ML11228A229
| ML11228A229 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom, Surry  |
| Issue date: | 12/17/2008 |
| From: | NRC/OCM |
| To: | |
| References | |
| FOIA/PA-2011-0083 | |
| Download: ML11228A229 (6) | |
Text
9 1ý OFýýL 11---ýR,'ýCý10ýNALý SOARCA Seismic Issue
-Ij Briefing for the Commissioners)
Technical Assistants Dec. 17 2008 J,
O N EýCf "ON'll!11,111" 11ýý 1
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Background===
Sequences for Peach Bottom and, Surry selected early 2007 - briefed ACRS July 2007
- ACRS in an October 2, 2008 public meeting identified a potential LERF seismic event for Surry from NUREG-1 150 SBO + LOCA + direct containment failure In NUREG-1 150, consequence analysis for this sequence was not reported because of a lack of quantification of non-nuclear seismic risks necessary for comparison. Performed as a sensitivity calculation in NUREG/CR
- Sequence originally screened out, qualitatively, by project Low frequency Lack of current plant specific quantification for fragility Lack of licensee analysis for identification / quantification First quantitative estimate in October at roughly.5x10-8, below our criterion, Recent quantitative reassessment using updated seismic hazard curve (but old fragility estimates) suggests this sequence has a frequency of
-2x10- 7 which meets screening criterion
- Questions remain on the state of quantification of theevent How do we address?
2
0 Path Forward Approach - exclude sequence from SOARCA analyses, acknowledge existence but defer to future resolution in separate project (development of better quantification is needed)
No delay in analyses Develop a separate seismic research program to address this long-standing issue Investigate the recent Japanese seismic experience at the Kashiwazaki-Kariwa nuclear power plant Develop seismic PRA guidance 3
Path Forward (cont)
- Advantages No delay Seismic event is poorly quantified
- Seismic hazard curve
" Fragility estimates Individual ACRS members consented GI-199 ongoing Near term resolution highly unlikely - much work needed (Plant specific detailed seismic modeling is ultimately required, reconciliation of Japanese seismic experience for US plants) - methods must be developed Consistent with current PRA treatment (event not identified in Surry or Peach Bottom IPEEE)
- No requirement for seismic PRA Consistent with SOARCA focus on mitigation - extreme seismicevent has little/no remedy Disadvantages Potential LERF event not analyzed Potential conflict with some stakeholders I
ALEL' ýCIS
ýNAL O MýAT 4
P ECI AL MATION Other approaches considered Address eventwith expedited and limited update of fragility and seismic
- Address event rigorously both seismic hazard and plant Ispecific fragility for LOCA and containment failure
- Assume worst case and calculate the consequences for the event AF 11 E
D ION INFO A
N5
Summary..
Identification of potential large seismic event does not diminish the overall SOARCA messages
- Sequences in the.10-5 to 10-7/reactor-year.range can be mitigated by SAMGs,,post-9/1 1. measures
- Releases from sequences, assuming no mitigation, are small and delayed Phenomena that resulted in large early release shown to be extremely unlikely.or unfeasible
- alpha-mode failure
- direct containment heating
- Releases from thermally induced steam generator tube rupture are small,' due to subsequent hot leg and lower head failure F 101 USE LY-EDEC 0
FORMATI 6