Streamlined RI-ISI

Patrick O’Regan

EPRI

poregan@epri.com

Introduction

• Background

• Streamlined RI-ISI Methodology

• Results

• Discussion, Lessons Learned, Improvements

• Summary

BackgroundGOAL:

Based upon the lessons learned from 50+ RI-ISI applications, develop a streamlined process for implementing and maintaining a RI-ISI program

But why?

Background

• Number of high safety significant (HSS) locations added by plant review – VY = zero BWR-N560– ANO-1 = zero B&W-N560– ANO-2 = zero CE – N578 (fullscope)– Fitzpatrick = zero BWR – N578 (fullscope)– South Texas 1 & 2 = zero West – N560

• Number of HSS locations added by NRC review – VY = zero– ANO-1 = zero– ANO-2 = zero– Fitzpatrick = zero– South Texas 1 & 2 = zero

Background

RI- Break Exclusion Requirements (HELB)

– EPRI TR-1006937

• Approved June 2002

• NRC Review

– Inspection population < 10 percent– Implementation via 50.59 procedure

– WCAP-14572, Addendum 1• Approved March 2004

• NRC Review

– Inspection population < 10 percent– Implementation via 50.59 procedure

Background

Code Case N663 “Alternative Surface Examination Requirements”

– Incorporates lessons learned from EPRI RI-ISI methodology and applications

– Eliminates many unnecessary examinations

– Reduces worker exposures

– Minimal analysis cost (as compared to typical RI-ISI applications)

– A number of plants approved to date

Background

Recent Experiences (RI-ISI Submittals)

– Results of Regulatory Reviews*

• Plant A – 70 locations added

• Plant B – 40 locations added

• Plant C – 40 locations added

• Plant D – 17 locations added

• Plant E – 13 locations added

* Reference - NEI 04-05

BackgroundRecent Experiences (cont.)

– RI-ISI Program Updates

• Plant A– PRA model updates

– Physical plant changes (e.g. power uprate, S/G replacement)

– No change in HSS

– No change in inspection program

• Plant B– PRA model updates

– Minor physical plant changes

– ~ 80 segments moved from Low to High/Medium

– ~ 30 segments moved from High to Low

Background

Recent Experiences (cont.)

– NEI 04-05 Update Review

• Four Plants Updated with:

– No changes to the RI-ISI selections / inspections

• Four Plants Updated with:

– Six exams eliminated and one added

– Twenty exams eliminated and five added

– Twenty eight exams eliminated and seven added

– Nineteen exams eliminated

Background

Summary - 1– Some applications approved with no changes required

– Some applications appear to be pushing the envelope (i.e. risk-

based versus risk-informed)

– Some applications experienced difficulty in gaining regulatory

approval (e.g. numerous RAIs, re-analysis, changes to program)

– Costs associated with program updates

– Updates may challenge initial program validity

Background

Summary - 2

– GOAL:

• Develop a consistent and streamlined process for

implementing and maintaining a RI-ISI program

– RESULT:

• Code Case N716; “Risk-Informed / Safety Based ISI”

(RIS_B)

Methodology

– ASME Whitepaper 2002-02-01

• Reviewed over fifty plant-specific RI-ISI applications,

• Thirty, of which, were Class 1 & 2 or fullscope applications

• Reviewed a number of industry and USNRC risk assessments

– Delta risk assessment conducted for eight plants• N716 (RIS_B) provides a risk reduction or at worst, risk neutrality

• Looked at BWRs and PWRs,

• Looked at plants that used the EPRI and West RI-ISI methods

• Does not credit the positive impact of 2(a)(5) (i.e. CDF > 1E-06)

Methodology

• High Safety Significant (HSS)– Reactor Coolant Pressure Boundary (e.g. Class 1)

– Shutdown Decay Heat Removal (out to containment / isolation)

– Break Exclusion Region (BER)

– Main Feedwater from S/Gs to BER

– Segments with > 1E-6 CDF (from internal flooding study)

• Low Safety Significant (LSS)– Remaining items (i.e.

• other Class 2,

• all Class 3,

• all NNS

Methodology

Treatment Criteria (PSI/ISI)• HSS population equal to 10%, plus augmented

programs

• HSS welds selected as follows:– 25 percent of the population identified as susceptible to each

degradation mechanism and degradation mechanism combination

– For the RCPB, at least two thirds of the examinations shall be located between the first isolation valve (i.e., isolation valve closest to the RPV) and the reactor pressure vessel.

– A minimum of ten percent of the welds in that portion of the RCPB that lies outside containment (e.g., portions of the main feedwater system in BWRs) shall be selected.

– A minimum of ten percent of the welds within the break exclusion region shall be selected.

Methodology

Additional Requirements

– Risk assessment of internal flooding events

(flooding, pipe whip, spray, etc.)

– Augmented inspection programs for FAC, IGSCC-

BWRs and localized corrosion (HSS & LSS Systems)

– Delta risk per EPRI TR-112657

Safety Significance Failure Potential Section XI Selections Case N-716 Selections

High Low DMs Rank Vol/Sur Sur Only RIS_B Other

RPV ���� LOCA TASCS, TT, (IGSCC) Medium (Medium) B-F 6 6 0 4 -

B-F 1 1 0 0 -

B-J 1 1 0 0 -

B-F 20 20 0 0 -

B-J 6 6 0 0 -

B-F 1 1 0 0 -

B-J 5 5 0 0 -

FW ���� LOCA TASCS, TT Medium B-J 60 18 0 9 -

FW ���� ILOCA TASCS, TT Medium B-J 10 8 2 7 -

FW ���� BER TASCS, TT Medium C-F-2 10 1 0 3 -

FW ���� ILOCA TASCS Medium B-J 4 0 4 4 -

FW ���� LOCA TT Medium B-J 3 2 0 3 -

FW ���� ILOCA None Low B-J 4 0 1 0 -

FW ���� BER None Low C-F-2 17 1 0 0 -

MS ���� LOCA None Low B-J 107 9 4 4 -

MS ���� ILOCA None Low B-J 64 8 34 0 -

MS ���� PLOCA None Low B-J 2 0 2 0 -

MS ���� BER None Low C-F-2 20 2 0 0 -

SD ���� LOCA None Low B-J 37 0 4 4 -

SD ���� ILOCA None Low B-J 4 0 0 0 -

SP ���� LOCA None Low B-J 5 0 0 1 -

RCR ���� LOCA None (IGSCC) Low (Medium) B-J 25 6 0 8 -

RCR ���� LOCA None Low B-J 161 38 4 12 -

RCR ���� PLOCA None Low B-J 8 0 4 0 -

CRD ���� Class 2 N/A Assume Medium C-F-2 63 5 0 0 -

SLC ���� LOCA None Low B-J 5 0 0 4 -

SLC ���� PLOCA None Low B-J 37 0 4 1 -

None (IGSCC) Low (Medium)

None Low

Code

Category

Weld

Count

TT, (IGSCC) Medium (Medium)

SystemBreak

Location

RPV LOCA

RPV LOCA

RPV LOCA

����

����

����

BWR - 1

Safety Significance Failure Potential Section XI Selections Case N-716 Selections

High Low DMs Rank Vol/Sur Sur Only RIS_B Other

RHR ���� BER TT, CC Medium C-F-2 4 0 0 1 -

RHR ���� BER TT Medium C-F-2 13 4 0 4 -

RHR ���� LOCA None Low B-J 24 8 0 7 -

RHR ���� PLOCA None Low B-J 55 10 0 1 -

RHR ���� BER None Low C-F-2 18 3 0 0 -

RHR ���� Class 2 N/A Assume Medium C-F-2 500 32 2 0 -

LPCS ���� LOCA None Low B-J 7 4 0 3 -

LPCS ���� PLOCA None Low B-J 25 4 0 1 -

LPCS ���� Class 2 N/A Assume Medium C-F-2 64 5 0 0 -

HPCS ���� LOCA TT Medium B-J 4 3 0 2 -

HPCS ���� LOCA None Low B-J 8 3 1 2 -

HPCS ���� PLOCA None Low B-J 30 2 0 1 -

HPCS ���� Class 2 N/A Assume Medium C-F-2 82 6 0 0 -

MSLC ���� ILOCA None Low B-J 31 0 1 4 -

FWLC ���� PLOCA None Low B-J 11 0 0 2 -

RCIC ���� LOCA None Low B-J 7 0 0 2 -

RCIC ���� PLOCA None Low B-J 5 0 0 1 -

RCIC ���� BER None Low C-F-2 12 5 0 0 -

RCIC ���� Class 2 N/A Assume Medium C-F-2 107 4 0 0 -

C-F-1 3 3 0 0 -

C-F-2 5 0 0 0 -

RWCU ���� LOCA None Low B-J 65 11 1 10 -

RWCU ���� ILOCA None Low B-J 25 8 0 2 -

B-J 4 0 0 0 -

C-F-2 22 2 0 0 -

Class 3 11 0 0 2 -

Other 1 0 0 0 -

RWCU ���� Class 2 None Low B-J 3 0 0 0 -

RWCU ���� Class 2 N/A Assume Medium C-F-2 2 0 0 0 -

N/A Assume MediumCGC ���� Class 2

Code

Category

Weld

CountSystem

Break

Location

None LowRWCU ���� BER

BWR - 2

Safety Significance Failure Potential Section XI Selections Case N-716 Selections

High Low DMs Rank Vol/Sur Sur Only RIS_B Other

RC ���� LOCA TASCS, TT Medium B-J 6 3 0 2 −

RC ���� LOCA TT, PWSCC Medium B-F 1 1 0 1 −

RC ���� LOCA TASCS Medium B-J 12 2 2 3 −

RC ���� LOCA TT Medium B-J 2 0 0 1 −

RC ���� LOCA PWSCC Medium B-F 9 9 0 9 −

B-F 12 12 0 4 −

B-J 609 48 111 47 −

RC ���� PLOCA None Low B-J 11 0 3 0 −

CS ���� LOCA TT Medium B-J 28 0 5 7 −

CS ���� ILOCA TT Medium B-J 2 0 0 0 −

CS ���� PLOCA TT Medium B-J 2 0 1 0 −

CS ���� LOCA None Low B-J 16 0 7 0 −

CS ���� PLOCA None Low B-J 22 0 5 0 −

CS ���� Class 2 LSS N/A Assume Medium C-F-1 239 11 3 0 −

RH ���� LOCA None Low B-J 3 1 0 2 −

RH ���� PLOCA None Low B-J 19 5 0 3 −

RH ���� Class 2 SDC − IC None Low C-F-1 26 4 0 0 −

RH ���� Class 2 LSS N/A Assume Medium C-F-1 282 12 0 0 −

SI ���� PLOCA IGSCC Medium B-J 47 13 2 14 −

SI ���� LOCA None Low B-J 32 5 6 8 −

SI ���� PLOCA None Low B-J 232 38 33 4 −

SI ���� PILOCA − OC None Low B-J 9 0 2 2 −

SI ���� PILOCA − IC None Low B-J 122 0 21 17 −

SI ���� Class 2 LSS N/A Assume Medium C-F-1 586 71 0 0 −

FW ���� Class 2 FWU − IC TASCS Medium C-F-2 8 5 0 2 −

FW ���� Class 2 FWU − OC None Low C-F-2 97 7 0 4 −

FW ���� Class 2 FWU - IC None Low C-F-2 46 3 0 0 −

FW ���� Class 2 FWI − OC None Low C-F-2 63 4 0 16 −

MS ���� Class 2 LSS N/A Assume Medium C-F-2 218 16 0 0 −

CTS ���� Class 2 LSS N/A Assume Medium C-F-1 165 14 0 0 −

System Break Location

RC ���� LOCA None Low

Code

CategoryWeld Count

Lessons LearnedPilot plants

– Application of approved RI-BER process results in inspection

populations below 10 percent [RIS_B sets floor at 10 percent]

– Application of approved RI-ISI for the RCPB results in inspection

populations below 10 percent [RIS_B sets floor at 10 percent]

– 2(a)(5) Requirement:

• Plant 1 – internal flooding study did not identify piping > 1E-06

• Plant 2 – plant made procedural/ hardware changes to reduce CDF

to < 1E-06

• Plant 3 - updated analysis to remove excessive conservatism to

reduce CDF contribution to < 1 E-06

• Added criterion for LERF > 1 E-07

Lessons LearnedIndustry Application

– 40 Units have applied the streamlined RI-ISI methodology and fall into four categories

• Plants that do not identify any safety significant (HSS) piping outside the pre-defined scope

• Plants that initially identify Class 3 or non safety related piping as HSS but conduct additional / more realistic analyses

• Plants that identify HSS piping in Class 3 or non safety related system and plant modification to eliminate to issue

• Plants that identify HSS piping in Class 3 or non safety related piping that conduct NDE on subject piping

Considerations for application

– Materials and operating conditions are factors in determining applicable degradation mechanism and susceptibility criteria

– Current inspection program/philosophy

– Periodic based ISI (e.g. deterministic rules)

– Operating experience based ISI (e.g. local corrosion, flow accelerated corrosion)

– Risk assessment of internal flooding events important in identify plant specific HSS piping, if any

– Systems that support multiple units may require additional thought

– System failures that could impact multiple units may require additional thought

Summary– Founded upon previously conducted Risk-informed work:

• Deterministic approaches

• Qualitative risk approaches

• Quantitative risk approaches (e.g. WCAP-14572, EPRI TR-112657, EPRI TR-1006937, N663, international experience)

– Uses generic insights to:

• Reduce cost of implementation and maintenance

• Assure defense in depth is maintained (e.g. high consequence sites)

– Uses plant-specific insights to:

• Assure important plant specific inspections are conducted

• Maintain or improve pressure boundary reliability (e.g. degradation mechanisms)

– Requirement for augmented programs for PWSCC, IGSCC, FAC, LC

– Requires and cost-effectively performs a full plant evaluation (safety related and non

safety related systems)