05000499/LER-2005-003, Regarding Inoperable Cold Overpressure Mitigation System
| ML051330251 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 05/10/2005 |
| From: | Parkey G South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NOC-AE-05001878 LER 05-003-00 | |
| Download: ML051330251 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability |
| 4992005003R00 - NRC Website | |
text
Nuclear Operating Company South rbas Prca Ekodrc Gencrlln&Stabo 0.n BPO 282 Htdsrh Trs 77483 May 10, 2005 NOC-AE-05001878 1 OCFR50.73 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852 South Texas Project Unit 2 Docket No. STN 50-499 Licensee Event Report 2-05-003 Inoperable Cold Overpressure Mitigation System Pursuant to 10CFR50.73, the South Texas Project submits the attached Unit 2 Licensee Event Report 2-05-003 regarding inoperability of the Cold Overpressure Mitigation System (COMS) during solid plant operations. The requirements of Technical Specification 3.4.9.3 were not met, in that a Reactor Coolant System vent of at least two square inches was not provided within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> following removal of power to the COMS actuation circuitry. 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) 972-7849.
Gary Parkey Vice President, Generation and Plant General Manager PLW Attachment: LER 2-05-003, Inoperable Cold Overpressure Mitigation System LER 2-05-003.doc STI: 31878114
NOC-AE-005001 878 Page 2 of 2 cc:
(paper copy)
(electronic copy)
Bruce S. Mallett 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 9th Street Austin, TX 78756-3189 Jeffrey Cruz U. S. Nuclear Regulatory Commission P. O. Box 289, Mail Code: MN116 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 David H. Jaffe U. S. Nuclear Regulatory Commission Jack A. Fusco Michael A. Reed Texas Genco, LP C. A. Johnson AEP Texas Central Company C. Kirksey City of Austin Jon C. Wood Cox Smith Matthews J. J. Nesrsta R. K. Temple E. Alarcon City Public Service LER 2-05-003.doc
Abstract
On Monday, March 7, 2005, preparations were being made to implement a modification to Unit 1 during its refueling outage.
Isolation of two actuation cabinets of the Solid State Protection System was required to complete the modification. Prior to isolation, it was determined that this would make the Cold Overpressurization Mitigation System (COMS) inoperable when Technical Specification 3.4.9.3 required that it be operable.
This was resolved by rescheduling the system isolation. Subsequent review found that while installing a similar modification on Unit 2 during the preceding Unit 2 refueling outage, two actuation cabinets were de-energized, making COMS inoperable without compensatory action as required by Technical Specifications. This was found to be reportable on March 11, 2005.
The root cause of this event was that the operational impact on COMS of de-energizing the 'A' and 'B' SSPS actuation cabinets for maintenance was not recognized. Detailed information regarding which equipment/components would be affected was not readily available in a usable format for review.
For corrective action, a load list will be developed for each of the Solid State Protection System actuation cabinets identifying the affected components and their state when the cabinet is de-energized. This information will be included in the applicable operating procedure. As a compensatory action until the corrective action is completed, the system engineer will be contacted to confirm the extent of impact on plant equipment/components prior to implementation of scheduled work activities that include de-energizing SSPS equipment.
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 NRC Forn 366A) (17)
I.
DESCRIPTION OF EVENT
A.
REPORTABLE EVENT CLASSIFICATION
This event is reportable pursuant to 10CFR50.73(a)(2)(i)(B). The South Texas Project has determined that the Unit 2 Cold Overpressurization Mitigation System (COMS) was inoperable without compensatory actions required by Technical Specifications.
The requirements of Technical Specification 3.4.9.3 were not met in that a Reactor Coolant System vent of at least two square inches was not provided within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> following removal of power to COMS actuation circuitry.
This event is also reportable pursuant to IOCFR50.73(a)(2)(vii).
This condition made two independent trains inoperable in a single system designed to mitigate the consequences of an accident. Reportability was determined on March 11, 2005.
B.
PLANT OPERATING CONDITIONS PRIOR TO EVENT
South Texas Project Unit 2 was in Mode 5.
C.
STATUS OF STRUCTURES, SYSTEMS, AND COMPONENTS THAT WERE INOPERABLE AT THE START OF THE EVENT AND THAT CONTRIBUTED TO THE EVENT There were no additional inoperable structures, systems, or components that contributed to the event.
D.
NARRATIVE SUMMARY OF THE EVENT
A modification affecting the Main Steam Isolation valves was implemented in Unit 1 during refueling outage lRE12. Implementation of the modification required that two of the Solid State Protection System actuation trains be de-energized. On March 7, 2005, during preparation for the outage, review of the schedule led to a question about operability of the COMS during solid plant operation. The response at the time was that operability would not be affected while the unit was under solid plant conditions. However, further discussion came to the conclusion that de-energizing both of the Solid State Protection System trains would make COMS inoperable.
Documentation of the effect on COMS from loss of power to the actuation cabinets is a seldom-used vendor control-wiring diagram.
This had not been documented in any procedure or guideline used during the process of implementing the modification. The Unit 1 outage schedule for 1 RE1 2 was rearranged so that COMS operability was no longer a Technical Specification issue. Consequently, there was no violation of Technical Specification requirements by Unit 1.
This led to review of the experience for its applicability to Unit 2.
A modification affecting the Feedwater Isolation Valves was implemented in Unit 2 during refueling outage 2RE10 in March 2004. While Unit 2 was in Modes 5 and 6, power was removed from the Solid State Protection System actuation trains for the modification to be performed. It was not realized that de-energizing the two SSPS actuation cabinets would make COMS inoperable. Power was removed at 1922 on March 31, 2004 and not restored until 1115 on April 2, 2004. Technical Specification 3.4.9.3 requires that either two pressurizer power-operated relief valves be operable, or that the Reactor Coolant System be depressurized using a vent of at least two square inches. With both relief valves inoperable, venting through the 2.0 square inch vent is required within the subsequent 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
Power was not restored for approximately 39 hours4.513889e-4 days <br />0.0108 hours <br />6.448413e-5 weeks <br />1.48395e-5 months <br /> 53 minutes, exceeding the time allowed by the Technical Specifications.
(if more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17)
IV.
CORRECTIVE ACTIONS
For corrective action, a load list will be developed for each of the Solid State Protection System actuation cabinets identifying the affected components and their state when the cabinet is de-energized.
This information will be included in the applicable operating procedure. As a compensatory action until the corrective action is completed, the system engineer will be contacted to confirm the extent of impact on plant equipment/components prior to implementation of scheduled work activities that include de-energizing SSPS equipment.
V.
PREVIOUS SIMILAR EVENTS
None.
VI.
ADDITIONAL INFORMATION
None.