NRC-92-0099, Forwards Vol 1,Main Rept & Vol 2,Apps of Fermi 2 Individual Plant Exam (Internal Events), in Response to Generic Ltr 88-20,Suppl 1 & NUREG-1335
| ML20114D533 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 09/01/1992 |
| From: | Orser W DETROIT EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20114D535 | List: |
| References | |
| CON-NRC-92-0099, CON-NRC-92-99, RTR-NUREG-1335 GL-88-20, NUDOCS 9209090121 | |
| Download: ML20114D533 (5) | |
Text
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ys Sept embe r 1. 1992 MRC-92-0099 U. S. Nut car Regulatory Commission Attn: Document Control Deck Washington, D.C. 20555
References:
1)
Fenni 2 NRC Docket No. 50-341 NLO License No. NPF-43
- 2) NRC Ceneric Letter 88-20. " Individual Plant Examinations for Severe Accident Vulnerabilities."
dated November 23, 1988, and Supplement 1. dated August 29, 1989.
- 3) Petroit Ediron Letter to NRC. " Fermi 2 Individual Plant Examination Program for Severo Accident
)
Vu.~ ne rabilitie s. " NRC-89-0213. dated (d
October 25. 1989.
4)
NRC Letter to Detroit Edison. " Review of 60-Day Response to Generic Letter 88-20. Individual Plant Examinations (IPE) (TAC No. 74410)." dated January 18. 1990.
- 5) Detroit Edison Letter to NRC. "Sammary Progress
' Report of First IPE Milestone." NRC-91-0013. dated Janua ry 29, 1991.
- 6) Detroit Edison Letter to NRC. " Summary Progress Report of Second IPE Milestone." NRC--91-0083.
dated July 9.1991.
- 7) Detroit Edison Letter to NRC. " Summary Progress Report r Third IPE Milestone". NRC-91-0153, dated November 27, 1991.
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- 8) Detroit Edison Letter to NRC. " Updated Schedule for Submittal of the IPE Report". NRC-92-0051, dated April'30, 1992.
9)
NRC. Letter to Detroit Edison.. " Updated Schedule for
("
Submittal of. Fermi 2 IPE Report (TAC No. M74410)."
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dated June 20, 1992.
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Submittal of the 1 ermi 2 IPE Report 9209090121 920901 N 's 0400M DR ADOCK 05000341 p
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.The purpose _ of -this letter is to submit the report of the Individual Plant Examination (IPE) conducted _ for _ Fermi 2 in response to NRC Generic = Letter 88-20 and Supplement 1 (Reference 2).
The enclosed IPE report was prepared in accordance with the guidelines provided in NUREG-1335. "I6dividual Plant Examination: - Submit tal Guidsuce". This ef fort -involved the updating and expansion of the Level 1 Probabilistic Risk Assessment -(PRA) that was in progress at the time the Generic Letter was issued and the performance of a Level' 2 Containment performance analysis..
- Detroit Edison provided its'60-day. response to NRC Generic Letter 88-20 by Reference 3.
This response was found acceptable by the NRC in Reference-4. The NRC concluded that the Fermi-2 "IPE approach, methodology, and-schedule are -acceptable". As committed in Reference
- 3. - Detroit Edison submitted. summary; progress reports of IPE milestones
- by References S. 6.' and 7. ' Subsequently, as. discussed-below, Detroit Edison updated-the schedule fort submittal of the Fermi 2 IPE Report to September 1,1992- (Reference 8).
This updated schedule was found acceptable by the NPC in Reference 9.
i '
In keeping with the NRC s--objectives. for.the IPE, Detroit Edison
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personnel 5 we been and -continue to be thoroughly involved in the d
Ferm1=2 IPE. This involvenent led to the idecision late:last ' year to mak.el almajor change to the PRA Level 1-model. : This change was considered necessary in order to accurately reflect the unique Fermi 2 of f-site power supply configuration which includes independent 120'KV and 345 KV lines and-switchyards. 1The PRA previously performed by a contractor -treated-the.switchyards and: loss of of f-site power
- events in a: more generic manner. As;a result of this decision the
'IPE has revealed some important insights regardirr 'the _-plant response --
to initiating events ' involving a partial:: loss L oi if-site power.-
' These. insights, as 'well as the overa11' preliminary?results f rom: our
- IPE. were discussed in April;with Region III.' the-Fermi?2 NRR Project Manager and..other members of the.NRC; staf fe Followingithis.-
- discussion. Detroit Edison decided; to request-a schedule' change 'in
- order to examine the PRA' results and : specific: contributors to risk in greater detail. - ' As indicated' in our -letter of April:30th.(Reference
> 8),:we. have.also used this additionali time to update the models-to include more current Fermi 2l system unavailability data.=
- Based on'the calculated core damage' frequency andt radionuclide release
- frequency. the Fermi?2.IPE has -identified no particularf vulnerability to' core damage or unusually poor containment performance.
e Fermi mean core 1 damage ~ frequency has,beenLealculated to:be 5.7x10Tg/yror roughly 1 in 175,0UO. years.
m.
'(O [c A review of!' he relative' contribution ofl each functional accident t
1 class to the total core damage frequency shows that no one class
' dominates the. total. -.The combination = of four dis rse functional
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USNRC September 1. 1992
.NRC-92-0099 Pcge 3 g
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classes contribute ever 80% of the total core damage f requency..These l_
four classes are: loss of containment heat removal. A'lVS events with inadequate heat removal. loss of injection with the rs actor vessel at high pressure; and loss of injection with the reactor vessel at low pressure. These are generally found to be dominant contributors to -
the core damage risk in mst EWRs.
l One functional class which has a lower contribution than might be l
expected is station blackout (approximately 2%). This is due to the unique design of the Femi 2 AC power syrtem which includes:
l 1.
Four Emergency Diesel Generators (EDG).
Two EDG's supply each of l
the main class IE divisions; bus's tie breakers within each division and between divisions 1 -and 2 provido additional flexibility and optionn-for recovery f rom many accident sequences l
involving a loss of - of f-site power.
2.
Four Combustion Turbine Geaerators (CTG) are located on-site' and are used by Detroit Edison during peak load periods. They can also feed Femi 2 and one CTG has a black-start capability and can bc started from the Fermi 2 Control Room.
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Another Femi 2 unique design feature-is the Standby Feedwater System. This system consists of two motor driven (non-ECCS) pumps l
that are capable of injecting 600 gpm each f rom the Condensate Storage Tank to the reactor via the feedwater lines.
Power supply to these pumps can be provided via the CTGa described above.
l-These plant unique design features are clearly key factors 'in L
accounting for the relatively low. core damage frequency calculated for Fermi 2.
This has been highlighted by sensitivity studies performed as part of the IPE.
For example. based on1a sensitivity study, if the j
standby feedwater system and on-site combustion turbine generators were not included in the Fermi' 2 design, then the overall core damage frequency would increase 'by more than_g/ year.
factor of five which would bring the value to approximately 3x10 With regard to"the containment analysis, the IPL results indicate that for 39% of the Fermi 2-core damage end: states, the containment.either -
remains intact or only a low magnitude radioactive release occurs.-
The IPE results predict that the frequency of any large release to the 7
environment would be 8.2x10 / year.
(This is.the Early/HighL release l.
-category described in the report.)
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In summary. Detroit Edison believes the NRC's objectives expressed.in
' Generic Letter' 88-20 have been met.
A detailed analysis of the' design
. f~N and operation of Femi 2 has been completed.and the IPE has confirmed
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I that there are no plant specific vulnerabilities to severe accidents.-
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In the process of_ performing the 11 :. the general level of awareness and understanding of severe accidents at Detroit. Edison has-been'
3 USNRC September 1. 1992
. NRC-92-0099 Page 4 significantly enhanced. We intend to build on this increased le. vel of knowledge in the future.
Through the involvement of Detroit Edison personnel in the IPE process, one of our primary objectives has also been accomplished.
That is, ve have continued the developrent _ of an in-house capability to maintain, utilize and upgrade the IPE modele. This places us in a position where we can continue to probe the IPE models for additional insights and potential in:provements that might further reduce risk.
The preliminary results have already been used last year to develop risk-bcsed inspection guidance for Detroit Edison Quality Assurance pe rsonnel. We anticipate more initiatives of this type in the future in areas such as guidance documents _ related to maintenance. planning, shutdown risk and severe accident management.
We fully recognize the need to continue to study the IPE and develop ef fective methods for communicating the results and insights to all levels of the organization. We 'aro strongly commit ted to doing this.
Specific training programs for this purpose will be developed for licensed operators. toembers of the Emergency Response Organization, managers and technical support personnel.
The Ferini 2 Individual Plant Examination Report (Internal Events).
Volumes 1 and 2. dated August 1992, is enclosed.
If you have any questions, please contact Mr. Robert 'A. Newkirk at
-(313) 586-4056.
Sincerely, u
Enclosure cc:
T. G. Colburn A.-B.
Davis' M. P. Phillipa S. Stasek
-(.
l USNRC September 1,1992
.NRC-92-0099 Page 3 v
I, WILLI AM S. ORSER, do hereby af firm that the foregoing statements are based on facts and circumstances which are true and accurate to-the best of my knowledge and belief.
Yul S UV WILLIAM S. ORSER Senior Vice President.
OV day of,
c4 b,1992,;beforeme On this personally appeared William S./ rder, being first duly ' sworn and O
says that he executed the foregoing as his free act and deed.
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Notary Public ROSAUS A ARMhTiA NOTARY PUSUC STATE CI'M10CCAN MON 205 COUNTY MY COVkpfgDN EXP..NOV.5L1993 s
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