Tacis 2.02/95 on VVER 440 RPV Integrity TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.02/95, “VVER , Reactor Pressure Vessel Integrity Assessment” Slide 1 Rev.: Beneficiary:Rosenergoatom, Moscow Contractor:EdF, VTT, Fortum Local Subcontractor:Moht & Atomenergoexport Budget: € Duration:24 months Contract expired:December 1999

Tacis 2.02/95 on VVER 440 RPV Integrity TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.02/95, “VVER , Reactor Pressure Vessel Integrity Assessment” Slide 2 Rev.: Objectives of the project Carry out accelerated re-embrittlement experiments on spare templates from Novovoronezh 3 & 4 RPV for validation of re- embrittlement kinetics. The elaboration of data files (material properties and NDT) needed for the PTS assessment of WWER 440 /230 RPV. Elaboration of mechanical properties by direct measurements of kinetic hardness of the RPV core region material. Re-evaluation of the crack initiation toughness (K Ic) )/ temperature indexation curve by consideration of all typical (representative of WWER 440 / 230 weld materials) results, available in Russia. Presentation of the results to the local Safety Authorities.

Tacis 2.02/95 on VVER 440 RPV Integrity TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.02/95, “VVER , Reactor Pressure Vessel Integrity Assessment” Slide 3 Rev.: Project implementation and results Task 1; Accelerated re-embrittlement experiments for Novovoronesh 3&4 RPV core weld –Templates form the RPV were used for the experimental part –Sub-size test specimens were irradiated in the Kola NPP, Unit 4 –Neutron dose was estimated on routine bases by measuring Mn-54 activity –Irradiation temperature was monitored with melting binary alloys –The test specimens were tested in RRCKI in Moscow after re-irradiation cycle –The increase in yield strength as expected –The shift in transition temperature in re-irradiation after annealing was much smaller than expected (Fig 1 and 2)

Tacis 2.02/95 on VVER 440 RPV Integrity TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.02/95, “VVER , Reactor Pressure Vessel Integrity Assessment” Slide 4 Rev.: Fig. 1Comparison of experimental and calculated embrittlement rates after irradiation-annealing-re-irradiation (IAI) cycle of the RPV core weld of Novovoronesh NPP Unit 3

Tacis 2.02/95 on VVER 440 RPV Integrity TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.02/95, “VVER , Reactor Pressure Vessel Integrity Assessment” Slide 5 Rev.: Fig. 2 Comparison of experimental and calculated embrittleemnt rates after irradiation-annealing-reirradiation cycle of RPV core weld of Novovoronesh NPP Unit 4.

Tacis 2.02/95 on VVER 440 RPV Integrity TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.02/95, “VVER , Reactor Pressure Vessel Integrity Assessment” Slide 6 Rev.: Project implementation and results (cont.) Task 2; Data files for Pressurized Thermal Shock (PTS) assessment; “material properties” A comprehensive summary of material properties needed for PTS studies was elaborated The summary included data on mechanical and chemical properties as well as crack initiation and fatigue crack growth Plant specific material data from Russian VVER 440/230 units Data from open literature, previous projects and other available sources were collected RPV core weld embrittlement aspects were a most important issue (influence of neutron irradiation as a function of neutron fluence) Effect of annealing and post annealing embrittlement was included

Tacis 2.02/95 on VVER 440 RPV Integrity TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.02/95, “VVER , Reactor Pressure Vessel Integrity Assessment” Slide 7 Rev.: Task 2; Data files for PTS analyses; Non-Destructive Testing (NDT) results Spectrum of expected remaining defects in the RPV was elaborated Data collected from NDT-results of manufacturing and acceptance control of VVER RPVs Statistics and experience from manufacturing induced defects was elaborated Detection probability based on the applied quality control and ISI was evaluated Influence of cladding was also considered Corresponding data from Skoda manufacturing procedures was also included The flaw distribution in Russian and Czeck RPVs was practically the same The Marshal distribution gives a higher probability of defects (Fig. 1) No remarkable defects found in any VVER RPVs in ISI Project implementation and results (cont.)

Tacis 2.02/95 on VVER 440 RPV Integrity TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.02/95, “VVER , Reactor Pressure Vessel Integrity Assessment” Slide 8 Rev.: Fig 3. Probability of defect size larger than a

Tacis 2.02/95 on VVER 440 RPV Integrity TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.02/95, “VVER , Reactor Pressure Vessel Integrity Assessment” Slide 9 Rev.: Project implementation and results (cont.) Task 3 Evaluation of the Kinetic Hardness Method (KHM) The objective to evaluate feasibility of determining mechanical properties by a non-destructive method: KHM A correlation has been found between the KHM and the tensile strain diagram According to VNIIAES a correlation has also been confirmed with toughness properties and embrittlement due to irradiation If so, the KHM method could be used for assessing irradiation embrittlement and toughness properties of the core region material of an operating RPV This method could accordingly be considered revolutionary Some controversial opinions do exist regarding the reliable applicability of the method on operating RPVs In Task 1 above, the correlation could not be confirmed (Fig 4)

Tacis 2.02/95 on VVER 440 RPV Integrity TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.02/95, “VVER , Reactor Pressure Vessel Integrity Assessment” Slide 10 Rev.: Fig 4. Comparison of R p0,2 values from real tensile testing with the KHM method for NV 3 core weld

Tacis 2.02/95 on VVER 440 RPV Integrity TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.02/95, “VVER , Reactor Pressure Vessel Integrity Assessment” Slide 11 Rev.: Fig 5. Comparison of R p0,2 values from real tensile testing with the KHM method for NV 4 core weld

Tacis 2.02/95 on VVER 440 RPV Integrity TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.02/95, “VVER , Reactor Pressure Vessel Integrity Assessment” Slide 12 Rev.: Project implementation and results (cont.) Task 4 ; Re-evaluation of the Fracture Toughness curve K Ic –Re-evaluation of the Russian K Ic curve by considering all VVER 440/230 RPV results available in Russia –Comparison with similar results from Phare 2.01/95 –The quality of the available Russian fracture toughness data did not enable upgrading of the K Ic curve in a fully reliable way according to the Maters Curve method –The results confirmed that the Fracture Toughness dependence of Eastern and Western type of RPV steels have a similar temperature dependence

Tacis 2.02/95 on VVER 440 RPV Integrity TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.02/95, “VVER , Reactor Pressure Vessel Integrity Assessment” Slide 13 Rev.: Project implementation and results (cont.) Global conclusions and recommendations –The embrittlement rate of the core weld at NV Units 3 & 4 was much smaller than expected based on sub-size specimen testing –Fracture toughness of template samples should be determined direct by static bend test of pre-cracked sub-size Charpy specimens –Russian acceptance standard for flaw evaluation and PTS analyses are well established –The correlation between mechanical tensile testing and KHM method was poor –Present Russian fracture toughness test data should be re-evaluated by analysing original load-displacement curves, if available –A more accurate statistical analysis using Master Curve approach should be performed