ML20100N186

Forwards Request for Exemption from Current NRC Piping Design Criteria Re Arbitrary Intermediate Pipe Breaks. Alternative Criteria to Provide Flexibility to Remove or Retain Shim Restraints Requested

ML20100N186
Person / Time
Site:	Clinton
Issue date:	04/16/1985
From:	Spangenberg F ILLINOIS POWER CO.
To:	Schwencer A Office of Nuclear Reactor Regulation
References
U-0832, U-832, NUDOCS 8504180416
Download: ML20100N186 (19)

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E t '; U-0832 r #, L30-65 (04-16)-L 1A.120 ILLIN018 POWER COMPANY IP . CLINToN PonEP STATION. P.o. BOX 678. CLINToN. ILLINOIS 61727 tApril 16, 1985 Docket No. 50-461 h .Direc'ort of Nuclear Reactor Regulation Attention: Mr..A. Schwencer, Chief

-Licensing Branch No. 2

' Division of Licensing-US Nuclear Regulatory Commission

Washington, DC 20555.'

$ i

Subject:

.Clinton Power Station Unit I l

' Elimination of Arbitrary Intermediate Pipe Breaks t

Dear .Mr. Schwencer:

The purpose of this letter is to request exemption from current Nuclear Regulatory Commission ~(NRC) piping design criteria with respect

.to' arbitrary intermediate pipe breaks. These'are breaks which, based on

. stress. analysis,-are below the stress limits and/or the cumulative usage factors specified in_the curren'd NRC criteria, but are. selected to provide'a minimum of two breaks between terminal ends.- Elimination of arbitrary-intermediate pipe breaks at Clinton Power Station (CPS) results in design and construction benefits due to the potential elimination of the' associated pipe whip restraints. Also, operational benefits arise from the decreased number of pipe whip restraints to be inspected and maintained for 40 years.

Attached is a detailed explanation and justification for the elimination of arbitrary intermediate _ pipe breaks at CPS. The following information is presented in it:

-1)- Current Break Selection Criteria

2) Industry Experience

3) Benefits.

4)- Al' ternate Pipe Break' Criteria

5) . Listing lof the Eliminated Pipe, Breaks s

6)' l Additional Technical: justification

.Since the design'and-construction of-pipe whip restraints Jassociated with arbitrary intermediate pipe breaks is nearly. complete,

Illinois Power Company,(IPC):does not. anticipate removing any of the installed restraints at this time. IPC is requesting the approval of' alternative. pipe. break criteria to provide.the flexibility to remove or not to-shim-: restraints in the future, if deemed necessary.

J 8504100416 850416 > d T:

{DR ADOCK 05000461 PDR ii - , 800l u

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. C . . . .* .,. U-0832' L30-85(04-16)-L 1A.120 IPC requests NRC approval for the application of alternative pipe

. break criteria as stated in section Sil and 5.2 of the attachment which would; eliminate the need to postulate' arbitrary intermediate pipe.

. breaks. Application'of the alternative pipe break criteria vill not falter IPC's ccamitment to quality in the design of safety related

' structures, systems, and components. The quality assurance program will i continue.to-ensure that safety related attuctures, systems and LcomponentsJare designed, fabricated, erected and tested to the quality.

standards appropriate with the safety. function to be performed.

i Dae~to'the mid-May' scheduling of hot op'erational testing at CPS,

-immediate attention by the NRC-'is requested so\that IPC can realize maximum benefits afforded by this proposed change to the pipe break criteria. A favorable response is requested by May 9,.1985.

Sincerely yours,

/

y, no e N F. A. Sf angefterg Director - Nuclear L.Lcensing and configuration 4 Nuclear. Station Engineering 4

Attachment

{ JDT/ lab I' cc: B. L. Siegel,' ERC Clinton Licensing Project Manager NRC Resident Office

' Illinois Departmentaof Nuclear Safety

~ Regional Administrator, Region III, USNRC s

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.CLINTON POWER STATION UNIT 1 ARBITRARY INTERMEDIATE PIPE BREAKS 1.0 Introduction

.The Fuclear[ Regulatory Commission (NRC) staff and industry discussions with the Advisory Committee on Reactor Safeguards

'(ACRS) have indicated general agreement with the elimination of the arbitrary _ intermediate breaks. Additionally, the NUREG-1061, LVolumo'3,' published in November 1984 recommends that the current NRC criteria be revised to eliminate the requirements for

. mechanical pipe rupture-protection against arbitrary intermediate breaks.: Elimination of arbitrary intermediate. breaks results in l_ design benef'.ts due to the potential elimination of.the associated

. pipe whip;rs.straints and related provisions currently incorporated

,i Ein the plart design to mitigate 'the effects of 'such pipe breaks.

In addition,. operational-advantages also ensue from the decreased' g . numbers of' pipe whip restraints to be inspected.and maintained for i

f40 years.;

-2.0. Break Selection Criteria

[ The break'aelection criteria-currently employed by Illinois Power

! - Company (I?C) for the- Clinton Power Station Unit 1 (CPS) is based f upon NRC Branch Technical Position MEB 3-1 as presented in the

" Standards Review Plan, Section 3.6.2. This position, requires-that n'

pipe breaks.be postulated at anchored' terminal ends and at.

intermediate locations where, depending on the pipe class, stresses or. cumulative usage factors-exceed specified limits. If two intermediate locations cannot be determined based'on the above

.because the stresses and cumulative usage factors are below the ,

-specified limits, the two highest' stress locations are selected.

3.0 Industry-Experience

l. . IPC c'oncurs with other nuclear utilities in the belief that current

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' knowledge and experience' supports the conclusion that designing for arbitrary intermediate breaks uis not justified.and that this ,

y _ requirement should be deleted. iThie conclusion:is supported by. ,

! , extensive operating-experiencecin over 80 operating U.S. plants and-j ca' number of similar plants overseas in which no_ piping failures

. have been known - to occur: that 'would suggest :the need ' to design l Lprotective features to mitigate the dynamic effects of arbitrary j~ -intermediate breaks. Arbitrary' intermediate breaks are~often.

t-  :. postulated'atLlocations where maximum pipe _ stresses are well'below

.the ASME Codetallowables.and'within a few-percent of theistress-levels at' other points 1La th'e same piping s' y stem. Mitigating the

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1 effects =fram such breaks with pipe _ whip restraints results'in fcomplicated protective ~ features being provided atfarbitrary b'reak'

-locations but.does lictie to enhance overall plant safety..

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4.0 Benefits-Elimination of the arbitrary intermediate break locations results in the potential elimination of the associated pipe whip restraints e.nd other structural provisions to mitigate the consequences of these bre'aks. Significant operational benefits are also realized F over the 40-year life of each plant. As identified in NUREG/'

4 CR-2136,:these benefits accrue in the areas of plant reliability and reduce. exposure of plant personnel to radiation during in-service inspection which is complicated by the presence of pipe

-whip restraints.

4.1 Access Access during plant operation for maintenance and inservice inspection is: improved due.to decreased congestion from these '

restraints.and their supporting structural steel. Also, fewer r restraints must be removed to gain access for weld inspec-

' tions. In addition to the decrease in maintenance effort, a corresponding reduction in man-rem exposure can be realized from fewer manhours spent in radiation areas, per ALARA.

4.2 Decrease in Heat Loss i By design, whip restraints fit closely around the high energy

. piping with gaps typicully being on'the order of an inch. t These restraints and their. supporting steel increase the heat loss to the surrounding environment significantly. Also, because thermal movement of the piping system during start-up and shutdown could deform the piping insulation against the fixed whip restraint, che insulation must be cut back in these areas, creating convection gaps. adjacent to the restraint, which, also increased heat loss to the environment'. This is a contributor to the tendency of many containments to operate at

-temperatures near technical specification limits. The ,

. elimination of whip reatraints associated with arbitrary :

intermediate breaks would' reduce heat loss to the containment and reduce containment temperature during power = operation.

4.3 Unanticipated Thermal Expansion Stress Pipe rupture protection devices are designed not to restrict pipe-free-thermal ~ expansion _however should these_ devices come into contact with the pipe.itself, unanticipated stresses due to restraint'of thermal expansion can be introduced into the piping system. As brought:out in ACRS hearings,sthe. potential

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for'this happening is greaterfthan:the potential for mechanistic failure at an arbitrary break point.- This results

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-in'a decrease in the;overall reliability.of the pipe system.

'To prevent this, an additional as-built verification step'is .s involved inLthe design process for each installed pipe whip restraint that requires complex measurements both in the cold and hot position of the pipe. _ The elimination of arbitrary Dintermediate breaks would significantly reduce the effort 2

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-_ involved in protecting the piping from the effects of unanticipated thermal expansion stresses at the associated whip restraints.

h 5.0 ' Alternative Pipe Break Criteria IPC proposes the following alternative pipe break criteria.

5.1- ASMZ Section III Piping Inside Containment ,

Piping systems shall be designed to accommodate pipe breaks at anchored terminal ends and locations where the

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stress or usage factor criteria of MEB 3-1 are exceeded.

. -No arbitrary-intermediate pipe breaks wil1~be postulated where the stress.and/or usage factor criteria are not exceeded.

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• For: breaks that must-be taken, the design will accommodate pipe whip, . jet impingement, -and compartment pressurization resulting from mechanistic treatment of the break. Current acceptable methods for limiting break opening, moderate and low energy exclusions, limited

. duration operation, etc. may still be applied..

l For plant flooding evaluations,' environmental qualification of equipment, and structural design of

equipment in' areas traversed by high energy piping i systems,~ pipe breaks will continue to be postulated ~1n accordance with the 'present project criteria,- i.e. , in

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each area traversed by the high energy piping system,

, non-mechanistic breaks _are postulated at the location

[~ that results in the-most severe environmental con' sequences. .Therefore. elimination of.the' arbitrary intermediate pipa breaks does not impact environmental

.qualifiqation of equipment nor' plant structural design.

5.2 ASME Section III and Seismically Designed Non-Section III~

' Piping Outside Containment Piping systems shall'be designed to accommodate pipe breaks at anchored terminal ends and locations where the

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stress criteria of MEB-3-1 is r.xceeded. No arbitrary intermediate pipe' breaks will be- postulated when the ~

stress criterion is not exceaded.

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For breaks thatimust be taken, the_ design will-accommodate pipe whip and jet impingement effects

resulting from mechanistic treatment of.the break.

-Compartment pressurization and flooding effects from breaks postulated.in accordante with MEB 3-1 will be

,' . accommodated in~the design.. Current acceptable methods I for limiting break' opening,Lmoderate and low energy exclusions,-limited duration operation, etc.'may still be

. _ applied.

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For plant flooding evaluations, environmental ,

qualification of equipment, and structural design of

- equipment.in. areas traversed by high energy piping i' systems, pipe-breaks-will continue to be postulated in

. accordance with the present project criteria, i.e., in E . each area-traversed by the high energy piping system,-

non-mechanistic breaks are postulated-at the location

, that results-in the most severe environmental

consequences. Therefore, elimination of the arbitrary intermediate pipe breaks does not impact the

' environmental qualification of equipment nor plant structural: design.

-6.0. Eliminated Pipe Breaks

' Appendix A. lists by subsystem Class 1 large bore intermediate pipe-

• 1breaks which may be eliminated from the design because the stress and usage factor limits have not been exceeded. ;After approval of this submittal by th9 NRC, the FS_AR will be revised to show which pipe whip restraines are not-required. A4 total of approximately 33

. breaks-sre to be eliminated.

. Appendix B lists the ASME Class 1, 2, and 3 small bore piping

' intermediate break locations that are to be eliminated. A total of approximately 12 breaks are~to be. eliminated.

j' The application of the proposed alternative pipe break criteria will result.in the deletion of approximately 45 break' locations and the potential deletion of 37 pipe whip. restraints. However, it should be noted that piping and system design is an iterative i process and that postulated break locations could potentially move

.as the system design and analysis of structures and piping develops over the course

of the design and construction. process.f Owing to j tha iterative nature of!the design process and its:potentialifor affecting postulated break-locations, changes affecting high' energy L , systems are continuously monitored and' evaluated to determine'the impact on. break location. ,IPC proposes to apply'these alternative criteria'to any potential break locations in the systems identified ~

.herein,'provided the stresses at those' locations areLbelow'the break selection threshold, and the operational concerns'in

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l Attachments D through'F are adequately' addressed. .This flexibility-is necessary to minimize future requests for break' elimination as '

the location' of the intermediate break points change during the ,

evolution'of the plant' design.

q 6.1 Elimination of Breaks Not Yet Identified' 1 4

iThe existing guidelines in MEB 3-1 of'the SRP (NUREG-0800) I

Revision 1 will be metifor1 hose t piping systems, or' portions l thereof, which'are not included

in this submittel. -If.other  ;

piping subsystems included in the systems: identified in Table- '

-D-1, but not specifically1 identified in this submittal, subse-quently qualify for the conditions described herein, the ,

I implementation of the proposed elimination of the arbitrary l L

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'i n'tet-ediate break criteria may be used. If this criteria is to be applied to additional. systems not included in Table D-1, those systems will be appropriately identified to the staff. ,

7.0 Additional Technical Justification

The following appendices provide additional technical information to justify this request. Specific NRC concerns are addressed in 10 Appendices C through G as follows:-

1. Technical justification for elimination Appendix C of arbitrary intermediate pipe breaks

_ 2. Provisions for minimizing intergranular Appendix D stress corrosion cracking in high energy lines

13. Provisions for minimizing the. effects Appendix E of thermal and vibration induced .

. piping fatigue

4. Provisions for minimizing water / steam Appendix-F hammer effects 5.- - Provisions for minimizing local stresses Appendix G from welded attachments 8.0 Conclusion IPC has reviewed the basis for the postulation of intermediato pipe breaks on designated high energy lines and has compared the design stresses and usage factors with the SRP MEB 3-1 Guidelines. On the

' basis'of ASME Code calculations, there is no technical' justification for the postulation of arbitrary intermediate pipe breaks. The probability of pipe rupture at the values of stress and usage factors assignable to these intermediate pipe' breaks is extremely remote, subsequently this' relief should..be' granted.

Since the design.and. construction of pipe whip restraints associated with arbitrary intermediate pipe breaks is nearly

complete,; Illinois Power-Company _(IPC)'does not anticipate removing any of the installed restraints at this time. 'IPC is requesting

.the approval-of alternative. pipe break criteria to provide the ~

. flexibility: to remove or not to' shim restraints in the future, if

' deemed necessary.

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APPENDIX A

• j- Summary of Class l'Large Bore Piping Intermediate. Break and Pipe Whip Restraint Reductions ,

Potential

' Pipe Whip Breaks /- Restraints /.

4 Intermediate Break ID Restraint'ID System Subsystem Break Locations Eliminated Eliminated

-Reactor RR Loop A - Discharge piping branch' 8/RD6 8/R356B R357B' c Recirculation RR Loop B connection points to RD7 the ring-header. RD8 R358B RD9 R359B (Loop A (Loop A numbers similar to identical) Loop B)

Main' Steam MS-Line A - Elbow butt welds on 3/MS-C57 4/MS-R24 50' elbows prior to MS-C58 'MS-R25 containment MS-C68 MS-R26 Elbow butt weld at top MS-R27 of riser from RPV.

MS-Line B .- Isolation valve guide 2/MS-Cl 4/MS-R2 locations. MS-C19 MS-R4

- ' Elbow butt weld at top MS-R5 of riser from RPV. MS-R6 i

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.MS-Line C - Isolation valve guide 2/MS-C35 4/MS-R16 locations. MS-C55 MS-R18 Elbow butt welds at top MS-R19 of riser from RPV . MS-R20

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9' APPENDIX A -

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Summary of Class 1 Large Bore Piping Intermediate Break and Pipe.-Whip Restraint Reductions- *

(continued)

' Potential ~-

Pipe Whip- ,

Breaks / Restraints /. '

Intermediate Break ID: Restraint ID~

' System Subsystem Break' Locations . Eliminated- ' Eliminated Main Steam MS-Line D Isolation valve' guide 2/MS-C21 4/MS-R10

- . locations. MS-C33 MS-R11

, - Elbow butt veld at top MS-R12 of riser from RPV. MS-R13

.High Pressure HP-01 -

Butt veld at check valve 2/HP-C6' 3/HP-R3 -

Core Spray prior to drywell wall. HP-C8- HP-R4 elbow butt weld at bottom of riser from RPV. HP-R4A

. - Elbow tutt weld at top of' riser from RPV.

Low Pressure LP-01 -. Butt welds at check valve 2/LP-CIA 4/LP-R1 core Spray and gate valve prior to LP-C8 LP-R2A-drywell wall. LP-R3

, Elbow butt welds at LP-R4A -i l

bottom.and-top of riser

, from RPV.

t Residual Heat RH-01 - Butt weld at check valve 3/RH-C1 2/RH-R2 '

l Removal prior to drywell. wall. RH-C8 RH-R3 Butt weld at gate valve RH-C9 '

prior to drywell wall.

- Elbow butt. welds at top  ;

of riser from RPV.

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Summary of Class 1 Large Bore" Piping"

. ~. Intermediate Break andL. Pipe: Whip Restraint-Reductions (continued)-

Potential Pipe Whip .

1 Breaks / . Restraints /-

Intermediate ' Break ID. Restraint ID System-  : Subsystem ~ Break Locations Eliminated Eliminated eResidual Heat ~ RH-O'3 -

Butt weld at check' valve 3/RH-C20 2/RH-R9- it Removal prior to drywell~ wall. RH-C21. 'RH-RIO

--Elbow butt welds at RH-C25 bottom-of riser from RPV.

. Elbow-butt weld-at' top. I of riser from RPV.

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, RH-05 - Lutt' weld at check valve 2/RH-C15 -

prior to drywell wall. .RH-C17

- Butt weld at gate valve .r prior.to drywell wall.

- Elbow butt weld at top of risersfrom RPV.

'RH-34 - Butt. welds at first-~and 1/RH-C32 -

second gate valves from '

the 20" Recire. header.

Reactor' Core RI-01: - ElbowLbutt welds at 3/RH-C5 2/RI-R4

-Isolation bottom ofl: riser f rom 24" RI-C6. RI-R5 Cooling- MSz header. RI-C5A  :

- Butt veld at 45* elbow prior to drywell wall. ,

TOTALS 33 37  ;

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APPENDIX B- '

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Summary of Class 1, 2, and13-Small Bore. Piping-Intermediate Break-Reductions ,

Potential No..of -Pipe. Whip

' Intermediate Breaks Restraints System Subsystem Break Locations ID EliminatedJ Eliminat'ed.

' Standby. Liquid SC-07 SC-C4- -3 0

' Control. .SC-C5 SC-C6 Reactor. Water RT-02 :RT-C341A '2 0 Cleanup RT-C261 RT-05 RT-C173A 2 0 RT-C187A Nuclear NB-01 NB-CSA 2 0 Boiler NB-CIO Piping Main Steam MS-05 MS-C74 1 0 Drain

Isolation IS-03 IS-C5 2 0 Valve Seal IS-C8 TOTALS 12 0 t

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. . ~l7 :  :._ l APPENDIX C TECHNICAL JUSTIFICATION FOR ELIMINATION OF ARBITRARY INTERMEDIATP. BREAKS ,

The following items provide generic. technical justification for the

elimination of: arbitrary intermediate pipe breaks and their associated

- ' pipe whip restraints.

1. _ Operating-procedures and pipe and system designs minimize the

possiblity of intergranular stress corrosioa cracking, thermal and vibration induced

fatique, and water / steam hammer in these. lines in which arbitrary pipe. breaks are currently poaculated. Detailed design provisions for these phenomena are provided in Appendices D, E, and _ F,: respectively.-

2. The' remaining postulated pipe breaks and whip restraints _ provide an adequate level'of protection in areas containing high energy lines.

Potential environmental effects are still considered in the design.

3. Pipe breaks ~are postulated to occur at locations whers, depending on.the pipe class, stresses are only 80% of Code allowable or where

'the cumulative usage factor is only 10% of the allowable 1.0. 1he

-arbitrary breaks'to be eliminated all exhibit stresses and usage factors below these conservative thresholds. r

4. Pipe rupture is recognized in Branch Technical-Posicion NEB 3-1 as l being a:" rare event which may only occur under unanticipated conditions".

5. Arbitrary intermediate breaks are only postulated'to. provide t

' additional conservatism in the design. - There is no technical

-justification for. postulating these _ breaks.

6.- Elimination of pipe whip restraints associated-with the arbitrary

~ breaks will facilitate'in-service inspection, reduce heat losses i

from the restrained piping, and reduce the potential-for-restraining pipe due to unanticipated' thermal' growth and' seismic motion.

7. . Pipe break-related' equipment qualification-(EQ) requirementsTare not.affected by-the. elimination of the' arbitrary. breaks. Breaks

-are' postulated non-sechanistically for EQ purposes.-

It is' concluded that the elimination of arbitrary intermediate breaks is I t'echnically ~ justified. basedion the proceding reasons.

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APPENDIX D PROVISIONS FOR MINIMIZING STRESS CORROSION CRACKING IN HIGH ENERGY LINES Industry' experience has shown~(NUREG-0691).that the potential for inter-

. granular' stress corrosion cracking (IGSCC) is less likely if the  !

• following conditions are controlled: high residual tensile stresses, i

susceptible piping material', and a corrosive environment.-

4 With_the' exception of the reactor recirculation piping, all austenitic stainless steel in contact with the reactor coolant is 316 L stainless Esteel and, therefore, has less than 0.03% carbon content.- The likelihood of IGSCC in stainless steel increases with carbon content.

The following additional process controls were applied in addition to 4 material l selection; j i:

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• All'austenitic stainless steel was purchased in the solution

• heat treated condition in accordance with applicable ASME and

-ASTM specifications.

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Welding heat input was restricted and interpass temperature l

wasilimited to 350*F. High heat welding processes such as

' block welding and electroslag welding were not permitted. All ,

. weld filler metal and castings were required by specification ,

i j to hwe a minimum of 5% ferrite. ,

• Inside diameter grinding of pipe welds was prohibited unless

! the pipe weld was subsequently solution-annealed.

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• Bending of small diameter.(2 inch and smaller) piping or tubing were eliminated by using fittings in the solution /

annealed condition. Pipes cold bent to.cause greater than 2h%

[ strain or to a radius less-than 20D'("D" being the' pipe or j: tubing diameter) were solution annealed.

Pickling of welds not subsequently solution-annealed were prohibited.

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D These controls were used to avoid severe sensitization and to comply

'with the intent of Regulatory Guide 1.44, " Control of the Use of

[ Sensitized Stainless Steel."

The reactor recirculation piping is fabricated primarily of 304 j' stainless steel.- Certain portions'have been changed to " nuclear grade" type"316-L which conts. ins less than 0.03% carbon. The remainder has had

!' corrosion-resistant clad" applied in the vicinity of the field ' welds 'so tihat no heat-affected type 304 will be'in contact with the coolant. The

piping assemblies were all solution annealed after all shop ~ welding and application of the cladding.

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' EFurthervare, NUREG-1061, Volume 3 (November 1984) indicates that thermal fatigue and stress corrosion cracking ~cannot be absolutely excluded from piping' operation and that it may never be possible to either precisely D-1 l

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-specify acceptable levels for them or assure' analytically that the specific. levels would not be exceeded. However, NURFG-1061 indicates that should these unanticipated severe conditions occur, the break would 1 most likely be located at the ' terminal ends, at connections to

-components .and at other locations which introduce higher stress concentration or that exceed the stated threshold limits of'SRP 3.6.2.

Based on these factors, the NUREG-1061, Volume 3, concluded that .

relaxing the arbitrary intermediate break requirements would not

-introduce adverse effects.

. Table D-1 summarizes the systems in which currently postulated arbitrary

' intermediate-breaks are to be eliminated.

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" APPENDIX D. M I TABLE D-1. y ,

, ;3 Elimination of Arbitrary: Breaks: ^

-. Systems Summary-

' Numb'e r' o f 1 B reaks /1.

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Pipe. Operating:  ! Whip. Restraints-Temp'. -(,F).

Piping = System -Material Deleted

-Main'~ Steam CS 550- ^11/16: -

. Reactor Recire SS 534 -8/8 550" 2/3 High. Pressure Core CS Spray LowiPressure Core CS 550 2/4 o

Residual Heat.' Removal CS/SS 550 9/4

- Reactor Core. Isolation' CS- 550 3/2 Reactor. Water. Clean-up CS 534-544/,437/ 4/0 t 233/120 .

Main. Steam Isolation ~ CS. 550 2/0 .

. Valve-Leakage rControl .)

CS/SS 549 2/0 NucleariBoiler: Piping Standby.. Liquid: Control CS/SS 135/80 2/0 45/37

- SS'.- Stainless Steel CS - Carbon Steel- <

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APPENDIX E PROVISIONS TO MINIMIZE THE EFFECTS OF-THERMAL AND VIBRATION INDUCED PIPING FATIGUE I.. GENERAL FATIGUE DESIGN CONSIDERATIONS For Class 1 lines, fatigue considerations are addressed by the cumulative usage factor (CUF). To' ensure that piping does not fail due-to fatigue, the ASME Code has established the CUF limit at 1.0.

By definition, all arbitrary intermediate break locations have CUFs below 0.1.

For Class 2 and 3 lines, fatigue.is. considered in the allowable stress range check for thermal expansion stresses. This stress is included in the total stress.value.used to determine postulated break locations. All arbitrary break locations exhibit stresses less than 80% of-the code allowables. If the number of thermal cycles is' expected _to be greater than 7,000, then the' allowable

. stresses are-further reduced by an amount dependent on the number of cycles.

II. THERMAL DESIGN CONSIDERATIONS For Class 1 lines anticipated flow conditions that could result in piping thermal transient stresses are defined. Piping thermal

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transient stresses are included in cumulative usage factors and documented in stress reports for the piping.

III. VIBRATION DESIGN CONSIDERATIONS

Piping at CPS is designed and supported to minimize transient and steady state vibrations. Preoperational and start-up testing will be performed to ensure that vibration of the piping systems are within allowable limits. The purpose of the program is to ensure that operations piping vibration does not result in exceedances of allowable stress amplitudes nor result in undesirable system

. responses. ~The freedom from restraint or snubber lock-up will also be observed; and a-cold / hot walkdown will be included.

Plant personnel will be trainedsto recognize excessive piping vibration so that' potential problems can be. resolved. In addition, a formal' test' program, as outlined-in the FSAR will be completed to

• verify the acceptability of the piping steady-state vibration.

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APPENDlX F

-PROVISION FOR MINIMIZING STEAM / WATER HAMMER EFFECTS 1 1. . Wr.ter' hammer is prevented in the ECCS discharge lines by maintaining the lines in a full condition. The lines are kept

. full up to the injection isolation valves by water leg pumps.

Bayond the discharge valve the line is not drained when the system is on standby, so the discharge lines will remain full.

"The HPCS is a motor-operated system and has no steam supply line. l The steam supply line to the RCIC turbine is maintained at an elevated temperature down to the shutoff valve directly upstream of

.the turbine by means of a condensing pot arrangement. The steam supply line is sloped downward to allow any moisture in the line to )

l drain off to the condensing pot. The condensing pot drains to the main condenser during normal plant operation and is automatically isolated when the RCIC system is initiated.

The. isolation valves on the steam supply line to the RCIC turbine are normally open, and automatically close upon receipt of any one of the following signals; a) A high pressure drop across a flow device in the Steam supply line equivalent to 300 percent of the steady state steam flow at 1192 psia.

b) A high area temperature, utilizing temperature switches in the leak detection system.

c)' A low reactor pressure of 50 psig minimum.

d) A high pressure between the turbine exhaust rupture diaphragas.

These valves may also be remote manually closed. A one-inch bypass with a motor operated-shutoff valve is supplied'around the inboard steam line isolation valve. This bypass.line will be used for

pressurizing,' draining, and pre-warming the. steam line prioroto opening the inboard steam'line' isolation

valve.

J In order to prevent damage from water hammer, neither steam isolation valve is opened automatically by an initiation'aignal.

Should either or both'of these valves be closed, they must be reopened by first closing both valves completely. With both' valves

. closed, the outboard-isolation valve can be: reopened to allow any.

imoisture in the line to drain.- Then moisture ahead of the inboard isolation valve is equalized and the downstream'line is warmed by slowly opening the inboard isolation valve bypass valve. Finally,

.the: inboard isolation valve may be reopened without. water hammer occuring.

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2. The main. steam and feedwater systems'are expected to experience steam and. water hammer loadings, respectively. Analyses are p

'erformed for these loadings and the main steam and feedwater systems are. designed to accommodate and minimize effects of these

>1oadings.- Main-steam piping is analyzed and designed for the

, effects of isolation valves closures, turbine stop valve closures, and safety relief valve openings. The feedwater piping is analyzed and designed for the effects of check valve closure caused by flow reversa1'from the RPV after a feedwater pump trip. The main steam

and feedwater: stress reports include the stresses and usage factors calculated from.the analyses of these events.

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APPENDIX G ,

PROVISION FOR MINIMIZING LOCAL STRESSES FROM WELDED ATTACHMENTS IPC has reviewed >all arbitrary l intermediate break locations to be

. eliminated and has determined that.in most cases no welded attachments are placed in close proximity to postulated break. locations. In four cases.'where welded attachments are in proximity to the postulated arbitrary. breaks, the local bending stresses induced by the attachment will not affect the stresses at the postulated break point. To ensure that this is the case, the~1ocal stresses have been determined and added

.to the primary stress in the stress report.

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