1. VVER Reactor Pressure Vessel Start of life toughness
2nd Nuclear Knowledge Preservation & Consolidation (NKP&C) Workshop
WWER – WS2
Amsterdam, November 2008
VVER Reactor Pressure Vessel
Start of life toughness
Marta Serrano
Structural Materials Division
CIEMAT

2. Reference fracture toughness curves
Introduction
Reference fracture toughness curves
VVER 440 Base material (15Kh2MFA and 15Kh2MFAA)
[KI]3=35+45 exp(0.02(T-Tk))
VVER 1000 Base material (15Kh2NMFA and 15Kh2NMFAA)
[KI]3=74+11 exp(0.0385(T-Tk))
VVER 440 and VVER 1000 welds
[KI]3=35+53 exp(0.0217(T-Tk))
The following temperature generalised dependence of [KIC] can be used for RPV PTS analysis:
[KIC] = exp [0.02 (T-Tk)]; [KIC] ≤ 200 MPa m1/2
This dependence corresponds to specimen thickness of 150mm and Pf = 0.05.

3. Reference fracture toughness curves
Introduction
Reference fracture toughness curves
[KI]3 MPam
(T-Tk) 50
100
150
200
250
300
-100
-50
VVER 440 base metal
VVER 1000 base metal
Welds
All PTS analysis Pf=0.05

4. ODIN>SOL_Toughness papers
Introduction
ODIN>SOL_Toughness papers
None are directly applicables to the subject
Other paper included in other ODIN folders and on the literature are used
Brumovsky M., (1992), “VVER Reactor pressure vessel integrity assessment comparison and experimental verification”, IAEA Specialist’s Meeting on The Integrity of Pressure Components of Reactor Systems, Paks, Hungary, May 1992.
Brumovsky, M. (1996), “Comparison of PWR and WWER codes for reactor pressure vessel life assessment”, Workshop on Internacional Practices on Reactor Pressure Vessel Integrity Assessment”, August 1996, Rez, Czech Republic.
Brumovský M., (2003) “Unified Procedure for Lifetime Assessment of Components and Piping in WWER Nuclear Power Plants (VERLIFE). Final report” EU Contract No: FIKS-CT
Brumovsky M., , “VERLIFE Unified Procedure”, ATHENA Workshop, AMES Thematic Network EURATOM FP5, October 25-27, 2004, Rome, Italy
English C., Jendrich U., Karpunin N., Lomakin S., Prosvirin A., Schulz H., Wallin, K., (1999), “Licensing related assessment of RPV embrittlement of VVER 440/230 Units”, IAEA Specialist Meeting on Irradiation Embrittlement ans Mitigation, April 1999
Guinovart J, Langer R., Lidbury D., Wardle G., Wallin K., Houssin B., (2000), “Unified reference fracture toughness design curves for RPV steels”, EC DG XI Contract B7-5002/97/000809/MAR/C2

5. Introduction
Other paper included in other ODIN folders and on the literature are used (Cont)
Joly P., Houssin B., Gauthier J.P., Pelli R., Wardle G., Langer R., Kastner B., (1998), “Compendium of pressure vessel steels and weldments properties and data required for structural integrity analysis”, EC DG XI Contract B7-6340/95/000877/MARC/C2.
Karzov, G; Timofeev, B.; Chernaenko, T., “Database of RPV materials for brittle fracture assessment of NPP equipment”, 3º International Conference on Strength, Durability and Stability of Materials and Structures. SDSMS'03, Klaipeda (Lithuania), Sep 2003
Pelli R., Wallin K, Timofeev B., Blyumin A. (1997), “Crack initiation fracture toughness of eastern CrMoV and CrNiMoV reactor pressure vessel steels and welds” Final Report
Planman T., Wallin K. and Rintamaa R., ”Evaluating crack arrest fracture toughness from Charpy impact testing”, 14th International Conference on Structural Mechanics in Reactor Technology (SMIRT14) Lyon, France, August 17-22, 1997
Timofeev B. T., Karzov G. P., Blumin A. A., Anikovsky V. V., (2000) , “Fracture toughness of 15X2MFA steel and its weldments”, International Journal of Pressure Vessels and Piping 77 (2000) pp
Timofeev B. T., Karzov G. P., Blumin A. A., Smirnov V. I., (2000) “Determination of crack arrest toughness for Russian light water reactor pressure vessel materials”, International Journal of Pressure Vessels and Piping 77 (2000) pp
Wallin K., Törrönen K., Ahlstrand R., Timofeev B.T., Rybin V., Nikolaev V., Morozov A. (1989), “Theory Based Statistical Interpretation of Fracture Toughness of Reactor Pressure Vessel Steel 15x2MfA and its Welds”, 10th International Conference on Structural Mechanics in Reactor Technology (SMIRT10) Anaheim, CA, USA August 14-18, 1989

6. Initiation fracture toughness
A large number of fracture toughness results are presented by Finish and Russian researchers in SMIRT 10 conference [Wallin 1989].
Five different heats of the 15Kh2MFA base material and two different welds, one submerged arc weld and one electroslag weld.
Cooperative program between VTT and various research institutes in the former Soviet Union.
Both three point bend and compact tension with thickness ranging from 25 mm to 150 mm.
Fracture toughness of the 15Kh2MFA and welds can be described by the Master Curve.

7. Initiation fracture toughness
This database was later checked and updated by Siemens and VTT assisted by Russian researchers in the frame of different EC-DG XI contracts [Pelli 1997, Joly 1998, Guinovart 2000].
A totally of 803 fracture toughness test results were collected of VVER 440 and VVER 1000 RPV materials.
Was also used on IRLA project
In all cases, some of the fracture toughness experimental results are below the PNAE curve 3

8. Initiation fracture toughness
Prometey researchers [Timofeev 2000, Karzov 2003 and Karzov 2006] derived envelope curves
Base metal 2.5Cr-Mo-V steel
Weld metal 2.5Cr-Mo-V steel
KIC, KJC, МПам
В=25 мм
В=50 мм
В=100 мм
В=125 мм
В=16 мм
В=25 мм
В=50 мм
В=75 мм
В=100 мм
В=150 мм
KIC, KJC, МПам
FRACTURE TOUGHNESS OF RPV STEELS FOR WWER-440: TEST RESULTS AND BASIC CURVE

9. Initiation fracture toughness
Prometey researchers [Timofeev 2000, Karzov 2003 and Karzov 2006] derived envelope curves
Base metal 2Cr-Ni-Mo-V steel
Weld metal 2Cr-Ni-Mo-V steel
KIC, KJC, МПам
В=10 мм
В=12 мм
В=25 мм
В=30 мм
В=40 мм
В=50 мм
В=75 мм
В=100 мм
В=150 мм
KIC, KJC, МПам
В=10 мм
В=50 мм
В=75 мм
В=100 мм
В=150 мм
FRACTURE TOUGHNESS OF RPV STEELS FOR WWER-1000: TEST RESULTS AND BASIC CURVE

10. Initiation fracture toughness
Brumovsky [Brumovsky 1992] presented an experimental validation of lower bound curves for VVER RPV steels, 15Kh2MFA and 15Kh2NMFA and their welds

11. Initiation fracture toughness
VERLIFE [Brumovsky 1996, 2003, 2004].
Main goal of the project was a preparation, evaluation and mutual agreement of a "Unified procedure for Lifetime Assessment of Components and Piping in VVER Type Nuclear Power Plants“
This procedure should be based on former Soviet rules and codes and would be usable in nuclear power plants in Finland, Czech Republic, Slovak Republic and Hungary for Periodic Safety Reports and Components/Plant Life Management.
More than 1,200 data for VVER-440 RPV materials and more than 700 data for VVER-1000 RPV materials from different VVER countries were collected within this project
Analysis of this database again showed that the specifics Soviet fracture toughness reference curves are not conservative. Only generic curves are reliable as they cover practically all experimental data.

12. Initiation fracture toughness
15Kh2MFA Base metal 50
100
150
200
250
300
350
400
B=10
B=16
B=25
B=30
VERLIFE VVER-440
B=37.5/40
B=50
B=75
B=100
B=125
B=150
[KIC]3-G
[KIC]3-BM
KCJ, MPa.m0.5
-300
-200
-100
100
15Kh2MFA weld 50
100
150
200
250
300
350
400
-300
-200
-100
T - Tk0, °C
KCJ, MPa.m0.5
B=10
B=16
B=25
B=30
B=37.5/40
B=50
B=75
B=100
B=125
B=150
[KIC]3-G
[KIC]3-WM
200
T - Tk0, °C

13. Initiation fracture toughness
15Kh2NMFA base metals 50
100
150
200
250
300
-200
-150
-100
-50
T-Tk0, °C
Kcj, MPa.m0.5
B=10
B=25
B=30
B=40
B=50
B=75
B=100
B=150
[KIC]3
[KIC]BM
VERLIFE VVER-1000
15Kh2NMFA weld metals
100
200
300
400
-200
-150
-100
-50 50
T - Tk0, °C
Kcj, MPa.m0.5
B=10
B=25
B=50
B=75
B=100
B=150
[KIC]3
[KIC]WM

14. Initiation fracture toughness
Master Curve is validated for VVER 440 and VVER 1000 RPV materials
VERLIFE
For VVER RPV type steels and their welds, the following relation is suggested:
KJC5%=min exp(0.019(T-RTT0)); 200
where RTT0 is defined as T0+T0.

15. Crack arrest fracture toughness
The positive temperature gradient and attenuation of neutron radiation across the pressure vessel wall provides a mechanism by which initiated cracks may be arrested before they propagate through the wall.
So beside initiation fracture toughness KIC, crack arrest fracture toughness KIa it is necessary to perform a integrity assessment of the RPV.
In the ASME code crack arrest reference fracture toughness curve is included and used to determine the pressure-temperature limit curve of the vessel.
This type of reference curve is not included in the Soviet Code

16. Crack arrest fracture toughness
A suggested dependence of crack arrest fracture toughness is proposed by Timofeev [Timofeev 2000b]
To construct a robust reference temperature dependence of KIa it is necessary to carry out additional investigations

17. Crack arrest fracture toughness
Wallin et al [Planman 1997] have proposed a crack arrest master curve
Crack arrest reference temperature TKIa.
Can be determined by the analysis of the forces of a instrumented charpy test.

18. Crack arrest fracture toughness
Within VERLIFE [Brumovsky 2003] the temperature dependence of crack arrest fracture toughness may be obtained by:
[KIa]3= min  exp(0.020(T-Tk-30)); 200 or
[KIa]3= min  exp(0.019(T- RTT0)-60)); 200

19. Conclusions
A consistent fracture toughness data base in the start of life conditions exists VVER reactor pressure vessel steels
Russian researches and is based on the Tk reference transition temperature and new references fracture toughness curves are suggested to replace the curves of PNAE.
VERLIFE procedure and it is based on the Master Curve concept, using the RTT0 reference transition temperature.
In any case, if the approach of initial condition + shift due to irradiation + margin is applied, it is evident that the SOL toughness is needed, but if the approach is based on irradiated results + fluence projections (if needed) the initial state is not needed and the uncertainties are reduced.
So if irradiated fracture toughness specimens exist, with the application of the VERLIFE lower bound, the initial state of the RPV is not needed.
Regarding crack arrest data, more experimental data is needed in order to establish a crack arrest fracture toughness reference curve for VVER PRVs