ML20199G771

Forwards Document That Identifies Two Issues That Need Resolution by W Before Staff Can Complete Review of Passive Containment Cooling Sys & Wgothic Code

ML20199G771
Person / Time
Site:	05200003
Issue date:	11/20/1997
From:	Scaletti D NRC (Affiliation Not Assigned)
To:	Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
References
NUDOCS 9711250284
Download: ML20199G771 (3)

Text

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l November 20, 1997 l

l Mr. Nicholas J. Liparuto, Manager Nuclear Safety and Regulatory Analysis Nurjear and Adv6nced Technology Division Westinghouse Electric Corporation P.O. Dox 355 Pittsburgh, PA 15230

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION RELAT!VE TO OPENS ITEM IN THE AP600 DESIGN CERTIFICATION REVIEW

Dear Mr. Liparuto:

As a result of the staff's continuing review of the AP600 design certificadon application, the Containment Systems and Severe Accident Branch has ider,tified the major open items resulting from the staff review the WGOTHIC application to the AP600 design certification application.

The enclosure identifies two issues that need resolution by Westinghouse before the staff can complete its review of passive coritainment cooling system and the WGOTHIC code.

if you have any questions regarding this request, please contact me at (301) 4151104.

Sincerely, original signed by:

Dino C. Scalettl Project Manager Standardization Project Directorate Division of Reactor Program Management Office of Nuclear Reactor Regulation Docket No. 52 003

Enclosure:

As stated cc w/ encl: See next page h{h { 1](( fjI] 4 DISTRIBUTION:

Docket File PDST R/F JWRoe PUBLIC DMatthews TRQuay

- TKenyon WHuffman JSebrosky DScaletti JNWilson JMoore,0-15 B18 WDean,0-5 E23 ACRS (ii) lg

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DOCUMENT NAME: A:\AP600PCS

- To receive a copy of this document, Indicate in the box: "C" = Copy without ))

attachment / enclosure "E" = Copy with attachment /ent!osure "N" = No copy l OFFICE PM:PDST:DRPM n. D:PDST:DRPM l l l NAME DScaletti:sL r TRQuay-liW DATE 114T97 f)L __\ 11/#97 OFFICIAL RECORD COPY

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Mr. Nicholas J. Liparuto Docket No. 52 003 Westinghouse Electric Corporation AP600 cc: Mr. B. A. McIntyre Mr. Russ Bell Advanced Plant Safety & Licensing Senior Project Manager, Programs Westinghouse Electric Corporation Nuclear Energy Institute Energy Systems Business Unit 1776 i Street, NW P.O. Box 355 Suite 300 Pittsburgh, PA 15230 Washington, DC 20006 3706 Mr. Cindy L. Haag Ms. Lynn Connor 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 15130 Dr. Craig D. Sawyer, Manager Advanced Reactor Programs Mr. Starting Franks GE Nuclear Energy U.S. De partment of Energy 175 Curtner Avenue, MC 754 NE 50 San Jose, CA 95125 1990's Germantown Road Gerrnantown, MD 20874 Mr. Robert H. Buchholz GE Nuclear Energy Mr. Frr.nk A. Ross 175 Curtner Avenue, MC-781 U.S. Cepartment of Energy, NE-42 San Jose, CA 95125 Office of LWR Safety and Technology 19901 Germantown Road Barton Z. Cowan, Esq.

Germantown, MD 20874 Ecker1 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 Design Certification Germantown, MD 2087a Electric Power Research Instituto 3412 Hillview Avenue Palo Alto, CA 94303 1

a h 480.1065F: The correlations and models used in WGOTHIC for heat and mass transfer are based on local conditions independent of scale. The only test data relevant to the AP600 are from the LST, where local variables were measured and stratification phenomena were shown to exist for some of the tests. Many other experimental facilities in the world data base have also show stratification.

The AP600 WGOTHIC evaluation redel(EM), used for design basis accident analyses,is unable to compute steam concentrations and temperature gradients correctly in its lumped-parameter mode. Many of the model features, such as the choice for the main steam line break (MSLB) position and the use of the Chun and Seban correlation with the evaporated flow model tend to minimize heat flux gradients.

Westinghouse, in WCAP 14407, "WGOTHIC Appl;;ation to AP600," Revision 1, states that the local conditions at the shell wall can be calculated in a conservative manner. However, Westinghouse has not provided sufficient evidence to demonstrate that WG')TH!C provides a conservative calculation of local conditions at the shell wall. Westinghouse arguments in the application report address vertical stratification (an extreme stratification was used), but do not address gradients in the horizontal direction (including the boundary layer next to the shell).

To address the latter, one approach would be to show that the containment atmosphere is indeed well mixed, from a theoretical (first principles) standpoint. The staff considers this approach to be very difficult, particularly in light of the non-homogeneity seen in the world data base. Another approach would be to demonstrate that the lumped-parameter WGOTHIC EM ceaservatively calculates the effects of the local steam concentration near the condensing surfaces.

The current analysis is unacceptable until the one of the above approaches, or an acceptable attemative, is implemented.

480.1086F: The positioning of the MSLB-break location away from its originallocation at the top of the steam generator downward to the vicinity of the operating det.K and into the center of the dome carries th:6 lollowing items of non conservatism: (1) the removal of an asymmetric break, (2) a condition for more mixing above the operating deck, (3) the elimination of the stratification issue, (4) the artificial generation of a well-mixed condition in the dome region, and (5) the i availability of two connections to the below deck regions as compared to only one with the break in the top location.

The combinatis n of these distortions stands a good chance of providing unrealistic computational results compared to the realistic break location. The MSLB is the limitiag accident for the peak pressure in the AP600 therefore an analysis of the MSLB with the break location near the top of the steam generator is required.

Enclosure l

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