ML18040A935
| ML18040A935 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 06/28/1989 |
| From: | Thadani M Office of Nuclear Reactor Regulation |
| To: | Varga S NRC |
| Shared Package | |
| ML17156B270 | List: |
| References | |
| NUDOCS 8907060093 | |
| Download: ML18040A935 (4) | |
Text
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UNI7CD STATES UCLEAR REGULATORY COMMISSI WASHINOTON, D..lr 25555 June 28, 1989 NOTE TO:
Steven A. Varga THROUGH:
Halter R. Butler FROM:
Mohan C. Thadanf
SUBJECT:
SUMMARY
OF JUNE 22, 1989 MEETING MITH PENNSYLVANIA POMER AND LIGHT COMPANY On June 22, 1989, PennsyIvania Power and Light Company (PPSL) met with the NRC staff and presented a briefing on its methodology for evaluation of severe accident risks at Susquehanna Steam Electric Station, Units 1 and 2.
A copy of PPSL's briefing viewgraphs and a list of attendees are enclosed.
Two previous meetings on PPSL's severe accident evaluation program were described in meeting sunearies dated May 12 and 24, 1989 (Copies of prevfous meeting suaearies are enclosed without the viewgraphs and attendee lists).
Ouring June 22, 1989 meeting, PPSL once again emphasized that there are several traditional probabflfstfc risk assessment characteristfcs which detract from gaining full potential benefits of operatfonal safety based on insights from evaluation of severe accidents.
The following examples were cited by PPM. to illustrate the pitfalls of using the traditional approach to risk assessment.
J 1.
The traditfonal approach (which includes the IPE approach) cannot read) ly be used to follow accident sequences from fnftiatfon to the final plant damage state (e.g. separation of front line function states from containment sequences).
Consequently, the available hardware that can be used to prevent or mitigate the consequences of an accfdent sequence can not be readily identified for use at each step of the accident sequence.
This results in higher than necessary calculated core damage frequencies.
2.
The traditional approach uses conservatfvdly prescribed coamon cause faflure rates, non-specific plant failure rates, limited operator actions, and very high operator error rates for critical actions.
Consequently, a
large number of potential accident recovery actions are missed, simple plant modifications to aid accfdent recovery are not consfdered, and procedures are not developed and operators not trained to respond to each step of the accfdent sequence.
This also results fn higher than necessary calculated core damage frequencies.
3.
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Based on the above, the PAL believes that while conventional approach provides some bottomlfne values of measure of risk, ft fnhfbfts the potential use of existing plant hardware, addftfon of fnexpensfve new
- hardware, improvement of existing. procedures, and development of new procedures.
In fts own analysis, which fs based on the PPSL IPE for Susquehanna, Units 1 and 2, PPKL has rectffied the pitfa11s of the traditional approach to risk assessment.
The PP!L incorporates the use of exfstfng hardware,
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MEETING WITH PENNSYLVANIA POWER AND LIGHT COMPANY - JUNE 22, 1989 ENCLOSURE 2 NAME Mohan Thadani Wayne Hodges Ashok Thadani S. A. Varga J.
G.
Par tlow Charlie Tinkler Len Soffer John Flack PK Niyogi J. 0.
Thoma Steve Blazo Ann Ramey-Smith Farouk Eltawila Norm Lauben William Beckner Scott Humphries Rich Barrett Glen Kelly Gene Y. Suh Joel J.
Kramer Ray Harris Paul Hill Cas Kukielka Eric Jebsen Bob Cushman David Ney Raymond Ng Stan P. Maingi John C. Lane Bill Johnston AFFILIATION NRC/NRR
. NRC/NRR/DEST/SRXB NRC/NRR/DEST NRR/DRP ADP/NRR NRR/SPLB NRC/RES/SAIB NRC/RES/SAIB NRC/RES/PRAB NRR/DRP Bechtel'ower Corp RES/HFB RES/AEB RES/RPSB RES/SAIB Scienthech, Inc.
NRR/RAB NRR/DRP NRR/DRP NRC/RES/DSR/HFB PPAL PPAL PPSL PPSL NMPC PA/DER/BRP NUMARC PA/DBR/BRP RES/SAIB NRC/Reg.
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