ML18227D285

Request to Grant Approval for Continued Operation Beyond Time Limit Specified in Amendment 20

ML18227D285
Person / Time
Site:	Turkey Point
Issue date:	01/21/1977
From:	Robert E. Uhrig Florida Power & Light Co
To:	Lear G Office of Nuclear Reactor Regulation
References
L-77-29
Download: ML18227D285 (8)

Text

U.S. NUCLLAR REGULATORY MISSION t

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dP,g>Z'>8M'V 5 C1Cllo h Oak FLORIDA POWER & LIGHTCOMPANY January 21, 1977 L-77-29 0 fice of Nu ctor Regulation Attn:

George Lear, Chief Operatirg Reactors Branch 53 Division of Operating Reactors U.

S. Nuclear Regulatory Commission Nashington, D.

C.

20555

Dear Nr. Lear:

Re:

Turkey Point Unit 4 Docket No. 50-251 Steam Generator Operation On December 3, 1976, the Nuclear Regulatory Commission issued Amendment 20 to Operating License DPR-41.

Amendment 20 added a new Paragraph 3.D as follows:

"D.

Steam Generator 0 eration Turkey Po3.nt Unit No.

4 shall be brought to a cold snutdown condition with'n 60 equivalent days of operation from December 3, 1976, unless the Nuclear Regulatory Commission grants prior approval for continued operation.

For the purpose of this requ're-ment, equivalent operation is defined as operation v'th a primary coolant temperature greater than 350'=."

Since December 3, F"orida Power

& Light Company (FPL) has sub-mitted considerable information on the subject of steam gener-atOr tube integrity as it applies to Turkey Point Units 3 and 4

(References 1-5).

The submittals were based o.. the results of extensive steam generator insp. ctions and ana'Iytical work performed by FPL and ilestinghouse Electric Corporation.

The most significant. results are summarized below:

(1)

Xntergranular stress-assisted cracking of steam generator tube U-berds has been confined to Row 1 tubes.

This has been verified by steam generator Eddy Current 'nspections and more detailed labora-tory examinations which have been performed for Turk y Point Units 3 and 4 and for other affected units.

There has been no evidence of interaranula cracking in the U-bends of tubes in rows other than Row l.

9.0<>5 PEOPLE... SERVING PEOPLE

To:

Re:

George Lear, NRC Turkey Point Unit 4 Docket No. 50-251 Steam Generator 0 eration January 21, 1977 Page (2)

(3)

FPL has initiated a program of preventive tube plugging, i.e., all Row 1 tubes in all 3 steam generators of both Turkey Point Units 3 and 4 have been plugged to preclude the possibility of tube leaks caused by intergranular cracking in the U-bends of those tubes.

Calculations performed by the steam generator manufacturer (Westinghouse) have shown that the U-bend strain levels in Rows 2 and beyond are signi-ficantly less'han the strain levels which resulted in cracking Row 1 tubes.

(4)

)

Assuming that flow slot hourglassing progressed until the slots were fully closed, the maximum strain imposed on any unplugged tube, (Note: all Row 1 tubes are plugged) would still be less than the strain im-posed on uncracked Row, 1 tubes.

In other words, the projected maximum strain for all tubes (excluding Row 1) will be less than a value that has been shown by laboratory examinations to be insufficient to cause cracking.

(5)

(6)

Analyses have been performed to evaluate the effects of full closure of the flow slots on the average tube denting rate, on shell integrity, and on the deforma-tion of the tube support plates and wrapper.

The analyses show that there are no significant adverse effects.

Projections of flow slot hourglassing show that con-tinued operation of Unit 4 until the next refueling (blay, 1977) vill result in less flow slot closure in the top support plate than has already been observed at Virginia Electric Power Company's (VEPCO) Surry Unit 1 and as stated previously where laboratory ex-aminations showed the absence of cracks in Rows 2

and 3 ~

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To:

Re:

George Lear, NRC Turkey Point Unit 4

Docket No. 50-251 Steam Generator 0 eration January 21, 1977 Page h Based on the foregoing, we conclude that, for the remainder of Cycle 3, flow slot deformation will not cause significant additional strain in theU-bends of tubes beyond Row 1, and the likelihood for the initiation of intergranular cracking in tubes beyond Row 1 is minimal.

Therefore, we request that you grant approval for continued operation of Turkey Point Unit 4 beyond the time limit specified in Amendment 20 to Operating License DPR-41.

A steam generator inspection program is being developed for use during the upcoming Unit 4 refueling.

The purpose of the program will be to provide further assuranc of the con-tinue'd integrity of the steam generator tubes in Row 2 and beyond.

Very truly yours, Vice President REU/i~IAS/hlc cc:

Norman C. Noseley, Region II Robert Lowenstein, Esq.

ATTACHNENT REFERENCES 1.

Letter L-76-431 (Unit 3 Steam'Generator Inspection Results) from Robert E. Uhrig (FPL) to George Lear (NRC) dated December 21, 1976.

J 2.

Letter L-76-432 (Units 3 and 4 Steam Generator Tube Integrity) from Robert E. Uhrig (FPL) to George Lear (NRC) dated December 22, 1976.

3.

Letter L-76-434 (Units 3 and 4 Steam Generator Tube Integrity Supplemental Information) from Robert E. Uhrig (FPL) to George Lear (NRC) dated December 30, 1976.

4.

Letter L-77-3 (Units 3 and 4 Steam Generator Tube Integrity Supplemental Information) from Robert E. Uhrig (FPL) to George Lear (NRC) dated January 3, 1977.

5.

Letter L-77-30 (Units 3 and 4 Steam Generator Tube Integrity Supplemental Information) from Robert E. Uhrig (FPL) to George Lear (NRC) dated January 21, 1977.

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