ML040750297

Steam Generator Tube Inspection Results

ML040750297
Person / Time
Site:	Braidwood
Issue date:	03/04/2004
From:	Mahesh Chawla NRC/NRR/DLPM/LPD3
To:	Bauer J Exelon Corp
Chawla M, NRR/DLPM, 415-8371
References
Download: ML040750297 (2)

Text

From: Mahesh Chawla To: Joseph.bauer@exeloncorp.com Date: 3/4/04 4:05PM

Subject:

Braidwood Station, Unit 1Steam Generator Tube Inspection Results By letters dated May 7, 2003 and July 29, 2003 , Exelon Generation Company, the licensee, submitted reports summarizing the steam generator tube inspections performed during the tenth refueling outage (April 2003) at Braidwood Station, Unit 1. The staff has reviewed the information the licensee provided with the submittal.

Based on the review of these documents, the staff has determined that following additional information is required in order to complete the evaluation. Please review these questions and and let me know your availability to have a teleconference. Please call me if you have any questions/comments at (301) 415-8371.

1. Various types of tube wear have occurred in Babcock and Wilcox recirculating steam generators including typical wear, localized fan bar wear (theorized to be a result of arch-bar distortion which affects specific columns of tubes), and atypical wear (attributed to asperities on the flat surfaces of the fan bar supports). For the indications of tube wear detected at Braidwood 1 at the fan bar and lattice grids, clarify the type of tube wear that is occurring at these locations.

2. The February 9, 2001 amendment request to extend the operating interval between inspections indicated that several tubes were in contact with other tubes and this condition is expected to naturally correct itself. Discuss the extent to which this condition (i.e., tube-to-tube contact) was monitored during your 2003 inspections. Discuss whether any tubes in contact were identified during the 2003 outage. If tubes in contact were identified, discuss whether the tubes were also in contact prior to placing the SG inservice. Discuss whether all tubes previously determined to be in contact were inspected in 2003. If all tubes known to be in contact were not inspected, discuss the basis for concluding that the structural and leakage integrity of the steam generators will be maintained at these locations until the next inspection.

3.The February 9, 2001 amendment request to extend the operating interval between inspections indicated that no foreign objects were known to be present in the steam generators.

For the loose parts that were identified during the 2003 outage, were these locations (i.e., the locations where the loose parts were detected in 2003) inspected (visually) during the inspections in 2000? The inspection results indicate wear on one tube proceeding to 48%

through-wall in the course of two operating cycles (or possibliy less), therefore, the staff requests a discussion on when these loose parts were introduced into the SG.

4.The steam generators at Braidwood 1 were replaced in 1998. Provide the following general design information: the manufacturer of the tubes, the thickness (axial extent) of the tube supports (fan bars and lattice grid), and the pitch and pattern (e.g., triangular) of the tubes.

Also, clarify the rows of tubes which were stress relieved after bending (i.e., what rows have bend radii less than or equal to 12-inches).

CC: Lauren Quinones; Louise Lund

Mail Envelope Properties (40479A1B.BD0 : 15 : 21352)

Subject:

Braidwood Station, Unit 1Steam Generator Tube Inspection Results Creation Date: 3/4/04 4:05PM From: Mahesh Chawla Created By: MLC@nrc.gov Recipients Action Date & Time owf4_po.OWFN_DO Delivered 03/04/04 04:05PM LNQ CC (Lauren Quinones) Opened 03/04/04 04:05PM exeloncorp.com Transferred 03/04/04 04:05PM joseph.bauer (Joseph.bauer@exeloncorp.com nrc.gov owf2_po.OWFN_DO Delivered 03/04/04 04:05PM LXL CC (Louise Lund) Opened 03/05/04 09:18AM Post Office Delivered Route owf4_po.OWFN_DO 03/04/04 04:05PM exeloncorp.com owf2_po.OWFN_DO 03/04/04 04:05PM nrc.gov Files Size Date & Time MESSAGE 3896 03/04/04 04:05PM Options Auto Delete: No Expiration Date: None Notify Recipients: Yes Priority: Standard Reply Requested: No Return Notification: None Concealed

Subject:

No Security: Standard To Be Delivered: Immediate Status Tracking: Delivered & Opened