NRC Generic Letter 1987-11

NRC Generic Letter 1987-011: Relaxation in Arbitrary Intermediate Pipe Rupture Requirements

ML031150493
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000000, Zimmer, Fort Saint Vrain, Washington Public Power Supply System, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Clinch River, Crane
Issue date:	06/19/1987
From:	Miraglia F J Office of Nuclear Reactor Regulation
To:
References
GL-87-011, NUDOCS 8706230486
Download: ML031150493 (12)

• - .~ S ve ^UNITED STATESNUCLEAR REGULATORY COMMISSIONWASHINGTON, D. C. 20555June 19, 1987TO ALL OPERATING LICENSEES, CONSTRUCTION PERMIT HOLDERS AND APPLICANTS FORCONSTRUCTION PERMITS

SUBJECT: RELAXATION IN ARBITRARY INTERMEDIATE PIPE RUPTURE REQUIREMENTS(GENERIC LETTER 87- 1]The NRC has finalized a revision to Branch Technical Position MEB 3-1 ofStandard Review 'Plan S~ection 3.6.2 In NUREG-0800 (Enclosure 1). The revisioneliminates all dynamic effects (missile generation, pipe whipping, pipe breakreaction forces, Jet impingement forces, compartment, subcompartment and cavitypressurizations and decompression waves within the ruptured pipe) and allenvironmental effects (pressure, temperature, humidity and flooding) resultingfrom arbitrary intermediate pipe ruptures. This action allows the eliminationof pipe whip restraints and Jet impingement shields placed to mitigate theeffects of arbitrary intermediate pipe ruptures,, and other related changes.Licensees of operating plants desiring to eliminate previously required effectsfrom arbitrary intermediate pipe ruptures may do so without prior NRC approvalunless such changes conflict with the license or technical specifications. Inthe case of a conflict, a license amendment should be requested before anychanges are made. In either case, the licensees' updated FSARs should reflecteliminated hardware associated wit'h arbitrary intermediate pipe ruptures.Arbitrary intermediate pipe ruptures, which previously were specified in B.1.c.-(l)(d) of MEB 3-1 for ASME Code Class 1 piping and in B.1.c.(2)(b)(ii) of MEB3-1 for ASME Code Class 2 and 3 piping, are now no longer mentioned or definedin MEB 3-1. Besides the relaxation in requirements relating to arbitraryintermediate pipe ruptures, the revised Standard Review Plan Section 3.6.2updates the citations to the ASME stress limits to achieve consistency with'current practices, and introduces other minor changes. However, requirementsfor postulated terminal end pipe ruptures, postulated intermediate piperuptures at locations of high stress and high usage factor and for leakagecracks are retained in the revision to MEB 3-1.Frank J a. r.Associate Director for ProjectscL eOffice of Nuclear Reactor Regulation

Enclosure:

Revised MEB 3-1of SRP 3.6.2 I~~pghl o L5b BRANCH TECHNICAL POSITION MEB 3-1POSTULATED RUPTURE LOCATIONS IN FLUID SYSTEMPIPING INSIDE AND OUTSIDE CONTAINMENTA.

BACKGROUND

This position on pipe rupture postulation is intended to comply with therequirements of General Design Criterion 4, of Appendix A to 10 CFR Part 50 forthe design of nuclear power plant structures and components. It is recognizedthat pipe rupture is a rare event which may only occur under unanticipatedconditions, such as those which might be caused by possible design, con-struction, or operation errors; unanticipated loads or unanticipated corrosiveenvironments. Our observation of actual piping failures has indicated thatthey generally occur at high stress and fatigue locations, such as at theterminal ends of a piping system at its connection to the nozzles of a compon-ent. The rules of this position are intended to utilize the available pipingdesign information by postulating pipe ruptures at locations having relativelyhigher potential for failure, such that an adequate and practical level ofprotection may be achieved.B. BRANCH TECHNICAL POSITION1. High-Energy Fluid Systems Pipinga. Fluid Systems Separated From Essential Systems and ComponentsFor the purpose of satisfying the separation provisions of plantarrangement as specified in B.1.a of Branch Technical Position (BTP)ASB 3-1, a review of the piping layout and plant arrangement draw-ings should clearly show the effects of postulated piping breaksat any location are isolated or physically remote from essentialsystems and components. At the designer's option, break locationsas determined from B.1.c. of this position may be assumed for thispurpose.b. Fluid System Piping in Containment Penetration AreasBreaks and cracks need not be postulated in those portions of pipingfrom containment wall to and including the inboard or outboard isola-tion valves provided they meet the requirement of the ASME Code, Sec-tion III, Subarticle NE-1120 and the following additional, design re-quirements:Systems and components required to shut down the reactor and mitigate the con-sequences of a postulated pipe rupture without offsite power.3.6.2-10Rev. 2 -June 1987 (1) The following design stress and fatigue limits should not beexceeded:For ASME Code,Section III, Class I Piping(a) The maximum stress range between any two loads sets(including the zero load set) should not exceed 2.4 Sm.,and should 'be calculated2 by Eq. (10) in NB-3653, ASMECode, Section.III.-. IIf the calculated maximum stress range of Eq. (10) exceeds2.4 Si. the stress ranges calculated by both Eq. (12) andEq. (13) in Paragraph NB-3653 should meet the limit of2.4 S(b) The cumulative usage factor should be less than 0.1.(c) The maximum stress, as calculated by Eq. (9) in NB-3652under the loadings resulting from a postulated pipingfailure beyond these portions of piping should not exceedthe lesser of 2.25 SM and 1.8 S, except-that following afailure outside containment, the pipe between the outboardisolation valve and the first restraint may be permittedhigher stresses provided a plastic hinge is not formed andoperability of the valves with such stresses is assured inaccordance with the requirements specified in' SRP Section3.9.3. Primary loads include those which are deflectionlimited by whip restraints.For ASME Code,Section III, Class 2 Piping:(d) The maximum stress as calculated by the sum of Eqs. (9) and(10) in Paragraph NC-3652, ASME Code,Section III, con-sidering those loads and conditions thereof for whichlevel A and level B stress limits have been specified inthe system's Design Specification (i.e., sustained loads,occasional loads, and thermal expansion) including an OBEevent should not exceed 0.8(1.8 Sh + SA). The 5h and 5A^- are allowable stresses at maximum (hot) temperature andallowable stress range for thermal expansion, respectively,as defined in Article NC-3600 of the ASME Code, Section-2 -III.2For those loads and conditions in which Level A and Level B stress limitshave been specified in the Design Specification (including the operating basisearthquake).3.6.2-11Rev. 2 -June 1987 (e) The maximum stress, as calculated by Eq. (9) in NC-3653under the loadings resulting from a postulated pipingfailure of fluid system piping beyond these portions ofpiping should not exceed the lesser of 2.25 Sh and 1.8 Sy.Primary loads include those which are deflection limitedby whip restraints. The exceptions permitted in (c) abovemay also be applied provided that when the piping betweenthe outboard isolation valve and the restraint is con-structed in accordance with the Power Piping Code ANSIB31.1 (see ASB 3-1 B.2.c.(4)), the piping shall either beof seamless construction with full radiography of all cir-cumferential welds, or all longitudinal and circumferentialwelds shall be fully radiographed.(2) Welded attachments, for pipe supports or other purposes, to theseportions of piping should be avoided except where detailed stressanalyses, or tests, are performed to demonstrate compliance with thelimits of B.L.b.(1).(3) The number of circumferential and longitudinal piping welds andbranch connections should be minimized. Where guard pipes are used,the enclosed portion of fluid system piping-should be seamless con-struction and without cfrcumfergnjtTal welds unless specific accessprovisions are made to permit inservice volumetric examination ofthe longitudinal and circumferential welds.(4) The length of these portions of piping should be reduced to theminimum length practical.(5) The design of pipe anchors or restraints (e.g., connections to con-tainment penetrations and pipe whip restraints) should not requirewelding directly to the outer surfdce of the piping (e.g., fluedintegrally forged pipe fittings may be used) except where suchwelds are, 100 percent volumetrically, examinable in service and adetailed stress analysis is performed to demonstrate compliancewith the limits of B.1.b.(1).(6) Guard pipes provided for those portions of piping in the containmentpenetration areas should be constructed in accordance with the rulesof Class MC, Subsection NE of the ASME Code,Section III, where theguard pipe is part of the containment boundary. In addition, theentire guard pipe assembly should be designed to meet the followingrequirements and tests:(a) The design pressure and temperature should not be less than themaximum operating pressure and temperature of the enclosed pipeunder normal plant conditions.3.6.2-12Rev. 2 -June 1987 I: I I .:' +i(b) The Level C stress limits in NE-3220, ASME Code, SectionlIII, should not be exceeded under the loadings associatedwith containment design pressure and temperature in com-bination with the safe shutdown earthquake.(c) Guard pipe assemblies should be subjected to a singlepressure test at t-'pressure not less than its designpressure.(d) Guard pipe assemblies should not prevent the access re-quired to conduct the inservice examination specified inB.1.b.(7).' Inspection ports, if used, should not belocated in that portion of the guard pipe through theannulus of dual barrier containment structures.(7) A 100% volumetric inservice examination of all pipe welds shouldbe conducted during each inspection interval as defined inIWA-2400, ASME Code,Section XI.c. Postulation of Pipe Breaks In Areas Other Than Containment Penetration(1) With the exception of those portions of piping identified inB.l.b, breaks in Class I piping (ASME Code,Section III) shouldbe postulated at the following locations in each piping andbranch run:(a) At terminal ends3(b) ,At intermediate locations where the maximum stress range2as calculated by Eq. (10) exceeds 2.4 S(c) At intermediate locations where the cumulative usage factorexceeds 0.1.As a result of -piping reanalysis due to differences between thedesign configuration and the as-built configuration, the: highest stress or cumulative usage factor locations may be.3.Extremities of- piping runs that connect to structures, components (e.g.,vessels, pumps, valves), or pipe anchors that act as rigid constraints topiping motion and thermal expansion. A branch connection to a main piping runis a terminal end of the branch run, except where the branch run is classifiedas part of a main run in the stress analysis and is shown to have a significanteffect on the main run' behavior. In piping runs which are maintained pres-surized during normal plant conditions for only a portion of the run (i.e., upto the first normally closed valve) a terminal end of such runs is the pipingconnection to this closed valve...-3.6.2-13Rev. 2 -June 1987 shifted; however, the initially determined intermediate breaklocations need not be changed unless one of the followingconditions exists:(1) The dynamic effects from the new (as-built) intermediate Ibreak locations are not mitigated by the original pipewhip restraints and jet shields.(ii) A change is required in pipe parameters such as major dif-ferences in pipe size, wall thickness, and routing.(2) With the exceptions of those portions of piping identified in B.L.b.,breaks in Class 2 and 3 piping (ASME Code,Section III) should bepostulated at the following locations in those portions of eachpiping and branch run:(a) At terminal ends.(b) At intermediate locations selected by one of the followingcriteria:(1) At each pipe fitting (e.g., elbow, tee, cross, flange, andnonstandard fitting), welded attachment, and valve. Wherethe piping contains no fittings, welded attachments, orvalves, at one location at each extreme of the piping runadjacent to the protective structure.(11) At each location where stresses calculated2 by the sum ofEqs. (9) and (10) in NC/ND-3653, ASME Code,Section III,exceed 0.8 times the sum of the stress limits given inNC/ND-3653.As a result of piping reanalysis due to differencesbetween the design configuration and the as-builtconfiguration, the highest stress locations may beshifted; however, the initially determined intermediatebreak locations may be used unless a redesign of thepiping resulting in a change in pipe parameters (diameter,wall thickness, routing) is required, or the dynamiceffects from the new (as-built) intermediate breaklocations are not mitigated by the original pipe whiprestraints and jet shields.(3) Breaks in seismically analyzed non-ASME Class piping are postulatedaccording to the same requirements for ASME Class 2 and 3 piping4above4Note that in addition, breaks in non-seismic, that is, non-Category I piping,are to be taken into account as described in Section II.2.k. "Interaction ofOther Piping with Category I Piping" of SRP 3.9.2.3.6.2-14Rev. 2 -June 1987 (4) Applicable to (1), (2) and (3) above:If a structure separates a high energy line from an essentialcomponent, that separating structure should be designed towithstand the consequences of the pipe break in the high-energy line which produces the greatest effect at the structureirrespective of the fact that the above criteria might notrequire such a break location to be postulated.(5) Safety-related equipment must be environmentally qualified inaccordance with SRP 3.11. Required pipe ruptures and leakagecracks (whichever controls) must be included in the design basesfor environmental qualification of electrical and mechanicalequipment both inside and outside the containment.d. The designer should identify each piping run he has consideredto postulate the break locations required by B.1.c. above. Incomplex systems such as those containing arrangements of head-ers and parallel piping running between headers, the designer shouldidentify and include all such piping within a designated run inorder to postulate the number of breaks required by these criteria.e. With the exception of those portions of piping identified inB.L.b, leakage cracks should be postulated as follows:(1) For ASME Code,Section III Class 1 piping, at axial lo-cations where the, calculated stress range2 by Eq. (10)in NB-3653 exceeds 1.2 S f(2) For ASME Code,Section III Class 2 and 3 or nonsafety class (notASME Class 1, 2 or 3) piping, at axial locations where thecalculated stress2 by the sum of Eqs. (9) and (10) inNC/ND-3653 exceeds 0.4 times the sum of the stress limits givenin NC/ND-3653.(3) Nonsafety class piping which has not been evaluated toobtain stress information should have leakage crackspostulated at axial locations that produce the most severeenvironmental effects.2. Moderate-Energy Fluid System Pipinga. Fluid Systems Separated from Essential Systems and ComponentsFor the purpose of satisfying the separation provisions ofplant arrangement as specified in B.L.a. of BTP ASB 3-1, areview of the piping layout and plant arrangement drawings3.6.2-15Rev. 2 -June 1987 should clearly show that the effects of through-will leakage..cracks at any location in piping designed to seismic and noh-seismic standards are isolated or physically remote from essen-tial systems and components.b. Fluid System Piping In Containment Penetration AreasLeakage cracks need not be postulated in those portions ofpiping from containment wall to and including the inboard oroutboard isolation valves provided they meet the requirementsof the ASME Code,Section III, NE-1120, and the stresses cal-culateO2 by the sum of Eqs. (9) and (10) in ASME Code, SectionIII,, NC-3653 do not exceed 0.4 times the sum of the stresslimits given in NC-3653.c. Fluid Systems In Areas Other Than Containment Penetration(1) Leakage cracks should be postulated in piping locatedadjacent to structures, systems or components important tosafety, except:(a) where exempted by B.2.b. or B.2.d.0(b) for ASME Code, Section IlI, Class 1 piping, thestress range calculated2 by Eq. (10) in NB-3653 isless than 1.2 Sm.(c) for ASME Code,Section III, Class 2 or 3 andnonsafety class piping, the stresses calculated2 bythe sum of Eqs. (9) and (10) in NC/ND-3653 are lessthan 0.4 times the sum of the stress limits given inNC/ND-3653.(2) Leakage cracks, unless the piping system is exempted by (1)above, should be postulated at axial and circumferentiallocations that result in the most severe environmental con-sequences.(3) Leakage cracks should be postulated in fluid system pipingdesigned to nonseismic standards as necessary to satisfy8.3.d. of BTP.ASB 3-1.d. Moderate-Energy Fluid Systems in Proximity to High-EnergyFluid SystemsLeakage cracks need not be postulated in moderate-energyfluid system piping located in an area in which a break in3.6.2-16Rev. 2 -June 1987

high-energy fluid system Piping is. postulated, provided such leakagecracks wouId not result In more- limiting environmental conditionsthan the high-energy piping break'. .Where a postulated leakage crackin the' moderate-energy fluid system piping results in-more limitingenvironmental conditions than the break, in proximate high-energyfluid system piping, the provisions of B.2.c. should be applied.e. Fluid Systems Qualifying as High-Energy or Moderate-Energy SystemsLeakage cracksinstead of breaks ...may. be postulated in the piping oflthose fluid systems that qualify as high-energy fluid systems for-only short operational period5 but, qualify as moderate-energy fluidsystems for the major operational period.3. Type of Breaks and Leakage Cracks in Flui'd System Pipinga. Circumferential Pipe BreaksThe following circumferential breaks should be postulatedindividually' in high-energy fluid system piping at"'the locationsspecified in B.1 of this position:(1) Circumferential breaks should be postulated in .'fluid systempiping'and branch'runs exceedinga intoinal pi-pe tize-Of I Inch,except where the maximum stress range- exceeds'-.the limitslspecified in B.l.c.(1) and B.l.c.(2) but the circumferentialstress range is at least 1.5 times the axial- stress range.Instrument lines, one Inch .and less nominal pipe _or tubing sizeshould meet the provisions of Regulatory Guide 1.11.(2) Where break locations- are selected without -the benefit ofstress calculations,' breaks shoul'd be: postulated at the pipingwelds to each fitting, valve, or welded attachment.5Tfieoperational period is considered'"short"1 if the fraction of time that thelsystem operates'wi.thin the pressure-temperature.conditions specified for high-energy fluid systems is about 2 percent. of the ti'me that the system operatesas a moderate-energy fluid system (e.g., systems such as the reactor decayheat removal system qualify-Aas modetate-energy fluid systems; however, systemssuch as auxiliary feedwater systms operated curing PWR reactor startup, hotstandby, or shUtdown qualify as high-energy fluid systems).I...I t : .. -, ...-..3.6.2-17Rev. 2 -June 1987 (3) Circumferential breaks should be assumed to result in pipeseverance and 'separation amounting to *at least a one-diameterlateral displacement of the ruptured piping sections unlessphysically limited by piping restraints, structural members, orpiping stiffness as may be demonstrated by inelastic limitanalysis (e.gi.,.a plastic hinge in the piping is not developedunder loading).(4) The dynamic force of the jet discharge at the break locationshould be based on the effective cross-sectional flow area ofthe pipe and on a calculated fluid pressure as modified by ananalytically or experimentally determined thrust coefficient.Limited pipe displacement at the 'break location, linerestrictions, flow limiters, positive pump-controlled flow, andthe absence of energy reservoirs may be taken into account, asapplicable, in the reduction of Jet discharge.(5) Pipe whipping should be assumed to occur 'in the plane definedby the piping geometry and configuration, and to initiate pipemovement in the direction of the Jet reaction.b. Longitudinal Pipe BreaksThe following longitudinal breaks should be postulated in high-eneryfluid system piping at the locations of the circumferential breaksspecified B.3.a'.:(1) Longitudinal breaks in fluid system piping and branch runsshould be postulated in nominal pipe sizes, 4-inch and larger,except where the maximum stress range exceeds the limitsspecified in B.1.c.(1) and B.1.c.(2) but the axial stress rangeis at least 1.5 times the circumferential stress range.(2) Longitudinal breaks need not be postulated at terminal ends.(3) Longitudinal breaks should 'be assumed to result in an axialsplit without pipe severance. Splits should be oriented (butnot concurrently) at two diametrically opposed points on thepiping circumference such that the Jet reactions cause out-of-plane bending -of the piping configuration. -Alternatively, asingle split may be assumed at the section of highest tensilestress 'as determined by detailed stress analysis (e.g., finiteelement analysis).(4) The dynamic force of the fluid Jet discharge should be based ona circular or elliptical (2D x 1/2D) break area equal to theeffective cross-sectional flow area of the pipe at the breaklocation and on a calculated fluid pressure modified by an3.6.2-18Rev. 2 -June 1987

• t Janalytically or experimentally determined thrust coefficient asdetermined for a circumferential break at the same location.Line restrictions, flow limiters, positive pump-controlledflow, and the absence of energy reservoirs may be taken intoaccount as applicable, in the reduction of Jet discharge.(5) Piping movement should be assumed to occur in the direction ofthe jet reaction unless limited by structural members, pipingrestraints, or piping stiffness as demonstrated by inelasticlimit analysis.c.- Leakage CrackLeakage cracks should be postulated at those axial locationsspecified'in B.1.e for high-energy fluid system piping and in thosepiping systems not exempted in B.2.c.(1) for moderate-energy fluidsystem piping.-(1) Leakage *cracks need not be postulated In 1 inch and smallerpiping.(2) For high-energy fluid system piping, the leakage cracks shouldbe postulated to be in those circumferential locations thatresult in the most severe environmental consequences. Formoderate-energy fluid system piping, see B.2.c.(2).(3) Fluid flow from a leakage crack should be based on a circularopening of area equal to that of a rectangle one-half pipe diam-eter in length and one-half pipe wall thickness in width.(4) The flow from the leakage crack should be assumed to result Inan environment that wets all unprotected components within the-- compartment, with consequent flooding in the compartment and'communicating compartments. Flooding effects should be deter-mined on the basis of a conservatively estimated time period-re-quired to effect corrective actions.C. REFERENCES1. 10'CFR Part 50, Appendix A, General Design Criterion 4, 'Environmentaland Missile Design Basis."2. ABoiler and Pressure Vessel Code," Sections III and XI, American Society2 of Mechanical Engineers, 1986 Edition'. S e3. Regulatory Guide 1.11, "Instrument Lines Penetrating Primary ReactorContainment."3.6.2-19Rev. 2 -June 1987 LIST OF RECENTLY ISSUED GENERIj LETTERSGenericLetter No.Subi ectDate ofIssuanceIssued ToGL 87-10GL 87-09GL 87-08GL B7-07GL 87-06GL 87-05GL 87-04GL 87-03GL 87-02IMPLEMENTATION OF 10 CFR 06/12/8773.57, REQUIREMENTS FOR FBICRIMINAL HISTORY CHECKSSECTIONS 3.0 AND 4.0 OF THE 06/04/87STANDARD TECHNICALSPECIFICATIONS ON THEAPPLICABILITY OF LCO ANDSURVEILLANCE REQUIREMENTSIMPLEMENTATION OF 10 CFR 73.55 05/11/87MISCELLANEOUS AMENDMENTS ANDSEARCH REQUIREMENTSINFORMATION TRANSMITTAL OF 03/19/87FINAL RULEMAKING FOR REVISIONSTO OPERATOR LICENSING-1OCFRS5AND CONFORMING AMENDMENTSTESTING OF PRESSURE ISOLATION 03/13/87VALVESREQUEST FOR ADDITIONAL 03/12/87INFORMATION-ASSESSMENT OFLICENSEE MEASURES TO MITIGATEAND/OR IDENTIFY POTENTIALDEGRADATION MKITEMPORARY EXEMPTION FROM 03/06/87PROVISIONS OF THE FBI CRIMINALHISTORY RULE FOR TEMPORARYWORKERSVERIFICATION OF SEISMIC 02/26/87ADEQUACY OF MECHANICAL ANDELECTRICAL EQUIPTMENT INOPERATING REACTORS, USI A-46VERIFICATION OF SEISMIC 02/19/87ADEQUACY OF MECHANICAL ANDELECTRICAL EQUIPMENT INOPERATING REACTORS (USI A-46)ALL POWERREACTORLICENSEESALL LIGHTWATER REACTORLICENSEES ANDAPPLICANTSALL POWERREACTOR.LICENSEESALL FACILITYLICENSEESALL OPERATINGREACTORLICENSEESLICENSEES OFOR'S,APPLICANTS FOROL'S, ANDHOLDERS OFCP'S FOR BWRMARK ICONTAINMENTSALL POWERREACTORLICENCESALL LICENSEESNOT SUBJECT TOUSI A-46REQUIREMENTSALL HOLDERS OFOPERATING ^.LICENSES NOTREVIEWED TOCURRENT, JLICENSINGCRITERIA ONSEISMICQUALIFICATIONOF EQUIPMENT