ML20236D567
| ML20236D567 | |
| Person / Time | |
|---|---|
| Issue date: | 08/21/1986 |
| From: | Ross D Office of Nuclear Reactor Regulation |
| To: | Sniezek J Committee To Review Generic Requirements |
| Shared Package | |
| ML20236D569 | List: |
| References | |
| NUDOCS 8707300526 | |
| Download: ML20236D567 (20) | |
Text
{{#Wiki_filter:_ _ _ UNITED STATES - ?/ ( NUCLEAR REGULATORY COMMISSION - A)c. % - , f 3 . wAsmNGTON, D. C. 20655 9 6 4 x....J AUGts q MEMORANDUM FOR: James H. Sniezek, Chairman. Comittee to Review Generic Requirements FROM: Denwood F. Ross, Acting Director Office of Nuclear Regulatory Research
SUBJECT:
REQUEST FOR CRGR REVIEW OF REVISED SRP SECTION 3.6.2, " DETERMINATION OF RUPTURE LOCATIONS AND DYNAMIC EFFECTS ASSOCIATED WITH THE POSTULATED RUPTURE OF PIPING" ] This complies with the July 30, 1985 memorandum from Minogue to Dircks j 1 entitled " Plan to Implement Piping Review Comittee Recommendations." According to that memorandum, we have prepared a revision to SRP 3.6.2 j covering recommendations from the Piping Review Comittee relating to: J i arbitrary intermediate pipe breaks:and associated environmental qualification requirements. The purpose of this present memorandum is to obtain CRGR j ' approval to. publish in the Federal Register the proposed revision with the aim of acquiring public coment. It is requested that this item be placed on the CRGR agenda at an early date. . Volume 5 of NUCEG-1061, " Report of the U.S. Nuclear Regulatory Comission . Piping Review Comittee". April 1985, contains the following statements and ,j recommendation: " Arbitrary Intermediate Breaks Pipe rupture protection devices can introduce many negative effects ~en plant operations and do not contribute to the plant safety as originally intended. Therefore, deletion of the requirement.to postulate arbitrary 1 intermediate _ breaks and to protect against the dynamic effects of jet ] impingement and pipe whip is warranted. Environmental qualification of equipmentinthevicinityoftheselines[witharbitraryintermediate breaks deleted) should be reviewed on a case-by-case basis until de-finitivecriteriaaredeveloped[intheSRP). The Piping Review Comittee recomends that Section 3.6.2 (MEB 3-1) of the SRP be revised to incorporate proposed changes eliminating the requirements for mechanical pipe rupture protection against arbitrary intermediate breaks in all systems, including those subject to stress corrosion cracking, fatigue, and dyncmic loads. The SRP should include definitive criteria related to environmental qualification of equipment." a i About fifteen nuclear power utilities have requested relaxations relating to ) arbitrary intermediate pipe break requirements and it is expected that other i 3 requests will be received before this revision is completed. B707300526 060904 )I PDR REVGP NRCCRGR MEETINGO96 PDR 1 ,,,,,.;~~,,,,,,~----- -"~~ ~ ~'~~ ~ ~ "
it-4 i1 Li i ,j i ..r ; Enclosure'l contains the proposed'. revision to Branch Technical Position MEB 3-1 of SRP 3.6.2. This: revision contains definitive criteria for environmental ] qualification of equipment as recomended by the Piping Review Committee. ej Besides addressing the' arbitrary intermediate break recommendation from'the j -l ~ Piping Review Comittee, the, staff has updated the stress limits and other f1 citations to the ASME Code in S.RP 3.6.2 using a review and recommendations - j explicitly prepared for this revision by E. C. Rodabaugh, a noted authority on j; o Since the purpose of the update is only the interpretations of the ASME Code. to make the revision ~of SRP 3.6.2 consistent with the most recent ASME Code, and because the Code is annually endorsed by regulation, we have not calculated ?; j l or assigned any value-impacts for.this part of the revision, 3 e the usage' factor to be employed with ] j Initially, we proposed a new value for l The proposed usage factor would have been a relaxation which Class 1 piping. 1 would have permitted the elimination of additional pipe ruptures in Class 1 . These additional pipe ruptures'are not classified as arbitrary in-l ) 4 l piping. The usage factor relaxation was not. treated by termediate pipe ruptures. the' Piping Review Comittee and was not heretofore. brought before senior NRC However, in obtaining staff review of the revised usage factor, 1 The -i management. we received three negative coments concerning this proposed relaxation. decision was made.to withdraw the revision to the' usage factor pending evalua-i tion of. cited deficiencies in.the ASME fatigue design curves.s i j - contains the Sumary of Proposed Generic Requirements for CRGR d under. contract with Lawrence Livermore National,gulatory Analysis perfom review,:while Enclosure 3 contains the Re Laboratory. Based.on my review of. y the proposed SRP revision and its regulatory analysis, I have determined that' public health and safety will.be' increased by an unquantified amount due to y w i improved inservice inspection and reduced opportunities for inadvertent 1 restraint of thermal growth. 'I have also found substantial cost savings to j industry from both implementation and' operational sources equal to a minimum of.$41 million. Averted occupational radiation exposures are estimated as-lj l 4 r 17,000 man-rem.' y, Besides avoiding revisions concerning the usage factor, four other potential These issues issues raised by NRC staff comenters are likewise not treated. 1! are: l f 4 1. Pipe-to-pipe impact criteria d4 2. Dynamic analysis models for jet thrust i j Size of leakage cracks j f 3. Allowable stresses between outboard isolation valve and first i 4. restraint. These issues merit our attention, and I recomend that they be addressed in f the near term under separate revisions to SRP 3.6.2. No regulatory analyses j j i are available for these issues, and it remains to be determined whether and { 4 i s .. s_
l In order to avoid delays how to implement. revisions concerning these issues'.k relaxations, we are moving -with. achieving the arbitrary intermediate brea forward with a limited revision at this time. This decision and this revision have been approved in NRR. For further information, contact John O'Brien (X37854) of the Engineering Branch, DES. Denwood F. Ross, Acting Director ~ Office of Nuclear Regulatory Research.
Enclosures:
As stated '1 q N i l a I d- ~ ~-
1 4 Explanation s. Revision 2 of SRP 3.6.2 (July 1986) This revision consists to a large degree of nine (9) inserts designated A 1. through I', and associated deletions. There are other changes, however, that are introduced without inserts. The following' inserts deal with making PEB 3-1 of SRP 3.6.2 consistent 2. with the latest ASME. Code.and reflect the efforts of E.C. Rodabaugh: :A, j B, C, F, G, H and I. i) The deletion without insert of B.I.C.(1)(d) on page 3.6.2-13 eliminates . 3. - arbitrary intermediate pipe ruptures in Class 1 piping. Also, the deletion with' insert of B.1.C.(2)(b)(ii) on page 3.6.2-14 eliminates. arbitrary intermediate pipe ruptures in Class 2 and 3 piping. .) .These are the only two places where requireme'nts for locating arbitrary intermediate pipe ruptures are revised. Insert D~ revises the position on ruptures in non nuclear class piping. 4. 1 Insert E revises requirements for equipment qualification when aribtrary J 5. . intermediate pipe ruptures are eliminated. j i
~ l m o. 4
- )
F.j ..m i SRP 3.6.2' '(Revision 2) .4 ' f INSERT A l (Footnote) 8For those loads and conditions in which Level' A and Level B stress limits $[1 j 'have been speci.ied in the' Design Specification (including the operating _ f J l basis. earthquake). 'l l INSERT B i The level-C stress limits in NE-3220,' ASME Code, Section III, should not 3 be.' exceeded under the loading associated with containment design pressure. j l and; temperature in combination.with the safe shutdown earthquake. q [; INSERT C H, l a .i At each location where stresses calculated 2 by the sum of Eqs. (9) and ^ (10)inNC/ND-3653,ASMECode,SectionIII, exceed 0.8timesthesumofthe-l
- stress limits given.in NC/ND-3653."
INSERT D Breaks in-seismically analyzed non-ASME Class piping are postulated ac-J J 2 cording to the'same requirements for ASME Class 2 and 3 piping'above. s INSERT E ( 5)' Safety related equipment must be environmentally qualified in i accordance with SRP.3.11, regardless of changing' requirements for 1 postulated pipe ruptures. However, with respect.to pipe rupture effects, . equipment' qualification is treated as follows: Required pipe ruptures and leakage cracks'(whichever controls) are the design bases for environmental qualification of electrical and mechanicalcequipment both inside and outside the containment. f INSERT F ,j 'With the exception of those portions of piping identified in B.I.b, e. leakage cracks should be postulated as follows. ) i '(1) For ASME Code, Section III Class 1 piping, at axial locations j where the calculated stress ranger by Eq. (10) in NB-3653 ex-1 a ceeds l'.2S. j m a 4 ~ ~ M*: ._,es.,.w.w-...m..e,,-
<t ,.s (2)I For'ASME Code, Section III Class 2'and.'3 or nonsafety class pip-ing, at axial locations where.the calculated stresse by the sum of Eqs. (9)'and (10)'in NC/ND-3653 exceeds 0.4 times . the sum of the stre,ss-limits given in NC/ND-3653. (3) Nonsafeti class piping which has not been evaluated to obtain stress information should have leakage cracks ~ postulated at axial locations that produce the most severe environmental ef-fects,. 5 t INS'ERT G' Leakage cracks need not.be postulated in those portions of piping from J containment wall to and including the inboard or outboard isolation valves d 1 provided they meet the' requirements of the'ASME! Code, Section III, NE-~1120. and the stresses calculated: by.the sum.of Eqs. (9) and (10) in J 4 ASME Code, Section III, NC-3653 do'not exceed 0.4 times the sum of the stress' limits given in NC-3653.- INSERT H'
- 1) Leakage cracks should be postulated in piping located adjacent to
( structures, systems or components important to safety, except: ' A (a): where exempted.by.B'.2.b or B.2.d, i for ASME Code, Sectfon'!II, Class 1 piping, the stress range 4 (b) calculated 2 by Eq. :(10) in NB-3653 is less than 1.2S;, for ASME Code, Section III, Class 2 or 3 and non-safety class (c) piping, the stresses calculated: by the~ sum of Eqs. (9) and (10) ~in.NC/ND-3653 are less than 0.4 times the sum of the stress limits given in NC/ND-3653. Leakage cracks, unless the piping system is exempted by (1) above, (2) should be postulated at axial' and circumferential locations that re-sult in the most severe environmental consequences. INSERT I c.. Leakage Cracks Leakage cracks shoul,d be postulated at those axial locations spec- 'ified in B.I.e.for high energy fluid system piping and in those pip-ing systems not' exempted in B.2.c.(1) for moderate energy fluid sys- -tem piping. t 'k 9 "M89W gg9_ _
I + 1 .. ~ i s t (1)' Leakage cracks need'not.be postulated in 1 inch and smaller pip-ing. '(2) For high' energy fluid system piping. the leakage l cracks should be po.stulated to be.in those circumferential locations that re-sult in the most severe environmental consequences. For moder-ate energy fluid system piping, see 8.2.c.(2).. (3) Fluid flow from:a leakage crack should bs based on a circular )j ' opening of f area equal to that of a rectangle one-half pipe diam-d eter in length'and one-half pipe wall thickness in width. 1 (4).The flow from the leakage crack should be assumed to result in 4 an environment that wets all unprotected components within the i compartment, with consequent flooding in the compartment and-i . Flooding effects should be de- ~ communicating compartments. termined on the basis of a conservatively estimated time. period j required to effect corrective actions. ' 1 1 Et 1, ,c.-.---
) / 'u ) structures, systems and components important to safety that.are l l. in close proximity to the postulated pipe rupture will be pro-- 'q. tected. The design will be of a nature to mitigate the conse-quences of pipe ruptures so thatL the reactor can be safely shut down and maintained in a safe shutdown condition'in the event - of a postulated rupture of a high or moderate energy piping system inside or outside of containment. V.. IMPLEMENTATION l Th'e following is intended to provide guidance to applicants and licensees regarding the NRC staff's plans for using this SRP section. Except in those cases in which the applicant proposes an aiceptable alternative method for' complying with specified portions of the Commission's regulations, the method described herein will be used by the staff in its evaluation of conformance with Commission regulations. For protection against postulated pipe ruptures outside containment, Reference 2 l includes the area of concern in this position and has been used for those plants { for which construction permit applications were tendered beforeLJuly 1,1973. )l Reference 3 specifically emphasizes protection via plant arrangement and layouts utilizing the concept of physical separation to the extent practical and has been used for those plants for which construction permit applications were t tendered af ter July 1,1973 and before July 1,1975 as specified in Section B.4 of BTP ASB 3-1. - BTP MEB 3-1 has been used for.all construction permit applica-j tions, in lieu of References 2 and 3, since July 1,1975 and should be used for future applicat 9,._. g I W M%,j. to c%nc s=o.C^!4 D Pta ^"tb ""'6 " l VI. REFERENCES ( % e-s9, 1. 10 CFR Part 50, Appendix A, General Design Criterion 4. " Environmental i and Missile Design Bases." ' 2. Attachment to letter from A. Giambusso, December 1972, " General Information Required for Consideration of the Effects of a Piping System Break Outside 1 Containment," Appendix B to BIP ASB 3-1 (attached to SRP Seption 3.6.1). 1 3. Letter from J. F. O' Leary,' July 12, 1973, and attachment entitled, " Criteria for Determination of Postulated Break and Leakage' Locations'in High and Mcderate Energy fluid Piping Systems Outside of Containment Structures," Appendix C to BTP ASB 3-1 (attached to SRP Section 3.6.1). 4. Branch Technical Position MEB 3-1, " Postulated Rupture locations in Fluid System Piping Inside And Outside Containment," attached to this SRP section. 5. Branch Technical Position ASB 3-1, " Protection Against Postulated Piping f ailures in Fluid Systems Outside Containment" (attached to SRP Section 3.6.1). o 6. F. J. Moody, " Prediction of Blowdown and Jet Thrust Forces," ASME Paper 69 HT-31, August 6, 1969. 7. NUREG-0609, " Asymmetric Blowdown Loads on PWR Primary Systems," resolution of Generic Task Action Plan A-2.
- 3. 6. 2-9 Rev. 1 - July 1981
1 BRANCH TECHNICAL P051110N Mll 3-1 POSTULAllD RUPTURE t0CA110N5 IN FLUID SYSTEM PIPING IN5IDE AMD OU1510E CONTAINKEK1 i A. aACKGR0hND a o This position on pipe rupture postulation is intended to comply with the require-sents of Generai Oesign Criteria 4, of Appendia A to 10 CFR Part 50 for the It is recognized that design of nuclear power plant structures and components. pipe rupture is a rare event which may only occur under unanticipated conditions, such as those which might be caused by possible design, construction, or opera-Our tion errors; unanticipated loads or unanticipated corrosive environments. oburvation of actual piping f ailures have indicated that they generally occur at high stren and f atigue locations, such as at the tersiral ends of a piping The rules of this system at its connection to the nozzles of a component. position are intended to utilize the available piping design information by postulating pipe ruptures at locations having relatively higher potential for f ailure, such that an adequate and practical level of protection say be achieved. B. BRANCH TECHNICAL. POSITION i 1. High-Energy Fluid Systems Piping Fluid Systems Separated From Essential Systems and Components a. For the purpose of satisfying the separation provisions of plant arrangement as specified in 8.1.a of Branch Technical Position (BTP) ASB 3-1, a review of the piping layout and plant arrangement drawings l should clearly show the effects of postulated piping breaks at.any location are isolated or physically remote free essential systems and -{ components.8 At the designer's option, break locations as determined from B.Lc. of this position say se assumed for this purpose.. b. Fluid System Piping in Containment Penetrattor. Areas Breaks and cracks need not be postulated in those portions of' piping f from containment wall to and including the inboard or outboard isola-tion valves provided they meet the requireme.ts of the ASME Code, Section 111, Subarticle HE-1120 and the follo.ing additional design requirernents: (1) The following design stress and fatigue limits should not be exceeded: For ASME Code, Section 111, Class 1 Piping (a) The maximum stress range between any two load sets (including the zero set) should not exceed 2.4 5,, and should be t n II, '5ystems and components required to shut down the reactor and mitigate the consequences of a postulated pipe rupture without of fsite power. 1 R5W A UcNA EQ 3.6.2-10 Rev.1 - July 1981
..r
- i-3 it'
' jl-1 4 i
- m : m :: n a!
a Ili the calculated maximum stress range of Eq. (10) exceeds J! -) 2.4 5,, the stress ranges calculated by both Eq. (12) and y En. (1Q.n Paragraph NB-3653 should meet the limit of 2.4_5" i .y.- I$t/Iboulative usage f actor. should be less than 0.1. 4 U' (b) t, The maximum stresy, as calculated by Eq. (9). in6 ) u; -]# j
- (c) NS-3652 under;t.Agloadings resulting from a postulated piping f
f ailure beyond thestr portions of piping should not exceed M except that following a failure outside containment, i 7A l ~. 2 M the pTpe between the outboard isolation: valve and the first A rgENWYh9 s li restraint may be' permitted higher stresses provided a plastic o 1 A hinge is not formed and operability of the valves with such j' 12.53 ad'/ M % stresses is assured in accordance with the requirementsPricar.i v r 1.% $ specified in SRP Section 3.9.7 j j b/ Ms which he deflection limited by whip ~ restraints. I.7 t .,f' For ASME' Coud, section 111', Class 2 Piping j N-1 1 i The maximum stress,MWs calculated by the-simw of Eq. (9) and (10) in Paraymph NC-3652, ASME Code, Section1111, con-
- j j (d) side 1ing those loads and conditions thereof'for'which level A
)
- .y and level B stresd limits have been specified in the system's sustained loads, occasional' l
i Design Specification (i.e. j loads, and thermal expansion) including an OBE event. should The S and54areallowable i r not ex g h o.4 h$g A stresses,at maximum (hot) temperature and allowanle stress g ,)' Article NC-3600 of the ASME Code, Section III. ra J J% /. 9 l MC The maximum stress, as calulated by Eq. (9) in 6, fei ,j ' 54M under the 16adings resulting from a postulated piping p' g failure of fluid system piping beyond these oortior.s oL2 29 Sb g _.g[D 'I piping spersid not' exceed q. %e. ess s I 1 Primary loads include those which are deHection ijmited The exceptions permitted in (c) above f by whip restraints. i may also be applied provided that when the piping s w r in accordance with the Pcwer Piping Code ANSI B31.1 (see 1 ASB 3-1 B.2.c(4),' the pipGig shall either be of seamless l construction with full radiography of all circumferential i Gelds, or all longitudinal and circumferential welds shall m s - m i1 be fully radiographer. i j Welded attachments, for pipe ' supports or other purposes, to these 6 (2) por' ions of piping should be " avoided except where detailed stress 4 analyses, or tests, are performed to demonstrate compliance with I the limits of B.1.b(1). a g-g Rev.1 - July 1981 3.6.2-11 .j p b A G n
e 1 .i (3) The' number of circumferential and longitudins' piping welds and ' branch connections should be minimized. Whe e guard pipes are the' enclosed portion of fluiJ systes pising should be. used lV seamless construction and without circuarerertial welds unless. 1 specific access provisions are made to persit inservice volumetric examination of the longitudinal and circumfe ential welds. (4) The length of these portions of piping shou 1c be reduced to the. i sinimum length practical. .e The design of pipe anchors or restraints (e s, connections to (5) containment penetrations and pipe whip rest'afnts) should not the piping require welding directly to the outer surfa:e of,be used) except (e.g.. flued integrally forged pipe fittingi say . here such welds are 100 percent volumetrica'ly examinable in wservice and a detailed stress analysis is pe-formed to demonstrate compliance with the Itaits of B.I.b(1). d Guard pipes provided f or those portions of s' ping in the contain-(6) sent penetration area; should be constructe:: in accordance with 1 the rules of Class MC, Subsection NE of the ASME Code, Section 111, In where the. guard pi,pe is part of the contai:eent boundary. addition, the. entire guard pipe assembly sN:uld be designed to meet the following requirements and tests: / The design pressure and temperature skuld not be less than (a} the saximum operating pressure and taperature of the t j enclosed pipt under normal plant confi ions. ust.e.T B } 1 Guard pipe assemblies should be subje:ted to a' single pres-Y (c) sure test at a pressure not less tha-its design pressure. I Guard pipe assemblies should not pre,ent the ac' cess required (d) to conduct the inservice examinatio-specified in B.I b.(7). Inspection ports, if used, should n:: be located in that portion of the guard pipe through tre annulus of dual barrier containment structures. A 100% volumetric inservice examination. c' all pipe welds should (7) be conducted during each inspection inte.at as defined in IWA-2400, ASME Code, Suf f on XI. y(Ekeaks] Postulation of Pipe W In Areas Other 1*a-Containment Penetration c. (1). With the exceptions of those portions o' piping identified in B.I.b, breaks in Class 1 piping (ASME C:de, Section III) should be postulated at the following locations ir each piping and branch run: 3.6.2-12' Rev.1 - July 1981
g (a) At terminal ends g 8 At intermediate locations where *.he maximum stress range" (b) as calculated by Eq. (10) 6 exceeds 2.4 5,. (c) At intermediate locations where the cumulative usage f actor exceeds 0.1. l As a result of piping reanalysis, g h the initially determined intermediate 'otation break conditions exist: j l 1 (i) Maximum stress ranges or cumulative usage f actors exceed j the threshold levels in (b) or (c) above. i l (ii) A change is required in pipe parameters such as ma,jor differences in pipe size, wall thickness, and routing. 1 .i y 3 j es of piping runs that connect to structures, compo6ents (e.g., vessels, pumps, valves), or pipe anchors that act as rigid constraints to A branch connection to a main piping piping motion and thereal expansion.run is a terminal end of the branc classified as part of a main run in the stress analysis and is shown to have In piping runs which are a significant effect on the main run behavior. maintained pressuriz the run (i.e., up to the first normally closed valve) a terminal end of such runs is the piping connection to this closed valve. .. Y :.. -...... I ~-' y., T' 1 .. 3 6.2:13 Rev. 1.,,, July 1981.
i iI f With the. exceptions of those portions of piping identified in f (2) A5HI Code, Section 111) 8.1.b, breaks in Class 2 and 3 piping (locations in those portiorts should be postulated at the following of each piping and branch run: (a) At terminal ends. (b) ' At intermediate locations selected by one of the following criteria: At each'pi.pe fitting (e.g., elbow,- tee, cross, flange, (1) and nonstandard fitting), welded attachment, and valve. Where the piping contains no fittings, welded attach-ments, or valves, at one location at each extreme of. the piping run adjacent to the protective structure. J INSEM C. (ii)>m i c"Yf MQ&A ....._..m_...,._,...e p' p 1 As a result of piping reanalysis,- the highest stress. > ^dt locations may be shifted;'htwever, the initially kwh ensg'i determined intermediate break locations say be used' ' ' % alm %H j % % PA M h edq M-- (3), TMSEU D m =mha -(4) Applicable to (1), (2) and (3) above: If a structure separates a high energy line from an essential component, 'that separating structure should be designed to with-stand the consequences of the pipe break in the high-energy line . hich produces the greatest effect at the structure irrespective of the f act that the above criteria might not require such.a w 3 break location to be postulated. QMER.T emmespass. 3.6.2-14 Rev. 1 - July 1981 s
- .wm.-
~ _m , m -- - - - - - ~ ~ ~
a i d. The designer should identify ecch piping rur. he has considered to postulate the break locations-eequired 3y 81.c above. In complex L systems such as those containing arrangements of headers and parallel L piping running.between headers, the designer should identify and include all such piping within a designated rvei in order to postulate the, number of breaks. required by these criteria. , - - - - = - _ _ ~.[uSE9.T F - - -. _~ _ - ..---===----~& A" 2. Moderate-Energy Fluid Syster. Piping a. Fluid Systees separated fror Essential Systres and Components For the purpose of satisfying the. separatio. provisions of plant arrangement as specified in B.I.a of BTP A58 3-1, a review of the piping layout and plant arrangement drawirgs should clearly show that-i the offects of through-wall leakage cracks at any location in piping designed to seistic and nonseismic standa-ds are isolated or physically: remote from essential systees and c'omponerts. +a l b. Fluid System Piping In Containment Penetration Areas 1 W 145097 q ~ 2. .ro-2 i c. Fluid Systems in Areas Other Than Contaiment Penetra' tion '.. *) - --.u- ?. i M IOSEE:;r H. ] .:..., r. v., m, L;. M M [pakage cracks should be postulated in fluid syster. piping designed to nonseismic standards as necessary to satisfy B.3.d of BTP ASB 3-1. (0 i 3.6.2-15 Rev. 1 - July 1981
= - - - - - -, - - - _. _ _ _. l 1 Moderate-Energy fluid Systems in Proximity to Hip-Inergy Fluid Systems L d. ) I Cracks need.not be postulated in moderate energy fluid system piping ? Iocated in an area in which a break in high eneruy riutd system piping 15 postulated. provided such Aracks would not result in more 1 tatting Where a 1 environmental conditions than the high energy piping break. y postulated leakage crack in the moderate-energy fluid system piping results in more limiting environmental conditioni than the break in ) prominate high energy fluid system piping, the pecvisions of 8.2.c ~g l should be impplied. Fluid Systems Qualifying as High-Energy or Moderate-Energy Systems 'l e. 4 y be postulated in W laakage cracks instead of breats as high-enerqv fluid the p.iping of those fluid systems that qual' systems for only short operational perio ut qualify as moderate-energy fluid systems for the major operational period. + Type of Breaks' and leakage Cracks in Fluid Systee Piping 3. Circumferential Pipe Breaks j a. j f The following circumferential breaks should be postulated individually I in high-energy fluid system piping at the locations specified in B.1 of this position: (1) Circumferential brtaks shoul.1 be postula in fluid systes pipe size of 1 inch, piping and branch runs exceeding a xceeds the limits except where the maximum stress ran specified in 8.1.c(1) and B.1.c(2) but the circumferential stress ~ Instrument range is ct least 1.5 times the axial stress range. lines, one inch and less nominal pipe or tubing size should meet the provisions of Regulatory Guide 1.11. l Where break locations are selected withoct the benefit of stress l (2) calculations, breaks should be postulated at the piping welds to each fitti valve or welded attachment. i ! I i Circumferential breaks should be assueet to result in pipe (3) severance and separation amounting to at least a one-diameter i lateral displacement of the ruptured pipng sections unless physically limited by piping restraints, structural members, or l 4 f opera ional period is considered *short" if the fraction of time that the 1 system operates within the pressure-temperature conditions specified for _hig_h-1 energy fluid systems is about 2 percent of the time that the system operates as a moderate-energy fluid system (e.g., systees such as the reactor decay heat renoval systes qualify as moderate-energy fluid systems; however, systees such as auxiliary feedwater systems operated during PWR reactor startup, hot standby, or shutdown qualify as high-energy fluid systess). q 3.6.2-16 Rev. 1 - July 1981 L AL)
1 j piping stifiness as may be demonstrated by inela 1 under loading). The dynamic force of the jet discharge et the break location should be based on the effective cross-section (4) analytically or experimentally determined thrust tions, flow.11 miters, positive pump-cor.ieolled flow, and the absence of energy reservoirs may be taken into account, as applicable, in the reduction of jet dis:harge. pipe whipping should be assumed to occr in th (5) movement in the direction of the jet reaction., ~ Longitudinal Pipe Breaks ll b. The following longitudinal breaks should be postulated in high-energy fluid systee piping at the locations of.the circumferential breats 2' n spec) tied in 8.3.a: 1 piping and branch runs should i (1) longitudinal breaks in fluid systes 4-inch and larger, except be postulated in nominal pipe .enceeds the. limits specified where the.saximum stress rangin B.).c(3) and B.I.c(2) but the axial s 1.5 times the circumferential stress range. terumaltwds. longitudinal breaks need not be postulated at q (2) n g 'l Longitudinal breaks should be assmet to result in an axial split without pipe severance. - Splits should be oriented (but (3) not concurrently) at two diametrically opposed points on the piping circumference such that the jet reactions causes out-o Alternatively, a plane bending of the piping confige ation. single split may be assumed at the section of element analysis). The dynamic force of the fluid jet discharge should be based on a circular or elliptical (20 x 1/20) break area e (4) location and on a calculated fluid pressure mod.ified by an analytically or experimentally determined thrust coef ficient as determined for a circumferential b-eak at the same loc Line restrictions, flow limiters, positive pump-controlled flow, and the absence of energy reservoirs may be taken into accoun as applicable, in the reduction of jet discharge. Rev.1 - July 1981 3.6.2-17
l q .g (5)_ Piping movement should be assumed to occur in the direction of. 'the jet reaction unless lialted by structural members, piping ' l l restraints, or. piping stiffness as demonstrated by inclastic Itait analysis. I W SErci t i . ~. q a r m P ' W ?**?- W f N,. =Q??;q:.^y. 4 .w .ii." ~ '~ 1 f f 4 C. REFERENCES I 1. 10 CFR Part 50, Appendix A, General Design Criterion 4 " Environmental ] and Missile Design Basis." 1 2. " Boiler and Pressure Vessel Code
- Section Ill and XI. American Society
. of Mechanical Engineers,'Q9 Sco SEiQ 3. Regulatory Guide 1.11, " Instrument Lines Penetrating Primary Reactor Containment." ~ if I 3.6.2-18 Rev.1 - July 1981 a
a 1 1 1 l .x r 1
SUMMARY
OF PROPOSED GENERIC REQUIREMENTS FOR CRGR REVIEW OFFICE OF NUCLEAR REGULATORY-RESEARCH .DATE: August 1, 1986, RES TASK NO.: MS-602-8 RES TASX LEADER: John A. O'Brien l MSEB, DET, RES ~ TELEPHONE: 301-443-7854 Title of Proposed ' Action i -q Pipe Rupture Requirements for Nuclear Power Plants 1 l Type of Action
- i SRP Revision Category:-
Category 2. The arbitrary intermediate break relaxations of this revision 1 have been requested by about fifteen utilities. Consistency _ demands a j that the SRP reflect current practices and' views. 1 1 ' Statement of the Problem The U.S. Piping Review Committee has. identified a numbe.r of difficulties J( resulting from dynamic effects associated with postulated arbitrary intennediate pipe ruptures. The following is a direct quote from Volume 5 1 of NUREG-1061, " Report of the U.S. Nuclear Regulatory Connission Piping Review Connittoe" April 1985: "As a result of these so called arbitrary intermediate break criteria, many These restraints have resulted pipe whip restraints have been installed. in many problems, which are described as follows: Designing for the two arbitrary Complications in Pipe System Design. o' intennediate breaks is a difficult process because the location of the two highest stress points tends to change several times as a result of thejiterative process involved in the seismic design of piping sys-tems.c The SRP (NUREG-0800, dated July 1981) provides' criteria intend-ed_to reduce the need to relocate intermediate break locations when ~ the high stress points shift as a result of piping reanalysis; in The two locations - practice, these criteria provide little relief. selected by the stress calculation may not be the actual locations of highest stress because the mathematical model may differ from the ac-If the locations are not actually representative, tual piping system. proper protection may not be provided in accordance with the system's ] design. J s-m,< _________________1_____________j
- 7 g
a, n Cost Factors.. As a result of the arbitrary intermediate break re-o- quirements, an excessive _ number of pipe rupture protection devices have to be designed and constructed. The cost for the. design, con-q struction,~and operational service maintenance is estimated to be from $4 million for.nine major systems to $30 million for all systems. Restricted Access for Inservice Inspection..The leak-before-break o, concept can be implemented only when inservice inspection and/or. leak-detection systems provide early detection of possible cracks and potential leaks.in the system. However, the. pipe. rupture protection-devices block access to welds and thus hinder inservice inspection. The removal and reinsta11ation of the pipe rupture protection devices. w will add to the time required to perform necessary inservice 1 i inspections. Restricted access will also increase occupt.tional radiation exposure,during repair, ma.intenance, and decontamination operations.. 3 Increased Heat Loss to Surrounding Environment. Because pipe' whip o-restraints fit closely around the high-energy piping, the piping'insu-y lation must often be cut back in these areas to avoid interferences, thus creating convection gaps adjacent to the restraints. This cre-ates an overall increase in heat loss to the surrounding environment L and is a major contributor to the tendency for msny containments to operate at temperatures near technical specification limits. j 1 o Unanticipated Thermal Expansiori Stress. Pipe rupture protection de-vices are designed not to restrict pipe-free thermal expansion. Should these devices inadvertently come into contact with the pipe itself, unanticipated stresses due to restraint of thermal expansion =can be introduced. The precise consequences of this incident are dif- ]Q ificult to assess. Probabilistic analyses performed by the Lawrence Livennore National Laboratory indicate in general that the resultant reduction in flexibility reduces the overall safety margin of the pipe u l system." . A need exists to remove these difficulties which result from the dynamic effects of postulated arbitrary intermediate pipe ruptures. Since arbitrary intermediate pipe ruptures are required only by Branch Technical l L Position MEB 3-1 of SRP 3.6.2, a revision to this document is appropriate. Additionally, MEB 3-1 (last revised in July 1981).contains citations to stress limits and other factors in the ASME Code which are no longer in effect. To' update SRP.3.6.2 to reflect the latest ASME Code requirements, a review was performed by E. C. Rodabaugh for the NRC and his recommendations have been implemented in this revision of SRP 3.6.2. i [' E . w _s. _
v g P'7 '1 g l. J Objective:,; a 'Tolobtain CRGR approval to publish in the Federal: Register.a proposed re-vision to Branch.Techni, cal Position MEB.3-1 of SRP 3.6.2 with the aim of' ' obtaining public comment., +
- 4 <
Selected Milestones:.(IntermediateMilestonesNotIndicated)_- Sept 1986s Pack?jelsent to CRGR< 'Nov 1986 CRGR. Review of. Proposed Revision. Completed. 4
- ACRS Review of Proposed Revision Completedl
' Jan 1987 Feb 1987' ' Federal Register *!otice of Proposed Revision Published 1Feb 1988' Federal Register Notice of SRP Issuance Published. = Action Proposed' LThis" action. relaxes arbitrary intermediate pipe rupture provisions'in' Branch Technical: Position MEB 3-1.of SRP:3.6.2.. Additionally, stress! ,1 . limits and other ASME citations are updated by this revision. This update = j has no' value-impact because it is already being implemented. Suppcrting Document 1 a .NUREG-1061LVolume-5. April 1985_ -1lj Affected' Plants; . A population of 80 PWR giants (62 operating an'd 18'under construction) with[3 a remaining lifetime of,2689 plant years.and 35 BWR plants (31 operating' and 4 under construction) with a remaining. lifetime of 1157 plant' years was ] ~ q included in this' evaluation.. q Implementation -- . The ' relaxation relating to arbitrary intermediate pipe ruptures is not Applicants and licensees need not develop any technical' mandatory. information nor prepare any value/ impacts to take advantage of the SRP. About fifteen utilities have requested relaxation regarding-revision. Licensees of operating plants arbitrary intermediate pipe ruptures. desiring to eliminate previously required dynamic effects from arbitrary-intermediate pipe ruptures may use the provisions of 10 CFR 50.59. .= t ..a H....,.,___ ..o m.....}}