ML20059H943

Responds to Unresolved Item Noted in SWS Operational Performance Insp Repts 50-348/93-13 & 50-364/93-13.Bounding Analysis Performed to Verify Acceptable Sys Response. Assumptions for LOSP Coincident W/Loca Event Listed

ML20059H943
Person / Time
Site:	Farley
Issue date:	11/05/1993
From:	Dennis Morey SOUTHERN NUCLEAR OPERATING CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9311100274
Download: ML20059H943 (2)

Text

r South:rn Nuclear Operating Compar$y

. . Post Cnfice Box 1295 Birmingham. Alabama 35201

- Telephone (20s) 868-5131 L

om um, Southern Nudear Operating Company "

Vice Presroent ,

Fariey P:o;ect the Southern elec:nc system Ncrvatier 05, 1993 Docket Nos: 50-348 50-364 U. S. Nuclear Regulatory Conunission ATTN: Document Control Desk Washington, D. C. 20555 Joseph M. Farley Nuclear Plant Inspection n Report Nos. 50-348/93-13 and 50-364/93-13 Gentlemen:

During the recent Service Water System Operational Performance Inspection (SWSOPI), i the NRC questioned several input assumptions for the SWS waterhammer analysis. This topic was identified by the NRC as Unresolved Item 50-348,364/93-13-02. Subsequent to the SWSOPI, a bounding analysis was performed to verify acceptable system response.

Although FNP has had no history of problems associated with waterhammer transients for the SWS, this updated analysis was performed to document that the design and operation of the SWS is not vulnerable to waterhammer excursions. The following are the assurnptions for the LOSP coincident with LOCA event:

. The previous analysis considered a SW pump restart in 7-12 seconds following a LOSP. The updated analysis conservatively considers a dual pump restart in 23 seconds for each train.

. T he previous analysir, assumed an initial SW temperature of 72 degrees F. TI)e updated analysis bounds the Technical Specification limit of 95 degrees F by assuming an initial temperature of 102 degrees F.

. The previous analysis did not consider the SW temperature rise that would result from heat rejected via system heat exchangers. The updated analysis examines the heat input for the limiting components by assessing the maximum SW outlet temperature for the containment coolers and diesel generator heat exchangers that would result from a LOSP and coincident LOCA.

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. The previous analysis was based on the predicted system backpressure that could  ;

result under LOSP/LOCA conditions. The updated analysis minimizes system j backpressure by considering a failure of the SW standpipe coincident with the ,

postulated LOCA/LOSP. It should be noted that this SWS configuration could only result from a seismic event coincident with the LOSP/LOCA or from a passive failure oflow energy piping coincident with the LOSP/LOCA and therefore, is beyond the a FNP design basis. However, this conservative assumption was applied in order to _

address questions regarding waterhammer transients with minimal system .

backpressure.  :

The results of the r_eanalysis indicate a maximum system pressure spike of125 psigi This spike occurs at the discharge of the containment coolers and is well below the system .

design pressure of150 psig. It should be further noted that the analysis assumes no credit for the SWS vacuum breakers. On this basis, it can be concluded that the present design -

and operation of the safety related SWS is conservative with regard to waterhammer .

vulnerability. ,.

Ifyou desire additional information regarding this topic, please advise,  ;

Respectfully submitted, y SOUTHERN NUCLEAR OPERATING COMPANY j

?.b N1.M Dave Morey  ;

DPH:maf WTRHMR. DOC cc: Mr. S. D. Ebneter Mr. T. A. Reed ,

. Mr. T. M. Ross l

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