Need for High Fluence RPV Reactor Surveillance Data for Long Term Operation

Transcription

1 Need for High Fluence RPV Reactor Surveillance Data for Long Term Operation William Server ATI Consulting Brian Hall Westinghouse Nathan Palm, Tim Hardin EPRI Randy Nanstad ORNL Degradation of Primary Components of Pressurized Water Cooled Nuclear Reactors: Current Issues and Future Challenges Vienna, November 5-8, 2013

2 What Happens at High Fluence? In the U.S., license renewal to 60 years of operation is approved for about 75% of the operating PWR fleet Activities are ongoing to investigate technical issues for extending the license life for an additional 20 years But, there is only a limited amount of power reactor surveillance data at fluences associated with 80 years The paucity of high fluence data has led to industry programs to significantly increase the amount of data over the next years EPRI Coordinated Reactor Vessel Surveillance Program (CRVSP) has been implemented EPRI PWR Supplemental Surveillance Program (PSSP) is being developed and implemented Coordination with activities funded by DOE including the Light Water Reactor Sustainability (LWRS) program 2

3 Previous Analyses of Irradiated Data Data at high fluences exist from test reactor experiments Much higher fluxes (typically 100X or more) Generally no direct materials link to power reactor surveillance data Mark Kirk has combined test and power reactor data Usually not measured Charpy transition temperature shift (TTS) Taken from many sources and material type sources (some do not relate to U.S. RPV steels) Comparison were made with the Eason, Odette, Nanstad, Yamamoto (EONY) embrittlement trend curve (ETC) prediction model (ORNL/ TM 2006/530) Kirk developed his own model, WR-C(5), Revision 1 (ASTM STP 1547) 3

4 Residuals of Test and Power Reactor Data Comparison with EONY Model From LWRS Newsletter, Issue 6, Dec

5 Comparison with EONY Model Underpredicted 5

6 New Comparison with only Existing U.S. PWR Surveillance Data Latest surveillance results (higher fluence) from the last 10 years were added to existing database Compare this database with three ETC prediction models Regulatory Guide 1.99, Rev. 2 [177 surveillance data values; developed in 1980s] EONY [approximately 750 power reactor surveillance data values from about ten years ago] as used in alternate PTS Rule (10 CFR 50.61a) Kirk s WR-C(5), Rev. 1 [combined test reactor and power reactor data from many sources] Reference: Materials Reliability Program: Material Selection for the PWR Supplemental Surveillance Program (PSSP) (MRP-364), EPRI, Palo Alto, CA

7 Broke Different Material Types into Chemistry Groups Welds 7

8 Material-Chemistry Subgroupings Form Plates SA-302BM, SA-533B1 Plate SA-302B Forgings SA-508 Welds Ni > 0.4% Welds Ni < 0.4% RVSP Materials RV Limiting Materials Ni Range Cu Group Cu Range Ni Range Cu Range < > All None is limiting None is limiting < > < > < >

9 Comparison for SA533B-1, Low Cu 9

10 Comparison for SA533B-1, Medium Cu 10

11 Comparison for SA533B-1, High Cu 11

12 Comparison for Forgings, Medium Cu 12

13 Comparison for Ni-Containing Welds with High Cu 13

14 Comparison for Low Ni-Containing Welds with Low Cu 14

15 Results of New Comparison Using Only U.S. PWR Surveillance Data Less high fluence data than used by Kirk, but trend does not seem as extreme as when many test reactor data are included The Regulatory Guide 1.99, Revision 2 model nonconservatively under-predicts some of the base metal measurements (most predominately for medium Cu forgings), but provides generally reasonable predictions for other material chemistry groups The WR-C(5), Revision 1 model tends to over-predict much of the data EONY tends to generally give reasonable predictions for all material chemistry groups 15

16 EPRI Coordinated Reactor Vessel Surveillance Program (CRVSP) CRVSP defers some capsule tests already planned in existing plant RVSPs, increasing fluences, but does not increase the number of capsule tests Data will be obtained over time (through 2025) but will not provide a large body of new data in the near future 16

17 EPRI PWR Supplemental Surveillance Program (PSSP) EPRI PSSP will Design/Fabricate/ Irradiate 2 supplemental surveillance capsules containing previously-irradiated PWR materials Reconstitute previously-irradiated specimens (per ASTM E1253) before re-irradiation Obtain 24 new high-fluence Charpy transition temperature shift measurements Materials selected based on information value to the PWR database PSSP development spread over 3 years, Goal: insert capsule(s) in 2015 Irradiate ~10 years in 2 PWRs Obtain data ~2025 Flux ~1.2 E+11 n/cm 2 /s (~0.35 n/cm 2 /year) thus adding ~3.5 E+19 n/cm 2 over 10 years Two irradiation temperatures to more closely match previous irradiation temperature 17

18 Capsule Design Overall geometry fits into standard Westinghouse 3-loop and 4-loop design capsule holder Contents 144 ASTM Type-A Charpy Impact specimens Dosimetry (Nb, Ni, Fe, Cu, Co) Melt wire temperature monitors (7 different temps) SiC as experimental temperature monitor 18

19 Materials Selection Method Existing broken CVN specimens of archived surveillance materials were catalogued Priority categories were defined within material-chemistry groups for PSSP screening based on: Discrepancy in ETC predictions between current and potential future ETCs Ability for these ETCs to predict measured data Hall, J. B., Server, W. L., Rosier, B., and Hardin, T., Comparison of Radiation Embrittlement Prediction Models to High Fluence U.S. Power Reactor Surveillance Data, 2013 ASME Pressure Vessels & Piping Conference, Paris, July 2013 Selection screening also included evaluation of: Data gaps, especially at high fluence Data that are already available Data that will become available from CRVSP Data that can be obtained in PSSP by adding ~3.5E19 n/cm 2 to existing broken specimens 19

20 Current Surveillance Data and Future CRVSP / PSSP Data Compared to RPV Fluences 20

21 PSSP Design and Planning Current Status Program makes use of archive irradiated material consistent with NRC s Generic Aging Lessons Learned report for license renewal (NUREG-1801) In process of obtaining permission to use materials for PSSP capsule from affected utilities Most materials are not vessel limiting materials and are unlikely to become limiting Discussions with prospective host plants have been initiated 21

22 High Fluence TTS Data from CRVSP and PSSP Fluence (n/cm 2 ) Data Points After Implementation of the CRVSP 1 Maximum Possible Data Points from the PSSP Total >3.0x >6.0x >8.0x >9.0x Assumes two data points per capsule (one weld and one base metal) from the CRVSP capsules 22

23 What about Material Test Reactors? Advantages of MTRs Obtain data quickly high flux to obtain high fluence in short time Obtain large amounts of data, including microstructural Variable control of irradiation temperature Different types of test specimens, possibly including fracture toughness Well characterized steels or model alloys to gain mechanistic insight Disadvantages of MTRs High flux provides different results in some materials depending upon flux-fluence conditions Often need to rely on correlations from Δhardness to ΔYS to ΔTT CVN to ΔK Jc due to limited irradiation space 23

24 Material Test Reactor (MTR) Irradiations Are 2-3 Orders of Magnitude Higher in Flux (Dose Rate) Need to know effects of dose rate After English 24

25 New Irradiation Experiment, UCSB ATR-2, is Now Underway in Advanced Test Reactor at INL Current RPV ETCs that under-predict TTS data from highly accelerated, short-time irradiations may be an artifact Research goal to develop models to accurately predict TTS for high ft, long-time (low f) RPV conditions using MTR data from actual surveillance materials and other steels and model alloys At a peak f 4x10 12 n/cm 2 -s, ft n/cm 2 can be achieved in a little more than one year Irradiations were started in June 2011 but operating delays at ATR have delayed completion to Fall 2013 After Odette 25

26 UCSB ATR-2 Key Design Features Irradiation at I-22 position with four temperature zones: 250, 270, 290 and 310 o C Active temperature control with variable He-Ar gas-gapmixture and monitor with 28 thermocouples Gd shielding of thermal neutron for reducing specimen activation After Odette 26

27 Large Number of Alloys and Specimens are Included in the UCSB ATR-2 Experiment Total of 180 RPV steel alloys including IVAR program (CM, L-series) and newly prepared slit melt model steels (SMMS), and commercial surveillance program welds and plates Specimen types 1000 Multi purpose disc coupons with 20 mm diameter 400 Miniature tensile specimens (SS-J2) in 20-mm diameter containers mm diameter disc compact tension (DCT) specimens (three alloys) After Odette 27

28 Microstructure Differences May Help Define Power Reactor vs. Test Reactor Microstructure techniques have evolved significantly in the last 15 years Atom probe tomography (APT) Small Angle Neutron Scattering (SANS) Advanced transmission electron microscopy (TEM) Positron annihilation line shape analysis (PALA) and positron lifetime (P-t) Combined isothermal or isochronal annealing with hardness and/or PALA Thermo-electric power (TEP) also called resistivity-seebeck coefficient (RSC) X-ray diffraction-scattering (XRDS) 28

29 APT Results for Low Cu, High Ni, Weld Metal at High ft Showing MNPs Ringhals Unit 4 Four slices through a 2 nm precipitate showing Ni-Mn-Si- Cu atoms These results are comparable to a non-cu, high Ni steel Further insight into these features for both power reactor and test reactor irradiations is being developed in cooperation with EPRI, UCSB (Odette), CRIEPI (Japan), and DOE LWRS 29

30 U.S. RPV Surveillance Steels in PSSP and Relation to Cooperative Programs Material Shielded Metal Arc Weld Linde 124 Weld Linde 1092 Weld Linde 1092 Weld Linde 0091 Weld Linde 80 Weld Linde 80 Weld SA533B-1 Plate SA533B-1 Plate SA508-2 Forging SA508-2 Forging Heat Number Cu (wt%) Ni (wt%) ATR-2 Irradiation (ft < E20 ) EPRI PSSP (expected ft ) Highest Existing/Future Surveillance (expected ft ) CRIEPI-EPRI AP (Surveillance ft ) ORNL AP (Surveillance ft) BOLA E E E P E E P E E E P E E A E E E E E19 5.8E E19 B E E E19 -- B E19 5.6E19/ 8.5E P E19 5.8E E19 123X167VA E E

31 Overall Summary Currently, there are limited U.S. power reactor surveillance data available at fluences greater than 4 x n/cm 2 (E > 1 MeV) for comparison with existing ETCs Additional data will be required to support extended operations beyond 60 years, where some plants are projected to have peak vessel fluences approaching 1 x n/cm 2 The EPRI CRVSP, the EPRI PSSP, the DOE Light Water Reactor Sustainability (LWRS) Program and the UCSB DOE-NE NEUP Program are interacting to provide a basis for a better mechanistic understanding of flux effects and the evolution of microstructure differences at high fluence between power reactor and test reactor irradiations Data generated in all of the US industry and government-funded programs can be used to validate or revise embrittlement trend correlations applicable to the high fluence regime before plants reach 60 years of operation 31