ML20141H840

Forwards Request for Addl Info Re 961126 Submittal of WOG Technical Rept,WCAP-14750, RCS Flow Verification Using Elbow Taps at W 3-Loop Pwrs

ML20141H840
Person / Time
Site:	Farley
Issue date:	07/30/1997
From:	Jacob Zimmerman NRC (Affiliation Not Assigned)
To:	Dennis Morey SOUTHERN NUCLEAR OPERATING CO.
References
TAC-M97325, TAC-M97326, NUDOCS 9708010218
Download: ML20141H840 (6)

Text

._ _ _ _ . _ _ _ . _ _-..~. . . _ _ . _ . _ _ . _ _ . _ _ .. _ _ _.._ ._

. 'a July 30; 1997

.' Mr. D. N. Morey Vice President - Farley Project Southem Nuclear Operating .

Company, Inc.

l f Post Office Box 1295 p Birmingham, Alabama 35201-1295

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION RELATED TO WCAP-14750,  ;

"RCS FLOW VERIFICATION USING ELBOW TAPS AT WESTINGHOUSE i 3-LOOP PWRS," JOSEPH M. FARLEY NUCLEAR PLANT, UNITS 1 AND 2 (TAC NOS M97325 AND M97326)

Dear Mr. Morey:

By letter dated November 26,1996, you submitted Westinghouse Owners Group Technical Report, WCAP-14750, "RCS Flow Verification Using Elbow Taps at Westinghouse 3-Loop .

PWRs," for NRC review and approval for the Farley Nuclear Plant, Units 1 and 2.  :

The staff has reviewed your submittal and determined that additionalinformation is required. .

The enclosure identifies the requested additional information needed.

It is requested that the information be provided within 60 days of receipt of this letter. If you ,

require any clarification regarding this request, please call me at (301) 415-2426. '

Sincerely, ORIGINhl SIGNED BY.:

Jacob 1. Zimmerman, Project Manager Project Directorate 11-2 Division of Reactor Projects - 1/Il  ;

Office of Nuclear Reactor Regulation Docket Nos. 50-348 and 50-364

Enclosure:

Request for Additionalinformation j

cc w/ encl: See next page Distribution: i

~ Docket File OGC ) i PUBLIC ACRS PD ll-2 Rdg. JJohnson, Ril NRC HLE CENTER COP 1r BBoger SShaeffer, Rll HBerkow LBerry i JZimmerman CNT ,

To receive a copy of this document, indicate in the box: "C" = Copy without attachment / enclosure "E" =

Ccpy with attachment / enclosure "N" = No copy OFFICE - PM g 2 l LA:PDil-2g L D:I3Dilg @ geggg E l NAME dEffyERMAN:cn LSERSY A[p HBER>lpW / JJy@7,, e/

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, . p rato g & UNITED STATES

, g j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20666-0001

%*****/ July 30,1997 3

Mr. D. N. Morey l Vice riesident - Farley Project Scatnem Nuclear Operating Company, Inc.

Post Office Box 1295 Birmingham, Alabama 35201-1295

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION RELATED TO WCAP-14750, "RCS FLOW VERIFICATION USING ELBOW TAPS AT WESTINGHOUSE 3-LOOP PWRS," JOSEPH M. FARLEY NUCLEAR PLANT, UNITS 1 AND 2 (TAC NOS. M97325 AND M97326)

Dear Mr. Morey:

By letter dated November 26,1996, you submitted Westinghouse Owners Group Technical Report, WCAP-14750, "RCS Flow Verification Using Elbow Taps at Westinghouse 3-Loop PWRs," for NRC review and approval for the Farley Nuclear Plant, Units 1 and 2.

The staff has reviewed your submittal and determined that additional information is required.  ;

The enclosure identifies the requested additionalinformation needed. '

It is requested that the information be provided within 60 days of receipt of this letter. If you require any clarification regarding this request, please call me at (301) 415-2426.

i Sincerely, I W

acob 1. Zimmerman, Project Manager Project Directorate Il-2 Division of Reactor Projects - 1/ll Office of Nuclear Reactor Regulation Docket Nos. 50-348 .nd 50-364

Enclosure:

Request for Additional Information cc w/ encl: See lext page

7

~

J:seph M. Fcriey Nuclear Plint Units 1 cnd 2 cc:

Mr. R. D. Hill, Jr.

General Manager - ,

Southem Nuclear Operating Company Post Office Box 470 Ashford, Alabama 36312 Mr. Mark Ajiuni, Licensing Manager  !

Southem Nuclear Operating Company l Post Office Box 1295 ,

Birmingham, Alabama 35201-1295 i

Mr. M. Stanford Blanton Balch and Bingham Law Firm Post Office Box 306 l

1710 Sixth Avenue North  !

Birmingham, Alabama 35201

)

Mr. J. D. Woodard f Executive Vice President l Southem Nuclear Operating Company i Post Office Box 1295 '

Birmingham, Alabama 35201 State Health Officer Alabama Department of Public Health 1 434 Monroe Street l

Montgomery, Alabama 36130-1701 "

Chairman Houston County Commission Post Office Box C406 Dothan, Alabama 36302 l Regional Administrator, Region ll U.S. Nuclear Regulatory Commission Atlanta Federal Center 61 Forsyth Street, S.W., Suite 23T85 j Atlanta, Georgia 30303 '

Resident inspector U.S. Nuclear Regulatory Commission 7388 N. State Highway 95 Columbia, Alabama 36319

] ,

i REQUEST FOR ADDITIONAL INFORMATION

< ON WCAP-14750. "RCS FLOW VERIFICATION USING ELBOW >

TAPS AT WESTINGHOUSE 3-LOOP PWRS" 1 ,

JOSEPH M. FARLEY NUCLEAR PLANT. UNITS 1 AND 2 l I

i j 1. Page 3, last paragraph, states, " Typically, the core exit and hot leg gradients remain 2 l relatively stable, changing only slightly as the radial power distribution changes during

l. a fuel cycle." i i

(

! Discuss the phenomenon of temperature switching experienced by some plants and its l impact on flow measurement by the proposed elbow tap flow method.

4 l 3

! 2. Page 6, last paragraph, discusses the magnitudes of observed calorimetric flow biases  !

i- and discusses the relationship between power and the onset of calorimetric flow I biases. Discuss how the hot leg gradients remain relatively stable as compared to  !

e power distribution based on the fact that on page 6 calorimetric flow bias are shown to '

j occur based on power level.

I

! 3. Page 11, first paragraph. Discuss how the repeatability term for the installed elbow tap  !

j element at Farley was determined. The topical states that the elbow tap flow  !

i measurement procedure relies on the repeatability of the elbow differential pressure (dp) measurement. WCAP-14750 states in Table A-5 that the elbow tap repeatability is t 0.5% dp. Confirm the value assumed in WCAP-14750 and state it specifically in the  !

topical report. '

4. Page 13, fourth paragraph, the topical stated that calorimetric baseline flows can be i

based on one cycle or the average of multiple cycles with consistent measurements.

The staff has only considered the average of multip!e cycles for previous amendment requests for elbow tap measurement. Provide a discussion on the acceptability of utilizing only a single cycle of data with regard to adequate margin and conservatism. .

5. Based on the topical report discussion that the calorimetric flow bias can be defined, discuss the feasibility of incorporating this known bias into the precision flow calorimetric as opposed to utilizing the elbow tap methodology.

G. Assuming typical accuracy of an elbow tap flow meter, discuss any change in measurement accuracy of the elbow flow tap element over an operational range of 85%

to 100% flow.

7. Page 14 states that the baseline elbow tap flow coefficient is based on the average dp from all elbow taps in all loops. Discuss how the outputs from each group of dp transmitters from each loop are averaged. Please explain why it is appropriate to average all nine transmitters' instrument output as described in WCAP-14750 although there are three distinct flows and three distinct flow elements.

Enclosure

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. 8. The revised thermal design procedure (RTDP) states that uncertainties are combined

! statistically to obtain an overall departure from nucleate boiling ratio (DNBR) i uncertainty factor such that the probability that DNB will not occur on the most limiting j fuel rod is at least 95% (at a 95% confidence level) for any condition I or ll event.

j Provide a discussion on the relationship of a "best estimate" flow model as the basis .

for comparison to the elbow tap flows with respect to the previous precision calorimetric calculated to a 95/95 measurement uncertainty and the 95/95 DNBR analysis.

, 9. Discuss the impact of imbalanced loop flows, the averaging of the elbow tap flows, on the elbow tap flow procedure and whether additional uncertainty should be considered.

Will the assumptions of the topical report remain valid for larger percentages of steam 1

generator tube plugging? What is the maximum tube plugging criteria for Farley?  ;

)

10. Page 24, third paragraph, the topical report states that Farley Unit 1 calorimetric flow measurements for cycles 2 and 3 were obtained at the end of the previous cycle but

were not considered appropriate for a baseline calorimetric. Provide a discussion as to

why these end-of-cycle measurements were not utilized in determining a baseline flow.

i Are '

l end-of-cycle measurements supported by the plant analysis (RTDP)?

i i l 11. Page 27, third paragraph, states that the elbow tap flow measurement repeatability is l estimated at 0.4% of flow. Since the repeatability of the elbow tap flow element is

! crucial, provide a discussion on the determination of the elbow tap flow measurement repeatability. (See question 3.)

1 1 12. Page 32, Table 6-4, " Comparison of Best Estimate and Elbow Tap Flows." How was 4 elbow tap flow baseline determined for comparison to best estimate flow? j

" 13. Figure 6-1, " Comparison of Farley Unit 1 RCS Flows" and Figure 6-2, " Comparison of  ;

Farley Unit 2 RCS Flows" show the best estimate flow exceeding the calorimetric and j

{ elbow tap flows during cycles 9,10,11,12,13 and 14 for Unit 1 and cycle 10 for Unit

2. Explain why the elbow t;p flow exceeds the best estimate flow for cycles 6 and 7.

14. Page 40, Table A1, " Baseline Flow Calorimetric Instrumentation Uncertainties." The

[ table references an uncertainty term "SRA" that is not identified in the Farley setpoint j methodology or the Farley RTDP. Additionally, Table A1 deletes the notes and i assumptions stated in the RTDP for Farley. Provide a description of the new term

"SRA" and provide a basis for the deletion of the notes and assumptions of this table.

15. Page 40, Table A1, instrument spans are revised. What accounts for the change in

! span shown? Instrument errors are also shown to be reduced for feedwater j instrumentation. What accounted for these reductions?

I

i 1

l  !

i

16. Table A4, " Cold Leg Elbow Tap Flow Uncertainty (Process Computer) Instrument J Uncertainties." Uncertainty terms for I/D, and A/D have been eliminated from the

]

' calculation although the information appears to be read from the process computer.  !

Explain these eliminations.

1 i

l 17. Page 47. Discuss why the Final Safety Analysis Report (FSAR) update does not i include a reference to the RTDP, Setpoint WCAP, and WCAP-14750 as well as FSAR l l Chapters 15,7, and 4 as currently referenced in the Farley FSAR.

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