U.S. Nuclear Regulatory Commission
Operations Center
Event Reports For
06/04/2003 - 06/05/2003
** EVENT NUMBERS **
39903
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|Power Reactor |Event Number: 39903 |
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| FACILITY: OCONEE REGION: 2 |NOTIFICATION DATE: 06/04/2003|
| UNIT: [1] [2] [3] STATE: SC |NOTIFICATION TIME: 19:03[EDT]|
| RXTYPE: [1] B&W-L-LP,[2] B&W-L-LP,[3] B&W-L-L|EVENT DATE: 06/04/2003|
+------------------------------------------------+EVENT TIME: 11:15[EDT]|
| NRC NOTIFIED BY: RANDY TODD |LAST UPDATE DATE: 06/04/2003|
| HQ OPS OFFICER: JOHN MacKINNON +-----------------------------+
+------------------------------------------------+PERSON ORGANIZATION |
|EMERGENCY CLASS: NON EMERGENCY |KERRY LANDIS R2 |
|10 CFR SECTION: | |
|AUNA 50.72(b)(3)(ii)(B) UNANALYZED CONDITION | |
| | |
| | |
| | |
+-----+----------+-------+--------+-----------------+--------+-----------------+
|UNIT |SCRAM CODE|RX CRIT|INIT PWR| INIT RX MODE |CURR PWR| CURR RX MODE |
+-----+----------+-------+--------+-----------------+--------+-----------------+
|1 N Y 100 Power Operation |100 Power Operation |
|2 N Y 100 Power Operation |100 Power Operation |
|3 N N 0 Cold Shutdown |0 Cold Shutdown |
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EVENT TEXT
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| APPENDIX R ISSUE |
| |
| During an Appendix R design basis review, an Engineer noted that cables |
| associated with normal operation of components used for one train (Primary |
| Isolation valves) of Appendix R mitigation were routed through an adjacent |
| fire zone associated with the other train of Appendix R mitigation. During |
| an Appendix R event, control of the affected components is transferred to |
| the Standby Shutdown Facility, which electrically isolates the subject |
| cables. |
| |
| However, the area containing the subject cables does not have fire detection |
| equipment. The Engineer noted that if a fire occurred and damaged the |
| cables, it would be theoretically possible for a "smart short" to result in |
| damage to equipment before action could be taken to transfer control to the |
| Standby Shutdown Facility. |
| |
| |
| Initial Safety Significance: |
| |
| This condition is similar to an example given in NUREG 1022, Section 3.2.4 |
| (fire barrier missing such that the required degree of separation for |
| redundant safe shutdown trains is lacking). |
| |
| In order to result in a loss of safety function, the postulated fire would |
| have to damage the cable, result in a smart spurious actuation of a |
| component, damage that component such that it became inoperable (such as by |
| burning out the motor of a valve), then also spread within the fire zone to |
| damage the redundant component (for example by burning the power cable or |
| motor control center). |
| |
| The Oconee license basis is no spurious circuit operations for 10 minutes. |
| Cable testing sponsored by the NRC, NEI, and EPRI for fire exposure has |
| demonstrated that armored type cable construction used in this application |
| is more rugged than other designs and that internal cable failure times |
| usually extend beyond 30 minutes. |
| |
| The area containing the cables is a high traffic area for both personnel and |
| material - including low quantities of transient combustibles, but has no |
| appreciable fixed fire loads. Thus the probability of a fire of sufficient |
| energy to damage the cable is low. Pending a PRA analysis, it appears |
| reasonable to credit prompt discovery of a fire and initiation of action to |
| suppress the fire and/or transfer of control to the Standby Shutdown |
| Facility prior to cable damage. Therefore the overall risk impact of this |
| event is currently considered low. |
| |
| |
| Corrective Action: |
| |
| The SSF has been declared inoperable pending establishment of a fire watch. |
| |
| The NRC Resident Inspector will be informed of this event by the licensee. |
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