ML20235M564
| ML20235M564 | |
| Person / Time | |
|---|---|
| Issue date: | 02/13/1989 |
| From: | Shao L NRC - EXTERNAL EVENTS STEERING GROUP |
| To: | Arlotto G, Houston R, Novak T NRC - EXTERNAL EVENTS STEERING GROUP |
| References | |
| NUDOCS 8902280323 | |
| Download: ML20235M564 (28) | |
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t'EMORANDUl? FOR:
Externa'l Events Steering Group Members:
G.'A..Arlotto
^
R.'W. Houston-T. M. Novak G. Bagchi, Executive Secretary FROM:
L. C. Shao,'Chairnan External Events Steering Group
-SUPJECT:
SUMMAPY OF JANUARY 24, 1989 MEETING WITH NUMARC-
- 0n Janucry 24, 1989', the Evternal. Events Steering' Group (EESG) met with their
.Scismic Subconnittee and representatives from NUMARC. The purpose of the meet-
'inE was to discuss seismic issues related to individual plant examination (IPE)
^
'for severe accidentr..
After an" introduction by all attendees (Enclosure 1), Mr.- Arlotto stated that the purpose'of the meeting was'to inform'the NUMARC staff and-their represen-
,tatives of Seismic Subcommittee progress i_n developing guidelines for seismic related IPEs.
In turn,.the' steering group and subcommittee would like-to be updated on related NUMARC activities. Mr. Arlotto pointed out that the NRC
' does-not-have rigorously defined positions on seismic IPEEEs. He concluded.by describ!ino the presentations that A. Murphy, Seismic Subcommittee Co-Chairman, L f!. Chokshi and J. Chen would be making..
A' copy of the' vugraphs' used by' A. Murphy, N. Chokshi, and J. Chen are included.
as Enclosure 2.
Highlights of the presentations and related discussions are given below.
o'.
SEISMIC'TPEEE - Proposed Basic Approach (A. Murphy)
~ Thc? subcommittee has developed two statements of work (S0W) for-contractor assistance in developing seismic related IPE guidelines.
The contractors are the Lawrence Livermore National Laboratory (LLNL) and the'Sandia National Laboratories (SNL). Copies of the S0W will'be provided to NUMARC once contractual procedures are
.conpleted.
Following the precedence established for internal event analyses, the Seismic Subcommittee is not explicitly defining the tern vulnerability.
In conjunction with seismic design margin evaluations, the sub-committee recommends that structures and components with seismic capacities less than the review level earthquake should be reported
.to the NRC'.
However, this reporting does not necessarily identify
'the structure or component as a vulnerability.
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The staff will use the backfit rule (10 CFR 50.109) to require 1
modifications beyond those volunteered by the utility.
.o Review Level Issues ( A.11urphy)
The subconnittee is presently considering a generic review level for 1
plants located in the Central and Eastern U.S.
The review level relates to the screening tables used in. conjunction with.the seismic design margin methodology. Plants located in the Western U.S. will use site specific review levels.
The spectra from new ground motion models paining acceptance by the earth science community. are showing more high frequency input than spectre ured in the development of the seismic design. margins methodology. (1411 REG /CR-0098).
Another concern related to ground mo-tion is that the seismic design margins methodology assumes a magni-tude 6.5 earthouake; is there a problem applying this methodology to higher ragnitude earthquakes?
o Risk Insights ( A. Murphy)
The subconnittee is concerned if one can one obtain risk' insights frnm the. seismic design margins methodology; will they be com-patible with these obtained from internal events analyses?
Consultants to the Seismic Subcommittee have stated that obtaining-risk insights using-seismic design methodologies may be easier with the LLNL developed methodology over the one developed by EPRI.
ftr. Arlotto asl:ed if this point had been discussed with EPRI staff and do they agree.
It nay be necessary for the technical staff to get together and discuss this in more detail.
Containment Performance (fl. Chokshi) 01 Contractor efforts related to containment performance described in
. should be completed in May 1989.
One problem in evaluating containment performance as an initiator or nitigation system is the ability to do an adequate walkdown, e.g.,
physical location of spray systems make them hard to examine, con-tainment access limited to periods of plant shutdown, o
Integration Plan (J. Chen) i Staff is concerned and trying to avoid a duplication of effort re-lative to internal and external events analyses; also other seismic related activities, e.g., external events and USI A-46 resolution.
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3 Generic Letter flo. 88-20 reminds the licensees and applicants that the external event analyses is proceeding on a' schedule'different from the internal events analyses. Documentation and retention of relevert data for'use in external events' analyses is recommended.
Draft external event guidance is due to the staff in May,'~ final cuidance is' due in the Fall.
Trial Plant Reviews seismic has had several, both PRA and margins methodologies o
,(NRC and EPRI);
o fire will use the Brunswick plant
-o high wind and flood - none planned.
Ruble Thomas reconrended a plant review for the high wind and flood methodology to ensure th6 staff fully understands the implications of its recommendations.
Following' the stafi presentation, !!UMARC staff presented their' efforts in ad-
- dressino seisr,ic related IPEs.
W. Lindblad stated how pleased he was that NRC and NUMARC had parallel objectives. W..Rasin stated that an important NUMARC concern is understanding what industry is trying to do relative to IPEs.. ls L
there a mutual understanding of terms, objectives and methodologies between
.NRC staff and industry?
J. 'Whiteraf t followed with a summary of the NUl1 ARC program.
Vugraphs are included as Enclosure 3, highlights of the presentation and related discussions are given below.
The three tasks in the flV!1 ARC program for seismic Severe Accident Policy resciution are:
l o.
Establish Basis for Investigation Objectives o.
Extend Seismic l'argin fiethodology o
Develop Basis for Establishing Review Level Ground Motion-L. Reiter asked why NUMARC was developing an industry perspective of Severe l
i Accident Policy objectives, is it because there is not enouah guidance in the documents issued?
J. Whitcraft answered by stating that terms like vulner-ability and outlier are not defined.
W. Rasin added he is not sure if the staff. is locking for evtliers or residual risk.
NUMARC's schedule for completion of its tasks.is:
o Objectives 6/30/89 o
Extend Seismic Margins 9/1/89 o
Review Level Ground Motion 9/1/89 l
l.
L. Shao noted and W. Rasin agreed that there is quite a disparity between the NRC and NUMARC schedules.
L. Shao went on to say that the NRC would like to neet its schedule.
NUf1 ARC was urged to compress its schedule so as to allow timely considerations of its reports.
L
4
/t the meetings conclusion, G. Ariotto commented that high level management reetings r.' this type are extrenely important. However, it is time for the technical staff to meet and discuss perceived differences or concerns in the different methodologies.
For example, NUMARC and flRC staff shoui' get together t6 discuss differences in review level earthquake or the ease of obtaining ritk insights from EPRI vs i:RC seismic design margin methodologies. He recom-mended that such reetings be arranged.
/
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'. C. Shao,' Chairman External Events Steering Group
Enclosures:
1.
Atterices Jan. 7/;.1989 lieetino T.
Vugraphs - A. Iturphy, fl. Chokshi, and J. Chen 3.
Vugraphs - J. Whitcrrft, t!UMARC Fi tributiot List:
See ettached sheet t
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W. Lindblad, NUMARC DISTRIBUTION J. Whiteraft, NUMARC U CEcFjord,'RES W. Matevia, Yankee D. Ross, RES J. C. Stepp, EPRI E. Jordan, AEOD A. Machiels, EPRI W. fiinners, RES E. Fotopoulos, Bechtel R. Besna k, RES F. Rahn, EPRI C. T hora s, lip R -
M. Hayner, NUMARC J. E. Richardson, NRR J. George NUMARC F. J. Itiraglir.,I;PR R. Thomas, NUMARC W. Beckner. PES R. Huston, NUMARC J. liitchell, RES W. Rasin, NUMARC A. J.11urphy, RES L. Re'ter. I1PF J..Chen, RES l1. Chokshi, PES D. Jerp, NRR G. Kelly, I;f:l R. Kenneally, PES T. Y. Chang, RES R. Rothman, imD E. Throm, RES' D. Guzy, R PRC PDP
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Enclosure 2
SEISMIC IPEE-PROPOSED BASIC APPROACH o
EVALUATE PLANTS SEISMIC CAPACITIES TO TDENTIFY VULNERABILITIES TO EARTHOUAKE INDUCED ACCIDENTS, o
DETERMINE HCLPF AS COMPARED TO A REVIEW LEVEL EARTH 0VAKE, o
REVIEW LEVEL EARTHOUAKE HIGH EN0 UGH TO CHALLENGE PLANT UNCOVER VULNERABILITIES, IF ANY LOW EN0llGH TO MINIMlZE SCOPE o
REVIEW LEVEL MAY BE GENERIC F0P MOST CENTRAL AND EARTERN U.S. PLANTS, o
REVIEW LEVEL MAY BE SITE-SPECIFIC FOR WESTERN U.S. PLANTS, n
ACCEPTABLE METHODS:
SEISMIC PRA SEISMIC DESIGN MARGINS PROGRAF (NRC OR EPRI) o COPRECTION OF VilLNERABILITIES IN F?NTEXT OF OTHER BACKFITS,
~
REVIFW LEVFL ISSilES o
HIGH FREQUENCY PROBLEM FOR STANDARDIZED GR0llND-MOTION
- SPECTRA, o
LIMITATIONS OF EARTHOUAKE SIZE IN SDMP, o
RELATIONSHIP OF PLANT HCLPF TO HAZARD AND CORE DAMAGE, CONTAINMENT PERFORMANCE o
NOT INCLUDED IN SDMP o
CAN BE EXTENDED USING PRA INSIGHT, 0
ACCESS PROBLEM IN WALKDOWN, o
MARK 1 AND ICE CDNDENSER NEEDS SPECIAL ATTENTION.
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RISK TNSIGHTS
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l o
NEEDED FOR TPEEE, NOT-lN SOMP, l
0 ONGOING STUDIES SHOWING FEASIBILITY OF GAINING INSIGHTS INTO:
CORE DAMAGE 4
l PLANT DAMAGE STATES o
OUAb'TTTATTVE RAD 10 LOG 1 CAL CONSEQUENCES F0P, COST /RENEFTT MAY BE INFEASIBLE, o
RISK INSIGHTS FROM EPRI SDMP MAY BE MORE DIFFICllLT.
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- LfCENSEES SHOULD CONDUCT SYSTEMATIC EXAMINATION OF PLANT DESIGN, OPERATION,~
- MAINTENANCE AND EMERGENCY OPERATION TO:
- IDENTIFY PLANT SPECIFIC VULNERABILITIES (DESIGN AND PROCEDURAL) TO SEVERE ACCIDENTS (FOR BOTH CORE DAMAGE AND CONTAINMENT PERFORMANCE); BOTH INTERNAL AND EXTERNAL INITIATORS ARE TO BE CONSIDERED.
EXTERNAL INITIATORS WILL BE CONSIDERED SEPARATE FROM THE IPEs AND ON A LATER SCHEDULE
- UNDERSTAND THE SEQUENCES THAT CONTRIBUTE THE MOST TO THE TOTAL CORE DAMAGE OR TO POOR CONTAINMENT PERFORMANCE
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CONTAINMENT PERFORMANCE 1,
C0taAlhMENT AS AN INITIATOR OF CORE DAMAGE SEQUENCES 2.
CONTAINMENT AS POST ACCIDENT MITIGATING SYSTEM FACTORS:
CONTAINMENT TYPES:
MARK 1, 11, Ill, ICE CONDENSER, LARGE-DRY, ETC.
1 STEEL VS, CONCRETE EARLY FAILURE VS. LATE FAILURE HlGH HCLPF PLANT VS, LOW HCLPF PLANT i
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I CONTAINMENT AS AN INITIATOR MARGIN METHODOLOGY ASSUMPTIONS REGARDING CONTAINMENT FUNCTIONAL i
SCREENING.
I 1
FOR PWRS: CONTAINMENT HEAT REMOVAL AND OVERPRESSURE PROTECTION (EARLY OR LATE) PART OF FUNCTIONAL GROUP B - ASSUME FAILURE IF FAILURE OF FUNCTIONAL GROUP A - NO MARGIN EVALUATION REQUIRED.
ERRORS RESULTING FROM"THESE ASSUMPTIONS ARE DISCUSSED AS BELOW.
Type I Error - This error involves seismic core melt sequences which would result from the success of Group A functions and i
failure of Group
.B functions.
These sequences will be missed, since the core melt is caused by failure of _ Group B arid thq screening insight assumes that if_Jrgup A succeeds then_ Group B s ucc_,eed ry which is a non-core melt. This type of error would obviously be non-conservative.
Type II Error - This error involves seismic core melt sequences
. hich result from failure of Group A functions but which are w
followed by success of Group B
containment protection functions.
These sequences would not be entirely missed since the core melt results from failure of Group A,
which the screening insight would find.
,However,, they would erroneously be considered to have included failure of-all the fu'nctions of Group B since the screening insight implies that success of i
the functions of Group B is not probable given f ailure of Group A.
This type of error would be conservative, since these Group A failure / Group B success sequences would be placed into Group A failure / Group B f ailure plant damage states, which have bigher consequences.
I CONCLUSION IN MARGIN METHODOLOGY - MISSING SEQUENCES CAUSED BY
)
GROUP B FL'NCTIONS LEAD TO MEASURABLE BUT UNIMPORTANT UNDERESTIMATION OF CORE MELT FREQUENCY.
Table 4-13 Functions Requiring Detailed Evaluations in Seismic Margins Reviews
'jGnctiEn Screening Requirement Remarks inltiators:
bifsite Power F
F= Assume Failure RCS Integrity (LOCA)
I Containment Integrity X
Functional Group A:
Eeactor Suberiticality I
X= Margin evaluation Normal Shutdown F
for all potential i
Emerg. Core Cooling (Early)
X failure modes is required.
runctional Group B:
Emers. Core Cooling (Late)
A A= Assume failure if Containment Heat Removal A
core melt occurs Cont.Ove rp re s. Pro t.
(Early)
A resulting from failure Cont.Overp res. Prot. (Late)
A of Functional Group A, assume successful if functional Group A is successful in pre-venting core melt.
Conditional on plant waikdown not finding any extremely gross plant-specific j
differences
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-CONTAINMENT AS' MITIGATION SYSTEM
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CONTAINMENT OVERPRESSURE / TEMPERATURE CHAli.FNGES:
A.
SEISMIC' INDUCED STRUCTURAL DEGRADATION B.-
SEISMIC VULNERABILITIES OF POST ACCIDENT. HEAT REMOVAL.
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AND COMBUSTIBLE GAS CONTROL SYSTEMS C.
SEISMIC VULNERABILITIES OF SUPPRESSION SYSTEMS 2.
CONTAINMENT BYPASS
- A, INTERFACING SYSTEM LOCA B.
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SEISMIC VULNERABILITIES OF CONTAINMENT ISOLATION SYSTEM o
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CllRPENT RESEARCH EFFORTS (1) DEVELOPE MOPE SPECIFIC GUIDANCE ON MARK I C0tRAINFENT FUNCTIONSTOBE INCLUDED IN MARGIN REVIEW, (2) REVIEW PAST Ato CURRENT PRAs TO IDEt,TIFY CONTAINMENT SYSTEMS / COMPONENTS NEEDED FROM BOTH, EARLY AND LATE FAILURE PERSPECTIVES, l
(3) DEVELOPE FRAGILITY SCREENING GUIDELINES FOR COMPONENTS IDENTIFIED IN (2),
l (4)
INVESTIGATE POSSIBILm' 0F USING HIGHER REVIEW LEVEL FOR MITIGATION I
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Enclosure.
3
~
NRC/NUMARC MEETING JANUARY 24, 1989 NUMARC SEISMIC ISSUES WORKING GROUP SEISMIC SEVERE ACCIDENT POLICY APPROACH TO RESOLUTION I
O SEISMIC SEVERE ACCIDENT POLICY RESOLUTION TASKS ESTABLISH BASIS FOR INVESTIGATION OBJECTIVES EXTEND SEISMIC MARGIN METHODOLOGY DEVELOP BASIS FOR ESTABLISHING REVIEW LEVEL GROUND MOTION l
l
1 i
SEISMIC SEVERE ACCIDENT POLICY RESOLUTION ESTABLISH POLICY OBJECTIVES INDUSTRY WILL DEVELOP ITS PERSPECTIVE OF THE SEVERE ACCIDENT POLICY OBJECTIVES DEFINITION OF OBJECTIVES IS NEEDED TO:
0
-ESTABLISH THE FOCUS OF EFFORT 0
MAXIMIZE USE OF RESOURCES 0
PROVIDE A MEASURE AGAINST PROGRESS 0
PROVIDE A BASIS FOR CLOSURE 1
i SEISMIC SEVERE ACCIDENT POLICY RESOLUTION ESTABLISH POLICY OBJECTIVES EVALUATE BASIS FOR OBJECTIVES 0
PLANT CAPACITY STUDY 0
ULTIMATE CAPACITIES NEED NOT BE IDENTIFIED 0-COST-BENEFIT CONSIDERATIONS 0
CONSISTENCY AMONG INITIATORS IMPLEMENTATION 0
EVALUATE ALTERNATIVES AVAILABLE TO MEET OBJECTIVES 0
INVESTIGATE CRUCIAL CONSTRAINTS 0
SEISMIC MARGINS VS PRA 0
DEVELOP GENERIC APPROACH FOR IMPLEMENTATION
l SEISMIC SEVERE ACCIDENT POLICY RESOLUTION EXTEND SEISMIC MARGIN METHODOLOGY APPROACH:
0 DETERMINE EXTENSION NEEDED TO COVER SEVERE i
ACCIDENT ISSUES 0
INVESTIGATE CRUCIAL CONSTRAINTS EPRI METHOD:
0 REVIEW LEVEL GROUND MOTION 0
DETERMINE SUCCESS PATHS 0
SCREEN SYSTEMS AND STRUCTURES 0
EVALUATE OUTLIERS EPRI METHODOLOGY INCLUDES LIQUEFACTION, DECAY HEAT REMOVAL AND RELAY CHATTER
--a._--_
.. ~
SEISMIC SEVERE ACCIDENT POLICY RESOLUTION BASIS FOR ESTABLISHING REVIEW LEVEL GROUND MOTION ESTABLISH CRITERIA FOR ACCEPTANCE 0
TO DEMONSTRATE AN ADEQUATE MARGIN 1
EVALUATE ALTERNATIVE APPROACHES CONSIDERING 0
CURRENT GE0 TECHNICAL SCIENCE 0
EXPERIENCE DATA 0
DETERMINISTIC, PROBABILISTIC OR COMBINATION 0
REGULATORY CONSTRAINTS 0
ANALYTICAL CONSEQUENCES DEVELOP A FINAL METHOD m.
m..__._-
m
--_.--.______,m__m.
m.m_
_.J
.. ~
SEISMIC. SEVERE ACCIDENT POLICY RESOLUTION SCHEDULE i
OBJECTIVES 30 JUNE 1989 EXTEND SEISMIC MARGINS 1 SEPTEMBER 1989 REVIEW LEVEL GROUND MOTION 1 SEPTEMBER 1989 i
i