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1 > Framatome ANP GmbH <

2 RPV integrity assessment in Germany Elisabeth Keim GmbH IAEA Workshop Brasil 2

3 Ensurance of RPV Integrity Requirement of RPV integrity is a design principle in the German Basic Safety Concept to ensure enclosure of activity inventory Optimization of: - Materials - Construction and Design - Manufacturing including: Detailed structural mechanics analyses of relevant load cases IAEA Workshop Brasil 3

4 Scheme of deterministic concept for RPV brittle fracture exclusion in Germany deterministic multi-barrier concept Independent redundancies Flawless before in-service Basic safety concept Integrity of material (NDE) In-service initiation and growth excluded Surveillance during operation NDE during inservice inspection Exclusion of initiation Postulated flaw Crack arrest Crack arrest analysis Brittle Safety Assessment NDE during inservice IAEA Workshop Brasil 4

5 RPV - Safety Assessment Material Loading T Temperature IAEA Workshop Brasil 5

6 RPV - Safety Assessment Material Temperature IAEA Workshop Brasil 6

7 Influence of Ageing, Determination of Residual Life Residual Life Assessment by Fracture Mechanics 2c a Loadability M a 2c W 2c/a = Shape factor = Crack depth = Crack length = Wall thickness = W BOL Material resistance > operational loading K IC = f (T, RT NDT ) > K I = f ( o, a, M) EOL BOL unirradiated irradiated CORE Defect size Change of material properties K I, K IC [ N mm -3/2 ] K IC K IC T 41 Stress intensity factor K l K l = K P + K T + K R Temperature [ C ] IAEA Workshop Brasil 7

8 Irradiation Surveillance Design Layout Implementation Assessment of irradiation behaviour Pre & post examination Hot cells Material lab IAEA Workshop Brasil 8

9 Status: Material Status at begin of operation ( all plants ): RT NDT Concept specified values In-service investigations: Values from irradiation program RT NDT Concept WM/BW IAEA Workshop Brasil 9

10 Status: Codes and Practice Status at begin of operation: USA, Germany RT NDT Concept Modifications during operation: USA RT NDT Concept and parallel T 0 Concept Germany ASTME 1921 ( Standard for experiments ) ASME XI, Code Case N 629 ( Application ) ASTM E 900, 10 CFR 50 Draft RT NDT Concept and applied T 0 Concept First application by Stade KTA 3203 in 2000 (Irradiation) KTA Draft IAEA Workshop Brasil 10

11 Safety Assessment according to RT NDT - Concept: RT NDTj = RT NDT + T 41 plant spec. K IC -Curve -1/2 ] 200 [MPa*m 150 unirradiated adjusted versus RT NDT irradiated asjusted versus Fracture toughness Ic K T ASME K IC Curve RT NDTj = RT NDT + T 41 Temperature [ C] Charpy Energy [J] T 41 plant spec. A V -T - Curve Temperature [ C] IAEA Workshop Brasil 11

12 German Plants / Licensing & Irradiation Programs Plant leading component neutron fluence [ cm -2 ] (E > 1MeV) 32 years of operation expected RT NDTj = RT NDT + T 41 [ C ] KWO* UP-WM 2,8 E > 32 > 2008 KKS* UP-WM 1,7 E KWB - A Ring 7 4,4 E KWB - B WM-Wur 3,8 E GKN 1 WM 1,4 E > 2048 KKU Ring 4 3,6 E > 2050 KKG Ring 3 3,0 E > 2052 KKP 2 Ring 3 3,6 E > 2055 KWG WM 3,1 E > 2055 KBR Ring 2 3,1 E 18 < > 2057 KKI 2 WM 3,1 E 18 < 4 64 > 2059 KKE WM 3,1 E 18 < > 2059 GKN 2 WM 3,3 E+18 < 8 64 > 2060 Trillo GW 3,0 E+18 < 2 >32 1) KKB WM 1,4 E KKI 1 WM (RN) 1,0 E 18-7 KKP 1 GW 1,1 E KKK WM 1,0 E KRB - B WM 0,9 E KRB - C WM 1,0 E 18 5 safe operation years of operation > 38 > 64 > 64 ca. 64 > 64 > 64 calendar year > 2020 > 2050 > 2050 > 2050 > 2050 > 2050 PWR BWR *) decomm. IAEA Workshop Brasil 12

13 Determination of Master Curve according to the T 0 Concept K JC in Mpa m K JC for T 0 K JC Local Approach Temperature in C IAEA Workshop Brasil 13

14 K JC for T 0 Master curve 50% Fraktile T 0 Concept (Assessment Curve) ASME K IC using T ASME K IC using T K ASME K IC using RT NDT K JC in MPa m Temperature in C IAEA Workshop Brasil 14

15 Example of Application KWO RPV T 0 - Estimation: unirradiated Base Metal T 0 = -56 C K JC in MPa m % 50 % 5 % all valid K JC -values Ring Temperature in C IAEA Workshop Brasil 15

16 Example of Application KWO RPV T 0 - Estimation: irradiated Base Metal K JC in MPa m Set T 0 = -23 C 2. Set T 0 = -21 C 3. Set T 0 = -4 C Temperature in C IAEA Workshop Brasil 16

17 Example of Application KWO RPV Reference Temperatures Base Metal 100 Reference temperature C RT NDT -6 C 50 0 RT NDTGrenz KTA 3203 new Reference temperature concept RT NDTj = RT NDT + T 41 Ring 2 (Middle value curve) RT To Ring 2 RT To -22 C 2,8E19 cm Neutron fluence Φ (E>1MeV) in cm -2 IAEA Workshop Brasil 17

18 Principle of RPV Brittle Fracture Safety Analysis. in case of PTS K I = σ π a Fracture Toughness K IC and Stress Intensity factor K I in MPa m a σ Material Loading σ a Temperature in C IAEA Workshop Brasil 18

19 Load Path of a Cold Injection Transient in Case of a Postulated Leak Update of the Load Path from As-build condition until today Status at in-service ( all plants ): Core weld Axi-symmetrical cooling Crack depth 10 mm, infinite investigations during service: Strip - / plume cooling Core weld and upper end of core Finite flaw size 10 x 60 mm² derived from NDE RPV A A Fluid-Fluid-Mixing ECC hot water pump mixing water view A plume region pffff postulated leak IAEA Workshop Brasil 19

20 Plume cooling schematically IAEA Workshop Brasil 20

21 Strip and Plume Cooling at the Inner RPV Wall Strip cooling Plume cooling IAEA Workshop Brasil 21

22 Temperature of cold and warm water layer in the cold leg and saturation temperature T_SAT Fluid temperatures in cold leg (deg C) Time (s) IAEA Workshop Brasil 22

23 Heat transfer coefficient between cold leg wall and the water layers Heat transfer coefficient in cold leg (kw/m²k) Time (s) IAEA Workshop Brasil 23

24 KKE, KKP2, GKN II - Matrix of Transients with Consideration of Realistic Injection Configurations; Cold Leg Safety Injection only in the Defect Leg (Size of Leak > 50cm² ) Injection configuration Covered by Number of SIP Number of HRP Hot leg leak size in cm² F Cold leg leak size in cm² 5 / 10 Cold leg safety injection in the defect leg 2 4 FL SK(K) CN FL SK(K) 4 4 CN + SK FL CN+ SK FL CN + SK FL CN+ SK Hot leg safety injection 2 2 / 4 FL SK (K)* FL SK (H,K)* FL SK (K)* SK(H) (K)* cold leg loading caused by HRP-injection SK: Nozzle corner, H: hot leg, K: cold leg FL: Flange connection weld CN: Core weld IAEA Workshop Brasil 24

25 Areas to be considered for German Konvoi plants as an example for KKE as well as Flaw Postulates for Base Material in the Core Weld Region and Nozzle Corner (cold Nozzle) RPV Areas under consideration Plattierung cladding Base Grundwerkstoff metal 2c a Example of crack geometry Hot leg leak 200 cm², Submodel for crack in cylindrical region, flaw depth 20 mm 3 2 GW WEZ Plattierung Example of crack geometry Hot leg leak 200 cm², Submodel for crack in nozzle region, flaw depth 20 mm IAEA Workshop Brasil 25

26 Global Finite Element Model for Temperature and Stress Calculations 1/4 Modell: K-Elemente Knoten IAEA Workshop Brasil 26

27 Finite element sub-model of the cold leg nozzle corner crack Sub model cold leg: Submodell kalter Stutzen: 9276 elements K-Elemente Knoten nodes IAEA Workshop Brasil 27

28 Stresses and Temperatures (injection into hot leg) for Postulated Inner Flaw in the Region of Hot Leg (5 cm² area leak in the cold leg) IAEA Workshop Brasil 28

29 Finite element mesh of a nozzle corner crack in the hot leg of the RPV Submodell model heißer hot leg: Stutzen: elements K-Elemente nodes Knoten IAEA Workshop Brasil 29

30 Temperatures and Axial Stresses for Hot Leg Leak Size 40 cm² (cold leg injection) Temperatures Axial Stresses IAEA Workshop Brasil 30

31 Temperatures and Axial Stresses for Hot Leg Leak Size 100 cm² (cold leg injection) Temperatures Axial Stresses IAEA Workshop Brasil 31

32 Transient Temperature Fields for Leak Sizes of 40 cm² and 100 cm² Animation Leak Size 40 cm² Leak Size 100 cm² IAEA Workshop Brasil 32

33 RPV Safety Assessment Material Loading T Temperature 2 IAEA Workshop Brasil 33

34 Consideration of WPS effect on the load path Material Stress intensity factor K IC K ICWPS Loading K Imax = K IWPS Temperature IAEA Workshop Brasil 34

35 Load Paths for the Core Weld (cold injection) as a Consequence of Different Leak Sizes in the Hot Leg Konvoi, cold leg injection, hot leg leak, core region, flaw size 10x60mm², K I from J as a function of crack tip temperature KI from J [MPa m] KIc(RTNDT (Tang.)= 86 C) KIc(RTNDT (Max.)= 109 C) KJ 100h ke_core_k 2SEP KJ 400h 4SEP KJ 200h 4SEP KJ 100h 4SEP KJ 50h 4SEP to be correlated with material properties leading transient crack tip temperature [ C] IAEA Workshop Brasil 35

36 German Plants / Licensing & Irradiation Programs Plant leading component neutron fluence [ cm -2 ] (E > 1MeV) 32 years of operation expected RT NDTj = RT NDT + T 41 [ C ] KWO* UP-WM 2,8 E > 32 > 2008 KKS* UP-WM 1,7 E KWB - A Ring 7 4,4 E KWB - B WM-Wur 3,8 E GKN 1 WM 1,4 E > 2048 KKU Ring 4 3,6 E > 2050 KKG Ring 3 3,0 E > 2052 KKP 2 Ring 3 3,6 E > 2055 KWG WM 3,1 E > 2055 KBR Ring 2 3,1 E 18 < > 2057 KKI 2 WM 3,1 E 18 < 4 64 > 2059 KKE WM 3,1 E 18 < > 2059 GKN 2 WM 3,3 E+18 < 8 64 > 2060 Trillo GW 3,0 E+18 < 2 >32 1) KKB WM 1,4 E KKI 1 WM (RN) 1,0 E 18-7 KKP 1 GW 1,1 E KKK WM 1,0 E KRB - B WM 0,9 E KRB - C WM 1,0 E 18 5 safe operation years of operation > 38 > 64 > 64 ca. 64 > 64 > 64 calendar year > 2020 > 2050 > 2050 > 2050 > 2050 > 2050 PWR BWR *) decomm. IAEA Workshop Brasil 36

37 Load Paths for the Cold Nozzle (hot and cold injection) as a Consequence of Different Leak Sizes in the Hot Leg KI aus J [MPa m] Konvoi, cold leg nozzle, flaw depth 10 mm, K I from J as a function of crack tip temperature KIc(RTNDT (Tang.)= 1,5 C) to be correlated with KIc(RTNDT (Max.)= 13 C) material properties KJ 015h he_stutzen_k 2SEP KJ 025h he_stutzen_k 2SEP KJ 100h he_stutzen_k 2SEP KJ 040h ke_stutzen_k 2SEP KJ 100h ke_stutzen_k 2SEP KJ 50h 4SEPk_Stutzen_k KJ 100h 4SEPk_Stutzen_k KJ 200h 4SEPk_Stutzen _k KJ 400h 4SEPk_Stutzen_k leading transient crack tip temperature [ C] IAEA Workshop Brasil 37

38 Summary on load (1) Updated thermal hydraulic analysis for six German plants: KKP 2 (Philippsburg), GKN II (Neckarwestheim), KKE (Emsland) GKN I (Neckarwestheim) Biblis A and B replacing the former load case Circumferential Thermo shock in the core weld region. Simulation of plant behavior by variation of the relevant leak load paths in case of safety injection. Areas of interest: nozzle (new) flange (new) core Weld (updated) were considered simultaneously. IAEA Workshop Brasil 38

39 All RPV areas were considered for each transient For all six plants a similar transient behavior is demonstrated Determination of the leading transient Summary on load (2) In the nozzle area the leading transients are small leak sizes < 100 cm² In the irradiated core region and in the unirradiated flange region the leading transient is for all plants a 100 cm² leak size The irradiated core weld is no longer the leading area Exclusion of brittle fracture is demonstrated in the specific RPV areas for the relevant loss of coolant paths investigated. Sufficiently large safety margins are obtained for all different injection modes IAEA Workshop Brasil 39

40 Experiences in the field of PTS Activities in materials engineering, irradiation surveillance programs and / or integrity analysis have been performed for PWR and BWR in Germany: Pressurized water reactors Grohnde KWG, Grafenrheinfeld KKG/BAG, Unterweser KKU, Phillipsburg 2 KKP 2, Biblis A and B KWB A/B, Obrigheim KWO, Neckarwestheim 1 and 2 GKN 1/2, Stade KKS, Brokdorf KBR, Emsland KKE and Isar 2 KKI 2 Boiling water reactors Phillipsburg 1 KKP1, Isar 1 KKI 1, Brunsbüttel KKB, Würgassen KWW, Krümmel KKK, Gundremmingen B and C GUN B/C IAEA Workshop Brasil 40

41 Experiences in the field of PTS Activities in materials engineering, irradiation surveillance programs and / or integrity analysis have been performed for the following foreign PWR and BWR: KWU-type (PWR): Gösgen KKG/D (Switzerland) Borssele KCB (Netherlands) Trillo CNT 1 (Spain) Angra 2 (Brazil) KWU-type (PHWR): Atucha 1 CNA 1 (Argentina) Westinghouse-type (PWR): Beznau-1 KKB 1 (Switzerland) Beznau-2 KKB 2 (Switzerland) Framatome-type CP0 (PWR): Fessenheim (France) GE-type (BWR) Mühleberg KKM (Switzerland) Leibstadt KKL (Switzerland) Santa Maria de Garona SMG (Spain) VVER-type (PWR) Kozloduy Unit 1-4 KNPP 1-4 (Bulgaria) Novovoronezh 3/4 NVNPP 3/4 (Russia) Bohunice IAEA Workshop Brasil 41