On Center for Nondestructive Evaluation...

Center for Nondestructive EvaluationOn-line Monitoring for PassiveOn line Monitoring for Passive Structures in Nuclear Power Pl tPlantsL d J B dLeonard J. BondDirector, Center for Nondestructive EvaluationEvaluation

September 3, 2012

IOWA STATE UNIVERSITY• College of Engineering

• 7,400 students• Founded 1858: 31,000 students• Home of DOE’s Ames

• 2011 Nobel Prize• Dan Shechtman

Laboratory• Highly ranked graduate

programs:(chemistry)• IPRT ‒ Institute

programs: College of Veterinary Medicine and College ofPhysical

Research & t h l

Medicine and College of Engineering,

technology

P tt d Whit• Pratt and Whitney ‒Center of Excellence (2012) http://www.cnde.iastate.edu/

Center for Nondestructive Evaluation

(2012)• CNDE ‒ NSF I/U CRC

• Founded 1985

Presidential visit August 28, 2012


IOWA STATE UNIVERSITY - CNDECNDE NSF I/U CRC (1985)• CNDE ‒ NSF I/U CRC (1985)• 15 industry sponsors

IHI E i i & T t

• Applied Sciences Complex - II

• IHI Engineering & Toyota• 17 professional staffAffili t d f lt & d t• Affiliated faculty & graduate studentsMore than $5M in equipment• More than $5M in equipment

• Modeling & simulation codesHome for: World Federation• Home for: World Federation NDE Centers & Int. Forum Reactor Aging ManagementReactor Aging Management (Prof. T. Shoji Chair)

• NDE Minor (BS) and an On-line http://www.cnde.iastate.edu/


( )Graduate Certificate in NDE

Outline• Introduction/background

• US Nuclear Fleet• License extension

• Can monitor let us get to 80 years?Can monitor let us get to 80 years?• SSC ‒ condition monitoring• Degradation & precursors• Degradation & precursors• AMP’sM it i li t i f t bl• Monitoring ‒ listening for trouble

• Prognostics• Challenges & Conclusions• Acknowledgements


US Nuclear Fleet• US: 104 operating plants

• 10% installed capacity0% a d apa y• 20% of electricity generation

• Average capacity factor ~91%Outages reduced from more than• Outages reduced from more than 100 to less than 40 days

• 135 power uprates: 5.8 GWe• 67 projects planned (@$2-500M)

• Since 1990 equivalent of 29 new q1 GWe reactors added

• NRC Post-Fukushima Reviews• Task force recommend actions• Task force recommend actions to enhance safety.

U.S. Nuclear Industry Capacity Factors1971 – 2011, Percent


Delayed & New Build ‒ PWR’sy• Brown Ferry #1 - re-start --- 2007• Watts Bar #2 - complete --- 2013

TVA to complete Bellefonte #1 2020• TVA to complete Bellefonte #1 -‒ 2020• 55% complete

• Vogtle (# 3 and 4)• US Nuclear Regulatory Commission has g y

completed its Final Safety Evaluation Report (FSER) for a limited work authorization (LWA) and Combined Licenses (COL) for the proposed VogtleUnits 3 and 4 reactorsUnits 3 and 4 reactors. (August 11, 2011)

• VC Summer (# 2 and 3)• 1st on line 2016


• NRC approval March 2012

New Degradation Processes Found in U S Nuclear Power Plants Roughly EveryU.S. Nuclear Power Plants Roughly Every 7 Years (Wilkowski, 2002)

2000

2010

1980

1990

2000ar

)

1960

1970

1980

Dat

e (y

ea

1940

1950

1930Vibrationfatigue

TP304IGSCC

Corr.-fatigue

Erosion-corr.

MIC TP347IGSCC

PWSCC


U.S. Pipe Failure Data by Degradation Mechanisms and Other CausesMechanisms and Other Causes (Lydell 2007)

21.4%

18.7%

32.5%

Vibration Fatigue (incl. Fretting)

Stress Corrosion Cracking

Flow Accelerated Corrosion

1.5%

6.5%

14.8%

Thermal Fatigue

Design & Construction

Corrosion (Crevice, MIC, Pitting)

0 8%

0.8%

1.4%

%

Water Hammer

Over-stressed / Over-pressurized

Erosion-Cavitation

Thermal Fatigue

0.4%

0.7%

0.8%

Unreported

Human Error

Water Hammer

5164 reported failures

0.1%

0.3%

0% 5% 10% 15% 20% 25% 30% 35%

Severe Weather (Freezing)

Corrosion Fatigue


Trend Over Time: Fewer Small Failures, Increasing Large and More Catastrophic g g pFailures

• Aging US nuclear fleet –will continue to operate beyond the initial design lif f 40 t 60life from 40 to 60 years and eventually to 80+ yearsyears

• Need capacity factor 90%+ for economics and maintain safety

• Deploy monitoring –avoid surprises andavoid surprises and the unknown!


License Extensions for Existing Fleet: Longer Term Operation (LTO)

• 73 plants granted extensions (40-60yr)60yr)

• Majority expected to extend life ‒ 18 applications pendingapplications pending

• 10 plants have entered LTOEquipment upgrades• Equipment upgrades

• Aging Management Plans• Active componentsp

• Maintenance rule and CBM• Passive Components

CRITICAL QUESTION WHAT WILL LIMIT PLANT LIFE?• In-service inspections

* NEI and NRC data January 201

CRITICAL QUESTION WHAT WILL LIMIT PLANT LIFE?EPRI, NRC & DOE LWRS Program seeking to answer question by

2020


y2020

US Fleet ‒ 2nd License Extension (60-80 years) ‒ Decision Window -( y )2020*Available Research Window Supporting

Utility and Regulator Plant Life Extension Decisions

(2009 2019)(2009 - 2019)

Key Utility Decision: Build new generation vs. extension of existing nuclear plant lifetimes

2020 Utility Decision Consequences: Industry-Wide Loss of Clean Power Generation from

Financial Markets / PSC / PUC Influences on Stock Pricing, Rates of Return, Capital Recovery and Utility Valuation

Utility Action: First Publically Discussed

Date of Utility Submission for 20 Year Life Extension

2010 2015 2020 2025 2030 2035

Wide Loss of Clean Power Generation from 25% of Existing Nuclear Plants With 20 Year

Life Extension

New Generating Plant Licensing, Construction and Startup Activities

Key Utility Action: Create Plant License

Extension NRC Submittal

Utility Action: First Actionable Date of Utility Submission for 20

Year Life Extension Consequences Path

Start of Industry / DOE / NRC Collaborative Research Programs

Prioritized to Importance and

Duration

Power Generation Basis: Upgraded Existing Fleet;

Future Power Generation

Key Utility Decision : Risk & Cost / Benefit Analyses

Prior

Initial Loss of Clean Power Generation from Existing

Nuclear Plants With 20 Year Life Extension

Life Extension Research Programs: Materials Aging and Degradation

Advanced Inspection and Evaluation

Consequen

Consequences Path

2040 New Nuclear Plants; New Coal Plants Alternative Energy Sources

2020 Utility Decision Consequences Extending 60 - 80 Years: Power Sourcing Reliability; Long Term Environmental Influences; Consumer Economics;NRC Regulatory Requirements re: Confirmatory Research on Aging

(Public Health and Safety Oversight)

Research Integration

Advanced Inspection and Evaluation Alternate Cooling Technologies Concrete and Structural Aging Plant Component Aging

nces Path

Applications Pathway to Utility Actions and Decisions 2015 - 2020

4/1/2008

Utility Financial Standing(Public Health and Safety Oversight)

NRC Regulatory Oversight of Existing Nuclear Plants, New Construction, and Legacy Sites

*US NRC – Amy Hull


US C y u

Can condition monitoring help keep nuclear power operating to p p p g80 years?

IEEE Spectrum – August 2012


p g

Motivation for Structural Health Monito ingMonitoring• Periodic NDE methods challenged by aging

tsystems• Frequency of inspection and inspection technology need t b i d i li ht fto be reviewed in light of known degradation mechanisms

Condition based• Condition-based maintenance philosophies, on-line

i i dmonitoring and diagnostics can reduce operation andoperation and maintenance (O&M) costs

• Digital systems give h d f ti lit

Nuclear Power Plant Systems


enhanced functionality

Light Water Reactor ‒ Life Extension

• Past Experience: • Majority of component failures

• Active components ‒ e.g., valve not operating on command

• Passive components: service degradationp g• Active components managed through maintenance programmaintenance program

• Passive components managed through periodic inspection (aging management plan)periodic inspection (aging management plan)


Damage Development with Time: Differentiation Between Reactive and Proactive ActionsBetween Reactive and Proactive Actions

Goal is to proactively address potential future degradation in ”

operating plants to avoid failures and to maintain integrity, operability and safety

“Dam

age

Reactive Proactiveactions

Structural Integrity Limit

Time

NDE Resolution Limit

“N ” Time“Now”

Move beyond philosophy of “Find and Fix”: Finding damage at an outage is expensive – longer outages – more inspection


NDE and On-line Monitoring ‒ LWR Passi e ComponentsPassive Components

• Degradation for LB-60 mechanisms being

On-line monitoring sensorsprovide data as a function ofmechanisms being

identified • MIT ‒ materials issues

provide data as a function oftime at discrete locations

table• MDM ‒ materials

degradation matrix

TIM

E

NDE provides data as adegradation matrix

• MIT and MDM being expanded to include

data as a function of location at discrete times

concrete (EPRI task)• NDE ‒ SHM requirement

differences being studied

SPACEFundamental differences in data structure between Nondestructive Evaluation differences being studied

• Measurements and monitoring gap

(NDE) and Structural Health Monitoring (SHM))(After Thompson [2009])


g g panalysis/needs assessment under development

(After Thompson [2009])

System, Structure, and Component (SSC) Component Performance(SSC) Component Performance Monitoring System*

On-Line Monitoring (OLM)

Diagnostics

Prognostics• What is the

Remaining

Risk Mitigation• How can the

effects of

Monitoring and Detection

Diagnostics• What is the

fault or degradation?

Remaining Useful Life (RUL) ?

degradation be mitigated?

DataDetection• Is there an

anomaly or fault?

Diagnostics and Prognostics (D/P)*Baldwin et al., 2010


,

Potential SSCs Issues with High Plant ImpactsImpactsWhich are the potential critical Systems, Structures and Components

that can significantly impact the cost, schedule and ultimate viability f th LTO? Si ifi I ?of the LTO? Significant Impact?


Potential Critical SSCs Issues with High Plant ImpactsHigh Plant Impacts (cont’d) Significant Impact?

*Of Burns and Roe


Proactive Management of Degradation:gPassive Components -- Motivation

Issue Programs

Corrosion Research

• In-service inspection: traditional nondestructive evaluation (NDE)

Crac

k Le

ngth

I

Development ofII

D l

Development and linkage of small cracks

III

Cost

Crack Length

IV

Growth of large cracks

• Periodically during outages• Long-initiating, fast-growing damage

(such as stress corrosion cracking SCC) b bl

Units of Time (or Fraction of Life)

Development of crack nucleation

sites

Development of crack

precursors Detection Limit

Units of Time (or Fraction of Life)

Cor SCC) can be a problem• Proactive Management of Materials

Degradation (PMMD)• Become “proactive” ‒ prediction of

remaining line• Early detection of materials degradation


Degradation Mechanism ClassificationClassification

• Aging degradation mechanisms are usually classified into:

• Internal: • changes to microstructure or chemical composition• change intrinsic properties (thermal aging creep• change intrinsic properties (thermal aging, creep, irradiation damage, etc.).

• Imposed: physical damage on the component• physical damage on the component

• metal loss (corrosion, wear) or cracking or deformation (stress-corrosion, deformation, cracking).

Phenomenon of aging degradation in NPPs are• Phenomenon of aging degradation in NPPs are complex:

• requires sophisticated, state of science and technology

IAEA Proceedings Series (2005)

procedures to effectively manage it and ensure safe, reliable operation

• not only technology is involved,


g ( )y gy ,• an effective management system is needed in order to

correctly implement mitigation or monitoring actions.

Precursors• NDE for materials degradation

precursorsprecursors• Nature of precursors depend on material

type and degradation mechanism• Mechanisms of interest in passive metallic components include fatigue (thermal and mechanical) SCC and(thermal and mechanical), SCC and embrittlement

• Local variations in residual stress, grain morphology and material chemistry

L l i ti i l ti ti• Local variations in elastic properties, electrical conductivity and magnetic permeability

fatigue pre-crack

SCC region


Evolution of Stress Corrosion C ackingCracking

NDT detection limit


Example of Effects of Longer Term Ope ationOperation


Which are the systems consider to be potentially life limiting?be potentially life limiting?

• Reactor Pressure Vessel (RPV)• Primary piping• Core internalsCore internals• Buried piping• Concrete structures• Concrete structures

• Primary containmentN l i l d• Nuclear island


Aging Management Plan (AMP) Guidance - Metallic Primary Components y pand Concrete Containments

Metallic Components Concrete Containmentsp• ASME Code Section XI• Guidance from various

Industry groups

• Article IWL-2000 of ASME code Section XI

Concrete components (category L-A)y g p• NEI, EPRI, BWRVIPs,

GESILs, WCAPs

Concrete components (category L A) Un-bonded post-tensioning systems

(category L-B)• Article IWE-2000 of ASME codeArticle IWE 2000 of ASME code

Section XI Metallic liner plates

• Additional GuidanceSource: Shah VN and CJ

Hookham. 1998. "Long-term Aging of Light Water Reactor

Concrete Containments "

• Additional Guidance from AmericanConcrete Institute

http://www.ne.doe.gov/LWRSP/overvie

Concrete Containments. Nuclear Engineeing and Design

185:51-81.


p // g / /w.html

AMP Guidance - CablesIAEA. 2000. Assessment and Management of Ageing of Major Nuclear Power Plant Components Important to Safety: In-containment Instrumentation and Control Cables. IAEA-TECDOC 1188 International Atomic Energy Agency Vienna AustriaTECDOC-1188, International Atomic Energy Agency, Vienna, Austria

EPRI. 2010a. Plant Support Engineering: Aging Management Program Development guidance for AC and DC Low-Voltage Power Cable Systems for Nuclear Power Plants. EPRI y1020804, Electric Power Research Institute, Charlotte, North Carolina.

EPRI. 2010b. Plant Support Engineering: Aging Management Program Guidance for Medium-Voltage Cable Systems for Nuclear Power Plants EPRI 1020805 Electric Power ResearchVoltage Cable Systems for Nuclear Power Plants. EPRI 1020805, Electric Power Research Institute, Charlotte, North Carolina.

• An EPRI guide for the management of I&C cables ismanagement of I&C cables is under development (at time of review)Th NRC i i i i

Source: Fantoni P. 2010. “Cable Aging Assessment and Condition Monitoring in

• The NRC is in negotiations with industry to develop a mutually agreeable AMP for

Nuclear Power Plants.” Presented at June 10, 2010, Seattle, WA

Center for Nondestructive Evaluationcables

Degradation ‒ Concrete and CablesCablesCommon Degradation Mechanisms (Concrete(ConcreteAlkali Silica ReactionsSulfate AttackCorrosion of Embedded SteelCorrosion of Steel Liner Plates “Hot Spots”

Cable failure due to localizedCommon Degradation Mechanisms (IAEA-TECDOC-1188 vol. 1)Macromolecular scission

Cable failure due to localized degradation of a section of cable due to exposure to extreme stressors (i eMacromolecular scission

Cross-linking reactionsOxidation

extreme stressors (i.e. temperature, radiation)

Elimination of hydrochloric acidEvaporation of plasticizers


Degradation ‒ Metallic Primary ComponentsComponents

Common Degradation Mechanisms

Unacceptable Degradation Unacceptable Degradation Unacceptable Degradation

Stabilizes at an unacceptable level

g

Deg

rada

tion

Deg

rada

tion

Deg

rada

tion

Stabilizes at an acceptable level

Stabilizes at an unacceptable level

Initiation Time Crack Propagation

Leve

l of

Initiation Time

Crack PropagationLe

vel o

f

Leve

l of

Early Trend Line

Early RapidLoss of FR

Slower Loss of FRWith Possible Stabilization

Time Time Time

Loss of FR With Possible Stabilization

Fatigue Cracking Stress Corrosion Reduction in g gCracking Fracture

Toughness


NDE ‒ Metallic Primary Pressure Boundary ComponentsBoundary ComponentsCommon NDE technologiesVisual Testing (VT)Ultrasonic Testing (UT)A ti E i i (AET)Acoustic Emission (AET)Guided Wave Ultrasonic Testing (GUT)Eddy Current (ET)Liquid Penetrant Testing

Visual TestingSource: M.T. Anderson, S.E. Cumblidge, and S.R. Doctor, “An Assessment of Remote Visual Testing System Capability for the Detection of Service I d d C ki ” B k t B i Th A iMagnetic Particle Testing

Radiographic Testing (RT)

Induced Cracking,” Back to Basics, The American Society for Nondestructive Testing, Columbus, Ohio, September 2005.

Magnetic Particle TestingSource: Basic Principles, Iowa State University, Ames, Iowa (http://www.ndt-ed.org/EducationResources/CommunityCollege/MagParticle/Indications/DryExamples htm)


e/MagParticle/Indications/DryExamples.htm).

NDE ‒ Concrete Containments and CablesCablesCommon NDE Technologies (Concrete)Visual (VT)

Indenter ModulusSource: Fantoni P. 2010. “Cable Aging Assessment and Visual (VT)

Ultrasonic Testing (UT)IR Thermography

Condition Monitoring in Nuclear Power Plants.” Presented at June 10, 2010, Seattle, WAg p y

Radiographic Testing (RT)Half Cell Potential Common Cable NDE Technologies

Elongation At Break (EAB)Linear Polarization Resistance Elongation At Break (EAB)Indenter Modulus Oxidation Induction Time/Temperature p(OIT/OITP)Mass LossTime Domain Reflectivity (TDR) and

Half Cell PotentialSource:http://www.cflhd.gov/agm/engapplications/BridgeSystemSubstructure/231DirectMeasurementMethods htm

Time Domain Reflectivity (TDR) and variantsLine Resonance Analysis (LIRA)


stemSubstructure/231DirectMeasurementMethods.htm

Listening for trouble!g


Some Degradation Monitoring Techniq esTechniques

• Ultrasonic Methods• Ultrasonic phased arrayUltrasonic phased array,

backscattering• Guided wave ultrasonics• Acoustic microscopy• Acoustic emission

Diffuse fieldMulti-frequency Eddy Currents• Diffuse field

• Non-linear acoustics…Electromagnetic Methods

Eddy Currents

Acoustic • Electromagnetic Methods

• Multi-frequency Eddy currents

Microscopy

• Magnetic Barkhausenemission Barkhausen Emission


• …

Ultrasonic Methods• Elastic wave propagation in materials is impacted by thematerials is impacted by the presence of damage

Microstructure• Microstructure• Dislocations• Residual stress• Cracks


Acoustic Emission Testingg• AE the only technique currently

sanctioned for online monitoring ofsanctioned for online monitoring of materials degradation in NPPs by the ASME code

• Section XI and Section V, Article 13,allow use of AE to monitor growth of existing flaw characterized by otherexisting flaw characterized by other NDE technique

• AE data examined every two monthsy• Not widely accepted by the US

nuclear industry• Worries about false calls and mid-cycle

shutdowns: No regulatory relief for the use of AE


Acoustic Emission Testingg• USAEC and USNRC sponsored

work to understand thework to understand the feasibility AE monitoring from mid 1960’s to early 1990’sy

• Work resulted in a series of reports and eventual field demonstrations at Watt’s Bar 1 reactor and Limerick Unit 1 reactorreactor


Acoustic Emission Testingg• Important Results

C k i l b d t t d i th f fl i• Crack signals can be detected in the presence of flow noise during normal NPP operation

• AE system sensor hardware can survive NPP environmentsy• AE successfully deployed to monitor crack growth in RPV

nozzle weldment continuously between successive refueling outages at Limerick Unit 1outages at Limerick Unit 1

• Russians using AE in life extension activities• Feasibility of online crack monitoring in NPPsFeasibility of online crack monitoring in NPPs with AE has been demonstrated

• AE studies provide significant insights that canAE studies provide significant insights that can guide other passive structure on-line monitoring


Acoustic Emission Testingg• Fatigue crack testing

C b t l i• Carbon steel pipe• 304 stainless steel pipe• 6 inch pipes

• In both materials, signals , gassociated with crack growth process were detectedProc. of SPIE Vol. 7984 798424‐1 (2011)


Acoustic Emission Testing -Eq ipmentEquipment

System used in Present day systemSystem used in Limerick Unit 1 demonstration

Present day system


In-situ Monitoringg• Sensors must be capable of in-situ

continuous monitoring in extreme environments

• Sensitivity to changes at microscopic levelSensitivity to degradation precursors

G id d W Ult i

• Sensitivity to degradation precursors• Long term stability of measurement system• Non-disruptive, in-situ system calibration

Guided Wave Ultrasonicsp , y

• Non-disruptive data transfer

Acoustic Emission


Guided Ultrasonic Waves• Long rage inspection capability (10’s of

meters) make technique attractive ) q• Applications to steam generator/IHX tubing,

buried piping, fuel rod cladding, etc.Challenges• Challenges

• Fluid filled piping• Unusual geometries• Characterizing flaw significance without prior knowledge


Guided Ultrasonic Waves• Monitored fatigue crack in 304 stainless

steel pipep p• Circumferential crack growth up to 3”• Through transmission measurements• Frequency swept from 350 kHz ‒ 600• Frequency swept from 350 kHz 600

kHz• Automation of system


Diffuse Field • Diffuse field develops after the ultrasonic field has undergone

many scattering events with the material and boundaries y gand a portion of the scattered wave is eventually returned to the transducer (Egle 1981).

Becker et al (2003) Weaver & Sachse (1995) showed that• Becker et al. (2003), Weaver & Sachse (1995) showed that experimentally measured ultrasonic waves in cement can be interpreted using diffusion theory to quantitatively measure di i ti d diff i ffi i t f ti f fdissipation and diffusion coefficients as functions of frequency and microstructure.

• These results provide a basic understanding of the effect of p gsome features of the microstructure on the propagation of ultrasonic waves.

• Diffuse field and backscattering measurements are appealing• Diffuse field and backscattering measurements are appealing because of the relative simplicity of the measurement and the theoretical description of the scattering processes.


Diffuse Field UltrasonicsBecker et al. (2003),

0 0 0

0 . 0 1

0 . 0 2

ude

(Vol

t)1 5 w t %

0 0 0

0 . 0 1

0 . 0 2

ude

(Vol

t)1 5 w t %

Weaver & Sachse (1995) showed that experimentally measured ultrasonic waves

- 0 . 0 2

- 0 . 0 1

0 . 0 0

0 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0T i m e ( s )

Am

plitu

- 0 . 0 2

- 0 . 0 1

0 . 0 0

0 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0T i m e ( s )

Am

plitu measured ultrasonic waves

in cement can be interpreted using

T i m e ( s )T i m e ( s ) diffusion theory

F F T

Am

p

Am

p

Am

p

F r e q u e n c y

F F T

Am

p

Am

p

Am

p

F r e q u e n c y

0 . 0 4

0 . 0 5

0 . 0 6

e (A

.U.) 1 . 2 5 M H z

• E n e r g y =0 . 0 4

0 . 0 5

0 . 0 6

e (A

.U.) 1 . 2 5 M H z

• E n e r g y = 3 mm Glass Beads and Water

0 . 0 0

0 . 0 1

0 . 0 2

0 . 0 3

0 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0T i m e ( s )

Am

plitu

de

1 5 w t % = 0 . 0 3 7 s - 1

E n e r g y • Q - 1 = / ( 2• f = f r e q u e

0 . 0 0

0 . 0 1

0 . 0 2

0 . 0 3

0 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0T i m e ( s )

Am

plitu

de

1 5 w t % = 0 . 0 3 7 s - 1

E n e r g y • Q - 1 = / ( 2• f = f r e q u e

Panetta et al. 2005

3 mm Glass Beads and Waterinside the Styrofoam Test Cell


Diffuse Field Ultrasonics

0 .0

0 .5

de (v

olts

)

F S tiData from Weaver & Sachse (1995)

Diff i it ( 2̂/ ) Di i ti (1/ )PNNL experiment

-0 .50 1000 2000

T im e (us)

Am

plitu

d

Diffusivity 95% Lower Bound 95% Upper Bound Dissipation 95% Lower Bound 95% Upper Bound250 90 0.544 0.499 0.589 5.266 5.061 5.471 1.48+/‐0.1 3.26+/‐0.74500 70 0.718 0.703 0.733 7.478 7.365 7.592 1.02+/‐0.05 5.8+/‐0.4

Frequency (kHz)

Separation (mm)

Diffusivity (mm̂ 2/us) Dissipation (1/ms)Diffusivity (mm̂ 2/us) Dissipation (1/ms)

Diffuse Energy Spectral Density

500 70 0.718 0.703 0.733 7.478 7.365 7.592 1.02 / 0.05 5.8 / 0.4500 90 0.895 0.862 0.928 6.835 6.572 7.099 0.88+/‐.027 7.0+/‐0.5750 90 1.245 1.145 1.346 15.057 14.076 16.038 1.41+/‐0.03 13.1+/‐0.271000 80 1.452 1.373 1.531 14.751 14.443 15.059 1.53+/‐0.05 15.3+/‐0.9y

Least SquaresLeast Squares Curve Fitting

Extract ParametersParameters

(Diffusivity, Dissipation, Arrival

Time)


Time)

Diffuse Fields ‒ Cast Steel CharacterizationCharacterization

• Pitch-catch configurationPitch catch configuration• 6-cycle, 500 mV tone-burst excitation

• 1.9 MHz, 2.0 MHz, 2.1 MHz, 2.2 MHz, 2.5 MHz• Transmit: 2.25 MHz 0.25” diameter probe• Receive: Microprobe (bandwidth approximately 2.5 MHz)

P b i di t t t ith i ith thi l f l t• Probes in direct contact with specimen with thin layer of couplantin between

• Data recorded corresponds to ~9.75 ms * P Ramuhalli et al


p(2010)

Diffuse Fields• Diffuse field energy spectral density estimated by filtering the RF signal squaredfiltering the RF signal squared• Low-pass filter, with cutoff frequency of 12 kHzLeast squares curve fit to estimate• Least-squares curve-fit to estimate• Diffusivity, Dissipation, and Arrival time

22

0 0

1 1, , 1 4 cos cos cos cos

n mD tl p

n m

n x m y n x m yE x y t el p l p

2

2

0

12 cos cos

nD tl

n

m

p p

n x n x el l

0

12 cos cos

mD tp

m

m y m y e Ep p

0te


Curve Fit Results

Curve Fit Curve Fit (log-scale)Curve Fit (2.2 MHz)

Curve Fit (log scale) (2.2 MHz)


Prognostics

Recurrent Neural

Bayesian Methods

Recurrent Neural Networks

Probabilistic Fracture Mechanics

y

• Prognostics Algorithms • Bayesian algorithms

• Model-based probabilistic l h bl f dalgorithms, capable of providing

confidence levels• Recurrent Neural Networks (RNN)

• Generally deterministic ‒ difficult toGenerally deterministic difficult to extract confidence levels

• Probabilistic fracture mechanics• Typically focus on large-crack growth


PHM for Passive NPP Components Predict Time-to-p ed ct e to

Failure (TTF) and Estimate RUL, Confidence

Wait for New Measurement

Bounds

h i b dNDE

Measurement zjat time j

Physics-based Models

Estimate at time jPrognostics:

Predict Material State for k>j

Degradation “Level”

(Material State for k>jState)

Stressor j at time j Stressor Estimates for k>j


j f j

Early Fatigue PrognosticMeasurements Physical

Models• Remaining useful life (RUL)

estimation for passive componentsestimation for passive components‒ From precursor measurement to

RULP b bili i i l i h• Probabilistic prognostic algorithm “Early fatigue prognostic”‒ Shows potential for RUL estimation

e Den

sity

in passive components• Open issues

‒ Better models of damage

Failu

reBetter models of damage accumulation

‒ Higher sensitivity measurementsBetter understanding of

Accumulated operating time (fraction of life)

‒ Better understanding of uncertainties associated with measurements and modelsE t i f l ith t th


‒ Extension of algorithms to other degradation mechanisms

Sample Estimates of the System State Prior to WeightingState Prior to Weighting

30

25

30

Measurement A l S

15

20

m S

tate

at time step 20Actual System State (unknown)

10

15

Sys

tem

0 2 4 6 8 10 12 14 16 18 200

5 Monte Carlo Estimates

0 2 4 6 8 10 12 14 16 18 20Time Step


Assessment of State of Maturity for Diagnostic [D] and Prognostic [P] Technologies (adapted from (Howard 2005) – Bond et al (2012))g ( p ( ) ( ))

Diagnostic/Prognostic Technology for: AP(a) A(b) I(c) NO(d)

Basic Machinery (motors pumps generators etc ) D&PBasic Machinery (motors, pumps, generators, etc.) D&P

Complex Machinery (helicopter gearboxes, etc.) D&P

Metal Structures D P

Composite Structures D Pp

Electronic Power Supplies (low power) D P

Avionics and Controls Electronics D P

Medium Power Electronics (radar, etc.) D P

i h l i ( l i l i )High Power Electronics (electric propulsion, etc.) D P

Instrument Re-calibration ‒ monitoring (NPP) D P

Active Components ‒ nuclear power plants D P

Passive Components ‒ nuclear power plants D P

(a) AP = Technology currently available and proven effective.

(b) A = Technology currently available, but V&V not completed.

(c) I = Technology in process but not completely ready for V&V(c) I = Technology in process, but not completely ready for V&V.

(d) NO = No significant technology development in place.


Passive Structure ‒ Online Monito ingMonitoringLarger defects

• Acoustic emissionEarly degradation• Acoustic,Acoustic emission Acoustic,

electromagnetic, thermal?

• Guided waves• Guided waves

Ph d SAFT• Phased array - SAFT• Diffuse field (concrete?)


Advanced Diagnostic Technologiesg g• Smart components and structures

• Self-diagnostic systems• Embedded Micro-Electromechanical SystemsElectromechanical Systems (MEMS) (and other) health monitoring sensors What everyone wants “Tricorde

• Wireless communication• Distributed data processing and control networksand control networks

• Prognostics implementation• Advanced NDE technologiesd a d o og• Proactive operations and maintenance program Bond et al (NERI Project)


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Challengesg• Lack of accessD d ti h i ith l i b ti• Degradation mechanisms with long incubation phases, short time - fast growth phrases (SCC)iffi l i l (f h i f• Difficult materials (from the perspective of

conventional inspections)• Sources of noise in data (measurement noise and uncertainties

• The unknowns as plans move from 40 to 60 and potentially 80 years of operation


Conclusions• Active components can now be diagnosed and managed using

advanced condition based maintenance ‒ prognostics capability p g p yexists, but has yet to be applied in US nuclear power plants

• Passive components are seen as the key to LTO (60-80 years) for the US nuclear fleetthe US nuclear fleet

• The potential to apply advanced on-line monitoring is being investigated: attention is focused on (i) acoustic emission, (ii) guided waves and (iii) diffuse

• Proactive approaches implemented using on-line monitoring have the ability to both constrain operations and maintenance coststhe ability to both constrain operations and maintenance costs and provide plant operators with greater plant condition awareness. I d diti ill t b tt i• Increased condition awareness will support better economic assessments of life costs and help to ensure continued safe operation as plants operate longer.


p p p g

Acknowledgmentg• Parts of this work was supported in part by the DOE ‒

NE LWRS Program: I acknowledge contributions by theNE LWRS Program: I acknowledge contributions by the PNNL Prognostic team: Ryan Meyer, Pradeep Rahamuhalli, Jamie Coble (PNNL) Samy Twafik and , ( ) yNancy Lybeck (INL)

• This work was in part supported in part by the U.S. Nuclear Regulatory Commission (NRC), Office of Nuclear Regulatory Research under contracts N-6019, N 6029 and N 6957N-6029 and N-6957.

• Support for work in this area has been provided through the Reactor Aging Management (RAM) Focusthrough the Reactor Aging Management (RAM) Focus Area of the PNNL Sustainable Nuclear Power Initiative (SNPI)


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On Center for Nondestructive Evaluation...

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