05000338/LER-2009-002
| Document Numbersequential Revmonth Day Year Year Month Day Year 05000Number No. | |
| Event date: | 10-23-2009 |
|---|---|
| Report date: | 12-15-2009 |
| 3382009002R00 - NRC Website | |
1.0 DESCRIPTION OF THE EVENT At 1626 hours0.0188 days <br />0.452 hours <br />0.00269 weeks <br />6.18693e-4 months <br /> on 10/23/09, a through-wall leak on the Unit 1 normal letdown line upstream of containment isolation valve 1-CH-TV-1204B (EllS System - CB, Component - ISV) was confirmed by Engineering. The leak located on the inlet side of the valve was almost undetectable and could only be seen by fogging of inspection mirrors. The valve was declared inoperable due to loss of containment isolation integrity and Technical Specification LCO 3.6.1A was entered.
At 1633 hours0.0189 days <br />0.454 hours <br />0.0027 weeks <br />6.213565e-4 months <br />, excess letdown was placed in-service to allow isolation of the normal letdown line and facilitate repairs of the weld leak. Almost immediately, indications of reactor coolant system (El IS System - AB) leakage into the component cooling (CC) system (EllS System - CC) were identified. The excess letdown system (EllS Sys- CB) was isolated. It was determined that approximately 260 gallons of reactor coolant had leaked to the CC system. At 1639 hours0.019 days <br />0.455 hours <br />0.00271 weeks <br />6.236395e-4 months <br />, it was determined that Emergency Action Level (EAL) SU6.1, RCS Leakage, was exceeded for four minutes from 1634 hours0.0189 days <br />0.454 hours <br />0.0027 weeks <br />6.21737e-4 months <br /> to 1638 hours0.019 days <br />0.455 hours <br />0.00271 weeks <br />6.23259e-4 months <br />.
At 1718 hours0.0199 days <br />0.477 hours <br />0.00284 weeks <br />6.53699e-4 months <br /> a unit shutdown commenced to repair the through wall leak on 1-CH-TV 1204B. At 1353 hours0.0157 days <br />0.376 hours <br />0.00224 weeks <br />5.148165e-4 months <br /> on October 24, 2009, Unit 1 entered Mode 5 cold shutdown. The normal letdown line leak was determined to be in the weld between the valve body and the special end connection. Subsequently, the normal letdown line leak was repaired and the system returned to service. The leak from RCS to CC was determined to be a failed tube in the excess letdown heat exchanger (EllS Component - HX). The tube has been plugged and the excess letdown heat exchanger was returned to standby mode. The Unit 2 excess letdown heat exchanger remains isolated. Unit 1 entered Mode 1 at 0643 hours0.00744 days <br />0.179 hours <br />0.00106 weeks <br />2.446615e-4 months <br /> on October 29, 2009. Unit 1 achieved 100 percent power at 0340 hours0.00394 days <br />0.0944 hours <br />5.621693e-4 weeks <br />1.2937e-4 months <br /> on October 30, 2009.
At 1734 hours0.0201 days <br />0.482 hours <br />0.00287 weeks <br />6.59787e-4 months <br /> on October 23, 2009, a one hour non-emergency report for a classification without declaration was made to the NRC Operations Center pursuant to 10 CFR 50.72(a)(1). A declaration of a Notification of Unusual Event (NOUE) was not made since the event had been terminated prior to the notification. A four hour non-emergency report was also made for a TS required shutdown pursuant to 10 CFR 50.72(b)(2)(i). The Virginia Department of Emergency Management (VDEM) was notified at 1918 hours0.0222 days <br />0.533 hours <br />0.00317 weeks <br />7.29799e-4 months <br /> as a result of exceeding EAL SU6.1.
2.0 SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS The through wall leak on 1-CH-TV-1204B was extremely small and had no impact on letdown flow required for RCS volume control and purification or for RC pump seal water injection. The weld defect was removed and a weld repair was satisfactorily completed.
This event posed no significant safety implications since there was no release of radioactive material. Therefore, the health and safety of the public were not affected by this event.
� This event is reportable pursuant to 10 CFR 50.73 (a)(2)(i)(A) for completion of a unit shutdown required by the plants Technical Specifications.
3.0 CAUSE The cause of the through wall leak on the containment side of containment isolation valve 1-CH-TV-1204B was determined to be from a defect in the weld between the valve body and the special end connection. The apparent cause of the weld defect was discontinuities from initial fabrication by the vendor which were not discovered by original construction non-destructive testing (NDE).
4.0 IMMEDIATE CORRECTIVE ACTION(S) Unit 1 was ramped to Mode 5 cold shutdown to facilitate repairs to through-wall leak on the containment side of containment isolation valve 1-CH-TV-1204B. Verbal notifications were made to the NRC Operations Center and the VDEM. The excess letdown heat exchanger was eddy current tested and one tube was plugged. The excess letdown heat exchanger was returned to standby mode.
5.0 ADDITIONAL CORRECTIVE ACTIONS The repairs for the through-wall leak on the Unit 1 normal letdown line upstream of containment isolation valve 1-CH-TV-1204B have been satisfactorily completed. This event was determined not to have been caused by any programmatic issues. This valve will continue to be examined by the Appendix J and ISI System Pressure Test Programs.
Non-destructive testing will be performed on two valves of similar construction. These tests will serve as a sample of a population of valves of the same construction. Any unsatisfactory results will require an evaluation as to whether further NDE will be necessary.
6.0 ACTIONS TO PREVENT RECURRENCE Actions stated are sufficient to prevent recurrence.
7.0 SIMILAR EVENTS LER N2-01-001-00, submitted on 2/16/01, identified a Unit 2 shutdown required by TS due to identified RCS leakage exceeding limits.
8.0 ADDITIONAL INFORMATION Unit 2 was operating at 100 percent power, Mode 1, and was not affected by the event.
9 8.0 ADDITIONAL INFORMATION (continued) Component information:
Mark Number � 1-CH-TV-1204B Manufacturer� Masoneilan Model Number � 20721 Description � 2 inch globe valve, 316 SST, with 2 inch socket-weld end connections �