ML18142A836

R.E. Ginna - Response to Request of 1/12/1977, DNBR Margins of at Least 22.2% Are Available; No Fuel Rod Bowing Has Been Observed in Ginna 9 Grid, Stainless Steel Guide Tube, 14 X 14 Fuel

ML18142A836
Person / Time
Site:	Ginna
Issue date:	02/11/1977
From:	White L Rochester Gas & Electric Corp
To:	Schwencer A Office of Nuclear Reactor Regulation
References
Download: ML18142A836 (5)

Text

5 U.se NUCLEAR REGULATORY C ISSION DOCKET NUMBER NRC>ORA 1 (2 78) 50-244 FILE NUMBER CIRC DISTRIBUTION FoR PART 50 DOCKET MATERIAL TO: FROM: DATE OF DOCUMENT Rochester Gas & Electric Co. ~

2/11/77

-Mr. A. Schwencer Rochester, New York ~ DATE RECEIVED L. D. White Jr. 2/16/77

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~QCOPY . One sz.gned DESCRIPTION ENCLOSURE Ltr. furnishing response to our 1/12/77 request for information on fuel rod bowing'nd on DNBR margins presently available. ~ .

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PLANT NAME R. E. Ginna No. 1 SAFETY FOR ACTION/INFORMATION 2 17 77 RJL ASSXGNED AD!

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ROCHESTER GAS AND ELECTRIC CORPORATION o 89 EAST AVENUE, ROCHESTER, N.Y. 14649 LEON D. WHITE, JR. TELEPHONE VICE RRESIOENT AREA cooE 7ld 546.2700 February ll, 1977

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Director of Nuclea'r Reactor Regulation cg Attention: Mr. A. Schw'en'cer, Chief Opexating Rea'ctors Branch 0'!

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U.S. Nuclea'r Regulatory Commission ,co~~ >Ey I, Washington, D.C. 20555

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Dear Mr. Schwencer:

>r,O 1I This letter is in res'ponse 'to your reques f for information on fuel'od bowing and on D h rh

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~2, 1977 ns presently available.'e have 'reviewed our fuel design in de supplier, Westingho'use 'Elec'tric Corporation, and have obtained il with our the DNBR margins which 'are pres'ently available.

Protection against reaching DNB ratios less than 1.30 is provided in two plant protec'tion setpoints, the 'underfrequency trip set-point. and the'vertemperature aT setpoint. The underfrequency trip provides'rotection for the loss-of-flow design basis accident while the ovex'temperature 5T trip provides protection for other potentially "

limiting DNB rel'ated transients. Thepresent Technical Specification limit for the underfrequency trip setpoint is 57.5 Hz, however a change 'in the Tec'hn'ic'al Spec'ification limit to 55 Hz was requested by application dated November', 1976. The analysis supporting this application showed a minimum DNBR during the loss of flow accident of 1.615 for a trip setpoint of 55 Hz and a frequency decay rate of 5 Hz/sec , for a margin of 24.2% to a DNBR of 1.30. In addition, mar-gins 'are available 'in the'NBR analysis for the thermal diffusion coefficient'f 3'.'0% and for the 'pitch 'reduction of 3.3%. Thus, a total margin of 30.5% is available 'for the'oss of flow design basis accident.

The analysis supporting sel'ection of the Technical Specification limit on the oVertemperature 'nT trip setpoint was originally performed for Cycle '3 and was submitted to the'RC on February 16, 1973. In this analysis a 9.9% DNBR penalty for densification heat flux spike and a for fuel rod flattening wer'e incorporated. As neither'f penalty 10.0% DNBR the'se 'pen'alties're. required now, they provide for a margin of 19.9%. In addition, thether'mal diffusion coefficient and pitch reduction margins are 'availabl'e, yiel'ding a total margin of 26.2%.

Analysis for Cycl'e 5, submitted to the NRC on March 26, 1975, resulted in a slight increa'se in theovextemperature 6T trip setpoint, thereby using 4.0%, of the DNBR margin. Inasmuch as the overtemperature bT has not been changed since 'the 'Cycle 5 analysis, a DNBR margin of 22.2%

is now available.

ROCHESTER GAS AND ELECTR ORP. SHEET NO. 2 To February ll, 1977 Mr. A. Schwencer, Chief Operating Reactors Branch 41 In addition to reviewing the DNBR margins available, we have reviewed fuel inspection data. As discussed in our letter of August 18, 1976, no fuel rod bowing has be'e'n seen in television examination of fuel assemblies with assembly aver'age burnups in excess of 2S,000 MWD/MTU.

Any assessment of potential DNBR penalties should, in our opinion, be consistent with thes'e 'actual measured data.

In summary, DNBR margins of at least 22.2% are available. In addition, no fuel rod bowing has bee'n observed in Ginna 9 grid, stainless steel guide tube, 14 x 14 fuel.

Very truly yours, L.D. Whi e, Jr.

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