ML20214T723

Informs of Major Discrepancies Between B&W Topical Rept BAW-10075A,Rev 1, Multinode Analysis of Small Breaks for B&W 177-Fuel Assembly...Plants W/Raised Loop Arrangements & Internal Vent Valves, & as-built Configuration of Plant

ML20214T723
Person / Time
Site:	Davis Besse
Issue date:	11/25/1986
From:	Williams J TOLEDO EDISON CO.
To:	Stolz J Office of Nuclear Reactor Regulation
Shared Package
ML20214T726	List: ML20214T723 ML20214T750
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-2.K.3.31, TASK-TM 1330, TAC-62086, NUDOCS 8612080675
Download: ML20214T723 (2)

Text

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TOLEDO

%sm EDISDN Docket No. 50-346 JOE VVILUAMS JR w vu nww wu,r g 19) 249-2300 License No. NPF-3 pa rem Serial No. 1330 November 25, 1986 Director of Nuclear Reactor Regulation Attention: Mr. John F. Stolz PWR Project Directorate No. 6 Division of PWR Licensing-B United States Nuclear Regulatory Commission Washington, D. C. 20555

Dear Mr. Stolz:

During a review of the Babcock & Wilcox (B&W) analytical assumptions to be used for the NUREG-0737, Item II.K.3.31 analysis for the Davis-Besse Nuclear Power Station, Toledo Edison discovered potentially non-conserva-tive discrepancies between B&W Topical Report BAW-10075A, Revision 1, "Multinode Analysis of Small Breaks for B&W's 177-Fuel Assembly Nuclear Plants with Raised Loop Arrangements and Internal Vent Valves," and the as-built configuration of the Davis-Besse Plant. These discrepancies were identified by Toledo Edison and reported in LER 86-028, Revision 0, dated August 8, 1986.

The major discrepancies identified by Toledo Edison and reported in LER 86-28, Revision 0 are:

1) BAW-10075A used a RCS low pressure trip setpoint of 2065 psia instead of 1900 psia for Davis-Besse.

2) BAW-10075A assumed a 43.5 second coastdown time for Main Feedwater (MFW) Flow instead of a shorter time of 7 seconds.

3) BAW-10075A assumed steam generator secondary side water level would be controlled to 32 feet by the Auxiliary Feedwater (AFW)

System instead of the 10 feet setpoint used at Davis-Besse.

4) BAW-10075A assumed one AFW pump would supply water to both steam generators whereas with the Davis-Besse AFW System one AFW pump feeds only one steam generator assuming the worst case single failure.

\

THE TOLEDO ED: SON COMPANY ED: SON PLAZA 300 MADISON AVENUE TOLEDO, OH:0 43652

D ckst Ns. 50-346 License No. NPF-3 Serial No. 1330 November 25, 1986 Page 2 T assess 2

the impact of these discrepancies, B&W re-analyzed the 0.04 ft SBLOCA with the presently approved B&W ECCS evaluation model using assumptions consistent with the present Davis-Besse Nuclear Power Station configuration. The results of this analysis were recently submitted to the NRC in response to NUREG-0737, TMI Action Item II.K.3.31 on plant-specific SBLOCA analyses (derial No. 1316). This submittal included B&W Report BAW-1981, "Small Break Loss of Coolant Accident Analysis for the 0737, Item II.K.3.31",

B&W177FARaisedLoopPlantinResponse-toNUREgSBLOCAresultsusingthe dated October, 1986, which compares the 0.04 ft present ECCS evaluation model with the results contained in BAW-10075A.

A comparison of the revired :esults with the BAW-10075A results showed that there was a slight decrease in minimum reactor vessel water level but that both agalyses demonstrated that the core would remain covered for the 0.04 ft SBLOCA. This comparison indicates that the discrepancies identified were non-conservative; however, when compared with the conserv-atisms in the overall.model they have a negligibly small effect upon the overall transient response. Consequently, Toledo Edison concludes that the SBLOCA licensing analyses performed for Davis-Besse still satisfy the requirements of both 10 CFR 50.46 and 10 CFR 50, Appendix K.

Additionally, as requested by the NRC in a telephone conversation with Toledo Edison, enclosed please find a copy of the B&W report, " Davis-Besse Small Break Loss of Coolant Analysis (SBLOCA) Assumptions Evaluation" (Document No. 51-1164527-00, dated September 11, 1986). The attached report summarizes the original B&W evaluations performed regarding the above discrepancies. This evaluation was performed prior to the completion of the analysis described in B&W-1981 and it concludes that the variation of these parameters did not have any significant effect upon the SBLOCA calculations performed to support the licensing of the Davis-Besse Nuclear Power Station.

Very truly yours, kY$ 't / r

JD:p1f Attachment ec: DB-1 NRC Resident Inspector