05000413/LER-2010-002, Discovery of Reactor Coolant System Pressure Boundary Leak at Thermowell 1NCTW5850 Seal Weld
| ML101120662 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 04/20/2010 |
| From: | Morris J Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 10-002-00 | |
| Download: ML101120662 (10) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded |
| 4132010002R00 - NRC Website | |
text
JAMES R. MORRIS Ener
,Vice President t9hEnergyo aab ula tto Duke Energy Catawba Nuclear Station 4800 Concord Rd.
York, SC 29745 803-701-4251 803-701-3221 fax April 20, 2010 U.S. Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, D.C. 20555
Subject:
Duke Energy Carolinas, LLC Catawba Nuclear Station, Unit 1 Docket Nos. 50-413 Licensee Event Report 413/2010-02, Revision 0 Problem Investigation Process No. C10-01020 Attached is Licensee Event Report (LER) 413/2010-002 Revision 0 entitled "Discovery of Reactor Coolant System Pressure Boundary Leak at Therrnowell 1 NCTW5850 Seal Weld".
This report is being submitted in' accordance with 10 CFR 50.73 (a)(2)(ii)(A),
"Degraded or Unanalyzed Condition." This event is considered to be of no significance with respect to the health and safety of the public. There are no regulatory commitments contained in this LER.
If questions arise regarding this LER, contact Phil Barrett at 803-701-4138.
Sincerely, James R. Morris Attachment www. duke-energy com
U.S. Nuclear Regulatory Commission April 20, 2010
.Page 2 cc:
L. A. Reyes Regional Administrator, Region II U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, Georgia 30303-1257 J. H. Thompson Project Manager (Catawba)
U.S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852-2738 Mail Stop 0-8 G9A G. A. Hutto, III NRC Senior Resident Inspector Catawba Nuclear Station INPO Records Center 700 Galleria Place Atlanta, GA 30339-5957
U.S. Nuclear Regulatory Commission April 20, 2010 Page 3 bxc:
(electronic copy) (with attachment):
INPO K.W. Phillips R.D. Hart G.Y. Helton S.F. Hatley (EPIX)
M.K. Green D.R. Brenton S. L. Nader A.M. Peterman R.G. Hull T.W. King H.D. Brewer K. R. Alter K.L. Ashe B.J. Horsley M.J. Brown bxc (hard copy) (with attachment):
L.F: Vaughn G.F. Winkel P.W. Barrett Master File CN-801.01 ELL LER File RGC Date File NCMPA-1 NCEMC PMPA lerevents@inop.org
Abstract
Event Description
On February 18, 2010, with the unit in Mode 4, a
reactor coolant pressure boundary leak was identified at the 1A reactor coolant hot leg thermowell 1NCTW5850 seal weld.
A cool down to Mode 5 was initiated.
Unit Status: At the time of the event, Unit 1 was in Mode 4 at 0% power.
Power had been reduced to perform an inspection in containment to identify the source of primary leakage.
Event Cause
The cause of the failed seal weld was inadequate weld control when the weld was fabricated during initial construction. The weld failure resulted from the presence of a discontinuity involving a metal removal process. Applied loads, primarily pressure loads (high strain -
low cycle fatigue) to the weakened area (i.e.
location metal removed) contributed to the seal weld failure.
Corrective Actions
After reducing primary system pressure, additional weld passes were applied at the seal weld associated with the mechanical joint located between the weld boss and the thermowell.
Visual examination of the other three Unit 1 hot leg RTD thermowells concluded no sign of leakage.
NRC FORM 366 (7-2001)
(If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A)
ADDITIONAL INFORMATION
To determine if a recurring or similar event exists, a search of Catawba's three year history was conducted.
There have been no reportable events with respect to failures of the NC system pressure boundary.
This event does not constitute a Safety System Functional Failure.
Adaptor and RTD instrument are not shown.
Thermowell
/
Seal Weld Helicoil Location of originally specified 0-ring Weld Boss 1.65" NRC FORM 366 (7-2001)