ML20135C142

Submits Second RAI Re Proposed Extension of 3.0 Volt Lower Repair Limit for Another Operating Cycle for Plant,Unit 1

ML20135C142
Person / Time
Site:	Byron, Braidwood
Issue date:	02/27/1997
From:	Lynch M NRC (Affiliation Not Assigned)
To:	Johnson I COMMONWEALTH EDISON CO.
References
TAC-M964500, TAC-M964501, TAC-M96498, TAC-M96499, NUDOCS 9703030380
Download: ML20135C142 (5)

Text

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February 27, 1997 T5 G i

, Ms. Irene Johnson, Acting Manager Nuclear Regulatory Services

, Commonwealth Edison Company Executive Towers West III 1400 Opus Place, Suite 500 Downers Grove, IL 60515

SUBJECT:

SECOND REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE PROPOSED l I

EXTENSION OF THE 3.0 VOLT LOWER REPAIR LIMIT FOR ANOTHER OPERATING CYCLE'FOR BYRON 1 AND BRAIDWOOD 1 (TAC N05. M96498, M96499, M96500 AND M96501)

Dear Ms. Johnson:

l The staff has reviewed your responses :n your letter dated February 5,1997,

, to the first eleven questions in our first request for additional information (RAI) transmitted in our letter dated January 27, 1997. The first RAI was related to your request to extend, for one more operating cycle, the voltage-based repair criteria incorporated into the Byron 1 and Braidwood 1 Technical Specifications (TS) by the license amendments issued on November 9,1995.

Specifically, these amendments raised the value of the lower voltage repair limit for a form of steam generator (SG) tube degradation identified as primarily. axially-oriented outer diameter stress corrosion cracking (0DSCC) from 1.0 volt to'3.0 volts. Our review has identified the need for a second RAI on this subject. The RAI in the enclosure to this letter is related to certain aspects of your proposed criteria for assessing the. scope of the forthcoming eddy current inspection (ECI) at Braidwood 1 presently scheduled to start in late March 1997. This second RAI would also be applicable to.

Byron 1 if the Byron 1 SG replacement program is delayed past December 1997.

If you have any questions on these matters, please contact me at (301) 415-3023.

Sincerely, g g Q % h ORIGINAL SIGNED BY:

M. David Lynch, Senior Project Manager Project Directorate III-2 Division of Reactor Projects - III/IV

. Office of Nuclear Reactor Regulation Docket.Nos. STN 50-454, STN 50-456

Enclosure:

RAI cc w/ encl: see next page Distribution: ' Docket File PUBLIC PDIII-2 R/F J. Roe JWR E. Adensam EGAl R. Capra J. Strosnider 07D4

'C. Moore M. D. Lynch OGC 015B18 R. Lanksbury,RIII ACRS T2E26 G. Dick R. Assa C. Beardsley 0704 K. Karwoski 07D4 S. Coffin 07D4 S. Bailey E. Sullivan 07D4 i P. Rush 0704 DOCUMENT NAME: BB96498.RAI Omii I

Ta receive a copy of this document, indicateAthe bog: "C" = Copy without enclosures *E" = Copy with enclosures *N" = No copy 0FFICE PM.j lO l R.AjRQDI-2 l L.- 9:PDIII-313 fil E NAME , Cs:: K tMdOREA LRCAPRA ()M DATE 02/27/97 '

02// /97 '[12/)7/97" 0FFICI AL' RECORD COPY 9703030380 970227 PDR ADOCK 05000454 P PDR

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I.-Johnson Byron /Braidwood Power Stations Commonwealth Edison Company cc: l Mr. William P. Poirier, Director George L. Edgar Westinghouse Electric Corporation Morgan, Lewis and Bochius Energy Systems Business Unit 1800 M Street, N.W.

Post Office Box 355, Bay 236 West Washington, DC 20036 Pittsburgh, Pennsylvania 15230 Attorney General  !

Joseph Gallo 500 South Second Street Gallo & Ross Springfield, Illinois 62701 1250 Eye St., N.W.

Suite 302 EIS Review Coordinator Washington, DC 20005 U.S. Environmental Protection Agency 77 W. Jackson Blvd.

Michael I. Miller, Esquire Chicago, Illinois 60604-3590 Sidley and Austin One First National Plaza Illinois Department of Chicago, Illinois 60603 Nuclear Safety Office of Nuclear Facility Safety Howard A. Learner 1035 Outer Park Drive Environmental law and Policy Springfield, Illinois 62704 Center of the Midwest 203 North LaSalle Street Commonwealth Edison Company Suite 1390 Byron Station Manager Chicago, Illinois 60601 4450 North German Church Road Byron, Illinois 61010 U.S. Nuclear Regulatory Commission Byron Resident Inspectors Office Kenneth Graesser, Site Vice President 4448 North German Church Road Byron Station Byron, Illinois 61010-9750 Commonwealth Edison Station 4450 N. German Church Road Regional Administrator, Region III Byron, Illinois 61010 U.S. Nuclear Regulatory Commission 801 Warrenville Road U.S. Nuclear Regulatory Commission Lisle, Illinois 60532-4351 Braidwood Resident Inspectors Office Rural Route #1, Box 79 Ms. Lorraine Creek Braceville, Illinois 60407 Rt. 1, Box 182 Manteno, Illinois 60950 Mr. Ron Stephens Illinois Emergency Services Chairman, Ogle County Board and Disaster Agency Post Office Box 357 110 East Adams Street Oregon, Illinois 61061 Springfield, Illinois 62706 Mrs. Phillip B. Johnson Chairman 1907 Stratford Lane Will County Board of Supervisors l Rockford, Illinois 61107 Will County Board Courthouse Joliet, Illinois 60434 i

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Commonwealth Edison Company Braidwood Station Manager Rt. 1, Box 84 Bracev111e, Illinois 60407 Ms. Bridget Little Rorem Appleseed Coordinator 117 North Linden Street Essex, Illinois 60935 ,

Document Control Desk-Licensing Commonwealth Edison Company 1400 Opus Place, Suite 400 Downers Grove, Illinois 60515 Mr. H. G. Stanley Site Vice President Braidwood Station Commonwealth Edison Company RR 1, Box 84 Braceville, IL 60407 i

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p REQUEST FOR ADDITIONAL"INFORMATION-

. e RELATED TO THE EXTENSION OF THE 3.0 VOLT LOWER VOLTAGE REPAIR LIMIT FOR ODSCC

. BYRON 1 AND BRAIDWOOD 1 DOCKET NOS. STN 50-454 AND STN 50-456 .i J

1. In your response dated February 5, 1997, to Question 7.of our request -i for additional information (RAI) issued on January 27, 1997, Comed stated that if an axial indication was found in a steam generator (SG) j tube at the top of the tubesheet or at an expansion joint at the tube  ;

support plates (TSP), in one of the 21 expanded SG tubes in each of the  ;

four SGs at Byron 1 and Braidwood 1, the scope of the eddy current i inspection (ECI) would not be expanded. These 21 expanded tubes act as '

l additional tie rods supporting the TSPs under SG blowdown loads which i would occur following a postulated main steamline break (MSLB) and are an important element in the staff's decision to issue on November 9, 1995, the Byron 1 and Braidwood 1 license amendments incorperating.the l lower voltage repair limit of 3.0 volts into the Byron 1 and Braidwood 1  !

Technical Specifications (TS). Specifically, the staff's review of the I license amendments cited above, focused on the importance of the structural integrity of these additional 21 tie rods. Comed's position on this particular issue is that the presence of axial indications found in an ECI would not result in a TSP displacement exceeding 0.10 inches.

This is the value which was assumed in your evaluati,on of the SG tube burst probability under postulated accident conditions as well as your evaluation of potential SG tube leakage.

While this' statement regarding TSP displacement may be true in itself, your response to Question 7 cited above does not address the need to expand the scope of the ECI as a result of identifying a potentially active stress corrosion process. The staff concern in this matter is that if an active stress corrosion process is occurring in one of the 21 expanded SG tubes acting as a tie rod, there is an increased potential for a circumferential indication to be developing in one of the expanded tie rods not chosen for inspection. Accordingly, discuss your plans for expanding the scope of your ECI in light of this particular staff concern.

2. In your response to Question 9 of our RAI dated January 27, 1997, Comed' I indicated the conditions which would cause it.to calculate the conditional failure probability of axial burst.

Specifically, Comed  !

stated that either about 250. axial indications in the 10 to 15 volt ,

range or one axial indication greater than 15 volts, would need to be '

identified before calculating this particular conditional failure probability. However, your projections for the forthcoming end-of-cycle A.

ENCLOSURE

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, (E0C) distribution of voltages include adjustments for: (a) the probability of detection (P0D) in an ECI; (b) flaw growth estimates determined from previous ECIs; and (c) non-destructive examination (NDE) uncertainty associated with an ECI. The staff believes that the net effect of these three adjustments is to provide a conservative estimate of the EOC voltage distributions.

3 Accordingly, it is not' clear to the staff that your proposed subject I

criteria are conservative. More importantly, if the licensee were to find on the order of one to five axial indications in the range of 10 to

, 15 volts during a forthcoming ECI, the ' staff would have serious concerns about the applicability of the methodology used to estimate the E0C ,

voltage distribution given that a very limited number of indications is expected to be found in this voltage range if this methodology is sufficiently conservative. Accordingly, discuss your proposed subject

- criteria in light of this particular staff concern.  ;

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