ML20206E629

EDO Control of Rulemaking Package Re Mods to GDC 4 Requirements for Protection Against Postulated Pipe Ruptures.Initiation of Rulemaking Approved

ML20206E629
Person / Time
Issue date:	12/12/1984
From:	Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO)
To:	Minogue R NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
References
NUDOCS 8606230469
Download: ML20206E629 (36)

Text

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DEC 121S84 MEMORANDUM FOR: Robert B. Minogue Director Office of Nuclear Regulatory Research FROM: William J. Dircks Executive Director for Operations

SUBJECT:

CONTROL OF NRC RULEMAKING By memorandum of February 13, 1984, " Control of NRC Rulemaking by Offices Reporting to the EDO," Offices were directed that effective April 1,1984, (1) all offices under EDO purview must obtain my approval to begin and/or continue a specific rulemaking, (2) resources were not to be expended on rule-makings that have not been approved, and (3) RES would independently review rulemaking proposals forwarded for my approval and make recommendations to me concerning whether or not and how to proceed with the rulemakings.

In accordance with my directive, the following proposal concerning rulemaking has been forwarded for my approval along with recomendations from RES con-cerning the proposal:

Proposal to initiate rulemaking concerning Modifications to GDC-4 Requirements for Protection Against Postulated Pipe Ruptures. (Sponsored by RES - memorandum, Minogue to EDO dated December 4, 1984.)

Initiation of this rulemaking is approved. The NRC Regulatory Agenda (NUREG_0936) should be modified to include this proposal.

(Signed) William J.Dircks William J. Dircks Executive Director for Operations cc: V. Stello J. Roe H. R. Denton R. C. DeYoung J. G. Davis P. G. Norry Distribution:

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\,..... DEC 4 1984 D MEMORANDUM FOR: William J. Dircks i Executive Director for Operations FROM: Robert B. Minogue, Director Office of Nuclear Regulatory Research

SUBJECT:

CONTROL 0F NRC RULEMAKING: RES REVIEW TO BEGIN RES l SPONSORED RULEMAKING Based on our review to begin RES sponsored rulemaking entitled, " Modifications  !

to GDC-4 Requirements for Protection Against Postulated Pipe Ruptures," RES l recommends that this rulemaking be initiated at this time. This recommendation l in draft form has been coordinated with NRR.

A summary of our recommendation is as follows:

o Rulemaking is the only acceptable alternative to continued granting of exemptions to GDC-4. The ELD has expressed the view that extensive use l of exemptions is inappropriate.

I o The results of the preliminary cost and benefits study indicate that this rulemaking will reduce radiation exposure while, at the same time, inservice inspection costs will decrease. However, there will be no increase in the risks to the public.

o Technology has advanced since GDC-4 was written, but application of this l

new technology is restricted by GDC-4. The proposed revision reflects current staff practices and will permit implementation of widely accepted I techniques.

l RES approached the OELD almost a year ago and suggested that this rulemaking l l was unnecessary. Our view was that a reinterpretation of the existing General j l Design Criterion 4 (GDC-4) based on recently completed research would be a more i l prudent course. The OELD stated, however, that the long-time interpretation of l GDC-4 had established a strong precedent which could only be changed by rule-l making. The research quoted above, which would have been the basis for re-l interpretation, was funded by RES at Lawrence Livermore National Laboratory (LLNL) l and is now one of the cited bases for the rulemaking, along with industry funded studies.

l The LLNL investigations estimated the probability of leaking and pipe rupture in l the primary system piping of PWR systems, using advanced fracture mechanics models i

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William J. Dircks DEC 4 E04 and systems engineering concepts. This work was used by the USNRC Piping Review Committee as a basis for establishing the validity of the leak-before-break hypothesis.-

! The complete RES review package has been sent to OED0 (Attention: DEDROGR) j and to the Director, NRR.

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I Robert B. Minogue, Directc Office of Nuclear Regulatory Research I

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MEMORANDUM FOR: William J. Dircks I Executive Director for Operations FROM: Robert B. Minogue. Director '

Office of Nuclear Regulatory Research

SUBJECT:

CONTROL OF NRC RULEMAKING: RES REVIEW TO BEGIN RES SPONSORED RULEMAKING ,

Based on our review to begin RES sponsored rulemaking entitled. " Modifications to GDC-4 Requirements for Protection Against postulated Pipe Ruptures." RES ,

recommends that this rulemaking be initiated at this time. This recommendation 4 in draft form has been coordinated with NRR. f 1 A sisenary of our recommendation is as follows:

o Rulemaking is the only acceptable alternative to continued granting of I exemptions to GDC-4. The ELD has expressed the view that extensive use il of exemptions is inappropriate.

o The results of the preliminary cost and benefits study indicate that this  !

rulemaking will reduce radiation exposure while, at the same time inservice g inspection costs will decrease. However, there will be no increase in the i risks to the public.

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o Technology has advanced since GDC-4 was written, but application of this new technology is restricted by 600-4. The proposed revision reflects j current staff practices and will permit implementation of widely accepted j techniques.

RES approached the OELD almost a year ago and suggested that this rulemaking was unnecessary. Our view was that a reinterpretation of the existing General Design Criterion 4 (GDC-4) based on recently completed research would be a more prudent course. The DELD stated, howcVer. that the long-time interpretation of l GDC-4 had established a strong precedent which could only be changed by rule-making. The research quoted above, which would have been the basis for re-interpretation, was funded by RES at Lawrence Livermore National Laboratory (LLNL) and is now one of the cited bases for the rulemaking, along with industry funded studies. .

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and systems engineering concepts. This work was used by the USNRC Piping Review Comittee as a basis for establishing the validity of the leak-before-break hypothesis. ,

The complete RES review package has been sent to OEDO (Attention: DEDROGR) and to the Director NRR.

~tF Robert 8. Minogue. Director Office of Nuclear Regulatory Research l DISTRIBUTION: i l RES Alpha  !

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TO: F. P. GILLESPIE, CHAIRMAN, RIRB FROM: 0. E, BASSETT, MEMBER, RIRB TITLE OF RULEMAKING: " Modifications to GDC 4 Requirements for Protection Against Postulated Pipe Ruptures" AGREE WITH RECOMMENDATIONS g*

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Against Postulated Pipe Ruptures," sponsored by RES.  ;

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and provide the Chairman, RIRB, with their voting sheets indicating their positions on the rulemaking. $

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will be appreciated. RAMRB will use the voting sheets to assemble the complete RES review package ,

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October 15, 1984 NOTE T0: Harold R. Denton, Director Office of Nuclear Reactor Regulation FROM: Themis P. Speis, Director Division of Safety Technology, NRR

SUBJECT:

LEAK-BEFORE-BREAK RULE In response to your memorandum of June 29, 1984, requesting RES initiation of rulemaking to codify the use of advanced fracture mechanics technology in the regulatory process by modifying GDC 4 requirements for protection against postulated pipe ruptures, RES has prepared the enclosed task control i

form, preliminary draft regulatory analysis, draft NRC Regulatory Agenda entry, and memorandum seeking ED0 approval. I recommend that you concur "

with initiation of this task by signing the task control form. The enclosed material has been reviewed by MTEB, and has the concurrence of DE. RSCB will follow the program to ensure that the schedule is expedited to the extent possible, in order to minimize staff efforts in processing exemptions.

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Themis P. Speis, Director l Division of Safety Technology, NRR

Enclosures:

1. Memorandum for W. Dircks fm R. Minogue

2. Task Control Fom

3. Draft NRC Regylatory Agenda Entry

4. Preliminary Draft Regulatory

(,

Analysis I

i Draft NRC Regulatory Agenda Entry i

TITLE: Modifications to GDC 4 Requirements for Protection Against j Postulated Pipe Ruptures CFR CITATION: 10 CFR 50, Appendix A ABSTRACT:

The proposed rule would allow the exclusion of some pipe ruptures g

presently postulated in the design basis. Only dynamic effects such as pipe whip and jet impingement are affected. Other design ,

requirements, including those relating to environmental j qualification of electrical and mechanical equipment, containment i design and ECCS performance are not influenced by this rule. The proposed rule would permit licensees to use newly developed analytical methods involving widely accepted advanced fracture mechanics theories for determining that certain pipe ruptures need i not be treated in the design basis for dynamic effects.

Implementation of the rule would facilitate the removal of f i

unnecessary pipe whip restraints and jet shields from existing ]

nuclear power plants. This would reduce inservice inspection costs <

and, in addition, would reduce inspector radiation exposure. A benefit derived from the rule would be the avoidance of extensive exemptions to General Design Criteria 4, which would be the only acceptable alternate to the proposed rule. This rule may only require minimum addition and/or modification of the existing text of .

GDC 4. The need and urgency for addressing the issue stems wholely '

! from the widespread acceptance of the analysis results and the research findings pertaining to pipe rupture coupled with increasing confidence in its applicability. Prior to the last few years, there ,

was no sound technical basis for excluding certain pipe ruptures  ;

from the design basis. Now it is clear that it is possible to l defend the exclusion of PWR primary loop double-ended guillotine '

pipe ruptures, and that the scope may be extended to other piping. ,

Two staff years is estimated to undertake this rulemaking. The notice of proposed rulemaking should appear in the Federal Register in July 1985.

l' TIMETABLE:

! Notice of Proposed Rulemaking 7/00/85 1

LEGAL AUTHORITY:

! 42 USC 2201; 42 USC 5846

~

EFFECTS ON SMALL BUSINESS AND OTHER ENTITIES:

Not applicable.

AGENCY CONTACT:

John A. O'Brien Office of Nuclear Regulatory Research Washington, D.C. 20555 ,

301 443-7860 j l ,

r Draft Federal Register Notice NUCLEAR REGULATORY COMMISSION j 10 CFR Part 50 '

i Hodifications to General Design Criterion 4 '

Requirements For Protection Against Dynamic Effects of Postulated Pipe Rupture AGENCY: Nuclear Regulatory Comission.

ACTION: Proposed rule.

I

SUMMARY

The Nuclear Regulatory Comission is proposing to amend its regulations which require ,the postulation in the design basis of dynamic effects from loss of coolant accidents up to and including a break equivalent in size to the double-ended rupture of the largest pipe of the reactor coolant system. Proposed modifications would allow analyses to serve as a sufficient basis for excluding consideration of dynamic effects, and only dynamic effects, associated with specific pipe ruptures. The amendment will permit the selective removal of pipe. whip restraints and jet shields from operating plants, plants under construction and future plant designs, but will not impact current design requirements for ECCS performance, containment sizing nor environmental qualification of electrical and mechanical equipment.

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DATE: Comment period expires [60 days after publication]. Comments received after this date will be considered if it is practical to do so, but assurance of consideration cannot be given except as to coments received on or before this date.

1 ADDRESSES: Send comments to: Secretary, U.S. Nuclear Regulatory Comission, Washington, DC 20555, ATTN: Docketing and Service Branch.

Hand deliver coments to: Room 1121, 1717 H Street, NW, Washington, DC between 8:15am and 5:00pm weekdays.

Copies of the regulatory analysis, documents referenced in this notice and comments received may be examined at: the NRC Public Document Room at 1717 H Street, NW, Washington, DC.

FOR FURTHER INFORMATION CONTACT: John A. O'Brien, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Comission, Washington, DC i

20555, Telephone (301) 443-7860.

i SUPPLEMENTARY INFCRMATION:

I. Background ,

II. Limitation to Dynamic Effects III. Historical Documentation L IV. Findings and Conclusions V. Invitation to Coment VI. Finding of No Significant Impact VII. Paperwork Reduction Act Statement VIII. Regulatory Analysis IX. Regulatory Flexiblity Act Certification .

X. List of Subjects In 10 CFR Part 50

__ _ __ _ . 3 , _ - _ _ _ _ _ _ __ _ ._ _

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BACKGROUND l t

Recent investigations using both deterministic and probabilistic i methodologies have demonstrated that for the specific case of the primary f circuits of pressurized water reactors, a double-ended guillotine rupture j does not occur. Efforts are currently underway to learn if these findings can be extended to other high energy piping systems.

i In the context of the definition of " Loss of Coolant Accident", the f

requirements of General Design Criterion 4 have led to the placement of massive pipe whip restraints and jet shields near piping to mitigate the {

consequences of postulated pipe rupture accidents. Many experts believe that these accident mitigation features actually degrade overall reliability of piping because they reduce the effectiveness of inservice inspection, and because of difficulties and potential errors in installation, or reinstallation, which could actually increase the likelihood of pipe rupture. The past several years have witnessed the development of methods which allow a determination of the applicability of the leak-before-break concept to specific situations. This concept is fundamental in deciding whether or not piping ruptures.

In summary, the requirements of GDC 4 as applied in the context of the definition of LOCA have led to a situation where unnecessary design features have been added to nuclear power plants to forestall accidents which do not occur, and now indications are that these design features i i

reduce reliability and increase inspector radiation exposure. A need j exists to allow exclusion of certain pipe ruptures when supported by acceptable analyses.

4_.---._-----.

LIMITATION TO DYNAMIC EFFECTS i

The decision to treat only dynamic effects associated with pipe ruptures in this rulemaking and to leave stand present requirements for ECCS i performance, containment sizing and environmental qualification of mechanical and electrical equipment rests on two foundations. Firstly, breaches in the reactor coolant pressure boundary may occur other than through pipe rupture, as for example, in the steam generator or through the '

reactor coolant pump. These non-pipe rupture breaches impose design <

requirements on the ECCS, containment and components which cannot be avoided by investigating the integrity of piping. Secondly, studies completed to date indicate that negative effects from the postulation of pipe rupture result only from the consideration of the dynamic effects associated with pipe rupture. The negative effects relate primarily to the placement of pipe whip restraints and jet shields which, according to present views, degrades reliability, increases inservice inspection radiation dosages and adversely affects construction and maintenance economics. Thus, the only incentive is to deal with the dynamic effects associated with postulated pipe ruptures.

HISTORICAL DOCUMENTATION In a June 14, 1983 letter to the NRC Executive Director for Operations from J. J. Ray, Chairman of the ACRS, the following paragraphs appears:

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"The NRC has been a leader in supporting research to validate the f application of both elastic and elastic-plastic fracture mechanics to  !

nuclear systems and components. Over the last decade this has led to a sound basis for predicting the conditions under which cracks in the primary pressure boundary will be stable. In particular, this work has provided confidence in predicting the range of crack sizes that I will be stable and grow slowly. That is, crack sizes that will leak but not break.

We believe it is now appropriate and fitting to apply this to the analysis of Task Action Plan A-2 dealing with the treatment of Asymmetric Blowdown Loads on Reactor Primary Coolant Systems. The central question here is whether the crack grows slowly to sizes well beyond those which will give detectable leaks, or if a pipe containing i

a crack too small to produce a detectable leak will suddenly and catastrophically break, and impose substantial asymmetric blowdown loads. Here, the fracture mechanics analysis clearly indicates that in PWR primary piping a substantial range of stable crack sizes exists between those which given detectable leaks, and the much larger size that results in a sudden failure. That is, there is no known mechanism in PWR primary piping material for developing a large break without going through an extended period during which the crack would leak copiously."

Later, in " Minutes of CRGR Meeting Number 47" dated Octotar 14, 1983, it is stated that:

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"The CRGR observed that the staff findings concerning leak before ,

break have broad implications that go beyond resolution of the A-2 I

issue affecting 13 PWR licensees. These findings and the technical justifications in support of the findings could extend to other break locations and to assumptions previously made for piping loops and components of the reactor coolant systems, for piping connected to the l coolant system and perhaps to the piping of other systems in the plant. This broader applicability of the leak before break criteria could have potentially large positive benefits in terms of the degree to which unneeded and potentially counter-productive hardware (e.g.,

piping restraints, jet impingment barriers etc.) continues to be required in plant construction. In this regard, the CRGR was advised by staff that the leak before break criteria could be more broadly extended to apply to the large size piping and components in the PWR reactor coolant system. This would be considered by the staff in the next few months. In parallel with this effort, the staff is preparing a rule change to codify their findings and recomendations. To maximize the utility of the staff's recomendation and their potentially positive benefits to plants under construction, the CRGR ,

1 recommended a special staff effort to implement these recomendations i to the extent justifiable in terms of safety and staff resources."

Still later, in Generic Letter 84-04 dated February 1, 1984, the following statements are made:

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" Authorization by NRC to remove or not to install protection against asymmetric dynamic loads (e.g., certain pipe whip restraints) in the primary main coolant loop will require an exemption from General Design Criteria 4 (GDC-4). Licensees must justify such exemptions on a plant-by-plant basis. In such exemption requests, licensees should perform a safety balance in terms of accident risk avoidance attributable to protection from asymetric blowdown loads versus the safety gains resulting from a decision not to use such protection.

Provided such a balance shows a net safety gain for a particular facility, an exemption to GDC-4 may be granted to allow for removal of existing restraints or noninstallation of restraints which would have i

otherwise been required to accommodate double-ended break asymmetric dynamic loading in the primary coolant loop.

l Other PWR licensees or applicants may also request exemptions on the f'

same basis from the requirements of GDC-4 with respect to asymetric blowdown loads resulting from discrete breaks in the primary main coolant loop, if they can demonstrate the applicability of the modeling and conclusions contained in the referenced reports to their i

plants or can provide an equivalent fracture mechanics based demonstration of the integrity of the primary main coolant loop in their facilities." l In the June 29, 1984 memorandum from Harold Denton to Robert Minogue which {

l requested initiation of this rulemaking, the view is expressed that.

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"The granting of plant specific exemptions to the regulations on a i

system unique basis entails significant allocation of resources both by the NRC staff evaluating such requests for exemptions and by the industry performing appropriate analyses. In addition, OELD views are d that extensive use of exemptions to authorize the elimination of pipe whip restraints is inappropriate. Accordingly, we are requesting the Office of Nuclear Regulatory Research to initiate rulemaking to enable the use of advanced fracture mechanics technology to determine the appropriate dynamic effects to be considered for piping system failures. There is a need for rulemaking that could allow less than full double-ended pipe breaks to be postulated for design against consequent dynamic effects (e.g., pipe whip, jet impingement). This rulemaking should not affect any other design basis requirements based on a double-ended pipe break, such as ECCS or containment loadings. ,

One way to accommodate these requested changes would be to modify General Design Criterion 4 to separately define the environmental and 1

dynamic effects of postulated piping failures."

6 FINDINGS AND CONCLUSIONS i Alternatives to this rulemaking were evaluated using as a basic premise the hypothesis that the NRC staff, the ACRS and the CRGR have determined that  ;

the postulation of certain pipe ruptures may have a detrimental effect on public health and safety as well as having adversely affected construction and maintenance economics. This hypothesis is supported in part by

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l citations in the HISTORICAL DOCUMENTATION portion of this SUPPLEMENTARY J INFORMATION. Additionally, the nuclear industry has supported this same view as reflected by comments in Volume 3 of NUREG-1061, " Evaluation of Potential For Pipe Breaks" prepared by the USNRC Piping Review Comittee.

Given this widely expressed view, it is imperative that steps be taken to allow removal of design features from both plants in operation and under construction which produce these negative effects. General Design Criterion 4, however, would require these design features. Thus only two 4

potential courses of action are acceptable: exemptions to GDC 4 and rulemaking. The ELD has expressed the view that extensive use of exemptions to authorize the elimination of pipe whip restraints is i I

inappropriate. Nonetheless, now that the analytical methods are available l l for application and acceptance criteria for implementing the analytical methods are being developed by the NRC and industry groups, there will be

significant motivation to seek exemptions. It therefore appears most j rational to undertake rulemaking at this time.

The need and urgency for addressing the issue stems wholely from the widespread acceptance of the analysis results and the research findings

pertaining to pipe rupture coupled with increasing confidence in its applicability. Prior to the last few years, there was no sound technical basis for excluding certain pipe ruptures from the design basis. Now it is clear that it is possible to defend the exclusion of PWR primary loop double-ended guillotine pipe ruptures, and that the scope may be extended to other piping. Rulemaking action would promote investigations to learn which etner situations would also permit the removal of pipe whip T

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o restraints and jet shields. Acceptance criteria for generally applying these results pertaining to leak-before-break are being published by the NRC staff in NUREG-1061, Volume 3, and by the American Nuclear Society in ANS-58.2.

It is anticipated that this rulemaking action will reduce occupational radiation exposure by amounts measured in tens of thousands of man-rem and that cost savings will exceed $100 million.

INVITATION TO COMMENT Coments pertaining to the value-impacts associated with this modification to General Design Criterion 4 are invited, with particular reference to experience with the use of pipe whip restraints and jet shields near nuclear reactor piping. Additionally, remarks relating to the scope of piping which could or should be affected as well as justifications for these remarks are welcomed.

1 Finally, the decision to limit the impact of this modification of General Design Criterion 4 to only dynamic effects associated with pipe rupture also merits review and coment.

FINDING OF N0 SIGNIFICANT ENVIRONMENTAL IMPACT i

The Comission has determined under the National Environment Policy Act of 1969, as amended, and the Comission's regulations in Subpart A of 10 CFP.

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Part 51, that this rule, if adopted, would not be a major Federal action significantly affect the quality of the human environment and therefore an environmental impact statement is not required. Although the removal of I

certain plant hardware could result, this will not alter the environment I-impact of the licensed activities. It is anticipated that removed hardware would be stored at the plant site to be available for any potential future needs. The environmental assessment and finding of no significant impact on which this determination is based are available for inspection at the NRC Public Document Room, 1717 H Street, NW, Washington, DC.' Single copies of the environmental assessment and the finding of no significant impact are available from John A. O'Brien, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, Washington, DC 20555, Telephone (301)443-7860.

PAPERWORK REDUCTION ACT STATEMENT This proposed rule contains no information collection requirements and therefore is not subject to the Paperwork Reduction Act of 1980 (44 U.S.C.

3501 et seq.) p

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REGULATORY ANALYSIS I f

The Comission has prepared a draft regulatory analysis on this proposed regulation. The analysis examines the costs and benefits of the alternatives considered by the Comission. The draft analysis is available 1 I

for inspection in the NRC Public Document Room, 1717 H Street NW, l 9

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Washington, DC. Single copies of the analysis may be obtained from John A. I-0'Brien, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Comission, Washington, DC 20555, Telephone (301)443-7860.  ;

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i REGULATORY FLEXIBILITY ACT CERTIFICATION As required by the Regulatory Flexibility Act of 1980, (5 U.S.C. 605(b)),

the Comission certifies that this rule, if adopted, will not have a i significant economic impact on a substantial number of small entities. '

This rule affects only the licensing and operation of nuclear power plants.

The companies that own these plants do not fall within the scope fo the definitions of "small entities" set forth in the Regulatory Flexibility Act or the Small Business Size Standards set out in regulations issued by the Small Business Administration at 13 CFR Part 121.

LIST OF SUBJECTS IN 10 CFR PART 50 Antitrust, Classified information, Fire prevention, Incorporation by reference, Intergovernmental relations, Nuclear power plants and reactors, Penalty, Radiation protection, Reactor siting criteria, Reporting and recordkeeping requirements.

f Under the authority of the Atomic Energy Act of 1954, as amended, the Energy Reorganization Act of 1974, as amended, and 5 U.S.C. 553, the NRC is proposing to adopt the following ameadments to 10 CFR 50. I

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PART 50 - DOMESTIC LICENSING OF PRODUCTION AND UTILIZATION FACILITIES  !

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1. The authority citation for Part 50 continues to read as follows:

3 AUTHORITY: Secs. 103, 104, 161, 182, 183, 186, 189, 68 Stat. 936, 937, '

948, 953, 954, 955, 956, as amended, sec. 234, 83 Stat. 1244, as amended (42 U.S.C. 2133, 2134, 2201, 2232, 2233, 2236, 2239, 2282): secs. 201, 202, 206, 88 Stat. 1242, 1244, 1246, as amended (42 U.S.C. 5841, 5842, 5846), unless otherwise noted. '

Section 50.7 also issued under Pub. L.95-601, sec.10, 92 Stat. 2951 (42 U.S.C. 5851). Sections 50.57(d), 50.58, 50.91, and 50.92 also issued under ,

Pub. L.97-415, 96 Stat. 2071, 2073 (42 U.S.C. 2133, 2239). Section 50.78 also issued under sec. 122, 68 Stat. 939 (42 U.S.C. 2152). Sections 50.80-5081 also issued under sec. 184, 68 Stat. 954, as amended (42 U.S.C.

i 2234), Sections 50.100 - 50.102 also issued under sec. 186, 68 Stat. 955 (42 U.S.C. 2236).

For the purposes of sec. 223, 68 Stat. 958, as amended (42 U.S.C. 2273),

550.10(a), (b), and (c), 50.44, 50.46, 50.48, 50.54, and 50.80(a) are issued under sec. 161b, 68 Stat. 948, as amended (42 U.S.C. 2201(b));

$%50.10(b) and (c) and 50.54 are issued under sec. 1611, 68 Stat. 949, as amended (42 U.S.C. 2201(i); and 50.55(e), 50.59(b), 50.70, 50.71, 50.72, 50.73, and 50.78 are issued under sec.1610, 68 Stat. 950, as amended (42 U.S.C. 2201(o)).

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2. In Appendix A, General Design Criteriaon 4 is revised to read as follows: l APPENDIX A - GENERAL DESIGN CRITERIA FOR NUCLEAR POWER PLANTS CRITERIA l I Overall Requirements Criterion 4 - Environmental and missile design bases. Structures, systems ,

and components important to safety shall be designed to accommodate the effects of and to be compatible with the environmental conditions associated with normal operation, maintenance, testing and postulated accidents, including loss-of-coolant accidents. These structures, systems and components shall be appropriately protected against dynamic effects, including the effects of missiles, pipe whipping and discharging fluids, that may result from equipment failures and from events and conditions outside the nuclear power unit. However, dynamic effects associated with loss-of-coolant accidents may be excluded from the design basis when analyses demonstrate that fluid system piping will not rupture using conditions consistent with the design basis for the piping.

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5 Dated at Washington, DC this day of 1984.

For the Nuclear Regulatory Comission.

Samuel J. Chilk Secretary of the Comission, l

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i Preliminary Draft Regulatory Analysis Task

Title:

Modifications to GDC 4 Requirements for Protection Against Postulated Pipe Ruptures l h

1. Statement of Issue

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Recent investigations using both deterministic and probabilistic i fracture mechanics methodologies have demonstrated that for the i specific case of the primary circuits of pressurized water reactors, i a double-ended guillotine rupture does not occur. Efforts are 1 currently underway to learn if these findings can be extended to 1 other high energy piping systems.

In the context of the definition of " Loss of Coolant Accident", the

requirements of General Design Criterion 4 have led to the placement of massive pipe whip restraints and jet shields near piping .to

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i mitigate the consequences of postulated pipe rupture accidents. Many

experts believe that these accident mitigation features actually j degrade overall reliability of piping because they reduce the j effectiveness of inservice inspection, and because of difficulties i and potential errors in installation, or reinstallation, which could actually increase the likelihood of pipe rupture. When the General .

Design Crtieria were promulgated, there were no conclusive methods to demonstrate that certain pipes could not rupture. The past several years have witnessed the development of advanced fracture mechanics technology. These advanced fracture mechanics techniques deal with relatively small flaws in piping components (either postulated or real) and examine their behavior under various pipe loads. The objective of efforts which utilize these methods has been to demonstrate that the detection of small flaws by either inservice 1

inspection or leakage monitoring systems is assured long before the flaws can grow to critical or unstable sizes which could lead to large break areas such as the double ended guillotine break (DEGB) or its equivalent. The concept underlying such analyses is referred to j as " leak-before-break" (LBB).

! In summary, the issue is that requirements of GDC 4 as applied in the i context of the definition of LOCA led to a situation where i unnecessary design features have been added to nuclear power plants i to forestall accidents which do not occur, and now indications are that these design features reduce reliability and increase inspector i) radiation exposure. A need exists to allow exclusion of certain pipe

! ruptures when supported by acceptable analyses. It is emphasized that not all pipe whip restraints and jet shields will be eliminated i as a result of this rulemaking; the scope of affected piping has not been determined. However, at tne very least, primary system piping of PWRs will be affected.

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2. The Need and Urgency for Addressing the Issue i

The need and urgency for addressing the issue stems wholely from the widespread acceptance of the analysis results and the research findings pertaining to pipe rupture coupled with increasing ,

confidence in its applicability. Prior to the last few years, there was no sound technical basis for excluding certain pipe ruptures from the design basis. Now it is clear that it is possible to defend the exclusion of PWR primary loop double-ended guillotine pipe ruptures, and that the scope may be extended to other piping. These analytical  ;

results have been applied to the resolution of Unresolved Safety Issue A-2 already. Acceptance criteria for applying these results pertaining to leak-before-break generally are being published by the NRC staff in NUREG-1061, Volume 3. and by the American Nuclear Society in ANS-58.2. The new knowledge that certain piping does not rupture mandates the removal of pipe whip restraints and jet shields both from the point of safety and economics. Rulemaking action would, in addition, promote investigations to learn which other i situations would also permit the removal of pipe whip restraints and jet shields.

3. Alternatives to Rulemaking Studies performed by Lawrence Livermore National Laboratory under contract to the Office of Nuclear Regulatory Research have shown that the presence of pipe whip restraints near piping can increase pipe rupture probabilities by a factor of ten and pipe leak probabilities by a factor of one hundred.

Given that the NRC staff, the ACRS, the CRGR and the nuclear industry have determined that the postulation of certain pipe rutpures may have a detrimental effect on public health and safety as well as having adversely affected construction and maintenance economics, it is imperative that steps be taken to allow removal of design features from both plants in operation and under construction which produce these negative effects. General Design Criterion 4, however, would require these design features. Thus only two potential courses of action are acceptable: exemptions to GDC 4 and rulemaking. The ELD has expressed the view that extensive use of exemptions to authorize the elimination of pipe whip restraints is inappropriate.

Nonetheless, now that the analytical methods are available for j application and acceptance criteria for implementing the analytical methods are being developed by the NRC and industry groups, there will be significant motivation to seek exemptions. It therefore appears most rational to undertake rulemaking at this time.

4. Addressing the Issue Through Rulemaking The issue will be addressed by a modification to General Design Criterion 4. The candidate modification is given below, where the underlined portion indicates the added text:

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(added text underlined, none of the old text is deleted) )

Criterion 4 - Environmental and missile design bases. Structures, systems and components important to safety shall be designed to accommodate the effects of and to be compatible with the environmental conditions associated with normal operation, maintenance, testing and postulated accidents, including loss-of-coolant accidents. These structures, systems and components shall be appropriately protected against dynamic effects, including the effects of missiles, pipe whipping and discharging fluids, that may result from equipment failures and from events and conditions outside the nuclear power unit. Dynamic effects associated with loss-of-coolant accidents may be excluded from the design basis when fracture mechanics analyses demonstrale that postulated leakage size flaws in fluid system piping will not propagate unstably. Postulated fluid system piping flaw sizes, locations, orientations, and their propagation shall be established consistent with the design basis for the piping.

5. Benefits and Costs The staff has stated in NUREG-1061, Volume 3 that:

"The LPipe Break] Task Group is aware that the NRC is initiating rulemaking to preclude the need to issue exemptions by permitting the use of advanced fracture mechanics as an alternate approach to requiring the postulation of pipe ruptures. The Task Group supports this initiative and strongly reconrnends that rulemaking be pursued expeditiously. The basis for this recommendation, as supported elsewhere in the value-impact and other sections of this report, is that a net safety as well as economic gain accrue from the elimination of massive protection devices in nuclear power facilities, particularly those intended to prevent whipping of ruptured pipes."

Elsewhere in the same document the staff writes:

"Any detailed value-impact assessment of changes in pipe break criteria requires knowledge beforehand of the specific changes themselves. Nevertholess, a review of assessments already completed for specific pipe break issues implies the following general conclusions for elimination of the double-ended-guillotine break (DEGB) as a design basis for PWR l reactor coolant loop piping: )

(a) Elimination of pipe whip restraints would only negligibly increase public and occupational radiation exposure (0!!E) resulting from pipe break accidents.

(b) Elimination of pipe whip restraints would improve access to pipe welds for inservice inspections, and thereby significantly reduce ORE during inspection. Improved access would also reduce ORE during normal plant maintenance, although to a lesser degree. This benefit would apply both to operating plants and to plants under c,onstruction.

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l (c) For operating plants not already having pipe whip i

restraints, eliminating the -DEGB -- and thus the need to ,

install restraints -- would reduce ORE during installation. I For the sixteen A-2 plants, installation and maintenance of I these restraints would avoid the occurrence of ORE by about a 11,000 man-rem compared to a small increase in iublic risk and accident avoided occupational exposure of Less than 5 man-rem." i

, Regarding item (a) and (c) above, recent research results from i

Lawrence Livermore National Laboratory not available to the Pipe Break Task Group have indicated that elimination of pipe whip restraints may actually produce a small decrease in public and occupational radiation when the prospect of improper installation of pipe whip restraints is considered. Improper installation of pipe whip restraints may increase pipe leak and rupture probabilities.

The industry perspective on value-impacts regarding the use of the leak-before-break hypothesis is reflected by the Atomic Industrial Forum and the Bechtel Power Corporation coments in ' NUREG-1061, Volume 3. According to the Atomic Industrial Forum, costs associated with pipe whip restraints are as follows:

o Design, procurement and construction costs related to pipe rupture hardware is from $20M to $40M per unit.

o Number of pipe whip restraints in a " typical" light water a reactor is from 250 to 400 per plant, i

o Installation times, including design, etc., is from 150,000 to 250,000 man-hours.

l The preceding figures will vary from plant to plant, depending on its l status, whether being designed, in early sta j

approaching a near-term operating license (NT0L)ges , or operating. of construction, Bechtel Power Corporation figures are similar as indicated below: .

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, o Design analyses, materials and construction is $100,000 per 4

restraint.

o Number of restraints on a typical plant is 300.

o Overall costs per nuclear unit is from $30M to $50M. ,

o Manpower per typical plant for overall installation of restraints is 250,000 man-hours per 500-600 MWe LWR.

Relevant excerpts from the Atomic Industrial Forum Discussion of

'ialue Impacts regarding application of the leak-before-break concept follow:

"Value-impacts reported by industry to date identify significant cost savings and operational radiation exposure (ORE) reductions that can be realized based on NRC approval of pipe ruptures

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postulated at specific locations and subsequent elimination of h the associated pipe ruptures mitigation hardware, i.e. , pipe h whip restraints and jet barriers. f Experience has shown that it is very difficult to assess an exact value impact. No standard value-impact methodology has  ;

i been used due to the many variables involved in computing cost savings and ORE reductions. However, it is industry's belief thet the magnitude of cost savings and ORE reductions are so compelling and beneficial that there is no need to rigorously quantify it." f

' "Where utilities have made specific requests, cost savings on the order of several million dollars and ORE reductions of several hundred man-rem are reported possible. The difference between the AIF and utility estimates is due to the fact that the AIF estimate is based on the total cost of all required pipe rupture hardware while the utility estimates are based on cost }

t savings on eliminating hardware associated with a limited scope [

NRC request."

"Value impact estimates can vary considerably from plant to plant due to fundamental differences in design. For instance, value impact estimates for a Combustion Engineering plant and a Westinghouse plant with similar megawatt ratings can be expected to be different due to design variances. Likewise, value impact differences can be expected among plants with the same NSSS vendor, e.g., 2, 3, and 4-loop Westinghouse plants. In addition, depending upon which lead A/E is contracted for the plant, design differences lead to different value impacts.

i r'or A/Es, the major difference is layout. Further differences i can originate as a result of design decisions made by the  !

utility."

"Pla t status variables are important when considering value imp 6ct estimates. For example, a value impact estimate for an

NT0L would include proportionately large contributions due to engineering and construction cost savings. A value impact estimate for an operating plant would include proportionately large contributions for removals costs and penalties for radiation exposure incurred during the removal."

More specific value-impact information is attached as Enclosures A, B, C and D to this preliminary draft regulatory analysis. A summary and comentary of the contents of these enclosures follows.

Enclosure A This value-impact analysis dated April 23, 1984 and submitted by Texas Utilities Generating Company deals with the elimination of large primary loop pipe rutpures at Comanche Peak, Units 1 & 2. It concludes that occupational radiation exposure would be reduced by 155 man-rem and cost savings of $2.7 million would be realized if only jet shields were not i

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I installed. No consideration is given to pipe whip restraints, except for l restraint shim costs. Additionaly, twenty-five weeks of replacement power costs due to fuel load delay would be saved. These figures are the total i for both units.

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Enclosure B f

Entitled " Safety Balance for the Elimination of Reactor Coolant System Main Loop Pipe Break Protective Devices" and dated March 23, 1984, this document deals with Units 1 & 2 of the Vogtle Electric Generating Plant owned by Georgia Power Company. Unlike Enclosure A, only man-rem savings associated with not installing pipe whip restraints are analyzed. No cost  !

savings are investigated, but the nominal estimates of occupational radiation exposure is 727 man-rem for both units with a range of 69 to 2797 man-rem.

Enclosure C Dated Septmeber 14, 1984, and prepared for Catawba Unit 2 owned by Duke Power Company, this enclosure contains a summary of estimated cost savings and operational benefits for elimination of primary loop pipe breaks.

Results indicate a reduction of 600 man-rem and a cost savings of $1.3 million.

Enclosure D Relating to South Texas Project, Units 1 and 2, owned by Houston Lighting and Power Company and dated April 5, 1984, this document, like Enclosure B, treats only man-rem savings associated with not installing pipe whip restraints. No cost savings are investigated, but the nominal estimate of occupational radiation exposure is 171 man-rem for both units with a range of 20 to 656 man-rem.

It is anticipated that similar results will be applicable to the reactor coolant loops of all PWRs and some BWRs indicating total reductions in occupational radiation exposure of the order of 10,000 man-rem and cost savings of $100 million. Moreover, since these estimates may be found to be applicable to piping other than the reactor coolant loop, substantial increments in these value impacts may result.

6. NRC Resources and Scheduling Two staff years is estimated to undertake this rulemaking. The notice of proposed rulemaking should appear in the Federal Register in July 1985.

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NUCLEAR REGULATORY COMMISSION wasumom.o.c.nosas IWORIW TOM N,*****/

October 29, 1984 j

MEMORANDUM FOR: Richard H. Vollmer Co-Chairman .

NRC Piping Review Comittee t Lawrence Shao, Co-Chairman i NRC Piping Review Consnittee .

FROM: William J. Olmstead h j

Director and Chief Counsel, Regulations Division ij Office of the Executive Legal Director

SUBJECT:

FINAL DRAFT REPORT OF PIPING REVIEW CONtITTEE On pages 4-1 and 4-2 of the referenced report, and again at page 11-2, the Cossnittee recommends continued use of GDC-4 exemptions "in parallel" with the GDC-4 rulemaking effort. On other occasions this office has stated its legal position that use of GDC-4 exemptions in this way is accompanied by considerable legal risk, in that it amounts to amendment of a fundamental NRC rule in the absence of rulemaking procedures. This risk increases as the use of such exemptions broadens.

We will continue to review closely the use of GDC-4 exemptions to implement LBB technology. Reliance on exemptions should not be allowed to delay or draw resources from the rulemaking effort. The most rapid and legally sound method of carrying out the Connittee's proposed coursa of action is to devote 3 I

maximum resources to the development of a sound technical basis for the amendment of GDC-4, and related provisions as necessary. This effort must  !

k include a basis for not extending LBB methodology to the LOCA definition, ECCS criteria, etc. Tsent this fully-developed technical record, the agency proceeds at considerable legal risk in allowing broadened use of this concept, which is at odds with previous regulatory assumptions.

William J. Olmstead Director and Chief Counsel Regulations Division Office of the Executive Legal Director

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