chemistry monitoring and control for fuel reliability monitoring and control for fuel ... chemistry...

Chemistry Monitoring and Control for FuelReliability

Technical Report

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Effective December 6, 2006, this report has been made publicly available in accordance with Section 734.3(b)(3) and published in accordance with Section 734.7 of the U.S. Export Administration Regulations. As a result of this publication, this report is subject to only copyright protection and does not require any license agreement from EPRI. This notice supersedes the export control restrictions and any proprietary licensed material notices embedded in the document prior to publication.

EPRI Project Manager B. Cheng

EPRI 3412 Hillview Avenue, Palo Alto, California 94304 PO Box 10412, Palo Alto, California 94303 USA 800.313.3774 650.855.2121 [email protected] www.epri.com

Chemistry Monitoring and Control for Fuel Reliability 1009731

Interim Report, December 2004

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iii

CITATIONS

This report was prepared by

Finetech, Inc. 115 Route 46, Suite A-1 Mountain Lakes, NJ 07046

Principal Investigators J. Giannelli M. Jarvis J. Tangen A. Jarvis

This report describes research sponsored by EPRI.

The report is a corporate document that should be cited in the literature in the following manner:

Chemistry Monitoring and Control for Fuel Reliability, EPRI, Palo Alto, CA, 2004. 1009731.

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PRODUCT DESCRIPTION

Water chemistry has been identified as a known or potential contributing cause in recent corrosion-induced fuel failures and anomalies such as fuel crud spallation and enhanced nodular corrosion. The 2004 revision of the BWR Water Chemistry Guidelines (EPRI report 1008192) addressed these concerns by recommending tighter chemistry control limits and additional monitoring for contaminants and additives that can have an adverse effect on fuel cladding corrosion. The revision focused on chemistry control for minimization of IGSCC (intergranular stress corrosion cracking) and IASCC (irradiation-assisted stress corrosion cracking) of reactor vessel internals and primary system piping and components, fuel reliability, radiation dose control, and FAC (flow accelerated corrosion) control. This interim report, which does not modify or supersede the Guidelines, provides a tutorial on these recommended BWR chemistry monitoring and control approaches and supplies supporting information on plant design characteristics, chemistry regimes, operating practices, and sources of impurities. It also reviews industry operating experience and provides plant chemistry data and calculated metals deposition results for several plants.

Results & Findings This report documents plant design features and operating practices that have an influence on or are impacted by plant chemistry. It also addresses current BWR water chemistry monitoring practices and potential sources of impurities, with an emphasis on those areas potentially related to fuel reliability. The report discusses chemistry transients and provides the results of chemistry analyses and mass balances performed specifically for fuel reliability monitoring. The source of data is the EPRI BWR Chemistry Monitoring Database, including the results of various ancillary surveys performed to support the database effort. The database currently encompasses 39 operating BWR units, including the 34 U.S. units, 2 Mexican BWRs and 3 European BWRs.

Challenges & Objectives Since the late 1990s, a number of cladding corrosion-induced fuel failures have occurred and enhanced nodular corrosion indications have been observed at BWRs despite advances in fuel cladding corrosion resistance and improved water quality. While the causes of the recent corrosion failures have not been identified, the operating and chemistry changes that have occurred during this period may have played a role. These include increased fuel duty, the use of Noble Metal Chemical Application (NMCA) in combination with hydrogen injection, and increased use of zinc injection. Concern about the economic and operational impact of fuel corrosion issues and the possibility of a chemistry influence on water chemistry practices has led to efforts to detect and quantify previously unnoticed chemical intrusions, to estimate corrosion products deposition on the fuel during steady state and non-steady state conditions, and to evaluate the possible role of chemical species such as silica previously thought to have no significant potential detrimental impact on fuel.

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Applications, Values & Use Given the wide range of current issues and unknowns, communication between fuels and chemistry personnel is especially important. It is of particular value for fuels personnel to have an understanding of the level of vigilance of todays BWR chemistry monitoring and control programs. In addition, it is important to more widely disseminate chemistry results, which may hold insights into identifying or eliminating a potential impact on fuel reliability.

EPRI Perspective Nuclear power plant chemistry is integral to major component reliability, radiation field management, fuel integrity, and the overall economic viability of plant operation. In the early days of nuclear power plant operation, poor control of water chemistry was a cause of materials degradation. Starting about 20 years ago, EPRIs efforts have contributed to a continuing improvement in water quality, including control of impurities to extremely low levels, reduction in the frequency of transient fault conditions, and the introduction of additives to control corrosion. However, changes in how plants are operated have subjected fuel to new conditions. Over the last decade, fuel duty has been steadily increasing through plant uprating, smaller reload batch size, and burnup and cycle length extensions. Interaction of higher duty fuel with coolant impurities and additives can result in excessive deposition of crud and hideout of chemical species, potentially leading to adverse effects on fuel cladding corrosion. This document provides useful information to assist utility fuel staff in assessing various water chemistry factors which may have an effect on fuel performance.

Approach Drawing on the 2004 Revision of the BWR Water Chemistry Guidelines and the EPRI BWR Chemistry Monitoring Database, the project team produced a tutorial overview of BWR chemistry monitoring and control, gathered examples of the impact of chemical ingresses and transients, and a assembled a summary of mass balance calculations for corrosion products deposition for use by BWR fuels and chemistry personnel. Without drawing conclusions on the causes of corrosion in particular cases, the team provided information useful to assessing the impact of chemistry on fuel corrosion.

Keywords BWRs Water chemistry Hydrogen water chemistry Zinc injection Noble metal chemical application (NMCA) Water chemistry impurity trend Fuel deposit mass balance

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ABSTRACT

Recent corrosion-induced fuel failures and anomalies at BWR power plants have led to renewed interest in the possible role of water chemistry in these incidents. This report, based on the EPRI BWR Water Chemistry Guidelines 2004 revision and EPRI BWR Chemistry Monitoring Database, documents plant design features and operating practices that have an influence on or are impacted by plant chemistry. In addition, current actual BWR water chemistry monitoring practices and potential sources of impurities are addressed, with emphasis on those areas potentially related to fuel reliability. Chemistry transients are discussed and examples are given, and results of chemistry analyses and mass balances performed specifically for fuel reliability monitoring are presented.

ACKNOWLEDGMENTS

The authors would like to thank the many BWR power plant and corporate chemistry, engineering, and radiation protection staff members who support the EPRI BWR Monitoring effort by providing data and information on an on-going basis. This effort provides key support for several EPRI research and development initiatives. The data and information available were used extensively in the preparation of this report.

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CONTENTS

1 INTRODUCTION ....................................................................................................................1-1 References............................................................................................................................1-2

2 OBJECTIVES .........................................................................................................................2-1

3 BWR PLANT DESIGN CHARACTERISTICS ........................................................................3-1 General Plant Design Data....................................................................................................3-1 Power Uprate ........................................................................................................................3-1 Plant Configuration................................................................................................................3-2 Materials of Construction.......................................................................................................3-3 System Flows and Reactor Liquid Mass Inventory ...............................................................3-3 Chemistry Regime.................................................................................................................3-4

4 POTENTIAL SOURCES AND IMPACT OF BWR CHEMICAL INPUTS................................4-1 Objectionable Impurities Generation and Ingress .................................................................4-1

Corrosion Products of System Materials ..........................................................................4-1 Radiolysis Products ..........................................................................................................4-2 Main Condenser Circulating Cooling Water In-leakage....................................................4-4 Condenser Air In-leakage.................................................................................................4-5 Electro-Hydraulic Control Fluid.........................................................................................4-7 Impurities in Recycled Radwaste Liquids .........................................................................4-9 Lubricating Oils/Hydraulic Fluids ....................................................................................4-10 Impurities in Plant Makeup Water...................................................................................4-10 Ion Exchange Resin and Precoat Materials ...................................................................4-11 Closed Cooling Water and Auxiliary Boiler Chemicals ...................................................4-12 Control Blade Cracking...................................................................................................4-13 Torus/Suppression Pool .................................................................................................4-17 Fuel Pool Liquids ............................................................................................................4-17

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Condensate Storage Tank (CST) ...................................................................................4-18 Degradation of Condensate Polisher Lining Materials ...................................................4-19 Standby Liquid Control ...................................................................................................4-19 Chemical Additives .........................................................................................................4-20

DZO ...........................................................................................................................4-20 Hydrogen Injection.....................................................................................................4-21 Noble Metals ..............................................................................................................4-22 Iron addition ...............................................................................................................4-22 Condensate/Feedwater Oxygen Injection..................................................................4-24

Maintenance Chemicals .................................................................................................4-24 Consumable Chemical Materials ...............................................................................4-24 Decontamination Chemicals ......................................................................................4-25

References..........................................................................................................................4-34

5 BWR CHEMISTRY MONITORING AND CONTROL PRACTICES........................................5-1 Normal Sample Locations .....................................................................................................5-1 Monitoring for Fuel Leaks......................................................................................................5-8 Reactor Coolant Activated Corrosion Products...................................................................5-10 Actual Sampling/Analysis Frequencies ...............................................................................5-10 Reactor Water Anions Analysis...........................................................................................5-10 Reactor Water and Feedwater Metals Analysis ..................................................................5-11 Post-UV Anions Analysis.....................................................................................................5-13 Phosphate Analysis.............................................................................................................5-13 Monitoring for Chemical Inputs............................................................................................5-13 Compliance with Action Levels............................................................................................5-16 Monitoring for Unknown Ionic Impurities .............................................................................5-16 Challenges for Expanded Monitoring ..................................................................................5-17 References..........................................................................................................................5-18

6 CHEMISTRY TRANSIENTS...................................................................................................6-1 Types of Chemistry Transients..............................................................................................6-1 Examples of Chemistry Transients........................................................................................6-1

EHC Fluid .........................................................................................................................6-1 Limerick EHC Fluid Intrusion .......................................................................................6-1 Columbia EHC Fluid Intrusion......................................................................................6-5

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Condenser Leaks .............................................................................................................6-6 Resin Intrusions................................................................................................................6-7 Maintenance Chemicals ...................................................................................................6-7 Lubricants .........................................................................................................................6-8 Loss of Hydrogen Injection ...............................................................................................6-9 Startup/Shutdown Transients .........................................................................................6-12

References..........................................................................................................................6-22

7 CHEMISTRY IMPACT OF PLANT OPERATING PRACTICES.............................................7-1 Plant Operating Strategy.......................................................................................................7-1 RWCU Operation ..................................................................................................................7-2 Condensate Polishing Practices............................................................................................7-3 Recycle or Discharge of Processed Radwaste Liquids.........................................................7-4 References............................................................................................................................7-5

8 CHEMISTRY DATA SUMMARY AND ANALYSIS FOR FUEL RELIABILITY MONITORING............................................................................................................................8-1

Summary of Recent Fuel Failures and Anomalies ................................................................8-1 Industry Data Trends.............................................................................................................8-5

Reactor Water Metals.......................................................................................................8-5 Feedwater Metals .............................................................................................................8-8 Feedwater Iron/Zinc Ratio ..............................................................................................8-12 Reactor Water Silica.......................................................................................................8-12

NMCA..................................................................................................................................8-13 Metals Mass Balance Results .............................................................................................8-14 Detailed Results for Selected Plants ...................................................................................8-22

Browns Ferry 2 ...............................................................................................................8-22 Browns Ferry 3 ...............................................................................................................8-30 River Bend......................................................................................................................8-38 Vermont Yankee.............................................................................................................8-46

Summary Matrix of Plants with Recent Corrosion-Related Fuel Failures ...........................8-53 References..........................................................................................................................8-56

9 CONCLUSION........................................................................................................................9-1

A LIST OF PLANT ABBREVIATIONS..................................................................................... A-1

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LIST OF FIGURES

Figure 5-1 Sample Points: BWR with Cascaded Drains ............................................................5-5 Figure 5-2 Sample Points: BWR with Forward-Pumped Drains.................................................5-6 Figure 5-3 Sample Points: BWR Typical Refueling Outage Line-ups........................................5-7 Figure 5-4 Percent of BWRs Meeting or Exceeding Sampling Frequencies in EPRI BWR

Water Chemistry Guidelines 2000 Revision..................................................................5-11 Figure 5-5 BWR Reactor Water Anions Analysis (39 BWRs) ..................................................5-12 Figure 5-6 BWR Reactor Water and Feedwater Metals Analysis (39 BWRs).........................5-12 Figure 6-1 Limerick 1 Reactor Water Conductivity Early Cycle 2 ...........................................6-3 Figure 6-2 Limerick 1 Reactor Water pH Early Cycle 2 ..........................................................6-4 Figure 6-3 Limerick 1 Reactor Water Chloride and Sulfate Early Cycle 2 ..............................6-4 Figure 6-4 Reactor Coolant Chemistry Response to Columbia Generating Station EHC

Fluid Ingress.......................................................................................................................6-5 Figure 6-5 Duane Arnold February 2003 Condenser Tube Leak...............................................6-6 Figure 6-6 River Bend Sulfate Excursion (January 2003)..........................................................6-8 Figure 6-7 Monticello Sulfate Trend (September 2000 September 2001) ..............................6-9 Figure 6-8 Susquehanna 2 Response to HWC Trip (10/9/04) .................................................6-10 Figure 6-9 FitzPatrick Chromate Spike, February 2000...........................................................6-11 Figure 6-10 Peach Bottom 3 Sulfate Response to HWC Trip, July 2004.................................6-11 Figure 6-11 Hatch 1 Cycle 21 Shutdown Reactor Water Zinc .................................................6-12 Figure 6-12 Hatch 1 Cycle 21 Shutdown Reactor Water Anions and TOC..............................6-13 Figure 6-13 Hatch 1 Cycle 21 Shutdown Reactor Water Chromium-51 ..................................6-13 Figure 6-14 Hatch 1 Cycle 21 Shutdown Reactor Water Manganese-54 ................................6-14 Figure 6-15 Hatch 1 Cycle 21 Shutdown Reactor Water Cobalt-58.........................................6-14 Figure 6-16 Hatch 1 Cycle 21 Shutdown Reactor Water Cobalt-60.........................................6-15 Figure 6-17 Hatch 1 Cycle 21 Shutdown Reactor Water Iron-59.............................................6-15 Figure 6-18 Hatch 1 Cycle 21 Shutdown Reactor Water Zinc-65 ............................................6-16 Figure 6-19 Hatch 1 Cycle 22 Startup Reactor Water Zinc......................................................6-16 Figure 6-20 Hatch 1 Cycle 22 Startup Reactor Water Anions and TOC..................................6-17 Figure 6-21 Browns Ferry 3 Cycle 11 Shutdown through Cycle 12 Startup Reactor Water

Anions ..............................................................................................................................6-18 Figure 6-22 Browns Ferry 3 Cycle 11 Shutdown through Cycle 12 Startup Reactor Water

Cations and TOC .............................................................................................................6-18

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Figure 6-23 Browns Ferry 3 Cycle 11 Shutdown through Cycle 12 Startup Reactor Water Chromium-51 ...................................................................................................................6-19

Figure 6-24 Browns Ferry 3 Cycle 11 Shutdown through Cycle 12 Startup Reactor Water Manganese-54 .................................................................................................................6-19

Figure 6-25 Browns Ferry 3 Cycle 11 Shutdown through Cycle 12 Startup Reactor Water Cobalt-58..........................................................................................................................6-20

Figure 6-26 Browns Ferry 3 Cycle 11 Shutdown through Cycle 12 Startup Reactor Water Cobalt-60..........................................................................................................................6-20

Figure 6-27 Browns Ferry 3 Cycle 11 Shutdown through Cycle 12 Startup Reactor Water Iron-59..............................................................................................................................6-21

Figure 6-28 Browns Ferry 3 Cycle 11 Shutdown through Cycle 12 Startup Reactor Water Zinc-65 .............................................................................................................................6-21

Figure 8-1 Cycle Average Reactor Water Iron (most recent complete cycle) ............................8-6 Figure 8-2 Cycle Average Reactor Water Chromium (most recent complete cycle)..................8-6 Figure 8-3 Cycle Average Reactor Water Nickel (most recent complete cycle) ........................8-7 Figure 8-4 Cycle Average Reactor Water Copper (most recent complete cycle) ......................8-7 Figure 8-5 Cycle Average Reactor Water Zinc (most recent complete cycle) ...........................8-8 Figure 8-6 Cycle Average Feedwater Iron (most recent complete cycle) ..................................8-9 Figure 8-7 Cycle Average Feedwater Chromium (most recent complete cycle)......................8-10 Figure 8-8 Cycle Average Feedwater Nickel (most recent complete cycle).............................8-10 Figure 8-9 Cycle Average Feedwater Copper (most recent complete cycle) ..........................8-11 Figure 8-10 Cycle Average Feedwater Zinc (most recent complete cycle)..............................8-11 Figure 8-11 Cycle Average Feedwater Iron/Zinc and Iron/(Nickel + Copper + Zinc) ...............8-12 Figure 8-12 2003 Average Reactor Water Silica .....................................................................8-13 Figure 8-13 Noble Metals Loading on Fuel..............................................................................8-14 Figure 8-14 Cycle Metals Deposition Normalized to Fuel Surface Area..................................8-18 Figure 8-15 Cycle Copper + Zinc Deposition Normalized to Fuel Surface Area......................8-18 Figure 8-16 Iron Deposition vs. Cycle Median Feedwater Iron................................................8-19 Figure 8-17 Copper Deposition vs. Cycle Median Feedwater Copper.....................................8-20 Figure 8-18 Zinc Deposition vs. Cycle Median Feedwater Zinc...............................................8-20 Figure 8-19 Copper + Zinc Deposition vs. Cycle Median Copper + Zinc.................................8-21 Figure 8-20 Feedwater Iron/(Nickel + Copper + Zinc) .............................................................8-21 Figure 8-21 Calculated Deposition Metals Ratio vs. Feedwater Metals Concentration

Ratio.................................................................................................................................8-22 Figure 8-22 Browns Ferry 2 Cycle Metals Deposition Profile...................................................8-24 Figure 8-23 Browns Ferry 2 Cycle 11 Metals Mass Balance Results ......................................8-25 Figure 8-24 Browns Ferry 2 Cycle 12 Metals Mass Balance Results ......................................8-26 Figure 8-25 Browns Ferry 2 Reactor Water Conductivity and Power ......................................8-28 Figure 8-26 Browns Ferry 2 Reactor Water Anions .................................................................8-28 Figure 8-27 Browns Ferry 2 Reactor Water Silica ...................................................................8-29

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Figure 8-28 Browns Ferry 2 CDI Conductivity .........................................................................8-29 Figure 8-29 Browns Ferry 3 Cycle Metals Deposition Profile...................................................8-32 Figure 8-30 Browns Ferry 3 Cycle 9 Metals Mass Balance Results ........................................8-33 Figure 8-31 Browns Ferry 3 Cycle 10 Metals Mass Balance Results ......................................8-34 Figure 8-32 Browns Ferry 3 Cycle 11 Metals Mass Balance Results ......................................8-35 Figure 8-33 Browns Ferry 3 Reactor Water Conductivity and Power ......................................8-36 Figure 8-34 Browns Ferry 3 Reactor Water Anions .................................................................8-37 Figure 8-35 Browns Ferry 3 Reactor Water Silica ...................................................................8-37 Figure 8-36 Browns Ferry 3 CDI Conductivity .........................................................................8-38 Figure 8-37 River Bend Cycle Metals Deposition Profile .........................................................8-41 Figure 8-38 River Bend Cycle 8 Metals Mass Balance Results...............................................8-42 Figure 8-39 River Bend Cycle 11 Metals Mass Balance Results.............................................8-43 Figure 8-40 River Bend Reactor Water Conductivity and Power.............................................8-44 Figure 8-41 River Bend Reactor Water Anions........................................................................8-45 Figure 8-42 River Bend Reactor Water Silica ..........................................................................8-45 Figure 8-43 River Bend CDI Conductivity ................................................................................8-46 Figure 8-44 Vermont Yankee Cycle Metals Deposition Profile ................................................8-48 Figure 8-45 Vermont Yankee Cycle 21 Metals Mass Balance Results....................................8-49 Figure 8-46 Vermont Yankee Cycle 22 Metals Mass Balance Results....................................8-50 Figure 8-47 Vermont Yankee Reactor Water Conductivity and Power ....................................8-51 Figure 8-48 Vermont Yankee Reactor Water Anions...............................................................8-52 Figure 8-49 Vermont Yankee Reactor Water Silica .................................................................8-52 Figure 8-50 Vermont Yankee CDI Conductivity .......................................................................8-53 Figure 8-51 Summary of Average Mass Deposition of Failed Fuel During First Cycle of

Exposure for Plants with Corrosion-Related Fuel Failures...............................................8-54

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LIST OF TABLES

Table 3-1 General Plant Design Data ........................................................................................3-4 Table 3-2 Power Uprate.............................................................................................................3-5 Table 3-3 Percent Change in Condensate Pump Discharge Iron with Power Uprate................3-8 Table 3-4 Plant Configuration ....................................................................................................3-9 Table 3-5 Main Condenser Materials and Condensate Temperature......................................3-11 Table 3-6 Main Condenser Cooling Data.................................................................................3-13 Table 3-7 Materials of Construction: Feedwater, Extraction Steam, Recirculation and

Reactor Water Cleanup Systems.....................................................................................3-15 Table 3-8 Condenser, Piping, Control Rod Blades, and Turbine Replacements .....................3-18 Table 3-9 System Flows and Reactor Liquid Mass Inventory..................................................3-19 Table 3-10 BWR Chemistry Regimes ......................................................................................3-21 Table 4-1 Typical Main Condenser Cooling Water Chloride and Sulfate Concentrations..........4-5 Table 4-2 Closed Cooling and Auxiliary Boiler Chemicals.......................................................4-14 Table 4-3 Zinc Pellet Impurity Specification.............................................................................4-21 Table 4-4 Typical Hydrogen Purity...........................................................................................4-21 Table 4-5 BWR Feedwater Iron Injection.................................................................................4-23 Table 4-6 Typical Impurities in Reagent Grade Ferric Oxide (Fe2O3).......................................4-23 Table 4-7 BWR Chemical Decontaminations...........................................................................4-27 Table 5-1 Normal Steam/Water Cycle Sample Location for Initial Detection of Chemical

Impurities..........................................................................................................................5-14 Table 5-2 Normal Auxiliary System Sample Location for Initial Detection of Chemical

Impurities..........................................................................................................................5-15 Table 5-3 Normal Steam/Water Cycle Sample Location for Monitoring Chemical

Additives...........................................................................................................................5-15 Table 8-1 Reported BWR Fuel Failures (1997 through September 2004).................................8-2 Table 8-2 BWR Corrosion-Induced Fuel Failures or Anomalies ................................................8-3 Table 8-3 BWR Fuel Surveillance Results.................................................................................8-4 Table 8-4 Calculated Metals Deposition on Fuel .....................................................................8-16 Table 8-5 Browns Ferry 2 Milestones ......................................................................................8-23 Table 8-6 Browns Ferry 2 Calculated Metals Deposition on Fuel ............................................8-23 Table 8-7 Browns Ferry 3 Milestones ......................................................................................8-31 Table 8-8 Browns Ferry 3 Calculated Metals Deposition on Fuel ............................................8-31

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Table 8-9 River Bend Milestones.............................................................................................8-39 Table 8-10 River Bend Fuel Failures .......................................................................................8-40 Table 8-11 River Bend Calculated Metals Deposition on Fuel ................................................8-40 Table 8-12 Vermont Yankee Milestones..................................................................................8-47 Table 8-13 Vermont Yankee Calculated Metals Deposition on Fuel .......................................8-47 Table 8-14 Summary Information for Plants with Recent Corrosion-Related Fuel Failures.....8-54

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1 INTRODUCTION

The EPRI BWR Water Chemistry Guidelines 2004 Revision [1] provides the framework and recommendations for chemistry monitoring and actions. The main emphasis is on chemistry control for minimization of IGSCC (intergranular stress corrosion cracking) and IASCC (irradiation-assisted stress corrosion cracking) of reactor vessel internals and primary system piping and components, fuel reliability, radiation dose control, and FAC (flow accelerated corrosion) control. Due to fuel corrosion issues over the past several years, the BWR Water Chemistry Guidelines has been strengthened to include tighter chemistry control limits and additional monitoring for contaminants and additives that can have an adverse effect on fuel cladding corrosion.

Water chemistry has been identified as a known or potential contributing cause in recent corrosion-induced fuel failures and anomalies such as fuel crud spallation and enhanced nodular corrosion. This was unexpected because advances in fuel cladding corrosion resistance and improved water quality led to the period lasting for most of the 1990s during which no industry-wide cladding corrosion fuel failures were experienced. However, since the late 1990s, a number of cladding corrosion-induced fuel failures have occurred and enhanced nodular corrosion indications have been observed while plants operated within established water chemistry guidelines. During this period, several operating and chemistry changes occurred, including:

Increased fuel duty (higher efficiency fuel designs, power uprates, higher discharge burn-up, longer operation cycle length) to improve cycle economics.

Noble Metal Chemical Application (NMCA), in combination with hydrogen injection, producing a highly reducing chemistry environment for IGSCC mitigation. All U.S. BWRs now operate under low ECP HWC (Hydrogen Water Chemistry) conditions, with either moderate-HWC or NMCA/HWC.

Increased zinc injection to control drywell shutdown dose rates as fuel crud restructures during the transition to a highly reducing chemistry environment.

Except for the River Bend Cycle 8 failures, where the cause was identified as Zircaloy corrosion beneath areas of heavy corrosion product deposits, and the River Bend Cycle 11 failures that were attributed to heavy deposits of tenacious crud [1], the causes of recent corrosion failures have not been identified. EPRI and the BWR chemistry community as a whole recognize the severe economic and operational impact of the fuel corrosion issues and the possibility of a chemistry influence. It is also recognized that aggressive operating conditions and non-optimal cladding alloying material can make the fuel more susceptible to corrosion [2]. Consequently, some plants have taken special actions to monitor for chemical impurities more frequently and for more species, during non-steady state operating conditions such as startups and shutdowns, to

1-1

Introduction

detect and quantify any chemical intrusions that might otherwise not be noticed. Mass balances are being performed to estimate corrosion products deposition on the fuel during steady state and non-steady state conditions to compare the magnitude and composition of the deposits at different plants and at the same plant during cycles with and without fuel issues. Some species previously thought to have no significant potential detrimental impact on fuel at concentrations at concentrations typically present in reactor coolant at power operating conditions are being reconsidered. For example, silica is being evaluated based on the identification of zinc silicate crystals within crud samples taken from some plants [2].

Given the wide range of current issues and unknowns, communication between fuels and chemistry personnel is especially important. It is of particular value for fuels personnel to have an understanding of the level of vigilance of todays BWR chemistry monitoring and control programs. In addition, it is important to disseminate chemistry results, which may hold insights into identifying or eliminating a potential impact on fuel reliability, to fuel experts.

Toward this goal, this report documents plant design features and operating practices that have an influence on or are impacted by plant chemistry. In addition, current actual BWR water chemistry monitoring practices and potential sources of impurities are addressed, with emphasis on those areas potentially related to fuel reliability. Chemistry transients are discussed and examples are given, and results of chemistry analyses and mass balances performed specifically for fuel reliability monitoring are presented. The source of data is the EPRI BWR Chemistry Monitoring Database, including the results of various ancillary surveys performed to support the database effort. The database currently encompasses 39 operating BWR units, including the 34 U.S. units, 2 Mexican BWRs and 3 European BWRs.

References

1. BWR Water Chemistry Guidelines 2004 Revision, EPRI, Palo Alto, 2004. TR-1008129. 2. Keys, T.A. and Jim Lemons, Fuel Corrosion Failures in the Browns Ferry Nuclear Plant,

International Conference: Water Chemistry of Nuclear Reactor Systems, San Francisco, October 11 14, 2004.

1-2

2 OBJECTIVES

The main objectives of this report are to:

Provide a tutorial for the BWR Fuel Reliability Program on BWR chemistry monitoring and control approaches with the goal of enhancing communication between fuels and chemistry personnel

Summarize plant design characteristics, chemistry regimes, operating practices, and sources of impurities that impact plant chemistry and have a known or potential influence on fuel reliability

Review industry operating experience under plant transient conditions to document the types and levels of chemical impurities

Summarize plant chemistry data and calculated metals deposition results for several plants, concentrating on those with fuel corrosion issues

An overview of the report sections and their content is as follows:

Section 1 Introduction: Provides an brief overview of current fuel issues, potential chemistry impact and responses

Section 2 Objectives

Section 3 Plant Design Characteristics: Provides tabulations of plant design data, particularly those that have a known or potential influence on plant chemistry.

Section 4 Sources and Impact of Chemical Inputs: Provides a summary of the sources, generation, ingress, and impact of objectionable impurities, chemical additives, and maintenance chemicals.

Section 5 BWR Monitoring and Control Practices: Chemistry monitoring approaches, normal sample locations, and actual practices are summarized, along with challenges for future monitoring.

Section 6 Chemistry Transients: Types and examples of chemistry transients are summarized based on industry operating experience. Examples include condenser cooling water ingress, ion exchange resin leakage, EHC (electro-hydraulic control) fluid ingress, cutting oil and turbine lube oil intrusions, and hydrogen injection trips.

2-1

Objectives

Section 7 Chemistry Impact of Plant Operating Practices: The effects on plant chemistry of plant operation and operating practices of key systems, such as RWCU, condensate polishers and liquid radwaste, are addressed.

Section 8 Chemistry Data Summary and Analysis for Fuel Reliability Monitoring: Summarizes recent findings of fuel failures and anomalies; provides cycle chemistry data and mass balance results of cycle metals deposition on fuel for comparison of plants; provides specific information for plants with corrosion-induced fuel failures.

2-2

3 BWR PLANT DESIGN CHARACTERISTICS

General Plant Design Data

BWR plant design characteristics are summarized in this section for use in making comparisons among plants. General plant data, including the GE BWR model, date of initial commercial operation, and power rating information are summarized in Table 3-1. The original licensed thermal power and the current power rating are also shown.

Power Uprate

As shown in Table 3-1, most plants have had and/or are planning for a power uprate of some type. The date of each power uprate, the magnitude and type are given in Table 3-2. Power uprates, particularly extended power uprates, have a significant impact on fuel due to the increased duty. In addition, the increased steam/water cycle flow rates tend to increase flow accelerated corrosion (FAC) rates and, hence, crud transport. Chemistry monitoring data do not indicate a significant increase in corrosion of feedwater piping and equipment. Higher FAC rates in steam and drain piping and components are indicated by the increase in condensate pump discharge (CPD) iron, as shown in Table 3-3. Although the increase in CPD iron has been significant, the impact of power uprates on feedwater corrosion product concentrations has been relatively low, generally due to plant design changes to improve corrosion products removal. For example, plants with Deep Bed Only condensate polishing have added prefilters, reducing feedwater metals concentrations. Plants using Filter Demineralizers for condensate polishing added or modified vessels to maintain or reduce process velocities at the power uprate conditions, providing the capability to maintain or reduce effluent concentrations.

The increase in condensate flow rate from a power uprate is often accompanied by an increase in condensate temperature. Either of these conditions tends to increase the soluble impurities in the condensate polishing system effluent and thus the feedwater. The impact is magnified when both the flow and temperature increase. The effluent concentrations of divalent anions (such as sulfate) and cations (such as calcium and magnesium), which are often limited by ion exchange kinetics, can increase particularly under conditions of a small, chronic condenser leak. As condensate temperature increases, the effluent concentrations of monovalent ions (such as chloride and sodium) tend to increase due to the increased dissociation of water, which produces more hydrogen and hydroxide ions, that compete for ion exchange sites with the ionic impurities. The increased temperature also increases the decomposition of ion exchange resins used in the condensate polishing system, increasing feedwater concentrations of sulfate and organic sulfur species (from cation resin decomposition) and amines and alcohols (from anion resin decomposition). Plants that have performed extended power uprates have not in all cases

3-1

BWR Plant Design Characteristics

upgraded the RWCU system to compensate for the increased impurity levels in the final feedwater.

Plant Configuration

Plant configuration parameters are summarized in Table 3-4. The drains path (cascaded or forward-pumped) has an impact on impurity and corrosion product concentrations in the final feedwater. With cascaded drains, the concentrations of inorganic and organic impurities in the condensate polishing system common effluent are normally the main inputs to final feedwater. Organic impurities may partially or totally thermally decompose in the feedwater train from the temperature increase as they are transported through the feedwater heaters. The mass rate of corrosion products transport (mainly iron and also copper at plants with copper-alloy condenser tubes) from the final feedwater to the reactor is also predominantly from the condensate polishing system effluent (the corrosion rate of the feedwater piping and components is relatively low). The dissolved oxygen concentration in the condensate is also normally approximately equal to that of the final feedwater at plants with cascaded drains. Plants injecting oxygen to meet feedwater dissolved oxygen control requirements normally inject either air or compressed oxygen into the condensate pump suction line. For plants with hydrogen water chemistry (HWC), hydrogen is typically injected into the suction of the feed pumps.

At plants with forward pumped drains, condensate from the last stage feedwater heaters, moisture separators and steam reheaters (if equipped) is collected and injected into the feedwater at a point where drain and feedwater temperatures are about equal. This stream typically does not contribute a significant quantity of inorganic or organic chemical impurities to the reactor coolant. The dissolved oxygen concentration tends to be high, due to partitioning of the oxygen carried over from the reactor vessel with the steam, and therefore normally produces an increase in the final feedwater dissolved oxygen compared with that of the condensate. For plants with carbon steel piping and components in the lines leading to the forward pumped drains, this stream can be a significant source of final feedwater iron. In contrast, at plants with corrosion resistant materials (such as chrome-moly steel), the iron concentration in the forward pumps drains is normally


F/D = Filter Demineralizer: This configuration includes filters that are precoated with materials containing powdered ion exchange resins, and are capable of providing low effluent iron concentrations with low tolerance to condenser leaks. For plants with copper-alloy condenser tubes, the copper removal capability by the F/D is limited.

The RWCU purification equipment configuration for each plant is also summarized in Table 3-4. Most plants have F/Ds (filter demineralizers) for reactor water purification, but four plants have DBs (deep bed demineralizers), either alone or downstream of F/Ds. Plants with deep beds in RWCU typically have the lowest steady state reactor water silica concentrations.

The fuel surface area is also given in Table 3-4. These values are used in normalizing crud deposition estimates to an average surface area basis. The most recent reported value is shown.

Materials of Construction

Main condenser materials of construction are summarized in Table 3-5. Copper-alloy condenser tubes contribute significantly to the copper concentration in the condensate pump discharge stream (concentrations of 2 to >5 ppb). The most common condenser tube materials are titanium and stainless steel. The most common shell material is carbon steel. The maximum, average and minimum condensate temperatures are also given in Table 3-5.

Information concerning the main condenser cooling water source and cooling tower use is given in Table 3-6. Seasonal (spring/summer and fall/winter) conductivity data for the cooling water are also given. The conductivity values provide an indication of the impact of condenser leaks at different plants. Cooling water conductivity ranges from


Chemistry Regime

Implementation dates for hydrogen water chemistry (HWC), zinc injection (NZO/DZO), and noble metals chemical application (NMCA) are shown in Table 3-10. Type of zinc injection (active or passive) and NMCA loading on fuel surface is also shown.

Table 3-1 General Plant Design Data

Plant BWR Model Commercial Operation DateOriginal Power

(MWe/MWth) Current Power

(MWe/MWth)

Browns Ferry 2 BWR 4/Type 4g (Mark I) Mar-75 1098/3293 1152/3458

Browns Ferry 3 BWR 4/Type 4g (Mark I) Mar-77 1098/3293 1152/3458

Brunswick 1 BWR 4/Type 5g (Mark II) Mar-77 821/2436 958/2929

Brunswick 2 BWR 4/Type 5g (Mark II) Nov-75 821/2436 895/2558

Clinton BWR/Type 5h (Mark III) Apr-87 985/2894 1182/3473

Cofrentes BWR 6/ (Mark-III) Mar-85 975/2895 1102/3236

Columbia BWR 5/Type 4g (Mark II) Dec-84 1154/3323 1180/3486

Cooper BWR 4/Type 4g (Mark I) Jul-74 1154/3323 801/2381

Dresden 2 BWR 3/Type 4g (Mark I) Jun-70 833/2527 912/2957

Dresden 3 BWR 3/Type 4g (Mark I) Nov-71 833/2527 912/2957

Duane Arnold BWR 4/Type 4g (Mark I) Feb-75 515/1593 565/1658

Fermi 2 BWR 4/Type 4g (Mark I) Jan-88 1093/ 1150/3430

FitzPatrick BWR 4/Type 4g (Mark I) Jul-75 780/2436 860/2536

Grand Gulf BWR 6/Type 5h (Mark III) Jul-85 1250/3833 1250/3898

Hatch 1 BWR 4 (Mark I) Dec-75 810/2436 910/2763

Hatch 2 BWR 4/Type 4g (Mark I) Sep-79 810/2436 920/2763

Hope Creek BWR 4/Type 4g (Mark I) Dec-86 1117/3293 1136/3339

Laguna Verde 1 BWR 5 (Mark II) Jul-90 654/1931 /2027

Laguna Verde 2 BWR 5 (Mark II) Apr-95 654/1931 /2027

LaSalle 1 BWR 5/Type 4g (Mark I) Jun-82 1140/3323 1200/3489

LaSalle 2 BWR 5/Type 4g (Mark I) Mar-84 1140/3323 1200/3489

Leibstadt BWR 6 Dec-84 960/3012 1230/3600

Limerick 1 BWR 4/Type 5g (Mark II) Feb-86 1055/3293 1200/3458

Limerick 2 BWR 4/Type 5g (Mark II) Jan-90 1055/3293 1200/3458

3-4


Table 3-1 (continued) General Plant Design Data

Plant BWR Model Commercial Operation DateOriginal Power

(MWe/MWth) Current Power

(MWe/MWth)

Monticello BWR 3/Type 4g (Mark I) Jun-71 576/1670 616/1775

Mhleberg 1973 372/1096 372/1096

Nine Mile Point 1 BWR 2/Type g (Mark I) Dec-69 610/1850 610/1850

Nine Mile Point 2 BWR 5/Type 5g (Mark II) Apr-88 1080/3323 1207/3467

Oyster Creek BWR 2/Type 4g (Mark I) Dec-69 640/1930 640/1930

Peach Bottom 2 BWR 4/Type 4g (Mark I) Jul-74 1080/3293 1159/3514

Peach Bottom 3 BWR 4/Type 4g (Mark I) Dec-74 1080/3293 1159/3514

Perry BWR 6/Type 5h (Mark III) Nov-87 1244/3579 1306/3514

Pilgrim BWR 3/Type 4g (Mark I) Dec-72 687/1998 687/2028

Quad Cities 1 BWR 3/Type 4g (Mark I) Feb-73 833/2511 912/2957

Quad Cities 2 BWR 3/Type 4g (Mark I) Mar-73 833/2527 912/2957

River Bend BWR 6/Type 5h (Mark III) Jun-86 986/2894 1086/3091

Susquehanna 1 BWR 4/Type 5g (Mark II) Jun-83 1050/3293 1220/3489

Susquehanna 2 BWR 4/Type 5g (Mark II) Feb-85 1050/3293 1220/3489

Vermont Yankee BWR 4/Type 4g (Mark I) Nov-72 540/1593 540/1593

Table 3-2 Power Uprate

Plant Commercial Operation Start Date

Original or Starting Power (MWth)

Uprate Date

Power Increase (% MWth)

Power Increase

(MWth)

Uprate Type

Current Power (MWth)

3293 Apr-99 5 164 S Browns Ferry 2 Mar-75

3458 future 15 E 3458

3293 Oct-98 5 164 S Browns Ferry 3 Mar-77

3458 Future 15 E 3458

2436 1997 5 122 S Brunswick 1 Mar-77

2558 2002 15 365 E 2929

2436 1996 5 122 S Brunswick 2 Nov-75

2558 2003 15 365 E 2929

Clinton Apr-87 2894 2002 20 580 E 3473

3-5


Table 3-2 (continued) Power Uprate



Uprate Date


Power Increase

(MWth)

Uprate Type


2895 Apr-88 2 57

2952 Mar-98 2.1 63

3015 Jun-02 5.6 169 Cofrentes Mar-85

3184 Oct-03 1.6 52

3236

Columbia Dec-84 3323 1995 4.9 163 S 3486

Cooper Jul-74 2381 Future 21.8 E 2381

Dresden 2 Aug-70 2527 Dec-01 17 430 E 2957

Dresden 3 Nov-71 2527 Oct-02 17 430 E 2957

1593 Aug-85 4.1 65 S Duane Arnold Feb-75

1658 Approved 15 248 E 1658

Sep-92 4 137 S Fermi 2 Jan-88

Nov-96 3430

FitzPatrick Jul-75 2436 Jan-97 4 100 S 2536

3833 Oct-02 1.7 65 MU Grand Gulf Jul-85

3898 Future 12 E 3898

2436 1996 5 122 S

2558 Sep-99 8 205 E Hatch 1 Dec-75

2763 Approved 1.5 41 MU

2763

2436 1995 5 122 S

2558 Dec-98 8 205 E Hatch 2 Sep-79

2763 Approved 1.5 41 MU

2763

Hope Creek Dec-86 3293 Aug-01 1.4 46 MU 3339

Laguna Verde 1 Jul-90 1931 Jun-99 5 96 S 2027

Laguna Verde 2 Apr-95 1931 Jul-99 5 96 S 2027

LaSalle 1 Jun-82 3323 2001 5 166 S 3489

LaSalle 2 Mar-84 3323 2001 5 166 S 3489

3012 1985 1 26

3138 Oct-98 6.3 189

3327 Sep-99 2.8 93

3420 Oct-00 2.8 95

Leibstadt Dec-84

3515 Sep-02 2.4 85

3600

3-6


Table 3-2 (continued) Power Uprate



Uprate Date


Power Increase

(MWth)

Uprate Type


3293 1995 5 165 S Limerick 1 Feb-86

3458 2000 5 3458

3293 1995 5 165 S Limerick 2 Jan-90

3458 2000 5 3458

Monticello Jun-71 1670 Oct-98 6.3 105 E 1775

Mhleberg 1973 1096

Nine Mile Point 1 Dec-69 1850 1850

Nine Mile Point 2 Apr-88 3323 1995 4.3 144 S 3467

Oyster Creek Dec-69 1930 1930

3293 Oct-96 5 165 S Peach Bottom 2 Jul-74

3458 2002 1.62 56 MU 3514

3293 Oct-95 5 165 S Peach Bottom 3 Dec-74

3458 2002 1.62 56 MU 3514

Perry Nov-87 3579 Jun-00 5 178 S 3758

Pilgrim Dec-72 1998 Jun-03 1.5 30 MU 2028

Quad Cities 1 Feb-73 2511 Dec-02 17.8 446 E 2957

Quad Cities 2 Mar-73 2527 Dec-02 17.8 446 E 2957

2894 Oct-00 5 145 S River Bend Jun-86

3039 May-03 1.7 52 MU 3091

3293 Apr-95 4.5 148 S Susquehanna 1 Jun-83

3441 2001 1.4 48 MU 3489

3293 Jun-94 4.5 148 S Susquehanna 2 Feb-85

3441 2001 1.4 48 MU 3489

Vermont Yankee Nov-72 1593 1593 Notes: E = Extended

MU = Measurement Uncertainty Recapture

S = Stretch

3-7


Table 3-3 Percent Change in Condensate Pump Discharge Iron with Power Uprate

All Plants Plants with Reheat Capability Plants without

Reheat Capability Power Uprate (MWth Percent Increase) Average Change in CPD

Iron Concentration (%) (Note 1)

10 37.7 NA 35.7

All 17.5 11.5 24.4

Number of Plants

Number with Increased in CPD Iron 13 7 6

Number with decrease in CPD Iron 2 2 0

Notes: 1. Plants with decrease not included in statistics.

3-8


Table 3-4 Plant Configuration

Plant Drains Path Reheat (Yes/No) Condensate

Polishing TypeRWCU Type

Fuel Surface Area (m2) (Note 1)

Browns Ferry 2 Cascaded No F/D F/D 8276

Browns Ferry 3 Cascaded No F/D F/D 8276

Brunswick 1 FPD Yes Filter + DB F/D

Brunswick 2 FPD Yes Filter + DB F/D

Clinton Cascaded Yes Partial Filter + DB (Note 2) F/D

Cofrentes FPD Yes F/D F/D 6708.9

Columbia Cascaded Yes F/D F/D 8181

Cooper Cascaded No F/D F/D 5422

Dresden 2 Cascaded No Partial Filter + DB (Note 3) DB 6811

Dresden 3 Cascaded No Partial Filter + DB (Note 3) DB 6811

Duane Arnold Cascaded Yes F/D F/D 3242

Fermi 2 FPD Yes F/D F/D

FitzPatrick Cascaded Yes DB F/D 6047

Grand Gulf FPD Yes DB F/D

Hatch 1 Cascaded Yes F/D F/D 5098

Hatch 2 Cascaded Yes F/D F/D 5098

Hope Creek Cascaded No Filter + DB F/D 8979

Laguna Verde 1 FPD Yes Filter + DB F/D

Laguna Verde 2 FPD Yes Filter + DB F/D

LaSalle 1 FPD Yes Filter + DB F/D 6731

LaSalle 2 FPD Yes Filter + DB F/D 6731

Leibstadt Combination Yes F/D F/D

Limerick 1 Cascaded No Filter + DB F/D 7312

Limerick 2 Cascaded No Filter + DB F/D 7312

Monticello Cascaded No F/D F/D 4596

Mhleberg Cascaded Yes F/D 2450

3-9


Table 3-4 (continued) Plant Configuration

Plant Drains Path Reheat (Yes/No) Condensate

Polishing TypeRWCU Type

Fuel Surface Area (m2) (Note 1)

Nine Mile Point 1 Cascaded Yes DB F/D + DB 5096

Nine Mile Point 2 FPD Yes DB F/D

Oyster Creek Cascaded Yes DB F/D + DB

Peach Bottom 2 Cascaded No F/D F/D 7361

Peach Bottom 3 Cascaded No F/D F/D 7357

Perry FPD Yes Filter + DB F/D 7895

Pilgrim Cascaded No DB F/D 6265

Quad Cities 1 Cascaded No F/D F/D 6265

Quad Cities 2 Cascaded No F/D F/D

River Bend FPD Yes Filter + DB F/D 6282

Susquehanna 1 Cascaded No Filter + DB F/D 8042

Susquehanna 2 Cascaded No Filter + DB F/D 8042

Vermont Yankee Cascaded No F/D F/D 3789

Notes: 1. Fuel surface area is latest provided. 2. 6 of 9 deep beds have slaved prefilters. 3. 40% headered filtration.

3-10


Table 3-5 Main Condenser Materials and Condensate Temperature

Condensate Temperature (oF)Plant Tubes Shell Tubesheets

Max. Min. Avg.

Browns Ferry 2 SS CS Carbon steel 130 80 105

Browns Ferry 3 SS CS Carbon steel 130 80 105

Brunswick 1 Titanium CS Aluminum bronze 135 90 100

Brunswick 2 Titanium CS Aluminum bronze 135 90 100

Clinton 304 SS CS Copper nickel 110 90 96

Cofrentes Titanium CS Titanium 135 105 125

Columbia Admiralty/ Copper Nickel CS 115 80 92

Cooper SS CS Aluminum bronze 130 90 120

Dresden 2 304 SS CS 125 70 110-115

Dresden 3 304 SS CS 125 80 110-115

Duane Arnold 304 SS A-36 CS 135 90 100

Fermi 2 Titanium CS 130 90 110

FitzPatrick

Admiralty brass w/titanium

impingement tubes

CS Muntz metal 125 83 110

Grand Gulf 304 SS CS CS 136 106.6 124.2

Hatch 1 Titanium CS 125 110 115

Hatch 2 Titanium CS 125 110 115

Hope Creek Titanium CS 135 95 135

(Summer) 95 (Winter

Laguna Verde 1

Cu-Ni (90-10) (70-30) (SB-

111-706)(SB-1) 1-7

CS SA-515-70 122 107.6 118.4

Laguna Verde 2

Cu-Ni (90-10) (70-30) (SB-

111-706)(SB-1) 1-7

CS SA-515-70 122 107.6 118.4

LaSalle 1 304 SS CS 135 100 115

LaSalle 2 304 SS CS 135 100 115

3-11


Table 3-5 (continued) Main Condenser Materials and Condensate Temperature

Condensate Temperature (oF)Plant Tubes Shell Tubesheets

Max. Min. Avg.

Leibstadt Titanium 131 113

Limerick 1 Admiralty brass CS 140 90 123

Limerick 2 Admiralty brass CS 135 110 123

Monticello 304 SS CS 135 100 110

Mhleberg Titanium (was brass)

Nine Mile Point 1 90Cu/10Ni

(11,754) Super SS (1,856)

13Cr/Mo 130 85 105

Nine Mile Point 2 Periphery 70/30 Cu/Ni the rest

Admiralty brass CS 120 90 115

Oyster Creek Titanium CS A-285C 118 50 88

Peach Bottom 2 Titanium CS 120 80 90-100

Peach Bottom 3 Titanium CS 120 80 90-100

Perry SS CS CS 130 95 110-120

Pilgrim Titanium CS 121 85 98

Quad Cities 1 SS CS SS 140 60 104

Quad Cities 2 SS CS SS 140 60 104

River Bend Admiralty brass Muntz alloy (60% Cu, 40% Zn)

123 118 120

Susquehanna 1 304 SS

ASME-SA-285 Gr.C

Cu bearing (0.25%

max) CS

137 118 96

Susquehanna 2 304 SS

ASME-SA-285 Gr.C

Cu bearing (0.25%

max) CS

138 119 98

Vermont Yankee 92% Admiralty 8% 304 SS

CS

Muntz metal

135 90 110

3-12


Table 3-6 Main Condenser Cooling Data

Average Circulating Water Conductivity (S/cm) Plant Cooling Water Source

Cooling Tower Use

Spring/Summer Fall/Winter

Browns Ferry 2 Tennessee River No 130-200 130-200

Browns Ferry 3 Tennessee River No 130-200 130-200

Brunswick 1 Cape Fear River Mouth (brackish) No Almost sea water Almost sea water

Brunswick 2 Cape Fear River Mouth (brackish) No Almost sea water Almost sea water

Clinton Clinton Lake No 409 404

Cofrentes River Jcar Yes 3000-3500 2500-3000

Columbia Columbia River Yes 660 (Brackish) 715

Cooper Missouri River No 600-700 600-700

Dresden 2 Kankakee river Yes 629 696

Dresden 3 Kankakee river Yes 629 696

Duane Arnold River Yes

Fermi 2 Lake Erie (pond) Yes 500 400

FitzPatrick Lake Ontario No 380 320

Grand Gulf Rainey (radial

wells alongside Mississippi River)

Yes 409 404

Hatch 1 Altamaha River Yes 100 80

Hatch 2 Altamaha River Yes 100 80

Hope Creek Delaware Bay Yes 1500 8000

Laguna Verde 1 Gulf of Mexico No

Laguna Verde 2 Gulf of Mexico No

LaSalle 1 Lake/River No 700-900 700-900

LaSalle 2 Lake/River No 700-900 700-900

Leibstadt Rhine River Yes

Limerick 1 River Yes 1500 1200

Limerick 2 River Yes 1500 1200

Monticello River 250-350 350

3-13


Table 3-6 (continued) Main Condenser Cooling Data

Average Circulating Water Conductivity (S/cm) Plant Cooling Water Source

Cooling Tower Use

Spring/Summer Fall/Winter

Mhleberg River

Nine Mile Point 1 Lake Ontario No ~300 ~300

Nine Mile Point 2 Lake Ontario Yes 1200 1200

Oyster Creek Bay No 30,000 30,000

Peach Bottom 2 Susquehanna River Yes 250 225

Peach Bottom 3 Susquehanna River Yes 250 225

Perry Lake Erie Yes 600-650 600-650

Pilgrim Atlantic Ocean No 30,000 30,000

Quad Cities 1 Mississippi River No 416 419

Quad Cities 2 Mississippi River No 416 419

River Bend Mississippi River (Clarifier) Yes 1995 1376

Susquehanna 1 Susquehanna River Yes 860 1000

Susquehanna 2 Susquehanna River Yes 860 1000

Vermont Yankee River Yes 120 120

3-14


Table 3-7 Materials of Construction: Feedwater, Extraction Steam, Recirculation and Reactor Water Cleanup Systems

Feedwater Heaters Plant

Tubes Shell Extraction Steam Piping Recirc. Piping RWCU Piping

Browns Ferry 2 SS CS CS 304 SS SS

Browns Ferry 3 SS CS CS 304 SS SS

Brunswick 1 304L SS CS (SA) SA-106 or A-106 Gr.B, SA-333 or A-333 Gr.6 SA-312 or SA-358 Type 304, electropolished & preoxidized

SA-312 or SA-358 Type 304, Seamless, Sch 80S

Brunswick 2 304L SS CS (SA) SA-106 or A-106 Gr.B, SA-333 or A-333 Gr.6 SA-312 or SA-358 Type 304, electropolished & preoxidized

SA-312 or SA-358 Type 304, Seamless, Sch 80S

Clinton 304 SS CS CS 304 SS CS

Cofrentes SS CS P22 & P11 low alloy steel 304 SS CS

Columbia 304 SS CS CS 304 SS CS

Cooper SS CS Some Cr/Mo, rest CS 316L seamless, electropolished & passivated 316L seamless, electropolished & passivated

Dresden 2 304 SS CS Low alloy steel Cr/Mo 304 SS 316 L SS

Dresden 3 304 SS CS Low alloy steel Cr/Mo 316 NG SS 316 L SS

Duane Arnold 304 SS 304 SS 304 SS

Fermi 2 SS CS CS. Some replaced with Cr-Mo Solution annealed austenitic 304 SS, IHSI, MSI Mostly SS, some CS

FitzPatrick 304 SS CS CS 304 SS CS

Grand Gulf SS CS CS 304 SS CS Sch 80, SA 106

Hatch 1 SS CS CS 304 SS SS

Hatch 2 SS CS CS 316 NG SS SS

Hope Creek 304 SS CS

3-15


Table 3-7 (continued) Materials of Construction: Feedwater, Extraction Steam, Recirculation and Reactor Water Cleanup Systems



Laguna Verde 1 SS SA-249 Type 304 CS SA-515-70 CS SA106 Gr.B SA-358 Type 304 CS SA106 Gr.B

Laguna Verde 2 SS SA-249 Type 304 CS SA-515-70 CS SA106 Gr.B

SA-358 Type 304

CS SA106 Gr.B

LaSalle 1 304 SS CS CS 304 SS CS

LaSalle 2 304 SS CS CS 304 SS CS

Leibstadt

Limerick 1 SA-249- 304L SS CS w/ SS overlay P11 Cr/Moly 304L SS 304 SS

Limerick 2 SA-249- 304L SS CS w/ SS overlay CS 304L SS 316L SS

Monticello

LP Heaters 304SS HP Heaters CS

Chrome alloy Extraction to 11 & 12 Htrs-304SS 13Htr-Chrome Moly 14 & 15 Htrs-Chrome Moly

Nuclear Grade 316 Modified L, induction heat stress relieved & passivated.

CS

Mhleberg

Nine Mile Point 1 304/316 SS CS CS ASTM A106 Gr B, Alloy ASTM A355 P22, ASTM A 357

316L SS SA 312/SA 358 Type 316L, ASTM A376 Type 304, CS ASTM A106GrB/SA 333 Gr 6

Nine Mile Point 2 Cu-Ni-SS CS SS/Outside |Cr-Mo 316 SS CS

Oyster Creek 304 SS A-249 CS A-285C CS A106 Gr. A & Gr. B 316 SS 316 SS

3-16


Table 3-7 (continued) Materials of Construction: Feedwater, Extraction Steam, Recirculation and Reactor Water Cleanup Systems



Peach Bottom 2 SS CS 1.25% Cr CS alloy 316 NG SS

Majority 304SS, some 316 NG SS (pump, regen HX to Vessel), CS in transition piping to FW system

Peach Bottom 3 SS CS 1.25% Cr CS alloy 316 NG SS

Majority 304SS, some 316 NG SS (pump, regen HX to Vessel), CS in transition piping to FW system

Perry SS CS CS SS SS

Pilgrim SS CS 1-1/4Cr-1/2Mo 316 SS ASTM A-312 or A-376 GR to 304 Sch 80

Quad Cities 1 SS CS CS SS SS

Quad Cities 2 SS CS CS SS SS

River Bend SS CS Cr-Mo 316 L SS Electropolished SS in Drywell; CS outside Drywell

Susquehanna 1 304 SS CS SS clad CS (mainly) and chrome-moly 304 SS CS (with short sections of 304 SS)

Susquehanna 2 304 SS CS SS clad CS (mainly) and chrome-moly 304 SS CS (with short sections of 304 SS)

Vermont Yankee

304 SS (Old Heaters) 304L SS (New Heaters)

CS (Old Heaters) 304 SS (New Heaters)

Chrome/Moly Hitachi 316LSS, electropolished. 304L & 316L, electropolished

3-17


Table 3-8 Condenser, Piping, Control Rod Blades, and Turbine Replacements

Replace Recirc. Piping

Replace RWCU Piping

Replace Extract.

Steam Piping

Replace Control

Rod Blades

Replace Turbine

Replace or Re-tube

Condenser Plant

Jan-91 (safe ends and risers)

Jan-91 (ring header, safe ends, risers)

Mar-93 (pins/rollers) Browns Ferry 2 Jan-91

Browns Ferry 3 Jan-95 Jan-95 Jan-95

Mar-91 Jan-85 Jan-83, Feb-87 Brunswick 1 Jan-83

Brunswick 2 Apr-84 Oct-89 Dec-85 Apr-84, Apr-88

Clinton Jan-85 Jan-87 Jan-88

Cofrentes Sep-00 Feb-02 Feb-02

Cooper 1984-1985 1987 Initial pipe

replacement in late 80s

Dresden 2 May-97

Dresden 3 Nov-85 May-97

Fermi 2 Apr-91 Oct-92 Apr-91, Nov-88 Mar-94

FitzPatrick Apr-94 1985 -

Hatch 1 Jun-90 Jan-90 Dec-96

Hatch 2 Dec-89 Aug-84 Jan-92 Dec-97

Hope Creek 1994 #3 Htr, 1995 #4 Htr

Limerick 1 Apr-00

Limerick 2 Apr-01

Monticello Dec-84 Dec-84 Dec-97

Mhleberg Aug-98 Aug-99

Nine Mile Point 1 1982-1983

Oyster Creek 1975 Apr-90 Oct-98 Apr-91, Nov-92

Peach Bottom 2 1991 1985

3-18


Table 3-8 (continued) Condenser, Piping, Control Rod Blades, and Turbine Replacements

Plant Replace or

Re-tube Condenser

Replace Recirc. Piping

Replace RWCU Piping

Replace Extract.

Steam Piping

Replace Control

Rod Blades

Replace Turbine

Peach Bottom 3 Dec-91 Dec-88

Perry Aug-92 1995

Pilgrim c. 1984 Jan-84 Jan-93 Jan-95 Jun-85 Jan-91

Quad Cities 1 Mar-04 (buckets)

River Bend Mar-92 May-92

Susquehanna 1 Jan-93 Dec-96 Jan-90 Mar-04

Susquehanna 2 Jan-93 Dec-97 1991 Mar-03

Vermont Yankee 1986 1986 1981

Table 3-9 System Flows and Reactor Liquid Mass Inventory

Plant Condensate Flow (lb/hr) Feedwater Flow

(lb/hr)

RWCU Flow (Normal/Max. % of

FW)

Reactor Liquid Mass Inventory

(lb at power)

Browns Ferry 2 1.41E+07 1.41E+07 0.9/0.9 527,000

Browns Ferry 3 1.41E+07 1.41E+07 0.9/0.9 527,000

Brunswick 1 7.91E+06 1.19E+07 1/1 470,000 - 480,000

Brunswick 2 7.31E+06 1.09E+07 1/1 470,000 - 480,000

Clinton 1.30E+07 1.30E+07 1/1 447,000

Cofrentes 1.01E+07 1.38E+07 0.92/1.11 448,124

Columbia 1.47E+07 1.47E+07 1/1 835,000

Cooper 9.52E+06 9.52E+06 1/1 420,000

Dresden 2 1.12E+07 1.12E+07 2.7/3.1 575,500

Dresden 3 1.12E+07 1.12E+07 2.7/3.1 575,500

Duane Arnold 7.89E+06 7.89E+06 1/1 251,000 (est).

Fermi 2 9.70E+06 1.52E+07 1/1.1 670,000

3-19


Table 3-9 (continued) System Flows and Reactor Liquid Mass Inventory

Plant Condensate Flow (lb/hr) Feedwater Flow

(lb/hr)

RWCU Flow (Normal/Max. % of

FW)

Reactor Liquid Mass Inventory

(lb at power)

FitzPatrick 1.08E+07 1.08E+07 1/1.19 471,000

Grand Gulf 1.07E+07 1.60E+07 1/1 970,000

Hatch 1 1.22E+07 1.15E+07 1/1 441,000

Hatch 2 1.30E+07 1.20E+07 1/1 440,000

Hope Creek 1.46E+07 1.46E+07 1/1 646,000

Laguna Verde 1 5.28E+06 8.25E+06 0.85

Laguna Verde 2 5.28E+06 8.25E+06 0.85

LaSalle 1 9.98E+06 1.43E+07 1/1 594,300

LaSalle 2 9.98E+06 1.43E+07 1/1 594,300

Leibstadt 9.80E+06 1.35E+07 1/

Limerick 1 1.47E+07 1.47E+07 1.1/1.1 550,000

Limerick 2 1.47E+07 1.47E+07 1.1/1.1 550,000

Monticello 7.28E+06 7.28E+06 1/1 425,000

Mhleberg 4.40E+06 4.40E+06 1.2/ 220,000

Nine Mile Point 1 7.30E+06 7.29E+06 2.74/5.14 502,000

Nine Mile Point 2 1.03E+07 1.49E+07 1.75/2 599,179

Oyster Creek 7.20E+06 7.20E+06 3/6 411,150

Peach Bottom 2 1.63E+07 1.63E+07 1/1.2 495,728

Peach Bottom 3 1.40E+07 1.40E+07 1.07/1.2 495,728

Perry 1.63E+07 1.63E+07 1/1 789,000

Pilgrim 7.95E+06 7.95E+06 1/1.5

Quad Cities 1 1.13E+07 1.13E+07 1.74/2 822,000

Quad Cities 2 1.13E+07 1.13E+07 1.74/2 822,000

River Bend 8.89E+06 1.24E+07 1/1 447,000

Susquehanna 1 1.46E+07 1.44E+07 1.03/1.03 646,000

Susquehanna 2 1.46E+07 1.44E+07 1.03/1.03 646,000

Vermont Yankee 6.43E+06 6.43E+06 1/1 390,000

3-20


Table 3-10 BWR Chemistry Regimes

BWR HWC Start Date Zn Inj.

Start DateZn

System NMCA NMCA Date Noble Metal

Loading on Fuel (g/cm2) (Note 4)

Browns Ferry 2 12/99 10/97 Passive Yes 3/01

Browns Ferry 3 8/00 12/95 Passive Yes 4/00 31.9

Brunswick 1 6/90 5/95 Passive No NA NA

Brunswick 2 1/89 3/96 Passive No NA NA

Clinton 6/02 12/00 Passive Yes 4/02

Cofrentes 3/97 7/96 Passive No 4/05* NA

Columbia 9/04 9/96 (1) Passive Yes 5/01

Cooper 1/03 12/99 Passive Yes 3/00 32.0

Dresden 2 4/83 12/96 Passive Yes 10/99, 10/03 32.5, 35

Dresden 3 3/99 7/98 Passive Yes 9/00

Duane Arnold 7/87 12/94 Passive Yes 10/96, 10/99 19.1, 30.4

Fermi 2 9/97 7/95 Passive No NA NA

FitzPatrick 8/88 1/89 Passive Yes 11/99, 9/04 23.5, 30.0

Grand Gulf 5/99 2/98 Passive No NA NA

Hatch 1 9/87 8/90 Passive Yes 3/99 52.6

Hatch 2 9/91 8/90 Passive Yes 3/00 50.6

Hope Creek 2/93 12/86 (2) Active No NA NA

Laguna Verde 1 4/05* 6/98 Passive No 10/05* NA

Laguna Verde 2 10/05* 8/98 Passive No 4/06* NA

LaSalle 1 8/99 7/94 Passive Yes 10/99 55.6

LaSalle 2 8/00 6/95 Passive Yes 11/00

Leibstadt 2/90 Passive No NA NA

Limerick 1 9/98 1992 Active Yes 3/00 25.3

Limerick 2 1/98 1991 Active Yes 4/01 26.7

Monticello 2/89 11/89 Active No NA NA

Mhleberg 11/00 8/98 Passive Yes 8/00 not known

Nine Mile Point 1 4/00 10/02 Passive Yes 5/00 41.8

Nine Mile Point 2 2/01 4/88 Passive Yes 9/00

3-21


Table 3-10 (continued) BWR Chemistry Regimes

BWR HWC Start Date Zn Inj.

Start DateZn

System NMCA NMCA Date Noble Metal

Loading on Fuel (g/cm2) (Note 4)

Oyster Creek 2/92 7/00 Passive Yes 10/02

Peach Bottom 2 5/97 6/91 Active Yes 10/98 61.5

Peach Bottom 3 3/97 6/92 Active Yes 10/99 32.2

Perry 8/02 2/90 Passive Yes 2/01

Pilgrim 9/91 12/96 Passive No NA NA

Quad Cities 1 10/90 9/98 Passive Yes 4/99 35.0

Quad Cities 2 10/90 6/97 Passive Yes 1/00 37.8

River Bend 12/01 6/97 (3) Passive No NA NA

Susquehanna 1 1/99 10/03 Passive No NA NA

Susquehanna 2 8/99 12/02 Passive No NA NA

Vermont Yankee 11/03 NA NA Yes 4/01

Table: 1. Discontinued for several months in 2001.

2. No zinc added cycle 6, 6/94 11/95.

3. Suspended 6/99 7/00.

4. Total quantity of noble metals added/fuel surface area.

*planned

NA is not applicable

3-22

4 POTENTIAL SOURCES AND IMPACT OF BWR CHEMICAL INPUTS

Objectionable Impurities Generation and Ingress

Corrosion Products of System Materials

Corrosion products are formed by corrosion processes at the surfaces of condensate, feedwater, steam, and reactor materials of construction. The corrosion products are present as impurities in the condensate, feedwater, and reactor coolant in ionic, colloidal, and insoluble oxide forms. The corrosion products are analyzed at the plant site as elemental metals, including iron, copper, nickel, zinc, chromium, and cobalt. Stations do not make determinations of the oxide forms collected from liquid samples. Iron occurs as the result of corrosion of carbon steel piping and components and represents the highest total mass of corrosion products generated. Copper and zinc are significant in plants with brass and other copper-alloy condenser tubes. Zinc is also an additive used at many plants for shutdown radiation dose control. Stainless steel piping and components are the sources of nickel and chromium. Cobalt is normally present in low mass concentrations (ppt levels) in condensate, feedwater, and reactor coolant, and is mainly of concern due to its activation in the reactor to produce 60Co, which deposits on piping surfaces and is responsible for the majority of the radiation exposure to plant personnel. The source of the cobalt is from the corrosion of structural materials (carbon steel, stainless steels, nickel-based alloys) that contain trace amounts of cobalt as an impurity and the wear of hard facing cobalt-based alloys, such as StelliteTM, that are used in turbines, in pumps and valves, and for the pins and rollers of older-design GE control blades. StelliteTM contains approximately 60% cobalt.

Typically, greater than 90% of the iron entering the reactor with the feedwater is deposited on the fuel surface. Under Normal Water Chemistry (NWC), BWRs operated for many cycles with >5 ppb feedwater iron without indications of crud-related fuel cladding corrosion failures. The crud deposited on the fuel tended to be mainly a fluffy hematite oxide with low resistance to heat transfer. Crud-induced localized corrosion (CILC) failures in the late 1970s and 1980s were attributed to localized heavy crud deposits rich in copper. This failure mechanism was mitigated by improvement of the nodular corrosion resistance of Zircaloy-2 cladding and by reducing feedwater copper concentrations through replacement of copper-alloy materials with a low-copper alternative or by improved copper removal from the condensate stream [1].

Operating and chemistry regime changes over the past several years have resulted in increased fuel duty and a different type of crud that deposits on the fuel surface. To improve cycle economics, power uprates have been implemented, fuel has been operated to a higher discharge burn-up, and operating cycles have been extended. Concurrently, more of the reactor chemistry

4-1

Potential Sources and Impact of BWR Chemical Inputs

environment has become increasingly reducing, evolving from hydrogen injection for recirculation piping protection (Hydrogen Water Chemistry or HWC), to moderate-HWC for internals protection, to Noble Metal Chemical Application with HWC (NMCA /HWC), under which the Electrochemical Corrosion Potential (ECP) reaches 450 to 500 mV (SHE) at wetted surfaces where the coolant hydrogen/oxidant (O2 + H2O2) molar ratio is >2. As the chemistry environment has become more reducing, there has been an increased emphasis on maintaining sufficient zinc injection to suppress shutdown radiation dose rates. The reducing environment and added zinc has changed the nature of the crud that deposits on the fuel.

Fuel crud deposits typically consist of a loosely adherent deposit overlaying over a more tenacious adherent deposit. Under NWC conditions the deposits were primarily red iron oxide, hematite. At plants with copper alloy condenser tubes this deposit could contain copper and zinc, depending on the type and efficiency of the condensate cleanup system. In some cases, incorporation of copper produced an insulating deposit that resulted in CILC, Crud Induced Localized Corrosion, of the fuel clad. The amount of adherent deposit increased with the introduction of zinc injection, without affecting fuel corrosion. Implementation of HWC typically produced a restructuring of metal oxide deposits in reducing regions as hematite (Fe2O3) was converted to magnetite (Fe3O4). The concentrations of soluble and particulate oxides in reactor water increased. Under conditions that are not yet understood, increased clad corrosion has recently occurred under fuel crud deposits at some units. Today, considerations such as higher discharge burn-up and higher local power peaking suggest that it is desirable to minimize the mass of crud deposited on the fuel. Consequently, to ensure fuel integrity, there is an intensified emphasis on controlling feedwater corrosion products, particularly iron and also copper for plants with a significant potential copper source (such as copper-alloy condenser tubes), and the input of zinc.

The highly reducing nature of portions of the BWR environment results in a combination of hematite (Fe2O3) and magnetite (Fe3O4) crud deposits on the fuel. The presence of metals such as zinc, nickel, chromium and cobalt promote the formation of spinel forms of the oxide. The formation of a tenacious oxide deposit is observed at the fuel cladding surface, beneath an outer fluffy hematite layer. Higher feedwater iron concentrations produce higher zinc demands to meet dose control goals, and increase the propensity for a thicker crud layer, which has been related to the occurrence of fuel crud spallation. Fuel crud spallation may be related to or a precursor of Zircaloy cladding corrosion.

Therefore, to enhance fuel reliability, minimizing feedwater corrosion products is recommended [2]. When feedwater iron is reduced, the quantity of zinc injected for radiation dose control can also be reduced.

Radiolysis Products

BWR operation results in the radiolytic decomposition of water by the gamma and neutron interaction with the water molecule as indicated by the following overall equilibrium reaction:

2H20 2H2 + O2

4-2


The reaction is shown as reversible since the hydrogen and oxygen species formed can also interact with the neutron and gamma flux to reform water molecules. Under steady state 100% power operating conditions without hydrogen injection (NWC), the equilibrium reactor coolant dissolved oxygen (DO) concentration in a typical BWR (in the liquid at the reactor recirculation system or the RWCU system sample point) is about 200 ppb, while the equilibrium dissolved hydrogen concentration is typically only a few ppb. Intermediate reactions in the radiolytic decomposition of water result in the production of hydrogen peroxide, a non-volatile, short-lived product that causes reactor water H2/O2 under NWC to be


As long as there is sufficient catalyst on the surface and the bulk water H2/O2 molar ratio is >2, the oxygen concentration on the surface will be minimal, and the corrosion potential will be


sulfuric acid (to lower the pH), organic scale inhibitors, or a combination of these. Corrosion inhibitors and dispersants may also be added in low concentrations. Some plants also add specialty chemicals for controlling macro-fouling (e.g., zebra mussels) in the main condenser tubes.

Chloride and sulfate concentrations that are representative of various types of circulating cooling water are shown in Table 4-1. For a given cooling water in-leakage rate, the rate of contaminant ingress various widely for the different cooling waters. For each cooling water type, the tolerable leak rate depends on the capability of the condensate polishing system to remove the ionic impurities from the condensate while maintaining acceptably low impurities in the condensate polisher effluent. Plants with deep bed condensate polishers have a much greater capacity to handle condenser leaks than plants with condensate filter demineralizers.

Condenser leaks can be generally classified as a small chronic leak, a significant leak, or a large leak. A small chronic leak, which may be too small to justify a power reduction to locate and plug, may have a measurable impact on the reactor water chemistry and result in higher operating costs due to the need to replace resins as the capacity is consumed. A significant leak has a measurable significant impact on chemistry and operating costs, but may be small enough (depending on condensate polishing design and cooling water source) that a planned power reduction to locate and plug the leak can be scheduled. A large leak is typically due to a condenser tube failure or a displaced tube plug and results in a high rate of ionic impurities ingress rate requiring timely (often rapid) response by the station to reduce power, isolate the water box with the leak and fix the leak (typically by plugging the leaking tubes).

Table 4-1 Typical Main Condenser Cooling Water Chloride and Sulfate Concentrations

Circulating Cooling Water Type Typical Cooling Water Chloride (mg/L) Typical Cooling Water

Sulfate (mg/L)

River, Once-through (low solids) 9.6 16.6

Lake, Once-through 30.3 30.1

Lake, 4.5 cycles of concentration 140 356

Saltwater 14,000 1,960

Condenser Air In-leakage

Air in-leakage into the main condenser occurs when the condenser is at vacuum and can be detected by increased condensate dissolved oxygen measurement and by increased offgas flow. The predominant effect depends on the location of the leak. The main elements contained in atmospheric air are nitrogen (approximately 79%) and oxygen (approximately 21%). In relation to fuel issues, air in-leakage could affect corrosion products transport if feedwater dissolved oxygen becomes too high. Air also contains trace impurities, such as carbon dioxide, which dissolves in water and has a measurable effect on condensate conductivity. When carbon dioxide dissolves in water, it is present as carbonic acid (H2CO3), which dissociates to form bicarbonate and carbonate ions and lowers the pH of demineralized water.

4-5


Above water level leaks are the most common because a typical condenser has 100 or more process connections, most of which are located above the normal water level. The magnitude of condenser air in-leakage can be estimated by the total offgas flow measurement downstream of the offgas recombiner system. Under normal water chemistry conditions (NWC), the radiolytic hydrogen and oxygen gas concentrations in the main steam are produced in stoichiometric quantities and, assuming full recombination in the offgas recombiner, the volumetric gas leaving the recombiner is essentially equal to air in-leakage into the main condenser. Therefore, the recombiner effluent normally contains nitrogen and oxygen at the nominal air volume concentrations of 79% and 21%, resp

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