ML20195G446

Discusses FPC 980518 Submittal of Operational Assessment of Once Through SG Tube Degradation at CR-3 in Accordance with License Commitment Submitted on 971207

ML20195G446
Person / Time
Site:	Crystal River
Issue date:	11/17/1998
From:	Wiens L NRC (Affiliation Not Assigned)
To:	Cowan J FLORIDA POWER CORP.
References
TAC-MA2071, NUDOCS 9811200307
Download: ML20195G446 (6)

Text

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l [pc(% 4 UNITED STATES i i g j NUCLEAR REGULATORY COMMISSION g WASHINGTON, D.c. 2006t4001

% , / tbwriber 17, 1998 Mr. John Paul Cowan Vice President, Nuclear Operations Florida Power Corporation -

ATTN: Manager, Nuclear Licensing (SA2A)

Crystal River Energy Complex 15760 W. Power Line Street sCrystal River, Florida 34428-6708 i

SUBJECT:

l STAFF EVALUATION OF OPERATIONAL ASSESSMENT OF STEAM GENERATOR TUBE DEGRADATION AT CRYSTAL RIVER UNIT 3 l (TAC NO. MA2071)

References:

1. Letter from Florida Power Corporation (FPC) to Document Control Desk (NRC), dated May 18,1998,"An Operational Assessment of Steam j Generator Tube Degradation at Crystal River Unit 3."

2. Letter from Florida Power Corporation (FPC) to Document Control Desk (NRC), dated December 5,1997, "Special Report 97-05 Once Through Steam Generator (OTSG) Notifications Required Prior to MODE 4, and Complete Results of OTSG Tube Inservice Inspection Performed during' the Current Outage (90-Day Report)."

l 3. Letter from Florida Power Corporation (FPC) to Document Control Desk l (NRC), dated September 14,1998,"SupplementalInformation to Assist NRC Staff's Review of Operational Assessment of Steam Generator Tube Degradation at Crystal River Unit 3 (TAC No. MA2071)."

4. Letter from L. Raghavan (NRC) to R. A. Anderson (FPC), dated

! October 28,1997, " Crystal River Unit 3 - Staff Evaluation and issuance of Amendment RE: Steam Generator Tube Intergranular Attack Degradation (TAC No. M98262)."

Dear Mr. Cowan:

t L By letter dated May 18,1998, (Reference 1) Florida Power Corporation (FPC) submitted an l operational assessment of once through steam generator (OTSG) tube degradation at Crystal River Unit 3 (CR-3)in accordance with a license commitment FPC submitted on December 7,1997 (Reference 2). Clarifying information conceming the assessment was provided in a letter dated September 14,1998 (Reference 3).

The Nuclear Regulatory Commission staff has reviewed the operational assessment with particular emphasis on the assessment of pit like intergranular attack (IGA) located in the first span of the "B" OTSG. During its last inspection of the OTSG tubes in June 1997, FPC applied a qualified eddy current inspection technique to disposition tubes exhibiting this degradation mode in accordance with its Technical Specifications (i.e., tubes with indications sized at depths of 40% throughwall or deeper were plugged). As discussed in the staff's safety evaluation related (

to Amendment No.158 dated October 28,1997 (Reference 4), sizing the depth of IGA g 9811200307 981117  ?

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J.P.Cowan 1 degradation from eddy current inspection data is a unique application of eddy current technology and is different from the approach used by other utilities. The general practice employed by other pressurized water reactor licensees is to plug all tubes with indications of IGA degradation regardless of the depth estimate provided by eddy current inspection data. Because of the unique application, FPC committed to additional reporting requirements, such as the subject operational assessment, that provide the staff a vehicle by which to monitor the tubes left in service at CR-3 with indications of pit-like IGA.

In Reference 1, FPC provided the results of its growth assessment of the "B" OTSG first span l pit-like IGA indications. It was stated in the submittal that based on the 1997 eddy current i

inspection results, the growth distributions are centered about the zero point, as has been observed in the past. FPC thus concluded that the majority ofindications are not exhibiting any discernable growth s in Reference 2, FPC provided the results of its deterministic operational assessment for pit-like IGA degradation. First, FPC determined the maximum dimensions of volumetric degradation allowable that will still provide the required structural and leakage integrity under norme' operating and accident conditions. These dimensions were obtained using standard e 'ineering equations and 95/95 lower tolerance limit tensile pro erties. FPC calculated that a m ,ium i length (in either the axial or circumferential direction) of 0.64 inches ccmbined with a i ximum depth of 66% throughwall will maintain structural and leakage integrity. In the most t 'nt CR-3 "B" OTSG eddy current inspection of the tubes, the maximum linear extent of first spar pit-like i

IGA was 0.30 inches. At this length, the allowable maximum depth increases to 74%

throughwall. Using a maximum depth of 39% throughwall for an indication left in service plus the 95th percentile depth measurement error of 16% leads to an allowance for growth over the

, current cycle of 19% throughwall. As discussed above, there is essentially no growth of IGA indications.

The staff has prepared draft guidelines, DG-1074, " Steam Generator Tube Integrity," which include guidelines for performing operational assessments. The staff expects to issue DG-1074 for public comment sometime around the end of 1998. DG-1074 recommends that the most limiting projected flaw should not result in safety factors less than those consistent with the ASME Code, Section Ill. The safety factor estimates should consider all significant uncertainties affecting the estimates such that the estimates are lower bound estimates with a probability of 0.95 evaluated at the 95% confidence level. The licensee did not rigorously address uncertainties (e.g., measurement uncertainties, analyst variability, etc.) to the degree recommended in DG-1074. Nevertheless, based on past inspection results, the estimates performed and the large margins estimated to exist relative to the Code margins, the staff believes that a more rigorous treatment of uncertainties would not affect the assessment l

conclusions; namely, the projected most limiting flaw is expected to exhibit safety margins consistent with the ASME Code.

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e J.P.Cowan .

Please contact me at (301) 415-1495 if you have questions conceming the staff's review. This completes the staff efforts under TAC No. MA2071.

Sincerely:

a Leonard A. Wiens, Senior Project Manager Project Directorate - 1/11 Division of Reactor Projects 1/11 Office of Nuclear Reactor Regulation Docket No. 50-302 cc: See next psge a

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i- Noveter 17, 1998

'J.P.Cowan Please contact me at (301) 415-1495 if you have questions concerning the staff's review. This completes the staff efforts under TAC No. MA2071. .

- Sincerely:

Original . signed by:

Leonard A. Wiens, Senior Project Manager Project Directorate 11-3 l Division of Reactor Projects - t/II Office of Nuclear Reactor Regulation Docket No. 50-302 l

cc:- See next page DISTRIBUTION .

N7 PUBLIC -

Crystal River r/f -

JZwolinski FHebdon.

LWiens BClayton OGC ACRS LPlisco, Ril SCoffin EMurphy DOCUMENT NAME: G:\ CRYSTAL \0TSG0 PAS.WPD To receive a copy of this document, indicate in the box: "C" = Copy without attachment / enclosure "E" =

Copy with attachment / enclosure "No a No c( W OFFICE PDil 3/PM j__ lC PDil 3/LA ,, l PDII-3/D ,1 l Cl NAME LWiens:cw / / x / BClayton A\fiF FHebdon M DATE 11////98W '- 11/i1 /98 11/l'7/98I 11/ /98 0FFICIAL RECORD COPY l

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-( Nowrt)er 17, 1998 J.P.Cowan .

Please contact me at (301) 415-1495 If you have questions concerning the staff's review. This completes the staff efforts under TAC No. MA2071.

Sincerely:

i Original signed by:

Leonard A. Wiens, Senior Project Manager Project Directorate 11-3 Division of Reactor Projects - 1/11 l Office of Nuclear Reactor Regulation Docket No. 50-302

, cc: See next page DISTRIBUTION Docket File a PUBLIC Crystal River r/f -

JZwolinski FHebdon LWiens BClayton OGC I ACRS LPlisco, Rll SCoffin EMurphy DOCUMENT NAME: G:\ CRYSTAL \0TSG0 PAS.WPD To receive a copy of this document, Indicate in the box: "C" = copy without attachment / enclosure "E" "

Copy with attachment / enclosure "N" = No copy OFFICE PDII 3/PM j __ lC PDil 3/LA , , l PDII 3/D ,) l Cl I NAME LWiensscw //g u / BClayton MV FHebdon T DATE 11/// /98W' 11/t1 /98 11/\"7/98 11/ /98 1 OfflCIAL RECORD COPY

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Mr. John Paul Cowan CRYSTAL RIVER UNIT NO. 3 Florida Power Corporation GENERATING PLANT J t

cc:

l Mr. R. Alexander Glenn Chairman Corporate Counsel .

Board of County Commissioners Florida Power Corporation Citrus County MAC-ASA '110 North Apopka Avenue P.O. Box 14042 Invemess, Florida 34450-4245 St. Petersburg, Florida 33733-4042 Mr. Robert E. Grazio, Director Mr. Charles G. Pardee, Director ' Nuclear Regulatory Affairs (SA2A)

Nuclear Plant Operations (NA2C) Florida Power Corporation Florida Power Corporation Crystal River Energy Complex Crystal River Energy Complex - 15760 W. Power Line Street 15760 W. Power Line Street Crystal River, Florida 34428-6708 Crystal River, Florida 34428-6708 Senior Resident inspector Mr. Robert B. Borsum - Crystal River Unit 3

- Framatome Technologies Inc. U.S. Nuclear Regulatory Commission 1700 Rockville Pike, Suite 525 6745 N. Tallahassee Road

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Rockville, Maryland 20852 Crystal River, Florida 34428 .

s l- Mr. William A. Passetti, Chief Mr. Gregory H. Hainon i l Department of Health '

Director, Quality Programs (SA2C) 4 Bureau of Radiation Control Florida Power Corporation 2020 Capital Circle, SE, Bin #C21 Crystal River Energy Complex

' Tallahassee, Florida 32399-1741 15760 W. Power Line Street Crystal River, Florida 34428-6708

- Attomey General

- Department of Legal Affairs Regional Administrator, Region !!

' The Capitol U.S. Nuclear Regulatory Commission Tallahassee, Florida 32304 61 Forsyth Street, SW., Suite 23T85 Mr. Joe Myers, Director

Division of Emergency Preparedness Mr. Leonard D. Wert Department of Community Affairs U.S. Nuclear Regulatory Commission 2740 Centerview Drive 61 Forsyth Street, SW., Suite 23T85 Tr.:lahassee, Florida 32399-2100 Atlanta, GA 30303-3415 L

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