ML20205B251

Forwards RAI Re Topical Rept WCAP-14696, Westinghouse Owners Group Core Damage Assessment Guidance

ML20205B251
Person / Time
Issue date:	03/25/1999
From:	Wen P NRC (Affiliation Not Assigned)
To:	Liberatori L WESTINGHOUSE OPERATING PLANTS OWNERS GROUP
References
PROJECT-694 NUDOCS 9903310184
Download: ML20205B251 (4)

Text

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March 25, 1999

! Mr. Lou Liberatori, Chairman

. Westinghouse Owners Group Steering Committee

Indian Point Unit 24

. Broadway & Bleakley Ave.

l Buchanan, NY 10511

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION FOR WESTINGHOUSE TOPICAL REPORT WCAP-14696, " WESTINGHOUSE OWNERS GROUP CORE DAMAGE ASSESSMENT GUIDANCE"

REFERENCE:

LETTER FROM L.F. LIBERATORI (WOG) TO P.C., WEN (NRC),

? TRANSMITTAL OF RESPONSES TO NRC COMMENTS FROM THE :

FEBRUARY 24,1999 CORE DAMAGE ASSESSMENT MEETING (MUHP-1302,)" MARCH 16,1999.

Dear Mr. Liberatori:

By letter dated November 22,1996, the Westinghouse Owners Group (WOG) submitted Westinghouse topical report %L .F-14696 for NRC review. On February 24,1999, the staff met with WOG to discuss issues related to the topical. In the referenced letter, WOG provided

- information addressed the staff's comments and questions. The staff has completed the review of WOG's response and has determined a need for additional information. The enclosure to this letter identifies the information required. Please address your response to the NRC Document Control Desk and reference WOG Project No. 694.

If you have any questions, please contact me at 301/415-2832 (email, pxw@nrc. gov) or Bob Palla at 301/415-1095 (email, rip 3@nrc. gov).

Sincerely, Original Signed By:

Peter C. Wen, Project Manager Generic lesues and Environmental Projects Branch Office of Nuclear Reactor Regulation Project No. 694

Enclosure:

RAI on Topical WCAP-14696

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March 25,1999 1 4

Mr. Lou Liberatori, Chairman Westinghouse Owners Group Steerine Committee Indian Point Unit 2 Broadway & Bleakley Ave.

Buchanan, NY 10511

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION FOR WESTINGHOUSE TOPICAL REPORT WCAP-14696, " WESTINGHOUSE OWNERS GROUP CORE DAMAGE ASSESSMENT GUIDANCE"

REFERENCE:

LETTER FROM L.F. LIBERATORI (WOG) TO P.C. WEN (NRC),

" TRANSMITTAL OF RESPONSES TO NRC COMMENTS FROM THE FEBRUARY 24,1999 CORE DAMAGE ASSESSMENT MEETING (MUHP-1302,)" MARCH 16,1999.

Dear Mr. Liberatori:

By letter dated November 22,1996, the Westinghouse Owners Group (WOG) submitted Westinghouse topical report WCAP-14696 for NRC review. On February 24,1999, the staff I met with WOG to discuss issues related to the topical. In the referenced letter, WOG provided information addressed the staff's comments and questions. The staff has completed the review of WOG's response and has determined a need for additionalinformation. The enclosure to this letter identifies the information required. Please address your response to the NRC I Document Control Desk and reference WOG Project No. 694.

If you have any questions, please contact me at 301/415-2832 (email, pxw@nrc. gov) or Bob Palla at 301/415-1095 (email, rip 3@nrc. gov).

Sincerely, Pt c. &

Peter C. Wen, Project Manager  ;

Generic Issues and Environmental i Projects Branch '

Office cf Nuclear Reactor Regulation Project No. 694

Enclosure:

RAI on Topical WCAP-14696 L

cc w/ encl: See next page

i l Reauest for Additionalinformation Regardina WCAP-146962

) " Westinghouse Owners Groun_ Core Damaae Assessment Guidance"

1. The revised core damage assessment guideline (CDAG) is structured to deal primarily i with the transient phase of an accident while core degradation is in progress The CDAG does not rely upon use of the post-accident sample system (PASS) because i

PASS results would not be available in a time frame to support protective action l recommendation decision-making and may be misrepresentative of actual conditions in  !

the RCS and/or containment. These limitations are less relevant following restoration of core cooling and return to a stable state. Although some of the sampling and analysis requirements for PASS may be relaxed as a result of the staff's review of WCAP-14986, i licensees would be expected to retain the capability for post-accident sampling of l radionuclides after plant conditions have stabilized, and to use PASS in that time period I to confirm the core damage projections and source term estimates made from fixed, in-plant instrumentation. Accordingly, the capability to translate PASS measurements into

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estimates of core damage and source terms, such as provided by the current core '

damage assessment methodology, should be retained by licensees. Please address the respective roles of the revied CDAG (for use in estimating the extent of core damage in the early stages of an accident) and those portions of the current core damage assessment methodolom that should be retained in order to support the use of PASS radionuclide measurements for confirmirig core damage estimates and refining source term estimates.

2. The response to staff comments regarding fuel clad rupture modeling does not address all staff concerns regarding the basis for the RCS pressure-core exit temperature relationship in Step A2 of the guideline. Please provide: (1) a description of how clad ballooning and rupture predictions based on the MAAP STRETH subroutine compare to predictions based on the burst strain correlationr. in NUREG-0630 for representative sequences, and (2) a characterization of the conservatisms in these models and the degree to which clad rupture may be over-predicted or under-predicted by the CDAG (assuming the recommended parameter values are used.)

3. The response to staff comments regarding the basis for assumed fission product holdup in the RCS included the calculated partitioning of fission products between the RCS and the containment for a range of sequences. Please provide the following additional information: (1) a further subdivision of the fission products inside containment in terms of the fraction that are airborne, trapped on containment surfaces, or present in the containment sump, and (2) indication of the containment spray system status in these calculations. Confirm that the assumptions in the WCAP regarding fission product inventory in containment (i.e., the assumptions on page 24 of 27 and 26 of 27) are still valid when the effects of fission product holdup on surfaces and in sumps is considered.

ENCLOSURE l

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.-Westinghouse Owners Group Project No. 694 l cc:

Mr. Nicholas Liparulo, Manager Equipment Design and Regulatory Engineering Westinghouse Electric' Corporation Mail Stop ECE 4-15 I

P.O. Box 355 Pittsburgh, PA '15230-0355 Mr. Andrew Drake, Project Manager Westinghouse Owners Group Westinghouse Electric Corporation Mail Stop ECE 5-16 P.O. Box 355 Pittsburgh, PA - 15230-0355 Mr. Jack Bastin, Director Regulatory Affairs Westinghouse Electric Corporation 11921 Rockville Pike Suite 107 Rockville; MD 20852 l;

Mr. Hank Sepp, Manager ,

Regulatory and Licensing Engineering l Westinghouse Electric Corporation PO Box 355 Pittsburgh, PA 15230-0355

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