ML20197A622

Forwards SER Accepting Applicability of Wcobra/Trac Computer Code for Large Break LOCA Analyses of AP600

ML20197A622
Person / Time
Site:	05200003
Issue date:	02/19/1998
From:	Huffman W NRC (Affiliation Not Assigned)
To:	Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
References
NUDOCS 9803090315
Download: ML20197A622 (4)

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February 19, 1998 -

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Mr. Nicholas J. Liparuto, Manager .

Nuclear Safety and Regulatory Analysis Q '

< Nuclear and Advanced Technology Division i

, Westinghouse Electric Corporation c y 4 . P.O. Box 355

! ( Pittsburgh, PA 15230

SUBJECT:

OPEN ITEMS ASSOCIATED WITH THE APCOO SAFETY EVALUATION REPORT (SER) ON THE APPLICABILITY OF WCOBRAfrRAC FOR LARGE BREAK LOCA ANALYSES

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Dear Mr. Liparulo:

The Reactor Systems Branch of the U.S. Nuclear Regulatory Commission has completed its SER on the applicability of the WCOBRAfrRAC computer code for large break !oss of coolant accident (LOCA) analyses of the AP600. Open iterns from a preliminary SER were provided to Westinghouse on December 18,1997. In addition to the previously identified items, the final SER contains several new items. These new items have been the subject of ongolng discus-tions with Westir.ghouse and resolution of these items should not result in any impact on the dasign certification schedule. These items have been designated as FSER open items an are attached in the enclosure to this letter if you have any questions regarding this matter, you may contact me at (301) 4151141.

Sincerely, original signed by:

William C. Huffman, P oject Manager Standardization Project D! rectorate Division of Reactor Program Managcment Office of Nuclear Reactor Regulation Docket No. 52 003

Enclosure:

As stated cc w/oncl: See next page 2

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Mr. Nicholas J. Liparulo Docket No. 52 003 Westinghouse Electric Corporation AP600 cc: Mr. B. A. McIntyre Mr. Russ Bell Advanced Plant safety & Licensing Senior Pitiect Manager, Programs Westinghouse Electric Corporation Nuclear Energy Institute Energy Systems Business l' nit 1776 l Street, NW l 4

P.O. Box 355 Suite 300 l Pittsburgh, PA 15230 Washington, DC 20006 3706 Ms. Cindy L. Haag Ms. Lynn Connor Advanced Plant Safety & Licens;ng Doc Search Associates Westinghouse Electr'c Corporation Post Of6ce Box 34 Energy Systems Business Unit Cabin John, MD 20818 Box 355 Phtsburgh, PA 15230 Dr. Craig D. Sawyer, Manager Advanced Reactor Programs Mr. Sterling Franks GE Nuclear Energy U.S. Department of Energy 175 Curtner Avenue, MC 754 NE 50 San Joss, CA 95125 19901 Germantown Road Germantown, MD 20874 Mr. Robert H. Buchholz GE Nuclear Energy Mr. Frank A. Ross 175 Curtner Avenue, MC 781 U.S. Department of Energy, NE-42 San Jose, CA 05125 office of LWR Safety end Technology 19901 Germantown Road Barton Z. Cowan, Esq.

Germantown, MD 20874 Eckert Seamans Cherin & Mellott 600 Grant Street 42nd Floor Mr. Charles Thompson, Nuclear Engineer Pittsburgh, PA 15219 AP600 Certification NE 50 Mr. Ed Rodwell, Manager 19901 Germantown Road PWR Det:gn Certification Germantown, MD 20874 Electric Power Research Institute 3412 Hillview Avenue Mr. Robert Malers, P.E. Palo Alto, CA 94303 Pennsylvania Department of Environmental Protection Bureau of Radiation Protection Rachel Carson State Office Building P.O. Box B469 Harrisburg, PA 17105-8469 4

1. • be I

SER OPEN ITEMS ON THEAPPLICATION OF WCOBRA/ TRAC FOR AP600 LARGE BREAK LOCA ANALYSES l

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440.810F The following additional application restriction should be included in the WCOBRA/rRAC Applicability to AP600 Large-Break Loses

• Coolant Accident report, WCAP 14171:

WCAP 14171, Revision 1, documents the application of the Westinghouse large break i LOCA best estimate methodology to the AP600. In developing that methodology some parameters were not included in the uncertainty analysis. Some of these parumeters were

bounded conservatively while others were judged to have an insignificant impact on the low calcula:ted PCT results and for simplicity were not considered. Among the latter set of-parameters are (1) the AP600 unique passive safety system (CMTs and PRHR) modeling, i and (2) fuel rod oxidation models. A bounding assessment of the potentialimpact of the l

PRHR and the CMT systems modeling on the calculated PCT was obtained by eliminating those systems from the large break LOCA transient calculdion. As noted on page 2 33 of ,

WCAP 14171, Revision 1, the effect of these systems is minor. The blowdown phase PCT values for the WCOBRA/ TRAC case in which these systems were elimint:ted each

! decreased by 5 'F from the base case blowdown PCT results. The reflood phase PCT results in the WCOBRA/ TRAC case without PRHR and CMT systems modeled is the same as the base case reflood PCT results.

The AP600 large break LOCA g5 percent PCT values for blowdown and reflood are reported in SSAR Table 15.6.5 9. The limiting PCT is that for the blowdown, at 1676 'F.

In the event that either the blowdown or reflood phase PCT exceeds 1725 'F in a future AF600 best estimate methodology large break LOCA analysis for any reason, Westing-

house shall perform the actions described below.

4 3 s. Repeat the global model matrix of calculations and the final g5 percent uncertainty calculations, s

b. Address the sensitivity to the CMT and PRHR modeling parameters which are not now

, included in the AP600 uncertainty methodology. Repeat the study that identifies the PCT sensitivity to PRHR/CMT elimination, and add the blowdown and reflood PCT impacts as a bias to their respective g5 percent PCT results.

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c. Perform an analysis of the maximum local oxidation using the techniques approved for 3/4 loop plant applications to show compliance with the applicable 10 CFR 50.46 L criteria. A transient with PCT in excess of the 95 percent PCT value identified in step

(a) above, augmented by the biases identified in step (b) above, would be used for the i

oxidation analysis. The core wide oxidation analysis would also be performed using j the methods approved for use in 3/4 loop plant applications.

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d. The results of these calculations will be submitted for staff review before their imple-mentation.

5 Enclosure

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2 440.811F The WCOBRATTRAC Applicability to AP600 Large Break Loss of Coolant Accident report, WCAP 14171, should include an appendix with relevant NRC staff requests for additional information and the Westinghouse responses. The following Westinghouse letters provide the responses the staff referenced in its SER:

(a) B. A. McIntyre, Westinghouse, letter to USNRC, Document Cont:ol Desk, " Westing-house Responses to NRC Requests for AdditionalInformation on the AP600," NTD-NRC-95-4598, Docket Number 8TN 52 003, November 17,1995.

(b) B. A. Mc!ntyre, Westinghouse, letter to USNRC, Dowment Control Desk, " Westing-house Responses to NRC Requests for AdditionalInformadon on the AP600," NSD-NRC 96-4908, Docket Number STN-52 003, December 10,1996.

(c) 8. A. McIntyre, Westinghouse, letter to USNRC, Document Control Desk,

• Responses to Open items on WCOBRATTRAC Applicability to AP600 Large Break Loss of-Coolant Accident," NSD.NRC 97 5171, Docket Number STN 52 003, June 10,1997, (d) B. A McIntyre, Westinghouse, letter to USNRC, Document Control Desk, " Responses j to Open items on WCOBRA/ TRAC Applicability to AP600 tirge Break Loss of-Coolant Accident," NSD NRC-97 5240, Docket Number STN 52 003, July 18,1997.

(e) 8. A. McIntyte, Westinghouse, letter to USNRC, Document Contrni Desk, " Response to Telecon Request for Information on WCOBRA/ TRAC," NSD-NRC 97 5332, Docket Number STN 52 003, September 18,1997.

(t) B. A. McIntyre, Westinghouse, letter to USNRC, Document Control Desk,

• Response Requests for AdditionalInformation on Chapter 15.6.5 of the AP600 Standard Safety Analysis Report (RAI 440.661)," NSD NRC 97 5291, Docket Number STN 52 003, August 27,1997,  ;

(h) Revisions to discussion items Sg and 17a as documented in Westinghouse fax to the NRC dated August 12,1997 440.812F Apptval of the applicability of WCOBRA/ TRAC for LBLOCA analyses of AP600 is contogent on acceptable completion of documentation of WCOBRA/ TRAC for 3/4 loop plants which is currently described in the Westinghouse Electric Corporation, Energy

, Systems Business Unit, Code Qualification Document for Best Estimate LOCA Analysis.

yptumes 1 (Revision 1) to 5. WCAP 12945 P, Juna 1992 to June 1993.

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