ML20210K280
| ML20210K280 | |
| Person / Time | |
|---|---|
| Site: | 05200003 |
| Issue date: | 08/14/1997 |
| From: | Huffman W NRC (Affiliation Not Assigned) |
| To: | Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| References | |
| NUDOCS 9708190208 | |
| Download: ML20210K280 (3) | |
Text
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August 14, 1997 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:
REQUESTS FOR ADDITIONAL INFORMATION (RAls) ON THE AP600 STANDARD SAFETY ANALYSIS REPORT (SSAR) CHAPTER 15 ACCIDENT ANALYSES
Dear Mr. Liparulo:
The Nuclear Regulatory Commission (NRC) is still reviewing toe AP600 Chapter 15 Accident Analyses.
Based on recent discussion between the staff
-and Westinghouse on the loss of ac power to plant auxiliaries transients and boron dilution events, the staff has determined that additional information will be needed to complete'its review of Chapter 15. The staff's RAls on the Chapter 15 analyses are provided as an enclosure to this letter, if you have any questions regarding this matter, you may contact me at (301) 415-1141.
Sincerely, original signed by:
William C. Huffman, 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 -
DISTRIBUTION:
Docket File PDST R/F TQuay PUBLIC TKenyon BHuffman JSebrosky DJackson
'JMoore, 0-15 B18 3
WDean, 0-5 E23 ACRS (11)
JLyons 0-8 01 Alevin, 0-8 E23 GHolahan, 0-8 E2 GHsii, 0-8 E23'
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9708190208 970814
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3 U.S. NUCLEAR REGULATORY COMISSION REQUESTS FOR ADDITIONAL INFORMATION ON l
WESTINGH0USE AP600 SsAR CHAPTER 15 ACCIDENT ANALYSES 1
Loss of AC-Power to Plant Aur111 arias i
)
RAI 440.723 The results of the chapter 15 analysis show that the pressurizer pressure f
i safety valves open and remain open for an extended period of-time (up to 5 j
hours) to release steam during pressurization transients (LOAC, LONF, inadvertent operation of the ECCS and CVS malfunction). -To address the staff's concern related to the operability of the safety valves, Westinghouse is requested to provide the following information:
(a)- Provide a' description of thc expected behavior of the pressurizer safety-i
' valves during the period of extended operation at the-relief setpoint, i
What is the duration and frequency.of the opening and closing of the J
pressurizer safety valves? What impact would repeated cycling.of the valves have on their operability.
Provide information on the pressu/izer i
' safety valve design features,< design qualification data, or analyses-that demonstrate that the safety valves will close after repeatedly opening for an extended period of time as shown in the chapter 15 pressurization j
transient analysis.
4 (b) Describe the LOFTRAN flow model' for the pressurizer safety valves and I
justify its adequacy for use in determining (1) the peak pressurizer pressure, and (2 of the pressurize)r safety valves.the duration and frequency of the opening and (c) Analyze _the case with the failure of the pressurizer safety valve to.
i close during pressurization ~ events (such as LOAC) and demonstrate-i' acceptability of the results.
Baron Dilution
[
RAI 440.724 In the Westinghouse response to RAI 440.120 dated May 14. 1997, Westinghouse i
. stated that "the relatively low flow. rate of fluid from the downcomer into the core during post-RCP trip natural circulation phase of AP600 small break LOCA 1
events enables mixing to occur in the core and lower plenum. No unmixed slugs j
of highly dilute liquid from the PRHR are present in the downcomer to enter i
the core during the LOCA design basis scenarios." Please provide quantitative-
. technical justification to support the engineering judgement regarding mixing in the downconer and the lower plenum of the core. The justification should
-include break size (worst case scenario), as well as condensate flow rate and final boron concentration uniformity in the downcome(s). The boron concentration and concentration i
r should also be addressed.
Enclosure I
i.
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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 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 15230 Dr. Craig D. Sawyer, Manager Advanced Reactor Programs Mr. S. M. Modro GE Nuclear Energy Nuclear Systems Analysis Technologies 175 Curtner Avenue, MC-754 Lockheed Idaho Technologies Company San Jose, CA 95125 Post Office Box 1625 Idaho Falls, ID 83415 Mr. Robert H. Buchholz GE Nuclear Energy Mr. Sterling Franks 175 Curtner Avenue, MC-781 U.S. Department of Energy San Jose, CA 95125 NE-50 19901 Germantown Road Barton Z. Cowan, Esq.
Germantown, MD 20874 Eckert Seamans Cherin & Mellott 600 Grant Street 42nd Floor Mr. Frank A. Ross Pittsburgh, PA 15219 U.S. Department of Energy, NE-42 Office of LWR Safety and Technology Mr. Ed Rodwell, Manager 19901 Germantown Road PWR Design Certification Germantown, MD 20874 Electric Power Research Institute 3412 Hillview Avenue Mr. Charles Thompson, Nuclear Engineer Palo Alto, CA 94303 AP600 Certification NE-E0 19901 Germantown Road Germantown, MD 20874
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