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

Safety Assurance of NPP with WWER MNTK-2007, May 29 – June , FSUE EDO “GIDROPRESS”, Podolsk, Russia 2 Background  The valid surveillance test data are a key issue for a safety assurance of WWER reactor pressure vessel  According to PNAE G 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 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 Objective

Safety Assurance of NPP with WWER MNTK-2007, May 29 – June , FSUE EDO “GIDROPRESS”, Podolsk, Russia 3 Materials and specimens  WWER-1000 RPV materials for South-Ukrainian NPP:  base (15Х2НМФАА steel)  weld metal (Cv-10KhGNMAA and flux 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 )

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

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

Safety Assurance of NPP with WWER MNTK-2007, May 29 – June , FSUE EDO “GIDROPRESS”, Podolsk, Russia 6 Charpy impact test data for base metal Notes: *) Charpy V-notch specimens for Charpy transition temperature curve Set (location) Quantity of specimens * ) Fluence scatter, % Mean fluence (E>0,5 MeV), n/m 2 T kF,  C∆T F,  CA F,  C Unirradiated specimens modernized 2L (upper layer) 12713, modernized 2L (lower layer) 11927, standard 1L (upper layer) , standard 1L (lower layer) , Reconstitution 1L 12911, Reconstitution 1L 13 40,

Safety Assurance of NPP with WWER MNTK-2007, May 29 – June , FSUE EDO “GIDROPRESS”, Podolsk, Russia 7 Charpy impact test data for weld metal Notes: *) Charpy V-notch specimens for Charpy transition temperature curve Set (location) Quantity of specimens * ) Fluence scatter, % Mean fluence (E>0,5 MeV), n/m 2 T kF,  C∆T F,  CA F,  C Unirradiated specimens modernized 2L (upper layer) , modernized 2L (lower layer) 13 20, standard 1L (upper layer) , standard 1L (lower layer) , Reconstitution 1L 12810, Reconstitution 1L ,

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

Safety Assurance of NPP with WWER MNTK-2007, May 29 – June , 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