ML18227B014

Response to Request for Additional Information on ECCS Reevaluation Supplemental Information

ML18227B014
Person / Time
Site:	Turkey Point
Issue date:	02/02/1977
From:	Robert E. Uhrig Florida Power & Light Co
To:	Stello V Office of Nuclear Reactor Regulation
References
L-77-38
Download: ML18227B014 (15)

Text

P. O. BOX 013100, MIAMI, FL 33101

~~~9 bi g>pe(afopg pQtJK't Ate FLORIDAPOWER & LIGHT COMPANY February 2,

1977 L-77-38 Office of Nuclear Reactor Regulation Attention:

Mr. Victor Stello, Director Division of Operating Reactors U.

S. Nuclear Regulatory Commission Washington, D.

C.

20555

Dear Mr. Stello:

Re:

Turkey Point Units 3 and 4

Docket Nos.

50-250 and 50-251 ECCS Reevaluation Su plemental Information a

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ECCS information applicable to Turkey Point Units 3 and 4 has been submitted by Florida Power s Light Company in letters dated December 9,

1976 (L-76-419) and December 30, 1976 (L-76-438 and L-76-439').

Attached herewith is additional information requested by your staff.

Very truly yours, Robert E. Uhrig Vice President REU/MAS/cpc Attachment cc:

Mr. Norman C. Moseley, Region II Robert Lowen'stein,'Esquire DOCKBfD USNRC

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ATTACHMENT Re:

Turkey Point Units 3 and 4

Additional ECCS Information QUESTION:

Justify that the peak clad temperatures corresponding to different percentages of plugged steam generator'tubes can be obtained by a linear interpolation, and submit a basis for the dependence of Fq on steam generator plug-ging.

ANSWER:

Sensitivity studies were performed by Westinghouse in the early part of 1976 to determine, on a generic basis, the effect, of plugged steam generator tubes on peak clad temperature (PCT) calculated during a LOCA.

Three sets of runs were made, 1 each for a'2 loop plant, a

3 loop

plant, and a

4 loop plant.

The results were summarized and presented at an ACRS ECCS Subcommittee meeting.

Plots of the results are shown in Figure 1.

Figure 1

shows that the curves of bPCT versus percent tube plug-ging are concave upward, which means that linearly interpolating between any two plugging levels results in a higher, or conservative, value of hPCT.

Also, an answer given below to another question justi-fies the relationship between Fq and PCT

(.01 Fq per 10'F).

Therefore, since "Fq vs.

PCT" is known, and "PCT vs. percent plugged tubes" zs known, then the generic relationship between Fc and percent plugged tubes can be determined (Figure 2).

QUESTION:

Submit the Westinghouse ECCS analyses which show that the decrease in accumulator water volume from 875 cu-bic feet to 825 cubic feet corresponds to 36'F rise in PCT.

ANSWER:

Presented here is a discussion of the effect on the LOCA of a 50 cubic foot change in accumulator water volume.

To demonstrate the sensitivity of PCT to changes in accumulatox water volume, specific analyses were made with accumulator water volumes of 825 and 875 cubic feet without changing other Turkey Point parameters.

This resulted in a total change of PCT of 36'F be-cause of the increase in downcomer water height and core inlet velocity.

The effectiveness of accumulators can be studied by inspecting Figures la and lb, which are the downcomer water level and core water level, plots, and Figures 2a and 2B, which are the core reflood water inlet velocity plots.

The optimum accumulator water volume, based on previous studies, is generally a value that results in the downcomer being "almost" full when the accumulators empty.

From Figure la, when %he accumulators empty, the down-comer height is about 9.5 feet for an initial water volume of 825 cubic feet per tank.

Figure lb indi-cates that increasing the initial water volume to 875 cubic feet per tank results in the downcomer being filled to 13.3 feet when the accumulators empty.

This difference in accumulator performance during the acci-dent results in a decrease in PCT from 2194'F for the core using 825 cubic feet initial accumulator water volume per tank to 2158'F for the case using 875 cubic feet.

The above delta change in peak cladtemperature was obtained by explicitly modeling an increase in accumu-lator water volume for the Turkey Point units and can only be applied in the specified range.

This response does not represent a generic sensitivity study.

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QUESTION:

Justify, by submitting the appropriate references to applicable sensitivity studies, the relationship

'between Fq and PCT (.01 F ~10'F PCT).

q ANSWER:

The sensitivity in the ECCS analysis to changes in the total peaking factor has been determined from previous analysis performed by Westinghouse.

v As presented in Reference 12 of the previous ECCS analysis (FPL letter L-76-419 of December 9,

1976) with core power equal to 2192 Mwt, it has been es-tablished that a conservative estimate of 10'F/0.01 Fq is appropriate for use on a generic basis as an interim measure.

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