thermal fatigue monitoring guidelines

Thermal Fatigue Monitoring Guidelines(MRP-32)

Technical Report

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EPRI Project ManagerJ. Carey

EPRI • 3412 Hillview Avenue, Palo Alto, California 94304 • PO Box 10412, Palo Alto, California 94303 • USA800.313.3774 • 650.855.2121 • [email protected] • www.epri.com

Thermal Fatigue MonitoringGuidelines (MRP-32)1001016

Final Report, April 2001

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NOTICE: This report contains proprietary information that is theintellectual property of the MRP utility members and EPRI.Accordingly, it is available only under license from EPRI and maynot be reproduced or disclosed, wholly or in part, by anyLicensee to any other person or organization.

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Framatome Technologies

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CITATIONS

This report was prepared by

Framatome Technologies3315 Old Forest RoadLynchburg, VA 24506

AuthorsB. L. BomanR. W. MooreR. R. Schemmel

Prepared for:Materials Reliability Project Thermal Fatigue Issue Task Group and EPRI

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

Thermal Fatigue Monitoring Guidelines (MRP-32), EPRI, Palo Alto, CA: 2001. 1001016.

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REPORT SUMMARY

The Materials Reliability Project (MRP), formed in January 1999, is an association of utilities focusing on pressurized water reactor (PWR) vessel, material, and related issues. The Thermal Fatigue Issue Task Group (MRP TF-ITG) was formed in mid-1999 to evaluate potential effects of thermal fatigue on normally stagnant piping systems attached to reactor coolant system piping. This TF-ITG report provides thermal fatigue monitoring guidelines for attached piping systems where there may be high potential for thermal fatigue cracking.

Background In 1998, the Nuclear Regulatory Commission expressed concerns that surface examinations of small diameter (< 4-inch NPS) high-pressure safety injection piping required by American Society of Mechanical Engineers (ASME) Section XI were not adequate and that volumetric examination should be considered. This led to formation of the MRP Thermal Fatigue program to provide evaluation and assessment techniques for managing potential thermal fatigue in attached piping systems.

Objective To assist utility engineers in defining an effective thermal fatigue monitoring program that determines whether significant thermal stratification and/or cycling is occurring in normally stagnant piping systems attached to the reactor coolant system (RCS).

Approach The research team used industry thermal fatigue monitoring experiences and current understanding of thermal stratification phenomena to develop the thermal fatigue monitoring guidance described in the report. Team members compared competing monitoring technologies and provided recommendations.

Results External thermocouples are recommended as the general thermal fatigue monitoring method for detecting cyclic thermal stratification caused by in-leakage or turbulent penetration. The report presents monitoring locations for both detecting thermal stratification and for obtaining data required for detailed structural evaluations. In addition, pressure, leakage, and displacement monitoring are discussed.

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EPRI Perspective These thermal fatigue monitoring guidelines provide utilities with a reference for establishing an effective monitoring program to determine the potential for unanticipated cyclic thermal stratification. Using these guidelines can contribute to an effective thermal fatigue management program and assist in avoiding unplanned outages due to thermal fatigue cracking.

Keywords Fatigue Thermal fatigue Thermal stratification Monitoring Reactor coolant piping Cracking Leakage

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ACKNOWLEDGEMENTS

The contributions made by the members of the MRP TF-ITG and other persons affiliated withthe project, listed below, are gratefully acknowledged for their efforts which led to the successfulcompletion of this document:

MRP TF-ITG Utility Members:

Mike Robinson – Chairman

Mike Belford

Jeff Brown

Mike Davis

Guy DeBoo

Maurice Dingler

Glenn Gardner

Charles Griffin

Daniel Jopling

Richard Lutz

Larry Rinaca

Sherman Shaw

Les Spain

Raymond To

Others:

Kurt Cozens

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EXECUTIVE SUMMARY

This MRP Thermal Fatigue report provides thermal fatigue monitoring guidelines for normallystagnant piping systems attached to reactor coolant piping where there may be high potential forthermal fatigue cracking.

The thermal fatigue monitoring process is defined for detecting the presence or absence of cyclicthermal stratification or for obtaining the required data for detailed structural evaluations of lineswhere cyclic thermal stratification occurs. For each of the process steps, guidance is providedsuch that the utility engineer can implement an effective thermal fatigue monitoring program.External thermocouples are recommended as the general means for detecting cyclic thermalstratification recognizing that adjustments to the measured data may be required to account forthe temperature cycle attenuation through the pipe wall. Other temperature sensor methods andsensor types are discussed for their applicability to the problem.

Temperature sensor locations are provided for a number of attached piping configurationsbelieved to encompass the variability in PWR power plant system piping designs. Theselocations are classified in two broad categories: (1) sensor locations required to detect thepresence or absence of cyclic thermal stratification, and (2) sensor locations required for detailedstress and fatigue evaluations of these cyclic conditions.

Data acquisition and transmission considerations are also discussed and the results of amonitoring survey are presented.

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CONTENTS

1 INTRODUCTION.................................................................................................................. 1-1

2 BACKGROUND................................................................................................................... 2 -1

3 IMPLEMENTING A THERMAL FATIGUE MONITORING PROGRAM ................................ 3-1

3.1 Thermal Fatigue Monitoring Process......................................................................... 3-2

3.2 Thermal Fatigue Monitoring Process Steps............................................................... 3-2

3.2.1 Define the Thermal Fatigue Monitoring Program Objective .............................. 3-2

3.2.2 Determine the Sensors to be Used .................................................................. 3-4

3.2.3 Determine Sensor Locations............................................................................ 3-4

3.2.4 Define Sampling Rate Requirements ............................................................... 3-6

3.2.5 Develop Software/Hardware Specification ....................................................... 3-7

3.2.6 Procure, Install, Configure Software/Hardware ................................................ 3-7

3.2.7 Collect Data ..................................................................................................... 3-7

3.2.8 Evaluate Data .................................................................................................. 3-8

3.2.9 Determine if Monitoring can be Discontinued ................................................... 3-8

3.2.10 If Stress Evaluation Required, are the Data Sufficient? .................................... 3-9

3.2.11 Re-configure .................................................................................................... 3-9

4 TYPES OF SENSORS FOR MONITORING......................................................................... 4-1

5 MONITORING LOCATIONS................................................................................................ 5-1

6 DATA ACQUISITION AND TRANSMISSION...................................................................... 6-1

6.1 Data Acquisition ........................................................................................................ 6-3

6.2 Data Transmission .................................................................................................... 6-3

6.3 Smart-Front-End versus Raw Data Acquisition.......................................................... 6-4

6.4 In-Containment Installation........................................................................................ 6-5

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7 MONITORING EXPERIENCE SURVEY .............................................................................. 7-1

8 ACRONYMS........................................................................................................................ 8-1

9 REFERENCES .................................................................................................................... 9-1

A TEMPERATURE MEASUREMENT.....................................................................................A-1

A.1 Resistance Temperature Detectors and Thermocouples...........................................A-1

A.1.1 Temperature Range .............................................................................................A-1

A.1.2 Response Time and Monitoring Frequency ..........................................................A-1

A.1.3 Temperature Measurement Accuracy...................................................................A-2

A.1.4 Installation ............................................................................................................A-5

A.2 Resistance Temperature Detectors (RTDs)...............................................................A-6

A.3 Thermocouples .........................................................................................................A-6

A.3.1 Thermocouple Types............................................................................................A-6

A.3.2 T/C Measurement Uncertainty Discussion ............................................................A-7

A.3.3 Special Fabrication Methods.................................................................................A-8

A.3.4 Insulation ..............................................................................................................A-8

B DISPLACEMENT METHOD INSTALLATION AND COST COMPARISON ........................B-1

B.1 Displacement Sensor Types......................................................................................B-1

B.2 Measurement Accuracy Comparison.........................................................................B-2

B.3 Installation.................................................................................................................B-3

C THERMAL FATIGUE MONITORING SURVEY SUMMARY................................................C-1

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LIST OF FIGURES

Figure 3-1 Thermal Fatigue Monitoring Process.................................................................... 3-10

Figure 4-1 Inside and Outside Pipe Surface Temperature Variations - Illustrating TypicalAttenuation Through Pipe Wall ........................................................................................ 4-4

Figure 4-2 Attenuation of Through-Wall Temperature Oscillations with Cyclic Period.............. 4-5

Figure 5-1 (a) and (b) Thermocouple Placement Upward-to-Horizontal-to-ValveConfiguration Inflow/In-leakage ....................................................................................... 5-4

Figure 5-1 (c) and (d) Thermocouple Placement Upward-to-Horizontal-to-ValveConfiguration Outflow/Out-leakage.................................................................................. 5-5

Figure 5-2 (a) and (b) Thermocouple Placement RCS-to-Horizontal-to Up (or Inclined)-to-Horizontal-to-Valve Configuration Inflow/In-leakage .................................................... 5-6

Figure 5-2 (c) and (d) Thermocouple Placement RCS-to-Horizontal-to-Up (or Inclined)-to-Horizontal-to-Valve Configuration Outflow/Out-leakage............................................... 5-7

Figure 5-3 (a) and (b) Thermocouple Placement RCS-to-Horizontal-to-ValveConfiguration Inflow/In-leakage ....................................................................................... 5-8

Figure 5-3 (c) and (d) Thermocouple Placement RCS-to-Horizontal-to-ValveConfiguration Outflow/Out-leakage.................................................................................. 5-9

Figure 5-4 (a) and (b) Thermocouple Placement RCS-to-Horizontal-to-Down (orInclined)-to-Horizontal-to-Valve Configuration Inflow/In-leakage.................................... 5-10

Figure 5-4 (c) and (d) Thermocouple Placement RCS-to-Horizontal-to-Down (orInclined)-to-Horizontal-to-Valve Configuration Outflow/Out-leakage .............................. 5-11

Figure 5-4 (e) and (f) Thermocouple Placement RCS-to-Horizontal-to-Down (orInclined)-to-Horizontal-to-Valve Configuration No Leakage (Turbulent Penetration) ...... 5-12

Figure 5-5 (a) and (b) Thermocouple Placement RCS-to-Down (or Inclined)-to-Horizontal-to-Valve Configuration Inflow/In-leakage ...................................................... 5-13

Figure 5-5 (c) and (d) Thermocouple Placement RCS-to-Down (or Inclined)-to-Horizontal-to-Valve Configuration Outflow/Out-leakage................................................. 5-14

Figure 5-5 (e) and (f) Thermocouple Placement RCS-to-Down (or Inclined)-to-Horizontal-to-Valve Configuration No Leakage (Turbulent Penetration)......................... 5-15

Figure 5-6 (a) and (b) Thermocouple Placement Outboard of First Valve – Through HotTrap Inflow/In-leakage ................................................................................................... 5-16

Figure 5-6 (c) and (d) Thermocouple Placement Outboard of First Valve – Through HotTrap Outflow/Out-leakage ............................................................................................. 5-17

Figure 5-7 (a) and (b) Thermocouple Placement Outboard of First Valve – Through ColdTrap Inflow/In-leakage ................................................................................................... 5-18

Figure 5-7 (c) and (d) Thermocouple Placement Outboard of First Valve – Through ColdTrap Outflow/Out-leakage ............................................................................................. 5-19

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Figure 6-1 Illustration of Recommended System Configuration.............................................. 6-2

Figure A-1 Recommended Temperature Sensor Installation Method ..................................A-10

Figure A-2 T/C Temperature Measurement Principles ........................................................A-11

Figure B-1 PT Installation Requirements.............................................................................B-3

Figure B-2 LVDT Signal Conditioning Requirements.............................................................B-5

Figure B-3 LVDT Data & Supply Voltage Installation Requirements.....................................B-5

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LIST OF TABLES

Table 3-1 Minimum Required Temperature Measurement Locations ..................................... 3-5

Table 5-1 Key for Thermocouple Placement Figures............................................................... 5-2

Table 5-2 T/C Placement Around Circumference of Pipe (for C-C designation) ...................... 5-3

Table A-1a Temperature Measurement Sensor Accuracies For Thermocouples andRTDs...............................................................................................................................A-3

Table A-1b Temperature Measurement Sensor Accuracies For Thermocouples andRTDs...............................................................................................................................A-4

Table A-1c Thermocouple Measurement Sensor Accuracies ................................................A-5

Table A-2 Characteristics of Tefzel (280), a Fluoropolymer Resin.........................................A-9

Table C-1 Plant Survey Summary .........................................................................................C-2



1-1

1 INTRODUCTION

This guideline presents plant-monitoring recommendations to support engineering evaluations ofthermal fatigue in normally stagnant, unisolable piping systems attached to the main reactorcoolant system (RCS) piping in Pressurized Water Reactor (PWR) power plants. Some of thepiping covered by this guideline was previously identified as being susceptible to thermal fatiguewith the issuance of NRC Bulletin 88-08 and its supplements.

These guidelines are provided for implementing means to detect and monitor the occurrence ofthe fluid conditions having the potential for inducing significant cyclic thermal stresses in RCSattached piping. As such, they include approaches to configuring and operating various types ofmonitoring and data handling systems for these purposes.

Section 3 provides an overview of the steps involved in developing a monitoring program tosupport evaluations of thermal fatigue in piping connected to the RCS. Included is a discussionof factors to be considered when setting up a program for monitoring plant piping for thermalcycling.

Section 4 addresses the measuring devices for use in monitoring the parameters of fluidtemperatures and pressures, and piping deflections. Section 5 provides guidelines for placementof sensors for temperature monitoring. Section 6 addresses data collection and transmission.

Section 7 summarizes results of a survey of thermal fatigue monitoring experience at operatingplants.

A list of acronyms used in this report is provided in Section 8.

Appendix A provides details related to temperature measurements and Appendix B addressesmethods of displacement sensor installation. Appendix C presents results of a limited thermalfatigue monitoring survey summary conducted in connection with the development of thesethermal fatigue monitoring guidelines.

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2 BACKGROUND

Cracking in piping attached to the reactor coolant system has, in some cases, been attributed tounanticipated cyclic thermal stratification. To assist utility personnel in assessing the potentialfor cyclic thermal stratification to occur in their plant, guidance for developing an effectivethermal fatigue monitoring program was needed.

Thermal fatigue monitoring is but one means of assessing the potential for cyclic thermalstratification in attached piping system. The reader is advised to review EPRI’s Thermal FatigueManagement Guidelines (currently in preparation) for additional information.

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3 IMPLEMENTING A THERMAL FATIGUE MONITORINGPROGRAM

This section provides guidelines for implementing a thermal fatigue monitoring program forpiping systems attached to the RCS. The steps in the monitoring process are presented anddiscussed. Some of the steps are easily described and understood while others warrant a detaileddiscussion. For the latter, an overview is presented in this section and a more detailed discussionis presented in a separate section of the report (e.g., types of sensors for monitoring, andlocations for temperature monitoring).

The occurrence of leakage from normally stagnant piping in operating PWRs and experience inthermal fatigue monitoring of piping indicate that cyclic thermal stratification has the potentialfor causing significant fatigue damage in RCS attached piping. Leakage has occurred in makeupand safety injection piping, residual heat removal (RHR), excess letdown, and RCS drain piping[1]. Plant measurements have demonstrated that very significant temperature gradients mayexist in these piping systems due to thermally stratified flows. Because of the large potentialtemperature differences between the RCS and attached piping, it can reasonably be assumed thatappreciable thermal loading of attached piping will occur over at least some fraction of the plantoperating lifetime. Whether the thermal loading is significant depends on the magnitude of thetemperature differences and the number of occurrences, i.e., cycles. For example, if an attachedline experiences a quasi-steady thermal stratification during hot operation that dissipates duringplant cooldown, it is likely that the fatigue damage can be shown acceptable given the relativelylimited number of heatups and cooldowns. If, however, thermal fatigue monitoring showedcyclic thermal stratification to be occurring more frequently than once per heatup and cooldown,then data would be required for a structural evaluation to determine if the associated fatiguedamage is acceptable considering the observed frequency and the expected plant operatinglifetime.

Generally, all piping connecting with the RCS should be considered potential candidates forthermal fatigue and reviewed to determine the need for thermal fatigue monitoring (see EPRI’sthermal fatigue management guidelines), including the following:

• Safety injection

• Charging / makeup

• RCS drain lines

• Normal letdown

• Alternate letdown

• RHR/CF injection

• RHR / Shutdown Cooling (SDC) / Decay Heat Removal (DHR) letdown

Implementing a Thermal Fatigue Monitoring Program

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Not all normally stagnant attached piping systems are expected to require monitoring (seeSection 3.1 for monitoring criteria) but all of the above should be considered. Pressurizer surge,spray, and auxiliary spray lines are also potential candidates for thermal fatigue monitoring.While these lines are not included within the scope of this report, discussions on monitoringtypes, data collection, and data transmission are applicable to these lines.

3.1 Thermal Fatigue Monitoring Process

An overview of the thermal fatigue monitoring process is presented in Figure 3-1. Once therequirement for thermal fatigue monitoring has been established, the steps shown in this figurecan be followed to implement a successful monitoring program. In general, the requirement forthermal fatigue monitoring can arise as a consequence of one or more of the following:

• An attached line has the potential for cold in-leakage from a high pressure source through asingle, normally-closed isolation valve.

• An attached line has the potential for cyclic thermal stratification due to its downwardorientation and ambient heat losses.

• Pipe cracking or leaks occur (or have occurred) in unisolable RCS attached piping at theparticular plant under consideration or in similar piping configurations at other plants.

• Additional data is required to show the structural evaluation of an attached line to beacceptable for the component’s design life.

3.2 Thermal Fatigue Monitoring Process Steps

A discussion of the individual monitoring steps follows.

3.2.1 Define the Thermal Fatigue Monitoring Program Objective

Definition of the monitoring program objective is the key step in the process. The monitoringprogram objective directly affects the selection of a) the parameter to be monitored, b) the viablesensor types, c) monitoring frequency, d) monitoring locations, e) choice of monitoring systemhardware and software, and f) the recommended action levels.

The monitoring program objective is closely tied to the phenomena of interest. Plant pipingleaks (see Reference 1 for more details) that have been attributed to thermal fatigue have beencaused by:

• The cyclic interaction of cold in-leakage from a high pressure injection system with turbulentpenetration from the RCS. This has been described within the industry as a “Farley-Tihange” type piping leakage event due to its occurrence at those plants. It has only occurredon lines that rise vertically from the RCS and then turn horizontal to a check valve and forwhich in-leakage has occurred. This configuration is designated “UHV” for upward-horizontal-valve.


3-3

• The cyclic turbulent penetration into attached lines that fall vertically from the RCS followedby a horizontal section in which the ambient heat losses are sufficient to provide a coldsource of water to intermittently mix with the hot water conveyed from the RCS. This typeof piping failure has occurred in the TMI-1 and ONS-1 cold leg drain lines and in Mihama’sexcess letdown line. This configuration is designated “DHV” for downward-horizontal-valve.

• The cyclic thermal mixing between hot RCS water and cold makeup water that has occurredin B&W makeup lines due to thermal sleeve loosening. Because the thermal sleeve redesignhas precluded additional failures, this application was not included in the scope of the EPRIthermal fatigue management project.

• Cyclic thermal stratification due to hot RCS out-leakage through the packing of an isolationvalve. This event, which occurred at the Genkai plant, is believed to be unique and highlyunlikely to re-occur. Thus, it has not been emphasized by the EPRI Thermal Fatigue Issuestask group. The monitoring guidance presented herein does allow for the possibility of cyclicthermal stratification due to out-leakage and monitoring locations to detect out-leakage areincluded herein.

The specific objectives of monitoring include:

• Determining whether or not significant in-leakage into the RCS is occurring.

• Determining whether or not turbulent penetration is causing significant cyclic thermalstratification to occur.

• Determining whether or not significant out-leakage from the RCS is occurring.

• Obtaining sufficient data to perform a detailed stress evaluation should cyclic thermalstratification occur due to in-leakage, turbulent penetration, or out-leakage.

In general, the extent of monitoring coverage, i.e., number of sensors, necessary to support astructural evaluation for a particular section of piping is greater than that required simply todetermine whether leakage flow or thermal cycling occurs. This is because any deficiencies inthe data intended for use in a structural evaluation require conservative, bounding assumptionswhere data are lacking, reducing the chances of demonstrating acceptable results.

For piping configurations known to be susceptible to thermal cycling, the monitoring objectiveshould be to confirm the conservatism of the prediction of the potential phenomena or to obtainsufficient thermal loading information to be able to analyze the piping in sufficient detail topredict with confidence that undetected cracking will not occur over the service lifetime of thepiping. In certain cases, it may not be possible to show by analysis that cracking will not occurunless the available monitoring data is adequate to thoroughly characterize the thermalconditions.

Monitoring goals should also include the gathering of sufficient information to justify changingplant operating conditions or making equipment changes to the affected system. Oncemodifications are made, monitoring should continue for a time sufficient to demonstrate theeffects of the changes.


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3.2.2 Determine the Sensors to be Used

Thermal fatigue due to cyclic thermal stratification is caused by time-varying changes in theinside water temperature. It is not practical to directly measure the inside fluid or inner pipe walltemperatures. Thus, indirect measurements are relied upon.

Candidate measurements for monitoring include the following: external pipe wall temperatures,flow rate, fluid pressure, piping displacements, and strain gage data. The selection of themeasurement(s) to be made is governed by the particular thermal fatigue monitoring objective.

If detection of in-leakage or out-leakage is the desired objective, then the use of external pipingtemperature and/or fluid pressure measurements may be appropriate. Pressure measurementsmay be used to indicate the potential for leakage, but cannot be used to determine whether theleakage flow is significant.

Valve leakage rates have also been measured directly and monitored at scheduled times with thereactor at hot conditions. Monitoring leakage rates directly would be important if the leakageflow is routed to the RCS for normal valve lineups.

For determining whether turbulent penetration thermal cycling is occurring, external temperaturemeasurements are recommended.

Thus, the recommended and most widely-used measurement is the external temperaturemeasurement. Of the potential sensors (thermocouples, RTDs, and thermography), externallymounted thermocouples provide the best combination of accuracy, affordability, and reliabilityfor measuring pipe wall temperature.

However, external temperature measurements have their limitations in applications where rapidcycling or short spikes in fluid temperature occur. If the objective is to obtain sufficient data toperform a detailed structural evaluation (e.g., if a certain degree of thermal cycling is beingjustified for continued operation), then external measurements alone may not provide adequatedetail to properly characterize the thermal cycling occurring on the inner pipe wall. Methods topredict inner wall temperatures from external measurements, such as described in References 2or 3, need to be employed. In addition, the use of piping displacements and/or strain gage datacan provide supplementary information for use in stress calculations, but are not required in mostcases.

Sensor types are discussed further in Section 4 with additional details in Appendix A.

3.2.3 Determine Sensor Locations

Pressure measurements to accurately indicate the potential for in-leakage may require installing apressure tap upstream of the first isolation valve outboard of the RCS. Differential pressuremeasurements across the isolation valve generally will require installation of taps upstream anddownstream of the valve. However, installing pressure taps in the piping specifically formonitoring purposes is not considered practical.


3-5

Piping displacement measurements, when advisable, should be made at mid-span between pipingsupports. Strain gages (optional) should be placed at the top and bottom of the piping at thesupports, within or adjacent to sections of piping subjected to thermal stratification. The pipingdisplacement and strain measurements may be useful for steady-state calibration of the structuralmodel and input data for time-averaged temperature distributions in the piping. Successfullycorrelating displacements with analytical predictions relies upon all the information for bothdisplacements and temperatures at corresponding times being communicated correctly to themodeler.

In the case of temperature measurement, sensor placement is dependent on the particularphenomenon and the physical layout of the section of piping of concern.

To meet the specific objectives listed previously in Section 3.2.1, minimal sets of pipingtemperature measurements are required as shown in Table 3-1 (for detailed recommendationsrefer to Section 5).

Table 3-1Minimum Required Temperature Measurement Locations

Objective Minimum Required Temperature Measurement Locations

Detect significantin-leakage.

Top and bottom of pipe immediately inboard of isolation valve.

Quantify thethermal cyclingcaused byturbulentpenetration .

In downward-running lines to a horizontal section, one measurement in thevertical section immediately above the elbow or bend to the horizontalsection. Two additional measurements at top and bottom of the horizontalpiping at the elbow or bend if the elbow/bend is located at 5 to 25 diametersfrom RCS (but not beyond the first closed valve).

Detect significantout-leakage.

Top and bottom of pipe immediately outboard of isolation valve.

Provide data forstress and fatigueevaluations.

Top and bottom of pipe for all sections subjected to significant thermalstratification and/or turbulent penetration at several axial locations for eachhorizontal section of piping, see Section 5.

Two assumptions regarding thermal cycling phenomena based on current understanding andplant operating experience are:

• In upward configurations without in-leakage or out-leakage, the thermal stratification thatoccurs will be such that it will not result in failure. This is based on observations from plantdata and thermal-hydraulic understandings that a near steady, relatively mild top-to-bottomtemperature difference (< 70°F) will develop during each plant heatup and dissipate duringthe plant cooldown and that the number of heatup/cooldown thermal cycles are such thatfailure will not occur (i.e., failures occur due to 105 to 107 cycles and not for 102 cycles).

• In downward configurations where the turbulent penetration does not reach the horizontal(i.e., cycling occurs exclusively in the vertical piping), the cycling as a result of thepenetration depth variation does not produce sufficient gradients in the pipe to cause


3-6

throughwall cracking. It is believed that pipe wall conduction will preclude formation ofsharp temperature gradients.

If these assumptions are proven false (by analysis or measured data), then the monitoringguidelines will need to be modified so that these locations are properly taken into account.

3.2.4 Define Sampling Rate Requirements

Required data sampling rates in terms of measurements per unit time will vary with the type ofparameter to be measured and the particular phenomenon of concern (i.e., monitoring objective).The inverse of sampling rate is sampling interval, or time between successive samples.

If detection of in-leakage or out-leakage is the desired objective, then sampling should becontinuous during dynamic plant conditions such as heatup, and on a periodic basis such asweekly for steady state conditions. The periodic basis depends on valve characteristics andoperating loads. If a valve is normally closed and isolated from temperature changes and waterhammer effects, the steady state monitoring may be greatly reduced. It is also noted that valveseat conditions can change due to open/close cycles, so that a conclusion that a valve does notleak past its seat in the short term is difficult to project to the end of plant life.

Sampling rates, using external thermocouples or pressure monitors, can be as low as one perminute for detection of in-leakage or out-leakage. However, as discussed in Section 3.2.8, dataonly needs to be reviewed periodically to demonstrate that leakage has not developed.

If the objective is to detect cyclic thermal stratification, the sampling should be performed for atleast one fuel cycle. Sampling rates need to be relatively high to capture the fluid temperaturefluctuations. Fluid temperatures in piping subjected to turbulent penetration may oscillate withperiods as short as a few seconds. However, the corresponding amplitude of wall temperaturevariations generally is much reduced relative to the fluid at these frequencies. The pipe wallthickness is the limiting factor on the time response for externally mounted sensors and can maskvariations with periods of less than 10 seconds for ½ inch thick stainless steel material.Consequently, the limits on the time response of the signal, and therefore on the requiredsampling rate with externally mounted temperature sensors, is determined by the method ofmounting and pipe wall thickness and not the time response of the sensors. In general, the fastestsampling time required will not be any faster than 2 to 5 seconds.

If the objective is to obtain data for a structural evaluation, data needs to be obtained duringheatups, power operation, and cooldowns. Since turbulent penetration is dependent on RCSflow, data should be collected during the changes in RC pump status that occur during heatupsand cooldowns. Sampling rates need be only fast enough to capture the short duration pulses.

To capture temperature data that does not involve rapid cyclic variations or short pulses, such asquasi-steady thermal stratification, sampling intervals can be as long as one minute.

Sampling intervals for other than temperature data, such as plant or system operating parameters,are not critical and generally can be as long or longer than one minute.


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3.2.5 Develop Software/Hardware Specification

For all but the simplest of plant monitoring systems, development of an equipment specificationis recommended to document the system requirements and provide the bases for design andprocurement. Requirements should address the following:

• Objectives

• Measurement locations, number of sensors, and sensor types

• Environmental conditions for sensor and candidate data acquisition locations

• Sensor placements

• Data acquisition hardware location and mounting method

• Sensor mounting method and signal transmission

• Data range (absolute and differential) requirements

• Data dynamic character requirements

• Accuracy, resolution, repeatability requirements

• Duration for data acquisition

• Alarms and event identification

• On-line display requirements

• Accessibility to data (reporting) needs

• Data storage, file maintenance, and retrieval

3.2.6 Procure, Install, Configure Software/Hardware

Details regarding the procurement and installation of the sensors and data acquisition system areprovided in Sections 4 and 6 along with Appendices A through C.

3.2.7 Collect Data

Data collection for purposes of monitoring for thermal fatigue should be scheduled to cover plantoperation over at least one complete fuel cycle such that all aspects of operation are covered (i.e.,monitoring should be performed during plant heatup, power ascension, full power operation,reactor shutdown, and plant cooldown). In general, monitoring data collected during normaloperating conditions are of interest. Data collected during upset conditions are of lesser valuesince the cumulative times and numbers of thermal cycles for these conditions would be smallrelative to the totals for normal operation.

Data acquisition systems can be set up to automatically archive monitoring data based on anynumber or kinds of triggering events. This can minimize the need for human attention andintervention as well as make efficient use of data storage devices over the 12 to 24 monthduration of the operating cycle.


3-8

3.2.8 Evaluate Data

Monitoring data must be evaluated to determine the course of action to be followed, whether toterminate monitoring or perform a stress and fatigue evaluation for the particular piping sectionof concern.

If temperature data are obtained using externally mounted temperature sensors, the raw data mustbe processed to extract estimates for the magnitudes and cycle counts of temperature variationsat the inner surface of the pipe wall. References 2 and 3 provide examples of such methods toconvert these data.

Plant monitoring data should be examined periodically to determine if mitigating steps areindicated to prevent excessive fatigue damage accumulation. Engineering actions may include,for example, requesting modification of operating procedures or plant parameters, orrecommending corrective maintenance of leaking valve seats. Technical specificationrequirements regarding integrity of pressure boundaries must of course be satisfied. Ideally, themonitoring system would be programmed to alert/alarm the existence of any condition likely torequire action by plant engineering.

If the objective of monitoring is to detect leakage, and given that leakage induced cracks havedeveloped quickly (one fuel cycle in a French plant), data should be reviewed at least once ortwice within a fuel cycle, depending on operational practices that could affect the leakage of thevalves, for example after each major plant evolution (heatup, power ascension, steady-statepower operation, cooldown, etc.). Again, a system that alerted the user whenever the actionlevels are exceeded would be ideal.

If the objective is to detect cyclic turbulent penetration, as into a drain line, the evaluation needbe done only once if the conditions sampled are bounding of plant conditions. Further discussionof the sufficiency in this case is given in Section 3.2.9.

3.2.9 Determine if Monitoring can be Discontinued

Once monitoring of a particular section of piping is initiated, termination would be justifiedunder the following circumstances:

• The piping section passes the screening criteria (currently under development).

• Use of monitoring data input to a structural evaluation shows acceptable fatigue results.

• Modifications made to plant procedures or equipment eliminates or decreases thermalcycling and reduces fatigue usage to acceptable levels as determined by post modificationmonitoring data input to the screening criteria and/or a structural evaluation.

Confidence in the decision to terminate monitoring is directly related to the adequacy, i.e.,extent, of the available amount of data used in the structural evaluation and the margins exhibitedby the analytical results.


3-9

If the original objective is to reduce uncertainty regarding cyclic behavior in an engineeringevaluation that considers a set of conditions concluded to bound those for the remaining plantlife, then a fixed period of monitoring is adequate for the purpose and the monitoring may beremoved at its completion. An example is drain line turbulence penetration where currentconditions would be expected to be essentially unchanging for the remaining plant life.

If the objective of monitoring is to detect cyclic behavior as would be caused by in-leakage, noguidance on terminating monitoring is provided since alternate provisions to assure lack ofunacceptable leakage are highly plant specific. As stated in section 3.2.4, it is noted that valveseat conditions can change due to open/close cycles, so that a conclusion that a valve does notleak past its seat in the short term is difficult to project to the end of plant life.

3.2.10 If Stress Evaluation Required, are the Data Sufficient?

Once monitoring data are available, a stress and fatigue evaluation may be required using themonitoring data for the specific piping section of concern. If the need to perform a stressanalysis is indicated based on minimal sets of temperature measurements for a section of piping,additional measurement points may be required depending on the magnitude of the temperaturedifferences. As an example, in a worst case scenario, the top-to-bottom temperature differencesconceivably could approach 400F for in-leakage to the RCS. A quick evaluation for this value ofstratification temperature difference and cyclic temperature range caused by turbulentpenetration would likely show that more detailed data would be required to show acceptablestress and fatigue results. Additional data would likely be required in this case includingmeasurements of top-and-bottom temperatures at a number of axial locations along the pipe.

3.2.11 Re-configure

A need to re-configure the monitoring of a specific section of piping will generally entail theaddition of temperature sensors. In the case of in-leakage, additional top-and-bottom of pipemeasurements along the pipe axis might be needed to define the axial temperature distributionsand the axial extent of piping subjected to cyclic temperatures. (Section 5 classifies sensorlocations into two categories: minimum coverage for cyclic thermal stratification detection, andmaximum coverage for detailed structural evaluation.)


3-10

MonitoringRequirementDefined

DefineMonitoringObjectives

DetermineSensorsTo Be Used

DetermineSensorLocations

DefineSamplingRates

Procure,Install,Configure

DataSufficient

?

DevelopSoftware/Hardware

Specification

Re-configure

EvaluateData

Collect Data

Cont inueMonitoring

DiscontinueMonitoring

Cycl ic TPObjective

DataObjective

Is

AllowableLeakage <

?

Are

Allowable Ts <

?

PerformDetailedEvaluation

Reduce

Leakage

Configurat ionDevelopment Phase

Monitor ing &Evaluat ion Phase

YesN o Yes

N o

Yes

N o

(e.g., add sensors)

OutleakageObjective

InleakageObjective

MonitoringRequired

?

N o

Yes

Figure 3-1Thermal Fatigue Monitoring Process

4-1

4 TYPES OF SENSORS FOR MONITORING

The types of parameters recommended for monitoring to detect and characterize thermal cycling in piping attached to the RCS include piping outside surface temperatures, as a minimum, and the additional parameters of fluid pressure and flow rate, piping displacements, and possibly local pipe strain as deemed appropriate. System parameters (e.g., RC pressure, temperatures, and loop flows or pump status) are also necessary for interpretation of collected data.

Generally, the recommended method for measurement of temperatures is to use externally mounted thermocouples. There are obvious advantages of outside rather than inside wall measurements in a plant program for thermal fatigue monitoring. However, to make a determination of the acceptability of outer surface measurements an evaluation needs to be made of the accuracy requirements for cyclic temperature variations and the ability of outside wall temperatures to meet these requirements for various values of pipe wall thicknesses.

Temperature measurements on the outside surface of piping may be used for monitoring of near-steady or slowly varying thermal stratification (e.g., for periods of oscillation on the order of a minute or more). However, because of attenuation through the wall, more rapid variations may not be observable at the outer surface. Figure 4-1 illustrates typical differences in amplitudes of temperature oscillations between the inside and outside of piping due to attenuation. Using outside temperature measurements, temperature variations on the piping inside surface may be recoverable using signal processing techniques (refer to Reference 2 for a description of the method). However, cyclic information above a certain frequency at the inside surface of the pipe can be lost, depending on the particular pipe wall thickness and metal thermal properties. Also, the ability to accurately transform outside surface temperature measurements to the inside surface is limited by the level of noise in the signal, possibly resulting in the introduction of significant errors in the predictions of inside temperature variations.

Figure 4-2 illustrates how the through-wall attenuation of the amplitude of temperature oscillations varies with cyclic period, specifically for stainless steel piping with ½ inch wall thickness. The figure is based on calculated results using an analytic solution for the temperature distribution through a flat plate with a periodic surface temperature. As shown, the amplitude of inside temperature oscillations with a period of about 25 seconds is reduced by a factor of 10, i.e., the outside amplitude is only 10 percent of the value at the inside surface. For cyclic periods below about 10 seconds, the outside amplitude is less than 1/30th, or about three percent, of the inside value.

This also shows the importance of adjusting the measurements made using sensors mounted on the outside of the piping to reflect the amplitude of temperature variations at the inner surface. For example, if outside measurements indicated an oscillation period of 15 seconds, the inside amplitude would be about 20 times that observed on the exterior.

Types of Sensors for Monitoring

4-2

Thermocouple-pairs mounted top and bottom on the piping OD at the valve are generally adequate for detecting the occurrence of significant leakage (i.e., leakage that results in non-negligible thermal cycles).

Where the magnitude of the temperature is less important than the difference in temperature, e.g., for top-to-bottom temperature difference, thermocouples can be set up in series fashion to produce a signal directly proportional to the temperature difference (see Figure A-2). This type of arrangement will provide a more accurate measure of temperature differential than taking the difference between two separate temperature measurements.

Thermography can be useful for determining the temperatures of piping under steady conditions, including steady thermal stratification in stagnant or near-stagnant, un-insulated lines. However, this method is not considered appropriate for purposes of monitoring to detect significant thermal cycling. This is primarily a result of the inability to assure that short-term "spikes" in temperature will be captured at the time the thermograph is made, since spikes caused by turbulent penetration, for example, may occur at random intervals separated in time by many minutes, or even hours. In addition, temperature fluctuations on the inside of the pipe are significantly attenuated by the pipe. Therefore, thermography is of extremely limited value for detecting thermal cycling due to certain mechanisms and is not considered an important tool in thermal fatigue monitoring.

Pressure monitoring can be used to indicate potential for leakage into or out of the RCS. However, the ability to determine the true pressure difference based on two separate measurements is limited in cases where the difference approaches the sum of uncertainties in the two pressure measurements. Consequently, pressure measurements using existing instruments (e.g., RCS pressure and HPI pressure) would be of limited use because of the associated uncertainties and the need to correct for elevation differences. For gross indications, existing pressure measurements would be acceptable. However, for conditions where small differences in pressure could exist, which could occur for certain valve lineups and valve leak rates, the uncertainties in pressure measurements could conceivably lead to an incorrect conclusion as to the direction of potential leakage. A local delta-pressure measurement at the valve would be less subject to effects of measurement error, but this would require pressure taps in the piping, which if they need to be installed would be expensive. For the case of slight pressure differences between RCS loops, even a local delta-pressure measurement may not be sufficiently accurate to properly indicate the direction of flow through cross-connected lines in the case of low leakage flow rates (which do not require more than a few psi pressure difference to drive flows that are a significant fraction of one gallon-per-minute).

Flow rate in the RCS attached piping may be an important monitoring parameter if the flow rate is throttled to the range where thermally stratified flow results, such as in the makeup line for B&W plants, for example. In this type of situation, the flow rate and pipe size influence the stratified layer depth in the pipe, thereby determining the general characteristics of the pipe temperature distribution in the circumferential direction.

Piping displacement measurements are needed in some cases to confirm the accuracy of the temperature data or to determine when the pipe comes into contact with a hard stop, e.g.,


4-3

structural concrete. These measurements can be vital in discovering an interference that alters the pipe displacement and loading in relationship to free thermal growth. The displacements will be used to provide analytical benchmarks showing that the thermal input to the model correctly predicts the displacements. Note that the displacement measurements and strain gages are a secondary source of information used to ensure that an analytical model is working correctly. As such, it is very important that the location of the measurements is communicated correctly to the analyst. Small changes in displacements at the measurement location due to thermal stratification can yield large changes over a substantial length of pipe, while the stratification temperatures may remain fairly constant over the length. Successfully correlating displacements with analytical predictions relies upon all the information for both displacements and temperatures at corresponding times being communicated correctly to the modeler.

Strain gages are useful in some instances to provide a direct measure of piping strain to supplement the more indirect and perhaps less accurate methods such as inference from a set of piping temperature measurements. Theoretically, strain gages would give a direct measurement of the “strain” resulting from the pipe deformity caused by thermal effects. The complexity of the measurement and uncertainty of the results have limited their use in “fatigue” applications to “information only.” To utilize strain gages, the designer must know if the measurement should detect static or dynamic strain and the appropriate strain direction. For this application, the sensors must either be temperature compensated or include a “dummy” gauge (no strain, only temperature effect) and it is recommended that individual “gauge factors” for each sensor be known (measured). Sensors are difficult to install and must be installed for each axis and the proper measurement bridge configuration selected.

Plant status information is essential to the analysis of data. This should include global primary system status to allow identification of initiating events and baseline plant conditions. This information can be gathered from the plant computer either “off-line” or “on-line” through simultaneous monitoring. Parameters of interest would be RCS temperatures, RCS pressure, RC pump status, pressurizer level, pressurizer spray and heater status, makeup and letdown flows, and any safety injection status.

Additional details regarding temperature and displacement sensors and measurements are included in Appendices A and B.


4-4

Figure 4-1Inside and Outside Pipe Surface Temperature Variations - Illustrating Typical AttenuationThrough Pipe Wall


4-5

0

20

40

60

80

100

120

0 5 10 15 20 25

Cyclic Period, sec

Att

enu

atio

n *

Figure 4-2 Attenuation of Through-Wall Temperature Oscillations with Cyclic Period

* Attenuation is defined here as the amplitude of the temperature oscillation at the ID of the pipe divided by the amplitude of the temperature oscillation at the OD of the pipe. As such, it is a reduction factor applied to the inside excitation to obtain the outside response, or conversely, an amplification factor applied to the outside observation to obtain the inside excitation. For example, an attenuation of 40 means that the outside amplitude is only 1/40th of the inside, or the inside amplitude is 40 times that observed on the outside. (Note that the attenuation cannot be less than 1.0 (no attenuation), but full attenuation corresponds to a value of infinity.)

The chart shows a calculation of attenuation for a stainless steel pipe of a particular diameter and wall thickness. As an example, if the inside pipe wall experiences a temperature oscillation with a period of approximately 15 seconds and an amplitude of 50°F, the amplitude of the outside pipe wall temperature oscillation will be about 1/20th, or 2.5°F. Longer periods will reduce the attenuation factor, and thus increase the amplitude of the outside temperature oscillation while shorter periods will decrease the exterior amplitude.

5-1

5 MONITORING LOCATIONS

This section presents recommendations for placement of monitoring sensors for variousrepresentative piping layouts which are considered subject to possible thermal cycling. Thethermal cycling may result from thermally stratified flow (TS), turbulent penetration (TP), or TPand TS interaction due to in-leakage/inflow (TP/TS).

These recommendations deal with the details of thermocouple (T/C) placement (or other types oftemperature sensors) for measurement of piping temperatures. The placement of sensors forother monitoring purposes, such as for displacement measurements, are discussed in Section 4.

Figures 5-1 through 5-7 illustrate the preferred placement of T/Cs for various pipingconfigurations. Because these configurations include upward (vertical and inclined), horizontal,and downward (vertical and inclined) orientations these figures are believed to encompass allattached piping configurations. Table 5-1 is a key to these figures.

The specific recommendations for T/C placement depend on the particular mechanism of thermalcycling of concern (for the particular piping configuration), whether TP, TS, or TP/TS. Bothmaximum and minimum coverage are included to conform to the possible range of monitoringobjectives, from the goal of simply detecting whether cycling occurs (minimum coverage) todetermining the detailed temperature distributions for input to a fatigue evaluation (maximumcoverage). An option is identified for more extensive coverage, for the case where the addeddata is needed or desired (possibly to refine calculations where margins need improvementand/or uncertainties need to be minimized).

In describing preferred T/C placement, the terms "hot-trap" and "cold-trap" are sometimes used.A "hot-trap" is an inverted U-section of piping (normally provided with vent connections),whereas a "cold-trap" is a U-section, i.e., loop-seal (normally provided with drain connections).

In the accompanying sketches showing preferred T/C placements, the following abbreviationsare used:

OPT - optional monitoring locations

T&B - top and bottom of horizontal (or near-horizontal) pipe

C-C - spaced around circumference of horizontal pipe, including T&B

S-S - one (or two opposed) T/Cs placed on a vertical (or near-vertical) pipe.

Monitoring Locations

5-2

For T&B positions, consideration should be given to including redundant T/Cs at either the topor bottom at critical locations where loss of data could essentially defeat the purpose of themonitoring operations. Also for the T&B configuration, T/Cs could also be positioned to includeone sensor at the top for temperature with a second top/bottom T/C pair connected in series tosense the temperature difference directly.

The C-C designation, for placement around the pipe circumference, is intended for T/Cs from 0degrees (at bottom of pipe) to 180 degrees (at top), on one side of the pipe. The number of T/Csranges from three, as a minimum, to as many as seven or more, with various values of angularspacing, depending on the pipe diameter and the purpose of the measurement. (For thisdescription, the ranges of nominal pipe sizes are defined as (1) small – 1 to 2 inches, (2) medium– 2 to 6 inches, and (3) larger – 6 to 14 inches or more. Table 5-2 describes the range ofpreferred T/C placements for the C-C layout.

Table 5-1Key for Thermocouple Placement Figures

Objective of Monitoring

In-leakage Out-leakage1 TurbulentPenetration

Configuration

Min Max Min Max Min Max

Upward-to-Horizontal-to-Valve (UHV) 5.1a 5.1b 5.1c 5.1d

Horizontal-to-Upward-to-Horizontal-to-Valve(HUHV)

5.2a 5.2b 5.2c 5.2d

Horizontal-to-Valve (HV) 5.3a 5.3b 5.3c 5.3d

NA

Horizontal-to-Downward-Horizontal-to-Valve(HDHV)

5.4a 5.4b 5.4c 5.4d 5.4e 5.4f

Downward-to-Horizontal-to-Valve (DHV) 5.5a 5.5b 5.5c 5.5d 5.5e 5.5f

Hot Trap 5.6a 5.6b 5.6c 5.6d

Cold Trap 5.7a 5.7b 5.7c 5.7d

NA

1 While not currently perceived to be a cause of thermal fatigue, monitoring for out-leakage is presented forcompleteness.


5-3

Table 5-2T/C Placement Around Circumference of Pipe (for C-C designation)

Phenomenon/(Purpose ofMeasurement)

Line Size Number of T/Cs Angular Position,(Bottom = 0 o)

small (1" to 2") 3to5

0, 90, 180

0, 45, 90, 135, 180

medium (2" to 6") 5to7

0, 45, 90, 135,180

0, 30, 60, 90, 120, 150, 180

TS

(Resolve temperaturedistribution aroundcircumference.)

large (6" to 14") 7 0, 30, 60, 90, 120, 150, 180

small to medium(1" to 6")

3 0, 30 to 45, 180In-leakage

(Detect in-leakage andprovide a measure ofstratified cold-layerdepth.)

large (6" to 14") 3 0, 15 to 30, 180

small to medium(1" to 6")

3 0, 135 to 150, 180Out-leakage

(Detect out-leakage andprovide a measure ofstratified hot-layerdepth.) large (6" to 14") 3 0, 150 to 165, 180

Local considerations for T/C placement -- For locations at or near:

• pipe elbows - on pipe, with clearance of at least one weld-bead width from weld.

• RCS nozzles / thermal sleeves - on pipe, spaced at least one weld-bead width from weld.

• valves - on pipe, spaced a distance from the valve of at least three times the pipe-wallthickness.

• piping supports - on pipe, spaced at least one pipe diameter from support.


5-4

(a ) M in imum CoverageDetec ts TP/TS Thermal Cyc l ing Near Va lveDetects In f low/ In- leakage Cyc les

(b ) Max imum CoverageCol lec t Data for Fat igue Evaluat ionTP/TS, TS Thermal Cyc l ing A long Hor izonta l

T&B ( In - leakage may be detec ted by B on ly )T&B (OPT)

T&B (C-C OPT)

T & BC-CT&B (OPT)

Ei ther Vert ica l or Inc l ined Pip ing

One or More Hor izon ta l Runs

Figure 5-1 (a) and (b)Thermocouple Placement Upward-to-Horizontal-to-Valve Configuration Inflow/In-leakage


5-5

(c ) Min imum CoverageDetects Outf low/Out- leakage Cycles

(d) Max imum CoverageCollect Data for Fatigue EvaluationTS Thermal Cycl ing Along Horizontal

T&B

T&B

Either Vertical or Incl ined Piping

One or More Horizontal Runs

T&B (C-C OPT)

Figure 5-1 (c) and (d)Thermocouple Placement Upward-to-Horizontal-to-Valve Configuration Outflow/Out-leakage


5-6

(a) Minimum CoverageDetects Inf low/ In- leakage Cycles

(b) Maximum CoverageCol lect Data for Fat igue Evaluat ionTP/TS, TS Thermal Cyc l ing Along Hor izonta l

T & B

C-C

Either Vert ical or Incl ined Piping

One or More Hor izonta l Runs

T & B

T&B (OPT)

Detects TP/TS Thermal Cyc l ing

T&B (OPT)

T&B (C-C OPT)T&B (OPT)

Figure 5-2 (a) and (b)Thermocouple Placement RCS-to-Horizontal-to Up (or Inclined)-to-Horizontal-to-ValveConfiguration Inflow/In-leakage


5-7

(c) Minimum CoverageDetects Outf low/Out- leakage Cycles

(d) Maximum CoverageCollect Data for Fatigue EvaluationTS Thermal Cycl ing Along Horizontal

T&B

Either Vertical or Incl ined Piping


T&B T&B (C-C OPT)

Figure 5-2 (c) and (d)Thermocouple Placement RCS-to-Horizontal-to-Up (or Inclined)-to-Horizontal-to-ValveConfiguration Outflow/Out-leakage


5-8



T & B

C-C


Detects TP/TS Thermal Cyc l ing

T & B


T&B (OPT)

Figure 5-3 (a) and (b)Thermocouple Placement RCS-to-Horizontal-to-Valve Configuration Inflow/In-leakage


5-9

(c) Minimum CoverageDetects Out f low/Out- leakage Cycles

(d) Maximum CoverageCol lect Data for Fat igue Evaluat ionTS Thermal Cyc l ing Along Hor izonta l

T & B

T & B


T&B (C-C OPT)


Figure 5-3 (c) and (d)Thermocouple Placement RCS-to-Horizontal-to-Valve Configuration Outflow/Out-leakage


5-10



T & B



Detects TP, TS Thermal Cyc l ing

T&B (C-C OPT)

T & B

S-S

T & B

T & B



T&B (OPT) S -S

T & B

T & B

T & B

If more than 25 d iametersbeyond RCS T/C on ver t ica land lower hor izontal not required.

Figure 5-4 (a) and (b)Thermocouple Placement RCS-to-Horizontal-to-Down (or Inclined)-to-Horizontal-to-ValveConfiguration Inflow/In-leakage


5-11

(c ) Min imum CoverageDetects Out f low/Out- leakage Cycles

(d) Max imum CoverageCol lect Data for Fat igue Evaluat ionTP, TS Thermal Cyc l ing A long Hor izonta l

T & B






T&B (OPT) S -S

T & BT & B

Figure 5-4 (c) and (d)Thermocouple Placement RCS-to-Horizontal-to-Down (or Inclined)-to-Horizontal-to-ValveConfiguration Outflow/Out-leakage


5-12

(e) Minimum CoverageDetects Turbulent Penetration Cycles

( f ) Maximum CoverageCollect Data for Fatigue EvaluationTP, TS Thermal Cycling Along Horizontal

Either Vertical or Inclined Piping


Detects TP, TS Thermal Cycling

S-S

T&B

Either Vertical or Inclined Piping


S-S

T&BT&B

If more than 25 diametersbeyond RCS, T/Cs on verticaland lower horizontal not required.

If more than 25 diametersbeyond RCS, T/Cs on verticaland lower horizontal not required.

Figure 5-4 (e) and (f)Thermocouple Placement RCS-to-Horizontal-to-Down (or Inclined)-to-Horizontal-to-ValveConfiguration No Leakage (Turbulent Penetration)


5-13

(a) Min imum CoverageDetects Inf low/In- leakage Cycles

(b) Max imum CoverageCol lect Data for Fat igue Evaluat ionTP/TS, TS Thermal Cyc l ing A long Hor izonta l



S-S

T & B


T&B (OPT)


S-S

T & B


T & BT & B

T & B

If more than 25 d iametersbeyond RCS, T/Cs on hor izonta lnot required

I f more than 25 d iametersbeyond RCS, T/Cs on hor izonta lnot required

Figure 5-5 (a) and (b)Thermocouple Placement RCS-to-Down (or Inclined)-to-Horizontal-to-Valve ConfigurationInflow/In-leakage


5-14

(c) Minimum CoverageDetec ts Out f low/Out - leakage Cyc les

(d) Maximum CoverageCol lect Data for Fat igue Evaluat ionTP, TS Thermal Cyc l ing A long Hor izonta l


Detec ts TP, TS Thermal Cyc l ing

T & B

Either Vert ical or Inc l ined Pip ing

T&B (OPT)


S - S

Either Vert ical or Inc l ined Pip ing

T & BT & B

T & B

Figure 5-5 (c) and (d)Thermocouple Placement RCS-to-Down (or Inclined)-to-Horizontal-to-Valve ConfigurationOutflow/Out-leakage


5-15

(e) Minimum Coverage

(f) Maximum CoverageCol lect Data for Fat igue Evaluat ionTP, TS Thermal Cycl ing Along Hor izonta l



S-S



S-S


T & BT & B

T & B

Figure 5-5 (e) and (f)Thermocouple Placement RCS-to-Down (or Inclined)-to-Horizontal-to-Valve ConfigurationNo Leakage (Turbulent Penetration)


5-16

(a) Minimum CoverageDetects Inflow/In-leakage Cycles

(b) Maximum CoverageCollect Data for Fatigue EvaluationTS at Measurement Location

Detects TS Thermal Cycling

T&B

Refer to other appropriatefigure for specific layout of RCS to first valve.


First in a seriesof downward steps

in a run of piping

T&B

Refer to other appropriatefigure for specific layout of RCS to first valve.



in a run of piping

Figure 5-6 (a) and (b)Thermocouple Placement Outboard of First Valve – Through Hot Trap Inflow/In-leakage


5-17

(c) Minimum CoverageDetects Out f low/Out- leakage Cycles

(d) Maximum CoverageCol lect Data for Fat igue Evaluat ionTS at Measurement Locat ion

T & B

Refer to other appropr iatef igure for speci f ic layout of RCS to f i rs t valve.


First in a seriesof upward s tepsin a r iser sect ion.



First in a seriesof upward s tepsin a r iser sect ion.

T & B

T&B (OPT)

T&B (OPT)

Figure 5-6 (c) and (d)Thermocouple Placement Outboard of First Valve – Through Hot Trap Outflow/Out-leakage


5-18


(b) Maximum CoverageCol lect Data for Fat igue Evaluat ionTS at Measurement Locat ion



First in a seriesof upward s teps

in a r iser sect ion.

T & B


First in a seriesof upward s teps

in a r iser sect ion.

T & B


Figure 5-7 (a) and (b)Thermocouple Placement Outboard of First Valve – Through Cold Trap Inflow/In-leakage


5-19

(c ) Min imum CoverageDetects Outf low/Out- leakage Cycles

(d) Max imum CoverageCollect Data for Fatigue EvaluationTS at Measurement Locat ion

Refer to other appropriatefigure for specif ic layout of RCS to f i rst valve.



in a run of piping

Refer to other appropriatefigure for specif ic layout of RCS to f i rst valve.


in a run of piping


S-S

S-S

T&B

T&B T&B (OPT)

Figure 5-7 (c) and (d)Thermocouple Placement Outboard of First Valve – Through Cold Trap Outflow/Out-leakage

6-1

6 DATA ACQUISITION AND TRANSMISSION

The data acquisition system (DAS) design should consist of application-specific components forinstrumentation, data acquisition, and data reduction. It can utilize state-of-the-art, commerciallyavailable hardware and software with the following features. An important design considerationis to utilize distributed remote I/O data acquisition hardware that is modularly expandable toallow expansion-contraction flexibility. On-line data reduction software should be employed toturn data into information in a real-time format to facilitate analysis. Special softwareconfiguration can provide event or condition triggered application files coupled with long-term(two years or greater) data storage and on-demand downloading of continuously monitoredlogged data. Periodic status reports can be automatically generated and user defined reports ordata analysis can be available when needed. Threshold limits can be used to alarm conditionsrequiring investigation. A historical database can be generated from the distributed inputs,including monitoring temporary sensors and existing plant signals, and linking to a plantcomputer for plant status. The system should provide real-time information stored with anaccessible database server and plant network compatibility. Figure 6-1 provides an overviewexample.

Data Acquisition and Transmission

6-2

Figure 6-1Illustration of Recommended System Configuration


6-3

6.1 Data Acquisition

When considering the purchase of a data acquisition system, too much emphasis is often placedon the cost of the data acquisition hardware, without giving enough thought to the overall systemand software. Unexpected costs for system configuration and software typically approach orexceed the cost of the hardware itself.

Small to medium size systems vary from limited channels to larger systems with up to 100 inputchannels, ranging from dedicated specialty units to portable or fixed flexible systems. Acommon purchasing guideline for evaluating potential DAS equipment has always been “cost-per-channel.” Hardware manufacturers are aware of this guideline and present products in theirliterature to reflect a low cost-per-channel. This "universal" guideline can be very misleading,unless the overall cost of implementation is considered.

For applications from 4 to 40 channels, medium size or transportable products range from $200to $300 per channel. The hidden costs are found in inflexibility for expansion and data handling(storage, analysis). These may not be easily “distributed” and quite often end up with unusedchannels (e.g. need 23, purchase 20-per-card). Distributed front-ends also normally provide afixed number of inputs per I/O card (8 to 20) and are almost always dedicated to one input type.

The largest risk factor, or hidden cost, is always software. Too often, products provide driversthat enable logging data in ASCII or CSV file format or provide communication links (dynamicdata exchange, DDE) to allow communicating with “any” Windows application. Be aware thatany software package that requires using a range of instrument command sets, or requirescomplex high-level statements as part of configuration, is likely to prove costly. An off-the-shelfsoftware package may seem expensive at $500 to $3000, but the difference between a lessexpensive system and this amount is very often spent interfacing the hardware with the softwareor in efforts spent collecting data and turning it into information.

“Plug-n’-Play” PC bus plug-in boards have similar problems as portable or “remote I/O" in thatthey normally have dedicated input types, 8 to 20 channels per card and normally lack isolation,signal conditioning, and the ability for distributed acquisition. Whereas these can beexceptionally fast (already on the PC bus) the specified accuracies and environmental tolerancesmay not apply to the thermal fatigue monitoring applications range of environmental conditions.

System integration and software are almost always more important in total cost than thehardware procurement costs. All hardware products include minimum software to allow loggingdata and displaying some channels on the PC screen. However, acquiring useful data andturning data into useful information can be handled either with significant analysis man-hours,continuing software involvement, or with the purchase of an adequate integrated system andsoftware at the beginning.

6.2 Data Transmission

Data acquisition is accomplished either through local storage (long signal leads to a logger orlogger(s) located near signal source) or acquired with a distributed “remote I/O” and transmittedto the logger (“file server” with network link).


6-4

Data transmission is typically accomplished via serial RS-232 or RS-422/485, manufacturerproprietary data highway, network (e.g., Ethernet), or wireless. RS-232 is a “live-zero” signalthat has limited speed (<19K baud) and distance (typical 50 feet). To avoid noise interferenceand data loss, the RS-422 (or 485) signals can be used, which are “differential” allowing highertransmitting speed without interference and therefore longer distances (a few thousand feet).Network communication is much faster than serial and can go long distances depending on cabletype. Wireless transmission has the advantage of not needing cables but requires a reasonableline-of-site, may require repeaters, has limited throughput capability, and cannot penetratecontainment walls. Thus, for attached piping applications network or RS-422 communication isrecommended.

6.3 Smart-Front-End versus Raw Data Acquisition

In cases where the application goals are reasonably well defined (as is the case with thermalfatigue monitoring) there may be advantages in a system that includes calculation capability atthe data acquisition front end. A good example would be a programmable logic controller PLCbased data acquisition system that allows for significant signal processing “up front” beforesignal transmission. This has the advantage of processing the data as it is collected andconverting it to information already in an application specific format. The PLC remote I/Omethod can provide the following functions:

• all signal conditioning

• data processing (volts-to-engineering units conversion)

• input running average

• channel averaging

• time averaging

• offset correction

• special calculations on combined channels

• input dead bands

• logged data exception reporting

• built-in counters for discrete events

• the capability to convert signals using linear, log, or square root functions

The processed information and data would be transmitted to a data acquisition to PC running aWindows application software that provides these functions:

• various runtime trend graph screens, pre-configured for on-line data analysis

• historical logging (a separate log file per day with deadbands and exception reporting)

• statistics calculations

• links to Excel and an analysis program

• alarms


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If such processing is known to be desirable, it is usually best to accomplish it automatically at thetime of data acquisition. While this processing can also be accomplished in an off-line PC, datatends to accumulate and may not be post - processed if it is not automated or made part of thesoftware.

6.4 In-Containment Installation

As has been discussed and presented in Figure 6-1, there is an advantage to be able to have thedata acquisition equipment located inside containment and the data be accessible outsidecontainment. Environmental considerations of concern for in-containment include those listedbelow:

• Radiation levels

• Temperature

• Humidity

• Vibration

It is normally possible to find locations within containment with an environment acceptable fordata acquisition hardware. Since the combination of temperature and humidity is of concern, theequipment is typically mounted as a special cabinet (to facilitate field connections) with forcedventilation, which can include a heat exchanger or air-conditioning unit.

Electronic equipment must be located in an area not exposed to high radiation. Equipmentperformance will degrade above 103 rad with failures occurring near 104 rad. In general, alocation can be found with radiation levels less than 50 mR/hr, which would be acceptable forlong-term (many years) operation. If the radiation levels exceed 1R/hr, the data acquisitionequipment may not survive one fuel cycle. Applications with equipment that will only be usedfor one heatup should not experience long-term dose effects, but still need to be outside of anyhigh dose rate area.

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7 MONITORING EXPERIENCE SURVEY

A survey of thermal fatigue monitoring experience by operating plants was conducted for thisreport. The responses from this survey are provided in Appendix C.

The state-of-the-art for this type of product changes rapidly. In general, the data acquisitionhardware and software used by the respondents would be considered out of date by today'stechnology standards. However, the problems reported by respondents can still provide usefulinsight for plants currently considering a monitoring system.

Sensor Types

For temperature monitoring, respondents reported experience with Resistance TemperatureDevices (RTDs) and Thermocouples (T/Cs). While both types of sensors were reported to beeffective, a plant that had experience with both types reported that they would use T/Cs, ifadditional monitoring were needed. FTI has selected T/Cs for providing temporary monitoringservices to plants, and has found them to be reliable.

T/Cs offer the convenience of two wires, compared to three or four wires for RTDs. Anadditional consideration for RTDs is the need for a bridge circuit for data acquisition.

Mounting Methods

Mounting – RTDs• RTDs cemented to pipe with leads fed through a penetration so they could be

monitored at power.• RTDs banded to the pipe with stainless steel bands.

Mounting - T/Cs• T/Cs spot-welded to a stainless steel band that is fastened to the pipe with a constant

torque clamp.• Stainless steel pipe clamps with attached tubes that are perpendicular to pipe;

thermocouples are inserted into tubes.• Weed type E curved radius T/Cs held in place with stainless steel pipe clamps.

Sensor Problems

Only one plant reported a problem specific to RTDs. Most problems reported could applyequally to RTDs or T/Cs.

Monitoring Experience Survey

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Problems – RTDs• Difficult to trouble shoot; long run for lead wires made isolation of problems

difficult.• RTDs [on the downstream side of first block valve off the RCS loop] were removed

from service because of reliability problems.• RTDs and lead wire subject to damage during ISI, insulation, etc.• Lack of redundancy when an RTD fails.• RTDs were initially installed as temporary and thus are not as rugged as permanent

plant instrumentation.

Problems – T/Cs• Changed from Gordon thermocouples mounted perpendicular to the pipe (was

difficult to maintain a good reading) to Weed type E curved radius T/Cs.• Thermocouples can come loose; connections can be made incorrectly (top reading

is bottom temperature and vice versa); installation is temporary, and shows it.• Encounter problems, if people step on insulation.• "Funny data" – i.e., thermocouples wired wrong, or bad thermocouple.

Data Acquisition

Various data loggers were reported without a clear preference for any particular type. Usuallythe data acquisition software was supplied with the data logger. Most did not identify thesoftware that was used for data acquisition. One plant reported using EPRI/SIA FatigueProsoftware to monitor existing plant instrumentation, which allows fatigue analysis associated withplant transients.

Data Acquisition Hardware• Two Fluke NetDAQ units and a network hub custom installed in a single cabinet in

containment.• Fluke Helios extender chassis in containment receiving about 80 T/C inputs; Fluke

Helios data acquisition unit and PC in cable spreading room for data logging.• Beckman Industrial (BI) data logger and BI Digitrack 360 drive• HP 34970A Data acquisition logger• Fluke 2280 datalogger• Wang and Omega data loggers

Data Acquisition Software• Fluke NetDAQ Logger software for data acquisition; Fluke Trend Link software

for viewing the data.

Monitoring Experience Survey

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Data Handling

Typically, a data logger produces a data file that is transferred either manually (e. g. floppy disk)or electronically to a PC for analysis using a spreadsheet, such as Microsoft Excel or Lotus 123.

Reported Data Handling Methods• T/Cs terminated to input cards in containment; connected by single Ethernet cable

through penetration to PC in cable spreading room. PC logs data that is manuallydownloaded to a Zip drive and transferred to another PC for analysis.

• T/Cs terminated to input cards in containment; connected by single RS-422 cablethrough penetration to data acquisition front end and PC in cable spreading room.PC logs data that is manually downloaded to a Zip drive and transferred to anotherPC for analysis.

• For drains and spray line, used a data logger connected to a PC. For other lines,fed leads through a penetration so they could be monitored at power.

• Data is collected by data logger and sent, by RS232 communications, to a plantcomputer that stores selected data. Periodic reports are generated off an Excelspreadsheet. Data is reviewed bi-weekly by site system engineers. Evaluate anydata that does not meet the IEB 88-08 criteria.

• Data logger linked to Digitrack 360 drive; provides a floppy disk with data fileretrievable by Lotus 123.

Monitoring Frequency and Rate

Frequency Rate

• Continuous • 30 sec samples for some (spray), 5 min samples for others

• Continuous • Data is collected every minute

• Following powerascension and every 6months

• Not available

• Quarterly and duringheat up

• Log data at 10 second intervals for 10 min, then at 10minute intervals for 24 hours

Monitoring Duration

Two plants reported that monitoring had been discontinued because the collected data showedthat there was no thermal stratification. The rest plan to monitor indefinitely.

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8 ACRONYMS

The following acronyms and abbreviations were used in this report:

ASCII ANSI standard character

C-C Monitoring location - spaced around circumference of horizontal pipe, includingT&B

CF Core Flood

CSV Comma Separated Variable data format

DAS Data Acquisition System

DHR Decay Heat Removal

DHV Attached piping configuration that runs vertically downward from the RCS andthen turns horizontal to a control or check valve

DIN German Industry Standard

EMF Electromotive Force (Voltage generated in T/C wire with temperature gradients)

HDHV Attached piping configuration that runs horizontally from the RCS, turnsdownward, turns horizontal to a control or check valve

HUHV Attached piping configuration that runs horizontally from the RCS, turns upward,turns horizontal to a control or check valve

HV Attached piping configuration that runs horizontally from the RCS to a control orcheck valve

ID Inner Diameter (of pipe)

ITG Issue Task Group

LVDT Linear Variable Differential Transformer

MRP Materials Reliability Project

Acronyms

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NRC Nuclear Regulatory Commission

OD Outer Diameter (of pipe)

OPT Optional monitoring locations

PLC Programmable Logic Controller

PT Position Transducer

PWR Pressurized Water Reactor

RTD Resistance Temperature Detectors/Devices

SQL Structured Query Language (real time, relational data base)

S-S Monitoring location - one (or two opposed) T/Cs placed on a vertical (or near-vertical) pipe.

T&B Monitoring Location - Top and bottom of horizontal (or near-horizontal) pipe

T/C Thermocouple

TF Thermal Fatigue

TP Turbulent Penetration

TP/TS TP and TS interaction due to in-leakage/inflow

TR Reference Temperature

TS Thermally Stratified Flow

RCS Reactor Coolant System

RHR Residual Heat Removal

SDC Shutdown Cooling

UHV Attached piping configuration that runs vertically upward from the RCS and thenturns horizontal to a control or check valve

9-1

9 REFERENCES

1. TR-1001006, Operating Experience Regarding Thermal Fatigue of Unisolable PipingConnected to PWR Reactor Coolant Systems (MRP-25), EPRI, Palo Alto, CA,:

2. Guyette, M., Prediction of Fluid Temperature from Measurements of Outside WallTemperatures in Pipes, ASME Journal of Pressure Vessel Technology, 116 (1994) 179-187.

3. Muroya, I. et al, “The Evaluation System of Thermal Stratification Stress Using OuterSurface Temperature” presented at the International Conference on Fatigue of ReactorComponents, Napa, CA, July-August 2000.

A-1

A TEMPERATURE MEASUREMENT

A.1 Resistance Temperature Detectors and Thermocouples

The two most common methods of measuring plant component exterior temperatures are withresistance temperature detectors (RTD) or thermocouples (T/C). The decision on which to use isusually determined from consideration of temperature range, response time, size, overallaccuracy, installation concerns and cost.

A.1.1 Temperature Range

For the thermal fatigue monitoring application, the points to be monitored fall into twocategories:

• Those in proximity to the RCS with maximum temperatures between 550oF and ~650oFpossible.

• Those on piping or components some distance from the RCS, without continuous flow, withtemperatures below 300oF.

Both RTDs and T/Cs envelop this range. The temperature to be sensed affects the sensorconfiguration and type of insulation used for the instrumentation cables. RTDs would be thesame for both ranges.

T/C configurations would be different for the two ranges with respect to accuracy, wireinsulation, and cost. To minimize cost for a long length T/C, the higher temperature applicationwould possibly use an extension wire in conjunction with a high temperature (>350oF) T/C. Forthe high temperature range, the T/C should use a glass braided insulation with a stainless steelprotective overbraid. Because of the high cost associated with this type it is usually used incombination with lower cost T/C extension cable with Teflon, PVC, or Tefzel insulation.

A.1.2 Response Time and Monitoring Frequency

As was shown and described with Figure 4-1, there is significant response attenuation whenmonitoring pipe fluid temperature with sensors on the outside wall. Experience indicates thatsampling at rates faster than 10 to 30 seconds does not provide additional information withrespect to absolute temperature. Since the major influence is a “damping of the amplitude,”sampling faster could however still give information about cyclic frequency.

Temperature Measurement

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It is general knowledge that a T/C responds faster than an RTD. This difference is only ofsignificance when a response time of less than one second is important. For the thermal fatiguemonitoring application the slower system response is generally the main concern and installationtechnique is more important to response than sensor type.

FTI has performed response time tests on various T/C and RTD configurations (exposed versussheathed, grounded versus ungrounded T/C, sheath thickness) to use as guidance for monitoringfrequencies. These can be summarized for functional purposes:

Sensor Type Dead Time Rise Time Settling TimeExposed T/C .01s 0.2s 0.7sExposed RTD .02s 0.2s 0.8s1/8" sh. ground T/C .04s 0.5s 1.6s1/8" sh. underground T/C .11s 0.9s 2.7s1/8" sh. RTD .14s 2.0s 6.0s

Sheath Thicknesses (all type K T/C)Exposed 0.01s 0.2s 0.7s1/16" 0.03s 0.27s 0.9s1/8" 0.11s 0.9s 2.7s1/4" 0.23s 2.7s 7.0s

dead time : the time lag before a material response occurs (e.g., 1% for a step response).

rise time: similar to time constant, the time requires to reach more than 60% in response to astep impulse.

settling time: the time required to reach (and stay within) 1% of the final value.

Based upon these limitations on sensor response it appears that when using a 1/8" groundedjunction T/C, monitoring much faster than every few seconds would not greatly increase dataquality. Based upon FTI experience with thermal fatigue monitoring data it is possible to detectcycling, approaching 50 degrees peak-to-peak and a 2 minute frequency on RCS nozzles, with a30-second sampling rate. This leads to a recommendation for a data scanning rate of 10 to 30seconds for locations susceptible to cycling.

As presented above, sensor size can be a consideration if the attached piping is not controllingresponse. Size does not become a concern with installation since miniature size RTDs and T/Care available today that make size a non-issue for most installations. A difference would be thatRTDs must be purchased whereas a T/C can be fabricated to facilitate installation and improveaccuracy. For very small diameter pipes (~1") the standard RTD sheath sizes of ~0.1" diameterrequire more attention to installation than a standard sheathed T/C of <0.05".

A.1.3 Temperature Measurement Accuracy

Overall accuracy is a multifaceted topic that is influenced by many factors and can be improvedthrough selection and testing. It is best to discuss this as measurement uncertainty rather than aninaccuracy or error. This uncertainty is also different for an absolute measurement than for a


A-3

differential measurement. Since temperature differences less than about 50oF or less are not aconcern, a guideline for a measurement uncertainty requirement would be 5°F.

In general, it can be assumed that installation and data acquisition will add an additional 1 degreeto the measurement uncertainty. If this were to be used with the “5°F measurement uncertaintyrequirement,” then the temperature measurement sensor accuracies described in Table A-1 wouldhave a 4-degree upper limit for ∆T measurement.

a. Sensor Accuracy

Table A-1(a-c) presents typical measurement uncertainties for RTD and T/C, absolute anddifference, and T/C with special fabrication and selection testing. Theoretically, measurementstrings that include a short section of high temperature T/C wire combined with a long section oflow temperature extension wire (if T > 350oF) have measurement uncertainties that are againabout 40% higher than those listed in Table A-1a for a single (1) T/C absolute temperaturemeasurement. This is because each T/C segment contributes its own error (uncertainty)component. Practice has shown this to be conservative and can be minimized with in-place post-installation testing and normalization. Extension T/C wire is normally used for long lengths ofcable run because of the reduced cost compared to that for high temperature T/C wire.Additional errors associated with T/C’s during extended use are described below Theuncertainties listed in Table A-1 (a-c) for RTDs assume that a 4-wire or 3-wire (wires runtogether from sensor to bridge) configuration is used.

Temperature cycling, (∆T/t) can be monitored (followed) within the limits of the date acquisitionfor deadband, repeatability and resolution.

Table A-1aTemperature Measurement Sensor Accuracies For Thermocouples and RTDs

ThermocoupleUncertainty Method ~600o

~300o (1) (2) RTD

U(A) Absolute 4 o 5o 7o <3o

U(∆,A) Difference(2)(∆) 6.5 o 7o 10o 4.5 o

Differential (∆,A) from two similar but independent absolute (A) measurements suchthat square-root sum of the squares can be applied.

U(∆,A) = √2 * U(A)

(1) Single T/C measurement without extension T/C(2) Single T/C measurement with extension T/C


A-4

Using two T/C absolute measurements to determine the difference does not meet the five degreeaccuracy requirement. Using RTDs, T/C with averaging, special fabrication and selectiontesting, or direct ∆T measurement improve the accuracy of the T/C measurement.

b. Using Averages from Two T/Cs and Direct Temperature Difference ∆T

As shown in Table A-1b, using the average of two measurements improves on the uncertainty. Ifabsolute temperature is not important, the differential temperature between two points can bedetermined more accurately. If the "2" T/Cs are actually fabricated from the same T/C wire thedifferences between their ∆mV/∆T will be small and, if combined for ∆T, there is no need tomeasure (or control) the reference temperature, TR. In general the ∆T must be calculated insoftware if the data acquisition does not include a direct T/C ∆T measurement. Using a singlevalue for the conversion (oF/mV) would result in less than a 0.25oF error for Type K T/Cs.Special consideration (ungrounded junction, isolated differential measurement) allows measuringabsolute and differential temperature directly and simultaneously from the same sensors.

Table A-1bTemperature Measurement Sensor Accuracies For Thermocouples and RTDs

Thermocouple~600o

Method ~300o (1) (2) RTD

U(avg, A) Average (2) 3 o 3.5o 5o 2 o

U(∆,avg) Difference from 2Average

4 o 5o 7o 3 o

U(dir ∆) Difference <3 o 3o 13o 1 o (matched pair)

Average (Avg) from two similar but independent absolute (A) measurements such thatsquare-root sum of the squares can be applied.

U(Avg, A) = U(A)/ √2

Difference (∆) from two average (A) measurements of absolute temperatures.U(∆, Avg) = U(A), where ∆T = TH (Avg) – TL (Avg)

Difference measured directly (dir∆) without measuring absolute temperature.U(dir∆) < U(A)

(1) Single T/C measurement without extension T/C(2) Single T/C measurement with extension T/C

c. Special Fabrication Methods to Improve Accuracy

By utilizing special fabrication and testing, improvements can be made in the uncertainty ofmonitoring temperature gradients from absolute measurements. This is accomplished byspecifying (or fabricating) individual T/Cs from the "same lot" (same spool of T/C wire) andperforming screening tests to guarantee the tighter tolerances. This should be backed up withstringent installation testing and post installation normalization (verification) at elevated


A-5

temperatures under isothermal conditions. Using these fabrication and testing methods canreduce the measurement uncertainty to those shown in Table A-1c.

Table A-1cThermocouple Measurement Sensor Accuracies

Test and "Same Lot"~300o ~600o

U(A) 3 o 4 o Absolute temperature

U(∆,A) 3 o 4 o Difference from two absoluteT

U(avg, A) 2 o 3 o Average of 2 absolute T

U(∆,avg) 2.5 o 3 o Difference of absolute –average

U(dir ∆) 2 o 3 o Direct difference temperature

A.1.4 Installation

Successful RTD and T/C thermal fatigue monitoring experience suggests that the sensors beeither cemented, bonded, spot welded to the pipe or held in place with a constant torque "clamp-on" band. It is recommended that all sensors fastened to the RCS pressure boundary be affixedwith circumferential stainless steel bands utilizing a constant torque device to maintain aconstant contact pressure and accommodate thermal expansion and contraction of the piping.These bands provide a chemically benign method of securing the sensors against the outside pipediameter while permitting installation of covering insulation to assure that the entire sensor massreaches a thermal equilibrium with the surface. They can easily be handled and installed inaccordance with cleanliness procedures to ensure no contamination of the pipe surfaces. Eachsensor band assembly weighs less than one pound and contributes a negligible load on the line.The entire assembly, thermocouples and band, can be pre-fabricated and tested prior toinstallation to minimize time required inside of containment (see Figure A-1).

Installation acceptance test, comparing pre to post readings, should guarantee the integrity of thesensor including:

a. Visual inspections and labeling

b. Documented installation location and position

c. Loop resistance (individual and string)

d. Loop points check using heated junction

e. Integrated system (through the Data Acquisition System (DAS)) patch verified withdisconnect/connect

f. Failed sensor (open junctions) detection in DAS


A-6

Following installation, it is very important that T/C’s fastened to the outer pipe wall are insulatedfrom the ambient to ensure only pipe temperature is being detected. This includes isolation fromthe room temperature as well as assuring that the T/C is protected from “drafts” and air currentsthat might “cool” the sensing location.

A.2 Resistance Temperature Detectors (RTDs)

In general, an RTD is more accurate than a T/C and must be used if tolerances less than 3oF areneeded. RTDs are passive devices where the actual measurement is resistance in a bridge circuit.Temperature is determined from a resistance (Ω) versus temperature (T) correlationaccomplished either in data acquisition hardware or in software. An RTD is a "point"measurement with the measured temperature determined from the actual temperature of thesensor material. Normally a platinum sensor is used, but nickel or copper could be selected forthis application. The most common RTD is a 100 ohm platinum sensor with an alpha coefficientof 0.00385 Ω/Ω/°C. Different types of RTDs have different alpha coefficients and they must bematched in instrumentation for proper conversion to temperature. In all cases a 3 or 4 wirebridge configuration is recommended to eliminate an offset introduced from leadwire resistance.If a two wire approach is utilized, the error in absolute measurement can be quantified andcorrected for in the software. Thus, the error introduced in the determination of the differentialtemperature can be less than for an absolute temperature measurement.

Temperature is normally calculated from measured resistance in the data acquisition systemusing the approximation formula (for platinum RTD):

RT = Ro * (1 + AT) where A = 0.00385. The exact formula would be:

RT = Ro * (1 + At + BT2) where A = 0.00300784 and B = 0.5784 * 10-6

For the range of temperatures for the thermal fatigue monitor application, the results differinsignificantly (<0.01%). The uncertainties associated with the RTD temperature measurementare due to variations in material, resistance to temperature conversion, self-heating, andinstallation.

A.3 Thermocouples

Refer to Figure A-2 for an illustration of T/C setups for absolute and difference measurements.

A.3.1 Thermocouple Types

Thermocouples can be made with any combination of two dissimilar materials. ISA recognizestwelve thermocouple types. Eight of the 12 have letter designations including Type J, Type K,Type N, and Type T, which are candidates for this application.

The most common determining factor for choosing thermocouple type is the temperature rangeof its intended application. Type J is suitable for a temperature range up to 1,400oF, Type K up


A-7

to 2,300oF, Type T up to 700oF, and Type N up to 2100oF. Any of these types are adequate forthe thermal monitoring applications.

Type T is copper-constantan T/C with copper wire having a positive coefficient and constantannegative coefficient. It is only recommended in mildly oxidizing environment and lowtemperatures (<700oF.)

Type J is iron-constantan T/C with iron wire having a positive coefficient and constantan anegative coefficient. It is not recommended for an oxidizing environment.

Type K is chromel-alumel with chromel wire having a positive coefficient and alumel having anegative coefficient. This is recommended for use in an oxidizing environment and therefore isbest suited for in-containment applications.

Type N is similar to Type K but it has been designed to minimize some of the instabilities in theconventional T/C combination. Changes in the alloy content have reduced thermal cyclinghysteresis and a higher silicon content in the positive element improves oxidation resistance.

A.3.2 T/C Measurement Uncertainty Discussion

To better understand techniques that can improve the measurement uncertainty of T/Cs, a shortdiscussion on the principle is helpful.

T/Cs are manufactured using materials and processes to controlled specifications that guaranteethat the product will be within standard tolerances for accuracy. For example, Type Kthermocouple wire shall meet the standard limits of error, as given in ANSI MC96.1:

+ 4oF or .75% of the measured temperature, which ever is greater.

This allows an error of + 4oF up to a temperature of 533oF, increasing linearly to +5.25oF at700oF.

This is normally referred to as "Full DIN” (referring to the original German Industry Standard)tolerance. For added cost it is possible to specify and purchase "half DIN" tolerance T/Cs.

These “as-received” tolerances and thermocouples can experience additional inaccuracies duringuse. Thermocouple types E, J, and K show inherent thermoelectric instability related to time-and/or temperature-dependent instabilities in several of their physical, chemical, nuclear,structural, and electronic properties.

There are three principal characteristic types and causes of thermoelectric instability in the mostcommonly used thermoelement materials:

1. A gradual and generally cumulative time-dependent drift in thermal electromotive force(EMF) on long exposure at elevated temperatures due to compositional changes caused byoxidation and to neutron irradiation, which can produce transmutation in nuclear reactorenvironments.


A-8

2. A short-term cyclic change in thermal EMF on heating thought to be due to some form ofstructural change.

3. A time-independent perturbation in thermal EMF in specific temperature ranges.

Unlike an RTD, with a T/C the temperature signal is not induced at the measurement point(junctions) but rather through temperature gradients along the length of the wires. Figure A-2 isprovided to help with this explanation. For an absolute measurement, the T/C junction providesa common temperature and voltage connection (contact, short) at the measurement point. Withchanging temperature an electromotive force is generated along the lengths of wire, the voltagegenerated differing for dissimilar materials (wires). After some length of wire at differenttemperatures, this difference can be measured as a mV signal proportional to the temperaturechange. A reference junction is provided to give a reference point (normally 0oC = 32oF) fromwhich to determine (calculate) the absolute temperature at the junction (either by formula orlook-up table). The uncertainties are in the mV/∆T for the wires, the accuracy of referencetemperature (TR) and the calculations.

With special fabrication consideration and selection testing it is also possible to reduce themeasurement uncertainty.

A.3.3 Special Fabrication Methods

If absolute temperature is not important, the differential temperature between two points can bedetermined more accurately. If the "2" T/Cs are actually fabricated from the same T/C wire thedifferences between their ∆mV/∆T will be small and, if combined for ∆T (see Figure A-2), thereis no need to measure (or control) TR. In general the ∆T must be calculated in the software if thedata acquisition does not include a direct T/C ∆T measurement.

In a similar fashion, improvements can be made in the uncertainty of monitoring temperaturegradients from absolute measurements. This is accomplished by specifying (or fabricating)individual T/Cs from the "same lot" (same spool of T/C wire) and performing screening tests toguarantee the tighter tolerances. This should be backed up with stringent installation testing andpost installation normalization (verification) at elevated temperatures under isothermalconditions.

A.3.4 Insulation

Material properties for the in-containment cables are always a concern with most plants havingrestrictions over the commonly available Teflon and PVC materials. A recommended practice isfor the thermocouples attached to the pipe to have stainless steel sheathing for high temperature(>300oF) T/C with fiberglass insulation and the low temperature T/C and extension cables madewith insulation of Tefzel. The high temperature T/C attached to the bands should have an overallfiberglass braid jacket insulation and the individual wires should also have fiberglass insulation.Low temperature T/Cs can be fabricated directly using “extension cable” T/C wire.


A-9

The Tefzel insulation (extensions cable jacket and wires) has:

1. Continuous temperature rating above 300oF.

2. Passes IEEE 383 flame test (70,000 BTU) and UL 83 (no afterburn).

3. Flame retardant and non-propagating in fire conditions.

4. Excellent chemical and radiation resistance.

5. Superior cut-through resistance.

Table A-2 includes more descriptive information on Tefzel as supplied by the manufacturer(Product Information from DuPont).

Table A-2Characteristics of Tefzel (280), a Fluoropolymer Resin

1. Description

Combining mechanical strength and toughness with chemical resistance, Tefzel fluoropolymerresins are widely used to make compact cable constructions that provide long, reliable service -especially in hot, corrosive environments.

Tefzel offers excellent electrical properties for demanding wire and cable applications. It resistsheat aging and also offers high resistance to aggressive chemicals, making it ideal forchemical/petrochemical plants, paper mills, and other facilities with hostile service environments.Relatively radiation resistant, Tefzel meets the requirements of IEEE-383 and is approved for usein nuclear power plants.

The physical and electrical properties of Tefzel permit more compact cable constructions forready connection with today's smaller electronic components. In fact, cables insulted with Tefzelcan be smaller and lighter, for a given ampacity, than almost any other insulting material offeringeconomy of operating space and value.

Tefzel also provides for trouble-free installation. Its toughness delivers excellent cut-through,abrasion, and crush resistance. Its flexibility, compactness, and low coefficient of friction makecables each to pull, minimizing the number of wires damages during installation.

Cables insulated and jacketed with Tefzel also have a low flame spread rating, passing the large-scale IEEE-383 flammability tests.

2. Applications

For high-temperature wiring with mechanical strength, stress crack resistance, and chemicalresistance, Tefzel 280 is the insulation of choice. Rated by UL at 150oC (302oF), it is widely usedfor insulating and jacketing heater cables and automotive wiring and for other heavy-wallapplications in which temperatures up to 200oC (392oF) are experienced for short periods orrepeated mechanical stress at 150oC is anticipated. It is also ideal for oil well logging cables.


A-10

Figure A-1Recommended Temperature Sensor Installation Method


A-11

Figure A-2T/C Temperature Measurement Princ iples

B-1

B DISPLACEMENT METHOD INSTALLATION AND COSTCOMPARISON

B.1 Displacement Sensor Types

Six means of sensing displacement were reviewed. Three are recommended and three were notfound to be suitable for attached piping applications. The recommended means ofmonitoring/measuring piping displacement during heatup, operation and cooldown are:

1. Cable-Extension Position Transducers (“String Pots”) (sensor is an extension wire connectedto a precision potentiometer):

A representative String Pot sensor has a 5” Stroke, 0.024” dia. measuring cable, top exit,2mV/V bridge and 6 pin metal MS3106E-145-6P connector on the enclosure. The effectivestroke length is ± 2.5”. The sensor requires a power supply, which can be a simple 12-40VDC unregulated power supply.

2. Linear Variable Differential Transformer (LVDT) Position Transducers:

A representative LVDT has a 3” Stroke, No. 8-32 threaded core, Hermetically sealed case,glass sealed MS type connector. Additionally, LVDTs require a signal conditioner tointerface with the Data Acquisition System. Normally a multi-channel unit would be usedwith a large number of sensors.

3. Conductive-Plastic Resistance and Collector Track Position Transducer:

A sample model has a 3” stroke with an IP65 enclosure (similar to NEMA Type 13). Thesensor requires a power supply, which can be a simple 12-40V DC unregulated powersupply.

The following three alternative methods of monitoring/measuring piping displacement duringheatup, operation and cooldown were reviewed. These alternative methods do not appear tooffer any benefit and are simply not suitable for this type of task.

4. Inductive and Capacitive Proximity Sensors

A review of existing and a search for new applications in this broad area of sensingtechnology did not result in a useable alternative method. These sensors have pickup rangesup to 40 mm (1 ½ “) and operate between -8°F and 158°F. Their enclosures are rated for IEC

Displacement Method Installation and Cost Comparison

B-2

IP 67 (water immersion). These may be useful for an application that requires indication ofpossible catastrophic line growth or movement.

Also as they are digital (single pulse), and quite accurate, these sensors could be appliedwith cable extension technology for unique displacement measurements.

5. Ultrasonic Sensors

This is a relatively new application of sensor technology. A representative has a singletransducer that functions as both transmitter and receiver. Its characteristics are:

Ranges available are from 2 to 40 inchesSonic cone is 6°Output of up to 6 transducers is easily synchronizedNormal sensor temperature range is between -13°F and 158°FTheir enclosures are rated for IEC IP 67 (water immersion)

While this model operates as a proximity sensor, the ability to accurately sense at a distanceof up to 40 inches may be beneficial in certain applications.

6. Encoders

A review of existing and a search for new applications in this broad area of sensingtechnology did not result in a useable alternative method.

B.2 Measurement Accuracy Comparison

Previous work for similar applications (to thermal fatigue monitoring) by FTI determined that anaccuracy/resolution requirement for displacement measurement was 0.1-inch. Test results forboth LVDTs and Position Transducers (PTs) showed resolution capabilities of 0.06 inch and0.04 inch, respectively. Achieving these accuracies in practice requires controlled installationand calibration (normalization) methods.

For information purposes, conclusions from the testing and evaluation of the above displacementtransducers are:

“From the thorough testing and evaluations of the two types of displacement transducersselected to measure movement of the surge line, it is evident that both the LVDTs and theString Pot position indicators (PTs) are well suited for the surge line test application. Thequalification results demonstrate that these transducers exhibit desirable, if notexceptional, operating and performance characteristics when subjected to the range ofexpected surge line and Pressurizer room ambient temperatures. It is concluded,therefore, that the LVDTs and PTs would both provide reliable engineering informationto support and enhance the understanding of thermal stratification and its effects on thesurge line.”


B-3

B.3 Installation

Installation and cost are a deciding factor with displacement measurements. Options 3 through 6discussed above either do not meet required environments or are more costly and difficult toinstall than PTs or LVDTs. “String pots” are less expensive and much easier to install andcalibrate (normalize).

It is extremely important to document the “as-installed” conditions for displacement sensors toallow interpretation of the data. This includes distance to the pipe connection point from a fixedreference, and direction of the attached wire (axial, longitude, and angle).

1. String Pot or Position Transducer (PT)

String Pots or Position Transducers (PT) are straightforward in their installation:

• PT enclosure bases have mounting provisions,

• PTs do not require perfect parallel alignment of the potentiometer spool wire for satisfactoryoperation

• PTs are relatively simple to set up (illustrated in Figure B-1). Resolution can be verifiedthrough testing and agreed to be within manufacturers specs. The actual calibration of theinstrument takes place in the field when the unit(s) is “zeroed” after installation.

Other advantages include reliable operation, proven bridge circuit, and one easily replaceablepower supply for multiple PTs. The environmental influences on the measurements have beenshown to be minimal (ambient temperature variations affecting the potentiometer and vibrationaffecting the sensor and wire).

The user can select either voltage or current as the output signal appropriate for the application.

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B-4

Representative String Pot performance is:

Accuracy: 0 to 5” Range ± 0.25% full strokeResolution: Essentially infiniteRepeatability: Greater of ± 0.001 inches or 0.02% full stroke

Representative String Pot Environmental characteristics are:

Operating Temperature: -40° F to +200°FHumidity: 100% RH at 90°FVibration: up to 10 G’s to 2000 HzEnclosure: NEMA 1

2. Linear Variable Differential Transformer (LVDT)

• LVDTs are also straightforward in their installation:

• LVDT enclosures can be purchased with a variety of mounting provisions.

• While LVDTs do not require perfect alignment of core for satisfactory operation, theiralignment is more critical then that for String Pots.

• Each LVDT requires a dedicated signal conditioning module

The LVDT in itself is simple and has many commendable features, such as:

Frictionless measurement and Infinite Mechanical Life

Infinite Resolution and Null Repeatability

Cross-Axis Rejection; i.e., the LVDT can also be used in application where the core does notmove in an exact straight line.

Input / Output Isolation – the LVDT is a transformer

Environmental Compatibility – LVDT sensors can be designed to operate in:

Temperatures ranging from cryogenic to 1000°FRadiation tolerance up to 105 RadsNeutron flux up to 3x1020 NVT total integrated fluxPressure up to 3,000 psi

LVDT signal conditioning electronics have the same environmental limitations as associatedwith the DAS hardware.

However, while the LVDT itself is simple, Figure B-2 depicts the additional excitation andsignal conditioning components required to operate an LVDT in the field.


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Figure B-3 depicts a possible arrangement of LVDTs used to monitor components incontainment. The signal conditioning modules (ATA 2001) could be placed outside thecontainment wall also, but would require a much greater cabling effort.

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Figure B-3LVDT Data & Supply Voltage Installation Requirements

DC-DC LVDT Specifications are:

Input Voltage: ±15VDC (nominal), ± 25 maStroke Range: ± 3.0”

Operating Temperature Range: 32° to 160°F (0°C to 70°C)Null Voltage: 0 VDCRipple: Less than 25 mV rmsLinearity 0.25% full rangeStability 0.125% full scaleTemperature –Coefficient of Scale Factor: 0.04%/°F (0.08%/°C)


B-6

Shock Survival: 250 g for 11 milliseconds half sineVibration Tolerance: 10 g up to 2 kHzHousing: ANSI 400 series Stainless Steel

AC-AC Long Stroke LVDT

Input Voltage: 1-7V RMS @Stroke Range: ± 3.0”

Operating Temperature Range: +32°F to 158°F (0°C to 70°C)Null Voltage: 0 VDCRipple: Less than 25 mV rmsLinearity 0.25% full rangeStability 0.125% full scaleTemperature –Coefficient of Scale Factor: 0.04%/°F (0.08%/°C)Shock Survival: 250 g for 11 milliseconds half sineVibration Tolerance: 10 g up to 2 kHzHousing: ANSI 400 series Stainless Steel

3. Position Transducer (Conductive-Plastic Resistance and Collector Track)

A Conductive-Plastic Track Position Transducer is mounted the same as a LVDT and is operatedthe same as a string pot. This device utilizes conductive plastic resistive plates in lieu of aprecision potentiometer (as used in the string pot) or variable transformer (as used in the LVDT).This system appears to be accurate and relatively low in cost.

Representative Specifications for Position Transducers with a 3 in. Stroke are:

Input Voltage: Max 42V DCStroke Range: ± 3.0”Operating Temperature Range: -25°F to 212°F (-32°C to 100°C)Linearity 0.1% full rangeRepeatability: <0.01 mmShock: 50 g for 11 milliseconds half sineVibration: 0.75 mm – 20 g, 5…2 kHzHousing: Anodized aluminum

Note: These items provide a PT or LVDT in the field that will provide a measurement signal toa specialized Data Acquisition System input.

C-1

C THERMAL FATIGUE MONITORING SURVEY SUMMARY

Questionnaires, prepared to obtain information about nuclear plant's experience with monitoringfor thermal fatigue problems, were sent primarily to plants that had responded to an earlier EPRIquestionnaire for Thermal Stratification and Cycling. FTI’s monitoring experience is alsoincluded.

The experiences for eleven plants, including three supplied by FTI, are provided in Tables C-1,C-2 and C-3. The first column of each table represents the questionnaire that was sent to theparticipants. A summary of responses is provided in the following paragraphs.

Thermal Fatigue Monitoring Survey Summary

C-2

Table C-1Plant Survey Summary

Utility: Entergy Southern Nuclear OperatingCompany

Carolina Power and Light Virginia Power

Plant: ANO Farley Harris North Anna/SurryUnits: 1 (BW) 1 & 2 (W) 1 (W) 1 & 2 (for both sites) (W)Contact person: Bracy Means Mike Belford Ray Lebitz Leslie (Les) SpainPhone Number: 501-858-5532 (205)992-5783 919-362-2042 804-273-2602E-mail: [email protected] [email protected] [email protected] [email protected] description ofthermal fatigue monitoringproblem(s) addressed:

Pzr Spray (normal andauxiliary), Decay Heat Dropleg, Cold Leg Drains, SurgeLine

Farley-2 Safety Injection (SI)line cracking · 3 cold leg, 3 hotleg, and 2 RHR lines, thenormal and alternate chargingline, and the aux Pressurizerspray line

Safety Injection andCharging

High pressure safety injection

Purpose of monitoring: Monitor locations susceptibleto thermal cycling.

Monitor locations susceptible tothermal cycling.Monitor locations susceptible tovalve leakage.In response to 88-08.

Monitor locations susceptibleto thermal cycling.

Monitor locations susceptibleto thermal cycling.Monitor locations susceptibleto valve leakage.Look for stratification, top tobottom, and whether it moveswith time; i.e., determine theamount of stratification, andwhether it cycles over time.

General description ofmonitoring system at thisplant:

Not using installed plantequipment; for 1" drain linesused 2 T/Cs strapped to pipe180 deg apart; For Pzr spray(normal) had 5 or more T/Csstrapped to pipe at severallocations for a temperatureprofile; for drains and sprayline, used a data loggerconnected to a PC. Forother lines, used RTDscemented to pipe with leadsfed through a penetration sothey could be monitored atpower.

See above for locations. RTDswere initially installed on bothsides of the first block valve offthe RCS loop. The RTDs onthe downstream side of eachvalve were removed fromservice because of reliabilityproblems and because theywere not required by IEB 88-08.Data is collected by dataloggerand sent to a plant computerthat stores selected data.Periodic reports are generatedoff an Excel spreadsheet. Anydata which does not meet the

Thermocouples are attachedto top/bottom of charging/SIpipe. Recently replaced themirror insulation with blankettype to allow for betterinstallation of t/c. Recentlychanged from Gordonthermocouples mountedperpendicular to the pipewhich was difficult tomaintain a good reading.

Thermocouples mounteddownstream (of valve?); datalogger linked to Digitrack 360drive; provides a floppy diskwith data file retrievable byLotus 123


C-3



Plant: ANO Farley Harris North Anna/SurryIEB 88-08 criteria is evaluatedby Westinghouse.

Data acquisition hardw are: Wang and Omega dataloggers (only bought Omegabecause Wang was in use).

Fluke 2280 datalogger HP 34970A Data acquisitionlogger

Beckman Industrial (BI) datalogger and BI Digitrack 360drive

Data acquisition softw are:Please comment onmonitoring programexperience for this plant:

Strengths: Data is reviewed bi-weekly bysite system engineers

System works most of thetime; confident would detectstratification and cycling

Weaknesses/problems: RTDs were difficult to troubleshoot; long run for lead wiresmade isolation of problemsdifficult.

RTDs and lead wire subject todamage during ISI, insulation,etc

Still encounter problems ifpeople step on insulation.

T/Cs can come loose;connections can be madeincorrectly (top reading isbottom temp); intended astemporary installation

Limitations encountered: Lack of redundancy when anRTD fails

What were the costconsiderations?

Projects driven by availabilityof manpower

None for the original installationbut funding for reliabilityimprovements has been harderto come by

Cost of analyzing erroneousdata compared to installationof new curved t/c

Number of locations: 3 for Pzr Spray 11 8 10 (typical, all four plants)No. of points/location: 5 or more T/Cs 2 2 2/top and bottom;

4/redundant top and bottomSensor type(s): Experience with RTDs and

T/Cs; would use T/Cs, ifmore monitoring needed.Got better results with T/Cs.

RTDs Weed type E curved radius Thermocouples

Monitoring locations: See above Charging, Alt Charging,Safety Injection (6)

See General Description

Sensor locations: Circumferentially spaced.Top/bottom of pipe.Horizontally spaced.

Top/bottom of pipe. Top/bottom of pipe. Top/bottom of pipe.Occasional on side of pipe at90 deg.


C-4



Plant: ANO Farley Harris North Anna/SurryInstallation techniques: RTDs cemented to pipe;

T/Cs mounted with jig oftubes and pipe clampstrapped to pipe

The RTDs are banded to thepipe with stainless steel bands.

Stainless steel pipe clamps Stainless steel pipe clampswith attached tubes;thermocouples are insertedinto tubes; system has beenin place since '89-'90;

Monitoring frequency:Continuous (constant),rates:

30 sec samples for some(spray), 5 min samples forsome

Data is collected every minute

Triggered, initiated on:Periodic, when: Following power ascension

and every 6 monthsquarterly and during heat up.

Description: Log data @ 10 sec for 10min, then @ 10 min for 24hours. Connections aremade outside thecontainment (in the "cablevault").

Data transmission: Proprietary for data logger. Serial.Distribution in plant and offsite.

Data Storage: Circular or floating buffer.Proprietary format data file.ASCII, CSV (e.g., Excel).

Circular or floating buffer.ASCII, CSV (e.g., Excel).

Continuous monitoring withexception reporting.ASCII, CSV (e.g., Excel).

Reporting Format: Periodic reports.Problems encountered: On one occasion, lost use of

PC due to damaged comm.cable; data logger producedhard copy that was manuallyentered into Excel.

Primary problem has been thatthe RTDs were initially installedas temporary and thus are notas rugged as a permanent plantinstrumentation.

"Funny data" – i.e.,thermocouples wired wrong,or bad thermocouple

Goals (wishes) not met: Plant plans to make the RTDinstallations permanent toincrease the reliability of thereadings

Be able to remove equipmentfrom plant (it is cheaper toleave equipment in place andmonitor every 18 months thanto do regular inspections).


C-5



Plant: ANO Farley Harris North Anna/SurryRecommendations: Use T/Cs instead of RTDs; If

insulated, replace insulationcorrectly – loose or improperinsulation will have anoticeable effect on datareadings

If doing installation again,would look for more robustequipment and more reliableway to mount thermocouples.

Future plans: Discontinue monitoring. Continue monitoringindefinitely.

Continue monitoringindefinitely.

Continue monitoringindefinitely.

Basis for discontinuing: Driven by the part of normaloperation that piping iscritical to operation; DHmonitored through out cycle;Drain and spray lines takenout before operating plant.

NA NA NA


C-6


Utility: PG&E New York Power Auth WCNOC Ameren UEPlant: Diablo Canyon (DCPP) Indian Point 3 Wolf Creek CallawayUnits: 1 and 2 (W) 1 (W) 1 (W) 1 (W)Contact person: Suresh G. Khatri Ahmet Unsal Maurice (Mo) Dingler Richard LutzPhone Number: (805)545-4169 (914)287-3435 (316)364-4127 (573)676-8536E-mail: [email protected] [email protected] [email protected] [email protected] description ofthermal fatigue monitoringproblem(s) addressed:

DCPP has not instrumentedany lines for unisolable leaks.Please note that we hadmeasured the temperature ofthe pressurizer surge line (topand bottom of the pipe).

2” auxiliary pressurizer sprayand 4” pressurizer sprayconnection

Pressurizer auxiliary spray line N/A. Callaway Plantdoes not currently havespecial instrumentationinstalled to monitorleakage or thermalcycling. See below fordiscussion of EPRI/SIAFatiguePro fatiguemonitoring system usedto obtain global data atCallaway Plant toaddress long term RCSthermal fatigue issues.

Purpose of monitoring: Provide means for ensuringthat pressure upstream fromblock valves which might leakis monitored and does notexceed RCS pressure.




A new isolation valve andpressure indicator (PI 155)have been installed in the BITbypass line.

RTDs were installed at theinterface of two lines (line #’s61 & 64)

RTDs installed on the pipe torecord the temperature of thepipe, which would allow thedetermination of valveleakage.

Callaway has procuredEPRI/SIA FatigueProfatigue monitoringsoftware. This softwarehas been saving dataon a triggered basis toallow fatigue analysisassociated with planttransients. Usespreviously existing plantinstrumentation and isnot designed to analyzevalve leakage, TP etc.


C-7

Utility: PG&E New York Power Auth WCNOC Ameren UEPlant: Diablo Canyon (DCPP) Indian Point 3 Wolf Creek CallawayUnits: 1 and 2 (W) 1 (W) 1 (W) 1 (W)Data acquisition hardw are: Data LoggerData acquisition softw are: Records temperatures FatiguePro software

installed in 1995 tosave plant transientdata

Please comment onmonitoring programexperience for this plant:

Strengths: Records a temperature everyminute and easy to maintain

Saving plant data forfuture analysis

Weaknesses/problems: data has to be downloadedevery 6 months

Future analysis may betime consuming due tobad data, etc.

Limitations encountered: Not designed to monitorvalve leakage orturbulent penetrationetc.

What were the costconsiderations?

installed in 1993 data nolonger available

Number of locations: 1 1 3No. of points/location: 1 2/location 180 o from each

otherSensor type(s): Pressure indicator RTDs Existing plant

instrumentation fortemperature, flow,pressure, etc.

Monitoring locations: Charging piping - BIT bypassline

Piping pressurizer aux spray line - 2 “in size

Bounding locationschosen to cover RCSnozzles & pipe.

Sensor locations: Single point location. Top/bottom of pipe. Circumferentially spaced.Installation techniques: Pressure indicator with

isolation valveN/A. Existing plantinstruments used forFatiguePro


C-8

Utility: PG&E New York Power Auth WCNOC Ameren UEPlant: Diablo Canyon (DCPP) Indian Point 3 Wolf Creek CallawayUnits: 1 and 2 (W) 1 (W) 1 (W) 1 (W)Monitoring frequency: Routine weekly checks. Periodic. Every minute. Temperature probes

used in past to identifyspecific RCS out-leakage locations.

Data transmission:Data Storage: Constant Logging.Reporting Format: Alarm.Problems encountered: NoneGoals (wishes) not met:Recommendations: Callaway plans to

continue globalfatigue/transientmonitoring (probably toend of plant life) usingFatiguePro software (orequivalent). Noinstalled localmonitoring at this time.

Future plans: Continue monitoringindefinitely.

Discontinue monitoring. Continue monitoringindefinitely.

Basis for discontinuing: NA Data collected showed thatthere was no thermalstratification.

NA


C-9


Utility: Duke Power Duke Power Duke PowerPlant: Oconee Oconee OconeeUnits: 2 1 and 3 1Contact person: Fred Custer Fred Custer Tim BrownPhone Number: (864) 885-3465 (864) 885-3465 (864) 885-3952E-mail:General description ofthermal fatigue monitoringproblem(s) addressed:

Obtain High pressureinjection line temperatureprofile to analyze for possibletemperature stratification

Obtain High pressure injectionline temperature profile toanalyze for possibletemperature stratification

Obtain temperature profile ofpressurizer valves

Purpose of monitoring: Monitor locations susceptibleto thermal cycling.

Monitor locations susceptible tothermal cycling.


T/Cs terminated to inputcards in containment;connected by single RS-422cable through penetration todata acquisition front end andPC in cable spreading room.PC logs data that is manuallydownloaded to a Zip driveand transferred to another PCfor analysis.

T/Cs terminated to input cardsin containment; connected bysingle Ethernet cable throughpenetration to PC in cablespreading room. PC logs datathat is manually downloaded toa Zip drive and transferred toanother PC for analysis.

T/Cs were added to existingNetDAQ system installed forHPI line monitoring; T/Csterminated to input cards incontainment; connected bysingle Ethernet cable throughpenetration to PC in cablespreading room. PC logsdata that is manuallydownloaded to a Zip driveand transferred to another PCfor analysis.

Data acquisition hardw are: Fluke Helios extender chassisin containment receivingabout 80 T/C inputs; FlukeHelios data acquisition unitand PC in cable spreadingroom for data logging.

Two Fluke NetDAQ units and anetwork hub custom installed ina single cabinet in containment.

Expanded input capability ofexisting system by adding athird Fluke NetDAQ unit tocabinet in containment.

Data acquisition softw are: LabTech notebook Fluke NetDAQ Logger softwarefor data acquisition; FlukeTrend Link software for viewingthe data.

Fluke NetDAQ Loggersoftware for data acquisition;Fluke Trend Link software forviewing the data.


C-10

Utility: Duke Power Duke Power Duke PowerPlant: Oconee Oconee OconeeUnits: 2 1 and 3 1Please comment onmonitoring programexperience for this plant:

Strengths: A reliable system; has donecontinuous multi-yearmonitoring at five other sites.

A reliable system; has donecontinuous multi-yearmonitoring.

Additional T/Cs were easilyadded to existing system; areliable system; has donemulti-year monitoring

Weaknesses/problems: Product is no longersupported; only chassisextender meets in-containment requirements;data acquisition main framemust be located outside ofcontainment.

Limitations encountered:What were the costconsiderations?Number of locations: 7 to 8, for each of four lines 4 to 5, for each of four lines for

Unit 1; for each of two lines forUnit 3

3 bands; on valve upper andlower flanges and centerbody

No. of points/location: 1 to 4 1 to 2 2 T/Cs 180° apartSensor type(s): T/Cs fabricated and tested by

FTI.T/Cs fabricated and tested byFTI.

T/Cs fabricated and tested byFTI.

Monitoring locations: Four HPI lines Four HPI lines for Unit 1; twoHPI lines for Unit 3

Sensor locations:Single point location Circumferentially spaced.

Top/bottom of pipe.Circumferentially spaced.Top/bottom of pipe

Across valves.

Installation techniques: T/Cs spot welded to constanttorque stainless steel clamps(bands)

T/Cs spot welded to constanttorque stainless steel clamps(bands)

T/Cs spot welded to constanttorque stainless steel clamps(bands)

Monitoring frequency: Once a minute. Once a minute. Once a minute.Data transmission: Serial RS-422 Network NetworkData Storage: Constant logging Constant logging Constant loggingReporting Format: Demand reports Demand reports Demand reports


C-11

Utility: Duke Power Duke Power Duke PowerPlant: Oconee Oconee OconeeUnits: 2 1 and 3 1Problems encountered: (potential) occasional bad

T/Cs avoided by having spareT/C bands available; locationof data acquisition PC (incable spreading room) notreadily accessible; makesdaily viewing of data unlikely;any system alarms areunnoticed until next visit toPC to get data.

(potential) occasional bad T/Csavoided by having spare T/Cbands available; location ofdata acquisition PC (in cablespreading room) not readilyaccessible; makes daily viewingof data unlikely; any systemalarms are unnoticed until nextvisit to PC to get data.

(potential) occasional badT/Cs avoided by having spareT/C bands available; locationof data acquisition PC (incable spreading room) notreadily accessible; makesdaily viewing of data unlikely;any system alarms areunnoticed until next visit toPC to get data.

Goals (wishes) not met:Recommendations: Coordinate reinstallation of

insulation with craft andobserve, if possible, to avoidpinching or cutting T/C leadswith insulation; check all T/Csfor good signals afterinsulation is reinstalled.

Coordinate reinstallation ofinsulation with craft andobserve, if possible, to avoidpinching or cutting T/C leadswith insulation; check all T/Csfor good signals after insulationis reinstalled.

Coordinate reinstallation ofinsulation with craft andobserve, if possible, to avoidpinching or cutting T/C leadswith insulation; check all T/Csfor good signals afterinsulation is reinstalled.

Future plans:

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EPRI creates science and technology solutions forthe global energy and energy services industry.U.S. electric utilities established the Electric PowerResearch Institute in 1973 as a nonprofit researchconsortium for the benefit of utility members, theircustomers, and society. Now known simply as EPRI,the company provides a wide range of innovativeproducts and services to more than 1000 energy-related organizations in 40 countries. EPRI’smultidisciplinary team of scientists and engineersdraws on a worldwide network of technical andbusiness expertise to help solve today’s toughestenergy and environmental problems.

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