Model of Irradiation Embrittlement WW ER Reactor Pressure Vessel Steel

1. SSC RF“RIAR” • Model of Irradiation Embrittlement WWER Reactor Pressure Vessel Steel V.V.Svetukhin, O.G.Sidorenko, V.N.Golovanov, D.N.Suslov State Science Center of Russian Federation “Research Institute of Atomic Reactors” Russia, Ulyanovsk reg., Dimitrovgrad October, 2005, Ulyanovsk, UlGU

2. SSC RF“RIAR” Background Nowadays, mathematical approximations that are not rested on real physical processes and do not allow for adequate prediction of influence of micro-structural changes on the DBTT shift are used to substantiate the WWER reactor vessel operation and lifetime extension. Purpose 1) A kinetic model developmentof radiation-induced impurities clusterization and precipitation in metals and alloys. 2) An explanation for the shift of ductile-brittle transition temperature on basis a kinetic model. 3) Description of neutron flux density effect on radiation embrittlement of pressure vessel steels.

3. SSC RF“RIAR” Analysis of micro-structural investigations shows the interaction of radiation defects with impurity atoms to play an important part in the process leading to radiation-induced precipitation of impurities. IAEA-TECDOC-1441, June, 2005

4. SSC RF“RIAR” SSC RF“RIAR” Mathematical model of metal strengthening by impurity clusters and precipitates Cu 1. Cu-clusters formation in cascades P cascade 2. Diffusion limited growth of clusters

5. SSC RF“RIAR” Mathematical model of metal strengthening by impurity clusters and precipitates 1. Clusters formation in cascades

6. SSC RF“RIAR” Mathematical model of metal hardeningby impurity clusters and precipitates or

7. SSC RF“RIAR” Calculation of vacancy concentrations and vacancy-accelerated impurity diffusion coefficient Recombination mechanism semi-empirical approximation

8. SSC RF“RIAR” Hardening of metals and alloys by impurity clusters

9. SSC RF“RIAR” Diffusion limited clusterisation (precipitation) «Diffusion flux effect» «Saturation flux effect» “Strong” flux effect No flux effect

10. SSC RF“RIAR” WWER-440 DBTT shift for 15H2МFА steel under irradiation by different neutron flux: F, 1020n/cm2

11. SSC RF“RIAR” VVER-440 300 250 200 150 100 50 Fluence, 1019 n/cm2 0 0 10 20 30 40 50 60 70 Levit V.I., Korolev Yu.N., Tipping Ph. and Lessa R.N.T. Empirical correlation of observed three stages of fast neutron irradiation hardening and embrittlement in WWER-440 pressure vessel materials. – Effects of Radiation on Materials: 18th International Symposium, ASTM STP 1325, 1999

12. 12 Model alloys embrittlement L.Debarberis….

13. 14 Model alloys embrittlement DBTT for LYRA: F=81018 см-2 (Е>0.5 MeV), =31012 сm-2s-1. (●)– experiment, (□) – prediction DBTT for Rovno:F=8 1018 сm-2 (Е>0.5 MeV), =3 1011 сm-2s-1 . (●)– experiment, (□) – prediction

14. SSC RF“RIAR” 19 WWER-1000 DBTT shift for 15H2NМFА steel under irradiation by different neutron flux: Т, 0С (predict) weld base m. CNiE, % Т, 0С (experiment) 20F1/3 (), 4,7СNi3F1/3 (o) (7,6/φ1/4+118(CNi-CNiE)+)F1/3 (●)

15. SSC RF“RIAR” • Conclusion • The report presents a physical model of the radiation-induced precipitation and clusterisation of impurities in solids. • The model allows taking into consideration the influence of such factors as irradiation dose, flux density, impurity concentration on embrittlement. • The proposed model was shown to be applied for description of radiation embrittlement of the WWER-440, WWER-1000 vessel steel. WWER-440: WWER-1000: