© 2015 Electric Power Research Institute, Inc. All rights reserved.

Carola Gregorich, Dr. - Senior Technical Leader Daniel Wells, PhD – Program Manager, Chemistry

17th International Conference on Environmental Degradation of Materials in Nuclear Power Systems –

Water Reactors Ottawa, ON, Canada, August 10, 2015

In-Plant Gamma Spectrometry for Source Term Control

Monitoring Review of US Experience

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In-Plant Gamma Spectrometry

Captures qualitatively and quantitatively isotopic data Can be done at a point in time and/or in time sequence

Adaptable to purpose and environment of measurement

Provides diagnostic and forensic data for asset protection and radiation field reduction

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Why Asset Protection Affects Radiation Field Generation

Soluble Species

Particulates Insoluble

Desorption

Sorption

Dissolution

Precipitation

Example Activation [Decay] 59Co (n,γ) 60Co [5.27 yrs]

58Ni (n,p) 58Co [70 days]

Rad

iatio

n Fi

eld

Stellite Replacement Low-Co Alloys

SD/SU Protocol Coolant Cleanup

Cor

e/Fu

el D

esig

n Fu

el C

lean

ing

Chemistry Regimes: Zn, pH, H2, Pt

Chemical/Physical Decon Surface Passivation

AL

AR

A

Comprehensive mechanistic understanding of corrosion, corrosion product release, and activity incorporation

on ex-core surfaces remains elusive under

multiple change implementation conditions

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Elusive Details of Surface Activity Incorporation

Base Metal (virgin material)

Metal Oxide Surface Protective Film

Permanent Corrosion Product Oxide Layer

Transient Corrosion Product Particulate Layer

Bulk Coolant

Release and incorporation mechanisms are controlled by base metal, coolant chemistry, temperature, pressure, and flow – Nickel and iron typically go into solution, while chromium does not – Interfacial coolant establishes saturation equilibrium with bulk coolant in

boundary layer – Temperature affects solubility – Ferrites & other species

form when precipitation occurs Particulate suspension

changes with flow Incorporation of activated

species depends on its chemical and physical properties as much as on those of the surface

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Standard Radiation Monitoring Programs

PWR: AUXS Locations – added in 2014 Revision CVCS-LD – CVCS letdown line in aux building CVCS-RL – CVCS return line in aux building CVCS-HX – Non-regenerative CVCS heat exchanger

RHR-LD – RHR letdown line in aux building RHR-RL – RHR return line in aux building RHR-HX – RHR heat exchanger

PZR1 – Horizontal section of Pressurizer Surge Line (hot leg tap) PZR2 – Horizontal section of Pressurizer Spray Line (cold leg tap) PZR3 – Horizontal section of Pressurizer Spray Line (head)

RFB – Refueling bridge, near operator RVCH – Reactor vessel closure head

B RECIRC PUMP A RECIRC PUMP

'A' RISER30o

'B' RISER60 o

'C' RISER90 o

'D' RISER120o

'E' RISER150o

'F' RISER210o

'G' RISER240 o

'H' RISER270o

'J' RISER300 o

'K' RISER330 o

'B' SUCTION0

o

'A' SUCTION

180 o

FCV 68-35FCV

68-33

FCV 68-1

FCV 68-3

FCV 68-79

FCV 68-77

HCV 74-69

FCV 74-49

HCV 74-55

584' grating

563' grating

550' floor

C/L 556' - 8"

C/L 552' - 4"

C/L 580' - 9"

22' Discharge Header

593' - 4"591'11" WHIPRESTRAINT

591'11" WHIPRESTRAINT

N1B

N2E N2D N2C N2B N2A N2K N2J N2H N2G N2F

1AD

5A

4A

3A

2A1A

2AS

N1A

1BD

5B

4B

3B

2B

1B

2BS

XX OR XXX DENOTES SURVEY POINT, POINTS SHOULD BE MARKED ON MIRROR INSULATION

B RECIRC PUMP A RECIRC PUMP

'A' RISER30o

'B' RISER60 o

'C' RISER90 o

'D' RISER120o

'E' RISER150o

'F' RISER210o

'G' RISER240 o

'H' RISER270o

'J' RISER300 o

'K' RISER330 o

'B' SUCTION0

o

'A' SUCTION

180 o

FCV 68-35FCV

68-33

FCV 68-1

FCV 68-3

FCV 68-79

FCV 68-77

HCV 74-69

FCV 74-49

HCV 74-55

584' grating

563' grating

550' floor

C/L 556' - 8"

C/L 552' - 4"

C/L 580' - 9"

22' Discharge Header

593' - 4"591'11" WHIPRESTRAINT

591'11" WHIPRESTRAINT

N1B

N2E N2D N2C N2B N2A N2K N2J N2H N2G N2F

1AD

5A

4A

3A

2A1A

2AS

N1A

1BD

5B

4B

3B

2B

1B

2BS

XX OR XXX DENOTES SURVEY POINT, POINTS SHOULD BE MARKED ON MIRROR INSULATION

BWR: AUXS Locations – reinstated/optimized in 2014 Revision

2014 Revisions capture also the locations of concern to radiation protection

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Available Data Sets from U.S. Fleet

BWR PWR

More & systematic data are available for BWR fleet

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What Can Be Concluded from Available PWR Data?

Limited data set, often captured to assess specific change, i.e., not comprehensive, and general conclusion may have limited applicability: Cobalt activities are higher in regions of lower temperature. Cobalt-58 activities are generally higher than Co-60 activities. Hot leg Co-58 and Co-60 activities remain constant over life of plant. Crossover/cold leg Co-58 and Co-60 activities decrease over life of plant.

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What Do the Data of BWR Reactor Recirculation System Tell?

Maximum in Bin

Measurement Data In Bin

Co-60 Median

Co-60 Average

Co-60 Standard Deviation

10 140 4.88 4.90 2.24

20 29 13.78 13.85 2.57

30 5 24.87 24.39 1.61

40 3 34.60 33.81 1.50

50 1 45.95 45.95

Plant design and operation resulting in Co-60 Surface Activities < 2.7 µCi/cm2 – identify desired conditions > 7.2 µCi/cm2 – identify detrimental conditions to achieve lower radiation fields

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Today’s U.S. BWR Coolant Operating Regimes Not Well Characterized

Num

ber o

f Gam

ma

Scan

Cam

paig

ns in

U.S

. BW

Rs Implementation of zinc injection

and hydrogen water chemistry was proportionally followed

Implementation of original noble metal injection followed on demonstration principle

? Implementation on online injection of platinum follow at discretion

Data are needed to • understand today’s corrosion

and activity incorporation • ensure asset protection, and • lower radiation fields

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Exploring Data – Seeing Faster, Clearer & More

Uncovering relationships not readily found by traditional methods/expertise Faster deeper dive into data exploration

Traditional Data Exploration: Scatter = No Conclusion = No Opportunity

Data Exploration with Tools of Data Science: Clear Grouping = Conclusions lead to Opportunities

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Diagnostic Tools of Data Science – Decision Tree Example

Confirming/disputing current assumptions and hypothesis

Identifying factors currently not considered

Original Condensate Filter Demineralizer Design

Main Condenser Tubesheet Material

Operational Year Zinc Injection Start

Operational Year Gamma Scan

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Diagnostic Tools of Data Science – Cluster Analysis Example

Puzzling – two very distinct clusters Insights do not reflect current understanding of chemistry regime effect on Co-60 incorporation

Limitation of Dataset?

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Diagnostic on BWR Gamma Scan Data to Derive Insights on Radiation Field Control

Parameter Set (Inputs) CRT Decision Tree

CHAID Decision Tree Two-Step Cluster

Basic Plant (7) 1. Original condensate cleanup design

2. BWR class

1. Original condensate cleanup design

2. Presence of fuel failure

1. BWR class 2. Number of control rod

blades Number of clusters - 5

Plant Materials (10) 1. Main Condenser Tubesheet

2. RCS StelliteTM surface area

1. Reactor recirculating System Piping

2. RCS StelliteTM surface area

1. Moisture Separator 2. Reactor recirculating

System Piping Number of clusters - 4

Chemistry (5) 1. Operational OLNC year 2. Operational NMCA Year

1. Operational HWC year 2. Operational DZO Year

1. Operational DZO year 2. Operational NMCA Year Number of clusters - 2

Operational (13) 1. Feedwater to condensate flow ratio

2. Core power, kWt/L

1. RCS liquid mass at full power, lbs

2. Average condensate temperature

1. Average condensate temperature

2. Core flow Number of clusters - 4

Top Two Importance Predictors

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Diagnostic on BWR Gamma Scan Data to Derive Insights on Radiation Field Control

Top Step – Cluster Analysis Top-5 dominant clusters shown

Kohonen – Cluster Analysis

Attention:

Colors Do Not relate.

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Validating Feasibility of Data Science Exploration Approach Co-60RRS-BRAC = 1.91 YOLNC - 0.62 YHWC + 11.15 RFW/Cd – 0.10 TAvCd – 6.5E-5 MRCSLq + 0.20 AStellRCS + 1.12 AStellCRB

+ 2.30 TCoreIn + 0.88 PCore + 2.75E-2 YOPS – 764.9 R2 = 0.633

Parameter Symbol Plant A Plant B Plant C Cycle N Plant C Cycle N+5

Operating year OLNC implemented YOLNC 27.5 30.8 26.1 26.1

Operating year HWC implemented YHWC 15.795 8 3.1 3.1

FW-to-Condensate flow ratio RFW/Cd 1.433 0.943 1 1

Avg. Condensate temperature, F TAvCd 115 115 110 110

RCS liquid mass at full power, lbs MRCSLq 594300 440000 471000 471000

StelliteTM surface area in RCS, sqft AStellRCS 162.639 118.3 118.3 118.3

StelliteTM surface area in of CRB, sqft AStellCRB 49.751 38.5 38.5 38.5

Coolant core-In temperature, C TCoreIn 274 276 278 278

Core power, kWt/L PCore 48.7 49.2 50.1 50.1

Operational year at time of Gamma Scan YOPS 29 23 35 45

Co-60 surface activity, measured, µCi/cm2 7.3 6.2 5.15 To be measured

Co-60 surface activity, calculated, µCi/cm2 5.8 4.9 3.8 4.1

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Validating Feasibility of Data Science Exploration Approach Co-60RRS-BRAC = 1.91 YOLNC - 0.62 YHWC + 11.15 RFW/Cd – 0.10 TAvCd – 6.5E-5 MRCSLq + 0.20 AStellRCS + 1.12 AStellCRB

+ 2.30 TCoreIn + 0.88 PCore + 2.75E-2 YOPS – 764.9 R2 = 0.633

Regression analysis based on parameter identified in exploratory decision tree and cluster analysis yields a potentially feasible approach to predict Co-60 incorporation in to ex-core surfaces on plant specific basis

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Isotopic Data for Asset Protection and Radiation Field Control Gamma Spectrometry

– Captures qualitatively and quantitatively isotopic data – Can be done at a point in time and/or in time sequence – Adaptable to purpose and environment of measurement – nuclide identification capabilities make it a diagnostic and forensic tool

Evaluation of gamma spectrometry data linked to plant design, materials, and operational information through data science tools to – Uncover previously hidden relationships – Identify new opportunities for asset protection and radiation field control – Enable improvements in performance indicators, utilization, and cost efficiency

U.S. gamma scan data set is limited

Available U.S. data for ex-core surface activities do not reflect adequately current plant operation regime

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Together…Shaping the Future of Electricity