ML20247J114
| ML20247J114 | |
| Person / Time | |
|---|---|
| Issue date: | 09/14/1989 |
| From: | Shao L NRC - EXTERNAL EVENTS STEERING GROUP |
| To: | Houston R, Novak T, Richardson J NRC - EXTERNAL EVENTS STEERING GROUP |
| References | |
| NUDOCS 8909200198 | |
| Download: ML20247J114 (4) | |
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$EP 14 29 MEMORANDUM FOR: External Events Steering Group Members R. W. Houston T. M. Novak
{
J. E. Richardson G. Bagchi., Executive Secretary 1
- FROM:
.L. C. Shao, Chairman
)
External Events Steering Group
SUBJECT:
SUMMARY
OF JULY 20, 1989 MEETING WITH NUMARC
' On July 20, 1989, theExternalEventsSteeringGroup(EESG)metwiththeir Seismic Subcommittee and representatives from NUMARC. The purpose of the meeting was to discuss seismic issues related to individual plant examinations for external events (IPEEE.
. After. an introduction by all attendees (Enclosure 1), Mr. Shao stated that the purpose of the meeting was to provide the NUMARC staff and their representatives with a summary of NRC activities associated with IPEEE guideline development.
In turn, the steering group and subcommittee would like to be updated on related NUMARC activities, particularly, industry proposed programs to address high frequency seismic motions, and to determine the review level earthquake associated with seismic design margins evaluations.
Mr. Shao described a related issue that the subcommittee and steering group is addressing. Namely, what hazard curves, NRC sponsored or EPRI sponsored, should be used in seismic PRAs? The availability of two hazard curves has the potential of causing problems during staff review of IPEEE submittals.
Mr. Houston added that the concept of Severe Accident Policy implementatica and. individual plant examinations may be tied to license renewals. Thus, the thely resolution of' seismic issues is very important.
Dr. Leon Reiter, Seismic Subcommittee Co-Chairman, briefly described subcommittee technical assistance activities related to seismic IPEEE guidance development (Enclosure 2). Contractor efforts to help the staff determine the
-review level earthquake have been:
(a) a comparison of NUREG/CR-0098 spectra (anchored at 0.3g) to multiples of the plants safe shutdown earthquake (SSE);
(b) an evaluation if the seismic margins methodology is applicable for L
earthquake magnitudes greater than 6.5; (c) an evaluation of the variability uncertainty);(d)pectraofearthquaketimehistories(spectralshapea review of th in the response s (e).an evaluation to determine if there is a correlation between plant HCLPF and core melt.
Efforts to extend the seismic margins methodology to include containment performance and provide risk insights for cost-benefit studies OF05 8909200198 890914 if l PDR REVGP NRCEXTER PNU
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I $ WC were discussed as well as miscellaneous topics on liquefaction, relay chatter, and integration of seismic issues. Dr. Reiter closed his presentation by noting that the contractor reports are draft and not available outside the staff except the magnitude-duration study and the high frequency study which will be given to NUMARC for distribution.
Mr. James Whiteraft, NUMARC, gave a brief overview of their perspective on IPEEEs and Severe Accident Policy implementation. Basically, HUMARC is starting with the concept that all operating plants are safe and the key effort is to find vulnerabilities. He suggested it may be possible to satisfy the policy statement without extensive investigations at all plants. NUMARC and industry will balk at doing extensive investigations; for example, margins evaluations, just for the sake of doing it.
If they are necessary they will be done. Mr. Whiteraft pointed out that plants have spent $300K apiece for the SQUG program; an additional $500K to $750K is anticipated for SQUG implemen-tation and $250K for a seismic design margins evaluation. Mr. Whiteraf t stated i
that the programs that will be described by Drs. Reed, Sewell and McGuire are still being developed and are being presented to the staff to get their initial reaction. -The final program will be available around September 15.
Dr. John Reed described the proposed industry program (EPRI) to address high-frequency ground motions (Enclosure 3). The program has three major areas; analysis of high-frequency seismic effects (assuming that equipment remains ductile); develop a simplified procedure for calculating floor response spectra, and shake table testing. Analytical investigations to be completed in mid 1990, and testing results by early 1991. An interim basis is recommended until EPRI project is completed.
Key interim recommendations include:
If seismic margin ground response spectrum (review level earthquake) a.
is less than SSE design response spectrum, then only do seismic walkdown to verify no vulnerabilities exist.
b.
Seismic margin screening tables can be related to the following 5%
damped spectral accelerations.
=
=
Other recommendations and related figures are provided in Enclosure 3.
Dr. Reed explained that the bases for the interim recommendations are judgment consistent with that used in the development of the original seismic margin screening tables, A-46 experience in developing screening guidelines and bounding spectrum, and earthquake experience which shows low-frequency motions
(<10Hz)arerequiredtocausedamagetonuclearplanttypeequipment.
Following a brief introduction by Dr. Robin McGuire, Dr. Rcbert Sewell described the proposed industry program to determine the review level earthquake motion for seismic design margins evaluations (Enclosure 4). The
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ft industry program is based on the assumption that the review level earthquake should be consistent with an acceptable seismic fraction of the NRC Safety Goal. After describing the proposed method of determining the review level earthquake (RLE) Dr. Sewell presented the following " graded approach" for the
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resolution of seismic concerns related to the IPEEE:
j RLE <1.25 SSE No Action RLEN 1.25 SSE Perform Seismic Margins Evaluation Dr. Sewell also stated that an A-46 evaluation would be performed regardless of RLE value. Further alternative gradation could also be based on a seismic safety goal fraction b,; seismic) at a RLE equal to, e.g., the SSE.
The staff pointed out that the NRC's Policy Statement on Safety Goals does not contain a numerical value that can be used as a figure-of-merit for core damage. The Safety Goal explicitly states one of its objectives as:
"providing reasonable assurance, giving consideration to the uncertainties involved, that a core-damage accident will not occur at a U.S. nuclear power plant."
In addition, the staff also indicated that the Safety Goal provides targets for generic regulatory requirements and not criteria for individual licensing decisions.
The subcommittee stated they were concerned about the "No Action" criteria explaining it may not meet the intent of the Severe Accident Policy Statement to find plant vulnerabilities. Lessons learned from past seismic PRA plant walkdowns have demonstrated that cost effective upgrades to enhance plant capacity have been made even when SSE criterion are met.
Further, the subcommittee advised the presenters that both Livermore and EPRI hazard curves should be considered when developing criteria to determine the review level earthquake.
During the meeting wrapup Mr. Bagchi, EESG executive secretary, informed the EESG, Seismic Subcommittee and NUMARC representation of an upcoming ACRS meeting on IPEEE. The date is September 6, 1989; it will be an all day meeting. The ACRS wants presentations from the staff and NUMARC. Mr. Bagchi will be working with appropriate people to develop an agenda.
(Note: Agenda developed and meeting held. Presentations made by NRC staff only).
L. C.
hao, Chairman External Events Steering Group
Enclosures:
As stated cc: Meeting Attendees DISTRIBUTION: RESReading -DCS R-2411 RKenneally DGuzy AMurphy RBosnak LShao GBagchi LShao P
- See previous page for concurrences SSEB/DE/RES NRR RKenneally* GBagchi*
S 9/14/89 9/14/89 9//p'/89
+
s
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l-N industry program'is based on the assumption that the review level earthquake I
should be consistent with an acceptable seismic fraction of the NRC Safety
{
Goal. 'After describing the proposed method of determining the review level i
earthquake (RLS Dr. Sewell presented the following " graded approach" for the resolution of seismic concerns related to the IPEEE:
RLE <1.25 SSE No Action RLE71.25 SSE Perform Seismic Margins Evaluation Dr. Sewell also stated that an A-46 evaluation would be performed regardless a
t of RLE value. Further, alternative gradation could also be based on a seismic safety goal fraction (p(seismic) at a RLE equal to, e.g., the SSE.
The staff pointed out that the NRC's Policy Statement on Safety Goals does not I
contain a numerical value that can be used as a figure-of-merit for core j
damage. The Safety Goal explicitly states one of its objectives as:
"providing reasonable assurance, giving consideration to the i
uncertainties involved, that a core-damage accident will not occur at a U.S. nuclear power plant."
In addition, the staff also indicated that the Safety Goal provides targets for generic regulatory requirements and not criteria for individual licensing I
decisions.
l The subcommittee stated they were concerned about the "No Action" criteria explaining it may not meet the intent of the Severe Accident Policy Statement to find plant vulnerabilities. Lessons learned from past seismic PRA pisnt walkdowns have demonstrated that cost effective upgrades to enhance plant capacity have been made even when SSE criterion are met. Further, the subcommittee advised the presenters that both Livermore and EPRI hazard curves
)
should be considered when developing criteria to determine the review level earthquake.
During the meeting wrapup Mr. Bagchi EESG executive secretary, informed the EESG, Seismic Subcommittee and NUMARC representation of an upcoming ACRS meeting on IPEEE. The date is September 6,1989; it will be an all day meeting. The ACRS wants presentations from the staff and NUMARC. Mr. Bagchi i
will be working with appropriate people to develop an agenda.
L. C. Shao, Chairman External Events Steering Group
Enclosures:
As stated cc: Meeting Attendees DISTRIBUTION: RESReading DCS R-2411 RKenneally DGuzy AMurphy RBosnak LShao GBagchi LShao PDR SSEB/DE/RES NR D:DE/RES RKenneally LShao 9
9/
/89 9/ /89 l
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