ML20128H909

Provides Requested Reanalysis to NRC Which Indicates That Some DACs Will Remain Far Below SBO Temp Limits for Duration of Postulated SBO Event.Rev 1 to Calculation M-73-116 Encl

ML20128H909
Person / Time
Site:	San Onofre
Issue date:	02/12/1993
From:	Marsh W SOUTHERN CALIFORNIA EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20128H910	List: ML20128H909 ML20128H918
References
TAC-M68599, TAC-M68600, NUDOCS 9302170224
Download: ML20128H909 (2)

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, Southem Califomia Edison Company .

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E WALTER C, MARSH - TEt# PHONE'

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February 12, 1993 ,

U; S. Nuclear Regulatory Cvunission 1 Attention: Document Control Desk Washington, D. C. 20555 i; '

Gentlemen:

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. Subject :-  : Docket Nos. 50-361 and.50-362

' Station-BlackoutLTemperature Rise Analysis-San Onofre Nuclear Generating' Station Units-2 and 3 sReference'A: - George Kalman to Harold B. Ray, February 6,' D92, " San Onofre Nuclear _ Generating Station, Units 2 and 3 Station Blackout-

-Analysis'(TAC Nos.- M68599/68600)."

Reference _B: _R. Ornelas (SCE) to Document Control Desk (NRC) letter dated March 12, 1992;:Same Subject.,

Reference C

R..M..Rosenblum (SCE) to Document ~ Control Desk ~(N_RC) letter dated June 11', 1992; Same Subject'.

'_By letter dated April- 17,_1989, SCE provided its-initial response to the

-Station B1ackout Rule to the NRC. This^ original' submittal ~wasl supplemented by:

, la secondlletter dated May 1, 1990. : The.NRC responded _to,these submittals by:

issu:ince of--a Safety Evaluation 'leport (SER) dated February ;6,1992 1(Reference? A). lThis NRC SER requested additional _ information on several . '

= specific-issues. 'By' letter dated March 12, :1992 (Reference B), SCE? respor.ded

< to'the: February /6,fl992 SER and committed .to provide _ additional information, ifor resolution of commentsEon th) loss.'of ventilation assumptions 'and inputs.:

" f "By letter dated' June ll, ~1992 (Reference C), SCE provided this additional

1. information"and, in: response'to NRC question 9, SCE.' committed to provide the-

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, 1NRCyithyattemperature-rise reana. lysis for? the switchgear room,-distribution ~

froom,Ecomputer? room,: control-room; and' control room: cabinet: area. 1The:NRC had' 1 requested SCE to perforn; aireanalysis;util.izing more conservative in-situ electrical heat 41oads.L iAccordingly, the purpose of this letter'is'to provide

,theLrequested reanalysis to the N.RC (enclosed).

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Document Control Desk February 12, 1993 Section 2.1, "Results" of the enclosed reanalysis currently indica 9* that the temperature of one Dominant-Area of Loncern (DAC) (the battery di Sution rooms)-is expected to riso above the maximum allowed temperature 120*F  ;

during a postulated station blackout event.. While SCE is continui..g to- "

evaluate other options, we are currently planning to implement administrative controls and/or praedures to ensure that the distribution room temperature remains below 120*F during an SB0 event. This action will be coordinated with the SCE's previous commitment to ensure that the initial temperature in the' ,

switchgear room, distribution rooms, computer rooms, control room area, and q control room cabinet area is maintained in accordance with UFSAR Table 9.4-4.

The enclosed reanalysis indicates that some DACs (computer room, . control room, and control room cabinet area) wil' remain far below their $80 temperature limits for'the duration of a postulated SBO-event. To provide the largest possible operating " temperature window" for these DAts, SCE plans to revise -

the enclosed reanalysis to determine the highest initial temperature for these areas that will still ensure these areas will remain below their final SB0 temperature limits. Once determined these new, higher initial temperature i limits will be incorporated into the next planned revision of the affected "

procedures and administrative controls, and the SB0 supporting documentation file. .

In our March 12, 1992 letter, SCE committed to complete all SB0 related E01 modifications by June 30, 1993. This date was intended to coincide with operator training. requalifications schedules, and the upcoming Unit 2, Cycle 7 refueling outage. However, because the Unit 2 Cycle 7 refueling outage is currently scheduled for completion in August,1993, we will need-to

- extend the June 30, 1993 E01 revision date. SCE will implement the

- administrative controls and/ar procedures by the end of the Unit 2, Cycle 7 refueling outage.

If you have any questions, or require additional information, please let me 1

- know.

Very truly yours,

[h&lbd cc: J._B. Martin, Regional Administrator, NRC Region V C. W. Caldwell,.NRC Senior Resident Inspector, San Onofre Units 1, 2&3 M. B. Fields, 11RC. project Manager, San Onofre Units 2 & 3

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