ENS 48095
ENS Event | |
|---|---|
20:20 Jul 11, 2012 | |
| Title | Cable Associated with 4Kv Shutdown Board Routed Incorrectly |
| Event Description | On July 11, 2012, during the [National Fire Protection Association] NFPA 805 transition review process for the Browns Ferry Nuclear Plant (BFN), it was discovered that a cable associated with 4kV Shutdown Board B cross-tie breaker 1828 differential lockout contacts was not routed in accordance with the Appendix R Separation Analysis. Specifically, the cable was determined to be routed in Fire Zone 03-02 and is considered to be an unanalyzed condition.
In the event of an Appendix R fire in Fire Zone 03-02, fire damage to cables associated with 4kV Shutdown Board B cross-tie breaker 1828 and the 4kV Shutdown Board 3EB cross-tie breaker 1848 could occur. A fire induced hot short could cause spurious closure of breaker 1828. Fire damage to cable associated with 4kV Shutdown Board B cross-tie breaker 1828 differential lockout contacts could also result in the loss of the breaker trip function. This condition may result in the following two failures: 1) If breaker 1828 spuriously closed, it could close onto a fault, since the cross-tie power cables from breaker 1828 on 4kV Shutdown Board B to Breaker 1848 on 4kV Shutdown Board 3EB are routed through Fire Zone 03-02 and would be subject to a fire induced fault, if energized. This could result in the trip of Diesel Generator B output breaker 1822 and deenergization of the 4kV Shutdown Board B. 2) Breaker 1848 on 4kV Shutdown Board 3EB is also vulnerable to spurious closure in the event of an Appendix R fire in Fire Zone 03-02, as the control cable for this breaker is routed through Fire Zone 03-02. In accordance with the applicable BFN Safe Shutdown Instruction, breaker 1848 is isolated and tripped locally prior to connecting Diesel Generator 3B to 4kV Shutdown Board 3EB. If offsite power was lost and 4kV Shutdown Board B and 4kV Shutdown Board 3EB were powered from Diesel Generators B and 3B respectively, and fire damage occurred to the breaker 1848 control cable and the cable for the breaker 1828 differential lockout contacts (which are both routed in Fire Zone 03-02) prior to the completion of Safe Shutdown Instruction steps to isolate and trip breaker 1848, then the potential to parallel Diesel Generators B and 3B out of phase would exist. Paralleling the Diesel Generators B and 3B out of phase with each other or offsite power poses the potential to damage either Diesel Generator. Therefore, this condition could result in a loss of power to credited safe shutdown equipment that would challenge the ability to provide adequate core cooling during performance of BFN Safe Shutdown Instructions. This condition is being reported pursuant to 10 CFR 50.72(b)(3)(ii)(B). This is also reportable as a 60-day written report in accordance with 10 CFR 50.73(a)(2)(ii)(B). The NRC Resident Inspector has been notified of this event. |
| Where | |
|---|---|
Browns Ferry  Alabama (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+-1.03 h-0.0429 days <br />-0.00613 weeks <br />-0.00141 months <br />) | |
| Opened: | Dvid Renn 19:18 Jul 11, 2012 |
| NRC Officer: | John Knoke |
| Last Updated: | Jul 11, 2012 |
| 48095 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 542662019-09-11T00:34:00011 September 2019 00:34:00
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