V. Revka, E. Grynik, L. Chyrko, Yu. Chaikovsky Institute for Nuclear Research NASU, Kiev, Ukraine

1. A comparison of the surveillance test results for the South-Ukrainian NPP unit 2 standard and modernized surveillance assemblies V. Revka, E. Grynik, L. Chyrko, Yu. Chaikovsky Institute for Nuclear Research NASU, Kiev, Ukraine V. Kovirshyn State Scientific and Technical Centre NRS, Kiev, Ukraine

2. The valid surveillance test data are a key issue for a safety assurance of WWER-1000 reactor pressure vessel According to PNAE G-7-002-86 a fluence scatter for specimens should not exceed 15 % to estimate RPV material radiation embrittlement using Charpy impact test data There are some shortcomings in standard surveillance assembly design that result in a high scatter ( 35 %) in fluence values for irradiated Charpy V-notch specimens Some surveillance sets in South-Ukrainian NPP unit 2 include the modernized assemblies that allows irradiating the Charpy V-notch specimens according to PNAE G-7-002-86 requirements Specimen reconstitution technique is also used to get valid surveillance test data Comparison of RPV material radiation embrittlement rate estimated by standard and modernized surveillance program, and the reconstitution technique Background Objective Safety Assurance of NPP with WWER MNTK-2007 , May 29 – June 1 2007, FSUE EDO “GIDROPRESS”, Podolsk, Russia

3. WWER-1000 RPV materials for South-Ukrainian NPP: base (15Х2НМФАА steel) weld metal (Cv-10KhGNMAAandflux ФЦ-16 ) with high nickel (1,74 % wt) and manganese (0,93 % wt) content Surveillance Charpy V-notch specimens (10 mm x 10 mm x 55 mm) Standard surveillance program 1L set (RSC Kurchatov Institute data) Specimens irradiated for 12 fuel cycles (~ 3213 eff. days) Reconstitution technique Modernized surveillance program 2L set (Kiev Institute for Nuclear Research) Specimens irradiated for 10 fuel cycles (~ 2623 eff. days) Materials and specimens Safety Assurance of NPP with WWER MNTK-2007 , May 29 – June 1 2007, FSUE EDO “GIDROPRESS”, Podolsk, Russia

4. Lead factor for an upper layer is  1 Lead factor for a lower layer is  2,5 Charpy Tension Upper layer Lower layer Standard surveillance assembly Safety Assurance of NPP with WWER MNTK-2007 , May 29 – June 1 2007, FSUE EDO “GIDROPRESS”, Podolsk, Russia

5. Upper layer Lower layer Modernized surveillance assembly Assembly Container Safety Assurance of NPP with WWER MNTK-2007 , May 29 – June 1 2007, FSUE EDO “GIDROPRESS”, Podolsk, Russia

6. Charpy impact test data for base metal Notes: *)Charpy V-notch specimens for Charpy transition temperature curve Safety Assurance of NPP with WWER MNTK-2007 , May 29 – June 1 2007, FSUE EDO “GIDROPRESS”, Podolsk, Russia

7. Charpy impact test data for weld metal Notes: *)Charpy V-notch specimens for Charpy transition temperature curve Safety Assurance of NPP with WWER MNTK-2007 , May 29 – June 1 2007, FSUE EDO “GIDROPRESS”, Podolsk, Russia

8. DBTT radiation shift for South-Ukrainian NPP-2 Base metal Weld metal • Transition temperature shift data based on the different approaches describe a tendency of material radiation embrittlement in the same way • Chemistry factor AF based on the standard surveillance test data can be considered as valid to estimate the embrittlement rate of RPV materials Safety Assurance of NPP with WWER MNTK-2007 , May 29 – June 1 2007, FSUE EDO “GIDROPRESS”, Podolsk, Russia

9. Conclusions • Modernized surveillance test data and reconstitution technique confirm a radiation embrittlement rate of WWER-1000 RPV materials for South-Ukrainian NPP-2 that has been obtained in the frame of a standard surveillance program • Charpy impact test data from the standard surveillance program can be used to get a reliable estimation of RPV material radiation embrittlement rate for South-Ukrainian NPP unit 2 Safety Assurance of NPP with WWER MNTK-2007 , May 29 – June 1 2007, FSUE EDO “GIDROPRESS”, Podolsk, Russia