ML20140H559

Discusses Evaluation of Core Spray Piping Indications During Refueling Outage 17.Staff Review for TAC M95141 Completed

ML20140H559
Person / Time
Site:	Cooper
Issue date:	05/09/1997
From:	Hall J NRC (Affiliation Not Assigned)
To:	Horn G NEBRASKA PUBLIC POWER DISTRICT
References
TAC-M95141, NUDOCS 9705130181
Download: ML20140H559 (5)

Text

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[/ k UNITED STATES Q 999 j.

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t NUCLEAR REGULATORY COMMISSION l WASHINGTON. D.C. 30806-0001 4

9***** May 9, 1997

) Mr. G. R. Horn

! Sr. Vice President of Energy Supply i f Nebraska Public Power District  ;

i 1414 15th Street '

l Columbus, NE 68601 i

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SUBJECT:

COOPER NUCLEAR STATION - EVALUATION OF CORE SPRAY PIPING INDICATIONS

! DURING REFUELING OUTAGE 17 (TAC NO. M95141) i

Dear Mr. Horn:

1

[ -By letter dated May 7, 1997, the Nebraska Public Power District (NPPD)

provided the staff with the results of your re-examination of three

! indications on the core spray piping at the Cooper Nuclear Station (CNS).

i The three indications had been previously identified during the 1995 refueling

i. outage. By letter dated December 21, 1995, the Nuclear Regulatory Commission i (NRC) staff approved your flaw evaluations of those indications, and also a

approved plant operation for one fuel cycle without repair of the subject j flaws. In that letter, the staff stipulated that continued operation beyond one cycle should be supported by re-inspection and re-evaluation of the j indications in accordance with the requirements of American Society of Mechanical Engineers (ASME) Code,Section XI, 1989 Edition.

I By letter dated November 27, 1996, NPPD notified the NRC that future l

inspections of the core spray spargers and piping would be performed in  ;

i <ccordance with the Boiling Water Reactor Vessel Internals Project guidelines i contained in EPRI Report TR-106740, dated July 1996, "BWR Vessel and Internals  !

! Project, Core Spray Internals Inspection and Flaw Evaluation Guidelines  !

i (BWRVIP-18)." The visual and ultrasonic (UT) re-examinations of the  !

j previously identified flaws were performed in accordance with this guidance '

during the current refueling outage (RFO-17).

In your letter of May 7,1997, you reported the following results: 0

Projected length Maximum /  !

j Weld Length - 1995 Length - 1997 at end of next Allowable ry' 'D )

Number results (in.) results (in.1 cycle (in.) flaw size i l j Al 8.9 9.1 10.3 11.8 A21 5.5 5.6 6.8 11 8 l

B12 1.5 NA NA 10.7 5

130058 9705130181 970509 PDR G

ADOCK 05000298 PDR N

Ibi (hhk

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Mr. G. R. Horn In 1995, the apparent indication in the area of the C12 weld was based on a visual examination, which could not be confirmed by UT examination at the time. Your re-examination of that area during RFO-17 failed to identify any flaws, and you have concluded that the previously identified indication in that area is non-relevant. You further concluded that the slight increases i i

reported in the lengths' of the indications seen in the areas of the Al and A21 )

welds may have resulted from differences in UT examination methods, or from l crack growth. If the increases are attributed to crack growth, you concluded 1 that the actual growth rate has been significantly less than the bounding rate l assumed in your previous analyses provided in your letters of November 22 and l December 18, 1995. You further concluded that the fracture mechanics evaluation submitted in those letters is still applicable, based on the absence of significant growth in the indications, and that the Code allowable flaw sizes will not be exceeded during an additional cycle of operation. You also committed to re-examine the two relevant indications using the BWRVIP-18  :

guidance at the next refueling outage. l The NRC staff has reviewed your letter of May 7,1997, and concludes that the i previous analyses and assumptions accepted in our letter dated December 21, l 1995, are applicable to the current indications, due to the limited crack l growth observed over the past cycle. Therefore, we conclude that the flaw j sizes at the end of the next fuel cycle will not exceed the critical flaw '

sizes cciculated using the methodologies and the teceptance criteria provided in IWB-3640 and Appendix C of the ASME Boiler and Pressure Vessel Code,Section XI, and that CNS can be safely operated for an additional fuel cycle without re) air of the flaws in the areas of the Al and A21 welds. Plant operation )eyond the next fuel cycle should again be supported by the results of re-inspection and re-evaluation of the indications, consistent with the <

commitments in your May 7, 1997, letter. '

In our letter of December 21, 1995, the staff requested you to provide an evaluation of the potential effects of reduced core spray flow due to leakage through the identified cracks, which were conservatively assumed to be through-wall. In addition, you were requested to evaluate the potential impact of loose parts resulting from a break of the core spray line t.t the identified crack locations. The staff has reviewed your evaluation of those potential effects, provided by letter dated March 29, 1996, and has concluded that these effects would result in a negligible increase in the peak cladding l temperature calculated for the Cooper Nuclear Station. However, this review was based on the crack lengths reported in 1995 and on the Maximum Average l Planar Linear Heat Generation Rates for the past fuel cycle. You are ,

therefore requested to submit for staff review an updated analysis to confirm l that these conclusions are valid for the next fuel cycle. This submittal is j requested within 3 months of plant restart from the current refueling outage. .

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t Mr. G. R. Horn ,

This completes the NRC staff review for TAC No. M95141. If you have any questions'regarding this issue, please contact me at (301) 415-1336.

Sincerely,

) ()

.nntL '

@mes R. Hall, Senior Project Manager .

froject Directorate IV-1 l

bivision of Reactor Projects III/IV Office of Nuclear Reactor Regulation i

Docket No. 50-298 cc: See next page f

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t i Mr. G. R. Horn t This completes the NRC staff review for TAC No. M95141. If you have any questions regarding this issue, please contact me at (301) 415-133C.

Sincerely, ORIGINAL SIGNED BY:

James R. Hall, Senior Project Manager Project Directorate IV-1 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket No. 50-298 l cc: See next page '

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i DISTRIBUTION:

-Docket File PUBLIC PD4-1 r/f J. Roe C. Hawes ACRS OGC (15B18) T. Gwynn, RIV J. Hall E. Adensam (EGAl) J. Strosnider K. Wichman i Document Name: C0095141.LTR i 0FC PM/PD4-1,,,1 LA/PD4-1 EMCB NAME JHall/vw[ CHawes UTld hh DATE 5/7/97 5/9 /97 5/9/97 0FFICIAL RECORD COPY

, _ _. _ _ _ _ _ . _ . _ _ _ _ . . . _ . - . _ - . - ~ _ . _ _ _ . _ . _ _ _ . _ -

et i Mr. G. R. Horn Nebraska Public Power Company Cooper Nuclear Station

CC

' Mr. John R McPhail, General Counsel Lincoln Electric System Nebraska Public Power District ~ ATTN: Mr. Ron Stoddard P. O. Box 499 lith & 0 Streets Columbus, NE 68602-0499 Lincoln, NE 68508 i

Nebraska'Public Power District Midwest Power  !

ATTN: Mr. P. D. Graham ATTN: Richard J. Singer, Manager-Nuclear j Vice President of Nuclear Energy 907 Walnut Street

• P. O. Box 98 P. O. Box 657 l Brownville, NE 68321 Des Moines, IA 50303 Randolph Wood, Director Nebraska Department of Environmental Nebraska Public Power District Control ATTN: Mr. B. L. Houston, Nuclear -

P. O. Box 98922 Licensing & Safety Manager Lincoln, NE 68509-8922 P. O. Box 98 Brownville, NE 68321 Mr. Larry Bohlken, Chairman Nemaha County Board of Commissioners  ;

- Nemaha County Courthouse l 1824 N Street '

Auburn, NE 68305 Senior Resident Inspector- 1 U.S. Nuclear Regulatory Commission l P. 0. Box 218 Brownville, NE 68321

]

- Regional Administrator, Region IV  !

. U.S. Nuclear Regulatory Commission j 611 Ryan Plaza Drive, Suite 1000 t Arlington, TX 76011 Ms. Cheryl Rogers, LLRW Program Manager Division of Radiological Health Nebraska Department of Health 301 Centennial Mall, South i P. O. Box 95007 I Lincoln, NE 68509-5007 l

- Mr. Ronald A. Kucera, Department Director of' Intergovernmental Cooperation Department of Natural Resources P.O. Box 176 Jefferson City, M0 65102 I