CRISM “Prometey”, Saint-Petersburg, Russia 1 ПОСТРОЕНИЕ РАСЧЕТНОЙ ТЕМПЕРАТУРНОЙ ЗАВИСИМОСТИ ВЯЗКОСТИ РАЗРУШЕНИЯ КОРПУСНЫХ РЕАКТОРНЫХ МАТЕРИАЛОВ: ОБЩИЕ ПРИНЦИПЫ И РЕЗУЛЬТАТЫ CONSTRUCTION OF THE DESIGN TEMPERATURE DEPENDENCE OF FRACTURE TOUGHNESS FOR RPV MATERIALS: BASIC PRINCIPLES AND RESULTS B. Z. Margolin, V.N. Fomenko, A.G. Gulenko, V.A. Shvetsova, V.A. Nikolaev, A.M. Morozov, L.N. Ryadkov CRISM “Prometey”, Saint-Petersburg V.A. Piminov FSUE EDO “Gidropress”, Podol’sk V.G. Vasiliev Concern Rosenergoatom, Moscow N. A. Shulgan Izhorsky Zavody, Saint-Petersburg presented by Valentin Fomenko

CRISM “Prometey”, Saint-Petersburg, Russia 2 OUTLINE OF PRESENTATION 1. Introduction: advanced methods of prediction of fracture toughness 2. The Unified Curve concept - main considerations and some results 3. Basic principles of construction of the design temperature dependence of fracture toughness, K JC (T) 4. Determination of the margins when constructing the K JC (T) curve with regard for - the uncertainty caused by restricted number of tested specimens - the uncertainty connected with spatial non-homogeneity of RPV material - type of tested specimens 5. Conclusions

CRISM “Prometey”, Saint-Petersburg, Russia 3 ADVANCED METHODS OF PREDICTION OF FRACTURE TOUGHNESS MethodAdvantagesShortcomings 1 Master Curve [ASTM E 1921] Simple use and calibration The lateral temperature shift condition is used  non-conservative predictions for highly irradiated steels 2 Basic Curve [РД ЭО ] 3 Probabilistic Prometey model [РД ЭО ] Prediction for any degree of material embrittlement Intensive calculations 4 Unified Curve [standard under ellaboration] Simple use and calibration. Any degree of material embrittlement

CRISM “Prometey”, Saint-Petersburg, Russia 4 THE UNIFIED CURVE CONCEPT 1.The temperature dependence of fracture toughness for RPV steel for any degree of material embrittlement is described by for В=25 mm и P f =0.5. When degree of embrittlement increases the parameter  decreases. 2.The parameter  may be determined by single temperature method and multiple temperature method on the procedure like as T o determination in the Master Curve 3.For multiple temperature method,  is calculated by equation where K JC(i) –the experimental value of K JC obtained at T test =T i.

CRISM “Prometey”, Saint-Petersburg, Russia 5 NEW ENGINEERING METHOD (UNIFIED CURVE) FOR PREDICTION OF K JC (T) FOR DIFFERENT MATERIALS WITH VARIOUS DEGREES OF EMBRITTLEMENT 1. AS-RECEIVED STATE MASTER CURVE UNIFIED CURVE

CRISM “Prometey”, Saint-Petersburg, Russia 6 NEW ENGINEERING METHOD (UNIFIED CURVE) FOR PREDICTION OF K JC (T) FOR DIFFERENT MATERIALS WITH VARIOUS DEGREES OF EMBRITTLEMENT 2. HIGH DEGREE OF EMBRITTLEMENT MASTER CURVE UNIFIED CURVE

CRISM “Prometey”, Saint-Petersburg, Russia 7 SCHEME FOR CONSTRUCTION OF THE DESIGN K JC (T) CURVE 4 – the curve constructed with the margin on the tested specimen type. Curve 4 takes into account that constraint for a zone of RPV may be larger than for sub-sized specimen of Charpy type. 5 – the design curve – the curve constructed with all the considered margins and recalculated for crack front length B=150 mm and the brittle fracture probability P f =0.05. Curve 5 shows that only 5% of specimens from RPV zone with the worst properties have K JC corresponding to curve 5. 1 – the curve determined from test results of (6  12) surveillance specimens The restricted number of specimens may provide K JC larger than actual properties of a material. 2 – the curve constructed with the margin on the restricted number of surveillance specimens. K JC for material of surveillance specimens with the confidential probability 95% is larger than K JC for curve 2. 3 – the curve constructed with the margin on spatial non-homogeneity of RPV material. K JC for any zone of RPV with the confidential probability 95% is larger than for curve 3.

CRISM “Prometey”, Saint-Petersburg, Russia 8 The function may be found with statistical theory when taking into account the Weibull distribution function for brittle fracture probability and the normal distribution function for average values of experimentally determined parameters. The margin  sp is introduced to take into account this uncertainty. THE UNCERTAINTY IN THE DETERMINATION OF  CAUSED BY RESTRICTED NUMBER OF TESTED SPECIMENS The relative margin is a function of the number N of tested specimens has to be determined.

CRISM “Prometey”, Saint-Petersburg, Russia 9 Main considerations and steps: 1.Value  is described by normal distribution function. 2.When using 95% confidential probability for the low boundary of the parameter  min =  -   sp,  Ω sp =1.6  [Ω], σ[Ω] - standard deviation DETERMINATION OF THE MARGIN δΩ sp CAUSED BY RESTRICTED NUMBER OF TESTED SPECIMENS 3. From the Unified Curve Task: to find the dependence of  Ω sp on the number N of tested specimens.

CRISM “Prometey”, Saint-Petersburg, Russia When replacing on (as these values are very close ) the relative margin as a function of the number N of tested specimens is written as 3. For the normal distribution function for K JC(med) and three-parameters Weibull distribution for brittle fracture probability For example, for N=10 the value of δΩ sp corresponds to (  T 0 ) sp =11°C if the coefficient b is unknown if the coefficient b=4

CRISM “Prometey”, Saint-Petersburg, Russia 11 INFLUENCE OF SPECIMEN TYPE ON FRACTURE TOUGHNESS where and - values of the temperature Т 0 in Master Curve for СТ specimens and SE(B)-10 specimens. The margin  T type is introduced to take into account the difference in the value of  determined on the basis of test results of specimens of different types. Pre-cracked Charpy s SE(B)-10 pecimens are usually used as surveillance specimens. Available fracture toughness data allow the determination of  T type as

CRISM “Prometey”, Saint-Petersburg, Russia 12 TEST RESULTS OF FRACTURE TOUGHNESS SPECIMENS OF VARIOUS TYPES * - Transferability of Fracture Tougness Data for Integrity Assessment of Ferritic Steel Component T 0, °С

CRISM “Prometey”, Saint-Petersburg, Russia 13 DETERMINATION OF THE MARGIN FOR FRACTURE TOUGHNESS SPECIMENS OF VARIOUS TYPES Pre-cracked Charpy specimens CT-specimens SE(B) specimens with deep (50%) side grooves K JC, МPа√m Temperature, °С  T type  T type = 15 o C  T type = 0 o C

CRISM “Prometey”, Saint-Petersburg, Russia 14 THE UNCERTAINTY IN THE VALUE OF  CAUSED BY RPV MATERIAL NON-HOMOGENEITY 1.The design dependence has to be constructed for RPV zone with the minimum resistance to brittle fracture. 2. Tests of surveillance specimens provide average values of characteristics of resistance to brittle fracture. 3. As quantitative measure of material non-homogeneity, the relative margin that does not depend on material condition is introduced :  pr is determined from test results of surveillance specimens, δΩ NH is value of  for RPV zone with the minimum resistance to brittle fracture, δΩ NH = Ω pr - Ω NH 4. The margin is found when using the distribution function of the critical brittle fracture temperature T K for RPV in the as-received (unirradiated) condition. 5. The Unified Curve concept is used to calculate  NH corresponding to the maximum T K value (T K value for RPV zone with the minimum resistance to brittle fracture) and  pr corresponding to average value of T K.

CRISM “Prometey”, Saint-Petersburg, Russia 15 DETERMINATION OF THE MARGIN ON SPATIAL NON-HOMOGENEITY OF RPV MATERIAL  σ(T K )  (T K )  1 (T K )  2  (T K ) NH =1.6(σ[T K ]) NH σ(T K ) R σ(T K ) Z (T K ) R1 (T K ) R2 (T K ) R3 (T K ) Z2 (T K ) Z1 (T K ) Z3 Z R Θ Z R Θ  Ω NH

CRISM “Prometey”, Saint-Petersburg, Russia 16 DETERMINATION OF THE MARGIN ON SPATIAL NON-HOMOGENEITY OF RPV MATERIAL for weld metal On the basis of analysis of the distribution of the critical brittle fracture temperature T K for circumferential welds of RPVs for WWER-440 and WWER-1000, the margin on spatial non-homogeneity  NH was found. Non-homogeneity of RPV weld metal was analyzed for two different directions of RPV: - along weld length (  circumferential direction) - on weld height (R radial direction) δ (T K ) NH (δT K ) R =21°C, (  T K )  =9°C Z R Θ δ(T K ) NH ≈23°C

CRISM “Prometey”, Saint-Petersburg, Russia 17 On the basis of analysis of the distribution of the critical brittle fracture temperature T K for archive blocks of RPVs for WWER-1000, the margin on spatial non-homogeneity  NH was found. Non-homogeneity of RPV base metal was analyzed for three different directions of RPV: - on RPV height (Z direction) - on RPV wall thickness (R direction) - on circumferential direction (  direction) (δT K ) R =18 °C, (  T K ) Z =18 °C, (  T K )  =10 °C δ(T K ) NH ≈27°C DETERMINATION OF THE MARGIN ON SPATIAL NON-HOMOGENEITY OF RPV MATERIAL for base metal δ (T K ) NH

CRISM “Prometey”, Saint-Petersburg, Russia 18 If the calculated flaw is located on the distance from surface no larger than ¼ of wall thickness δ(T K ) R = 0 DETERMINATION OF THE MARGIN ON SPATIAL NON-HOMOGENEITY OF RPV MATERIAL δ(T K ) NH ≈ 21 °C S/4 T K for surveilance specimens T K δ(T K ) RZΘ wall thickness (S) Z 1 Θ 1 Z 2 Θ 2 δ(T K ) ZΘ

CRISM “Prometey”, Saint-Petersburg, Russia 19 where k=0.33 when recalculating from B=25 mm to B=150 mm and from P f =0.5 to P f =0.05 EQUATION OF THE DESIGN K JC (T) CURVE CONSTRUCTED WITH ALL THE CONSIDERED MARGINS The margin on spatial non-homogeneity of RPV material The margin on the tested specimen number The margin on the tested specimen type

CRISM “Prometey”, Saint-Petersburg, Russia 20 CONCLUSIONS 2. The numerical values of all the considered margins are determined. 3. Equation of the design temperature dependence of fracture toughness K JC (T) is proposed. 1.Scheme for construction of the design temperature dependence of fracture toughness K JC (T) is proposed. This curve is constructed on the basis of the Unified Curve concept and the margins that take into account  the uncertainty caused by restricted number of tested surveillance specimens;  the uncertainty connected with spatial non-homogeneity of RPV material;  type of tested specimens.