Status of the Master Curve Fracture Toughness Evaluation Method using Miniature C(T) Specimens

Transcription

1 Status of the Master Curve Fracture Toughness Evaluation Method using Miniature C(T) Specimens Central Research Institute CRIEPI of Electric Power Industry Masato Yamamoto and Naoki Miura Oct. 24 th, 2017 Fourth International Conference on Nuclear Power Plant Life Management 1

2 The Master Curve (MC) method A sophisticated fracture toughness evaluation method based on statistical study at ductile brittle transition region, proposed by Kim Wallin Testing method was codified as ASTM E1921 or JEAC 4216 Relevance of the MC method had been verified through IAEA CRP-8 Employed as new RPV integrity evaluation methods IAEA TR-429, IAEA TECDOC-1631 ASME Code case N-629, N-631, N-830 JEAC 4206 Oct. 24th,

3 Advantage of the Master Curve method initial fracture toughness by drop-weight tests Relationship between Charpy shift and fracture toughness shift RPV Surveillance specimen (Charpy) ( mm) Charpy absorption energy before irradiation after irradiation Shift in Charpy energy Temperature Fracture 破壊靭性 toughness, MPa m Existing surveillance program 50 Temperature toughness relationship 温度, Temperature No C(T) specimens for the Master Curve evaluation are installed in the surveillance capsules Fracture toughness can be directory obtained by minimum 6 to 8 C(T) specimens. Fracture 破壊靭性 toughness, MPa m Direct evaluation of temperature-toughness trend by small number of specimens 温度, Temperature Master Curve fracture toughness evaluation by Mini-C(T) specimens Oct. 24th,

4 The Master Curve + Miniature C(T) specimens initial fracture toughness by drop-weight tests Relationship between Charpy shift and fracture toughness shift RPV Surveillance specimen (Charpy) ( mm) Charpy absorption energy before irradiation after irradiation Shift in Charpy energy Temperature Fracture 破壊靭性 toughness, MPa m Existing surveillance program 50 Temperature toughness relationship 温度, Temperature Fracture 破壊靭性 toughness, MPa m Direct evaluation of temperature-toughness trend by small number of specimens The Master Curvemethod is 150 capable of the specimen size 100 correction. We can use very 50 small specimens if the 8 miniature C(T) specimens appropriateness of test ( mm) can be machined from techniques are confirmed a pair of broken Charpy halves Temperature Master Curve fracture toughness evaluation by Mini-C(T) specimens 温度, Oct. 24th,

5 WhatistheMini-C(T) specimen? Dimension 4mm thickness C(T) specimen, whose dimensions conform to the Master Curve fracture toughness standard, ASTM E1921. Specimen size (4 x 10 x 9.6 mm) Small enough to be machined maximum 8 specimens from a broken pair of acharpy specimen. Usage of Mini-C(T) specimen The Master Curve method can compensate the specimen size effect. Theoretically Mini-C(T) specimens can be used for the Master Curve evaluation. B (4±0.08) 2.2± ± N ( ) D (φ2±0.04) 2H (9.6±0.08) 0.8 at side surface a 0 (4±0.4) W (8±0.04) L (10±0.08) Oct. 24th,

6 Development of Mini-C(T) technique Reference temperature, To Miura, Soneda, ASME J. of PVT ,(2010) RPV steel base metal Consistency of toughness between Mini-C(T) and larger specimens Utilization in surveillance program T o, degc Cumulative probability ln(ln(1/(1-p))) Toughness ln(k Jc(1Teq) -20) : Valid :Invalid due to improper control mode :Invalid due to insufficient number of specimen A1 A2 A3 B1 B2 B3 C1 C2 D1 D2 E1 E2 E3 F1 G1 G2 H1 H2 H3 H4 H5 I1 I2 I3 Round robin test for confirmation of reproducibility Confirmatory study using irradiated material and / or actual RPV material Oct. 24th, 2017 Standardization of test procedure 6

7 Requirementforcapsuleretrieval EFPY Present Surveillance program (JEAC 4201) ΔRT NDT < ΔRT NDT < ΔRT NDT < ΔRT Operating year Special Inspection for 60yrs operation Additional requirement by draft NRA review document for JEAC Once before but close to 40yrs Special 1 Special 2 Once between 40 to 50 yrs Additional 1 Once between 40 to 50 yrs Additional 2 Once between 50 to 60 yrs Oct. 24th,

8 CONSISTENCY OF FRACTURE TOUGHNESS BETWEEN MINI-C(T) AND LARGER SPECIMENS Oct. 24th,

9 T 0 obtained using various size of specimens (Miura et al., ASME Journal of PVT Vol ) 4T-C(T) (a) SFVQ1A forging Appropriateness of use of Mini-C(T) specimens for the Master Curve evaluation was confirmed for 1 forging and 2 plate un-irradiated RPV steels 2T-C(T) 1T-C(T) 0.5T-C(T) Mini-C(T) Oct. 24th,

10 ROUND ROBIN TEST Oct. 24th,

11 Cumulative probability ln( ln(1/(1-p))) Reference temperature T 0, degc Fracture toughenss ln(k Jc(1Teq) -20) Mini-C(T) round robin test summary A1 A2 A3 B1 B2 B3 C1 C2 D1 D2 E1 E2 E3 F1 G1 G2 H1 H2 H3 H4 H5 I1 I2 I3 Equivalent To between 1T-C(T) and Mini-C(T) specimens. Consistent results among the participants. Purpose: Ensure the reproducibility of T o evaluation on Mini- C(T) specimens(rpvbase metal unirradiated) machined and provided from CRIEPI Participants: Kyoto-Univ., JAEA, Toshiba/Hitachi GE/NFD, MHI/NDC, ORNL(USA), EPRI(USA), Westinghouse(USA), VTT(Finland), UJV(Czech), HZDR(Germany), SCK CEN(Belgium), CRIEPI : Valid :Invalid due to improper control mode :Invalid due to insufficient number of valid data Oct. 24th,

12 Organi zation Block No. dk/dt, MPa m 0.5 /sec Test temperature selection for Mini-C(T) Master Curve evaluation Test temperature for each specimen, C A B C D E F Fracture toughness, MPa m Reference temperature T T 0, C o, C Every participant could determine proper test temperature for valid evaluation. : Valid : Invalid Error bar: standard deviation of T 0 specified in ASTM E e1 Appendix X4.2 Am Bm Cm Dm Em Fm Aa Ba Fa 8 specimens from 1/4-T and 3/4-T location 4T-C(T) 2T-C(T) 1T-C(T) 0.4T-C(T) All specimens from single block Larger specimens [7] Oct. 24th,

13 STANDARDIZATION OF TEST AND EVALUATION METHOD Oct. 24th,

14 Change in geometry and tolerance requirement Tolerant requirement in former standard Standard deviation of T o, o C Tolerance 0.05W or 0.10W Former standard Tolerance 0.13W Revised standard Possible scatter in T o Change in notch height and tolerance requirements Notes and suggestions for usage of small specimens JEAC Revised tolerant requirement (0.1mm in Mini-C(T) = 0.13W) ASTM E a Oct. 24th,

15 Revision history JEAC 4216 add Mini-C(T) specimen as a recommended specimen shape for the Master Curve evaluation in 2015 revision. ASTM E1921 changed the notch shape requirement in 2016 revision, and mitigated tolerance requirement in 2017 revision. Oct. 24th,

16 ONGOING CONFIRMATORY STUDY USING IRRADIATED MATERIALS Oct. 24th,

17 Ongoing METI project for confirmation of applicability of Mini-C(T) specimens to irradiated materials Purpose Ensure the applicability of Mini-C(T) test technique to irradiated materials. Accumulate the knowledge base of fracture toughness distribution in thickness direction of RPV steels. 1. Investigation on irradiated JRQ material Mini-C(T) toughness evaluation on irradiated European standard reference material, JRQ, which has toughness characterized by both of initial distribution and neutron attenuation effect. 2. Mini-C(T) toughness evaluation on low upper shelf weld metal Linde80 Ensure the applicability of Mini-C(T) technique for low upper shelf material, which is recognized as a challenging material for small specimen toughness evaluation. Cladding Fluence level Charpy shift due to irradiation( T 41J ) Distribution of initial T 41J Distribution of T 41J after the irradiation Base Metal RPV beltline Curve not incorporated initial T 41J distribution (current Surveillance) Curve with initial distribution incorporated Location in thickness direction Oct. 24th, 2017 AESJ 2017 fall meeting, C

18 JRQ material and Mini-C(T) specimen IAEA reference material JRQ (SA533B Cl. 1 Plate) irradiated in previous EPRI MRP Original layer Irradiated position Fluence, x10 19 n/cm Distance between IS and irradiated position, mm Inner surface ¼ T Two laboratories were separately carried out Specimen machining Fatigue pre-cracking Master Curve testing Outer surface Oct. 24th,

19 Curve not incorporated initial T41J distribution (current Surveillance) T o comparison for each layer Fluence X10 19 n/cm 2 20 T L1P1 L2P3 L3P4 L4P6 Lab Lab Lab Cladding Fluence level Charpy shift due to irradiation( T 41J) Distribution of initial T 41J Distribution of T 41J after the irradiation RPV beltline Base Metal Curve with initial distribution incorporated Location in thickness direction Oct. 24th,

20 Fracture toughness, MPa m Mini-C(T) application on low upper shelf weld metal, Linde 80, in irradiated state Mini-C(T) Linde 80 (WF-70) T o = 27 o C Limit to elastic crack extension in the present dataset Equivalent MC between Mini-C(T) and larger specimens Temperature, Linde 80 weld metal retrieved from unused Midland NPP RPV beltline weld Fluence(Irradiated in HSST project) n/cm 2 (>1MeV),288 : Present study : Larger specimen result in letrature Excellent agreement between Mini-C(T) and larger specimens NUREG/CR-5736 Oct. 24th,

21 Summary Mini-C(T) Master Curve method is one of the promising options for increasing demand of frequent and accurate toughness evaluation Technology basis for the test technique was established and testing standard has been revised to allow the use of Mini-C(T) specimens. Confirmatory study with irradiated material is ongoing. Oct. 24th,