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ENCLOSURE 8 TO AEP-NRC-2018-02

WCAP-18302-NP, Revision O "Technical Justification for Eliminating Residual Heat Removal Line Rupture as the Structural Design Basis for D.C. Cook Units 1 and 2, Using Leak-Before

Break Methodology" (Non-Proprietary)

WCAP-18302-NP Revision 0

WESTINGHOUSE NON-PROPRIETARY CLASS 3

January 2018

Technical Justification for Eliminating Residual Heat Removal Line Rupture

. . . . . . . . . . . . .

as the Structural Design Basis for D.C. Cook Units 1 and 2, Using Leak-Before-Break Methodology

@Westinghouse

*** This record was final approved on 1/18/2018 9:39:42 AM. ( This statement was added by the PRIME system upon its validation)

-I


WCAP-18302-NP Revision 0

Technical Justification for Eliminating Residual Heat Removal Line Rupture as the Structural

Design Basis for D.C. Cook Units 1 and 2, Using Leak-Before-Break Methodology

, January 2018

Author: Eric D. Johnson* Structural Design and Analysis - II

Reviewer: Momo Wiratmo* Structural Design and Analysis - II

Approved: Benjamin A. Leber, Manager* Structural Design an4 AnaJysis ~ II

*Electronically approved records are authenticated in the electronic document management system.

Westinghouse Electric Company LLC 1000 Westinghouse Drive

Cranberry Township, PA 16066, USA

© 2018 Westinghouse Electric Company LLC All Rights Reserved


WESTINGHOUSE NON-PROPRIETARY CLASS 3 lll

TABLE OF CONTENTS

1.0 Introduction .............................................................. · ..................................................................... 1-1 1.1 Purpose ............................................................................................................................ 1-1 1.2 Scope and Objectives ....................................................................................................... 1-1 1.3 References ........................................................................................................................ 1-2

2.0 Operation and Stability of the Reactor Coolant System ............................................................... 2-1 2.1 Stress Corrosion Cracking ............................................................................................... 2-1 2.2 Water Hammer ................................................................................................................. 2-2 2.3 Low Cycle and High Cycle Fatigue ................................................................................. 2-2 2.4 Other Possible Degradation During Service of the RHR Lines ....................................... 2-3 2.5 References ........................................................................................................................ 2-4

3.0 Pipe Geometry and Loading ......................................................................................................... 3-1 3.1 Calculations of Loads and Sfresses ................................................. : ........................ : ....... 3-1 3.2 Loads for Leak Rate Evaluation ...................................................................................... 3-1 3.3 Load Combination for Crack Stability Analyses ............................................................. 3-2 3.4 References ........................................................................................................................ 3-3

4.0 Material Characterization .............................................................................................................. 4-1 4.1 RHR Line Pipe Material and Weld Process .................................................................... .4-1 4.2 Tensile Properties ............................................................................................................. 4-1 4.3 Reference ......................................................................................................................... 4-1

5.0 . Critical L_ocations ... , ................. , ................. , .......................................... , ........ _. ....... , ........ _. ....... , ........ 5-1 .5.1 Critical Locations ............................................................................................................. 5-1

6.0 Leak Rate Predictions ................................................................................................................... 6-1 6.1 Introduction ...................................................................................................................... 6-1 6.2 General Considerations .................................................................................................... 6-1 6.3 Calculation Method .......................................................................................................... 6-1 6.4 Leak Rate Calculations .................................................................................................... 6-2 6.5 References ........................................................................................................................ 6-3

7.0 Fracture Mechanics Evaluation ..................................................................................................... 7-1 7.1 Global Failure Mechanism ............................................................................................... 7-1 7.2 Results of Crack Stability Evaluation ........................... , .................................................. 7-2 7.3 References ........................................................................................................................ 7-2

8.0 Assessment of Fatigue Crack Growth ........................................................................................... 8-1 8.1 References ........................................................................................................................ 8-1

9 .0 Assessment of Margins ................................................................................................................. 9-1

10.0 Conclusions ....................................... : .......................................................................................... 10-1

Appendix A: Limit Moment. .................................................................................................................... A-1

WCAP-18302-NP January 2018 Revision 0


WESTINGHOUSE NON-PROPRIETARY CLASS 3 IV

LIST OF TABLES

Table 3-1 Summary ofD.C. Cook Units 1 and 2 Piping Geometry and Normal Operating Condition for 14-inch RHR Suction Lines and 8-inch RHR Return Lines ........................... 3-4

Table 3-2 Summary ofD.C. Cook Unit 1 Normal Loads and Stresses 14-inch RHR Suction Lines and 8-inch RHR Return Lines ..................................................................................... 3-5

Table 3-3 Summary ofD.C. Cook Unit 2 Normal Loads and Stresses 14-inch RHR Suction Lines and 8-inch RHR Return Lines ..................................................................................... 3-7

Table 3-4 Summary of D.C. Cook Unit 1 Faulted Loads and Stresses 14-inch RHR Suction Lines and 8-inch RHR Return Lines ..................................................................................... 3-9

Table 3-5 Summary ofD.C. Cook Unit 2 Faulted Loads and Stresses 14-inch RHR Suction Lines and 8-inch RHR Return Lines ...... ; ................ ; ................ ; ................ ; ................ ; ........ 3-11 ·

Table 4-1 Material Properties for Operating Temperature Conditions on D.C. Cook Units 1 and 2 RHR Lines ................................................................................................................... 4-2

Table 5-1 Critical Analysis Location for Leak-Before-Break ofD.C. Cook Units 1 and 2 RHR Lines ..................................................................................................................................... 5-1

Table 6-1 Flaw Sizes Yielding a Leak Rate of 8 gpm for the D.C. Cook Units 1 and 2 RHR Lines ..................................................................................................................................... 6-4

Table 7-1 Flaw St~bility Results for the D.C Cook Units 1 a.nd 2 RHR Unes Based on Umit . Load ...................................................................................................................................... 7-3

Table 9-1 Leakage Flaw Sizes, Critical Flaw Sizes, and Margin for the D.C. Cook Units 1 and 2 RHR Lines ................................................................................................................... 9-2



Figure 3-1

Figure 5-1

Figure 5-2

Figure 5-3

Figure 5-4

Figure 6-1

Figure 6-2

Figure 6-3

Figure 7-1

FigureA-1


LIST OF FIGURES

D.C. Cook Units 1 and 2 Typical Piping Layout for RHR Lines ................................... 3-13

D.C. Cook Unit 1 RHR Suction Line Loop 2 Critical Weld Locations ........................... 5-2

D.C. Cook Unit 1 RHR Return Line Loops 2 and 3 Critical Weld Locations ................. 5-3

D.C. Cook Unit 2 RHR Suction Line Loop 2 Critical Weld Locations ..................... , ..... 5-4

D.C. Cook Unit 2 RHR Return Line Loops 2 and 3 Critical Weld Locations ................. 5-5

Analytical Predictions of Critical Flow Rates of Steam-Water Mixtures ........................ 6-5

[ ]",c,e Pressure Ratio as a Function of LID ....................................... 6-6

. Idealized Pressure Drop Profile Through a Postulated Crack .... :······ .. :·······:················:···6-7

]",c,e Stress Distribution ............................................................................ 7-4

Pipe with a Through-Wall Crack in Bending .................................................................. A-2

V



WESTINGHOUSE NON-PROPRIETARY CLASS 3 1-1

1.0 INTRODUCTION

1.1 PURPOSE

The current structural design basis for the D.C. Cook Units 1 and 2 Residual Heat Removal (RHR) lines, including the 14-inch suction lines attached to the Loop 2 hot leg and the 8-inch return lines attached to the Loop 2 and Loop 3 Accumulator lines, require postulating non-mechanistic circumferential and longitudinal pipe breaks. This results in additional plant hardware ( e.g., pipe whip restraints and jet shields) which would mitigate the dynamic consequences of the pipe breaks. It is, therefore, highly desirable to be realistic in the postulation of pipe breaks for the RHR lines. Presented in this report are the descriptions of a mechanistic pipe break evaluation method and the analytical results that can be used for establishing that a circumferential type of break will not occur within the RHR lines. The evaluations consider that circumferentially oriented flaws cover longitudinal cases.

1.2 SCOPE AND OBJECTIVES

The purpose of this investigation is to demonstrate Leak-Before-Break (LBB) for the D.C. Cook Units 1 and 2 RHR suction lines from the hot leg piping of Loop 2 up to the second isolation valve away from the hot leg and the RHR return lines from the 10-inch Accumulator lines to the first check valve. Schematic drawing of the piping systems are shown in Section 3 .0, Figure 3-1. The recommendations and criteria proposed in SRP 3.6.3 (References 1-1 and 1-2) are used in this evaluation. The criteria and the resulting steps of the evaluation procedure can be briefly summarized as follows:

1. Calculate the applied loads based on as-built configuration. Identify the location(s) at which the highest faulted stress occurs.

2. Identify the materials and the material properties.

3. Postulate a through-wall flaw at the governing location(s). 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 normal operating loads. Demonstrate that there is a margin of 10 between the calculated leak rate and the leak detection capability.

4. Using maximum faulted loads in the stability analysis, demonstrate that there is a margin of 2 between the leakage size flaw and the critical size flaw.

5. 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.

6. For the material types used in the plant, provide representative material properties.

7. Demonstrate margin on applied load by combining the faulted loads by absolute summation method.

Introduction WCAP-18302-NP

January 2018 Revision 0



This report provides a fracture mechanics demonstration of RHR line piping integrity for D.C. Cook Units 1 and 2 consistent with the NRC's position for exemption from consideration of dynamic effects (Reference 1-3).

It should be noted that the terms "flaw" and "crack" have the same meaning and are used interchangeably. "Governing location" and "critical location" are also used interchangeably throughout the report.

1.3 REFERENCES

1-1 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.

1-2 NUREG-0800 Revision 1, March 2007, Standard Review Plan: 3.6.3 Leak-Before-Break · Evaluation Procedures.

1-3 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.

Introduction WCAP-18302-NP


*** This record was ·final approved on 1/18/2018 9:39:42 AM. ( This statement was added by the PRIME system upon its validation)


2.0 OPERATION AND STABILITY OF THE REACTOR COOLANT SYSTEM

2.1 STRESS CORROSION CRACKING

The Westinghouse reactor coolant system (RCS) primary loops and connected Class 1 piping 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 1400 reactor-years, including 16 plants each having over 30 years of operation, 10 other plants each with over 25 years of operation, 11 plants each with over 20 years of operation and 12 plants each with over 15 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 (PWRs). The results of the study performed by the PCSG were presented in NUREG-0531 (Reference 2-1) entitled "Investigation and Evaluation of Stress Corrosion 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."

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, sulfites, 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.

Operation and Stability of the Reactor Coolant System WCAP-18302-NP




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 parts per billion (ppb) range by controlling charging flow chemistry and maintaining hydrogen in the reactor coolant at specified concentrations. Halogen concentrations are also stringently controlled by maintaining concentrations of chlorides and fluorides within the specified limits. Thus during plant operation, the likelihood of stress corrosion cracking is minimized.

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 ofIGSCC have been reported for PWR primary coolant systems.

Primary Water Stress Corrosion Cracking (PWSCC) occurred in the V. C. Summer reactor vessel hot leg nozzle, Alloy 82/182 weld. It should be noted that this susceptible material is not found at the D.C. Cook Units 1 and 2 RHR lines.

2.2 WATERHAMMER

. . . . . . . . . . . .

Overall, there is a low potential for water hammer in the RCS and connecting RHR lines since they are designed and operated to preclude the voiding condition in normally filled lines. The RCS and connecting RHR lines including piping and components are 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 dynamic loads. To ensure dynamic system stability, reactor coolant parameters are stringently controlled. Temperature during normal operation is maintained within a narrow range by the control rod positions; pressure is also controlled within a narrow range for steady-state conditions by the pressurizer heaters and pressurizer spray. 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 and the connecting auxiliary lines. Preoperational testing and operating experience has verified the Westinghouse approach. The operating transients of the RCS primary piping and connected RHR lines are such that no significant water hammer can occur.

2.3 LOW CYCLE AND HIGH CYCLE FATIGUE

The 1967 edition of the B3 l.1 Code does not contain an explicit piping low cycle fatigue analysis requirement. The B31.1 piping complies with a stress range reduction factor to be applied to the allowable stress as a way to address fatigue from full temperature cycles for thermal expansion stress evaluation. The stress range reduction factor is 1.0 (i.e., no reduction) for equivalent full temperature





cycles less than 7000. For D.C. Cook Units 1 and 2, the equivalent full temperature cycles for the applicable design transients are less than 7000, so no reduction is required.

Pump vibrations during operation would result in high cycle fatigue loads in the piping system. During operation, an alarm signals the exceedance of the RC pump shaft vibration limits. Field vibration measurements have been made on the reactor coolant loop piping in a number of plants during hot functional testing. Stresses in the elbow below the RCP have been found analytically to be very small, between 2 and 3 ksi at the highest. Field measurements on a typical PWR plant indicate vibration stress amplitudes less than 1 ksi. When translated to the connecting RHR lines, these stresses would be even lower, well below the fatigue endurance limit for the RHR line materials and would result in an applied stress intensity factor below the threshold for fatigue crack growth.

2.4 OTHER POSSIBLE DEGRADATION DURING SERVICE OF THE RHR LINES

Thermal stratification occurs when conditions permit hot and cold layers of water to exist simultaneously in a horizontal pipe. This can result in significant thermal loadings due to the high fluid temperature differentials. Changes in the stratification state result in thermal cycling, which can cause fatigue damage. This was an important issue in PWR feedwater line and pressurizer surge line piping, where temperature differentials of 300°F were not uncommon.

The issue of RHR valve leakage described in NRC Bulletin 88-08, Supplement 3 (Reference 2-3) identifies a scenario that could lead to stratification conditions which would jeopardize piping integrity .

. WCAP-12143_(Referenc~ 2-4) identifies_three auxiUary piping systems for D_.C. Cook Units 1 and 2 that are susceptible to the valve leakage and the potential stratification detailed in Bulletin 88-08. The RHR lines are not identified as one of the three susceptible lines.

The RHR lines and the associated fittings for the D.C. Cook Nuclear Power Plants are forged product forms, which are not susceptible to toughness degradation due to thermal aging.

The maximum normal operating temperature of the RHR piping is about 617°F. This is well below the temperature that would cause any creep damage in stainless steel piping. Cleavage type failures are not a concern for the operating temperatures and the material used in the stainless steel piping of the RHR lines.

Wall thinning by erosion and erosion-corrosion effects should not occur in the RHR piping due to the low velocity, typically less than 1.0 ft/sec and the stainless steel material, which is highly resistant to these degradation mechanisms. Per NUREG-0691 (Reference 2-2), a study on pipe cracking in PWR piping reported only two incidents of wall thinning in stainless steel pipe and these were not in the RHR lines. The cause of wall thinning is related to high water velocity and is therefore clearly not a mechanism that would affect the RHR piping.

Brittle fracture for stainless steel material occurs when the operating temperature is about -200°F. RHR line operating temperature is higher than 120°F and therefore, brittle fracture is not a concern for the RHR lines.





2.5 REFERENCES

2-1 Investigation and Evaluation of Stress-Corrosion Cracking in Piping of Light Water 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.

2-3 NRC Bulletin 88-08, Supplement 3, "Thermal Stresses in Piping Connected to Reactor Coolant Systems" April 11, 1989.

2-4 WCAP-12143, Revision O and Supplement 1, "Report on Evaluation of Auxiliary Piping attached to the Reactor Coolant System per NRC Bulletin 88-08 for American Electric Power Service Corporation D. C. Cook Units 1 and 2," April 1989.





3.0 PIPE GEOMETRY AND LOADING

3.1 CALCULATIONS OF LOADS AND STRESSES

The stresses due to axial loads and bending moments are calculated by the following equation:

where,

(J

F

stress, psi

axial load, lbs

F M (J =-+

A Z

M moment, in-lbs

A

z

pipe cross-sectional area, in2

section modulus, in3

The moments for the desired loading combinations are calculated by the following equation:

M =JM2 +M 2 +M2 X y Z

where,

X component of moment, Torsion

Y component of bending moment

M 2 Z component of bending moment

3-1

(3-1)

(3-2)

The axial load and moments for leak rate predictions and crack stability analyses are computed by the

methods to be explained in Sections 3.2 and 3.3.

3.2 LOADS FOR LEAK RATE EVALUATION

The normal operating loads for leak rate predictions are calculated by the following equations:

F = Fow + Frn + Fp (3-3)

Mx = (Mx)ow + (Mx)rn (3-4)

Mv = (Mv)ow + (Mv)rn (3-5)

Mz (Mz)ow + (Mz)rn (3-6)

Pipe Geometry and Loading January 2018 WCAP-18302-NP Revision 0



The subscripts of the above equations represent the following loading cases:

DW =

TH

p

dead weight

normal thermal expansion

load due to internal pressure

3-2

This method of combining loads is often referred to as the algebraic sum method (References 3-1 and 3-2). The LBB evaluations do not include moment effects due to pressure loading since the moment loading is significantly dominated by the thermal loads for nonnal operation and by the seismic loads for faulted events.

The dimensions and normal operating conditions are given in Table 3-1. The loads based on this method of combination are provided in Tables 3-2 and 3-3 at all the weld locations. The weld naming convention used in this report is as follows:

Unit# - Sl(2/4/6/8) - Isometric # - Spool Sheet # -Analysis Node #

where: SI2 - Unit 1 RHR return lines SI4 - Unit 1 RHR suction line SI6 - Unit 2 RHR return lines SI8 - Unit 2 RHR suction line

3.3 LOAD COMBINATION FOR ·cRAcK ·sTABILiTY ANALYSES

In accordance with Standard Review Plan 3.6.3 (References 3-1 and 3-2), the absolute sum of loading components can be applied which results in higher magnitude of combined loads. If crack stability is demonstrated using these loads, the LBB margin on loads can be reduced from -V2 to 1.0. The absolute summation of loads is shown in the following equations:

F = I F DW I + I F TH I + I F p I + I F SSEINERTIA I + I F SSEAM I

Mx = I (Mx)nw I + I (Mx)m I + I (Mx)ssEINERnAI + I (Mx)ssEAMI

My= I (My)nw I+ I (My)m I+ I (My)ssEINERnAI + I (My)ssEAMI

Mz = I (Mz)nw I + I (Mz)m I + I (Mz)ssEINERTIAI + I (Mz)ssEAMI

(3-7)

(3-8)

(3-9)

(3-10)

where subscript SSEINERTIA refers to safe shutdown earthquake inertia, SSEAM is safe shutdown earthquake anchor motion. It is noted that the D.C. Cook piping analyses consider Design Basis Earthquake (DBE) as the seismic criteria, which is equivalent to Safe Shutdown Earthquake (SSE).

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 weld locations are given in Tables 3-4 and 3-5.

Pipe Geometry and Loading WCAP-18302-NP




Notes: For the RHR suction lines attached to the Loop 2 hot leg, the LBB analysis will not be performed at the locations beyond the second isolation valve away from the hot leg. Two isolation valves will prevent the propagation of any piping breaks in the subsequent RHR piping from affecting the primary loop piping system. For the RHR return lines attached to the Loop 2 and Loop 3 Accumulator lines, the LBB analysis will not be performed at the locations beyond the first check valve away from the Accumulator lines. Two check valves, one on the RHR return line and one on the Accumulator line, will prevent the propagation of any piping breaks in the subsequent RHR return piping from affecting the primary loop piping system. Figure 3-1 illustrates the typical layout of the 14-inch RHR suction line and the 8-inch RHR return line, showing segments, for D.C. Cook Units 1 and 2.

3.4 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.

3-2 NUREG-0800 Revision 1, March 2007, Standard Review Plan: 3.6.3 Leak-Before-Break Evaluation Procedures.





Table 3-1 Summary ofD.C. Cook Units 1 and 2 Piping Geometry and Normal Operating Condition for 14-inch RHR Suction Lines and 8-inch RHR Return Lines

Pipe Minimum Normal Operating

Loop Segment Weld Location Outside Wall

Nodes Diameter Thickness Pressure Temperature

(in) (in) (psig) {°F)

RHRs-1 start: 288

14.000 1.251 2235 617 end: 282 2

276 RHRs-11

start: 14.000 1.251 450 120 end: 244

2 RHRr2-I start: 324

8.625 0.731 2235 120 end: 320

3 RHRr3-I start: 196

8.625 0.731 2235 120 end: 242

Notes: Figure 3-1 shows the piping layout and segments. Figures 5-1 through 5-4 show the weld locations for each line analyzed. Material type isA376 TP316 or A403 WP316. Piping in segment RHRs-1 and RHRs-11 is 14-inch Schedule 160. Piping in segment RHRr2-I and RHRr3-I is 8-inch Schedule 140. The minimum wall thickness is conservatively based at the weld counterbore and not per ASME Code requirement.





Table 3-2 Summary ofD.C. Cook Unit 1 Normal Loads and Stresses 14-inch RHR Suction Lines and 8-inch RHR Return Lines

Segment Weld Location

Node

1-SI4-1RH29-1RH29l-288

1-SI4-1RH29-1RH291-288-2

1-SI4-1RH29-1RH291-284F RHRs-1

1-SI4-1RH29-1RH291-284F-2

1-SI4-1RH29-1RH291-282

1-SI4-1RH29-1RH29l-282-2

1-SI4-1RH28-1RH28 iA-276

1-SI4-1RH28-1RH281A-276-2

1-SI4-1RH28-1RH281A-274F

1-SI4-1RH28-1RH281A-274F-2

1-SI4-1RH28-1RH281A-268F

1-SI4-1RH28-1RH281A-268F-2

1-SI4-1RH28-1RH281A-268N

1-SI4~ 1RH.28-11_lli28JA-268N-2

1-SI4-1RH28-1RH281B-267

1-SI4-1RH28-1RH281B-267-2

1-SI4-1RH28-1RH281-262N

1-SI4-1RH28-1RH281-262N-2

1-SI4-1RH28-1RH281-260F RHRs-11

1-SI4-1RH28-1RH281-260F-2

1-SI4-1RH28-1RH282-260N

1-SI4-1RH28-1RH282-260N-2

1-SI4-1RH28-1RH282-254F

1-SI4-1RH28-1RH282-254F-2

1-SI4-1RH28-1RH283-250N

1-SI4-1RH28-1RH283-250N-2

1-SI4-1RH28-1RH283-248F

1-SI4-1RH28-1RH283-248F-2

1-SI4-1RH28-1RH283-248N

1-SI4-1RH28-1RH283-248N-2

1-SI4-1RH28-1RH283-244

1-SI4-1RH28-1RH283-244-2


Axial Force (lbs)

230,556

232,511

231,852

232,109

235,831

228,341

50,474

42,989

50,469

42,989

44,340

48,773

47,578

. 45,889

47,568

45,889

47,370

46,088

47,370

46,080

63,793

29,659

46,788

46,669

42,648

50,382

43,620

49,227

46,580

46,878

46,580

46,878

Moment (in-lbs)

699,382

699,382

360,328

360,328

346,413

346,413

762,648

762,648

1,062,735

1,062,735

1,268,232

1,268,232

1,059,750

. 1,05.9,750

598,178

598,178

272,039

272,039

1,049,556

1,049,556

1,304,695

1,304,695

14,793

14,793

21,003

21,003

27,593

27,593

33,640

33,640

139,155

139,155

Total Stress (psi)

9,366

9,405

7,083

7,088

7,067

6,918

6,202

6,053

8,246

8,097

9,524

9,612

8,168

8,135

5,024

4,991

2,799

2,773

8,095

8,069

10,161

9,479

1,035

1,032

994

1,149

1,059

1,171

1,159

1,165

1,878

1,884




Table 3-2 (continued)

Segment Weld Location Axial Force Node (lbs)

1-SI2-1RH27-1RH275-324Z 89,111

1-SI2-1RH27-1RH275-324Z-2 91,022

1-SI2-1RH27-1RH275-322F 89,108

1-SI2-1RH27-1RH275-322F-2 91,022 RHRr2-I

1-SI2-1RH27-1RH275-322N 88,199

1-SI2-1RH27-1RH275-322N-2 91,844

1-SI2-1RH27-1RH275-320 88,410

l-SI2-1RH27-1RH275-320-2 91,578

1-SI2-1Sl33-1Sl331A-196Z 89,318

1-SI2-1 Sl33-1 SI331A-196Z-2 90,811

1-SI2-1 Sl33-1 Sl331A-240N 89,319

1-SI2-l Sl33-1 Sl331A-240N-2 90,811 RHRr3-I

1-SI2-1 Sl33-1 Sl331A-240F 92,904

1-SI2-1S133-1Sl331A-240F-2 87,433

1~SI2-1Sl33-1Sl331A~242 . 92,697

1-SI2-1 Sl33-1 Sl331A-242-2 87,580

Notes: See Figures 3-1, 5-1, and 5-2 for piping layout. Axial force includes pressure.


Moment (in-lbs)

36,936

36,936

46,442

46,442

60,659

60,659

37,485

37,485

106,270

106,270

100,023

100,023

78,025

78,025

. 57,708

57,708

3-6

Total Stress (psi)

6,034

6,139

6,322

6,427

6,702

6,903

6,012

6,187

8,145

8,227

7,956

8,038

7,487

7,186

6,861

6,578




Table 3-3 Summary ofD.C. Cook Unit 2 Normal Loads and Stresses 14-inch RHR Suction Lines and 8-inch RHR Return Lines


Node

2-S18-2Rl-I331-2Rl-I331-288

2-S18-2Rl-I331-2Rl-I331-288-2

2-SI8-2Rl-I331-2Rl-I331-284F Rl-IRs-I

2-SI8-2Rl-I331-2Rl-I33l-284F-2

2-SI8-2Rl-I331-2Rl-I331-282

2-S18-2Rl-I331-2Rl-I33l-282-2

2-SI8-2Rl-I331-1Rl-I281R-276

2-SI8-2Rl-I33 l-1Rl-I281R-276-2

2-SI8-2Rl-I331-1Rl-I281R-274F

2-SI8-2Rl-I331-1Rl-I281R-274F-2

2-SI8-2Rl-I33l-1Rl-I281AA-268F

2-S18-2Rl-I331-1Rl-I281AA-268F-2

2-SI8-2Rl-I331-1Rl-I281AA-268N

2-SI8-2Rl-I331-1Rl-I281AA-268N~2

2-SI8-2Rl-I331-2Rl-I333-267

2-SI8-2Rl-I331-2Rl-I333-267-2

2-SI8-2Rl-I33 l-1Rl-I292R-262N

2-SI8-2Rl-I331-1Rl-I292R-262N-2

Rl-IRs-II 2-SI8-2Rl-I331-1Rl-I292R-260F

2-SI8-2Rl-I331-1Rl-I292R-260F-2

2-SI8-2Rl-I331-1Rl-I292AR-260N

2-SI8-2Rl-I331-1Rl-I292AR-260N-2

2-S18-2Rl-I332-2Rl-I336-254F

2-SI8-2Rl-I332-2Rl-I336-254F-2

2-S18-2Rl-I332-2Rl-I336-250N

2-SI8-2Rl-I332-2Rl-I336-250N-2

2-SI8-2Rl-I332-2Rl-I337-248F

2-SI8-2Rl-I332-2Rl-I337-248F-2

2-SI8-2Rl-I332-2Rl-I335-248N

2-SI8-2Rl-I332-2Rl-I335-248N-2

2-SI8-2Rl-I332-2Rl-I335-244

2-SI8-2Rl-I332-2Rl-I335-244-2


Axial Force (lbs)

228,175

235,725

228,642

235,320

232,120

232,054

46,762

46,697

46,761

46,703

43,134

49,963

49,509

.43,939

49,514

43,942

44,818

48,641

44,820

48,631

57,206

36,251

46,777

46,681

42,699

50,308

43,722

49,093

46,614

46,844

46,614

46,844

Moment (in-lbs)

383,620

383,620

291,246

291,246

397,780

397,780

706,267

706,207

895,956

895,956

1,026,326

1,026,326

891,786

S91,7.86

439,237

439,238

324,771

324,771

904,410

904,410

1,115,229

1,115,229

22,672

22,672

18,273

18,273

24,173

24,174

27,155

27,155

117,499

117,499

Total Stress (psi)

7,168

7,319

6,548

6,681

7,343

7,342

5,744

5,743

7,036

7,035

7,852

7,988

7,063

. 6,952

3,980

3,869

3,107

3,183

7,055

7,131

8,739

8,320

1,088

1,086

977

1,129

1,037

1,145

1,115

1,120

1,731

1,735





Segment Weld Location Axial Force

Node (lbs)

2-SI6-2RH32-2RH322-324Z 88,963

2-SI6-2RH32-2RH322-324Z-2 91,168

2-SI6-2RH32-2RH322-322F 88,962

2-SI6-2RH32-2RH322-322F-2 91,169 RHRr2-I

2-SI6-2RH32-2RH322-322N 88,590

2-SI6-2RH32-2RH322-322N-2 91,333

2-SI6-2RH32-2RH322-320 88,797

2-SI6-2RH32-2RH322-320-2 91,187

2-SI6-2SI582-2SI584-196Z 91,158

2-SI6-2SI582-2SI584-196Z-2 88,977

2-SI6-2SI582-2SI584-240N 91,154

2-SI6-2SI582-2SI5 84-240N-2 88,974 RHRr3-I

2-SI6-2SI582-2SI584-240F 90,660

2-SI6-2Sl582-2SI584-240F-2 89,678

2-SI6-2SI5 82-2SI5 84-242 90,453

2-SI6-2SI582-2SI584-242-2 89,824



Moment (in-lbs)

90,235

90,235

70,915

70,915

53,578

53,578

12,570

12,570

54,601

54,601

56,682

56,682

47,211

47,211

31,158

31,158

3-8

Total Stress (psi)

7,640

7,761

7,055

7,176

6,509

6,660

5,279

5,411

6,682

6,561

6,744

6,624

6,430

6,376

5,933.

5,898




Table 3-4 Summary ofD.C. Cook Unit 1 Faulted Loads and Stresses 14-inch RHR Suction Lines and 8-inch RHR Return Lines


Node

1-SI4-1RH29-1RH291-288

1-SI4-1RH29-1RH291-288-2

1-SI4-1RH29-1RH291-284F RHRs-I

1-SI4-1RH29-1RH291-284F-2

1-SI4-1RH29-1RH291-282

1-SI4-1RH29-1RH291-282-2

1-SI4-1RH28-1RH281A-276

1-SI4-1RH28-1RH281A-276-2

1-S14-1RH28-1RH281A-274F

1-SI4-1RH28-1RH281A-274F-2

1-S14-1RH28-1RH281A-268F

1-S14-1RH28-1RH281A-268F-2

1-S14-1RH28-1RH281A-268N

. 1-SI4-1RI,--I28-lRH281A-268N~2

1-SI4-1RH28-1RH281B-267

1-S14-1RH28-1RH281B-267-2

1-SI 4-1 RH28-1 RH281-262N

1-SI4-1RH28-1RH281-262N-2

1-SI4-1RH28-1RH281-260F RHRs-II

1-SI4-1RH28-1RH281-260F-2

1-S14-1RH28-1RH282-260N

1-SI4-1RH28-1RH282-260N-2

1-SI4-1RH28-1RH282-254F

1-SI4-1RH28-1RH282-254F-2

1-SI4-1RH28-1RH283-250N

1-SI4-1RH28-1RH283-250N-2

1-SI4-1RH28-1RH283-248F

1-SI4-1RH28-1RH283-248F-2

1-SI4-1RH28-1RH283-248N

1-SI4-1RH28-1RH283-248N-2

1-SI4-1RH28-1RH283-244

1-SI4-1RH28-1RH283-244-2


Axial Force (lbs)

244,752

243,643

243,350

243,109

238,703

238,652

52,222

52,208

52,198

52,182

55,231

54,855

50,327

50,182 .

50,171

50,042

48,500

48,388

48,740

48,814

65,913

65,927

48,552

48,551

53,271

52,826

52,239

51,611

51,733

51,193

50,141

49,988

Moment (in-lbs)

974,990

974,953

578,790

578,673

544,473

544,447

96i,545

961,528

1,318,421

1,317,136

1,538,243

1,538,024

1,287,274

1,286,64.6

732,799

732,946

428,833

435,537

1,323,316

1,324,376

1,617,843

1,616,904

218,111

217,992

169,025

167,181

272,126

264,539

293,720

293,028

224,288

224,256

Total Stress (psi)

11,527

11,505

8,800

8,795

8,474

8,472

7,592

7,592

10,023

10,014

11,581

11,572

9,773

9,766.

5,993

5,992

3,889

3,933

9,987

9,996

12,336

12,330

2,455

2,454

2,215

2,193

2,896

2,832

3,033

3,018

2,529

2,525





Segment Weld Location Axial Force Node (lbs)

1-SI2-1RH27-1RH275-324Z 95,150

1-SI2-1RH27-1RH275-324Z-2 95,125

1-SI2-1RH27-1RH275-322F 95,126

1-SI2-1RH27-1RH275-322F-2 95,092 RHRr2-I

1-SI2-1RH27-1RH275-322N 96,482

1-SI2-1RH27-1RH275-322N-2 96,373

1-SI2-1RH27-1RH275-320 96,218

1-SI2-1RH27-1RH275-320-2 96,037

1-SI2-1 SI33-1 SI331A-196Z 94,109

l-SI2-1 SI33-1 SI331A-196Z-2 94,104

1-SI2-1 SI33-1 SI331A-240N 94,103

1-SI2-1SI33-1SI331A-240N-2 94,091 RHRr3-I

1-SI2-1 SI33-1 SI331A-240F 94,627

1-SI2-1SI33-1SI331A-240F-2 94,398

1-SI2- l SI33-1 SI331A-242 . 94,384

1-SI2- l SI33-1 SI331A-242-2 94,225



Moment (in-lbs)

333,949

334,065

236,187

236,153

247,073

241,023

99,135

99,122

526,381

526,364

512,976

512,917

393,956

361,314

159,293 .

159,441

3-10

Total Stress (psi)

15,361

15,363

12,399

12,396

12,803

12,614

8,309

8,299

21,130

21,129

20,724

20,721

17,149

16,148

10,030 .

10,025




Table 3-5 Summary ofD.C. Cook Unit 2 Faulted Loads and Stresses 14-inch RHR Suction Lines and 8-inch RHR Return Lines


Node

2-SI8-2RH331-2RH33l-288

2-SI8-2RH331-2RH331-288-2

2-SI8-2RH331-2RH331-284F RHRs-1

2-SI8-2RH33l-2RH331-284F-2

2-SI8-2RH331-2RH331-282

2-SI8-2RH331-2RH331-282-2

2--SI8-2RH331-1RH28iR-276

2-SI8-2RH331-1RH281R-276-2

2-SI8-2RH331-1RH281R-274F

2-SI8-2RH331-1RH281R-274F-2

2-SI8-2RH331-1RH281RA-268F

2-SI8-2RH331-1RH281RA-268F-2

2-SI8-2RH331-1RH281RA-268N

2:-SI8-2RH331-1RH281RA~268N-2

2-SI8-2RH331-2RH333-267

2-SI8-2RH331-2RH333-267-2

2-SI8-2RH331-1RH292R-262N

2-SI8-2RH331-1RH292R-262N-2

2-Sl8-2RH331-1 RH292R-260F RHRs-11

2-SI8-2RH331-1RH292R-260F-2

2-SI8-2RH33 l-1RH292AR-260N

2-SI8-2RH331-1RH292AR-260N-2

2-SI8-2RH332-2RH336-254F

2-SI8-2RH332-2RH336-254F-2

2-SI8-2RH332-2RH336-250N

2-SI8-2RH332-2RH336-250N-2

2-SI8-2RH332-2RH337-248F

2-SI8-2RH332-2RH337-248F-2

2-SI8-2RH332-2RH335-248N

2-SI8-2RH332-2RH335-248N-2

2-SI8-2RH332-2RH335-244

2-SI8-2RH332-2RH335-244-2


Axial Force (lbs)

242,226

241,963

241,606

241)37

237,101

237,021

50,375

50,366

50,349

50,338

55,438

55,019

54,014

53,909

53,754

53,628

51,615

51,445

51,557

51,652

61,221

61,240

47,914

47,871

52,874

52,410

51,765

51,112

52,008

51,503

50,221

50,097

Moment (in-lbs)

767,713

767,586

533,972

533,765

630,774

630,780

967,393

967,402

1,250,555

1,248,990

1,447,421

1,447,209

1,282,543

.1,282,307 _

644,385

644,010

613,530

622,001

1,409,558

1,409,983

1,686,244

1,686,279

242,781

242,642

170,099

169,713

282,564

274,560

311,775

310,980

234,103

234,086

Total Stress (psi)

10,065

10,059

8,460

8,453

9,030

9,028

7,595

7,595

9,523

9,513

10,966

10,956

9,814

9,8.11

5,462

5,457

5,209

5,264

10,631

10,635

12,708

12,709

2,610

2,608

2,214

2,202

2,958

2,890

3,162

3,146

2,597

2,595





Segment Weld Location Axial Force

Node (lbs)

2-SI6-2RH32-2RH322-324Z 94,861

2-SI6-2RH32-2RH322-324Z-2 94,825

2-SI6-2RH32-2RH322-322F 94,831

2-SI6-2RH32-2RH322-322F-2 94,780 RHRr2-I

2-SI6-2RH32-2RH322-322N 93,973

2-SI6-2RH32-2RH322-322N-2 93,732

2-SI6-2RH32-2RH322-320 93,732

2-SI6-2RH32-2RH322-320-2 93,560

2-SI6-2SI5 82-2SI5 84-196Z 92,718

2-SI6-2SI5 82-2SI5 84-196Z-2 92,733

2-SI6-2SI5 82-2SI584-240N 92,732

2-SI6-2SI582-2SI584-240N-2 92,719 RHRr3-I

2-SI6-2SI582-2SI584-240F 98,521

2-SI6-2SI5 82-2SI584-240F-2 98,311

2-SI6-2SI5 82-2SI5 84-242 . 98,307

2-SI6-2SI582-2SI584-242-2 98,159



Moment (in-lbs)

351,868

351,813

283,515

283,426

222,880

223,440

112,739

112,711

402,630

402,620

387,658

387,483

276,014

268,889

J 14,901

114,857

3-12

Total Stress (psi)

15,887

15,884

13,816

13,810

11,932

11,936

8,584

8,574

17,306

17,307

16,853

16,847

13,792

13,565

. 8,902

8,892


••• This record was final approved on 1/18/2018 9:39:42 AM. ( This statement was added by the PRIME system upon its validation)


RHR Suction:

RHRs-1 RHRs·II •iii•• ., .,,,.,.. -·=-«rw•• ,._

IM0-128 ICM·l29

Hot leg loop 2

RHRReturn:

. -~- -Kl- . - - -T - -Kl- - -i><l I Sl-166-2

Cold Leg Loop 2 I RHRr2·1

I I I L-K)

RH-133

S1·166-3 ~-~-T Cold leg loop 3 :

RHRr3•1

I I

L-KJ RH-134

Figure 3-1 D.C. Cook Units 1 and 2 Typical Piping Layout for RHR Lines


3-13




4.0 MATERIAL CHARACTERIZATION

4.1 RHR LINE PIPE MATERIAL AND WELD PROCESS

The material type of the RHR lines for D.C. Cook Units 1 and 2 is either A376 TP316 for seamless pipes or A403 WP 316 for fittings. This is a wrought product of the type used for the piping in several PWR plants. The welding processes used are Shielded Metal Arc Weld (SMAW) and Submerged Arc Weld (SAW).

In the following sections the tensile properties of the materials are presented for· use in the Leak-Before-Break analyses.

4.2 TENSILE PROPERTIES

Certified Materials Test Reports (CMTRs) with mechanical properties were not readily available for the D.C. Cook Units 1 and 2 RHR lines. Therefore, ASME Code mechanical properties were used to establish the tensile properties for the Leak-Before-Break analyses.

For the A376 TP316 (seamless pipe) and A403 WP316 (wrought fittings) material types, the representative properties at operating temperatures are established from the tensile properties given by Section II of the 2007 ASME Boiler and Pressure Vessel Code. Code tensile properties at temperatures for the operating conditions considered in this LBB analysis were obtained by linear interpolation of tensile properties provided in the Code ..

Material modulus of elasticity was also interpolated from ASME Code values for the operating temperatures considered, and Poisson's ratio was taken as 0.3. The yield strengths, ultimate strengths, and elastic moduli for the pipe material at applicable operating temperatures are tabulated in Table 4-1.

4.3 REFERENCE

4-1 ASME Boiler and Pressure Vessel Code Section II, 2007 Edition through 2008 Addenda.

Material Characterization WCAP-18302-NP



___ _J


Table 4-1 Material Properties for Operating Temperature Conditions on D.C. Cook Units 1 and 2 RHR Lines

Segment

RHRs-I

RHRs-II RHRr2-I RHRr3-I

Material Characterization WCAP-18302-NP

Operating Temperature

(OF)

617

120

Ultimate Strength

(psi)

71,800

75,000

Yield Strength

(psi)

18,764

28,960

Elastic Modulus (psi)

25,215,000

27,992,308




5.0 CRITICAL LOCATIONS

5.1 CRITICAL LOCATIONS

The Leak-Before-Break (LBB) evaluation margins are to be demonstrated for the critical locations (governing locations). Such locations are established based on the loads (Section 3.3) and the material properties established in Section 4.2. These locations are defined below for the D.C. Cook RHR lines.

Critical Locations for the RHR Lines:

All the welds in the RHR lines are fabricated using the Shielded Metal Arc Weld (SMAW) or Submerged Arc Weld (SAW) processes. The pipe material type is A376 TP316 or A403 WP316. The governing locations were established on the basis of the pipe geometry, welding process, material type, operating temperature, opernting pressure, and the highest faulted stresses at the_ welds.

Table 5-1 shows the highest faulted stress and the corresponding weld location node for each welding process type in each segment of the 14-inch RHR suction lines and the 8-inch RHR return lines, enveloping both D.C. Cook Units 1 and 2. Definition of the piping segments and the corresponding operating pressure and temperature parameters are from Tables 3-1 and Figure 3-1. Figures 5-1 through 5-4 show the locations of the critical welds.

Table 5-1 Critical Analysis Location for Leak-Before-Break ofD.C. Cook Units 1 and 2 RHR Lines

Welding Operating Operating

Segment Pipe Size Pressure Temperature Process

(psig) (OF)

RHRs-I 14-inch SMAW 2235 617

SAW 2235 617

RHRs-II 14-inch SMAW 450 120

SAW 450 120

SMAW 2235 120 RHRr-1* 8-inch

SAW 2235 120

Note: *RHRr-I includes RHRr2-I (Loop 2) and RHRr3-I (Loop 3).

Critical Locations WCAP-18302-NP

Maximum Faulted Stress

(psi)

11,527

8,800

12,709

11,581

15,887

21,130

Weld Location Node

288 (Unit 1)

284F (Unit 1)

260N (Unit 2)

268F (Unit 1)

324Z (Unit 2)

196Z (Unit 1)



Critical Location: Segment RHRs-1 SAW weld


14" SCH 160

248

Critical Location: Segment RHRs-1 SMAW weld

Critical Location: Segment RHRs-II SAW weld

5-2

Figure 5-1 D.C. Cook Unit 1 RHR Suction Line Loop 2 Critical Weld Locations




. _____ · -~· J


RHR Return

I I

Accumulator Line Loop 2 • I A I I/,\ Sl-166-2

• • -~# I . ' •l It

to Accumulator Line Loop 2 RHR Return

I I

Accumulator Line Loop 3 I ,

I A t t \ SI-166-3 ,!~' . .,.. ..

~# I . •l It

to Accumulator Line Loop 3

5-3

Critical Location: Segment RHRr-1 SAW weld

Figure 5-2 D.C. Cook Unit 1 RHR Return Line Loops 2 and 3 Critical Weld Locations





Critical Location: Segment RHRs-II SMAWweld

14" SCH ISO

270

5-4

Figure 5-3 D.C. Cook Unit 2 RHR Suction Line Loop 2 Critical Weld Locations





I I

Accumulator Line Loop 2

' I 2-RH-133 .A _ _ _

... _. f I \ 2-SJ-166-2

RHRReturn

!~' 1~· ~., I

•l II

Critical Location: Segment RHRr-1 SMAW weld

Accumulator Line Loop 3 . '

I 2-RH-134 A . _- .

-- f I \ 2-Sl-166-3

RHR Return

,!~' .. .~· ~ ... •l It

to Accumulator Line Loop 2 to Accumulator Line Loop 3

Figure 5:-4 D.C. Cook-Unit-2 RHR Return Line Loops 2 and 3 Critical Weld Locations ·

5-5





6.0 LEAK RATE 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 [

]a,c,e

6.3 CALCULATION METHOD

The basic method used in the leak rate calculations is the method developed by [

]a,c,_e

The flow rate through a crack was calculated in the following manner. Figure 6-1 (from Reference 6-2) was used to estimate the critical pressure, Pc, for the RHR line enthalpy condition and an assumed flow. Once Pc was found for a given mass flow, the [ ]a,c,e was

found from Figure 6-2 (taken from Reference 6-2). For all cases considered, [ ]"'c,e therefore, this method will yield the two-phase pressure drop due to momentum effects as

illustrated in Figure 6-3, where P0 is the operating pressure. Now using the assumed flow rate, G, the frictional pressure drop can be calculated using

where the friction factor f is determined using the [ was obtained from fatigue crack data on stainless steel samples. these calculations was [ ]a,c,e

(6-1)

t,c,e The crack relative roughness, E,

The relative roughness value used in

The frictional pressure drop using equation 6-1 is then calculated for the assumed flow rate and added to the [ ]a,c,e to obtain the total pressure drop

from the primary system to the atmosphere.

Leak Rate Predictions WCAP-18302-NP



-- - ·1


That is, for the RHR lines:

Absolute Pressure - 14.7 = [ ]a,c,e (6-2)

for a given assumed flow rate G. If the right-hand side of equation 6-2 does not agree with the pressure difference between the RHR line and the atmosphere, then the procedure is repeated until equation 6-2 is satisfied to within an acceptable tolerance which in tum leads to a flow rate value for a given crack size.

For the single phase cases with lower temperature, leakage rate is calculated by the following equation (Reference 6-4) with the crack opening area obtained by the method from Reference 6-3.

Q =A (2gtlP/kp)05 ft3/sec; (6-3)

where, LlP == pressure difference between stagnation ari.d back pressure (lb/ft2), g = acceleration of gravity (ft/sec2), p = fluid density at atmospheric pressure (lb/ft\ k = friction loss including passage loss, inlet and outlet of the through-wall crack, A= crack opening area (ft2).

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 3-2 (for Unit 1), and Table 3-3 (for Unit 2), were applied in these calculations. The crack opening areas were estimated using the method of Reference 6-3 and the leak rates were calculated using the formulation described above, The material properties of Section 4.2 (see Table 4-1) were used for these calculations.

The flaw sizes to yield a leak rate of 8 gpm were calculated at the governing locations and are given in Table 6-1 for D.C. Cook Units 1 and 2. The flaw sizes so determined are called leakage flaw sizes.

The D.C. Cook Units 1 and 2 RCS pressure boundary leak detection system meets the intent of Regulatory Guide 1.45 and meets a leak detection capability of 0.8 gpm. Thus, to satisfy the margin of 10 on the leak rate, the flaw sizes (leakage flaw sizes) are determined which yield a leak rate of 8 gpm.




J


6.5 REFERENCES

6-1 ]a,c,e

6-2 M. M. El-Wakil, "Nuclear Heat Transport, International Textbook Company," New York, N.Y, 1971.

6-3 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 11-1, NUREG/CR-3464, September 1983.

6-4 Crane, D. P., "Handbook of Hydraulic Resistance Coefficient," Flow of Fluids through Valves, Fittings, and Pipe by the Engineering Division of Crane, 1981, Technical Paper No. 410.





Table 6-1 Flaw Sizes Yielding a Leak Rate of 8 gpm for the D.C. Cook Units 1 and 2 RHR Lines

Segment Pipe Size Welding Weld Location Leakage Flaw Size Process Node (in)

SMAW 288 (Unit 1) 4.59 RHRs-I 14-inch

SAW 284F (Unit 1) 5.50

RHRs-II 14-inch SMAW 260N (Unit 2) 6.41

SAW 268F (Unit 1) 5.91

RHRr-I* SMAW 324Z (Unit 2) 4.25

8-inch SAW 196Z (Unit 1) 4.11

Note: *RHRr-1 includes RHRr2-I (Loop 2) and RHRr3-I (Loop 3).


6-4




a,c,e

STAGNATION ENTHALPY nc,2 Btu/lb,

Figure 6-1 Analytical Predictions of Critical Flow Rates of Steam-Water Mixtures




Figure 6-2 [



LENGTH/DIAMETER RATIO (L/D)

r,c,e Pressure Ratio as a Function of LID

6-6

a,c,e



I


[

Figure 6-3 Idealized Pressure Drop Profile Through a Postulated Crack


6-7

a,c.e




7.0 FRACTURE MECHANICS EVALUATION

7.1 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 limit load 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 RHR line 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:

. [

r The analytical model described above accurately accounts for the piping internal pressure as well as imposed axial force as they affect the limit moment. Good agreement was found between the analytical predictions and the experimental results (Reference 7-1). For application of the limit load methodology, the material, including consideration of the configuration, must have a sufficient ductility and ductile tearing resistance to sustain the limit load.

Fracture Mechanics Evaluation WCAP-18302-NP



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7.2 RESULTS OF CRACK STABILITY EVALUATION

A stability analysis based on limit load was performed. Shop welds and field welds for the RHR lines of D.C. Cook Units 1 and 2 utilize the SMAW or SAW weld processes. The "Z" correction factor (References 7-2 and 7-3) are as follows:

Z = 1.15 [1.0 + 0.013 (OD-4)] for SMAW

Z = 1.30 [1.0 + 0.010 (OD-4)] for SAW

where OD is the outer diameter of the pipe in inches.

The Z-factors for the SMAW and SAW were calculated for the critical locations, using the pipe outer diameter (OD) of 14.000 inches for the RHR suction lines and 8.625 inches for the RHR return lines. The applied faulted loads of Table 3-4 (for Unit 1) and Table 3-5 (for Unit 2) were increased by the Z factor and critical flaw size was calculated by flaw stability under the respective loading conditions for each governing location. Table 7-1 summarizes the results of the stability analyses based on limit load for the governing locations on D.C. Cook Units 1 and 2. The associated leakage flaw sizes (from Table 6-1) are also presented in the same table.

7.3 REFERENCES

7-1 Kanninen, M. F., et. al., "Mechanical Fracture Predictions for Sensitized Stainless Steel Piping with Circumferential Cracks," EPRl NP-192, September 1976 ..

7-2 Standard Review Plan; Public Comment Solicited; 3.6.3 Leak-Before-Break Evaluation Procedures; Federal Register/Vol. 52, No. 167/Friday, August 28, 1987/Notices, pp. 32626-32633.






Table 7-1 Flaw Stability Results for the D.C. Cook Units 1 and 2 RHR Lines Based on Limit Load

Segment Pipe Size Welding Weld Location Critical Flaw Size Process Node (in)

RHRs-I 14-inch SMAW 288 (Unit 1) 17.22

SAW 284F (Unit 1) 18.03

RHRs-II 14-inch SMAW 260N (Unit 2) 18.87

SAW 268F (Unit 1) 18.85

RHRr-I* 8-inch SMAW 324Z (Unit 2) 10.30

SAW 196Z (Unit 1) 8.34



7-3

Leakage Flaw Size (in)

4.59

5.50

6.41

5.91

4.25

4.11




Figure 7-1 [


Neutral Axis

i3,c,c Stress Distribution

7-4




8.0 ASSESSMENT OF FATIGUE CRACK GROWTH

The fatigue crack growth (FCG) analysis is not a requirement for the LBB analysis (see References 8-1 and 8-2) since the LBB analysis is based on the postulation of a through-wall flaw, whereas the FCG analysis is performed based on the surface flaw. In addition Reference 8-3 has indicated that, "the Commission deleted the fatigue crack growth analysis in the proposed rule. This requirement was found to be unnecessary because it was bounded by the crack stability analysis."

Also, since the growth of a flaw which leaks 8 gpm would be expected to be minimal between the time that leakage reaches 8 gpm and the time that the plant would be shutdown; therefore, only a limited number of cycles would be expected to occur.

8.1 REFERENCES

8-1 Standard Review Plan; Public Comment Solicited; 3.6.3 Leak-Before-Break Evaluation Procedures; Federal Register/Vol. 52, No. 167/Friday, August 28, 1987/Notices, pp. 32626-32633.


8-3 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/Tue~day, . Oc~ober 'P, 1987/Rules. and Regulations, pp. 41288-41295.

Assessment of Fatigue Crack Growth WCAP-18302-NP




9.0 ASSESSMENT OF MARGINS

The results of the leak rates of Section 6.4 and the corresponding stability evaluations of Section 7.2 are used in performing the assessment of margins. Margins are shown in Table 9-1 for the governing locations on D.C. Cook Units 1 and 2. All the LBB recommended margins are satisfied.

In summary, margins at the critical locations are relative to:

1. 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 8 gpm (the leakage flaw).

2. Leak Rate - A margin of 10 exists between the calculated leak rate from the leakage flaw and the plant leak detection capability of 0.8 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 flaw size is stable). A margin of 1 on loads using the absolute summation of faulted load combinations is satisfied.

Assessment of Margins WCAP-18302-NP




Table 9-1 Leakage Flaw Sizes, Critical Flaw Sizes, and Margin for the D.C. Cook Units 1 and 2 RHR Lines

Welding Weld Location Segment Pipe Size

Process Node

RHRs-1 14-inch SMAW 288 (Unit 1)

SAW 284F (Unit 1)

SMAW 260N (Unit 2) RHRs-11 14-inch

SAW 268F (Unit 1)

RHRr-1* SMAW 324Z (Unit 2)

8-inch SAW 196Z (Unit 1)


Assessment of Margins WCAP-18302-NP

Critical Flaw Size

(in)

17.22

18.03

18.87

18.85

10.30

8.34

Leakage Flaw Size

(in)

4.59

5.50

6.41

5.91

4.25

4.11

9-2

Margin

3.8

3.3

2.9

3.2

2.4

2.0



WESTINGHOUSE NON-PROPRIBTARY CLASS 3 10-1

10.0 CONCLUSIONS

This report justifies the elimination of RHR line breaks from the structural design basis for D.C. Cook Units 1 and 2 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.

Note: Alloy 82/182 welds do not exist at the D.C. Cook Units 1 and 2 RHR lines.

b. Water hammer should not occur in the RHR line piping because of system design, testing, and operational considerations.

c. The effects of low and high cycle fatigue on the integrity of the RHR line piping are negligible.

d. Ample margin exists between the leak rate of small stable flaws and the capability of the D.C. Cook Units 1 and 2 reactor coolant system pressure boundary leakage detection systems.

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 (fully aged) stability of the critical flaws.

For the critical locations, postulated flaws will be stable because of the ample margins described ind, e, and fabove.

Based on loading, pipe geometry, welding process, and material properties considerations, enveloping critical (governing) locations were determined at which Leak-Before-Break crack stability evaluations were made. Through-wall flaw sizes were postulated which would cause a leak at a rate often (10) times the leakage detection system capability of the plant. Large margins for such flaw sizes were demonstrated against flaw instability. Finally, fatigue crack growth assessment was shown not to be an issue for the RHR line piping. Therefore, the Leak-Before-Break conditions and margins are satisfied for D.C. Cook Units 1 and 2 RHR line piping. It is demonstrated that the dynamic effects of the pipe rupture resulting from postulated breaks in the RHR line piping need not be considered in the structural design basis of D.C. Cook Units 1 and 2.

Conclusions WCAP-18302-NP



Appendix A: Limit Moment WCAP-18302-NP


APPENDIX A: LIMIT MOMENT

] a,c,e

A-1




Q) ci cu· ... _----------------------

Figure A-1 Pipe with a Through-Wall Crack in Bending

Appendix A: Limit Moment WCAP-18302-NP

A-2



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WCAP-18302-NP Revision 0 Proprietary Class 3

**This page was added to the quality record by the PRIME system upon its validation and shall not be considered in the page numbering of this document.••

Author Approval Johnson Eric D Jan-17-2018 14:47:27

Reviewer Approval Wiratmo Mamo Jan-17-2018 15:29:57

Manager Approval Leber Benjamin A Jan-18-2018 09:39:42

Files approved on Jan-18-2018


WCAP-18302-NP, Revision 0, 'Technical Justification for ... · 1-2 NUREG-0800 Revision 1, March...

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