W3P86-2982, Responds to Addl Questions Re Changes to Large Break LOCA Analytical Models Since Cycle 1 Break Spectrum Performed & Why 0.8 double-ended Guillotine Break Remains Limiting Break Size

Responds to Addl Questions Re Changes to Large Break LOCA Analytical Models Since Cycle 1 Break Spectrum Performed & Why 0.8 double-ended Guillotine Break Remains Limiting Break Size

ML20212B360
Person / Time
Site:	Waterford
Issue date:	12/23/1986
From:	Cook K LOUISIANA POWER & LIGHT CO.
To:	Knighton G Office of Nuclear Reactor Regulation
References
W3P86-2982, NUDOCS 8612290228
Download: ML20212B360 (2)

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• P. O. BOX 60340 LOUISI& ANA POWER L1GHT/ 317NEWBARONNESTREET

• ORLEANS, LOUISIANA 70160 + (504)595-3100 UrTONSYS December 23, 1986 W3P86-2982 A4.10 QA Mr. George W. Knighton, Director PWR Project Directorate No. 7 Division of PWR Licensing-B Office of Nuclear Reactor Regulation Washington, D.C. 20555

SUBJECT:

Waterford SES Unit 3 Docket No. 50-382 Waterford 3 Cycle 2 Large Break LOCA Analysis

REFERENCES:

1. W3P86-3328 dated October 1, 1986

2. W3P86-3384 dated October 28, 1986

3. W3P86-2941 dated November 26, 1986

4. W3P85-2177 dated July 19, 1985

Dear Mr. Knighton:

By the Reference 1 letter LP&L submitted Part B of the Waterford 3 Cycle 2 Reload Analysis Report (RAR). This submittal included those sections of the RAR that described both the LOCA and non-LOCA safety analyses. In response to requests for additional information regarding the methodology used for the Cycle 2 large break LOCA analysis, LP&L submitted References 2 and 3.

In subsequent discussions with your staff, additional questions were raised concerning changes that have been made to the large break LOCA analytical models since the Cycle 1 break spectrum was performed and why, in light of these changes, the 0.8 double-ended guillotine (DEG) break remains the limiting break size. This letter is intended to address this matter.

The most recent break spectrum performed for Waterford 3 is discussed in Amendment 23 of the WSES-3 FSAR (dated November, 1981). Since that time the limiting break (0.8 DEG) has been reanalyzed three times; first, to reflect changes in the Safety Injection Tank (SIT) k-factors (described in Amendment 31 to the WSE5-3 FSAR dated March, 1983) second, to reflect changes in the assumed axial power shape (described in Reference 4) and finally, to reflect l changes necessary for Cycle 2 (described in the RAR).

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Page 2 W3P86-2382 In all of these cases it was not deemed necessary to reanalyze the break spectrum primarily because the aforementioned changes had very little, if any, effect on the blowdown hydraulics and, since the reflood behavior is identical for all large breaks, it is the blowdown hydraulics that determines which break size is most limiting. Thus, the limiting break size identified in the original Cycle 1 break spectrum analysis would also be the limiting break size for Cycle 2.

LP&L has provided detailed justification (References 2 and 3) to demonstrate that the analysis presented in Section 8.0 of the RAR represents the most limiting large break LOCA and hence, the highest peak clad temperature. At the same time however, we realize that the LOCA analyses presented in both the FSAR and the RAR do not incorporate all of the most recent NRC approved LOCA analytical models and, although the analyses are conservative, they are not representative of the latest analytical techniques. In addition, a LOCA reanalysis using the latest NRC approved models will have a significant benefit to LP&L since such analyses will provide a consistent technical basis for Cycle 3 and future reload cycles. Therefore, LP&L belitves it is prudent to reanalyze the large break LOCA (including a new break spectrum) using the latest NRC approved large break LOCA models (which include revisions to the blowdown hydraulics model), and expects to have this effort completed and the pertinent results transmitted to your staff by May 1, 1987. This analysis will be based on the same Cycle 2 data that is currently described in the RAR. We will inform you promptly if there are any changes to this schedule.

LP&L understands that this reanalysis of the large break LOCA is being provided on a confirmatory basis to provide additional information supporting the NRC and LP&L conclusion as to the conservatism present in the current LOCA analysis results. If there are any questions or you require further information please contact me or Bob Murillq at (504) 595-2838.

Yours very truly, f(J&L K.W. Cook Nuclear Safety and Regulatory Affairs Manager hWC/DPS/smb

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cc: E. L. Blake, W. M. Stevenson, R. D. Martin, J. H. Wilson, N. Lauben (NRC/NRR), NRC Resident Inspector's Office (W3) i NS41243 l

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