ML20084F058

Forwards Summary Description of Calculation 8031-1401, Describing Resultant Primary Containment Pressure Effect Due to Inadvertent Actuation of Drywell Sprays,Per 840224 Request

ML20084F058
Person / Time
Site:	Limerick
Issue date:	04/27/1984
From:	Kemper J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Schwencer A Office of Nuclear Reactor Regulation
References
NUDOCS 8405030102
Download: ML20084F058 (3)

Text

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W PHILADELPHIA ELECTRIC COMPANY 2301 M ARKET STREET P.O. BOX 8699 PHILADELPHIA. PA.19101 (215) 84f 4502 April 27, 1984 JOHN S. KEMPER VIC E #R E SID ENT

$NGeNE S RING AND RESE ARCH Mr. A. Schwencer, Chief Licensing Branch No. 2 Division of Licensing U.

S. Nuclear Regulatory Commission Washington, D.C.

20555-

Subject:

Limerick Generating Station, Units 1&2 Response to Procedures and System Review Branch Question

References:

1)

S. L.

Daltroff to A. Schwencer letter dated 1/19/84.

2)

NRC and PECO telecon dated 2/24/84.

File:

GOVT 1-1 (NRC) l

Dear Mr. Schwencer:

As a result of the review of the information submitted witit reference 1,

the staff requested additional information in reference 2.

In response to this request, enclosed is the Summary Description of LGS Calculation No. 8031-1401, describing the resultant primary containment. pressure effects due to inadvertent actuation ^of.drywell sprays.

Sincerely,

_ff*N,/

.:h RJS/gra/042484315~

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See Attached Service List l

8405030102'B4042705000352

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SUMMARY

DESCRIPTION OF LCS CALCULATION No. 8031-1401 (USED IN DEVELOPMENT OF EPG CALC #9)

Bechtel Calculation No. 8031-1401 was performed to determine the negative containment pressures resulting from actuation of the drywell sprays.

FSAR Section 6.2.1.1.4 provides a description of this analysis and the results for the design basis case. This document summarizes the portion of Calculation No. 8031-1401 which considers another case that assumes a small break LOCA occurs during drywell purging and determines the resultant negative containment pressure due to actuation of the drywell sprays.

A small pipe break pressurizes the drywell at a slower rate than a large pipe break and this.results in the purge valves staying open longer before they isolate due to high drywell pressure. This process allows more non-condensables to be purged from primary containment. The

. drywell will continue to be pressurized by the break af ter isolation and theLremaining non-condensables are driven into the wetwell via the d owncomers. The consequence of having less non-condensables in the wetwell is -that the rate of pressure decrease in the drywell will be more rapid due to the reduced flow rate of non-condensables from the wetwell to the drywell via the vacuum breakers.. Since there are.less non-condensables available to the drywell, the final pressure in the drywell will be less than the final pressure in - the aforementioned

~ design basis ' case. - Except fo'r the. portion of the calculation which determined the amount of non-condensables removed froe primary containment, the methodology and assumptions used for this case are identical to the

- case described in the FSAR.-

The drywell pressure. transient andidrywell purge valve flow' characteristics and closure times were modeled-to calculate the amount of.non-condensables removed; from primary containment. - Since it was; uncertain which. size.

break would cause the greatest amountiof non-condensables to'be purged 2 from primary containment, a spectrum of break sizes was postulated.-

.From the -results of all the cases run, 22,090 -lbe was.the least amount-

~ ofinon-condensables calculated to remain.inside the primary containment (following isolation. This mass is the amount of non-condensables in th'e

suppression pool air space following the purge of drywell non-consensables to the wetwell, via the 'downcomers, due to drywell pressurization.

-Following initiation of the drywell. sprays, la resultant negative pressure of '-4.686 psig was calculated lfor this case,1which is within, the-design pressure of -5 psig, even.though_this is-not considered a designibasis case.-

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This calculation'.is preliminary, since the' data'used for-the suppression

. chamber.to.dryvell vacuum breaker characteristics was based on preliminary <

. test-.results.~ The calculation is currently being: revised-to, incorporate (recent vacuum breaker performance test data. ' The ' resultant' negative-

- pressure is notiexpected to. exceed. the design. limit.

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