Idea Transcript
USE OF REACTOR PRESSURE VESSEL SURVEILLANCE MATERIALS FOR EXTENDED LIFE EVALUATIONS USING POWER AND TEST REACTOR IRRADIATIONS
W. L. Server, ATI Consulting R. K. Nanstad, ORNL G. R. Odette, UCSB
What to Expect
Introduction and importance Brief description of U.S. RPV surveillance programs Long term operation programs in the U.S. UCSB/ORNL ATR-2 irradiation project and commercial RPV surveillance materials Summary
Introduction
RPV is first line of defense against release of radiation during an operating accident in LWRs Fracture toughness of RPV is diminished over time due to neutron radiation embrittlement Current regulations take embrittlement into account for operating life; e.g.., pressurized thermal shock (PTS) for PWRs Extended operating life beyond 60 years requires more irradiation data to assure continued safe operation
Key Issue – High ft Data Gap
For 80 years of operation (and even in some cases for 60 year life) fluence (ft) in the RPV can reach or exceed 5 x 1019 n/cm2 (E > 1 MeV) Current PTS embrittlement model (EONY) has very little surveillance data for ft > 3 x 1019 n/cm2 More surveillance data will be generated in the future, but concern exists that there may be an acceleration in embrittlement at high ft – longer time exposure at RPV operating flux (f) levels
EONY Model Prediction Error as a Function of ft plus 2 Sigma Bounds
Mixture of Test and Power Reactor Data
Data shown was a mixture of test reactor and power reactor data Predominantly test reactor data above ft of 3 x 1019 n/cm2 Part
of non-conservatism likely is due to an artifact of high f irradiation Physical understanding and more data with matching ft for test and power reactor irradiations is needed
U.S. RPV Surveillance Programs
All U.S. plants have an RPV surveillance program following a version of ASTM E 185 and Appendix H of 10 CFR Part 50 – original intent was for design validation, but data now used to generate embrittlement trend prediction model Current program will generate data for current licensed life, but data at high ft are needed soon to assess potential enhanced embrittlement 70%
of plants have an extended license life for 60 years, and all remaining plants intend to seek extension Very little surveillance data exist at ft above 5 x 1019 n/cm2
Industry Surveillance Program Adjustments
Coordinated reactor vessel surveillance program (CRVSP) just initiated Adjusts
plant-specific capsule withdrawal to assure high ft data are obtained more efficiently Does not generate more data than current surveillance programs Does not greatly enhance obtaining data in a reduced time frame
More high ft data are needed in a more timely manner
Possible Supplemental Program
In order to gain more high ft data in the shortest time frame possible, a PWR supplemental surveillance program (PSSP) is being considered PSSP
would utilize broken irradiated Charpy specimens to be irradiated to a higher ft in a host reactor Reconstituted Charpy specimens would then be used to measure transition temperature shifts
Concurrent option would be to combine high ft data from test reactor irradiations with appropriate adjustments for f
Other Industry Programs
EPRI Long Term Operation (LTO) program Originally focused on defining research needs for operation beyond 60 years Now part of the EPRI base funding and coordinated with existing EPRI programs including RPV integrity
Cooperative “Nuclear Plant Life Extension Demonstration (NPLED) Project” Constellation Energy Nuclear Group (CENG), EPRI LTO, and DOE Light Water Reactor Sustainability (LWRS) Programs combined under this joint agreement Two key CENG plants are participating (operating in LR)
R.E. Ginna – PWR, two-loop, 580 MW Nine Mile Point Unit 1 – BWR-2, Mark 1, 620 MW
R.E. Ginna Surveillance Program
Five of the original six surveillance capsules have been tested; forgings and weld metal in each Last tested capsule had ft = 5.8 x 1019 n/cm2 Measured Charpy 41 J shift vs. EONY prediction:
Linde 80 weld metal – Measured121oC; EONY 111oC EONY under-predicts by 10oC A508-2 forging – Measured 42oC; EONY 29oC EONY under-predicts by 13oC A508-2 forging – Measured 51oC; EONY 29oC EONY under-predicts by 22oC
A couple of broken Charpy halves from the three highest ft capsules for weld and one forging material have been sent to ORNL for atom probe tomography (APT) and small angle neutron scattering (SANS) as part of DOE LWRS
R.E. Ginna Surveillance Results Compared to EONY & Kirk Models
Atom Probe Tomography (APT) of Mn-Ni Irradiation Clusters in a Model Alloy Mn-Ni clusters, predicted in the 1990s , also have been identified in RPV steels (with little or no Cu) and may act as an additional embrittlement mechanism, particularly at high ft
Test Reactor Irradiations at ATR-2
UCSB-ORNL joint project funded by DOE and using ATR-2 under the National Scientific User Facility (NSUF) With a peak f ≈ 3.3 x1012 n/cm2-s at I-22 position, ft ≈ 1020 n/cm2 can be achieved in 1.2 years Temperature zones: 250, 270, 290 and 310 oC Active temperature control with variable He-Ar gasgap-mixture and monitored with 28 thermocouples Gd shielding of thermal neutron for reducing specimen activation
Large Number of Alloys & Specimens Included in 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 and new split melt alloys Specimen types ≈ 1000 Multi purpose disc coupons with 20 mm diameter ≈ 400 Miniature tensile specimens (SS-J2) in 20-mm diameter containers 42 20-mm diameter disc compact tension (DCT) specimens (three alloys)
20.0
Overlap of Existing Test Reactor Data with ATR-2 Experiment
Selection of Surveillance Materials
Highest ft materials tested in PWR surveillance programs Covers range of materials in operating PWRs (welds, plates, and forgings) One weld wire heat from two different weldments with greatly different copper contents (1P3571) Non-irradiated archive material was readily obtainable
Surveillance Materials Added to ATR-2 Plant
Material
Heat Number
Cu-Ni Composition, wt%
Farley Unit 2
SMAW
BOLA
0.03-0.9
Farley Unit 2
Plate, SA533B-1
C7466-1
0.2-0.6
V.C. Summer
Linde 124 Weld
4P4784
0.05-0.91
Kewaunee
Linde 1092 Weld
1P3571
0.22-0.72
Maine Yankee
Linde 1092 Weld
1P3571
0.36-0.78
Farley Unit 1
Linde 0091Weld
33A277
0.14-0.19
Beaver Valley Unit 2
Plate, SA533B-1
B9004-1
0.05-0.56
Kewaunee
Forging, SA508-2
B6307-1
0.06-0.75
Turkey Point Unit 4
Linde 80 Weld
71249 (SA1094)
0.29-0.6
Capsule Layout
1 2
3
180 materials plus different multiples 1661 specimens in 13 capsules 7 dosimetry modules 7 temperature/f variations 250 - 310 ºC 4 – 19x 1019 n/cm2 (for ≈ 390 FPI days) Nominal Target ft
Capsule ID
Materials
Target Temp.
UCSB-1
coupon/tensile
290 ¼C
low 4.2
UCSB-2
coupon/tensile
290 ¼C
low 6.2
UCSB-3
coupon/tensile
290 ¼C
med 8.8
UCSB-4
coupon/tensile
270 ¼C
med 10.3
UCSB-5
coupon/tensile
250 ¼C
med/hi 10.9
UCSB-6
DCT
290 ¼C
hi 11.7
UCSB-7
coupon/tensile
290 ¼C
hi 12.2
UCSB-8
coupon/tensile
290 ¼C
hi 12.3
UCSB-9
DCT
290 ¼C
hi 11.7
UCSB-10
coupon/tensile
310 ¼C
med/hi 11.0
UCSB-11
coupon/tensile
290 ¼C
med 9.8
UCSB-12
DCT
290 ¼C
low 7.6
UCSB-13
coupon/tensile
290 ¼C
low 5.5
(x1019n/cm2)
4 5
6
7
8 9
10 11 12
ATR-2 Coupon & Tensile Summary 290°C high flux
290°C med flux
disc coupons
31split melt commercial model alloys
78
10 simple model alloys
30
16 RPV plates/forgings
34
12
35
26 RPV welds
71
57
61
UCSB/ORNL
(surveillance)
290°C low flux
250°C
270°C
310°C
disc coupons
disc coupons
disc coupons
68
7
36
42
9
4
3
3
13
35
3
10
9
41
50
5
23
21
250°C
270°C
310°C
tensiles
disc coupons
tensiles
disc coupons
69
72
71
290°C high flux
290°C med flux
tensiles
2
290°C low flux
disc coupons
tensiles
disc coupons
tensiles
disc coupons
tensiles
disc coupons
disc coupons
disc coupons
56 RR model alloys & H.T. variations
56
17
106
16
115
15
56
9
10
12 RR archival crossover welds & plates
25
Rolls Royce
290°C high flux
Other participants 5 Bettis plate & weld alloys 13 CRIEPI alloys
disc coupons
25
290°C med flux disc coupons
22
290°C low flux disc coupons
5 13
13
13
12
250°C
270°C
310°C
disc coupons
disc coupons
disc coupons
10
5
5
13
13
ATR-2 Fracture Matrix Three sets of disc compact tension specimens, corresponding tensile specimens and multi-purpose coupons
20 mm dia. disc compact tension specimen
D.C.T. matrix
Irrd. Condition
Specimen set
Palisades B weld
290°C, 3.5 E12
14 DCT, 19 tensiles, 3 coupons
UCSB forging (C17 as tempered)
290°C, 3.5 E12
14 DCT, 18 tensiles, 4 coupons
UCSB forging ( LP as tempered)
290°C, 2.1 E12
17 DCT, 17 tensiles, 1 coupon
Multi Purpose Coupons Majority of coupon specimens are in 2 cm diameter disc form; precision punched, ground and polished on both faces and laser engraved with alloy code and serial number:
C19
-Microhardness -Shear punch tests -Atom Probe / LEAP
07
-TEM 0.5mm 2cm
-Neutron & X-ray scattering spectroscopy
Tensile Specimens 16
1.2
4
5
0.5
R1.4
Flat tensile type SSJ2 all dimensions mm
18 tensiles compressed in fitted pocket and capped
Small Specimen Loading Design Small (8mm dia.) discs: three stacks of 10 pressed into holder
Bettis 1cm sq coupons: stack of 5 compressed by lid
Dosimetry wire canisters: pressed into dummy
Advanced Microstructure Characterization Tools to Be Applied
Atom probe tomography (APT) Small angle neutron scattering (SANS) X-ray diffraction-scattering (XRDS) Resistivity-Seebeck coefficient (RSC) Positron annihilation spectroscopy (PAS) Transmission electron microscopy (TEM)
ATR-2 Capsule Status Test assembly completed in late spring 2011 and installed in ATR-2 in May 2011 Irradiation began on June 7, 2011 and will achieve ft = 0.9 1020 n/cm2 in autumn of 2012 Thermocouple monitors show specimens are generally being irradiated at or close to target temperatures
Summary
Plans to operate PWR plants to 80 years or more will require RPV surveillance data at high ft to assure integrity Current surveillance programs have been adjusted and enhanced to generate key data for 60 years, and now consideration is being given for 80 or more years; but the time horizon is at least 12 years Test reactor irradiations have been initiated with key RPV and model alloy steels, which include surveillance program steels irradiated in current power reactor surveillance programs to high ft All of these data are crucial in understanding radiation embrittlement mechanisms and to enable extrapolation of irradiation effects on toughness properties for extended time periods Potential methods for adjusting higher f test reactor data to predict power reactor vessel conditions are expected