ML18096B498

Response to 02/17/1976 Letter Submitting a re-evaluation of ECCS Cooling Performance Calculated in Accordance with the Approved Combustion Engineering Evaluation Model

ML18096B498
Person / Time
Site:	Saint Lucie
Issue date:	02/01/1977
From:	Robert E. Uhrig Florida Power & Light Co
To:	Ziemann D Office of Nuclear Reactor Regulation
References
L-77-37
Download: ML18096B498 (25)

Text

NRC FoRM 495 I2.(W)

U.S. NUOLSAR RSGULATORYQUUISSION NRC DISTRIBUTION FoR PART 60 DOCI(ET MATERIALt DOCKET NUMIIER 50-335 FILE NUMQER TO:

Mr Ziemann DL DATE OF DOCUMENT 2-1-77.'.ROM:

Florida Power

& Light Co Miami Fla R E Uhrig DATE RECEIVED 2-3"77 SL~TTE R ABORIGINAL Ocor v

.RfNOTORI2ED g}UN c LASS I F I E D PROP INPUT FORM NUMBERNF COPIES RECEIVED i

i'3'siigned DESCRIPTION Ltr notarized 2-1-77....trans the following:

ENCLOSURE

'S U

S

'mdt to'L/Change to'ech Spec'5:

Consisting of revisions with regard to reevaluation of ECCS cooling performanc'e calculated, in ac-cordance wi:th Cohbultion Eng eval'uation model

.....(40 cys encl rec'd)

lp PLANT NAME:

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@OT REMOVE ASSIGNED AD:

FOR ACTION/INFORMATION e.~an n S

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FLORIDAPOWER & LIGHTCOMPANY

, February 1,

1977 L-77-37 o

Office of Nuclear Reactor Regulation Attention:

Mr. Dennis,L., Ziemann, Chief

.~qp Operating Reactors Branch N2, Division o'f Operating Reactors

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JQg<ypQ U.

S. Nuclear Regulatory Commission Washington, D.

C.

20555

Dear Mr. Ziemann:

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Re:

St. Lucie Unit 1 I

Docket, No. 50-335 Proposed Amendment to Facility 0 eratin License DPR-67 In accordance with provision (1) of the June 17, 1976 Order for Modification of License DPR-67, Florida Power a Light Company hereby submits a re-evaluation of ECCS cooling performance cal-culated in accordance with an approved Combustion Engineering Evaluation Model.

The re-evaluation supports reactor operation with a maximum allowable peak linear heat generation rate (PLHGR) of 14.8kw/ft and supplements our earlier submittal L-76-254 of July 9, 1976.

Based on the above, we request that the St. Lucie Unit 1 Operating License be amended by depleting provisions (1) and (2) of the June 17 Order, and that our proposed Technical Specification amendment contained in letter L-76-254 be approved.

Our current.

schedule shows that. ascension to 100 percent power will be possible after February 4,

1977, therefore, your timely review of our request will be appreciated.

With the current PLHGR limit of 12.7 kw/ft, we may not be able to perform certain tests which have been scheduled as part of the 100% power portion of the startup test program.

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The proposed Technical Specification amendment has been reviewed by the St. Lucie Plant Facility Review Group and the Florida Power

& Light Company Nuclear Review Board.

They have concluded that it-does not involve an unreviewed safety question.

Very truly yours, Vice President REU/MAS/cpc Attachment cc:

Mr. Norman C. Moseley, Region II Robert Lowenstein, Esquire

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St. Lucie Unit 1, Core lA ECCS Performance Results Supplement 1

S-I.

Introduction Recent modifications to the STRIKIN-II code prompted a spectrum reanalysis for St. Lucie Unit 1, Core 1, which was reported in Reference l.

These calculations used a STRIKIN-II version which allowed a return to nucleate boiling.

Subsequently, STRIKIN-II was modified to prevent a

return to nucleate boiling, and the Core

1. poison rods

~<ere replaced.

The purpose of this submittal is to report the results of' worst break reanalysis of the reconstituted core (C.ore 1A), using the STRIKIN-II version which does not allow a return to nucleate boiling.

S-II.

~Summa r The calculations documented herein consist of' reanalysis of the most limiting break (0.8 DES/PD)* as reported in Reference 1, at a peak linear heat generation rate (PLHGR) of 14'8 kw/ft.

The table below compares. the results to those reported in Reference l.

Peak Clad Tem erature F

Clad Oxidation (X)

Local Core Wide Reference 1'return to nucleate boiling) 2181 13.1

< 0.795 Reanalysis (no return to nucl cate boiling) 2157 12.9

< 0.791 The reanalysis yielded clad temperatures and oxidation percentages which are within the NRC Acceptance Criteria published in the Federal Register on January 4, 1974.

The decrease in peak clad temperature is explained in Sections III-A, C, and E.

• 0.8 DES/PD

= 0.8 Double-Ended Slot at the Pump Discharge

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S-III. Lar e Break S estrum Anal sis A.

Method of Calculation The only differences between the method used in Reference 1

and that used in the current calculation are the post-CHF heat transfer logic in STRIKIN-II and the treatment of the fuel-clad gap region immediately following clad rupture.

The STRIKIN-II version used in Reference 1 allowed a return to nucleate boiling, while the version used in the current calculation does not (2)

Also, in Reference 1, the gap at the rupture location was assumed to fill with steam immediately at rupture, while the current calculation assumes that the gap contains fission gas until the blowdown peak clad temperature is reached, then 'fills with steam (2)

B.

Emer enc Core Coolin S stem Assum tions The ECCS assumptions are the same as those stated in Reference 1,

C.

Core, S stem, and Containment Parameters 4

The parameters are the same as those given in Reference 1,

except that the calculation of the steady-state gap conductance

. and stored energy in the fuel has been updated to reflect the as-operated condition of the reconstituted core.

Included in this update was a reduction in the PLHGR used in FATES to the actual limit of 14.8 kw/ft.

The steady-state gap conductance and fuel temperatures are compared to those reported in Reference 1 in Table S-III.l.

The effect of the replacement of I

the poison rods upon other system parameters has also been considered and is negligible.

D.

Break Selection Reference 1 presented the results of a full six break spectrum.

As requested in Reference 3, this supplement to Reference 1 analyzed the most limiting break, the 0.8 DES/PD.

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E.

Results Since only the STRIKIN-II calculations were repeated in this analysis, only the results which are different from those reported in. lection. III of Reference 1 will be presented.

Table S-III.2 contains a list of the variables plotted.

The times of interest for the break analyzed are the same as in Reference 1>

except for the hot rod rupture time.

Table S-III.3 presents the rupture, time, the peak clad temperature, and the clad oxida-tion percentages for this analysis.

For comparison

purposes, the results of the spectrum reported in Reference 1 are also shown.

t The prevention of return to nucleate boiling, taken alone, would have resulted in an increase in peak clad temperature over that reported in Reference l.

However, as reported in Tables IV-2 and IV-3 of Reference 2, this effect is essentially cancelled by the change in the gap'treatment at rupture.

The additional effect of updating the steady-state fuel temperature calculation results in a net decrease in the peak clad temperature.

F.

Com uter Code Version Identification The following STRIKIN-II code version was used in this analysis:

STRI KIN-II:

Version 76234

REFERENCES 1.

L-76-254 Letter from R.

E. Uhrig (FP5L) to Yictor Stello (NRC)

July 9, 1976.

2.

Supplement 4 to CENPD-135, "STRIKIN-II,'

Cylindrical Geometry Fuel Rod Heat Transfer Program", August, 1976'.

3.

Letter from D. L. Ziemann (NRC) to R.

E. Uhrig (FP8L), August 26, 1976.

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.TABLE S-I II.l St. Lucie Unit I General System Parameters guantity Reference 1

Return to Nucleate Boilin Value Reanalysis No Return to Nucleate Boilin Peak Linear Heat Generation Rate (PLHGR)

Gap Conductance at PLHGR Fuel Centerline Temperature at PLHGR 14.8 kw/ft 760.4 BTU/hr-ft -

F 3882.5 F

14.8 kw/ft 7g4,8 BTU/hr-ft - F 20'843.7 F

Fuel Average Temperature at PLHGR 2573.6 F

2537.7 F

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Table S-III.2 St. Lucie Unit 1

'Va'riables Plotted for the

" 0.8 x Double-Ended Slot Break in Pump Discharge Leg (0.8 x DES/PD)

Variable Fi gure Number Peak Clad Temperature Local Clad Oxidation Hot Spot Gap Conductance

Clad, Fuel Centerline, Fuel Average, and Coolant Temperature for the Hottest Node Hot Spot Heat Transfer Coefficient Hot Rod Internal Gas Pressure S-III.1 S-III.2 S-III.3 S-III.4 S-III.5 S-III.6

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Table S-I II.3 St. Lucie Unit 1

Rupture Times, Peak Clad Temperatures, and Oxidation Percentages Break Hot Rod Rupture Time sec Peak Clad Tem erature F

Clad Oxidation 5 Local Core-Wi de Reference 1

Return to Nucleate Boilin 1.0 DES/PD 0.8 DES/PD 0.6 DES/PD 1.0 DEG/PD 0.8 DEG/PD 0.6 DEG/PD 10.1 9.9 10.5 10.2 10.1 29.1 2148 2181 2080 2139 2129 1937

13. 2

< 0. 803 13.1

<0.795 12.3

<0.727

~ 13.4

<0.828 13.3

< 0.850 9.6

< 0.565 Reanal sis No Return to Nucleate Boilin 0.8 DES/PD 10.1 2157 12.9

< 0.791

2200 ST.

LUCRE UNIT I 0'8DOUBLE ENDED SLOT BREAK PUNP DISCHARGE LEG I'M CLAD. TENPERATURE 2000 1800 1600 o

1000 1200 A

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3.000 800 600 000 TINE SECONDS I

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ST LUCIE VNIT 0,8 x IJBLE ENDED SLOT BREAK IN NP DISCHARGE LEG LOCAL CLAD OXIDATION

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LUCIE UNIT I 0,8 x IBLE ENDED SLOT BREAK IN 'IP DISCHARGE LEG CLAD TEMPERATURE, CENTERLINE FUEL TEMPERATURE, AVERAGE FUEL TEMPERATURE AND COOLANT TEMPERATURE FOR HOTTEST NODE 4000 3500 3000 2500 FUEL CENTERLINE UJ I

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IGURE S I Is ST, LUCIE UNI 0.8 x OUBLE ENDED SLOT BREAK I PUiRP DISCHARGE LEG HOT SPOT HEAT, TRANSFER COEFFICIENT 180

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FIGURE S

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DI'SCHARGE. LEG HOT ROD INTERNAL GAS PRESSURE 1000,0

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RUPTURE=10,11165 SECONDS 800,0 600,0 000,0.

200,0 0.0,0...:::: 20;0 60,0

TIElE, SECONDS 80,0 100,0

STATE OF FLORIDA

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ss.

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

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

Robert E. Uhrig Subscribed and sworn to before me this day of NOTARY PUBLIC, in nd r the County of Dade, State of Florida HOTARY PUBLIC STATE OF FLORIDA AT LARGf MYCOMMISSIONEXPIRESNOV. 30 1979 N

ommission e<pires