ML20127B713
| ML20127B713 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Limerick |
| Issue date: | 06/04/1984 |
| From: | Reiter L Office of Nuclear Reactor Regulation |
| To: | Thadani A Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19292B772 | List:
|
| References | |
| FOIA-84-624 NUDOCS 8406080318 | |
| Download: ML20127B713 (4) | |
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'JllN 0 41984 MEMORANDUM FOR:
A. Thadani, Chief i
Reliability and Risk Assessment Branch Division of Safety Technology THP.!I.
t James P. Knight, Assistant Director for
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Division of Engineering' Components & Structures Engineering FROM.:
Leon Reiter, Extreme External Event Coordinator Geosciences Branch Division of Engineering
SUBJECT:
COMMENTS ON LIMERICK RISK INSIGHTS REPORT In response to your memorandum of April 27, 1984 to R. E. Jackson, I am providing coments on seismic related issues in the May 1984 Draft of
" Review Insights on the Probabilistic Risk Assessment, Limerick Generating Station."
In heneral the report conveys the points brought out in the DE review as discussed in the September 23, 1983 memort,Jum from Knight to Rowsome.
The comments below reflect BNL's and DE's recommendation to deemphasize the absolute values calculated in the seismic portions of the Limerick Generating Station Severe Accident Risk Assessment (LGS-SARA). This lim tation is not a result of any particular shortcoming in the LGS-SARA but rather of limitations in the state-of-the-art itself. As indicated below specific references to the March 16, 1984 memorandum from Jackson to Hulman which discusses the LLNL calculations at Limerick should be made.
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Leon Reiter, Ex reme External Event Coordiantor Geosciences Branch Division of Engineering
Enclosure:
As stated cc: See next page y
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- A. K. Ibrahim N. C. Chokshi Y. Li A. Lee 2
E. Chelliah G. Lear R. Bosnak V. Noonan R. Martin A. Schwencer e*
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Specific Coments D,
- p. xi(d) - change last sentence to " Calculations show that external i..
-l 3-events contribute less than 25% of the core damage frequency at y
Limerick. 'However, possible differences in sources of uncertainty and
' its treatment in external and internal events argues against placing f,
. much emphasis on this estimate at this time.
- p. II-5 Line 12 - Eliminate sentence that begins "That s"
report.... reasonable". Add " Additional comments on the seismic hazard analysis may bd found in an NRC memorandum dated March 16, 1984. The report and memoranda-indicate that the PECO's analysis is
',I state-of-the-art and that limitations of the current state-of-the-art necessitate placing emphasis on the relative rather than absolute use of 4
seismic PRA calculations.
- p. II Ort the last line "The" should be replaced with "This is."
- p. II At the end of the second paragraph after "..... risk at Limerick", add "The high degree of uncertainty specifically associated with seismic hazard calculations was emphasized as a result of new studies mentioned in an NRC memorandum dated March 16, 1984.
- p. v In the third paragraph the two sentence beginning with "It should be remembered..." should be replaced by.."
We are not aware of any systematic study into the differences in sources and. treatment of uncertainty between internal versus external events. Thus extreme caution should be used in plant comparisons that mix internal with the various types of external events."
Tables 1,-2, 3, 5, 8, 9 - These tables produce results based on single value estimates.
It is-our experience that such tables may be misinterpreted unless specific estimates or discussions of uncertainty are made directly in the tables. This may be particularly important with respect to the cost-benefit analysis in Table 9.
The specific single-value~ estimate (mean, median) used should also be identified. We reconsnend that the tables, and if necessary, the associated text, be modified to' reflect the existence of large uncertainties.
Table 1 - Footnote 2 with respect to Seismic Events should be changed to read " Review did not provide alternate point estimates to that of PECO because of uncertainties. It was recomended that point estimates be deemphasized."'
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Add to References
- 21. Memorandum from R. E. Jackson, DE/NRC to J. Hulman, DSI/NRC " Input to Limerick FES," dated March 16, 1984
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