effect of solute element Effect of temperature Effect of neutron fluence Effect of neutron flux Part II Embrittlement correlation methods Development of Japanese embrittlement correlation Known unknows and unknown unknows 5 1

52 Previous Japanese correlation JEAC T T log f P 215Cu Ni Cu f 41J log f Si 61 Ni Ni Cu f 41J 301 ΔT 41J, ΔTT Cu, Ni, P, Si f, DBTT shift Content of Cu, Ni, P and Si wt.% Neutron fluencex10 19 n/cm 2, E>1MeV Statistics based correlations 52

53 Prediction by JEAC T T log f P 215 Cu Ni Cu f log f Si 61 Ni Ni Cu f 41J 77 41J 301 JEAC Surveillance data High Cu steels irradiated at low flux Hi Cu steels TBDD shift Low Cu steels Low Cu steels irradiated up to high fluences Neutron fluence (n/cm 2, E>1MeV) 6x10 19 n/cm 2 (40years) 1x10 20 n/cm 2 (60years) 53

54 Development new Japanese correlation Larger embrittlement in high Cu steels than expected at lower flux conditions. Trend of embrittlement of low Cu steels irradiated up to high fluences is different from predicted. New results/knowledge of mechanism of irradiation embrittlement Development of new correlation based on understanding of mechanism 54

55 Embrittlement mechanism SC G.B. Solute atom MD Disl. Solute atom cluster Dislocation loop 55

56 Dislocation loop formation near line dislocations B9-3 g Clusters are preferentially formed near one side of dislocation. Some clusters are the rings that lie on the same plane, suggesting dislocation loops. Some of the other clusters may be small dislocation loops with solute atom segregation. Cu, Si, P B9-3: R7_02618, 42.9x49.4x265nm, 12.0M Presented at ASTM Symposium in B9-3: R7_02571, 35.7x41.6x235nm, 8.05M 56

57 Modeling of microstructural change High Cu steel Low Cu steel Cu Ni, Mn, Si 57

58 Modeling of microstructural change Irradiation defect (dislocation loop) Cu Ni, Mn, Si 58

59 Modeling of microstructural change Irradiation induced clusters Irradiation enhanced clusters Irradiation induced clusters Matrix damage Matrix damage 59

60 Contribution of clusters to embrittlement RT NDT ( o C) T41J RT NDT ( o C) NDT ( o C) V f 1/2 (N. Soneda et al. CRIEPI Q06019, 2007) V f 1/2 V f 1/2 V f 1/2 (JNES PRE Project, N. Soneda et al. JAI , 2009.) DBTT shift is proportional to sqrt of volume fraction of solute atom clusters Independent of chemical composition 60

61 Japanese correlation (JEAC /-2013) Microstructural change C t C t SC MD mat avail 0 C D C C D C 2 4 Cu 1 Cu 2 MD 9 Cu Cu 1 8 Ni F 5 D 2 T Cu C 6 D 7 thermal Cu Ni 2 D C t irrad Cu D SC thermal Cu 1 2 C mat Cu t v SC C t enh Sc v SC C SC Embrittlement due to microstructure mat TSC 17 V f, V 0 f f C Cu, CSC 114 C Ni TMD 18 C MD T T 2 SC T 2 MD 2 DCu t CSC

62 Japanese correlation Based on revised embrittlement mechanism Solute atom clusters Effect of neutron flux Independent of product form (base metal, weld) Prediction of "trend" of embrittlement Offset correction T T T T Fluence Fluence Offset t Fluence 62

63 Surveillance data vs prediction Calculated ΔRT NDT ( C) Base and weld metals SRM materials MTR materials 1:1 line ±22 C Calculated ΔRT NDT ( C) Base and weld metals SRM materials MTR materials 1:1 line ±18 C Measured ΔRT NDT ( C) Measured ΔRT NDT ( C) 63

64 Outline Part I Irradiation-induced features that cause embrittlement Effect of solute element Effect of temperature Effect of neutron fluence Effect of neutron flux Part II Embrittlement correlation methods Development of Japanese embrittlement correlation Known unknows and unknown unknows 6 4

65 Known unknows Unstable matrix feature (UMF) Does high flux irradiation cause larger shifts at high fluences? Is UMF a new phase (MD, CEC + UMF) or anything else? Late Blooming Phase Ni-Mn-Si phase are formed in low Cu and medium Ni materials irradiated in both power reactors and MTRs. Does LB phase appear at high fluences in high Ni (and maybe high Cu) materials? Material effect (?) CE effect, Linde80 effect, Product form effect Initial strength effect Decoration of dislocations by dislocation loops What is the effect of decoration? 65

66 Dislocation loop formation near line dislocations B9-3 g Clusters are preferentially formed near one side of dislocation. Some clusters are the rings that lie on the same plane, suggesting dislocation loops. Some of the other clusters may be small dislocation loops with solute atom segregation. Cu, Si, P B9-3: R7_02618, 42.9x49.4x265nm, 12.0M Presented at ASTM Symposium in B9-3: R7_02571, 35.7x41.6x235nm, 8.05M 66

67 Unkown unknows Embrittlement only from micro- and macro-scopic (mechanical property) points of view has been discussed. 67

68 Thank you very much for your attention. 68