ML20154S561

Reg Guide 01.178, Approach for Plant-Specific Risk-Informed Decisionmaking Inservice Insp of Piping

ML20154S561
Person / Time
Issue date:	09/30/1998
From:	NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
To:
References
TASK-*****, TASK-RE REGGD-01.178, REGGD-1.178, NUDOCS 9810280016
Download: ML20154S561 (24)

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U.S. NUCLEAR REGULATORY COMMISSION s:pt:mber 1998 O(g[paug\\

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REGULATORY GUIDE

• • • ++

OFFICE OF NUCLEAR REGULATORY RESEARCH FOR TRIAL USE REGULATORY GUIDE 1.178 (Draft was issued as DG-1063)

AN APPROACH FOR PLANT-SPECIFIC RISK-INFORMED DECISIONMAKING INSERVICE INSPECTION OF PIPING A. INTRODUCTION tion of plant piping using risk insights. The Electric Power Research Institute (EPRI) published its "PSA During the last several years, both the U.S. Nuclear Applications Guide"(Ref.14) to provid utilities with Regulatory Commission (NRC) and the nuclear indus-try have recognized that probabilistic risk assessment guidance on the use of PRA information for both regu-latory and nonregulatory applications. The Nuclear En-(PRA) has evolved to be more useful in supplementing traditional engineering approaches m reactor regula-ergy Institute (NEI) has been developing guidelines on risk-based ISI and submitted two methods, one devel-tion. After the publication ofits policy statement (Ref,

1) on the use of PRA in nuclear regulatory activities, the oped by EPRI (Ref.15) and the other developed by the Commissica directed the NRC staff to develop a regu-ASME research and the Westinghouse Owners Group g

latory fra*nework that incorporated risk insights. That (Refs.16-17), for staff review and approval.

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framework was articulated in a November 27,1995, pa-per to the Commission (Ref. 2). This regulatory guide, Given the recent initiatives by the ASME in devel-A oping Code Cases N-560, N-577, and N-578, it is an-which addresses inservice inspection of piping (ISI),

with its companion Standard Review Plan, Section ticipated that licensees will request changes to their 3.9.8 of NUREG-0800 (Ref. 3), and other regulatory plant's design, operation, or other activities that require documents (Refs. 4-10), implement, in part, the Com-NRC approval to incorporate risk insights into their ISI mission's policy statement and the staff's framework programs (known as risk-informed inservice inspec-for incorporating risk insights into the regulation of nu-tion programs, RI-ISI). Until the RI-ISI is approved clear power plants.

for generic use, the staff anticipates that licensees will request changes to their ISI programs by requesting In 1995 and 1996, the industry developed a number NRC approval of alternative inspection programs that (

of documents addressing the increased use of PRA in meet the criteria of 10 CFR 50.55a(a)(3)(i) in Section j

nuclear plant regulation. The American Society of Me-50.55a, " Codes and Standards," of 10 CFR Part 50, chanical Engineers (ASME) initiated Code Cases

" Domestic Licensing of Product:an and Utilization Fa-N-560 (Ref.11), N-577 (Ref.12), and N-578 (Ref.13) cilities," providing an acceptable level of quality and that address the importance categorization and inspec-safety. As always, licensees should identify how the USNRC REGUIATORY GUIDES Tn. guid

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chosen approach, methods, data, and criteria are ap-tory decisionmaking. In August 1995, the NRC adopted a policy statement regarding the expanded use propriate for the decisions they need to make.

f PRA (Ref.1). In part, the policy statement states In October 1997,the Commission published a draft that:

of this regulatory guide for public comment. This The use of PRA technology should be in-guide's principal focus is on the use of PRA findings creased in all regulatory matters to the ex-and risk insights in support of proposed changes to a tent supported by the state-of-the-art in plant's design, operations, and other activities that re.

PRA methods and data and in a manner that quire NRC approval % h changes include (but are not complements the deterministic approach limited to) license amendments under 10 CFR 50.90, and supports the NRC's traditional philoso-7 requests for the use of alternatives under 10 CFR phy of defense-in-depth.

50.55a, and exemptions under 10 CFR 50.12. This reg.

PRA and associated analyses (e.g., sensi-ulatory guide describes methods acceptable to the NRC tivity studies, uncertainty analyses, and im-staff for integrating insights from PRA techniques with l

traditional engineering analyses into ISI programs for -

portance measures) should be used in regu-latory matters, where practical within the piping.

bounds of the state-of-the-art,to reduce un-The draft guide, DG-1063, was discussed during a necessary conservatism associated with public workshop held on November 20-21,1997, and current regulatory requirements, regulatory was peer reviewed. While the public comments and guides, license commitments, and staff peer review of the document were positive, the staff has practices. Where appropriate, PRA should not had an opportunity to apply the guidance to indus-be used to support the proposal of addi-try's pilot plants.Therefore, this regulatory guide is be-twnal rpatory requirements in accor-ing issued for trial use on the pilot plants. This regula-dance with 10 CFR 50.109 (Backfit Rule).

tory guide does not establish any final staff pos.tions, Appropriate procedures for m.cluding PRA i

and may be revised.m response to experience with its gg

, fg use. As such, this trial regulatory guide does not estab' quirements should be developed and fol-lish a staff position for purposes of the Backfit Rule,10 lowed. It is, of course, understood that the CFR 50.109, and any changes to this regulatory guide intent of this policy is that existing rules and prior to staff adoption m final form will not be consid-regulations shall be complied with unless cred to be backfits as defined in 10 CFR 50.109(a)(1).

these rules and regulations are revised.

This will ensure that the lessons learned frota regulato-PRA evaluations in support of regulatory ry review of the pilot plants are adequately addressed in decisions should be as realistic as practica-this document and that the guidance is sufficient to en.

ble and appropriate supporting data should hance regulatory stability in the review, approval, and be publicly available for review.

implementation of proposed RI-ISI programs.

The Commission's safety goals for nuclear In the interest of optimizing limited resources, the p wer plants and subsidiary numerical ob-appendices that were in DG-1063 will be incorporated jectives are to be used with appropriate con-in a future NUREG report. The appendices have been sideration of uncena.nties m making reg;u-delded from this guide to focus the NRC staff's limited latory judgments on tt med for proposmg resources on the review and approval of the pilot plant and b ekfitting new genei c requirements l

applications and the topical reports submitted in sup-n nucl ar p wer plant licensees.

port of the pilot plant analyses. Staff positions on the in its approval of the policy statement, the Com-methodologies will be provided in the staff's safety mission articulated its expectation that implementation evalu on of the topical reports and pilot plant submit-of the policy statementwillimprovethe regulatory pro-tals.hs ;)tocess would minimize resources needed to cess in three areas: foremost, through safety decision-update the RG to address the different methods pro-making enhanced by the use of PRA insights; through posed by the industry, more efficient use of agency resources; and through a a

reduction in unnecessary burdens on licensees.

Background

During recent years, both the NRC and the nuclear In parallel with the publication of the policy state-industry have recognized that PRA has evolved to the ment, the staff developed a regulatory framework that point that it can be used increasingly as a tool in regula-incorporates risk insights. That framework was anticu-1.178 - 2

lated in a November 27,1995, paper (SECY-95-280)

As a result of the above insights, more efficient and to the Commission. This regulatory guide, which ad-technically sound means for selecting and scheduling f} dresses ISI programs of piping at nuclear power plants, ISIS of piping are under development by the ASME Q is part of the implementation of the Commission's (Refs.11-13).

policy statement and the staff's tramework forincorpo.

ratmg risk insights into the regulation of nuclear power When categorizing piping segments in terms of plants. This document uses the knowledge base docu-their contribution to risk,it is the responsibility of a li-mented in Revision 1 of NUREG/CR-6181 (Ref.18),

censee to ensure that the categorization of piping seg-and it reflects the experience gained from the ASME ments and the resulting inspection programs are consis-initiatives (Code Case development and pilot plant ac-tent with the key principles and risk guidelines (e.g.,

tivities).

core damage frequency (CDF) and large early release frequency (LERF)) addressed in Regulatory Guide While the conventional regulatory framework, 1.174 (Ref. 4). This regulatory guide augments the based on traditional engineering criteria, continues t guidance presented in Regulatory Guide 1.174 by pro-sesve its purpose in ensuring the protection of pubhc viding guidance specific to incorporating risk insights health and safety, the current information base contains to i service inspection programs of piping.

insights gained from over 2000 reactor-years of plant Purpose of the Guide operating experience and extensive research in th areas of matenal sciences, aging phenomena, and in-Consistent with Regulatory Guide 1.174 (Ref. 4),

spection techniques. This information, combmed with this regulatory guide focuses on the use of PRA in sup-modern risk assessment techniques and associated port of a risk informed ISI program. This guide pro-data, can be used to develop a more effective approach vides guidance on acceptable approaches to meeting to ISI programs for piping.

the existing Section XI requirements for the scope and frequency ofinspection of ISI programs. Its use by li-The current ISI requirements for piping compo-censees is voluntary. Its principal focus is the use of A nents are found in 10 CFR 50.55a and the General De-gs and nd msips k dedsbns on n

sign Criteria listed in Appendix A to 10 CFR Part 50.

changes proposed to a plant's inspection program for These requirements are throughout the General Design piping. The current ISI programs are performed in com-

"" *ith the requirements of 10 CFR 50.55a and E.'th Section XI of the ASME Boiler and Pressur Criteria, such as in Criterion I, "Overall Require-wi ments,,, Criterion II,, Protection by Multiple Fa..

ssmn Product Barriers," Criterion III," Protection and Reac-sege, wM are part o% planfs huskg basis.

tivity Control Systems," and Criterion IV, " Fluid Sys-This approach provides an acceptable level of quality tems',,

and safety (per 10 CFR 50.55a(a)(3)(i)) by incorporat-ing insights from probabilistic risk and traditional anal-Section XI of the American Society of Mechanical ysis calculations, supplemented with operating reactor Engineers (ASME) Boiler and Pressure Vessel Code data. Licensees who propose to apply risk-informed ISI (BPVC) (Ref.19) is referenced by 10 CFR 50.55a, pr gr ms would amend their final safety analysis re-which addresses the codes and standards for design, p rt (FSAR, Sections 5.3.4 and 6.6) accordingly. A fabrication, testing, and inspection of piping systems.

S tandard Review Plan (S R P) (Ref. 3) has been prepared The objective of the ISI program is to identify service-f r use by the NRC staffin reviewing RI-ISI applica-tions.

induced degradation that might lead to pipe leaks and ruptures, thereby meeting, in part, the requirements set This document addresses risked-informed meth-in the General Design Criteria and 10 CFR 50.55a. ISI ods to develop, monitor, and update more efficient ISI programs are intended to address all piping locations programs for piping at a nuclear power facility. This that are subject to degradation. Incorporating risk in-guidance does not preclude other approaches for incor-sights into the programs can focus inspections on the porating risk insights into the ISI programs. Licensees more important locations and reduce personnel expo-may propose other approaches for NRC consideration.

I sure, while at the same time maintaining or improving It is intended that the methods presented in this guide be public health and safety. The justification for any re-regarded as examples of acceptable practices; licensees duction in the number ofinspections should address the

) issue that an increase in leakage frequency or a loss of should have some flexibility in satisfying the regula-tions on the basis of their accumulated plant experience defense in depth should not result from decreases in the and knowledge. This document addresses risk-numbers of inspections.

informed approaches that are consistent with the basic 1.178 - 3

All Class 1,2, and 31 piping within the current elements identified in Regulatory Guide l.174 (Ref. 4).

in addition, this document provides guidance on the ASME Section XI programs, and following for the purposes of RI-ISI.

All piping whose failure would compromise Safety-related structures, systems, or compo-Estimating the probability of a leak, a leak that pre-vents the system from performing its function (dis-nents that are relied upon to remain functional abling leak), and a rupture for piping segments, during and following design basis events to en-sure the integrity of the reactor coolant pres-Identifying the structural elements for which ISI sure boundary, the capability to shut down the can be modified (reduced or mereased), based on reactor and maintain it in a safe shutdown con-factors such as risk insights, defense in depth, re-dition, or the capability to prevent or mitigate duction of unnecessary radiation exposure to per-the consequences of accidents that could result

sonnel, in potential offsite exposure comparable to 10 CFR Part 100 guidelines.

7 Determining the risk impact of changes to ISI pro-Non-safety relatedstructures,systemsorcom-

grams, ponents 1

Capturing deterministic considerations in the re-That are relied upon to mitigate accidents vised ISI program, and or transients or are used in plant emergen-Developing an inspection program that monitors cy operating procedures; or the performance of the piping elements for consis-Whose failure could prevent safety-related tency wl") the conclusions from the risk assess-structures, systems, or components from ment.

fulfilling their safety-related function; or

]

Whose failure could cause a reactor scram Given the recent initiatives by the ASME in devel-or actuation of a safety-related system.

oping Code Cases N-560, N-577, and N-578 (Refs.

For both the partial and full scope evaluations, the 11-13), it is anticipated that licensees will request licensee is to demonstrate comphance with the accep-changes to their plant's design, operation, or other ac-tance guidelines and key principles of Regulatory tivities that require NRC approval to incorporate risk Guide 1.174 (Ref. 4).

insights in their ISI programs (RI-ISI). Until the RI-ISI is approved for generic use, the staff anticipates that li-The inspection locations of concern include all censees will request changes to their ISI programs by weld and base metal locations at which degradation requesting NRC approval of a proposed inspection pro-may occur, although pipe welds are the usual point of gram that meets the criteria of 10 CFR 50.55a(a)(3)(i),

interest in the inspection program. Within this regula-providing an acceptable level of quality and safety. The tory guide, references to " welds" are intended in a licensee's RI-ISI program will be enforceable under 10 broad sense to address inspections of critical structural locations in general, including the base metal as well as CFR 50.55a.

weld metal. Inspections will often focus on welds be-cause detailed evaluations will often identify welds as Scope of the RI-ISI Program the locations most likely to experience degradation.

This regulatory guide only addresses changes t Welds are most likely to have fabrication defects, welds the ISI programs for inspection of piping. To adequate-are often at locations of high stress, and certain de-ly reflect the risk implications of piping failure, both gradation mechanisms (stress corrosion cracking) usu-partial and full-scope RI-ISI programs are acceptable ally occur at welds. Nevertheless, there are other degra-to the NRC staff.

dation mechanisms such as flow-assisted-corrosion (e.g., erosion-corrosion) rnd thermal fatigue that occur Partial Scope: Alicensee may elect to limit its RI-independent of wehls.

ISI program to a subset of piping classes, for example, I

ASME Class-1 piping only, including piping exempt 1 Generally, ASME Code Class 1 includes all reactor pressure bound.

from the current requirements.

ary (RCPB) components. AsME Code Class 2 generally includes sys-tems or portions of systems important to safety that are designed for l Full Scope: A full scope RI-ISI program evaluates post accident containment and removal of heat and fission products.

ASME Code Class 3 generally includes those system components or the P P n8 n a Iilant as bein8 either hi h or low safet portions of systems important to safety that are designed to provide ii i

8 Significant. A full scope RI-ISI includes:

coolingwater and auxiliary feedwater for the front-une systems.

1.178 - 4

PRA scope-internal and external event initiators, l

To ensure that the proposed RI-ISI program would at-power and shutdown modes of operation, con-provide an acceptable level of quality and safety, the li-sideration of requirements for Level 1,2, and 32 l,) censee should use the PRA to identify the appropriate

analyses, V

scope of the piping segments to be included in the pro-gram. In addition, licensees implementing the risk-in-Risk metrics-core damage frequency,large early formed process may identify piping segments catego-release frequency and importance measures, rized as high safety-significant (llSS) that are not Sensitivity and uncertainty analyses.

currently subject to the traditional Code requirements To the extent that a licensee elects to use PRA as an (c.;., outside the Code boundaries, including Code ex-element to enhance or modify its implementation of ac-empt piping) or are not being inspected to a level that is tivities affecting the safety-related functions of SSCs commensurate with their risk significance. In this con-subject to the provisions of Appendix B to 10 CFR text,llSS refers to a piping segment that has a relatively Part 50, the pertinent requirements of Appendix B are high contribution to risk. PRA systematically takes applicable.

credit for systems with non-Code piping that provide support, act as alternatives, and act as backups to those The information collections contained in this doc-systems with piping that are within the scope of the cur-ument are covered by the requirements of 10 CFR rent Section XI of the Code.

Part 50, which were approved by the Office of Manage-ment and Budget (OMB), approval number Organization and Content 3150-0011. The NRC may not conduct or sponsor, and a person is not required to respond to, a collection ofin-This regulatory guide is structured to follow the formation unless it displays a currently valid OMB con-general four-element process for risk-informed ap-trol number.

plications discussed in Regulatory Guide 1.174 (Ref.

4). The Discussion section summarizes the four-Abbreviations and Definitions element process developed by the staff to evaluate pro-ASME American Society of Mechanical Engi-O posed changes related to the development of a RI-ISI neers

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program. Regulatory Position 1 discusses an accept.

BPVC Boiler and Pressure Vessel Code able approach for defining the proposed changes to an CCDF Conditional core damage frequency ISI program. Regulatory Position 2 addresses, in gen-CCF Common cause failure eral, the traditional and probabilistic engineering eval-CDF Core damage frequency uations performed to support RI-ISI programs and pre-CLERF sents the risk acceptance goals for determining the Conditional large early release frequency acceptability of the proposed change. Regulatory Posi-Expert tion 3 presents one acceptable approach forimplement.

Elicitation In the context of this regulatory guide, ing and monitoring corrective actions for RI-ISI pro-expert elicitation is a process used to esti-grams. The documentation the NRC will need to render e dat a d pute c es re its safety decision is discussed in Regulatory Position 4.

available for the intended purpose. It is a process used to estimate the failure proba-bility and the associated uncertainties of Relationship to Other Guidance Documents the material in question under specified As stated above, this regulatory guide discusses ac-degradation mechanisms. For example, if ceptable approaches to incorporate risk insights into an a structural mecha ucs cod: is not quah-ISI program and directs the reader to Regulatory Guide fled to calculate the failure probability of 1.174 and SRP Chapters 19 and 3.9.8 for additional E ".stic piping and no data are avaHaNe to guidance, as appropriate. Regulatory Guide 1.174 de-estimate its failure probability, experts m scribes a general approach to risk-informed regulatory plastic piping and their failure may be I

decisionmaking and discusses specific topics common asked to estimate the failure probabilities.

to all risk-informed regulatory applications. Topics ad-if applicable industry data are available,

} dressed include:

an expert elicitation process would not be needed.

PRA quality-data, assumptions, methods, peer 2

review, Level 1-accident sequence analysis. Level 2-accident progression and source term analysis, and Level 3-offsite consequence analysis.

1.178 - 5

RI-ISI Risk-informed inservice inspection Expert Panel Normally refers to plant personnel exper-Staff Refers to NRC employees ienced in operations, maintenance, PRA, Sensitivity ISI programs, and other related activities Studies Varying parameters to assess impact due and disciplines that impact the decision to uncertainties under consideration, SRP Standard Review Plan FSAR Final Safety Analysis Report SRRA Structural reliability / risk assessment (re-HSS High safety significance fers to fracture mechanics analysis)

IGSCC Intergranular stress corrosion cracking SSCs Structures, systems and components i

importance Tech Spec Technical specifications f

Measures Used in PRA to rank systems or compo.

nents in terms of risk significance I

B. DISCUSSION ISI Inservice inspection IST Inservice testing When a licensee elects to incorporate risk insights LERF Large early release frequency into its ISI programs, it is anticipated that the licensee LSS Low safety significance will build upon its existing PRA activities. Figure 1 it-NDE Nondestructive examination lustrates the five key principles involved in the inte-NEI Nuclear Energy Institute grated decisionmaking process; they are described in NRC Nuclear Regulatory Commission detail in Regulatory Guide 1.174 (Ref. 4). In addition, PRA Probabilistic risk assessment Regulatory Guide 1.174 describes a four-element pro-PSA Probabilistic safety assessment cess for evaluating proposed risk-informed changes as RCPB Reactor coolant pressure boundary illustrated in Figure 2.

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The key principles and the section of this guide that scribing the scope of ISI piping that would be incorpo-addresses each of these principles for RI-ISI programs rated in the overall assessment and how the inspection of l

m are as follows.

this piping would be changed. Also included in this ele-I

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1. The proposed change meets the current regulations ment is identification of supporting information and a unless it is explicitly related to a requested exemp-pr p sed plan for the licensee's interactions with the tion or rule chuge. (Regulatory Position 2.1.1)

NRC throughout the implementation of the RI-ISI.

2. The proposed change is consistent with the 1.1 Description of Proposed Changes defense-in-depth philosophy. (Regulatory Position A full description of the proposed changes in the ISI 2.1.2) program is to be prepared. This description should in-

3. The proposed change maintains sufficient safety clude:

margins. (Regulatory Position 2.1.3)

Identification of the plant's current requirements that 4.

When proposed changes result in an increase in would be affected by the proposed RI-ISI program.

core damage frequency or risk, the increases should To provide a basis from which to evaluate the pro-be small and consistent with the intent of the Com-posed changes, the licensee should also confirm that mission's Safety Goal Policy Statement. (Regula-the plant's design and operation is in accordance with tory Position 2.2) its current requirements and that engineering infor-

5. The impact of the proposed change should be mon-mation used to develop the proposed RI-ISI program itored by using performance measurement strate.

is also consistent with the current requirements.

gies. (Regulatory Position 3)

Identification of the elements of the ISI program to The individual principles are discussed in detail in be changed.

Regulatory Guide 1.174.

Identification of the piping in the p! ant that is both di-Section 2 of Regulatory Guide 1.174 describes a rectly and indirectly involved with the proposed four-element process for developing risk-informed reg-changes. Any piping not presently covered in the n

ulatory changes. i.n overview of this process is given plant's ISI program but categorized as high safety I

U) elements are performed may vary or they may occurin here and illustrated in Figure 2. The order in which the significant (e.g., through an integrated decisionmak-ing process using PRA insights) should be identified parallel, depending on the particular application and and appropriately addressed. In addition, the particu-the preference of the program developers. The process lar systems that are affected by the proposed changes is highly iterative. Thus, the final description of the pro-should be identified since this information is an aid in posed change to the ISI program as defined in Element planning the supporting engineering analyses.

1 depends on both the analysis performed in Element 2 Identification of the information that will be used to and the definition of the implementation of the ISI pro-support the changes. This could include performance gram performed in Element 3. While ISI is, by its na-data, traditional engineering analyses, and PRA in-ture, an inspection and monitoring program, it should formation.

be noted that the monitoring referred to, in Element 3 is associated with making sure that the assumptions made A brief statement describing how the proposed about the impact of the changes to the ISI program are changes meet the intent of the Commission's PRA not invalidated. For example, if the inspection intervals Policy Statement.

c.re based on an allowable margin to failure, the moni-1.2 Changes to Appmved RI-ISI Pmgrams toring is performed to make sure that these margins are not eroded. Element 4 involves preparing the documen-This section provides guidance on the need for licen-tation to be submitted to the NRC and to be maintained sees to report program activities and guiM en formal by the licensee for later reference.

NRC review of changes made to RI-ISI programs.

I The licensee should implement a process for deter-J C. REGULATORY POSITION mining when RI-ISI program changes require formal NRC review and approval. Changes made to the NRC-approved RI-ISI program that could affect the process W

1 ELEMENT 1: DEFINE TIIE PROPOSED

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CIIANGES TO ISI PROGRAMS and results that were reviewed and approved by the NRC staff should be evaluated to ensure that the basis for the In this first element of the process, the proposed staff's approval has not been compromised. All changes changes to the ISI program are defined. This involves de-should be evaluated using the change mechanisms 1.178 - 7

described in the applicable regulations (e.g.,10 CFR the Commission's Safety Goal Policy Stateraent; 50.55a,10 CFR 50.59) to determine whether NRC re-and Support the integrated decisionmaking process.

view and approval are required prior to implementation.

If there is a question regarding this issue, the licensee The scope and quality of the engineering analyses should seek NRC review and approval prior to imple.

performed to justify the changes proposed to the ISI mentation.

programs should be appropriate for the nature and 2.

ELEMENT 2: ENGINEERING ANALYSIS scope of the change. The decision criteria associated with each key principle identified above are presented As part of defining the proposed change to the licens-in the following subsections. Equivalent critena can be ee's ISI program, the licensee should conduct an engi-Proposed by the licensee if such criteria can be shown to neering evaluation of the proposed change, using and in.

meet the key principles set forth in Section 2 of Regula-tegrating a combination of traditional engineering t ry Guide 1.174.

methods and PRA. The major objective of this evaluation is to confirm that the proposed program change will not 2.1 Traditional Engineering Analysis compromise defense in depth, safety margins, and other Th.is part of the evaluation is based on tradit.ional key principles described in this guide and in Regulatory engineering methods. Areas to be evaluated from this Guide 1.174 (Ref. 4). Regulatory Guide 1.174 provides viewp int include meeting the regulations, defense-in-general guidance for perfomiing this evaluation, which depth attributes, safety margins, assessment of failure is supplemented by the RI-ISI guidance herein.

potential of piping segments, and assessment of pn-mary and secondary effects (failures) that result from 1

piping failures.

'N kN l The engineering analysis for a RI-ISI piping pro-

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gram will achieve the following:

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1. Assess compliance with applicable regulations,

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2. Perform defense-in-depth evaluation,

3. Perform safety margin evaluation, I

4.

Define piping segments, l

5. Assess failure potential for the piping segment Figure 3 Element 2 (from leaks to breaks),

6. Assess the consequences (both direct and indirect) of iping segment failure, P

The regulatory issues and engineering activities that should be considered for a risk-informed ISI pro-7.

Cateprize the piping segments in terms of safety gram are summarized here. For simplicity, the discus-(risk) significance, sions are divided into traditional and PRA analyses (see 8.

Develop an inspection program, Figure 3). Regulatory Position 2.1 addresses the tradi-

9. Assess the impact of changing the ISI program on t

tional engineering analysis, Regulatory Position 2.2 CDF and LERF, and addresses the PRA-related analysis, and Regulatory Position 2.3 describes the integration of the traditional

10. Demonstrate conformance with the key principles and PRA analyses. In reality, many facets of the tradi-(e.g., maintaining sufficient safety margins, de-fense in depth consideration, Commission's Safety tional and PRA analyses are ite ative.

Goal Policy, etc.).

The engineering evaluations are to:

I 2.1.1 Assess Compliance with Applicable Demonstrate that the change is consistent with the Regulations defense-in-depth philosophy; The engineering evaluation should assess whether L

Demonstrate that the proposed change maintains the proposed changes to the ISI programs would com-sufficient safety margins; promise compliance with the regulations. The evalua-Demonstrate that when proposed changes result in tion should consider the appropriate requirements in i

an increase in core damage frequency or risk, the the licensing basis and applicable regulatory guidance.

increase is small and consistent with the intent of Specifically, the evaluation should consider:

1.178 - 8

10 CFR 50.55a vidually and cumulatively) is consistent with the i

• A defense-in-depth philosophy. In this regard, the intent 9

ppendix A to 10 CFR Part 50 of this key principle is to ensure that the philosophy of Criterion I, "Overall Requirements" defense-in-depth is maintained, not to prevent changes Criterion II, " Protection of Multiple Fission in the way defense-in-depth is achieved. The defense-Product Barriers" in-depth philosophy has traditionally been applied in reactor design and operation to provide multiple means Criterion Ill," Protection and Reactivity Con-to accomplish safety functions and prevent the release trol Systems" of radioactive material. It has been and continues to be Criterion IV," Fluid Systems," etc an effective way to account for uncertainties in equip-ASME Boiler and Pressure Vessel Code, Section ment and human performance. Where a comprehensive XI (10 CFR Part 50.55a) risk analysis can be done, it can be used to help deter-mine the appropriate extent of defense in-depth (e.g.,

Regulatory Guide 1.84 (Ref. 20) balance among core damage prevention, containment Regulatory Guide 1.85 (Ref. 21) failure, and consequence mitigation) to ensure protec-tion of public health and safety. Where a comprehen-Regulatory Guide 1.147 (Ref. 22) sive risk analysis is not or cannot be done, traditional Appendix B to 10 CFR Part 50.

defense-in-depth consideration should be used or main-tained to account for uncertainties. The evaluation In addition, the evaluation should consider wheth-should consider the intent of the general design criteria, er the proposed changes have affected license commit-national standards, and engineering principles such as ments. A broad review of the licensing requirements the single failure criterion. Further, the evaluation and commitments may be necessary because proposed should consider the impact of the proposed change on ISI program changes could affect issues not explicitly barriers (both preventive and mitigative) to core dam-stated in the licensee's FSAR orISI program documen-age, containment failure or bypass, and the balance tation.

among defense-in-depth attributes. The licensee should The Director of the Office of Nuclear Regulation is select the engineering analysis techniques, whether allowed by 10 CFR 50.55a to authorize alternatives to quantitative or qualitative, appropriate to the proposed the specific requirements of this regulation provided change (see Regulatory Guide 1.174, Reference 4, for the proposed alternative will ensure an acceptable level ddtional guidance).

of quality and cafety. Thus, alternatives to the accept-An important element of defense in depth for RI-able RI-ISI approaches presented in this guide may be ISI is maintaining the reliability ofindependent barri-proposed by licensees so long as supporting informa-ers to fission product release. Class 1 piping (primary tion is provided that demonstrates that the key prin-coolant system)is the second boundary between the ra-ciples discussed in this guide are maintained.

dioactive fuel and the general public. If a RI-ISI pro-The licensee should include in its RI-ISI program gr m C tegorized, for example, all the hot and cold legs submittal the necessary exemption requests, technical I O* Primary system piping as LSS and calculated specification amendment requests (if applicable), and that, with no inspections, the frequency ofleaks would relief requests necessary to implement its RI-ISI pro-n t increase beyond existing performance history of the gram.

ASME Code, the staff would continue to require some level of NDE inspection.

NRC-endorsed ASME Code Cases that apply risk-infarmed ISI programs will be consistent with this reg.

2.1.3 Safety Margins ulatory guide in that they encourage the use of risk in-In engineering programs that affect public health sights in the selection of inspection locations and the and safety, safety margins are applied to the design and use of appropriate and possibly enhanced inspection operation of a system.These safety margins and accom-techniques that are appropriate to the failure mecha-panying engineering assumptions are intended to ac-nisms that contribute most to risk.

count for uncertainties, but in some cases can lead to j 2.1.2 Defense in Depth E5aluation operational and design constraints that are excessive m

and costly, or that could detract from safety (e.g., result

,_j As stated in Regulatory Guide 1.174 (Ref. 4), the in unnecessary radiation exposure to plant personnel).

engineering analysis should evaluate whether the im-Insufficient safety margins may require additional pact of the proposed change in the ISI program (indi-attention. Prior to a request for relaxation of the existing 1.178 - 9

requirements, the licensee must ensure that the uncer-could encompass multiple criteria, as long as a sound tainties are adequately addressed. The quantification of engineering and accounting record is maintained and uncertainties would likely require supporting sensitiv-can be applied to an engineering analysis in a consistent and sound process. Consequences of failure may be de-ity analyses.

0".ed in terms of an initiating event, loss of a particular i

The engineering analyses should address whether the impacts of the changes proposed to the ISI program I'"*'. I ss f a system, or combinations thereof. The 1 cation of the piping in the plant, and whether inside or are consistent with the key principle that adequate utside the containment or compartment, should be safety margins are maintained. The licensee is expected taken into consideration when defining piping seg-to select the method of engineering analysis appropri-ments.

ate for evaluating whether sufficient safety margins would be maintained if the proposed change were im-The definition of a piping segment can vary with plemented. An acceptable set of guidelines for making the methodology. Defining piping segments can be an that assessment are summarized below. Other equiva-iterative process. In general, an analyst may need to lent decision criteria could also be found acceptable.

modify the description of the piping segments before they are finalized. This guide does not impose any spe-Sufficient safety margins are maintained when:

cific definition of a piping segment, but the analysts Codes and standards (see Regulatory Position and the definition of a segment must be consistent and 2.1.1) or alternatives approved for use by the NRC technically sound.

are met, and i

2.1.5 Assess Piping Failure Potential Safety analysis acceptance criteria in the licensing basis (e.g., updated FSAR, supporting analyses)

The engineering analysis includes evaluating the are met, or proposed revisions provide sufficient failure potential of a piping segment. Figure 4 identifies margin to account for analysis and data uncer-the three means for estimating the failure potential of a i

tainty.

piping segment: data, fracture mechanics computer f

codes, and the expert elicitation process. Determining l

2.1.4 Piping Segments the failure potential of piping segments, either with a I

A systematic approach should be applied when quantitative estimate or by categori7ation into groups, analyzing piping systems. One acceptable approach is should be based on an understandmg of degradation to divide or separate a piping system into segments; dif-mechanisms, operational characteristics, potential dy-ferent criteria or definitions can be applied to each pip-namic loads, flaw size, flaw distribution, inspection pa-(

ing segment. One acceptable method is to identify seg-rameters, experience data base, etc. The evaluation l

l ments of piping within the piping systems that have the should state the appropriate definition of the failure same consequences of failure. Other methods could potential (e.g., failure on demand or operating failures suNivide a segment that exhibits a given consequence associated with the piping, with the basis for the defini-into segments with similar degradation mechanisms or tion) that will be needed to support the PRA or risk as-similar failure potential. The definition of a segment sessment. The failure potential used in or in support of ESTIMATING FAILURE POTENTTAI as h M Tyd h ~

EXPEKl's g

E ON

!,L

~ MTM MECHANICS "l

g p%jCODESi iP

((IFNEEDED)

M

$sw dc e e,%

4 w

Figure 4 Estimating Failure Potential of Piping Segments 1.178 - 10

l the analysis should be appropriate for the specific envi-for leaks, disabling leaks, and breaks, the failure poten-ronmental condition, degradation mechanisms, and tial for all three break types should be addressed.

] (failure modes for sach.' ping location and break size 1

/

e.g., leak, disabling leak, break). When data are ana.

2.1.6 Assess Consequences of Piping Segment s"

lyzed to develop a categornation process relating de-Failuirs gradation mechanisms to failure potential, the data When evaluating the risk from piping failures, the should be appropriate and publicly available. When an analyst needs to evaluate the potential consequences, or elicitation of expert opinion is used in conjunction failures, that a piping failure can initiate. This can be ac-with, or in lieu of, probabilistic fracture mechanics complished by performing a detailed walkdown of a analysis or operating data, a systematic process should nuclear power facility's piping network. Assessment of be developed for conducting such an elicitation. In such internal and external events, including resulting pri-cases, a suitable team of experts should be selected and mary and secondary effects of piping failures (e.g.,

trained (Ref. 23,24).

leaks, disabling leaks, and breaks) are important pa-rameters to the risk-informed program (see Figure 5).

To understand the impact of specific assumptions Leaks can result in failures of electrical components or models used to characterize the potential for piping caused by jet impingement. Disabling leaks and full failure, appropriate sensitivity or uncertainty studies breaks can lead to a loss of system function, flooding-should be performed. These uncertainties include, but induced damage, and initiating events. Full breaks can are not limited to, design versus fabrication differences, lead to damage resulting from pipe whip, as well as variations in material properties and strengths, effects flooding and initiating events. Each of these break of vanous degradation and aging mechanisms, varia-types has its associated failure potential that is evalu-tion in steady-state and transient loads, availability and ated in Regulatory Position 2.1.5. A failure modes and accuracy of plant operating history, availability ofin-consequence assessment is performed to identify the spection and maintenance program data, applicability potential failures, from piping leaks to breaks. Internal and size of the data base to the specific degradation and flooding PRAs can identify the impact of jet impinge-piping, and the capabilities of analytic methods and ment and flooding to the RI-ISI program. The failures O

models to predict realistic results. Evaluation of these are used as input to the risk analysis. Alternative meth-uncertainties provides insights to the input parameters ods for evaluating consequences should be submitted that affect the failure potential, and therefore require to the NRC for review and approval. These evaluations careful consideration in the analysis.

are expected to provide information for the conse-quence analysis. They are not intended to be used in The methodology, process, and rationale used to lieu of the plant licensing basis.

determine the likelihood of failure of piping segments should be independently reviewed during the final clas-2.1.7 Pn>babilistic Fracture Mechanics Evaluation sification of the risk significance of each segment. Ref-When implementing probabilistic fracture me-erencing applicable generic topical reports approved by chanics computer programs that estimate stwetural the NRC is one acceptable means to standardize the reliability and are used in risk assessment of piping, or process. This review should be documented and a sum-other analytic methods for estimating the failure poten-mary discussion of the review should be included in the tial of a piping segment, some of the important parame-submittal. When new computer codes are used to de-ters that need to be assessed in the analysis include the velop quantitative estimates, the techniques should be identification of structural mechanics parameters, deg-verified and validated against established industry radation mechanisms, design limit considerations, op-codes and available data. When data are used to evalu-erating practices and environment, and the develop-ate the likelihood of piping failures, the data should be ment of a data base or analytic methods for predicting submitted to the NRC or referenced by an NRC ap-the reliability of piping systems. Design and opera-proved topical report. As stated in Regulatory Guide tional stress or strain limits are assessed. This informa-1.174 (Ref. 4)," data, methods, and assessment criteria tion is available to the licensee in the design informa-used to support regulatory decisionmaking must be tion for the plant. The loading and resulting stresses or scrutable and available for public review."It is the re-strains on the piping are needed as input to the calcula-c) sponsibility of the licensee to provide the data, meth-tions that predict the failure probability of a piping seg-V ods, and justification to support its estimation of the ment. The use of validated computer programs, with failure potential of piping segments. Since conse-appropriate input, is strongly recommended in a quanti-quences of and potential for piping failures could differ tative RI-ISI program because it may facilitate the 1.178 - 11

LEAKIBREAK CONSEQUENCES Effects from Jet Impingement Leak l

l Disabling Leak or Full Break Loss of System Function Disabling Leak (plant trip) or Initiating Event Full Bitak Disabling Leak or Full Break Effects from Flooding Full Break Effects from Pipe Whip Figure 5 Mapping of Probabilities and Consequences for RI-ISI Analysis regulatory evaluation of a submittal. The analytic tant element in ensuring this quality. The licensee's method should be validated with applicable plant and submittal should discuss measures used to ensure ade-quate quality, such as a report of a peer review (when industry piping performance data.

performed) that addresses the appropriateness of the PRA model for supporting a risk assessment of the 2.2 Prubabilistic Risk Assessment change under consideration. The report should address in accordance with the Commission's policy on any limitations of the analysis that aie expected to im-PRA, the risk informed application process is intended pact the conclusion regarding the acceptability of the not only to support relaxation (number ofinspections, proposed change. The licensee's resolution of the fmd-mspection intervals and methods), but also to identify ings of the peer review, certification, or cross compari-areas where mereased resources shou.d be allocated t son, when performed, should also be submitted. This enhance safety. Therefore, an acceptable RI-ISI pro-response could indicate whether the PRA was modified cess should not focus exclusively on areas in which re-or could justify why no change to the PRA was neces-duced mspection could be justified. This section ad-sary to support decisionmaking for the change under dresses ISI-specific considerations m the PRA t consideration.

support relaxation of mspections, enhancement ofin-spections, and validation of component operability.

2.2.1 Modeling Piping Failures in a PRA The scope of a RI-ISI program, therefore, should in-Input from the traditional engineering analysis ad-clude a review of Code-exempt piping for partial or dressed in Regulatory Position 2.1 includes identifica-full-scope programs and the review of non-Code piping tion of piping segments from the point of view of the for full-scope RI-ISI programs.

failure potential (degradation mechanisms) and conse-quences (resulting failure modes and consequential pri-The general methodology for using PRA in regula.

mary and secondary effects). The traditional analysis tory applications is discussed in Regulatory Guide identifies both the primary and secondary effects that 1.174. The PRA can be used to categorize the piping can result from a piping failure, such as a leak, disabling segments into HSS and LSS classification (or more leak, and a break. The assessment of the primary and classifications, if a finer graded approach is desired) secondary failures identifies the portions of the PRA and to confirm that the change in risk caused by the that are affected by the piping failure.

change in the ISI program is in accordance with the guidance of Regulatory Guide 1.174 (Ref. 4).

Each pipe segment failure may have one of three types ofimpacts on the plant.

if a licensee elects to use PRA to enhance or modify

1. Ini:iating event failures when the failure directly its activities affecting the safety-related functions of causes a transient and may or may not also fail one SSCs subject to the provisions of Appendix B to or more plant trains or systems.

10 CFR Part 50, the pertinent requirements of Appen-dix B will also apply to the PRA. In this context, there-2.

Standby failures are those failures that cause the fore, a licensee would be expected to control PRA ac-loss of a train or system but which do not directly tivity in a manner commensurate with its impact on the cause a transient. Standby failures are character-facility's design and licensing basis and in accordance ized by train or system unavailability that may re-with all applicable regulations and its OA program de-quire shutdown because of the technical specifica-scription. An independent peer review can be an impor-tions or limiting conditions for operation.

1.178 - 12

3. Demand failures are failures accompanying a de-provide a discussion and justification of the ranges se-mand for a train or system and are usually caused lected. The' use of ranges instead of individual results by the transient-induced loads on the segment dur-estimates may require fewer calculations, but the cate-ing system startup.

gorization process and decision criteria should bejusti-The impact of the pipe segment failure on risk fled, well defined, and repeatable.

should be evaluated with the PRA. Evaluation may in.

2.2.1.1 Dependencies and Common Cause Fall-volve a quantitative estimate derived from the PRA, a ures. The effects of dependencies and common cause systematic technique to categorize the consequence of failures (CCFs) for ISI components need to be consid-the pipe failure on risk, or some combination of quanti.

ered carefully because of the significance they can have fication and categorization. If a segment failure were to on CDF. Generally, data are insufficient to produce lead to plant transients and equipment failures that are lP ant-specific estimates based solely on plant-specific not at all represented in the PRA (a new and specific ini.

data. For CCFs, data from generic sources may be re-tiating event, for example), the evaluation process

quired, should be expanded to assess these events.

2.2.1.2 Human Reliability Analyses To Isolate PRAs normaily do not include events that repre-Piping Breaks. For ISI-specific analyses, the human sent failure ofindividual piping segments nor the struc-reliability analysis methodology used in the PRA must tural elements within the segments. A quantitative esti-account for the impact that the piping segment break mate of the impact of segment failures can be done by w uld have on the operator's ability to respond to the modifying the PRA logic to systematically and ex-event. In addition, the reliability of the inspection pro-plicitly include the impact of the individual pipe seg-gram (including both operator and equipment qualifi-ment failures. The impact of each segment's failure on cation), which factors into the probability of detection, risk can also be estimated without modifying the PRA's should also be addressed.

logic by identifying an initiating event, basic event, or 2.2.2 Use of PRA for Categorizing Piping group of events, already modeled in the PRA, whose Segments failures capture the effects of the piping segment's fail-Once the impact of each segment's failure on plant O

case (, referred to as the surrogate approach). In either ure risk metrics has been determined, the safety signifi-to assess the impact of a particular segment fail-cance of the segments is developed. The method of ure, the analyst sets the appropriate events to a failed categorizing a piping segment can vary. For example,if state in the PRA (by assigning them a frequency or the pipe failure event frequency or probability are esti-probability of 1.0) and requantifies the PRA or the ap-mated by structural mechanics methods as discussed in propriate parts of the PRA as needed. The requantifica-Regulatory Position 2.1.5 and the events are incorpo-tion should explicitly address truncation errors, since rated into the PRA logic model, importance measure cut set or truncated sequences may not fully capture the calculations and the determination of safety signifi-impact of multiple failure events. This yields condi-cance, as discussed in Regulatory Guide l.174 and SRP tional CDF (CCDF) and conditional LERF (CLERF)

Chapter 19 (Refs. 4 and 8), may be performed. Alterna-estimates when the segment failure would trip the tively, if a CCDF, CLERF, CCDP, or CLERP (depend-plant, and conditional core damage probabilities ing on the impact the segment failure has on the plant)

(CCDP) and conditional large early release probabili-are estimated for each segment from the PRA, a CDF ties (CLERP) when the segment failure would not trip and LERF caused only by pipe failures may be devel-the plant.

oped by combining the conditional consequences and If a systematic technique is used to categorize the segment failure probabilities or frequencies external to consequence of pipe failures, it should also be based on the PRA logic model. Importance measures can also be PRA results. In this case, however, the categories may developed using these results and these measures be represented by ranges of conditional results, and compared to appropnate threshold criteria to support instead of quantifying the impact of each segment fail, the determination of the safety significance of each seg-ure, the process should provide for determining which ment. The calculations used in such a process should range each segment's failure would lie within. In gen.

yield well defined estimates of CDF, LERF, and impor-I eral, the consequences would range from high, for those tance measures. The licensee should provide a discus-segments whose failure would have a high likelihood of sion of and justification for the threshold criteria used.

leading to core damage or large early release, to low for As discussed in Regulatory Position 2.2.1, the con-those segments whose failure would likely not lead to sequence of segment failures may be represented by core damage or large early release. The licensee should categories of consequences instead of quantitative 1.178 - 13

• estimates for each segment. In this case, the potential The method for selecting the number of piping ele-for pipe failare as discussed in Regulatory Position ments to be inspected should be justified.

2.1.5 would also be developed as categories ranging 3.

ELEh1ENT 3: Ih1PLEh1ENTATION, radation mecha-from high to low depending on the deg'kelihood that the PERFORh1ANCE h10NITORING, AND nisms present and the corresponding li CORRECTIVE ACTION STRATEGIES segment will fail.These consequence and failure likeh.-

Integrating the information obtained from Ele-hood categories should be systematically combined to ments 1 and 2 of the RI-ISI process (as described in develop categories of safety significance. The licensee Regulatory Positions 1 and 2 of this guide), the licensee should provide a discussion and justification relating develops proposed RI-ISI implementation, perfor-the consequence and failure likelihood categories to the mance monitoring, and corrective action strategies.

safety-significant category assigned to each combina.

The RI-ISI program should identify piping segments tion.

whose inspection strategy (i.e., frequency, number of The safety-significance category of the pipe seg-inspections, methods, or all three) should be increased ment will help determine the level of inspection effort as well as piping segments whose inspection strategies devoted to the segment. In general, higher safety-might be relaxed. The program should be self-correct.

significant segments will receive more inspections and ing as experience dictates. The program should contain more demanding inspections than less significant seg-performance measures used to confirm the safety in-ments. In any integrated categorization process, the sights gained from the risk analyses.

principles in Regulatory Guide 1.174 need to be ad-Upon approval of the RI-ISI program, the licensee dressed. Irrespective of the method used in the analysis, should have in place a program for inspecting all HSS the licensee needs tojustify the final categorization pro-and LSS pipingidentified in its program. (Note that ref-cess as being robust and reasonable with respect to the erence to HSS piping is broadened when implementing analysis uncertainties.

a more detailed graded categorization process, such as low, medium, and high safety significant. For discus-2.2.3 Demonstrate Change in Risk Resulting from sion purposes, a two-category process (e.g., HSS and Change in ISI Pmgram LSS) will be assumed. Requirements for medium and I SS piping will be addressed on a case-by-case basis.)

Any change in the ISI program has an associated The number of required inspections should be a product risk impact. Evaluation of the change in risk may be a f the systematic application of the risk informed pro-detailed calculation or it may be a bounding estimate

cess, supported by sensitivity studies as appropriate. The change may be a risk increase, a risk decrease, or risk 3.1 Pmgram Implementation neutrality. The change is evaluated and compared with A licensee should have in place a schedule for in-the guidelines presented in Regulatory Guide 1.174.

specting all segments categorized in its RI-ISI program The staff expects that a RI-ISI program would lead to s LSS and HSS.This schedule should include inspec-both risk reduction and reduction in radiation exposure tion strategies and inspection frequencies, inspection to plant personnel.

methods, the sampling program (the number of ele-ments/ areas to be inspected, the acceptance criteria, 2.3 Integrated Decisionmaking etc.) for the HSS piping that is within the scope of the ISI pr gram, including piping segments identified as Regulatory Positions 2.1 and 2.2 address the ele-HSS that are not currently in the ISI program.

ments of traditional analysis and PRA analysis of a RI-ISI program. These elements are part of an integrated The analysis for a RI-ISI program will, in most decisionmaking process that assesses the acceptability cases, confirm the appropriateness of the inspection in-of the program.The key principles of Regulatory Guide terval and scope requirements of the ASME Boiler and 1.174 (Ref. 4), as highlighted in Figure 1, are systemat-Pressure Vessel Code (B&PVC)Section XI Edition ically addressed. Technical and operations personnel at and Addenda committed to by a licensee in accordance the plant review the information and render a finding of with 10 CFR 50.55a. The requirements for these inter-HSS or LSS categorization for each piping segment un-vals are contained in Section XI of the B&PVC. How-der review. Detailed guidelines for the categorization of ever, should active degradation mechanisms surface, piping segments should be developed and discussed the inspection interval would be modified as appropri-with the group responsible for the determination (typi-ate. Updates to the RI-ISI program should be per-cally performed by the plant's expert panel).

formed at least periodically to coincide with the 1.178 - 14

inspection program requirements contained in Section dures to update the PRA (which may be more restrictive XI under inspection Program B. The RI-ISI program than a Section XI period type update) or as new de-

/7, should be evaluated periodically as new information gradation mechanisms are identified.

)

becomes available that co'uld impact the ISI program.

For example, if changes to the PRA impact the deci-3.2.2 Changes to Plant Design Features sions made for the RI-ISI program, if plant design and As changes to plant design are implemented, operations change such that they impact the RI-ISI pro.

changes to the inputs associated with RI-ISI program gram, if inspection results identify unexpected flaws, segment definition and element selections may occur. It or if replacement activities impact the failure potential is important to address these changes to the inputs used of piping, the effects of the new information should be in any assessment that may affect resultant pipe failure assessed. The periodic evaluation may result in updates Potentials used to support the RI-ISI segment defini-to the RI-ISI program that are more restrictive than re.

tion and element selection. Some examples of these in-quired by Section XI. As plant design feature changes Puts would include:

are implemented, changes to the input associated with Operating characteristics (e.g., changes in water the RI-ISI program segment definition and element chemistry control) selections should be reviewed and modified as needed.

Changes to piping performance, the plant procedures Material and configuration changes that can affect system operating parameters, piping in-Welding techniques and procedures spection, component and valve lineups, equipment op-Construction and preservice examination results erating modes, or the ability of the plant personnel to perform actions associated with accident mitigation Stress data (operating modes, pressure, and tem-should be reviewed in any RI-ISI program update.

perature changes)

Leakage and flaws identified during scheduled inspec-In addition, plant design changes could result in tions should be evaluated as part of the RI-ISI update.

significant changes to a plant's CDF or LERF, which in Piping segments categorized as HSS that are not in turn could result in a change in consequence of failure

[3 the licensee's current ISI program should (wherever ap-f r system piping segments.

\\

propriate and practical) be inspected in accordance with 3.2.3 Changes to Plant Procedures applicable ASME Code Cases (or revised ASME Changes to plant procedures that affect ISI, such as Code), including compliance with all admiuistrative system operating parameters, test intervals, or the abil-requirements. Where ASME Section XIinspection is ity of plant operations personnel to perform actions as-i not practical or appropriate, or does not conform to the sociated with accident mitigation, should be included key principles identified in this document, alternative for review in any RI-ISI program update. Additionally, inspection intervals, scope, and methods should be de-veloped by the licensee to ensure piping integrity and t changes in those procedures that affect component in-spection intervals, valve lineups, or operational modes detect piping degradation. A summary of the piping of equipment should also be assessed for their impact segments and their proposed inspection intervals and on changes in postulated failure mechanism initiation scope should be provided to the NRC prior to imple-or CDF/LERF contribution.

mentation of the RI-ISI program at the plant.

For piping segments categorized as HSS that were 3.2.4 Equipment Performance Changes the subject of a previous NRC-approved relief request Equipment performance changes should be re-or were exempt under existing Section XI criteria, the viewed with system engineers and maintenance per-licensee should assess the appropriateness of the relief sonnel to ensure that changes in performance parame-or exemption in light of the risk significance of the pip.

ters such as valve leakage, increased pump testing, or ing segment.

identification of vibration problems is included in the periodic evaluation of the RI-ISI program update. Spe-l 3.2 Performance Monitoring cific attention should be paid to these conditions if they 3.2.1 Periodic Updates w re n t previously assessed in the qualitative inputs to the element selections of the RI-ISI program.

The RI-ISI program should be updated at least on g) the basis of periods that coincide with the inspection 3.2.5 Examination Results program requirements contained in Section XI under When scheduled RI-ISI program NDE examina-I Inspection Program B. These updates should be per-tions, pressure tests, and awresponding VT-2 visual formed more frequently if dictated by any plant proce-examinations for leakage have been completed, and if 1.178 - 15

unacceptable flaws, evidence of service related degra-

1. The evaluation of the implementation program will dation, or indications of leakage have been identified, be based on the attributes presented in Regulatory the existence of these conditions should be evaluated.

Positions 3.1 through 3.3 of this Regulatory Guide 1.178, This update of the RI-ISI program should follow the applicable elements of Appendix B to 10 CFR Part 50

2. The corrective action program should provide rea-to determine the adequacy of the scope of the inspection sonable assurance that a nonconforming compo-nent will be brought back into conformance in a

program, timely fashion. The corrective actions required in 3.2.6 Information on Individual Plant and ASME Section XI should continue to be followed.

Industry Failures

3. Evaluations within the corrective action program Review of individual plant maintenance activities may also include:

associated with repairs or replacements, including Ensuring that the root cause of the condi-identified flaw evaluations,is an important part of any tion is determined and that corrective ac-periodic update, regardless of whether the activity is the tions are taken to preclude repetition. The result of a RI-ISI program examination. Evt.luating identification of the significant condition this information as it relates to a licensee's plant pro-adverse to quality, the cause of the condi-vides failure information and trending information that tion, and the corrective action are to be may have a profound effect on the element locations documented and reported to appropriate currently being examined under a RI-ISI program. In-levels of management.

dustry f ailure data isjust as important to the averall pro-Determining the impact of the failure or a

gram as the owner's information. During the periodic n nc nf rmance on system or train oper-update, industry data bases (including available inter-ability since the previous inspection.

national data bases) should be reviewed for applicabil-Assessing the applicability of the failure ity to the owner's plant.

or nonconforming condition to other 3.3 Corrective Action Programs components in the RI-ISI program.

Correcting other susceptible RI-ISI com-(

Each licensee of a nuclear power plant is responsi-ble for having a corrective action program, consistent ponents as necessary.

l incorporating the lessons in the plant data l

with Regulatory Guide 1.174 (Ref. 4). Measures are to be established to ensure that conditions adverse to quah base and computer models,if appropriate.

l ity, such as failures, malfunctions, deficiencies, devi-Assessing the validity of the failure rate ations, defective material and equipment, and noncon.

and unavailability assumptions that can formances, are promptly identified and corrected. In result from piping failures used in the the case of significant conditions adverse to quality, the PRA or in support of the PRA, and measures must ensure that the cause of the condition is Considering the effectiveness of the com-determined and corrective action is taken to preclude repetition. The identification of the significant condi-ponent's inspection strategy in detecting tion adverse to quality, the cause of the condition, and the failure or nonconforming condition.

l the corrective a; tion are to be documented and reported The inspection interval would be reduced i

to appropriate levels of management.

or the inspection methods adjusted, as ap-pmpriate, when the component (or group For Code piping categorized as llSS, this correc-f components) experiences repeated fail-l tive action program should be consistent with applica-ures or nonconformmg conditions.

ble Section XI provisions. For non-Code and Code-4.

The corrective action evaluation should be pro-J exempt piping categorized as llSS, appropriate Section vided to the licensee's PRA and RI-ISI groups so XI provisions should also be used, or the licensee that any necessary model changes and regrouping should submit an alternative program based on the risk are done, as appropriate.

. significance of the piping.

5. The Rl-ISI program documents should be revised 3.4 Acceptance Guidelines to document any RI-ISI program changes resulting from the corrective actions taken, These acceptance guidelines are for the imple.

mentation, monitoring, and corrective action programs 6.

A program is in place that monitors industry find-for the accepted RI-ISI program plan.

ings.

1.178 - 16

7.

Piping is subject to examination. The examination tal. RefereNes to NRC-approved generic topical re-requirements include all piping evaluated by the ports that address the methodology and issues risk-informed process and categorized as high requested in a submittal are acceptable. Since topical

(

)

safety significant.

reports could cover more issues than applied by a li-8.

The inspection program is to be completed during censee or the licensee may elect to deviate from the full each ten-year inspection interval with the follow-body of issues addressed in the topical report, such dis-ing exceptions.

tinctions should be clearly stated. If a licensee refer-8.1 If, during the interval, a reevaluation using the ences a topical report that has not been approved by the RI-ISI process is conducted and scheduled NRC, the time required to review the submittal may be delayed.

items are no longer required to be examined, these items may be eliminated.

The following items should be included in the ap-8.2 If, during the interval, a reevaluation using the plication to implement a RI-ISI program.

RI-ISI process is conducted and items must be added to the examination program, those items A request to implement a RI-lSi program as an au-will be added.

thorized alternative to the current NRC endorsed ASME Code pursuant to 10 CFR 50.55a(a)(3)(i).

9.

Locations selected for successive and additional The licensee should also provide a description of inspections should be subjected to successive and how the proposed change impacts any commit-additional examinations consistent with Section XI ments made to the NRC.

requirements at appropriate intervals.

10. Examination and Pressure Test Requirements.

Detailed discussions on each of the following five Pressure testing and VT-2 visual examinations are key principles of risk-informed regulations (see to be performed on Class 1,2, and 3 pipmg systems Section 2 of Regulatory Guide 1.174 (Ref. 4) foi in accordance with Section XI, as specified in the more details)'

licensee's ISI program. The pressure testing and

1. The proposed change meets the current regula-p VT-2 examinations are also to be performed on tions unless it is explicitly related to an alterna-

)

non-Code HSS piping and on non-Code LSS pi -

P

,V ing with high failure potential.

tive requested under 10 CFR 50.55a(a)(3)(i), a requested exemption, or a rule change.

Examination qualification and methods and per-2.

sonnel qualification are to be m, accordance with The proposed change is consistent with the de-the edition and addenda endorsed by the NRC fense-in-depth philosophy (see detailed dis-through 10 CFR R.55a," Codes and Standards."

cussions in Section 2.2.1.1 of Regulatory Guide 1.174).

11. Acceptance standards for identified flaws and re-pair or replacement activities are to be performed in

3. The proposed change maintains sufficient accordance with the B&PVC Section XI require-s fety margins (see detailed discussions in ments.

Section 2.2.1.2 in Regulatory Guide 1.174).

12. Records and reports should be prepared and main-4.

When proposed changes result in an increase in tained in accordance with the B&PVC Section XI core damage frequency and/or risk, the in-Edition and Addenda as specified in the licensee's creases should be small and consistent with the ISI program, guidance in Regulatory Guide 1.174.

4. ELEMENT 4: DOCUMENTATION

5. The impact of the proposed change should be The recommended contents for a plant-specific monitored using performance measurement risk-infcrmed ISI submittal are presented here. This strategies, guidance will help ensure the completeness of the infor-Identification of the aspects of the plant's current mation provided and aid in minimizing the time needed requirements that would be affected by the pro-for the review process.

posed RI-ISI program. This identification should

'q 4.1 Documentation that Should He Included in a include all commitments (for example, the IGSCC Licensee's RI-ISI Submittal inspections and other commitments arising from generic letters affecting piping integrity) that the li-

~

Table i provides an overall summary of the infor-censee intends to change or terminate as part of the mation needed to support a risk-informed ISI submit.

RI-ISI program.

1.178 - 17

Table 1 Documentation Summary Table PRA Quality Address the adequacy of the PRA model used in the calculations.

Address the acceptance guidelines in Regulatory Position 2 of this document and in Regulatory Guide 1.174 (Ref. 4).

Failure Probability Calcula-Address the methods used to calculate or categorize the failure probability or tions frequency of a piping element Any use of expert elicitation should be fully documented.

Changes in CDF and LERF Address the change in CDF and LERF resulting from changes to the ISI pro-gram ISI Systems identify all the systems inspected based on the current ISI programs and compare the systems for the RI-ISI programs.

Segmentation Identify methods used to segment piping systems, if applicable.

Categorization Identify methods used to categorize piping segments and elements as HSS,

)

LSS, high failure potential, and low failure potential.

Identify all the HSS-HFP and HSS-LFP elements (format may differ based on decision matrix employed).

Sampling Method Identify the method used to calcula : the number of elements to be inspected.

Document the method used to establish elements within a lot. Address how this method provides an acceptable level of quality and safety per 10 CFR 50.55a(a)(3)(i).

Iwcations ofInspections Provide a system / piping diagram or table that compares the existing ISI loca-i tions of inspection with the RI-ISI location of inspection.

Address the reasons for the changes.

l Failure Probabilities Identify the methods used to arrive at the failure probabilities for piping seg-ments.

Performance Monitoring Discuss the performance goals and corrective action programs.

j Periodic Reviews Identify the frequency of performance monitoring and activities in support of the RI-ISI program. Address consistency with other RI programs (e.g.,

Maintenance Rule, IST, Tech Specs).

Describe the QA program used to ensure proper implementation of RI-ISI QA Program process and categorization and consistency with other R1 programs.

Expert Elicitation Identify any use of the expert elicitation process to estimate a failure proba-bility for piping. Address the reasons why an expert elicitation was required, j

provide all supporting information used by the experts, document the conclu-sions, and address how the results will be incorporated in an industry data base or computer code, or why it is not necessary to make the findings avail-able to the industry.

Each weld to be inspected Identify: 1.The inspection method to be used 2.The applicable degradation mechanism to be inspected, and 3.The frequency ofinspection Address each of the key prin-Verify compliance with applicable regulations, defense-in-depth, safety mar-ciples and the integrated deci-gins, etc.

s sionmaking guidelines (e.g.,

Regulatory Position 2.3)

Implementation and monitor-Address the acceptance guidelines outlined in Regulatory Position 3 of this ing program regulatory guide.

j 1.178 - 18

A summary of events involving piping failures that justification for the number of elements to be o

j have occurred at the plant or similar plants. Include inspected.

in the summary any lessons learned from those

._)

events and indicate actions taken to prevent or The degradation mechanisms for each seg-l

~)

minimize the potential for recurrence of the events.

ment (if segments contain welds exposed to different degradation mechanism, for each Identification of the specific revisions to existing weld) used to develop the failure potential of inspection schedules, locations, and methods that each segment.

would result from implementation of the proposed program.

Equipment assumed to fail as a direct or indi-rect consequence of each segment's failure (if Plant procedures or documentation containing the segments contain welds with different failure guidelines for all phases of evaluating and imple-consequences, for each weld).

menting a change in the ISI program based on pro-babilistic and traditional insights. These should

- A description of how the impact of the change include a description of the integrated decision.

between the current Section XI and the pro-making process and criteria used for categorizing posed RI-ISI programs is evaluated or the safety significance of piping segments, a de.

bounded, and how this impact compares with scription of how the integrated decisionmaking the risk guidelines in Section 2.2.2.2 of Regu-was performed, a description and justification of 1 tory Guide 1.174.

the number of elements to be inspected in a piping segment, the qualifications of the individuals mak-The means by which failure probabilities or fre-mg the decisions, and the guidelines for making quencies or potential were determined. The data those decisions.

should be provided in the submittal for analyses that rely on operational data for determining failure The result:; of the licensee's ISI-specific analyses frequencies or potential. Reliance on fracture me-used to support the program change with enough chanics structural reliability and risk analysis n

detail to be clearly understandable to the reviewers codes should be documented and validated. Re-(

)

of the program. These results should include the liance on the expert elicitation process should be following information.

(

fully documented. (NOTE: Expert clicitation is only used if data are not sufficient to estimate the

- A list of the piping systems reviewed.

failure probability and frequency of a piping seg-

- A list of each segment, including the number mer.t. Data assessment is not an expert elicitation of welds, weld type and properties of the weld-process and can normally be performed by plant ing material and base metal, the failure poten-Personnel.)

tial, CDF, CCDF/CCDP, LERF, CLERF, im-A description of the PRA used for the categoriza-portance measure results (RAW, F-V, etc.) and tion process and for the determination of risk im-justification of the associated threshold val-ues, degradation mechanism, test and inspec-pact, in terms of the process to ensure gaality, scope, and level of detail, and how limitations in tion intervals used in orin support of the PRA, etc. Results from other methods used to de-quality, scope, and level of detail are compensated velop the consequences and categorization of for in the integrated decisionmaking process sup-each segment (or weld) should be documented porting the ISI submittal. The key assumptions in a similar level of detail. (NOTE: Table 2 used in the PRA that impact the application (i.e.,

licensee voluntary actions), elements of the moni-provides an example of a summary of possible methods for obtaining failure probabilities toring program, and commitments made to support the application should be addressed.

based on specified degradation mechanisms.

The staff recommends that licensees provide If the submittalincludes modified inspection inter-such a table with supporting discussions.)

vals, the methodology and results of the analysis should be submitted.

For the selected limiting locations, provide ex-q amples of the failure mode, failure potential, A description of the implementation, performance

)

failure mechanism, weld type, weld location, monitoring, and corrective action strategies and and properties of the welding material and programs in sufficient detail for the staff to under-I base metal. Provide a detailed description and stand the new ISI program and its implications.

1.178 - 19

Applicable documentation discussed under the with the role the PRA results play in the integrated Cumulative Risk documentation for submittal in decisionmaking process. In addition to documen-Section 1.3 of Regulatory Guide 1.174 (Ref. 4).

tation on the PRA itself, analyses performed in support of the ISI submittal should be documented Reference to NRC-approved topical reports on im-in a manner c nsistent with the basehne documen-plementing a RI-ISI and supporting documents.

tation. Such analyses may, elude:

m Variations from the topical reports and supporting documents should be clearly identified.

- The process used to identify initiating events developed in support of the RI-ISI submittal Detailed justification for the proposed regulatory and the results from the process.

action (e.g., how the proposed program meets the Any event and fault trees developed during the i

requirements set in 10 CFR 50.55a(a)(3)(i)).

RI-ISI submittal preparation.

4.2 Documentation That Should Be Available Documentation of the methods and techniques Onsite for Inspection used to identify and quantify the impact of pipe The licensee should maintain at its facility the tech-failures using the PRA, or in support of the nical and administrative records used in support of its PRA, if different from those used during the submittal, or should be able to generate the information development of the baseline PRA.

on request. This information should be available for

- The techniques used to identify and quantify NRC review and audit. If changes are planned to the ISI human actions.

program based on internal procedures and without prior

- The data used in any uncertainty calculations NRC approval, the following information should also or sensitivity calculations, consistent with the

}

be placed in the plant's document control system so that the analyses for ar.y given change can be identified and guidance provided in Regulatory Guide 1.174.

reviewed. The record should include, but not be limited How uncertainty was accounted for in the seg-to, the following information.

ment categorization, and the sensitivity stud-j ies performed to ensure the robustness of the Plant and applicable industry data used in support categonzation.

of the RI-ISI program. All analyses and assump.

Detailed results of the inspection program corre-tions used in support of the RI-ISI program and communications with outside organizations sup-sponding to the ISI inspection records described in porting the RI-ISI program (e.g., use of peer and the implementation, performance monitoring, and

{

independent reviews, use of expert contractors).

corrective action program accompanying the RI-ISI submittal.

Detailed procedures and analyses performed by an For each piping segment, information on weld expert panel, or other technical groups, if relied upon for the RI-ISI program, including a record of type, weld location, and properties of welding ma-deliberations, recommendations, and findings.

terial and base metal.

For each piping segment, information regarding Documentation of the plant's baseline PRA used to support the ISI submittal should be of sufficient de-the process and assumptions used to develop fail-tail to allow an independent reviewer to ascertain ure mode and failure potential (frequency /proba-(

whether the PRA reflects the current plant configu-bility), in addition to the identification of the fail-ration and operational practices commensurate ure mechanism.

l l

9 1.178 - 20

e 7-.

V L) l Table 2 Example of a Summary of Methods Used To Estimate Piping Failuir Probabilities for Risk Categorization Failure Mechanism Methods for Estimating Probability Name of 3'

Mechanism Contributing Factors Failure Mode Stainless Steel Carbon Steels Other Materials Thermal Striping Crack Code Name Code Name Iligh Cycle Flow Induced Vibration Initiation Failure Fatigue Mechanical Vibration Crack Code Name Code Name.

Database-Growth Thermal Stratification Crack Code Name Code Name Low Cycle IIeat-up and Cool-down Initiation Failure Fatigue Thermal Cycling Crack Code Name Code Name Database Growth Coolant Chemistry

. Crack Code Not Corrosion Crevice Corrosion Initiation

'Name Applicable Failure Cracking Susceptible Material Database Iligh Stresses Crack Code Not h

(Residual, Springing)

Growth Name Applicable h

Flow Accelerated. Corrosion Wall Name of Name of Failure Wastage Microbiologically Ind. Corr.

Thinning Code Code Database -

Pitting and/or Wear Other Creep Damage Miscellaneous Failure Failure Failure Mechanisms Thermal Aging Modes Database Database Database Irrad. Embrittlement i

l

~l

REFERENCES 1.

USNRC,"Use of Probabilistic Risk Assessment 9.

USNRC, " Standard Review Plan for Risk-Methods in Nuclear Regulatory Activities; Final Informed Decision Making: Inservice Testing,"

Policy Statement," Federal Register, Vol. 60, p Standard Review Plan, NUREG-0800, Chapter 42622, August 16,1995.

3.9.7, August 1998.3

2. USNRC," Framework for Applying Probabilistic

10. USNRC, " Standard Review Plan for Risk-Risk Analysis in Reactor Regulation,"

Informed Decision Making: Technical Specifica-SECY-95-280, November 27,1995.1 tions," Standard Review Plan, NUREG-0800, Chapter 16.1, August 1998.3

3. USNRC," Standard Review Plan for the Review of Risk-Informed Insenvice Inspection of Piping,"

11. American Society of Mechanical Engineers," Case NUREG-0800, Section 3.9.8, September 1998.2 N-560, Alternative Examination Requirements for Class 1, Category B-J Piping WeldsSection XI,

4. USNRC, "An Approach for Using Probabilistic Division 1," August 9,1996.4 i

Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Current Licensing

12. American Society of Mechanical Engineers," Case i

Basis," Regulatory Guide 1.174, July 1998.2 N-577, Risk-Informed Requirements for Class 1, 2, and 3 Piping, Method A,Section XI, Divi-

5. USNRC,"An Approach for Plant-Specific, Risk-sion 1," September 2,1997.4 Informed Decisionmaking: Inservice Testing,,,

Regulatory Guide 1.175, August 1998.2

13. American Society of Mechanical Engineers," Case N-578, Riskinformed Requirements for Class 1, 6.

USNRC, "An Approach for Plant-Specific, Risk-2, and 3 Piping, Method B,Section XI, Divi-Informed Decisionmaking: Graded Quality Assur-sion 1," September 2,1997.4 ance," Regulatory Guide 1.176, August 1998.2

14. Electric Power Research Institute,"PSA Applica-

7. USNRC,"An Approach for Plant-Specific, Risk-tions Guide," EPRI TR-105396, August 1995.5 Informed Decisionmaking: Technical Specifica-tions," Regulatory Guide 1.177, August 1998.2

15. Electric Power Research Institute," Risk-Informed Inservice Inspection Evaluation Procedure," EPRI 8.

USNRC, " Standard Review Plan for Risk-TR-106706, June 1996.5 Informed Decision Making," Standard Review Plan, NUREG-0800, Chapter 19, July 1998.3

16. Westinghouse Energy Systems, " Westinghouse Owners Group Application of Risk Informed Methods to Piping Inservice Inspection Topical Copies are available for inspection or copying for a fee from the NRC 1

Public Document Room at 2120 L Street NW., Washington, DC; the Report," WCAP-14572, Revision 1, October PDR's mailing address is Mail Stop LL-6, Washington, DC 2uS55; 1997 3 telephone (202) 634-3273; fax (202) 634-3343.

Single copics of regulatory guides,both active and draft, and standard

17. Westinghouse Energy Systems, " Westinghouse 2

review plans may be obtained free of charge by writing the Reproduc-Structural Reliability and Risk Assessment tion and Distribution Scrvices Section,0CIO. USNRC, Washington, (SRRA) Model for Piping Risk-Informed laser-DC 20555-0001, or by tax to (301) 415-2289, or by e-mail to GRWl@NRC. GOV. Active guides may also be purchased from the vice Inspection," WCAP-14572, Revision 1, Sup-National Technical Information Service on a standing order basis.

plement 1, October 1997.1 Details on this service may be obtained by writing NTIS,5285 Port Royal Road, Springfield, VA 22161. Copies of active and draft guides

18. T.V. Vo et al., "A Pilot Application of Risk In-are available for inspection or copying for a fee from the NRC Pubhc Document Room at 2120 L Strect NW.. Washington.DC; the PDR's formed Methods To Establish Inservice Inspection mailmg address is Mail Stop LL-6, Washington, DC 20555; tele-Pn.onties for Nuclear Components at Surry Unit 1 phone (202) 634-3273; fax (202) 634-M43.

Nuclear Power Station," USNRC, NUREG/

3Copics are available at current rates from the U.S. Government CR-6181, Revision 1, February 1997.3 Printing Office, PO. Box 37082, Washington. DC 20402 -9328 (tele-phone (202) 512-2249);or from the National Technicallnformation Service by wnting NTIS at 5285 Port Royal Road, Springfield, VA 4 Copies may be obtained from the American Society of Mechanical 22161. Copies are available for inspection or copying for a fee from Engineers.345 East 47th Street, New York, NY 10017.

the NRC Public Document Room at 2120 LStreet NW., Washington, DC; the PDR's mailing address is Mail Stop LL-6, Washington, DC 5 Copies may be obtained from the EPRI Distribution Center,207 20555; telephone (202) 634-3273; fax (202) 634-3343.

Coggins Drive, PO. Box 23205, Pleasant mil, CA 94523.

I

(

1.178 - 22

19. American Society of Mechanical Engineers,

22. USNRC," Inservice Inspection Code Case Accept-

" Rules for Inservice Inspection of Nuclear Power ability, ASME Section XI, Division 1," Re Plant Components," ASME Boiler and Pressure Guide 1.147, Revision 11, October 1994.gulatory O

Vessel Code,Section XI,1989 Edition, New I

1 York *4

23. M.A. Meyer and J.A. Booker," Elicit.mg and Ana-D lyzing Expert Judgement," NUREG/CR-5424

20. USNRC," Design and Fabrica. Code Case Ac-(Prepared for the NRC by Los Alamos National ceptability, ASME Section 'II, Division I," Regu-Laboratory), USNRC, January 1990.3 latory Guide 1.84, Revision 30, October 1994.

24. J.P. Kotra et al.," Branch Techm. cal Position on the

21. USNRC, " Materials Code Case Acceptability, Use of Expert Elicitation in the High-Level Radio-ASME Section III, Division 1," Regulatory Guide active Waste Program," NUREG-1563, USNRC, 1.85, Revision 30, October 1994.2 November 1996.

REGULATORY ANALYSIS A draft regulatory analysis was published with the draft of this guide when it was published for public comment (Task DG-1063, October 1997). No changes g

were necessary, so a separate regulatory analysis for Regulatory Guide 1.178 has

(

not been prepared. A copy of the draft regulatory analysis is ava!!able for inspec-(

tion or copying for a fee in the NRC's Public Document Room at 2120 L Street NW., Washington, DC, under Task DG-1063.

1 1

0 1.178 - 23

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