ML17352B019
| ML17352B019 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 12/31/1994 |
| From: | Bhowmick D, Petsche J, Prager D WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML17352B017 | List: |
| References | |
| WCAP-14238, NUDOCS 9502080168 | |
| Download: ML17352B019 (82) | |
Text
WESTINGHOUSE NON-PROPRIETARY CLASS 3 0
WCAP-14238 TECHNICALJUSTIFICATION FOR ELIMINATING LARGE PRIMARY LOOP PIPE RUPTURE AS THE STRUCTURAL DESIGN BASIS FOR THE TURKEY POINT UNITS 3 AND 4 NUCLEAR POWER PLANTS DECEMBER 1994 D. C. Bhowmick J. F. Petsche VERIFIED:
D. E. Prager APPROVED:
r 5 S. A. Swamy Structural Mechanics Technology Work Performed Under Shop Order FYNP-950 WESTINGHOUSE ELECTRIC CORPORATION Nuclear Technology Division P. O. Box 355 Pittsburgh, Pennsylvania 15230-355 1994 Westinghouse Electric Corporation AllRights Reserved m%1574-1w.wpf:Ib/122094 9502080ih8 950202 PDR ADOCK.05000250 P
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Section Title TABLE OF CONTENTS
~Pa e
EXECUTIVE
SUMMARY
1.0 INTRODUCTION
1.1 Purpose 1.2 Background Information 1.3 Scope and Objectives 1.4 References 1 1-2 1-3 2.0 OPERATION AND STABILITYOF THE REACTOR COOLANT SYSTEM 2.1 Stress Corrosion Cracking 2.2 Water Hammer 2.3 Low Cycle and High Cycle Fatigue 2.4 References 2-1 2-1 2-2 2-3 2-3 3.0 PIPE GEOMETRY AND LOADING 3.1 Introduction to Methodology 3.2 Calculation of Loads and Stresses 3.3 Loads for Leak Rate Evaluation 3.4 Load Combination for Crack Stability Analyses 3.5 References 3-1 3-1 3-2 3-3 3-3 3-4 4.0 MATERIALCHARACTERIZATION 4.1 Primary Loop Pipe and Fittings Materials 4.2 Tensile Properties 4.3 Fracture Toughness Properties 4.4 References 4-1 4-1 4-1 4-2 4-3 m:51574-1w.wpf: 1b/122094 lv
WESTINGHOUSE NON-PROPRIETARY CLASS 3 TABLE OF CONTENTS Section Title
~Pa e 5.0 CRITICALLOCATIONS AND EVALUATIONCRlTERIA 5-1 5.1 Critical Locations 5-1 5.2 Fracture Criteria 5-1 6.0 LEAKRATE PREDICTIONS 6.1 Introduction 6.2 General Considerations 6.3 Calculation Method 6.4 Leak Rate Calculations 6.5 References 6-1 6-1 6-1 6-1 6-2 6-3 7.0 FRACTURE'MECHANICS EVALUATION 7.1 Local Failure Mechanism 7.2 Global Failure Mechanism 7.3 Results of Crack Stability Evaluation 7.4 References 7-1 7-1 7-2 7-3 7-4 8.0 FATIGUE CRACK GROWTH ANALYSIS 8.1 References 8-1 8-2
9.0 ASSESSMENT
OF MARGINS 9-1
10.0 CONCLUSION
S 10-1 m:41574w.wyf:1b/122794
WESTINGHOUSE NON-PROPRIETARY CLASS 3 TABLE OF CONTENTS Section Title
~Pa e APPENDIX A -
LimitMoment A-I APPENDIX B -
Toughness Criteria for Turkey Point Units 3 and 4 Cast Primary Loop Components B-1 m%1574-1w.wpf: 1b/122094 VI
WESTINGHOUSE NON-PROPRIETARY CLASS 3
WESTINGHOUSE NON-PROPRIETARY CLASS 3 0
Table Title LIST OF TABLES
~Pa e 3-1 Dimensions, Normal Loads and Normal Stresses for Turkey Point Units 3 and 4 3-5 3-2 Faulted Loads and Stresses for Turkey Point Units 3 and 4 3-6 Measured Tensile Properties for Turkey Point Units 3 and 4 Primary Loop Piping 4-5 4-2 Measured Room Temperature Tensile Properties for Turkey Point Units 3 and 4 Primary Loop Elbow Fittings 4-8 4-3 Mechanical Properties for Turkey Point Units 3 and 4 Materials at Operating Temperatures 4-10 4-4 Fracture Toughness Properties for Turkey Point Units 3 and 4 Primary Loops for Leak-Before-Break Evaluation at Critical Locations 4-11 6-1 Flaw Sizes Yielding a Leak Rate of 10 gpm at the Governing Locations 6-4 m%1574-1w.wpf: 1b/122094 vli
WESTINGHOUSE NON-PROPRIETARY CLASS 3 LIST OF TABLES (cont)
Table Title
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7-1 Stability Results for Turkey Point Units 3 and 4 Based on Elastic-Plastic J-Integral Evaluations 7-5 7-2 Stability Results for Turkey Point Units 3 and 4 Based on LimitLoad 7-6 8-1 Summary of Reactor Vessel Transients 8-3 8-2 Typical Fatigue Crack Growth at [
]'~'40 Years) 8-4 9-1 Leakage Flaw Size, Critical Flaw Sizes and Margins for Turkey Point Units 3 and 4 9-2 B
Chemistry and Fracture Toughness Properties of the Material Heats of Turkey Point Units 3 and 4 B-2 rK)1574-1w.wpf:lb/122094 Vill
WESTINGHOUSE NON-PROPRIETARY CLASS 3 LIST OF FIGURES
~Fi ure Title
~Pa e 3-1 Hot Leg Coolant Pipe 3-7 3-2 Schematic Diagram of Turkey Point Units 3 and 4 Primary Loop Showing Weld Locations 3-8 Representative Lower Bound True Stress - True Strain Curve for A351 CF8M at 608'F
,4-'12 4-2 Representative Lower Bound True Stress - True Strain Curve for A351 CF8M at 547'F Pre-Service J vs. ha for SA351 CF8M Cast Stainless Steel at 600'F 4-14 J vs. ha at Different Temperatures for Aged Material
[
]'"'7500 Hours at 400'C) 4-15 6-1 Analytical Predictions of Critical Flow Rates of Steam-Water Mixtures 6-5 6-2
[
of L/D
]'~'ressure Ratio as a Function 6-6 6-3 Idealized Pressure Drop Profile Through a Postulated Crack 6-.7 mh1574-1w.wpf: 1b/122094 Ix
WESTINGHOUSE NON-PROPRIETARY CLASS 3 LIST OF FIGURES (cont)
~Fi ure Title
~Pa e
7-1
]'~'tress Distribution 7-7 7-2 Critical Flaw Size Prediction - Hot Leg at Location 1 7-8 7-3 Critical Flaw Size Prediction - Hot Leg at Location 2 7-9 7-4 Critical Flaw Size Prediction - Cold Leg at Location 11 7-10 8-1 Typical Cross-Section of [
8-5 8-2 Reference Fatigue Crack Growth Curves for [
]I+,e 8-6'-3 Reference Fatigue Crack Growth Law for [
in a Water Environment at 600'F 8-7 A-1 Pipe with a Through-Wall Crack in Bending A-2 m:51574-lw.wpf: 1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 EXECUTIVE
SUMMARY
The original structural design basis of the reactor coolant system for the Florida Power and Light Company (FPL) Turkey Point Units 3 and 4 Nuclear Power Plants required consideration of dynamic effects resulting from pipe break and that protective measures for such breaks be incorporated into the design.
Subsequent to the original Turkey Point design, additional concern of asymmetric blowdown loads was raised as described in Unresolved Safety Issue A-2 (Asymmetric Blowdown Loads on the Reactor Coolant System) and Generic Letter 84-04 (Reference 1-1). However, research by the NRC and industry coupled with operating experience determined that safety could be negatively impacted by placement of pipe whip restraints on certain systems.
As a result, NRC and industry initiatives insulted in demonstrating that Leak-before-break (LBB) criteria can be applied to reactor coolant system piping based on fracture mechanics technology and material toughness.
Generic analyses by Westinghouse for the application of LBB for specific plants was documented in response to Unresolved Safety Issue A-2 and approved for Turkey Point in NRC letter dated November 28, 1988 (Reference 1-10). By letter dated November 28, 1988, the NRC stated that:
"...an acceptable technical basis had been provided so that the asymmetric loads resulting from double-ended pipe breaks in main coolant loop piping need not be considered as a design basis for certain plants, including Turkey Point Units 3 and 4, provided two conditions are satisfied.
However, of the two conditions, only the one relating to the leakage detection system applies to Turkey Point Units 3 and 4. Specifically, the condition requires that leakage detection systems be sufficient to provide adequate margin to detect the postulated circumferential throughwall flaw utilizing the guidance of Regulatory Guide 1.45.....
We have reviewed your November 1, 1988 submittal and concur that the leakage detection systems at Turkey Point Units 3 and 4 satisfy the requirements in Generic Letter 84-04.
This closes MPA [Multi-Plant Action] D-10 for Turkey Point Units 3 and 4. Turkey Point Units 3 and 4 primary loop piping also complies with the revised General Design Criteria 4 (GDC-4) of Appendix A to 10 CFR Part 50, and the dynamic effects of postulated primary loop pipe ruptures may be eliminated from the design basis."
m%1574-1w.wpf: 1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 This report demonstrates compliance with LBB technology for the Turkey Point reactor coolant system piping based on a plant specific analysis.
The report documents the plant specific geometry, loading, and material properties used in the fracture mechanics evaluation.
Mechanical properties were determined at operating temperatures.
Since the piping systems include cast stainless steel fittings, fracture toughnesses considering thermal aging were determined for each heat of material.
Based on loading, pipe geometry and fracture toughness considerations, enveloping critical locations were determined at which leak-before-break crack stability evaluations were made.
Through-wall flaw sizes were found which would cause leak at a rate of ten times the leakage detection system capability of the plant.
Large margins for such flaw sizes were demonstrated against flaw instability. Finally, fatigue crack growth was shown not to be an issue for the primary loops.
It is concluded that dynamic effects of reactor coolant system primary loop pipe breaks need not be considered in the structural design basis of the Turkey Point Units 3 and 4 Nuclear Power Plants.
m:51574-1w.wpf: 1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3
'ECTION
1.0 INTRODUCTION
1.1 Purpose This report applies to the Turkey Point Units 3 and 4 Reactor Coolant System (RCS) primary loop piping. It is intended to demonstrate that for the specific parameters of the Turkey Point Units 3 and 4 Nuclear Power Plants, RCS primary loop pipe breaks need not be considered in the structural design basis.
The approach taken has been accepted by the Nuclear Regulatory Commission (NRC) (Reference 1-1).
1.2 Background Information Westinghouse has performed considerable testing and analysis to demonstrate that RCS primary loop pipe breaks can be eliminated from the structural design basis of all Westinghouse plants.
The concept of eliminating pipe breaks in the RCS primary loop was first presented to the NRC in 1978 in WCAP-9283 (Reference 1-2). That topical report employed a deterministic fracture mechanics evaluation and a probabilistic analysis to support
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the elimination of RCS primary loop pipe breaks.
That approach was then used as a means of addressing Generic Issue A-2 and Asymmetric LOCA Loads.
Westinghouse performed additional testing and analysis to justify the elimination of RCS primary loop pipe breaks.
This material was provided to the NRC along with Letter Report NS-EPR-2519 (Reference 1-3).
The NRC funded research through Lawrence Livermore National Laboratory (LLNL)to address this same issue using a probabilistic approach.
As part of the LLNLresearch effort, Westinghouse perforined extensive evaluations of specific plant loads, material properties, transients, and system geometries to demonstrate that the analysis and testing previously performed by Westinghouse and the research performed by LLNLapplied to all Westinghouse plants (References 1-4 and 1-5). The results from the LLNLstudy were released at a March 28, 1983, ACRS Subcommittee meeting.
These studies which are applicable to all Westinghouse plants east of the Rocky Mountains determined the mean probability of a direct LOCA (RCS primary loop pipe break) to be 4.4 x 10 per reactor
-12
-7 year and the mean probability of an indirect LOCA to be 10 per reactor year.
Thus, the results previously obtained by Westinghouse (Reference 1-2) were confirmed by an independent NRC research study.
rK51574-lw.wpf:1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Based on the studies by Westinghouse, LLNL,the ACRS, and the AIF, the NRC completed a safety review of the Westinghouse reports submitted to address asymmetric blowdown loads that result from a number of discrete break locations on the PWR primary systems.
The NRC Staff evaluation (Reference 1-1) concludes that an acceptable technical basis has been provided so that asymmetric blowdown loads need not be considered for those plants that can demonstrate the applicability of the modeling and conclusions contained in the Westinghouse response or can provide an equivalent fracture mechanics demonstration of the primary coolant loop integrity. In a more formal recognition of Leak-Before-Break (LBB) methodology applicability for PWRs, the NRC appropriately modified 10 CFR 50, General Design Criterion 4, "Requirements for Protection Against Dynamic Effects for Postulated Pipe Rupture" (Reference 1-6).
1.3 Scope and Objective The general purpose of this investigation is to demonstrate leak-before-break for the primary loops in Turkey Point Units 3 and 4. While the Standard Review Plan which is documented in Reference 1-7 was not in existence at the time Turkey Point Units 3 and 4 were licensed, the recommendations and criteria proposed in Reference 1-7 are used in this evaluation.
These criteria and resulting steps of the evaluation procedure can be briefly summarized as follows:
1)
Calculate the applied loads.
Identify the location at which the highest stress occurs.
2)
Identify the materials and the associated material properties.
3)
Postulate a surface flaw at the governing location.
Determine fatigue crack growth.
Show that a through-wall crack willnot result.
4)
Postulate a through-wall flaw at the governing location.
The size of the flaw should be large enough so that the leakage is assured of detection with margin using the installed leak detection equipment when the pipe is subjected to norinal operating loads. A margin of 10 is demonstrated between the calculated leak rate and the leak detection capability.
5)
Using faulted loads, demonstrate that there is a margin of at least 2 between the leakage size flaw and the critical size flaw.
m%1574-1w.wpf: 1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Q
6)
Review the operating history to ascertain that operating experience has indicated no particular susceptibility to failure from the effects of corrosion, water hammer or low and high cycle fatigue.
7)
For the materials actually used in the plant provide the properties including toughness and tensile test data.
Evaluate long terra effects such as thermal aging where applicable.
8)
Demonstrate margin on applied load.
This report provides a fracture mechanics demonstration of primary loop integrity for the Turkey Point Units 3 and 4 Plants consistent with the NRC position for exemption from consideration of dynamic effects.
Several computer codes are used in the evaluations.
The main-frame computer programs are under Configuration Control which has requirements conforming to NRC's Standard Review Plan 3.9.1 (Reference 1-8).
The fracture mechanics calculations are independently verified (benchmarked).
1.4 References 1-1 USNRC Generic Letter 84-04,
Subject:
"Safety Evaluation of Westinghouse Topical Reports Dealing with Elimination of Postulated Pipe Breaks in PWR Primary Main Loops," February 1, 1984.
1-2 WCAP-9283, "The Integrity of Primary Piping Systems of Westinghouse Nuclear Power Plants During Postulated Seismic Events," March, 1978.
1-3 Letter Report NS-EPR-2519, Westinghouse (E. P. Rahe) to NRC (D. G. Eisenhut),
Westinghouse Proprietary Class 2, November 10, 1981.
1-4 Letter from Westinghouse (E. P. Rahe) to NRC (W. V. Johnston) dated April 25, 1983.
1-5 Letter from Westinghouse (E. P. Rahe) to NRC (W. V. Johnston) dated July 25, 1983.
m:51574-1w.wpf: 1b/122094 1-3
WESTINGHOUSE NON-PROPRIETARY CLASS 3 1-6 Nuclear Regulatory Commission, 10 CFR 50, Modification of General Design Criteria 4 Requirements for Protection Against Dynamic Effects of Postulated Pipe Ruptures, Final Rule, Federal Register/Vol. 52, No. 207/Tuesday, October 27, 1987/Rules and Regulations, pp. 41288-41295.
1-7 Standard Review Plan:
Public Comments Solicited; 3.6.3 Leak-Before-Break Evaluation Procedures; Federal Register/Vol. 52, No. 167/Friday August 28, 1987/Notices, pp. 32626-32633.
1-8 Nuclear Regulatory Commission, Standard Review Plan Section 3.9.1, "Special Topics for Mechanical Component," NUREG-0800, Revision 2, July 1981.
1-9 WCAP-7211, Revision 3, "Energy Systems Business Unit Policy and Procedures for Management, Classification, and Release of Information," March, 1994.
1-10 Nuclear Regulatory Commission Docket 0's 50-250 and 50-251 Letter from G. E. Edison, Sr. Pxoject Manager, NRC, to W. F. Conway, Sr. Vice President, Florida Power and Light,
Subject:
"Turkey Point Units 3 and 4, Generic Letter 84-04, Asymmetric LOCA Loads," dated 11/28/88.
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WESTINGHOUSE NON-PROPRIETARY CLASS 3 SECTION 2.0 OPERATION AND STABILITYOF THE REACTOR COOLANT SYSTEM 2.1 Stress Corrosion Cracking The Westinghouse reactor coolant system primary loops have an operating history that demonstrates the inherent operating stability characteristics of the design.
This includes a low susceptibility to cracking failure from the effects of corrosion (e.g., intergranular stress corrosion cracking (IGSCC)).
This operating history totals over 800 reactor-years, including five plants each having over 18 years of operation and 15 other plants each with over 13 years of operation.
In 1978, the United States Nuclear Regulatory Commission (USNRC) formed the second Pipe Crack Study Group.
(The first Pipe Crack Study Group (PCSG) established in 1975 addressed cracking in boiling water reactors only.)
One of the objectives of the second PCSG was to include a review of the potential for stress corrosion cracking in Pressurized Water Reactors (PWR's).
The results of the study performed by the PCSG were presented in NUREG-0531 (Reference 2-1) entitled "Investigation and Evaluation of Stress Corrosion e
L Cracking in Piping of Light Water Reactor Plants."
In that report the PCSG stated:
"The PCSG has determined that the potential for stress-corrosion cracking in PWR primary system piping is extremely low because the ingredients that produce IGSCC are not all present.
The use of hydrazine additives and a hydrogen overpressure limit the oxygen in the coolant to very low levels.
Other impurities that might cause stress-corrosion cracking, such as halides or caustic, are also rigidly controlled.
Only for brief periods during reactor shutdown when the coolant is exposed to the air and during the subsequent startup are conditions even marginally capable of producing stress-corrosion cracking in the primary systems of PWRs.
Operating experience in PWRs supports this determination.
To date, no stress corrosion cracking has been reported in the primary piping or safe ends of any PWR."
During 1979, several instances of cracking in PWR feedwater piping led to the establishment of the third PCSG.
The investigations of the PCSG reported in NUREG-0691 (Reference 2-2) further confirmed that no occurrences of IGSCC have been reported for PWR primary coolant systems.
As stated above, for the Westinghouse plants there is no history of cracking failure in the reactor coolant system loop. The discussion below further qualifies the PCSG's findings.
mA1574w.wpf: 1b/122794 2-1
WESTINGHOUSE NON-PROPRIETARY CLASS 3 For stress corrosion cracking (SCC) to occur in piping, the following three conditions must exist simultaneously:
high tensile stresses, susceptible material, and a corrosive environment.
Since some residual stresses and some degree of material susceptibility exist in any stainless steel piping, the potential for stress corrosion is minimized by properly selecting a material immune to SCC as well as preventing the occurrence of a corrosive environment.
The material specifications consider compatibility with the system's operating environment (both internal and external) as well as other material in the system, applicable ASME Code. rules, fracture toughness, welding, fabrication, and processing.
The elements of a water environment known to increase the susceptibility of austenitic stainless steel to stress corrosion are:
oxygen, fluorides, chlorides, hydroxides, hydrogen peroxide, and reduced forms of sulfur (e.g., sulfides, sul6tes, and thionates).
Strict pipe cleaning standards prior to operation and careful control of water chemistry during plant operation are used to prevent the occurrence of a corrosive environment.
Prior to being put into service, the piping is cleaned internally and externally.
During flushes and preoperational testing, water chemistry is controlled in accordance with written specifications.
Requirements on chlorides, fluorides, conductivity, and Ph are included in the acceptance criteria for the piping.
During plant operation, the reactor coolant water chemistry is monitored and maintained within very specific limits. Contaminant concentrations are kept below the thresholds known to be conducive to stress corrosion cracking with the major water chemistry control standards being included in the plant operating procedures as a condition for plant operation.
For example, during normal power operation, oxygen concentration in the RCS is expected to be in the ppb range by controlling charging flow chemistry and maintaining hydrogen in the reactor coolant at specified concentrations.
Halogen concentrations are also stringently controHed by maintaining concentrations of chlorides and fluorides within the specified limits.
Thus dtuing plant operation, the likelihood of stress corrosion cracking is minimized.
2.2 Water Hammer Overall, there is a low potential for water hammer in the RCS since it is designed and operated to preclude the voiding condition in normally flied lines.
The reactor coolant system, including piping and primary components, is designed for normal, upset, emergency, and faulted condition transients.
The design requirements are conservative relative to both the number of transients and their severity.
Relief valve actuation and the associated hydraulic transients following valve opening are considered in the system design.
Other valve and pump actuations are relatively slow transients with no significant effect on the system m:51574-1w.wpf: 1b/122094 2-2
WESTINGHOUSE NON-PROPRIETARY CLASS 3 dynamic loads.
To ensure dynamic system stability, reactor coolant parameters are stringently
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controlled.
Temperature diuing normal operation is maintained within a narrow range by control rod position; pressure is controlled by pressurizer heaters and pressurizer spray also within a narrow range for steady-state conditions.
The flow characteristics of the system remain constant during a fuel cycle because the only governing parameters, namely system resistance and the reactor coolant pump characteristics, are controlled in the design process.
Additionally, Westinghouse has instrumented typical reactor coolant systems to verify the flow and vibration characteristics of the system.
Preoperational testing and operating experience have verified the Westinghouse approach.
The operating transients of the RCS primary piping are such that no signiQcant water hammer can occur.
2.3 Low Cyde and High Cycle Fatigue Low cycle fatigue considerations are accounted for in the design of the piping system through the fatigue usage factor evaluation to show compliance with the rules of Section IIIof the ASME Code. A further evaluation of the low cycle fatigue loadings was carried out as part of this study in the form of a fatigue crack growth analysis, as discussed in Section 8.0.
High cycle fatigue loads in the system would result primarily f'rom pump vibrations.
These
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are minimized by restrictions placed on shaft vibrations during hot functional testing and operation.
During operation, an alarm signals the exceedence of the vibration limits. Field measurements have been made on a number of plants during hot functional testing, including plants similar to Turkey Point Units 3 and 4.
Stresses in the elbow below the reactor coolant pump resulting from system vibration have been found to be very small, between 2 and 3 ksi at the highest.
These stresses are well below the fatigue endurance limitfor the material and would also result in an applied stress intensity factor below the threshold for fatigue crack growth.
2.4 References 2-1 Investigation and Evaluation of Stress-Corrosion Cracking in Piping of LightWater Reactor Plants, NUREG-0531, U.S. Nuclear Regulatory Commission, February 1979.
2-2 Investigation and Evaluation of Cracking Incidents in Piping in Pressurized Water Reactors, NUREG-0691, U.S. Nuclear Regulatory Commission, September 1980.
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WESTINGHOUSE NON-PROPRIETARY CLASS 3
WESTINGHOUSE NON-PROPRIETARY CLASS 3 SECTION 3.0 PIPE GEOMETRY AND LOADING 3.1 Introduction to Methodology The general approach is discussed first. As an example a segment of the primary coolant hot leg pipe is shown in Figure 3-1.
The as-built outside diameter and minimum wall thickness of the pipe are 34.00 in. and 2.395 in., respectively, as shown in the figure. The normal stresses at the weld locations are from the load combination procedure discussed in Section 3.3 whereas the faulted loads ate as described in Section 3.4.
The components for normal loads are pressure, dead weight and thermal expansion.
An additional component, Safe Shutdown Earthquake (SSE), is considered for faulted loads.
As seen from Table 3-2, the highest stressed location in the entire loop is at Location 1 at the reactor vessel outlet nozzle to pipe weld. This highest stressed location is a load critical location and is one of the locations at which, as an enveloping location, leak-before-break is to be established.
Essentially a circumferential flaw is postulated to exist at this location which is subjected to both the normal loads and faulted loads to assess leakage and stability, respectively.
The loads (developed below) at this location are also given in Figure 3-1.
Since the elbows are made of cast stainless steel, thermal aging must be considered (Section 4.0). Thermal aging results in lower fracture toughness; thus, locations other than the load critical locations must be examined taking into consideration both fracture toughness and stress.
The enveloping locations so determined are called tou hness critical locations.
Two most critical locations are identified after the full analysis is completed.
Once loads (this section) and fracture toughnesses (Section 4.0) are obtained, the load critical and toughness critical locations are determined (Section 5.0). At these locations, leak rate evaluations (Section 6.0) and fracture mechanics evaluations (Section 7.0) are performed per the guidance of Reference 3-1.
Fatigue crack growth (Section 8.0) and stability margins are also evaluated (Section 9.0).
The locations for evaluation are those shown in Figure 3-2.
m:51574-1w.wpf: 1b/122094 3-1
WESTINGHOUSE NON-PROPRIETARY CLASS 3 3.2 Calculation of Loads and Stresses The stresses due to axial loads and bending moments are calculated by the following equation:
Q
+
F M
A Z
(3-1)
- where, a
=
stress F
M A
Z axial load bending moment pipe cross-sectional area section modulus The bending moments for the desired loading combinations are calculated by the following equation:
M= Mr +Mz (3-2)
- where, MY MZ bending moment for required loading Y component of bending moment Z component of bending moment The axial load and bending moments for leak rate predictions and crack stability analyses are computed by the methods to be explained in Sections 3.3 and 3.4.
e mal 574-1w.wpf:1b/122094 3-2
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Loads for Leak Rate Evaluation The normal operating loads for leak rate predictions are calculated by the following equations:
F
=
FDW+ FTH+ FP MY (MY)DW+ (MY)TH+ (MY)P Z
=
( Z)DW+ ( Z)TH+ (
Z)I (3-3)
(3-4)
(3-5)
The subscripts of the above equations represent the following loading cases:
DW TH P
deadweight normal thermal expansion load due to internal pressure This method of combining loads is often referred as the al ebraic sum method (Reference 3-1).
The loads based on this method of combination are provided in Table 3-1 at all the locations
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identified in Figure 3-2. The as-built dimensions are also given.
3.4 Load Combination for Crack Stability Analyses In accordance with Standard Review Plan 3.6.3 (Reference 3-1) the absolute sum of loading components can be applied which results in higher magnitude of combined loads. Ifcrack stability is demonstrated using these loads, the LBB margin on loads can be reduced from 42 to 1.0.
The absolute summation of loads are shown in the following equations:
F = IFDw I+ I Fm I+ IFp I+ I FssHNaR~ I+IF~ I M =l(M )
I+I(M)
I+I(M) I+I(M)
'I+I(M )
I Mz = I (Mz)ow I+ I (Mz)Tn I + I (Mz)p I+ I (Mz)ss~iiA I+ I (Mz)ssaAM I (3-6)
(3-7)
(3-8) where subscripts SSE, INERTIAand AMmean safe shutdown earthquake, inertia and anchor motion, respectively.
mh1574-1w.wpf: 1b/122094 3-3
WESTINGHOUSE NON-PROPRIETARY CLASS 3 The loads so determined are used in the fracture mechanics evaluations (Section 7.0) to demonstrate the LBB margins at the locations established to be the governing locations.
These loads at all the locations of interest (see Figure 3-2) are given in Table 3-2.
3.5 References 3-1 Standard Review Plan:
Public Comments Solicited; 3.6.3 Leak-Before-Break Evaluation Procedures; Federal Register/Vol. 52, No. 167/Friday, August 28, 1987/Notices, pp. 32626-32633.
m:51574-1w.wpf: 1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 0
Table 3-1 Dimensions, Normal Loads and Normal Stresses for Turkey Point Units 3 and 4 Location'0 12 Outside Diameter (in.)
34.00 34.00 37.75 37.62 36.25 36.25 36.25 36.25 37.63 32.25 32.25 33 56 Minimum Thickness (in.)
2.395 2.395 3.270 3.205 2.520 2.520 2.520 2.520 3.208 2.270 2.270 2 930 Axial Loadb (kips) 1341 1341 1578 1715 1657 1653 1719 1716 1819 1363 1363 1363 Bending Moment (in-kips) 23453 11266 17788 3777 4329 4422 781 3712 8794 6861 6878 7759 Total Stress (ksi) 18.99 12.05 10.77 6.32 8.26 8.29 6.81 8.19 10.95 10.96 8.75 b
See Figure 3-2 Includes pressure m:51574-1w.wpf: 1b/122094 3-5
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 3-2 Faulted Loads and Stresses for Turkey Point Units 3 and 4 Location~~
10 12 Axial Load'kips) 1877 1876 2007 1745 1824 1821 1743 1745 1832 1434 1435 1430 Bending Moment (in-kips) 24027 11912 20886 5043 5235 4834 1169 4385 10705 9600 8097 9331 Total Stress (ksi) 21.57 14.67 13.09 6.87 9.32 9.11 7.08 8.62 9.17 13.12 12.12 9.78 b
See Figure 3-2 See Table 3-1 for dimensions Includes pressure m:51574-1w.wpf: 1b/122094 3-6
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Crack p
P'p )q4 OD OD' 34.00 in t'
2.395 in Normal Loads'orce':
1341 kips bending moment:
23453 in-kips Faulted Loads'orce':
1877 kips bending moment:
24027 in-kips
'ee Table 3-1
'ee Table 3-2
'ncludes the force due to a pressure of 2250 psia Figure 3-1 Hot Leg Coolant Pipe m:51574w.wpf: lb/121994 3-7
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Reactor Pressure Vessel HOT LEG COLD LEG REACTOR COOLANTPUMPl
~ STEAM GENERATOR CROSSOVER LEG HOT LEG Temperature 608'F, Pressure:
2250 psia CROSSOVER LEG Temperature 547'F, Pressure:
2250 psia COLD LEG Temperature 547'F, Pressure:
2250 psia
, Figure 3-2 Schematic Diagram of Turkey Point Units 3 and 4 Primary Loop Showing Weld Locations mA1574w.wpf:1b/121994 3-8
WESTINGHOUSE NON-PROPRIETARY CLASS 3 SECTION 4.0 MATERIALCHARACTERIZATION 4.1 Primary Loop Pipe and Fittings Materials The primary loop pipe materials are A376 TP316, and the elbow fittings are A351 CF8M.
4.2 Tensile Properties The Pipe Certified Materials Test Reports (CMTEb) for Turkey Point Units 3 and 4 were used to establish the tensile properties for the leak-before-break analyses.
The CMTRs include tensile properties at room temperature and/or at 650'F for each of the heats of material.
These properties are given in Table 4-1 for piping and in Table 4-2 for elbow fittings.
For the A376 TP316 material, the representative properties at 608'F were established from the tensile properties at 650'F given in Table 4-1 by utilizing Section IIIof the 1989 ASME
~
~
~
~
~
Boiler and Pressure Vessel Code (Reference 4-6).
Code tensile properties at 608'F were obtained by interpolating between the 600'F and 650'F tensile properties.
Ratios of the code tensile properties at 608'F to the corresponding tensile properties at 650'F were then applied to the 650'F tensile properties given in Table 4-1 to obtain the plant specific properties for A376 TP316 at 608'F.
The Elbow Fittings Certified Materials Test Reports (ChfIRs) for Turkey Point Units 3 and 4 were used to establish the tensile properties for the leak-before-break analyses.
The CMTEb for elbow fittings include tensile properties at room temperature for each of the heats of material.
These properties are given for Turkey Point Units 3 and 4 in Table 4-2.
For the A351 CF8M material, the representative properties at 608'F and 547'F were established from the tensile properties at room temperature given in Table 4-2 by utilizing Section IIIof the 1989 ASME Boiler and Pressure Vessel Code.
Code tensile properties at 608'F and 547'F were established by interpolating between the 500'F, 600'F and the 650'F tensile properties.
Ratios of the code tensile properties at 608'F and 547'F to the corresponding properties at room temperature were then applied to the room temperature properties given in Table 4-2 to obtain the plant specific representative properties for A351 CF8M at 608'F and 547'F.
mA1574w.wpf:1b/122794
WESTINGHOUSE NON-PROPRIETARY CLASS 3 The average and lower bound yield strengths and ultimate strengths are given in Table 4-3.
The ASME Code moduli of elasticity are also given, and Poisson's ratio was taken as 0.3.
For leak-before-break fracture evaluations of the toughness critical locations the true stress-true strain curves for A351 CF8M at 608'F and 547'F must be available.
These curves were obtained using the Nuclear Systems Materials Handbook (Reference 4-1). The lower bound true stress-true strain curves are given in Figures 4-1 and 4-2.
4.3 Fracture Toughness Properties The pre-service fracture toughnesses of both forged and cast stainless steels of interes't here have in terms of Jbeen found to be very high at 600'F.
Typical results for a cast material are given in Figure 4-3. J is observed to be over 2500 in-lbs/in~. Forged materials are even higher.
However, cast stainless steels are subject to thermal aging during service.
This thermal aging causes an elevation in the yield strength of the material and a degradation of the fracture toughness, the degree of degradation being somewhat proportional to the level of ferrite in the material.
To determine the effects of thermal aging on piping integrity, a detailed study was carried out in Reference 4-2. In that report, fracture toughness results were presented for a material
[
]'"'he effects of the aging process on the end-of-service life fracture toughness are further discussed in Appendix B.
End-of-service life toughnesses for the heats are established using the alternate toughness criteria methodology of Reference 4-5 (Appendix B). By that methodology a heat of material is said to be as good as [
]'"'fit can be demonstrated that its end-of-service fracture toughnesses equal or exceed those of [
]'"'. The worst case fracture toughness values m:)1574-1w.wpf: 1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 for Turkey Point Units 3 and 4 loops at critical locations, as taken from Appendix B, are given in Table 4-4.
Available data on aged stainless steel welds (References 4-2 and 4-3) indicate that Jvalues for the worst case welds are of the same order as the aged material.
However, the slope of the J-R curve is steeper, and higher J-values have been obtained from fracture tests (in excess of 3000 in-lb/in ). The applied value of the J-integral for a flaw in the weld regions willbe lower than that in the base metal because the yield stress for the weld materials is much higher at the temperature'.
Therefore, weld regions are less limiting than the cast material.
It is thus conservative to choose the end-of-service life toughness properties of [
]'~'s representative of those of the welds.
Also, such pipes and fittings have an end-of-service life calculated room temperature Charpy U-notch energy, (KCU), greater than that of f
]'~'re also conservatively assumed to have the properties of [
]**'.
In fracture mechanics analyses that follow, the fracture toughness properties given in Table 4-4 willbe used as the criteria against which the applied fracture toughness values will be compared.
Forged stainless steel piping such as A376 TP316 does not degrade due to thermal aging.
Thus fracture toughness values well in excess of that established for the cast material'and welds exist for this material throughout service life and are not limiting.
4.4 References 4-1 Nuclear Systems Materials Handbook, Part I - Structural Materials, Group 1 - High Alloy Steels, Section 2, ERDA Report TID 26666, November, 1975.
4-2 WCAP-10456, "The Effects of Thermal Aging on the Structural Integrity of Cast Stainless Steel Piping for W NSSS," W Proprietary Class 2, November 1983.
In the report all the applied J values were conservatively determined by using base metal strength properties.
m%1574-1w.wpf:lb/122094 4-3
WESTINGHOUSE NON-PROPRIETARY CLASS 3 4-3 Slama, G., Petrequin, P., Masson, S.H., and Mager, T.R., "Effect of Aging on Mechanical Properties of Austenitic Stainless Steel Casting and Welds", presented at Smirt 7 Post Conference Seminar 6 - Assuring Structural Integrity of Steel Reactor Pressure Boundary Components, August 29/30, 1983, Monterey, CA.
4-4 Appendix IIof Letter from Dominic C. DiIanni, NRC to D. M. Musolf, Northern States Power Company, Docket Nos. 50-282 and 50-306, December 22, 1986.
4-5 Witt, F.J., Kim, C.C., "Toughness Criteria for Thermally Aged Cast Stainless Steel,"
WCAP-10931, Revision 1, Westinghouse Electric Corporation, July 1986, (Westinghouse Proprietary Class 2).
4-6 ASME Boiler and Pressure Vessel Code 1989, Section IH.
m:51574-1w.wpf: 1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 4-1 Measured Tensile Properties for Turkey Point Units 3 and 4 Primary Loop Piping Component Heat Num.
Yield Room Temp (psi)
Ultimate Room Temp (psi)
Yield Temp 650F (psi)
Ultimate Temp 650F (psi)
Material Type Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg ot Leg Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Cold Leg Cold Leg old Leg F0070 ¹2646 38200 F0070 ¹2646 34100 F0214 ¹2850 42000 F0214 ¹2850 43000 F0188 ¹2844 39200 F0188 ¹2844 38900 D8549 ¹1170 30100 D8549 ¹1170 36900 F0215 ¹2892X 43000 F0215 ¹2892X 42000 F0225 ¹2895X 42000 F0225 ¹2895X 46000 E-1493 ¹3356 42000 E-1493 ¹3356 42600 E-1485 ¹3352X 42300 E-1485 ¹3352X 45400 E-1482 ¹3355 40900 E-1482 ¹3355 48600 E-1483 ¹3357 42100 E-1483 ¹3357 43000 E-1490 ¹3348Y 46000 E-1490 ¹3348Y 40900 E-1490 ¹3347X 43100 E-1490 ¹3347X 43000 D8777 ¹2874X 35300 D8777 ¹2874X 34900 D8913 ¹2877 35100 79000 21000 78200 21000 83300 22400 82800 22400 83400 26100 84000 26100 75000 22100 79000 22100 83000 21700 84600 21700 85900 22100 88800 22100 83100 25500 84500 25500 85400 27500 87400 27500 82700 24500 88800 24500 85000 23700 85200 23700 85700 23700 83300 23700 86000 23700 82700 23700 79200 24100 78200 24100 79200 23100 60800 60800 62300 62300 67000 67000 63400 63400 66800 66800 68200 68200 69200 69200 72200 72200 66200 66200 52100 52100 68600 68600 68600 68600 65600 65600 64200 A-376TP316 A-376TP316 A-376TP31 6 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP31 6 A-376TP316 A-376TP316 A-376TP316 A'-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP31 6 A-376TP31 6 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 m%1574-1w.wpf: lb/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 4-1 (cont)
Measured Tensile Properties for Turkey Point Units 3 and 4 Primary Loop Piping Component Heat Num.
Yield Room Temp (psi)
Ultimate Room Temp (psi)
Yield Temp 650F (psi)
Ultimate Temp 650F (psi)
Material Type Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg D8913 ¹2877 38100 D8915 ¹2876 34100 D8915 ¹2876 32800 F0230 ¹2993 48000 F0230 ¹2993 47000 F0162 ¹2858 43700 F0162 ¹2858 46200 F0371 ¹3130 47000 F0371 ¹3130 44000 F0228 ¹2949 42200 F0228 ¹2949 45000 F0373 ¹3166 40100 F0373 ¹3166 45500 F0244 ¹2997 42900 F0244 ¹2997 47500 F0229 ¹2950 41000 F0229 ¹2950 44400 F0371 ¹3128 46800 F0371 ¹3128 36900 F0189 ¹2868Z 37700 F0189 ¹2868Z 44100 F0189 ¹2870X 41300 F0189 ¹2870X 42900 F0189 ¹2870Y 41300 F0189 ¹2870Y 42900 D8775 ¹2880 34100 D8775 ¹2880 41100 79600 23100 64200 78400 22500 63600 78600 22500 63600 88100 21700 70200 90900 21700 70200 83100 27600 69400 84900 27600 69400 88700 25600 72300 88800 25600 72300 86100 24700 69800 89900 24700 69800 86900 25600 71900 91900 25600 71900 85400 25400 69900 88100 25400 69900 85700 24500 68200 86400 24500 68200 78700 25600 72300 84700 25600 72300 80600 25200 70000 91000 25200 70000 82200 25200 70000 84200 25200 70000 82200 25200 70000 84200 25200 70000 75800 24000 60400 77800 24000 60400 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A'-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A.-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 mh1574-1w.wpf: 1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 4-1 (cont)
Measured Tensile Properties for Turkey Point Units 3 and 4 Primary Loop Piping Component Heat Num.
Yield Room Temp (psi)
Ultimate Room Temp (psi)
Yield Temp 650F (psi)
Ultimate Temp 650F (ps )
Material Type Xover Leg Xover Leg Xover Leg Xover Leg D8777 ¹2879 38100 D8777 ¹2879 38500 D8785 ¹2881 32900 D8785 ¹2881 34100 78200 78200 78200 79000 20200 60000 20200 60000 20400 57200 20400 57200 A-376TP316 A-376TP316 A-376TP316 A-376TP316 Xover Leg E-1485 ¹3361Y 38300 Xover Leg E-1485 ¹3361Y 45900 Xover Leg F-0215 ¹2892 40000 Xover Leg F-0215 ¹2892 41900 Xover Leg F-0221 ¹2866 41000 Xover Leg F-0221 ¹2866 41500 83900 91400 84800 87700 83900 83000 23600 70700 23600 70700 21700 82300 21700 82300 21600 65200 21600 65200 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 over Leg E-1484 ¹3360X 39600 83300 Xover Leg E-1484 ¹3360X 44500 Xover Leg F-0212 ¹2887 43500 Xover Leg F-0212 ¹2887 43200 88800 85100 88000 Xover Leg E-1484 ¹3360Y 39600 83300 23600 63600 23600 63600 23400 67400 23400 67400 23600 63600 A-376TP316 A-376TP316 A-376TP316 A-376TP316 A-376TP316 Xover Leg E-1484 ¹3360Y 44500 88800 23600 63600 A'-376TP316 m:51574-1w.wyf: 1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 4-2 Measured Room Temyerature Tensile Properties for Turkey Point Units 3 and 4 Primary Loop Elbow Httings Corny onent Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Hot Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Cold Leg Xover Leg Xover Le Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Heat Num.
11897-2 12121-2 12012-2 08368-1 08247-1 08586-1 16037-1 10865-2 12393-4 05872-2 05769-5 05715-2 10048-1 10763-1 10008-1 10804-1 10091-1 10128-1 10320-1 10563-1 10283-1 10243-1 10400-1 10644-1 09476-3 09027-1 06239-2 Yield Room Temp (psi) 39000 43500 39000 43500 46500 40000 37500 42000 42000 49500 52500 51000 45000 44250 46500 43500 42000 46500 48000 43500 48000 46500 48000 49500 45000 48000 48000 Ultimate Room Temp (psi) 76000 85000 77000 87500 88000 84000 75000 81500 83000 89000 93500 90000 87000 81000 88000 81000 86500 89000 91500 88000 91500 90000 91500 91000 88000 90500 88000 Material Type A351CFSM A351CF8M A351CF8M A351CF8M A351CFSM A351CFSM A351CFSM A351CF8M A351CFSM A351CFSM A351CF8M A351CF8M A351CFSM A351CF8M A351CF8M A351CF8M A351CF8M A351CFSM A351CFSM A351CF8M A351CF8M A351CF8M A351CF8M A351CF8M A351CF8M A351CF8M A351CFSM m:51574-1w.wpf: 1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 4-2 (cont)
Measured Room Temperature Tensile Properties for Turkey Point Units 3 and 4 Primary Loop Elbow Fittings Component Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Xover Leg Heat Num.
12511-2 12584-2 12357-7 12432-5 11518-1 12087-1 13498-3 14206-1 13378-3 15258-1 12660-2 12857-1 14048-1 14335-1 13133-2 Yield Room Temp (psi) 46500 40500 42000 45000 42000 39000 45750 45000 42000 42000 42000 42000 40500 51000 45000 Ultimate Room Temp (ps )
89000 83250 82500 86000 83750 79000 87250 86250 84250 83750 85000 83500 78500 88500 87000 Material Type A351CF8M A351CF8M A351CF8M A351CFSM A351CFSM A351CF8M A351CF8M A351CF8M A351CF8M A351CF8M A351CF8M A351CFSM A351CF8M A351CF8M A351CF8M mh1574-1w.wpf: 1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 4-3 Mechanical Properties for Turkey Point Units 3 and 4 Materials at Operating Temperatures Material Temperature
('F)
Average Yield Strength (psi)
Yield Stress (ps)
Ultimate Strength (psi)
Lower Bound a,c,e Modulus of Elasticity E = 25.26 x 10'i. at 608'F E = 25.56 x 10'i. at 547'F Poisson's ratio:
0.3 m:51574-1w.wpf: 1b/122094 4-10
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 4-4 Fracture Toughness Properties for Turkey Point Units 3 and 4 Primary Loops for Leak-Before-Break Evaluation at Critical Locations Location<'>
Heat No.
KCU (daJ/cm')
Jic,
(in-Ib/in~)
Tmst.
(non-dim)
Comments
" The locations are shown in Figure 3-2 m:51574-lw.wpf: 1b/122094 4-11
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure 4-1 Representative Lower Bound True Stress - True Strain Curve for A351 CF8M at 608'F mA1574-1w.wpf: 1b/122094 4-12
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure 4-2 Representative Lower Bound True Stress - True Strain Curve for A351 CFSM at 547'F m%1574-1w.wpf:1b/122094 4-13
WESTINGHOUSE NON-PROPRlETARY CLASS 3 Figure 4-3 Pre-Service J vs. ha for SA351 CF8M Cast Stainless Steel at 600'F m%1574-1w.wpf: 1b/122094 4-14
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure 4A J Vs. ha at Different Temperatures for Aged Material
[
]~~'7500 Hours at 400'C) mA1574-lw.wpf:1b/122094 4-15
WESTINGHOUSE NON-PROPRIETARY CLASS 3
WESTINGHOUSE NON-PROPRIETARY CLASS 3 SECTION 5.0 CRITICALLOCATIONS AND EVALUATIONCRITERIA 5.1. Critical Locations The leak-before-break (LBB) evaluation margins are to be demonstrated for the limiting locations (governing locations).
Candidate locations are designated load critical locations or toughness critical locations as discussed in Section 3.0.
Such locations are established based on the loads (Section 3.0) and the material properties established in Section 4.0.
These locations are defined below for Turkey Point Units 3 and 4. Table 3-2 as well as Figure 3-2 are used for this evaluation.
Load Critical Locations The highest stressed location for the A376 TP316 straight pipes is Location 1
(See Figure 3-2) at the reactor vessel outlet nozzle to pipe weld.
Furthermore, since it is on a straight pipe, it is a high toughness location.
Tou hness Critical Locations Low toughness locations are at the ends of every elbow. Allthe elbows except those indicated in page B-1 of Appendix B, exceed the toughness of [
).'"'n the case of the hot leg low toughness are at locations 2 and 3 (See Figure 3-2 for locations).
Location 2 governs since it has higher stress than location 3. In the case of cross over leg and cold leg the lowest toughness is on cold leg at locations 11 and 12. Location 11 governs since it has higher stress and lowest toughness among all the elbow locations in cross over leg and cold leg. It is thus concluded that the enveloping locations are 2 and 11.
The allowable toughness for the critical locations are shown in Table 4-4.
5.2 Fracture Criteria As willbe discussed later, fracture mechanics analyses are made based on loads and postulated flaw sizes related to leakage.
The stability criteria against which the calculated J and tearing modulus are compared are:
(1)
IfJ
< J, then the crack is stable; m%1574-lw.wpf:1b/122094 5-1
WESTINGHOUSE NON-PROPRIETARY CLASS 3 (2)
IfJ
> Jtbut, ifT (T
and J
<J, then the crack is stable.
app max'here:
Japp J
app mat max Applied J J at Crack Initiation Applied Tearing Modulus Material Tearing Modulus Maximum J value of the material These criteria apply to the toughness critical locations.
For critical locations, the limitload method discussed in Section 7.0 is used.
m:51574w.wpf: 1b/122094 5-2
WESTINGHOUSE NON-PROPRIETARY CLASS 3 SECTION 6.0 LEAKRATE PREDICTIONS 6.1 Introduction The purpose of this section is to discuss the method which is used to predict the flow through postulated through-wall cracks and present the leak rate calculation results for through-wall circumferential cracks.
6.2 General Considerations The flow of hot pressurized water through an opening to a lower back pressure causes flashing which can result in choking.
For long channels where the ratio of the channel length, L, to hydraulic diameter, DH, (L/DH) is greater than [ ]'"', both [
]Rg,C 6.3 Calculation Method The basic method used in the leak rate calculations is the method developed by [
The flow rate through a crack was calculated in the following manner.
Figure 6-1 from Reference 6-1 was used to estimate the critical pressure, Pc, for the primary loop enthalpy condition and an assumed flow. Once Pc was found for a given mass flow, the [
]'"'as found from Figure 6-2 (taken from Reference 6-1). For all cases considered, since [
]"'herefore, this method willyield the two-phase pressure drop due to momentum effects as illustrated in Figure 6-3, Po is the operating pressure.
Now using the assumed flow rate, G, the frictional pressure drop can be calculated using mA1574-1w.wpf:1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 hP, = [
]Qg,C (6-1) where the friction factor f is determined using the [
.]* 'he crack relative roughness, c, was obtained from. fatigue crack data on stainless steel samples.
The relative roughness value used in these calculations was [
]'
The frictional pressure drop using equation 6-1 is then calculated for the assumed flow rate and added to the [
]'"'o obtain the total pressure drop from the primary system to the atmosphere.
That is, for the primary loop Absolute Pressure
- 14.7 = [
(6-2) for a given assumed flow rate G. Ifthe right-hand side of equation 6-2 does not agree with the pressure difference between the primary loop and the atmosphere, then the procedure is repeated until equation 6-2 is satisfied to within an acceptable tolerance which in turn leads to correct flow rate value for a given crack size.
6.4 Leak Rate Calculations Leak rate calculations were made as a function of crack length at the governing locations previously identified in Section 5.1. The normal operating loads of Table 3-1 were applied, in these calculations.
The crack opening areas were estimated using the method of Reference 6-2 and the leak rates were calculated using the two-phase flow formulation described above.
The average material properties of Section 4.0 were used for these calculations.
The flaw sizes to yield a leak rate of 10 gpm were calculated at the governing locations and d'Tdl fld. dd*fl d
d*
- d ddd~fl The Turkey Point Units 3 and 4 RCS pressure boundary leak detection system meets the intent of Regulatory Guide 1.45.
Thus, to satisfy the margin of 10 on the leak rate, the flaw
. sizes (leakage flaws) are determined which yield a leak rate of 10 gpm.
m%1574-1w.wpf:lb/122094 6-2
WESTINGHOUSE NON-PROPRIETARY CLASS 3 6.5 References 6-1
[
6-2 Tada, H., "The Effects of Shell Corrections on Stress Intensity Factors and the Crack Opening Area of Circumferential and a Longitudinal Through-Crack in a Pipe,"
Section II-l,NUREG/CR-3464, September 1983.
m:51574-1w.wpf:1b/122094 6-3
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 6-1 Flaw Sizes Yielding a Leak Rate of 10 gym at the Governing Locations Location Flaw Size (in) mh1574-1w.wpf:1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 a,c,e Figure 6-1 Analytical Predictions of Critical Flow Rates of Steam-Water Mxtures I:51574-1w.wpf: 1b/122094 6-5
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure 6-2
]~"'ressure Ratio as a Function of L/D m%1574-1w.wpf:1b/122094 6-6
WESTINGHOUSE NON-PROPRIETARY CLASS 3 a,c,e a,c,e Figure 6-3 Idealized Pressure Drop Pro6le Through a Postulated Crack m:51574w.wpf:1b/121994 6-7
WESTINGHOUSE NON-PROPRIETARY CLASS 3
WESTINGHOUSE NON-PROPRIETARY CLASS 3 0
SECTION 7.0 FRACTURE MECHANICS EVALUATION 7.1 Local Failure Mechanism The local mechanism of failure is primarily dominated by the crack tip behavior in terms of crack-tip blunting, initiation, extension and Qnally crack instability. The local stability willbe assumed ifthe crack does not initiate at all. It has been accepted that the initiation toughness measured in terms of J from a J-integral resistance curve is a material parameter deflning the crack initiation. If, for a given load, the calculated J-integral value is shown to be less than the Jof the material, then the crack willnot initiate. Ifthe initiation criterion is not met, one can calculate the tearing modulus as defined by the following relation:
T.
dJ E
da (Pf where:
0
~PP E
Gf applied tearing modulus modulus of elasticity 0.5 (ay + og (flow stress) crack length yield and ultimate strength of the material, respectively Stability is said to exist when ductile tearing occurs ifT,pp is less than T, the experimentally determined tearing modulus.
Since a constant T is assumed a further restriction is placed in J pp J pp must be less than Jwhere J is the maximum value of J for which the experimental T is greater than or equal to the T used.
As discussed in Section 5.2 the local crack stability willbe established by the two-step criteria:
(1) IfJ
< J, then the crack willnot initiate.
app (2) IfJ pp ) Ji but ifT pp < T GIld J pp <J, then the crack is stable.
mh1574-1w.wpf:1b/122094 7-1
WESTINGHOUSE NON-PROPRIETARY CLASS 3 7.2 Global Failure Mechanism Determination of the conditions which lead to failure in stainless steel should be done with plastic fracture methodology because of the large amount of deformation accompanying fracture.
One method for predicting the failure of ductile material is the plastic instability method, based on traditional plastic limitload concepts, but accounting for strain hardening and taking into account the presence of a flaw. The flawed pipe is predicted.to fail when the remaining net section reaches a stress level at which a plastic hinge is formed.
The stress level at which this occurs is termed as the flow stress.
The flow stress is generally taken as the average of the yield and ultimate tensile strength of the material at the temperature of interest.
This methodology has been shown to be applicable to ductile piping through a large number of experiments and will be used here to predict the critical flaw size in the primary coolant piping. The failure criterion has been obtained by requiring equilibrium of the section containing the flaw (Figure 7-1) when loads are applied.
The detailed development is provided in appendix A for a through-wall circumferential flaw in a pipe with internal pressure, axial force, and imposed bending moments.
The limit moment for such a pipe is given by:
]a,c,e where:
]
ag,e m:$ 1574-1w.wpf: 1b/122094 7-2
WESTINGHOUSE NON-PROPRIETARY CLASS 3 The analytical model described above accurately accounts for the piping internal pressure as well as imposed axial force as they affect the limitmoment.
Good agreement was found between the analytical predictions and the experimental results (Reference 7-1).
For application of the limitload methodology, the material, including consideration of the configuration, must have a sufficient ductility and ductile tearing resistance to sustain the limitload.
7.3 Results of Crack Stability Evaluation Stability analyses were performed at the critical locations established in Section 5.1.
The elastic-plastic fracture mechanics (EPFM) J-integral analyses for through-wall circumferential cracks in a cylinder were performed using the procedure in the EPRI fracture mechanics handbook (Reference 7-2).
The lower-bound material properties of Section 4.0 were applied (see Table 4-3).
The fracture toughness properties established in Section 4.3 and the normal plus SSE loads given in Table 3-2 were used for the EPFM calculations.
Evaluations were performed at the toughness critical locations identified in Section 5.1.
The results of the elastic-plastic fracture mechanics J-integral evaluations are given in Table 7-1.
The critical locations were also identified in Section 5.1. A stability analysis based on limit load was performed for these locations as described in Section 7.2.
The welds at these locations are assumed conservatively as SAW weld (SAW gives highest "Z" factor correction).
The "Z" factor correction for SAW was applied (Reference 7-3) as follows:
4 Z = 1.30 [1.0 + 0.010 (OD-4)]
where OD is the outer diameter of the pipe in inches.
The Z-factors were calculated for the critical locations, using the dimensions given in Table 3-1. The Z factor was 1.69 for locations 1 and 2. The Z factor was 1.67 for location 11.
The applied loads were increased by the Z factors and plots of limitload versus crack length were generated as shown in Figures 7-2, 7-3 and 7-4.
Table 7-2 summarizes the results of the stability analyses based on limitload.
The leakage size flaws are presented on the same table.
mh1574w.wpf: lb/122794 7-3
WESTINGHOUSE NON-PROPRIETARY CLASS 3 7.4 References 7-1.
Kanninen, M. F., et. al., "Mechanical Fracture Predictions for Sensitized Stainless Steel Piping with Circumferential Cracks," EPRI NP-192, September 1976.
7-2.
Kumar, V., German, M. D. and Shih, C. P., "An Engineering Approach for Elastic-Plastic Fracture Analysis," EPRI Report NP-1931, Project 1237-1, Electric Power Research Institute, July 1981.
7-3.
Standard Review Plan; Public Comment Solicited; 3.6.3 Leak-Before-Break Evaluation Procedtues; Federal Register/Vol. 52, No. 167/Friday, August 28, 1987/Notices, pp. 32626-32633.
mh1574-1w.wpf: 1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 7-1 Stability Results for Turkey Point Units 3 and 4 Based on Elastic-Plastic J-Integral Evaluations Fracture Criteria Flaw Size J
Location (in)
(in-lb/in )
mat Calculated Values max app app (jn-lbfjna)
(in-lb/jn )
m%1574-1w.wpf:1b/122094 7-5
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 7-2 Stability Results for Turkey Point Units 3 and 4 Based on LimitLoad Location Flaw Size in.
Leakage Flaw Size a,c,e m:51574-lw.wpf: 1b/122094 7-6
WESTINGHOUSE NON-PROPRIETARY CLASS 3 a,c,e Figure 7-1
]+~
Stress Distribution mh1574-1w.wpf: 1b/122094 7-7
WESTINGHOUSE NON-PROPRIETARY CLASS 3 a,c,e OD = 34.00 in vy = 20.47 ksi t = 2.395 in o'= 52.10 ksi F, = 1877 kips M, = 24027 in-kips A376 TP316 Material With SAW Weld Figure 7-2 Critical Flaw Size Prediction - Hot Leg at Location I mh1574-1w.wpf:1b/122094 7-8
WESTINGHOUSE NON-PROPRIETARY CLASS 3 OD = 34,00 in cry = 2344 ksi t = 2.395 in o'= 71.79 ksi F, = 1876 kips M, = 11912 in-kips A351 CF8M Material With SAW Weld Figure 7-3 Critical Flaw Size Prediction - Hot Leg at Location 2 mh1574-1w.wpf:1b/122094 7-9
WESTINGHOUSE NON-PROPRIETARY CLASS 3 OD = 32.25 in a= 24.23 ksi t = 2.27 in o'= 71.79 ksi F, = 1435 kips Mb = 8097 in-kips A351 CF8M Material With SMAW Weld Figure 7A Critical Flaw Size Prediction - Coll Leg at Location 11 m:51574-1w.wpf: 1b/122094 7-10
WESTINGHOUSE NON-PROPRIETARY CLASS 3 SECTION 8.0 FATIGUE CRACK GROWTH ANALYSIS To determine the sensitivity of the primary coolant system to the presence of small cracks, a fatigue crack growth analysis was carried out for the [
']*~'egion of a typical system (see Location [. ]*~'fFigure 3-2). This region was selected because crack growth calculated here willbe typical of that in the entire primary loop. Crack growths calculated at other locations can be expected to show less than 10% variation.
A[
]'"'fa plant typical in geometry and operational characteristics to any Westinghouse PWR System.
[
.]'
Allnormal, upset, and test conditions were considered.
A summary of generic applied transients is provided in Table 8-1. Circumferentially oriented surface flaws were postulated in the region, assuming the flaw was located in three different locations, as shown in Figure 8-1.
Specifically, these were:
Cross Section A: [
Cross Section B: [
Cross Section C:
[.
]ay,e
]Op,C Fatigue crack growth rate laws were used
[:
] "'he law for stainless steel was derived from Reference 8-1, with a very conservative correction for the R ratio, which is the ratio of minimum to maximum stress during a transient.
For stainless steel, the fatigue crack growth formula is:
= (5.4 x 10 '
K,~" inches/cycle dn where K=K (1-R)o.~
mh1574w.wpf: 1b/122794 8-1
WESTINGHOUSE NON-PROPRIETARY CLASS 3 where:
[
]ay,e where dX is the stress intensity factor range.
The calculated fatigue crack growth for semi-elliptic surface flaws of circumferential.
orientation and various depths is summarized in Table 8-2, and shows that the crack growth is very small, [
]*"'.1 References 8-1 Bamford, W. H., "Fatigue Crack Growth of Stainless Steel Piping in a Pressurized Water Reactor Environment," Trans. ASME Journal of Pressure Vessel Technology, Vol. 101, Feb. 1979.
8-2 8-3
]ay,c m:51574-1w.wpf: 1b/122094 8-2
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 8-1 Summary of Reactor Vessel Transients Number Typical Transient IdentiTication Number of Cycles 10 12 Normal Conditions Heatup and Cooldown at 100'F/hr (pressurizer cooldown 200'F/hr)
Load Follow Cycles (Unit loading and unloading at 5%
of full power/min)
Step load increase and decrease Large step load decrease, with steam dump Steady state fluctuations U set Conditions Loss of load, without immediate turbine or reactor trip Loss of power (blackout with natural circulation in the Reactor Coolant System)
Loss of Flow (partial loss of flow, one pump only)
Reactor trip from full power Test Conditions Turbine roll test Hydrostatic test conditions Primary side Primary side leak test Cold Hydrostatic test 200 18300 2000 200 106 80 40 80 400 10 5
50-10 m:51574-1w.wpf:1b/122094 8-3
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 8-2 Typical Fatigue Crack Growth at I
]+~ (40 years)
Initial Flaw (in.)
FINALFLAW(in.)
]+CO
]a,c,e 0.292 0.300 0.375 0.425 0.31097 0.31949 0.39940 0.45271 0.30107 0.30953 0.38948 OA435 0.30698 0.31626 0.40763 0.47421 mh1574-1w.wpf:1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 a,c,e Figure S-1 Typical Cross-Section of [
mh1574-1w.wpf:1b/122094 8-5
WESTINGHOUSE NON-PROPRIETARY CLASS 3 a,c,e Figure 8-2 Reference Fatigue Crack Growth Curves for [
]
QQC m%1574-1w.wpf: 1b/122094 8-6
WESTINGHOUSE NON-PROPRIETARY CLASS 3 a,c,e Figure 8-3 Reference Fatigue Crack Growth Law for t a Water Environment at 600'F mA1574-1w.wpf:1b/122094 8-7
WESTINGHOUSE NON-PROPRIETARY CLASS 3
WESTINGHOUSE NON-PROPRIETARY CLASS 3 SECTION
9.0 ASSESSMENT
OF MARGINS The results of the leak rates of Section 6.4 and the corresponding stability and fracture toughness evaluations of Sections 7.1, 7.2 and 7.3 are used in performing the assessment of margins.
Margins are shown in Table 9-1.
In summary, at all the critical locations relative to:
Flaw Size - Using faulted loads obtained by the absolute sum method, a margin of 2 or more exists between the critical flaw and the flaw having a leak rate of 10 gpm (the leakage flaw),
2.
Leak Rate - A margin of 10 exists between the calculated leak rate from the leakage flaw and the leak detection capability of 1 gpm.
3.
Loads - At the critical locations the leakage flaw was shown to be stable using the faulted loads obtained by the absolute sum method (i.e., a flaw twice the leakage flaw size is shown to be stable; hence the leakage size flaw is stable).
mh1574-1w.wpf: 1b/122094 9-1
WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 9-1 Location Leakage Flaw Sizes, Critical Flaw Sizes and Margins for Turkey Point Units 3 and 4 Leakage Flaw Size Critical Flaw Size Margin based on limitload based on J integral evaluation I:51574-lw.wpf:1b/122094 9-2
WESTINGHOUSE NON-PROPRIETARY CLASS 3 SECTION
10.0 CONCLUSION
S This report justifies the elimination of RCS primary loop pipe breaks from the structural design basis for the Turkey Point Units 3 and 4 as follows:
a.
Stress corrosion cracking is precluded by use of fracture resistant materials in the piping system and controls on reactor coolant chemistry, temperature,
- pressure, and flow during normal operation.
b.
Water hammer should not occur in the RCS piping because of system design, testing, and operational considerations.
c.
The effects of low and high cycle fatigue on the integrity of the primary piping are negligible.
d.
Ample margin exists between the leak rate of small stable flaws and the capability of the Turkey Point Units 3 and 4 reactor coolant system pressure boundary Leakage Detection System.
e.
Ample margin exists between the small stable flaw sizes of item d and larger stable flaws.
f.
Ample margin exists in the material properties used to demonstrate end-of-service life (relative to aging) stability of the critical flaws.
For the critical locations flaws are identified that willbe stable because of the ample margins described in d, e, and f above.
Based on the above, it is concluded that dynamic effects of RCS primary loop pipe breaks need not be considered in the structural design basis of the Turkey Point Units 3 and 4 Nuclear, Power Plants.
iK41574-1w.wpf:1b/122094 10-1
WESTINGHOUSE NON-PROPRIETARY CLASS 3
WESTINGHOUSE NON-PROPRIETARY CLASS 3 APPENDIX A LIMITMOMENT
]ac,e mh1574-1w.wpf:1b/122094 A-1
WESTINGHOUSE NON-PROPRIETARY CLASS 3 a,c,e Figure A-1 Pipe with a Through-Wall Crack in Bending m:51574-1w.wpf: 1b/122094 A-2
WESTINGHOUSE NON-PROPRIETARY CLASS 3 APPENDIX B TOUGHNESS CRITERIA FOR TURKEYPOINT UNITS 3 AND 4 CAST PRIMARYLOOP COMPONENTS Allof the individual cast piping components of the Turkey Point Units 3 and 4 primary loops, do not satisfy the original [
]"'riteria (Reference 4-5). [
m%1574-lw.wpf: 1b/122094 B-1
Table B Chemistry and Fracture Toughness Properties of the Material Heats of Turkey Point Units 3 and 4 a,c,e 0
0 A
1w.wpf:1b/122094
WESTINGHOUSE NON-PROPRIETARY CLASS 3 m:41574-1w.wpf: 1b/122094 B-3