05000369/LER-2010-001, Regarding Power Reduction of Two Units Due to Entry Into LCO 3.0.3 Caused by the Inoperability of Both Trains of the Control Room Area Chilled Water System
| ML100820284 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 03/11/2010 |
| From: | Repko R Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 10-001-00 | |
| Download: ML100820284 (10) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3692010001R00 - NRC Website | |
text
REGIS T. REPKO Vice President drGEnergyo McGuire Nuclear Station Duke Energy MG01 VP / 12700 Hagers Ferry Rd.
Huntersville, NC 28078 980-875-4111 980-875-4809 fax regis. repko@duke-energy, com March 11,2010 U.S. Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, D.C. 20555
Subject:
Duke Energy Carolinas, LLC McGuire Nuclear Station, Units 1 and 2 Docket Nos. 50-369, 50-370 Licensee Event Report 369/2010-01, Revision 0 Problem Investigation Process No. M-10-00185 Pursuant to 10 CFR 50.73 Sections (a)(1) and (d), attached is Licensee Event Report (LER) 369/2010-01, Revision 0, regarding the power reduction on both operating units due to entry into Technical Specifications Limiting Condition for Operation (LCO) 3.0.3 caused by the inoperability of both trains of the Control Room Area Chilled Water System.
This report is being submitted in accordance with 10 CFR 50.73 (a)(2)(i)(B),
"Operation or Condition Prohibited by Technical Specifications." 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 Lee A. Hentz at 980-875-4187.
Sincerely, Regis T. Repko Attachment www. duke-energy. com
'*i i'lii*i! !.*I U.S. Nuclear Regulatory Commission March 11, 2010 Page 2 cc:
L. A. Reyes Administrator, Region II U.S. Nuclear Regulatory Commission Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, GA 30303 J. H. Thompson Project Manager (McGuire)
U.S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852-2738 Mail Stop 0-8 G9A J. B. Brady NRC Senior Resident Inspector McGuire Nuclear Station B. 0. Hall, Section Chief North Carolina Department of Environment and Natural Resources Division of Environmental Health Radiation Protection Section 1645 Mail Service Center Raleigh, NC 27699-1645
Abstract
Unit Status: At the time of the event, Units 1 and 2 were in Mode 1 at 100%
power.
Event Description
On January 12, 2010, while performing annual maintenance on the "A" Control Room Area Chilled Water System (CRACWS)
- chiller, the "B" CRACWS chiller developed a refrigerant leak on the hot gas bypass piping and was declared inoperable.
With both trains of CRACWS inoperable, both McGuire units entered Technical Specification Limiting Condition for Operation (LCO) 3.0.3 and initiated a shutdown of both units.
Following a temporary repair to the "B" chiller, McGuire requested and received a Notice of Enforcement Discretion (NOED) and terminated the two unit shutdown.
Event Cause
The cause of the "B" CRACWS chiller hot gas. bypass piping leak was vibration produced by normal chiller operation.
Contributing to the leak was additional vibration produced by a 2007 chiller controls modification, piping corrosion, and residual piping stresses produced by a 2009 base metal weld repair.
Corrective Actions
Replace the hot gas bypass, piping on both CRACWS chillers.
Reduce the piping vibration on the CRACWS chillers to acceptable levels.
Inspect and coat the chiller piping susceptible to corrosion.
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 (if more space is required, use additional copies of NRC Form 366A)
But several events. were identified as missed opportunities that could have flagged site personnel to the extent of the vibration of the "B" CRACWS chiller hot gas bypass piping.
PIP M-01-3554 documents an instance where the vendor supplied hot gas bypass valve actuator had become disconnected from the valve on the "B" CRACWS chiller due to significant vibration.
This vibration was listed as one of the causes for the. loosening of the actuator mounting bolts, but no corrective actions were developed to identify or reduce the vibration.
- - In 2007, the chiller controls modifications also replaced the hot gas bypass valve and actuator on both chillers.
But the modifications did not evaluate the adverse affects of the new actuator weight and orientation to the piping system.
PIP M-09-00966 documents a refrigerant leak on the "B" CRACWS chiller caused by pre-existing flaws and cyclic stresses.
Corrective actions
were created to obtain resonance data on the hot gas bypass piping systems of the "A" and "B" CRACWS chillers but not a full spectrum of vibration data* with the chillers in operation.
Full spectrum vibration data could have identified the excessive vibration levels.
PIP M-09-7675 documents a refrigerant.leak on the "B" CRACWS chiller hot gas bypa.ss elbow.
Site personnel at the time did not fully evaluate the potential failure modes of this leak which could have led to piping replacement versus the base metal weld repair option.
The weld repair option was influenced by the unavailability of replacement components and concerns over the unavailability time of the "B" CRACWS chiller.
The base metal weld repair aggravated an existing, but, unknown at the time, flaw.
NRC FORM 366 (7-2001)