ML18227D332

Letter Response to Request Concerning Results of Westinghouse Safety Analyses

ML18227D332
Person / Time
Site:	Turkey Point
Issue date:	08/19/1976
From:	Robert E. Uhrig Florida Power & Light Co
To:	Stello V Office of Nuclear Reactor Regulation
References
Download: ML18227D332 (6)

Text

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~IMMI%10H (rg FLORIDA POWER 6 LIGHT COiblPANY August 19 I 1976 L-76-300 hO Office of Nuclear Reactor eg ation Attn:

Victor Stello, Jr.,

Di ctor 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 Westin house Safet Anal ses

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CC'loh Mhl The Westinghouse Electric Corporation has informed Florida Power

& Light Company that recent developments have affected the results of certain safety analyses for Westinghouse plants.

The following information regarding this problem is being submitted to you in response to an August 13, 1976 telephone request from your staff.

One development involves the temperature of the fluid in the upper head.

Past ECCS analyses assumed that the temperature in the upper head was equal to the vessel inlet temperature (Tcold).

The conservative judgment into assume that the tem-perature will be equal to the vessel outlet temperature (Thot).

The consequence is a reduction in maximum allowable Heat Flux Hot Channel Factor (Fo) to prevent operation at unacceptable local power levels.

i'he resulting FO limit for Turkey Point is conservatively estimated to be 2.265.

The new F~ limit was derived as shown below:

Note:

[2.32 -A -B +C]

D = 2.165

2. 32 = previous limit on F~

A =.26

= estimated reduction in F due to increase in upper head temperature f om T ld to Th t.

B =.04

= estimated reduction in F< due to plugged steam generator tubes.

C =.05

= estimated increase in F due to the fact that the ECCS analysis peak 81ad temperature is 50'elow the Final Acceptance Criteria.

D 2 20 0 factor for increasing F~ due to operation 2300 100 Mwt below the power level used in the ECCS analysis.

For a 925 ft, accumulator

volume, A =.16 and F< = 2.27.

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PEOPLE... SERVING PEOPLE

To:

Victor Stello, Jr.

Re:

Turkey Point Units 3 and 4

Docket Nos.

50-250 and 50-251 Westin house Safet Anal ses August. 19, 1976 Page Another development involves rod bow.

Recent test results indicate that the rod bow DNB penalty is higher than previously used.

The combination of this penalty with available margins results in an estimated reduction in DNBR on a region-by-region basis.

Increasing the rod bow DNB penalty can be offset by a combination of the following:

a)

A reduction in the maximum allowable Nuclear Enthalpy Rise Hot Channel Factor (F<H) on a region-by-region basis.

i) 0% to 4% reduction for new first cycle fuel applied linearly from Beginning-of-Cycle to End-of-Cycle.

ii) 6% constant reduction for fuel which has received 1 cycle of burnup.

iii) 7% constant reduction for fuel which has received 2 or more cycles of burnup.

b)

A reduction in Tave and a corresponding the Overtemperature hT equation.

(1' 1'

in the constant. in the temperature term in the Overtemperature 8T equation DNBR. )

change in in Tave and difference 1% in c)

An increase in reactor coolant flow.

1% flow increase

=

1% increase in DNBR.)

For the time being, the increased upper head fluid temperature and the increased rod bow penalty are being offset by opera-tionally limiting F~ and F<

as described above.

In the future, operational considerations Say cause us to revise the means by which we accommodate the higher rod bow DNB penalty, in which case we may utilize some other combination of available options.

The revised limits described above represent preliminary esti-mates.

The evaluation of these developments is continuing in

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To:

Victor Stello, Jr.

Re:

Turkey Point Units 3 and 4

Docket Nos.

50-250 and 50-251 Westin house Safet Anal ses August 19, 1976 Page an effort to quantify the effects on the Turkey Point units more precisely.

Very truly yours, Robert E. Uhrig Vice President REV/mS/hlc cc:

Norman C. Moseley, Region IZ Jack R.

Newman, Esq.

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