need for high fluence rpv reactor surveillance … for high fluence rpv reactor surveillance data...

Need for High Fluence RPV Reactor

Surveillance Data for Long Term Operation William Server Brian Hall

ATI Consulting Westinghouse

Nathan Palm, Tim Hardin Randy Nanstad

EPRI ORNL

Degradation of Primary Components of Pressurized Water Cooled Nuclear Reactors: Current Issues and Future Challenges

Vienna, November 5-8, 2013

2 © 2013 Electric Power Research Institute, Inc. All rights reserved.

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 10-12 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


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)


Residuals of Test and Power Reactor Data

Comparison with EONY Model

From LWRS

Newsletter,

Issue 6,

Dec.2011


Comparison with EONY Model

Under-

predicted


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. 3002000654. 2013.


Broke Different Material Types into Chemistry Groups

Welds


Material-Chemistry Subgroupings

Form

RVSP Materials RV Limiting Materials

Ni Range Cu Group Cu Range Ni Range Cu Range

Plates

SA-302BM, SA-533B1

0.44–0.68 < 0.10 0.03–0.09 0.41–0.67 0.03–0.24

0.10–0.17 0.10–0.15

> 0.17 0.19–0.25

Plate

SA-302B

0.056–0.20 All 0.09–0.20 None is

limiting

None is

limiting

Forgings

SA-508

0.68–0.86 < 0.06 0.01–0.057 0.68–0.90 0.04–0.17

0.06–0.12 0.06–0.11

> 0.12 0.13–0.16

Welds

Ni > 0.4%

0.52–1.26 < 0.10 0.02–0.055 0.52–1.04 0.03–0.34

0.10–0.23 0.15–0.23

>0.23 0.23–0.39

Welds

Ni < 0.4%

0.04–0.22 < 0.10 0.01–0.09 0.13–0.15 0.13–0.15

0.10–0.23 0.13–0.21

>0.23 0.24–0.41


Comparison for SA533B-1, Low Cu


Comparison for SA533B-1, Medium Cu


Comparison for SA533B-1, High Cu


Comparison for Forgings, Medium Cu


Comparison for Ni-Containing Welds with High Cu


Comparison for Low Ni-Containing Welds

with Low Cu


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 non-

conservatively 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


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


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, 2012-2014

• Goal: insert capsule(s) in 2015

• Irradiate ~10 years in 2 PWRs

– Obtain data ~2025

– Flux ~1.2 E+11 n/cm2/s (~0.35 n/cm2/year) thus adding ~3.5 E+19 n/cm2 over 10 years

– Two irradiation temperatures to more closely match previous irradiation temperature


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


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/cm2 to existing broken specimens


Current Surveillance Data and Future CRVSP /

PSSP Data Compared to RPV Fluences


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


High Fluence TTS Data from CRVSP and PSSP

Fluence (n/cm2)

Data Points After

Implementation of

the CRVSP1

Maximum Possible

Data Points from

the PSSP

Total

>3.0x1019 58 25 83

>6.0x1019 24 13 37

>8.0x1019 10 6 16

>9.0x1019 4 4 8

1 Assumes two data points per capsule (one weld and one base metal) from the CRVSP capsules


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 ΔTTCVN to

ΔKJc due to limited irradiation space


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


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 ≈ 4x1012 n/cm2-s,

ft ≈ 1020 n/cm2 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


UCSB ATR-2 Key Design Features

• Irradiation at I-22 position with four temperature zones: 250, 270, 290 and 310oC

• Active temperature control with variable He-Ar gas-gap-mixture and monitor with 28 thermocouples

• Gd shielding of thermal neutron for reducing specimen activation

After Odette


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

– 42 20-mm diameter disc compact tension (DCT) specimens (three alloys)

20.

0

After Odette


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)


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


U.S. RPV Surveillance Steels in PSSP and Relation to

Cooperative Programs

Material 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)

Shielded

Metal Arc

Weld

BOLA 0.03 0.9 1.2E20 8.73E19 8.73E19 --

Linde 124

Weld 4P4784 0.04 0.95 1.0E20 6.54E19 -- --

Linde 1092

Weld 1P3571 0.22 0.72 9.1E19 5.62E19 5.62E19 --

Linde 1092

Weld 1P3571 0.36 0.78 -- 6.11E19 6.11E19 --

Linde 0091

Weld 33A277 0.14 0.19 1.2E20 8.47E19 8.47E19 --

Linde 80

Weld 71249 0.29 0.6 -- 1.29E19 -- --

Linde 80

Weld 61782 0.24 0.52 -- 9.3E19 5.8E19 -- 1.7 - 5.8 E19

SA533B-1

Plate B7212-1 0.19 0.6 1.2E20 8.73E19 8.73E19 --

SA533B-1

Plate B9004-2 0.05 0.56 9.1E19

5.6E19/

8.5E19 -- --

SA508-2

Forging 125P666 0.05 0.69 -- 9.3E19 5.8E19 -- 1.7 - 5.8 E19

SA508-2

Forging

123X167VA

1 0.06 0.75 -- 5.62E19 5.62E19 --


Overall Summary

• Currently, there are limited U.S. power reactor surveillance data available at fluences greater than 4 x 1019 n/cm2 (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 1020 n/cm2

• 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

need for high fluence rpv reactor surveillance … for high fluence rpv reactor surveillance data...

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