L-77-106, 04/04/1977 Letter Proposed Amendment to Facility Operating Licenses DPR-31 & DPR-41 Options Available for Offsetting an Increased Rod Bow Penalty

04/04/1977 Letter Proposed Amendment to Facility Operating Licenses DPR-31 & DPR-41 Options Available for Offsetting an Increased Rod Bow Penalty

ML18227D845
Person / Time
Site:	Turkey Point
Issue date:	04/04/1977
From:	Robert E. Uhrig Florida Power & Light Co
To:	Stello V Office of Nuclear Reactor Regulation
References
L-77-106
Download: ML18227D845 (10)

Text

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%if;.C DISTRIBUTION rauRT 60 DOCI(ET MATERIAL TPe FROM: DATE OF DOCUMENT Florida Power & Light Company 4/4/77 Mr. Victor Stello 'Miami, Florida DATE >>ECEIVEO Mr. Robert E. Uhrig 4/7/77 ILL E TTE n DNOTonlzto PnOP INPUT FOAM NUMBER OF COPIES >>ECi;IVEO Efo fl I C I N A L fQSNC LASS I F I E 0 Dcopv DESC>>IPTION ENCLOSUAE Ia Ltr w/attached document..notorized '

4/4/77 ~ ~ ~ trans the following: Amdt. to OL/change to Appendix A tech specs. concerns the effects of fuel rod g > @%ra bowing with attached report-entitled i'IIc<~ I'Margins in Turkey Point Units 3,

$(,j',"<j;assai Safe'ty Analysis to Offset the Effects.'f

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Office of Nuclear Reactor Regulation fQyypg Attention: Mr. Victor Stello, Director pp Division of'Operating Reactors co a.s~ Pj's U. S. Nuclear Regulatory Commission F'j~issp Washington, D. C. 20555

Dear Mr. Stello:

Re: Turkey Point Units 3 and 4 Dockets No. 50-250 and 50-251 Proposed Amendment to Facility 0 crating Licenses DPR-31 and DPR-41 In our letter of August 19, 1976 (L-76-300) we described the options available at Turkey Point Units 3 t' for offsetting an increased rod bow penalty. Since then, FPL has performed analyses which account for the effects of fuel rod bowing on the DNBR margin of the Turkey Point nuclear units, and which are in conformance with the DNBR penalties promulgated by the NRC for the type of fuel (Westinghouse LOPAR) currently in the cores of the Turkey Point units. However, instead of taking the rod bow penalty in terms of a reduction in F , we show in the attached safety analysis that sufficient Pant specific DNB margin exists to absorb the entire penalty due to the low power level at which the units are operating. This margin is available because the setpoints and transient thermal-hydraulic analyses are based on a considerably higher enthalpy rise hot channel factor than the one under which the plants are now operating.

Only the curves of reactor core thermal and hydraulic safety limits for normal operation shown in the Technical Specifications need be revised, as the new curves are based on the current enthalpy rise hot channel factor. As this fact is not reflected in the basis'f the Technical Specification, the basis needs revision also. Therefore, in accordance with 10 CFR 50.30, three (3) signed originals and forty (40) copies of a request to amend Appendix A of Facility Operating Licenses DPR-31 and 41 are hereby submitted for your review. The proposed changes are described below and shown on the accompanying Technical Specification pages bearing the date of this letter in the lower right hand corner.

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Office of Nuclear Reactor Regulation Page Two Fi ure 2.1-1 This is the replacement figure for the thermal and hydraulic safety limits and includes the rod bow penalty.

Pa e B2.1-1 The values for F N and F< N are changed to reflect the current values. A statement is added that the safety limits have been reduced to account for rod bow.

Page B2.1-2 The statement on the reactor control and protection system is expanded to indicate that tgis system is based on the original design values of F and F<H, which therefore leads to highly conservative setp8ints.

This proposed amendment has been reviewed by the Turkey Point Plant Nuclear Safety Committee and the Florida Power & Light Company Nuclear Review Board. They have concluded that the proposed amendment does not involve a significant hazards consideration and should not involve prenoticing pursuant. to 10 CFR 2.105.

Until such time as this change is approved, the administrative procedures with regard to DNB margin, detailed in our letter of

,August 19, 1976, will be continued.

Very truly, yours,

~57 k Robert E. Uhrig Vice President REU/RDH/HAS/cpc Attachment cc: Nr. Norman C. Moseley, Region Robert Lowenstein, Esquire II

640 p = 2400 psia

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P ='250 psia 62 P. = 2100 psia 610 600 P = 1900 psia

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570 560 0 20 40 60 . 80 100 120 RMED POT'TER (PERCENT)

F/gure 2. l-1. Rector Core Thnrr.".Of apd Hydraulic Sofcfy Limits Three 4'psnat~

4/4/77

I BASES FOR SAFETY LIMIT,.REACTOR CORE To maintain the integrity of the fuel cladding and prevent fis-sion product release, it is necessary to prevent overheating cladding under all operating conditions. This is accomplish-of'he ed by operating within the nucleate boiling regime of heat

~ansfer, wherein the heat transfer coefficient is very large

.and the clad surface temperature is only a few degrees Fahrenheit above the .coolant saturation temperature. The upper boundary of

.the nucleate boiling regime is termed departure from nucleate boiling (DNB) and at this point there is a sharp reduction of

&e heat transfer coefficient, which would result in high clad temperatures and the possibility of clad failure. DNB is 'not, however, an observable parameter during reactor operation.

Therefore, the observable parameters; thermal power, reactor

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coolant temperature and pressure; have been related to DNB .

through the W-3 DNB correlation. The W-3 DNB correlation has been developed to predict the DNB flux and the location of DNB for axially uniform and non-uniform heat flux distributions.

The local DHB heat flux ratio (DNBR), defined as the ratio of the heat flux that would cause DNB at a particular core location Co the local heat flux, is indicative of the margin to DNB.

Me curves in the Specification represent the loci of points of thermal power, coolant system pressure and average temperature

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which ensure that the design limits on minimum DNBR are

.not exceeded. (1)

The cl'rves are based on the following nuclear hot channel factors:

Pq ~ 2.41 N - 1.5S P ~

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'These limiting hot channel factors are higher than those cal-culated at full power for the range from all control rods fully Mthdrawn to maximum allowable control rod insertion. The con-trol rod insertion limits are covered by Specification 3.2.

Slightly higher hot channel factors could occur at lower power levels because additional control rods are in the core. Bow-ever, the control rod insertion limits dictated by Figure .

3.2-1 ensure that the DNBR is ~ways greater at partial power

.than at full power.

e Me hot channel factors are also sufficiently large to account Sor the degree of malpositioning of part-length rods that is allowed before the reactor trip set points are reduced and "rod withdrawal block and load runback may be required. 12) '-) Rod Mthdrawal block and load runback occur before reactor trip setpoints are reached.

-The Reactor Contxol and Protection System is designed to prevent any anticipated combination of transient conditions that would result

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in exceeding DNBR design limits. '; The setpoints are based on I N N the original values of F and F>H in the FSAR, 3.13 and 1.75 q

respectively, and represent conservative values'ven with the rod bow penalty included.

References (1) FPL report NAD- QR-25 (2) FSAR 3.2.2 32.1-2 4/4/77

STATE OF FLORIDA )

) ss COUNTY OF DADE )

Robert. E. Uhrig, being first duly sworn, deposes and says:

That he is a Vice President of Florida Power & Light Company, the Licensee herein; That he has executed the foregoing document; that the made in this said document are true and correct to the state-'ents best of his knowledge, information, and belief, and that he is authorized to execute the document on behalf of said Licensee.

Robert, E. Uhrig gP

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v Subscrib d and sworn to before me this day of Y PUBLIC, in n for the County of Dade, State of Florida HOTARY PVSUC STAB CP RORIOA AT LARCH'hY COAVrttSSION EXPIRES NOV. 30 'I979 My commission expires: SONOQ) THRU CffsER-L IN5. UMOERWklTERS

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