ML20198Q476
| ML20198Q476 | |
| Person / Time | |
|---|---|
| Site: | 05200003 |
| Issue date: | 01/14/1998 |
| From: | Huffman W NRC (Affiliation Not Assigned) |
| To: | Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| References | |
| NUDOCS 9801230046 | |
| Download: ML20198Q476 (3) | |
Text
._
January 14, 1998 Mr. Nicholas J. Liparulo, Manager Nuclear Safety and Regulatory Analysis Nuclear and Advanced Technology Division Westinghouse Electric Corporation P.O. Box 355 Pittsburgh, PA 15230
SUBJECT:
OPEN ITEM ASSOCIATED WITH THE AP600 SAFETY EVALUATION REPORT (SER) ON THE VALIDATION OF WCOBRA/ TRAC FOR LONG TERM COOLING ANALYSES
Dear Mr. Liparulo:
The Reactor Systems Branch of the U.S. Nuclear Regulatory Commission has completed its SER on the validation of the WCOBRA/ TRAC computer code for long term cooling analyses of thc AP600 following loss-of-coolant accidents. Open items from a preliminary SER were provided to Westinghouse on December 10,1997. In addition to those it'sms, the final SER contains one additionalissue. This issue has been extracted from the SER and designated as an FSER open item in the enclosure to this letter.
If you have any questions regarding this matter, you may contact me at (301) 415-1141.
Sincerely, original signed by:
Wilham C. riuffman, Project Manager Standardization Project Directorate Division of Reactor Program Management Office :,i Nuclear Reactor Regulation Docket No.52-003
Enclosure:
As stated cc wIencl: See next page hh d
DISTRIBUTION:
- Docket File PDST R/F JRoe PUBLIC DMatthews TQuay TKenyon WHuffman JSebrosky JNWilson DScaletti JMoore,0-15 B18 WDean,0-5 E6 ACRS (11)
LLois, O-5 E23
}g RCaruso,0-8 E23 TCollina,0-8 E23 SNewberry,0-8 E2 GHolahan,0-8 E2 JLyons,0-8 D1 ll Illll!lllllllll ll
'4 4
4 S
D E
DOCUMENT NAME: A:\\WCT-LTC1.O'
. To receive a copy of this document, indicate in the box: "C" = Copy without attachment / enclosure "E" = Copy with attachment / enclosure "N" = No copy OFFICE PM:PDST:DRPM l D:PDST:DRPM l l
l NAME WCHuffMbc_,Lt TRQuay',D
- DATE 01/ M 8~
01/d!98 W
_y OFFICIAL RECORD COPY 9801230046 980114 PDR ADCCK 05200003 E
=r Mr. Nicholas J. Liparulo Docket No.52-003 Westinghouse Electric Corporation AP600 t-ec:
Mr. B. A. McIntyre Mr. Raiss 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 Pinsburgh, PA 15230 Washington, DC 20006-3706 Ms. Cindy L. Haag Ms. Lynn Connor Advanced Plant Safety & Licensing Doc-search Associates Wesunghouse Electric Corporation Post Office Box 34 Energy Systems Business Unit Cabin John, MD 20818 Box 355.
Pittsburgh, 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 Jose, CA 95125 19901 Germantown Road Germantown, MD 20874 Mr. Robert H. Buchholz GE Nucis.e Energy Mr. Frank A. Ross 175 Curtner Avenue, MC-781 U.S. Department of Energy, NE-42 San Jose, CA 95125 Office of LWR Safety and 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 Design Certification Germantown, MD 20874 Electric Power Research Institute 3412 Hillview Avenue Mr. Robert Maiers, P.E.
Palo Alto, CA 94303 Pennsylvania Department of Environmental Protection Bureau of Radiation Protection-Rachel Carson State Office Building P.O. Box 8469 Harrisburg, PA 17105-8469 l
i
l SER OPEN ITEM ON THE VAllDATION OF WCOBRA/ TRAC FOR AP600 LONG TERM COOLING ANALYSES 440.809F The calculated total ADS-4 flow was within 15 percent of the measured value for the quasi-steady state during the latter portion of the window for all four validation calculations described in Section 5 of the WCOBRA/ TRAC, OSU Long-Term Cooling Final Validation Report, WCAP-14776, along with two out of three extended calculation ducribed in Appendix A of WCAP 14776. For the extended calculation Test SB01 described in Appendix A of WCAP-14776, the calculated ADS-4 flow near 10,000 seconds exceeded the measured value by nearly 50 percent. However, the total calculated flow out of the primary system, which includes the flow out the break as well as from ADS-4 valves, was in reasonable agreement with the measured values. The primary cause of this discrepancy was that the downcomer level was high enough to cover the cold leg break with liquid in the test, leading to a relatively high break flow and low ADS-4 flow, while the downcomer level in the caiculation was too low to cover the break with liquid leading to a relatively low break flow and high ADS-4 flow. Thus, the cause of the discreparty in the calculation of SB01 is the downcomer level, which was rated "high"in the PIRT. The staff recognizes that the code produced satisfactory results for the totalin-flow and out-ilow, but the calculatiot of the downcomer level should have been more accurate for the 6801 case discussed above. Therefore, the staff considers the calculation of the SB01 liquid level in the downcomer as an open item. Westinghouse should e : plain why its calculation of this puticular test produced the inaccurate downcomer level, and why this code behavior will not occur during AP600 plant calculations.
Enclosure
________- ___--___-_ -__ - -