ML20135B418

Forwards Questions & Comments Related to Rev 1 to WCAP-14171 Wcobra/Trac Applicability to AP600 Large-Break Loca

ML20135B418
Person / Time
Site:	05200003
Issue date:	02/26/1997
From:	Huffman W NRC (Affiliation Not Assigned)
To:	Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
References
NUDOCS 9703030037
Download: ML20135B418 (5)

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,  ; _/ ' February 26 1997 ,

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• 6 Mr. Nicholas J. Liparule, Manag2r , 4 Nuclear Safety /and-Regulatory Analysis ,  ? *

' Nuclear and Advanced Technology Division' Westinghouse Electric ~ Corporation "

P.O._. Box'355 Pittsburgh, PA 15230 -

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SUBJECT:

'FOLLOWON QUESTIONS ON THE REVISED REPORT ON WCOBRA/ TRAC  ;

, APPLICA81LITY-TO AP600 LARGE-BREAK LOSS-0F-COOLANT ACCIDENT

Dear Mr. Liparulo:

. 1 Westinghouse. letter NSD-NRC-96-4871, dated October 30,- 1996, submitted . i Revision. l .to WCAP-14171, WCOBRA/TMC Applicability to AP600 Large-Break Los:- j l- of-Coolant Accident. The revision addresses previous NRC staff comments

. including those provided in an N.RC. letter to Westinghouse dated.May 17, 1996.

i In addition, request for additional information (RAI)' responses related to the j revised WCAP were submitted by Westinghouse letter NSD-NRC-96-4908, dated I December 10, 1996. Subsequently, the staff sent Westinghouse some additional  !

l questions in a letter dated January 3, 1997. The staff and Westinghouse have had a rari~es of telephone conversat'ons discussing the most recent set of

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! questions' In its iYf6Fi E6~c6mplete the evaluation of-WCOBRA/ TRAC applica-

! . bility of AP600, the NRC staff and its contractor'at INEEL, have additional

[ questions. These questions are included as an enclosure to this letter.

Many of.the enclosed questions and comments may not merit the issuance of'  !

i formal RAls. To expedite the review process, Westinghouse is requested to i provide brief written responses to each question'which can then be used to

support detailed discussions during telephone conversations or meetings. The i staff expects that the enclosed questions will be included in the 90en item i

- , tracking system so that the status and disposition of these items can be tracked.

! If you have any. questions regarding this matter, you may contact'me at (301) 415-1141.

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Sincerely, I  ; original ~ signed by: ,

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William C. Huffman, Project Manager Standardization Project Directorate j ,

Division of Reactor Program Management i Office lof Nuclear Reactor Regulation i i

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Docket No.52-003 * ,

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Enclosure:

As stated _'

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Mr. Nicholas J. Liparulo Docket No.52-003 Westinghouse Electric Corporation AP600 i

cc: Mr. B. A. McIntyre Mr. Ronald Simard, Director Advanced Plant Safety & Licensing Advanced Reactor Programs Westinghouse Electric Corporation Nuclear Energy Institute Energy Systems Business Unit 1776 Eye Street, N.W.

P.O. Box 355 Suite 300 Pittsburgh, PA 15230 Washingtor,, DC 20006-3706 l Ms. Cindy L. Haag Ms. Lynn Connor j Advanced Plant Safety & Licensing Doc-Search Associates '

Westinghouse Electric Corporation Post Office Box 34 Energy Systems Business Unit Cabin John, MD 20818  ;

Box 355 Pittsburgh, PA 15230 Mr. James E. Quinn, Projects Manager 4 LMR and SBWR Programs Mr. M. D. Beaumont GE Nuclear Energy Nuclear and Advanced Technology Division 175 Curtner Avenue, M/C 165 l Westinghouse Electric Corporation San Jose, CA 95125 l One Montrose Metro 11921 Rockville Pike Mr. Rebert H. Buchholz Suite 350 GE Nuciear Energy Rockville, MD 20852 175 Curtner Avenue, MC-781 San Jose, CA 95125 Mr. Sterling Franks U.S. Department of Energy Barton Z. Cowan, Esq.

NE-50 Eckert Seamans Cherin & Mellott 19901 Germantown Road 600 Grant Street 42nd Floor Germantown, MD 20874 Pittsburgh, PA 15219 i

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Mr. S. M. Modro Mr. Ed Rodwell, Manager Nuclear Systems Analysis Technologies PWR Design Certification Lockheed Idaho Technologies Company Electric Power Research Institute Post Office Box 1625 3412 Hillview Avenue Idaho Falls, ID 83415 Palo Alto, CA 94303 Mr. Frank A. Ross Mr. Charles Thompson, Nuclear Engineer U.S. Department of Energy, NE-42 AP600 Certification Office of LWR Safety and Technology NE-50 19901 Germantown Road 19901 Germantown Road Germantown, MD 20874 Germantown, MD 20874 l

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l ADDITIONAL COMMENTS ON THE REVIEW OF WESTINGHOUSE'S REPORT WCAP-14171-P, REVISION 1 WCOBRA/ TRAC APPLICA81LITY TO AP600 LBLOCA

1. In a telephone conversation with Westinghouse, the possibility of Westinghouse writing a letter to clarify how the AP600 methodology (which 1 includes some modifications to the approved best estimate methodology) l meets.the-14 steps of the Code Scaling, Applicability, and Uncertainty methodology' was discussed. The staff would find such a letter helpful in completing and documentiag its review. Will Westinghouse commit to providing such a letter?

2. a. The approved methodology presented sensitivity studies for time steps and burnup. Do any of these studies need to be redone for AP600 because of design differences or calculational differences that affect the results for AP600 relative to three- and four-loop plants? l

, Please provide some justification with your answer.

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b. What is the reference for the AP600 break spectrum study that identi-  !

fled the limiting break? Do any of the proposed methodology changes l for AP600 impact the validity of the earlier study? Please provide some justification with your answer.

3. How will Westinghouse determine the ranges for the sensitivity studies on i the AP600 bounded parameters (for example, the temperature ranges for I accumulator water or plant average temperature)?  !

4. a. Does Westinghouse use the approved version of WCOBRA/ TRAC, WCOBRA/ TRAC, M007A.Rev.1, in its AP600 analyses?

b. Are all AP600 design changes (relative to three- and four-loop  !

plants) that are important to LBLOCA addressed through code input (for example, direct vessel injection and the accumulators)? That  !

is, clarify that Westinghouse did not need to modify WCOBRA/ TRAC, M007A.Rev.1, to analyze AP600.

5. Because of the simplifications to the approved methodology made for AP600, Westinghouse stated in WCAP-14171-P, Revision 1, that the valida-tion and correction of the superposition assumptions in the approved methodology was not needed for the AP600. However, the models are still separated into global and lot w models and evaluated using different approaches. Was this separatie 21so' covered in th'e approved methodology superposition validation /ccrrect, ~ ' If yes, clarify how the AP600 methodology accounts for the need to validate / correct for this separa- i tion. If no, then clarify what was done in the approved methodology in this area.

6. In Attachment 1 of Reference 2, Westinghouse described a correction to the HOTSPOT standard deviation-that was made to ensure the appropriate-ness of the results. It is the staff's understanding that this correc-tion should be a part of the AP600 methodology. Clarify if this is true

j. or explain why it is not needed for the AP600 methodology.

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! 7. In WCAP-14171-P, Revision 1. Westinghouse stated that the WCOBRA/ TRAC code uncertainty is kept as a lower limit on the uncertainty. In the approved methodology, the code uncertainty consisted of two parts that were compared to two different uncertainties, and one of those uncertain-ties-is no longer directly included in the AP600 uncertainty methodology.

Therefore, clarify how the code uncertainty is applied in the AP600 methodology. As a related question, if only the one part of the code uncertainty is retained in the AP600 methodology, clarify how Westinghouse's AP600 methodology accounts for the goodness of the WCOBRA/ TRAC results relative to test data.

8. In WCAP-14171-P, Revision 1, the WCOBRA/ TRAC analysis of Cylindrical Core Test Facility Run 58' did not the calculate the oscillations observed in the test results. Clarify if this was due to the WCOBRA/ TRAC analysis calculating that the downcomer level did not recover to the DVI nozzle elevation. If this was the case, clarify the reasons for the difference relative to the test data which did show the downcomer level recovering to the DVI nozzle elevation. If not, clarify the reasons for the i

WCOBRA/ TRAC and test differences. '

REFERENCES  :

1. B. Boyack, et al., Quantifyina Reactor Safety Marains. Acolication of Code Scalina Anolicability. and Uncertainty Evaluation Methodoloav to a {

Larae-Break. Loss-of-Coolant Accident, NUREG/CR-5249, EGG-2552, Decem-ber 1989.

2. N. J. Liparulo, Westinghouse, letter to USNRC Document Control Desk,

" Docketing of Supplemental Information Related to WCAP-12945-P,"

NSD-NRC-96-4718, NSA-SAI-96-167, Nay 9, 1996.

3. J. Sugimotgo, et al., Data Report on Larae Scale Reflood Test-78. CCTF Core-II Test C2-AA2 (Run 058), JAERI Memo 59-446, February 1985.

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' DISTRIBUTION: Letter to-Nicholas J.'Linarulo.' Dated: February 26. 1997 i l

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