ML20141H970

Forwards RAI Re Risk Based Seismic Margins Analysis Found in AP600 Probabilistic Risk Assessment

ML20141H970
Person / Time
Site:	05200003
Issue date:	05/28/1997
From:	Joseph Sebrosky NRC (Affiliation Not Assigned)
To:	Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
References
NUDOCS 9708040151
Download: ML20141H970 (4)

Text

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May 28, 1997.

Mr. Nich21as J. Liparulo, Manager Nuclear Safety and Regulatory Analysis Nuclear'and Advanced Technology Division Westinghouse Electric Corporation P.O. Box 355 Pittsburgh, PA 15230

SUBJECT:

FOLLOWON QUESTIONS REGARDING THE AP600 SEISMIC MARGINS ANA

Dear Mr. Liparulo:

i

. As a result of its review of the June 1992, application for design certifica-

{. tion of the AP600, the staff has determined that it needs additional informa- ,

l tion. Specifically, the enclosure to this letter contains requests for >

r additional information concerning the risk-based seismic margins analysis

! found in the AP600 probabilistic risk assessment.

a

! You have requested that portions of the information submitted in the i

June 1992, application for design certification be exempt from mantiatory i public disclosure. While the staff has-not completed its review of your ,

request in accordance with the requirements of 10 CFR 2.790, that portion of l i

the submitted information is being withheld from public disclosure pending the '

} staff's final determination. The staff concludes that these followon ques-tions do not.contain those portions of the information for which exemption is sought. However, the staff will withhold this letter from public disclosure i for 30 calendar days from the date of this letter to allow Westinghouse the i-opportunity to verify the staff's conclusions. If, after that time, you do not request that all or portions of the information in' the' enclosures be withheld from public disclosure in accordance with 10 CFR 2.790,'this letter j will be placed in the Nuclear RegCatory Commission Public Document Room.

j. If you have any questions regarding this matter, you may contact me at (301) 415-1132.

I Sincerely, 1

j original signed by:

Joseph M. Sebrosk'y, Project Manager Standardization Project Directorate Division of Reactor Program Management '

Office of Nuclear Reactor Regulation Docket No.52-003

Enclosure:

As stated Il cc w/ enclosure:

See next page 3 '

!!n!:10 jn**

.ao NRC Fil.E CENTER COPY

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DOCUMENT NAME: A: SEIS'PRA.RAI TJ seesive a sepy of this desanimmt,indesTo in she boa: C* Acaptwithout metechment/encioeure *E" = Copy with attachment / enclosure *N* = No copy j OFFICE PM:PDST:DRPM- SPS$:DS$M\ D:PDST:DRPM l l l NAME JSebrosky:sq/th JFla'eit-A TQuay T}W DATE (M;7/97 ff ~ (/s997) C/2Ay97

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9708040151 970528 PDR ADOCK 05200003 A PDR - . .

- . . . . - - -. _ ._. - .- - - . . . - - . - - _ . . - ~ . . . - . . _

Mr. Nicholas J. Liparulo Docket No.52-003 i

'astinghouse Electric Corporation AP600 cc: Mr. B. A. McIntyre Ms. Cindy L. Hug 1

i Advanced Plant Safety & Licensing Advanced Plant Safety & Licensing

, Westinghouse Electric Corporation -Westinghouse Electric Corporation 1

Energy Systems Business Unit l Energy Systems Business Unit i P.O. Box 355 {

Box 355 i Pittsburgh, PA 15230 Pittsburgh, PA 15230 1 4

Mr. S. M. Modro  !

! Nuclear Systems Analysis Technologies  !

i Lockheed Idaho Technologies Company  !

! Post Office Box 1525 j Idaho Falls, ID 83415 Enclosure to be distributed to the following addressees after the result of the proprietary evaluation is received from Westinghouse:

Mr; Ronald Simard, Director Ms. Lynn Connor Advanced Reactor Programs l

' DOC-Search Associates Nuclear _ Energy Institute Post Office Box 34 l 1776 Eye Street, N.W. Cabin John, MD 20818 i l Suite 300

. Washington, DC 20006-3706 Mr. Robert H. Buchholz l GE Nuclear Energy.

Mr. James E. Quinn, Projects Manager 175 Curtner Avenue, MC-781  ;

i LMR and SBWR Programs San Jose, CA 95125' GE Nuclear Energy

, 175 Curtner Avenue, M/C 165 Mr. Sterling Franks

San Jose, CA 95125 U.S. Department of Energy <

NE-50 -

. Barton Z. Cowan, Esq. 19901 Germantown Road )

1 Eckert Seamans Cherin & Mellott Germantown, MD 20874

! 600 Grant Street 42nd Floor Pittsburgh, PA 15219 Mr. Charles Thompson, Nuclear Engineer

! AP600 Certification j' Mr. Frank A. Ross NE-50 i

U.S. Department of Energy, NE-42 19901 Germantown Road 1

! Office of LWR Safety and Technology Germantown, MD 20874  !

( 19901 Germantown Road i j Germantown, MD 20874 1

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! Mr. Ed Rodwell, Manager l PWR Design Certification I Electric Power Research Institute l 3412 Hillview Avenue Palo Alto, CA 94303 {

AP600 SEISMIC MARGINS ANALYSIS REVIEW

REQUEST FOR ADDITIONAL INFORMATION i

. 720.391 A possible failure mechanism of passive containment cooling is the i

blockage of the baffle as a result of a seismically-induced blockage of the drain system (not included in the SMA). The 4

2 opening of the PCCWST air operated valves (due to loss of com-  :

pressed air upon loss of offsite power) would release water which

, would block the baffle if the drain system fails due to the j seismic event. Westinghouse should evaluate and discuss the j feasibility of this containment cooling failure mechanism.

?

l 720.392 As for the internal events analysis, the SMA is performed assuming a 24-hour. mission time. However, in the SMA a discussion, in the form of a sensitivity study, is presented assuming 72-hour mission i time. In such " sensitivity" study, however, actual plant behavior during a loss of offsite power (LOSP) event (at 0.09g review  ;

level) is not modeled. Although it is mentioned that the operator l may decide to stop the ADS actuation timer at approximately 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br />, this is not modeled in the event tree. Furthermore, due

to the assumption of active system unavailability, eventually the 4 plant will need to be depressurized to use IRWST injection and sump recirculation for long-term cooling (even if the operator

' blocks" ADS actuation at 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br />). Therefore, an important i mixed cutset in the analysis should be: Seismically induced LOSP

! (0.099 ) initiating event followed by non-seismic failure of ADS or

IRWST injection or sump recirculation. Please address this issue #

j in your SMA.

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I Enclosure )

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DISTRIBUTION Letter to Mr. Nicholas J. Liparulo. Dated: May 28'. 1997

~* Docket File

• Enclosure to be held for 30 days  :

• PUBLIC PDST R/F MSlosson SWeiss TQuay TKenyon BHuffman JSebrosky DJackson ACRS (11)

WDean, 0-5 E23 JMoore, 0-15 B18 JFlack, 0-8 F5 NSaltos, 0-10 E4 Slee, 0-7 H15 3 l

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