05000499/LER-2006-001, Regarding Safety Injection Train Inoperable Longer than Allowed Under Technical Specifications
| ML070370323 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 01/31/2007 |
| From: | Coates K South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NOC-AE-07002105 LER 06-001-00 | |
| Download: ML070370323 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4992006001R00 - NRC Website | |
text
Nuclear Operating Company South Texas Project Electric Generating Station PO. Box289 Wdsworth, Texas 77483 January 31, 2007 NOC-AE-07002105 File No.: G25 10 CFR 50.73 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 South Texas Project Unit 2 Docket No. STN 50-499 Licensee Event Report 2-06-001 Safety Iniection Train Inoperable Longer Than Allowed Under Technical Specifications Pursuant to 10 CFR 50.73, the STP Nuclear Operating Company (STPNOC) submits the attached Unit 2 Licensee Event Report 2-06-001 to address an incident of failure to restore safety injection Train A to service in the time required by Technical Specifications.
High head safety injection pump 2A was declared inoperable at 0100 on November 27, 2006, due to maintenance requirements; this also made the associated low head safety injection and containment spray pumps inoperable. The allowed outage time expired at 0100 on December 4, 2006. Because the time for repairs was expected to exceed that time, STPNOC requested Enforcement Discretion from the Technical Specification requirements to allow operation for an additional eight days beyond the allowed outage time. The request was granted by the NRC.
The HHSI pump and the associated components were declared operable at 1119 on December 7, 2006. This event did not have an adverse effect on the health and safety of the public.
There are no commitments contained in this Licensee Event Report. Corrective actions will be processed in accordance with the STP Corrective Action Program.
If there are any questions on this submittal, please contact either P. L. Walker at (361) 972-8392 or me at (361) 972-8902.
Ken L. Coates Plant Manager PLW
Attachment:
LER 2-06-001, Safety Injection Train Inoperable Longer Than Allowed Under Technical Specifications LER 2-06-001.doc STI: 32105478
NOC-AE-07002105 Page 2 of 2 cc:
(paper copy)
(electronic copy)
Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 Richard A. Ratliff Bureau of Radiation Control Texas Department of Health 1100 West 4 9 th Street Austin, TX 78756-3189 Senior Resident Inspector U. S. Nuclear Regulatory Commission P. 0. Box 289, Mail Code: MN1 16 Wadsworth, TX 77483 C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704 A. H. Gutterman, Esquire Morgan, Lewis & Bockius LLP Mohan Thadani U. S. Nuclear Regulatory Commission Steve Winn Christine Jacobs Eddy Daniels Marty Ryan NRG South Texas LP J. J. Nesrsta R. K. Temple Kevin Polio City Public Service C. Kirksey City of Austin Jon C. Wood Cox Smith Matthews LER 2-06-001.doc
Abstract
On November 27, 2006, Unit 2 High Head Safety Injection (HHSI) pump 2A of the Emergency Core Cooling System (ECCS) was declared inoperable at 0100 due to maintenance requirements; this also made the associated low head safety injection and containment spray pumps inoperable. During disassembly, internal damage to the pump occurred, requiring repairs before the HHSI pump could be returned to operability. The allowed outage time expired at 0100 on December 4, 2006. Because the repairs were expected to exceed that time, Enforcement Discretion was approved by the NRC on December 3, 2006, allowing operation for an additional eight days.
Technical Specifications 3.5.2 and 3.6.2.1 require that if one train of ECCS and containment spray is inoperable, it is to be restored to operability within seven days or the unit is to be in at least hot standby within six hours. The HHSI pump and the associated components were declared operable at 1119 on December 7, 2006. Because these components were inoperable longer than allowed under the Technical Specifications without entering the appropriate action statements, this event is reportable pursuant to 10 CFR 50.73(a)(2)(i)(B).
The root cause is that the unexpected condition was not sufficiently assessed and the potential hazards to the affected components were not identified prior to proceeding to use force in removing the pump half-coupling. For corrective action, affected personnel will be retrained on the Conduct of Maintenance and expectations on tool use.
The Rotating Equipment Certifications of the craftsmen involved have been deactivated, pending remedial training and recertification.
In addition, a contributing factor of a pre-existing condition involving assembly of the pump rotating element was identified. This aspect is currently under review.
Only Train A of Unit 2 was affected. This event resulted in no personnel injuries, no offsite radiological releases, and no damage to other safety-related equipment.
(if more space is required, use additional copies of SUMMARY OF THE EVENT At 0100 on November 27, 2006, Unit 2 High Head Safety Injection (HHSI) pump 2A of the Emergency Core Cooling System (ECCS) was declared inoperable to perform planned maintenance activities to replace the mechanical seal. This also made the associated Low Head Safety Injection (LHSI) and Containment Spray (CS) systems inoperable.
Access to the mechanical seal required removal of a pump half-coupling. However, the half-coupling was found to be stuck. To free the stuck half-coupling, use of hydraulic force was determined to be necessary.
The force exerted in freeing the half-coupling apparently damaged the pump internals.
The mechanical seal package was replaced and, during reassembly, a spacer connecting the half-coupling could not be reinstalled due to a lack of clearance.
The pump casing was filled with water to check the pump shaft for freedom of rotation. However, the pump shaft would not rotate, with the following as probable causes:
- Internal obstruction resulting from application of excessive force to remove the half-coupling.
- Internal obstructions resulting from repeated vertical movement of the pump shaft without lubrication to the upper impeller bearings during reassembly, causing galling of the stainless steel bearings.
Consequently, the decision was made to overhaul the pump, including replacement of the rotating element. Actions to restore the pump to operability were expected to require an additional six days beyond the seven-day allowed outage time that expired at 0100 on December 4, 2006. Because this was a first-time evolution for the South Texas Project, Enforcement Discretion was requested from the NRC and was verbally approved by the NRC on December 3, 2006, allowing an additional eight days of operation to complete restoration of the pump.
Operability of the other two Unit 2 HHSI pumps, Train B and Train C, was confirmed by satisfactory test results on December 2, 2006.
The rotating element was shipped to the vendor for disassembly, failure analysis, and
(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) (17)
HALF.-COUPLING (OS)
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