ML20148D700

Forwards RAI Re AP600 Adverse Sys Interactions for Beyond Design Basis Accident Scenarios Involving SG Tube Rupture W/Failure of One or More Rector Coolant Pumps to Trip When Required

ML20148D700
Person / Time
Site:	05200003
Issue date:	05/28/1997
From:	Huffman W NRC (Affiliation Not Assigned)
To:	Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
References
NUDOCS 9706020058
Download: ML20148D700 (4)

Text

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May 28,1997 Mr. Nicholas J. Liparulo, Manager Nuclear Safety and Regulatory Analysis 3

. Nuclear and Advanced Technology Division Westinghouse Electric Corporation l P.O. Box 355 l Pittsburgh, PA 15230

SUBJECT:

AP600 ADVERSE SYSTEMS INTERACTIONS REQUESTS FOR ADDITIONAL INFORMA-TION (RAI)

Dear Mr. Liparulo:

The staff has recently been reviewing the potential for AP600 adverse system interactions for beyond-design-basis accident scenarios involving a steam a

generator tube rupture with a failure of one or more reactor coolant pumps to trip when required. Westinghouse letter NSD-NRC-97-5116, dated May 9, 1997, provided revision 1 to the AP00 Adverse System Interactions (ASI) report,

. WCAP-14477, which evaluates potential AP600 system interactions and their

impact on plant safety. Based on the staff's review of the revised ASI report, some clarification is needed related to reactor coolant pump (RCP) interactions with the passive residual heat removal (PRHR) system. A request for additional information on this subject is enclosure with this letter. j If you have any questions regarding this matter, you can contact me at

(301) 415-1141. ,

1 l Sincerely, 3 original signed by:

4 l WiliiamC..Huffman,ProjectManager 4 Standardization Project Directorate sDivision of Reactor Program Management

. 0ffice of Nuclear Reactor Regulation Docket No.52-003 ,

i

Enclosure:

As stated i cc w/ enclosure:

4 See next page DISTRIBUTION:

Docket File PDST R/F i PUBLIC MSlosson TRQuay TKenyon BHuffman JSebrosky DJackson JMoore, 0-15.818 WDean, 0-17 G21 /

ACRS (11) GHolahan, 0-8 E2 JLyons, 0-8 E23 i Alevin, 0-8 E23 NSaltos, 0-10 E4 MCunningham, 0-10 E4 JF1ack,-0-10 E4 yfO$lI

$ T l no (3f ,000 DOCUMENT NAME: A:ASI-SGTR.RAI j To rective a copy of thle document inescate in the boa: "C" = Copy Mthout ettechment/ enclosure "E" = Copy with attachment / enclosure "N" = No copy 0FFICE PM:PDST:DRPM D:PDST:DRPM I NAME WCHuffmani h TRQuay 'O4 i DATE 05AW/97 05/2*/97 0FFICIAL RECORD COPY 9706020058 970528 PDR ADOCK 05200003 4 PDR

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

Westinghouse Electric Corporation AP600  :

cc: Mr. B. A. McIntyre Mr. Ronald Simard, Director Advanced Plant Safety & Licensing Advanced Reactor Programs 3 Westinghouse Electric Corporation Nuclear Energy Institute.

4 Energy Systems Business Unit 1776 Eye Street, N.W.

P.O. Box 355 Suite 300 l Pittsburgh, PA 15230 Washington, DC 20006-3706 i

i Ms. 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 l~ Pittsburgh, PA 15230 Mr. James E. Quinn, Projects Manager LMR and SBWR Programs *

Mr. M. D. Beaumont GE Nuclear Energy i Nuclear and Advanced Technology Division 175 Curtner Avenue, M/C 165 l W:!stinghouse Electric Corporation San Jose, CA 95125 One Montrose Metro j 11921 Rockville Pike Mr. Robert H. Buchholz i Suite 350 GE Nuclear Energy l Rockville, MD 20852 175 Curtner Avenue, MC-781 San Jo.se, CA 95125-l Mr. Sterling Franks

} U.S. Department of Energy Barton Z. Cowan, Esq.

4 NE-50 Eckert Seamans Cherin & Mellott j

19901 Germantown Road 600 Grant Street 42nd Floor '

Germantown, MD 20874 Pittsburgh, PA 15219 i

Mr. S. M. Modro Mr. Ed Rodwell, Manager Nuclear Systems Analysis Technologies PWR Design Certification .

Lockheed Idaho Technologies Company Electric Power Research Institute Post Office Box 1625  !

3412 Hillview Avenue Idaho Falls, ID 83415 Palo Alto, CA 94303 Mr. Frank A. Ross Mr. Charles Thompson, Nuclear Engineer U.S. Department of Energy, NE-42 AP600 Certification Office of LWR Safety and Technology NE-50 19901 Germantown Road 19901 Germantown Road Germantown, MD 20874 Germantown, MD 20874

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AP600 ADVERSE SYSTEM INTERACTIONS j REQUESTS FOR ADDITIONAL INFORMATION 440.647 The staff needs clarification with regard to some of the information provided in WCAP-14477, Rev. 1, the AP600 Adverse Systems Interactions i

(ASI) report regarding reactor coolant pump (RCP) interactions with the

! passive residual heat removal (PRHR) system as discussed on pp. 2-8 and 1

i 2-9 of the report. The staff's main concern centers on a beyond-design-basis accident scenario involving a steam generator tube rupture (SGTR) i with failure to trip a single RCP, due perhaps to a common-cause failure 1

1. (CCF) of all of the breakers for that RCP. The scenario assumes that ac power is available after the SGTR occurs, so that the pump continues to run after a valid " trip" signal that actuates the core makeup tanks (CMTs) and the PRHR system. For parts a-c below, the staff assumes that the SGTR occurs in the steam generator (SG) on the loop opposite the PRHR

, heat exchanger, and that the RCP that fails to trip is one of the two on i

the SG with the ruptured tube. Westinghouse has submitted an analysis of a similar event, in which All of the RCPs continue to run, but has not i addressed quantitatively the case in which only one RCP fails to trip.

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a. The ASI report states that operation of both of the RCPs in the loop opposite the PRHR heat exchanger could cause reverse flow in the PRHR heat exchanger (HX), which would presumably degrade its j performance. Does this same potential exist if only one pump is j running in the loop opposite the PRHR heat exchanger?

b. Even if reverse flow in the PRHR system could not occur with only

one RCP operating as postulated above, could the continued opera-

! tion of the RCP degrade the performance of the PRHR HX by affect-ing the downcomer pressure distribution near the PRHR-side cold legs?

c. What is the potential for a single operating RCP in the loop opposite the PRHR heat exchanger to interfere with heat removal ,

through the PRHR HX and simultaneously to degrade performance of the CMTs?

d. How would the system response change if the SGTR were in the PRHR-side SG (potentially affecting the return flow from the PRHR HX to the SG outlet plenum), with the operating RCP in the loop opposite the PRHR heat exchanger?

e. The statement on p. 2-9, at the end of the section on this inter-action, referring to a Chapter 16 SSAR requirement, needs further elaboration. Under what conditions is at least one RCP required to operate on the PRHR loop? Assuming that a valid RCP-trip signal is received in response to the SGTRs postulated above, how would this requirement affect the continued operation of the RCP in the loop opposite the PRHR heat exchanger that fails to trip, assuming that an operator is unable to trip that pump?

Enclosure

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f. How much margin exists in the AP600 to deal with the scenario as postulated, to prevent excessive inventory loss through the SGTR (exacerbated by the operating RCP), resulting in SG overfill, containment bypass, and potential core uncovery? If operator action is required to deal with this event, does sufficient time exist for necessary actions to be taken to preclude core damage and release of radioactivity? What specific operator actions could be taken to deal with an RCP that fails to trip due to CCF of the breakers?

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