05000260/LER-2010-002
| Browns Ferry Nuclear Plant Unit 2 | |
| Event date: | 04-26-2010 |
|---|---|
| Report date: | 06-25-2010 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| Initial Reporting | |
| 2602010002R00 - NRC Website | |
I. PLANT CONDITION(S)
At the time of discovery, Browns Ferry Nuclear Plant (BFN) Units 1, 2, and 3 were at 100 percent power.
II. DESCRIPTION OF EVENT
A. Event:
On April 9, 2010, at approximately 0218 hours0.00252 days <br />0.0606 hours <br />3.604497e-4 weeks <br />8.2949e-5 months <br /> Central Daylight Time (CDT), Maintenance personnel commenced the performance of Surveillance Procedure 2-SR-3.3.6.1.6(4), Reactor Core Isolation Cooling (RCIC) [BN] Time Delay Relay Calibration. This procedure is performed to determine the operability of the RCIC Steam Line Flow - High Isolation Function for both the A and B Channels. At approximately 0500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br /> CDT, Maintenance personnel completed performance of 2-SR-3.3.6.1.6(4).
On April 26, 2010, at approximately 1115 hours0.0129 days <br />0.31 hours <br />0.00184 weeks <br />4.242575e-4 months <br /> CDT, a Quality Assurance Inspector notified Operations personnel that there were contact boots on contacts 1, 2, 3 and 4 of relay 2-RLY-071-13A-K32, RCIC High Steam Flow Relay. Operations immediately declared the associated B Channel of the RCIC Steam Line Flow - High Isolation Function inoperable, and entered Technical Specification (TS) 3.3.6.1, Action A, which requires that with one or more required channels inoperable, within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, place the channel in trip.
On April 26, 2010, at approximately 1140 hours0.0132 days <br />0.317 hours <br />0.00188 weeks <br />4.3377e-4 months <br /> CDT, after verifying there was no testing or maintenance activities in progress that required the contact boots to be in place, Operations personnel removed the contact boots from contacts of relay 2-RLY-071-13A-K32 and declared the B Channel of the RCIC Steam Line Flow - High Isolation Function operable, exiting TS 3.3.6.1 Action A. Operations also verified that the A Channel remained operable during the time the B Channel was inoperable which would have isolated RCIC on a valid Steam Line Flow - High signal (i.e., verified that isolation capability was maintained).
The Tennessee Valley Authority (WA) determined that the B Channel of RCIC High Steam Flow Isolation logic was inoperable April 9, 2010 at approximately 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br /> CDT until April 26, 2010 at 1140 hours0.0132 days <br />0.317 hours <br />0.00188 weeks <br />4.3377e-4 months <br /> CDT which is longer than allowed the 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> allowed by TS. Thus, WA is submitting this report in accordance with 10 CFR 50.73(a)(2)(i)(B), any operation or condition prohibited by the plant's Technical Specifications.
B. Inoperable Structures, Components, or Systems that Contributed to the Event:
None C. Dates and Approximate Times of Major Occurrences:
April 9, 2010, between 0218 hours0.00252 days <br />0.0606 hours <br />3.604497e-4 weeks <br />8.2949e-5 months <br /> and 0500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br /> CDT April 26, 2010, at 1115 hours0.0129 days <br />0.31 hours <br />0.00184 weeks <br />4.242575e-4 months <br /> CDT Maintenance personnel performed 2-SR-3.3.6.1.6(4).
Operation informed that there are contact boots on relay 2-RLY-071-13A-K32.
April 26, 2010, at 1115 hours0.0129 days <br />0.31 hours <br />0.00184 weeks <br />4.242575e-4 months <br /> CDT April 26, 2010, at 1140 hours0.0132 days <br />0.317 hours <br />0.00188 weeks <br />4.3377e-4 months <br /> CDT
D. Other Systems or Secondary Functions Affected
None
E. Method of Discovery
The contact boots were found by visual observation.
F. Operator Actions
None
G. Safety System Responses
None
III. CAUSE OF THE EVENT
Operations declares the B Channel of the RCIC Steam Line Flow - High Isolation Function inoperable and enters TS 3.3.6.1, Action A.
Operations removes contact boots from the relay, declares the B Channel of the RCIC Steam Line Flow - High Isolation Function operable, and exits TS 3.3.6.1 Action A.
A. Immediate Cause
The immediate cause for the event was a failure to remove the contact boots following the completion of the testing activities on relay 2-RLY-071-13A-K32.
B. Root Cause
The root cause of this event was a failure of the individuals involved to use human performance tools and verify the contact boots were removed as required by Surveillance Procedure 2-SR-3.3.6.1.6(4).
C. Contributing Factors
There was no requirement to independently verify the contact boots were removed. The procedure contained steps for concurrent first and second party sign off for removal of the relay contact boots.
IV. ANALYSIS OF THE EVENT
The contact boots installed on relay 2-RLY-071-13A-K32 during the performance of 2-SR-3.3.6.1.6(4) rendered the B Channel of RCIC Steam Line Flow -High Isolation Function inoperable. During the time the B Channel of RCIC Steam Line Flow - High Isolation Function was inoperable, the A Channel remained operable. Thus, the Unit 2 RCIC system would have isolated on a RCIC Steam Line Flow - High signal, if needed.
V. ASSESSMENT OF SAFETY CONSEQUENCES
The safety consequences of this event were not significant. The RCIC Steam Line Flow - High Function is provided to detect a break of the RCIC steam lines and initiate closure of the steam line isolation valves of the RCIC system. During this event, isolation capability of the RCIC Steam Line Flow - High Isolation Function was maintained. Although one channel of the RCIC Steam Line Flow - High Isolation Function was inoperable, the redundant channel remained operable and would have actuated to isolate the RCIC steam lines on a valid RCIC Steam Line Flow - High signal, if required. Therefore, WA concludes that there was no significant reduction in the protection of the public by this event.
VI. CORRECTIVE ACTIONS - The corrective actions are being managed with TVA's Corrective Action Program
A. Immediate Corrective Actions
The immediate corrective actions included determining if any on-going testing activities which could require the contact boots to be in place. Once it was determined that there were no on- going testing activities, the contact boots were removed. A walk down of the Auxiliary Instrument Rooms for Units 1, 2, and 3 was conducted. No other contact boots were found.
B. Corrective Actions to Prevent Recurrence
The individuals involved will receive appropriate personnel actions.
WA will review and revise applicable procedures to incorporate independent verification requirements for steps associated with restoring the correct configuration when removing contact boots.
VII. ADDITIONAL INFORMATION
A. Failed Components
None B. Previous LERs On Similar Events No previous LERs were identified for a similar event. WA has found two similar occurrences, one in May of 2006 and one in June of 2007. Contact boots were left in place following maintenance activities. In both of these occurrences work was being performed by multiple groups, and the actions to remove the contact boots had been completed prior to declaring the associated systems operable. The steps to remove the contact boots had been marked "not applicable." Corrective actions for both occurrences included a briefing on the issue with Maintenance personnel. Following the June 2007 occurrence, Mechanical Maintenance procedures were revised to include first and second party signatures for installation and removal of contact boots. The previous corrective actions appear to be ineffective.
Incorporating independent verification steps into applicable procedures should be effective in preventing recurrence of this type event.
C. Additional Information
Corrective action document for this report is Problem Evaluation Report 226666.
D. Safety System Functional Failure Consideration:
This event is not classified as a safety system functional failure according to NEI 99-02.
E. Scram With Complications Consideration:
This event was not classified as a complicated scram according to NEI 99-02.
VIII. COMMITMENTS
None