R 2.06/96, Surveillance of VVER-1000 RPV Beneficiary:Rosenergoatom, Moscow Consortium:Belgatom, Siemens AG, SCK-CEN Local Subcontractor:Atomstroyexport Budget: € Duration:30 months Contract expired:November 2001 TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.06/96, “Surveillance Program for VVER RPV”

R 2.06/96, Surveillance of VVER-1000 RPV Objectives of the project Define adequate and reliable evaluation methods for the determination of the real irradiation conditions of the surveillance specimens (neutron flux, temperature) Re-assess the current situation of the surveillance programs using knowledge received in previous studies Improve the quality and reliability of surveillance test results by using reconstitution technique adopted at RRCKI Define corrective actions and alternative surveillance programs as well as archive material and advanced characterisation methods TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.06/96, “Surveillance Program for VVER RPV”

R 2.06/96, Surveillance of VVER-1000 RPV Project implementation and results Task 1; Description of the Surveillance program of VVER 1000 A comprehensive description of the surveillance program of different types of VVER 1000 RPVs (V-320 and V-187) The following shortcomings were identified and reported: –Capsules located in a position with high neutron flux gradient (Fig.) –Spectral index of Surveillance Specimens (SS) differ from that of the RPV wall –Decay half life of the main dosimeter 54Mn is too short;extrapolations needed –Irradiation temperature was believed to be higher than of the RPV wall (305 o C /290 o C ) –Use of standard Charpy specimens does not allow to evaluate reliable transition temperature; only 6 specimens out of 12 can be used in each set Surveillance samples above the core Neutron fluence variation 200% Irradiation temperature ?

R 2.06/96, Surveillance of VVER-1000 RPV Task 1; Continuation –Surveillance test results from Balakovo, Kalinin and Novovoronesh VVER 1000 NPPs were reviewed and data base was elaborated –Totally 11 sets of surveillance specimens were reviewed –The results come mainly from sets number 1 and 2, for NV Unit 5 set nr. 3 was also reported (17 years of operation) –Due to lead factor the results from set nr. 3 corresponds to End of Life conditions at RPV wall position (Fig.) –The measured embrittlement shift was in many cases higher than expected based on the Russian Guide (Fig.) –The reason to the shift was considered the high Ni-content of weld material TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.06/96, “Surveillance Program for VVER RPV”

R 2.06/96, Surveillance of VVER-1000 RPV Kalinin 1; Fast neutron fluence on SS

R 2.06/96, Surveillance of VVER-1000 RPV VVER-1000 Surveillance test results of weld metal

R 2.06/96, Surveillance of VVER-1000 RPV Task 2; Real irradiation conditions –The main objective to determine the real irradiation conditions of the SS –A special irradiation set was designed and irradiated in Balakovo Unit 1 –The irradiation took one year; from 12/ /2000 –Special temperature monitors (melting alloys from SCK-CEN) and dosimeters (Fe, Mn, Ni, Ti, Cu, Co and Nb) were used for determining the irradiation conditions –Activity measurements were carried out on pieces of central plate and the Charpy V specimens –The azimuthal neutron distribution was determined by measuring activity of cut outs of the support plate of the capsule TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.06/96, “Surveillance Program for VVER RPV”

R 2.06/96, Surveillance of VVER-1000 RPV The special irradiation capsule

R 2.06/96, Surveillance of VVER-1000 RPV Task 2; Real irradiation conditions; Continuation The results of the temperature measurement showed that the upper limit of the irradiation temperature of the SS is 300 o C This is a good result and confirms that the reliability of the SS testing is quite consistent as far as the irradiation temperature is concerned (Table) The results from the dosimetry monitoring showed the following as regards C/E (calculation to experiment): Fe dosimetry gives C/E close to 1 Ni dosimetry overestimates; C/E is Ti dosimetry underestimates; C/E is Cu dosimetry shows big scatter C/E being (Co contamination could disturb) Nb dosimetry gives C/E Nb is the most promising dosimeter due to representative threshold and long saturation TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.06/96, “Surveillance Program for VVER RPV”

R 2.06/96, Surveillance of VVER-1000 RPV Task 3Advanced methodologies – Toughness determination Task 3.1; Charpy-V specimens reconstitution –Reconstitution and testing of broken surveillance specimens by “stud welding” method (Fig) –The method was qualified in RRCKI –Collect specimens with similar neutron fluence (+/-15%) values in order to produce an acceptable amount of test specimens and results for a reliable toughness curve –Specimens from Kalinin Unit 1, set # 2 were selected for the study –The results of reconstitution is shown in Fig. –The DBTT is higher than the Guide curve; The original toughness is much below 0 o C so the absolute transition temperature is still below the projected one Principle and sequence of reconstitution

R 2.06/96, Surveillance of VVER-1000 RPV DBTT shift for Kalinin 1 with reconstitution TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.06/96, “Surveillance Program for VVER RPV”

R 2.06/96, Surveillance of VVER-1000 RPV –Different NDT methods for monitoring neutron embrittlement of RPV were briefly reviewed –The study focused on methods that are currently in use or in an advanced stage of development and under pre-qualification –The conclusion was that there is no fully qualified fully reliable NDT technique to quantify the radiation embrittlement of RPV –The most promising methods to date are; Kinetic hardness, Magnetic properties, Positron annihilation and Thermoelectric power –The stainless steel cladding makes NDT testing on the vessel wall difficult –Available technique can give only quantitative information on material state below cladding Task 3.2; Non Destructive Testing (NDT) TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.06/96, “Surveillance Program for VVER RPV”

R 2.06/96, Surveillance of VVER-1000 RPV Task 3.3 and 3.4; ”Master Curve” and “Local Approach” –Presently the fracture toughness (FT) of the SS is determined by an indirect approach (correlation of Charpy V / FT) –Master Curve approach gives a possibility of direct determination of FT with improved reliability –The Russians have introduced a corresponding direct FT method called “Local Approach” –The aim of Tasks 3.3 and 3.4 was to compare this two methods by performing simultaneous testing –Two materials were selected for the comparison program: Artificially embrittled weld of VVER 1000 RPV SS from Kalinin 1 NPP surveillance program –FEM calculations were carried out to confirm experimental results of crack resistance curve (J-  a) TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.06/96, “Surveillance Program for VVER RPV”

R 2.06/96, Surveillance of VVER-1000 RPV Comparison of the methods for Kalinin weld

R 2.06/96, Surveillance of VVER-1000 RPV Local Approach Master Curve Comparison of the methods for the artificially embrittled material

R 2.06/96, Surveillance of VVER-1000 RPV The results of the comparative testing showed the following: –The comparison of the Master Curve and Local Approach showed good agreement for the tough material form Kalinin surveillance program –The agreement was not very good for the artificially highly embrittled RPV steel FEM calculations showed a good agreement with experimental crack resistance results Task 3.3 and 3.4; ”Master Curve” and “Local Approach” (cont.) TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.06/96, “Surveillance Program for VVER RPV”

R 2.06/96, Surveillance of VVER-1000 RPV Task 4.Corrective actions - alternative surveillance programs Reconstitution needed in order to provide sufficient number of specimens for toughness testing Advanced technique, such as Master Curve and Local Approach recommended A combination of SS with similar neutron dose from different surveillance sets will increase reliability of toughness testing Activity of each Charpy or TPB specimens need to be measured in the notch region The present withdrawal schedule of sets nr. 1, 2 and 3 is well based. The withdrawal of remaining sets 4, 5 and 6 shall be based on life-time management strategy of the NPP No promising proposals on alternative surveillance programs could be identified TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.06/96, “Surveillance Program for VVER RPV”

R 2.06/96, Surveillance of VVER-1000 RPV Dosimetry Detailed local power distribution of upper boundary fuel element cycle by cycle operation history needed Nb should be used for dose monitoring; even extraction of Nb from RPV and stainless steel should be utilized Capsule orientation should be determined by using Nb wires or plates Specimen reconstitution Reconstitution is recommended systematically in order to provide sufficient number of specimens with uniform fluence The neutron fluence of each selected broken specimen need to be re-evaluated before reconstitution Updating of existing data and trend curve development Advanced methods – Master Curve and Local Approach The shape of the FT curve need to be confirmed for brittle material Task 5.Recommendations for Surveillance programs TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.06/96, “Surveillance Program for VVER RPV”

R 2.06/96, Surveillance of VVER-1000 RPV Main conclusions 1.This Tacis project was very successful providing extremely important values to the embrittlement assessment of VVER 1000 RPVs 2.The irradiation temperature of the surveillance specimens was confirmed to be representative 3.The need of upgrading neutron dosimetry and the fluence evaluation procedures of the of the SS of the VVER 1000 RPV was endorsed 4.The need of upgrading the fracture toughness trend curves for irradiated RPV material was identified and strongly recommended 5.A means of upgrading the trend curves is the use of reconstitution and improved neutron monitoring and calculations TACIS Project: R8.01/98 – TRANSLATION, EDITING AND DIFFUSION OF DOCUMENTS (Result Dissemination) Tacis R2.06/96, “Surveillance Program for VVER RPV”