ML20247D216
| ML20247D216 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 07/20/1989 |
| From: | Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8907250086 | |
| Download: ML20247D216 (3) | |
Text
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L PHILADELPHIA ELECTRIC COMPANY NUCLEAR GROUP HEADQUARTERS 955-65 CHESTERBROOK BLVD.
WAYNE PA 19087 5691 (zis) sso-sooo July 20, 1989 Docket Nos.
50-352 50-353 License Nos. NPF-39 NPF-84 U.S.
Nuclear Regulatory Commission Attn:
Document Control Desk Washington, D.C.
20555
Subject:
Limerick Generating Station, Units 1 and 2 Response to Request for Additional Information Regarding Consideration of Severe Accident Mitigation Design Alternatives-Correction Gentlemen:
NRC letter dated May 23, 1989, requested Philadelphia Electric Company (PECo) to provide additional information concerning severe accident mitigation design alternatives (SAMDAs) for the Limerick Generating Station (LGS).
The requested additional information was submitted to the NRC by our letter dated June 23, 1989.
Subsequent to the submittal of this letter, an error was discovered in our response to NRC Question 1.
Specifically, the error
,4 l
was in the estimated total early fatality risk.
Consequently, the information in Table 1-4,
" Dominant Early Fatality Sequences,"
included in the attachment to our June 23, 1989 letter, was affected since the percent contribution of each core damage sequence in Table l-4 is based on the total early fatality risk.
Use of the correct total early fatality risk resulted in lowering the percent contribution of individual core damage sequences, l
and increasing the number of core damage sequences that comprise a given percentage of the total early fatality risk.
Accordingly, a revised Table 1-4, indicated by a bar in the right-hand margin, is l
attached and should replace Table 1-4 in the attachment to our June 23, 1989 letter.
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- We'have evaluated the effect of this error'on the= rest of d
it; heil'nformation' provided by our June.- 22,'1989' lettero and'have-
"determinedithat there-are no other changes. -That.is,,the severe 4
l-accident risk,eand consequently the-cost-benefit of the SAMDAs
]
evaluated,: remain asistated in our June 23, 1989 letter.
Accordingly, q
ino new: insights were gained ~and the' conclusions in our-June 23, 1989-
'j lettercremain unchanged.
l If you should'have'any questions, or~ require additional information', please contact us.
Very truly yours,
.0.
G. A.
Hunger, Jr.
Director Licensing Section Nuclear Support Division Attachment cc:
W. T. Russell, Administrator, Region I, USNRC
-T.
J.. Kenny, USNRC Senior Resident Inspector, LGS.
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TABLE l-4 DOMINANT FJmLY FATALITY SEQUENCES Risk
. Accident
% Contribution to Total Ranh Hecuence Class Early Fatality Risk 1
TSRPV 3/S 49 2
TCP2LHU' 4
9 3
TMP2LHU' 4
6 4
TTPPU' 4
5 5
TCP2U' 4
3 6
TTPPLHU' 4
3 These sequences contribute about 75% of the total early fatality risk.
The next 12 sequences would bring the total to approximately 90%.
Each sequence would add 2% or less to the total.
The only additional functional failures occurring in these additional sequences are random reactor vessel failure, seismically induced failure to scram and failure of SBLC, failure of HPCI following a turbine trip ATWS, failure to restore feedwater following HPCI failure for a turbine trip ATWS, failure to bypass level 1 MSIV closure before lowering level after a turbine trip ATWS, and failure to inhibit ADS after an ATWS.
The sequences are defined in Table 1-2, except for the following:
TTPPLHU' - Turbine Trip ATWS (TTP) with stuck open relief valve (P), operator successfully lowers level (LH) but fails to control low pressrue injection after depressurization (U').
Revised July 1989 l
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