05000389/LER-2002-001
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3892002001R00 - NRC Website | |
FACILITY NAME (1) NUMBER (2) LER NUMBER (6) PAGE (3) St. Lucie Unit 2 05000389
Description of the Event
On May 13, A 2002, A St. Lucie Unit 2 was in Mode 1 operation at 100 percent reactor power. A St. Lucie was preparing to repair identified seal discrepancies on doors [ETIS:VI:DR:SEAL] A that provide access through the control room A (CR) A ventilation boundary. A At 0800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br />, maintenance requested permission to repair CR door RA-114.
CR door RA-114 is the external door of a two-door vestibule. A RA-114 was fully opened to determine if the inner door of the two-door vestibule, RA-108, was capable of maintaining the CR pressure boundary for an extended time period. A With RA-114 fully open, the CR pressure was not affected and no CR low pressure alarms were received.
Maintenance was then given permission to work on CR door RA-114. No Technical Specification (TS) Limiting Condition of Operation (LCO) Action was entered because it was determined that door RA-114 did not affect the CR pressure boundary. Repair activities on door RA-114 were suspended on May 14, 2002 when Engineering was contacted to resolve door seal design issues.
On May 16, 2002, at 0824 hours0.00954 days <br />0.229 hours <br />0.00136 weeks <br />3.13532e-4 months <br />, St. Lucie Unit 2 voluntarily entered TS 3.7.7 Action b for an inoperable control room emergency air cleanup system (CREACS) during restoration of an unrelated ventilation system temporary system alteration (TSA).
The TSA restoration scope was completed when blank plates were removed and registers re-installed in ductwork located in the cable spreading room (CSR). At approximately 1115 hours0.0129 days <br />0.31 hours <br />0.00184 weeks <br />4.242575e-4 months <br />, a CREACS TS surveillance was performed to ensure that the TSA restoration had no adverse effect on the CR envelope. However, the test results were unsatisfactory, and TS 3.7.7 Action b continued during the re-installation of the TSA. At 1450 hours0.0168 days <br />0.403 hours <br />0.0024 weeks <br />5.51725e-4 months <br />, after the TSA was re-installed, the effect of the degraded RA- 114 door seals on the surveillance was questioned. The TS surveillance was performed again with unsatisfactory results. Troubleshooting efforts were focused on the CR boundary doors, and results indicated that the CR envelope could be established if door seals were installed on RA-108, the inner door vestibule counterpart to RA-114.
All St. Lucie Unit 2 TS 3.7.7 action statements were exited at 2255 hours0.0261 days <br />0.626 hours <br />0.00373 weeks <br />8.580275e-4 months <br /> when the TS surveillance was performed satisfactorily subsequent to RA-108 door seal installation.
Cause of the Event
This event was caused by personnel error because the degraded seal condition of doors RA-108 and RA-114 was not adequately evaluated during the door seal maintenance.
Although door RA-108, the inner door of the vestibule, was previously identified as having no door seals, this condition was not considered an issue because the CR pressure remained greater than 1/8 inch water gage (wg) when the outer vestibule door (RA-114) was opened. However, St. Lucie personnel failed to realize that this pre-maintenance check was inappropriate with CREACS in its normal operating lineup because the outside air make up flow was much greater (-1000 cfm) than the flow allowed during accident conditions (450 cfm). Opening door RA-114 would have little effect on CR pressure with outside air make up flow approaching 1000 CFM. The pre- maintenance check gave CR personnel false assurance that the seal condition of doors RA-114 and RA-108 had no effect on the CR pressure boundary because the CR pressure remained at greater than 1/8 inch wg above its surroundings.
Analysis of the Event
This event is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as "any operation or condition prohibited by the plant's Technical Specifications," and NUREG-1022, Revision 2 guidance. There is firm evidence that both CREACS trains were unable to pass a TS surveillance from May 13, 2002, when work commenced on door RA-114, until May 16, 2002 when seals were installed on door RA-108 and a successful TS surveillance performed.
Analysis of Safety Significance CREACS assures CR habitability by controlling the environment in the CR envelope during normal plant operation, anticipated operational occurrences, or abnormal occurrences. CREACS maintains the CR envelope at an average positive pressure of 1/8 inch wg above that of the surroundings during normal plant operation and following a loss of coolant accident (LOCA). The system design assures that no single active failure coincident with a loss of off-site power could result in loss of functional performance. The CREACS design bases is to prevent post-accident operator dose from exceeding the limits of General Design Criterion (GDC) 19. The subject CR door seals are necessary to maintain the CR pressure boundary during normal and post-accident conditions.
Although the CR pressure boundary TS surveillance could not be successfully completed, FPL concludes that CREACS was able to maintain sufficient positive CR pressure with respect to its surroundings during the time period between May 13, 2002 and May 16, 2002. The safety function, though degraded, was satisfied based on a review of the available surveillance test data and the CR envelope remained operable with respect to its design bases function of maintaining operator dose within GDC 19 criteria. Therefore, this event had no adverse effect on the health and safety of the public.
Corrective Actions
1. The door seals on RA-108 were installed on May 16, 2002.
2. The CR envelope was restored and both trains of CREACS satisfactorily passed the TS surveillance on May 16, 2002.
3. Door repairs are being performed under plant work order (PWO) 31023087.
4. St. Lucie is considering this event for inclusion in the continuing training program.
Additional Information
Failed Components Identified None Similar Events Recirculation Procedures Inadequate.