05000244/LER-2014-002
| R.E. Ginna Nuclear Power Plant | |
| Event date: | 03-13-2014 |
|---|---|
| Report date: | 05-08-2014 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition |
| 2442014002R00 - NRC Website | |
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1. DESCRIPTION OF EVENT
A. PRE-EVENT CONDITIONS At the time of discovery, the plant was in Mode 1 at approximately 100% power.
B. EVENT DESCRIPTION
On March 13, 2014, during a review of industry Operating Experience (OE), Ginna identified that there were unprotected DC control circuits for Non Safety Related DC motors which are routed from the turbine building to other separate fire areas. Fuses used to protect the motor power conductors appear to be inadequate to protect the control conductors. It is postulated that under fire safe shutdown conditions, a fire in one area can cause short circuits potentially resulting in secondary fires or cable failures in other fire areas where the cables are routed. The secondary fires or cable failures are outside the assumptions of the 10 CFR 50 Appendix R Safe Shutdown Analysis.
C. DATES AND TIMES OF OCCURENCES
1967 Original Construction 03/13/2014 Review of Industry Operating Experience identifying postulated Hot Short Condition 04/11/2014 Fuses installed in Circulating Water Pump Discharge MOV control circuits
D. METHOD OF DISCOVERY
Review of systems and drawings based upon industry operating experience.
E. MAJOR OPERATOR ACTION
Established compensatory actions consisting of hourly fire tours of the affected areas.
F. SAFETY SYSTEM RESPONSE
None required.
2. CAUSE OF EVENT
The cause of this condition is that the Original Design did not meet current fire protection standards.
This is a latent design issue that has been present since plant construction (in the late 1960s). A postulated fire-induced circuit failure that causes the condition requires two opposite polarity conductors to short to each other.
Contributing to this, the design analysis for this non-safety related electrical panel only evaluated protection for the power cables connected to the fuses, and not the control circuits for the motors.
3. ANALYSIS OF EVENT
This event is reportable under 10CFR50.73(a)(2)(ii)(B) for the concern is it could be possible for a fire in one fire area to damage this circuit and cause a short circuit that would overheat the cables before the fuses would provide protection. This short circuit could possibly result in secondary fires or cable damage in other fire areas where the cables are routed. The Ginna Fire Protection Plan does not analyze for simultaneous fires in two or more fire protection areas. If the situation were to occur, the plant would be in an unanalyzed condition, with the potential to impact equipment credited for safe shutdown.
This condition was entered into the corrective action program under CR-2014-001346.
All DC motor circuits were reviewed for the potential vulnerability. DC Motor control circuits were reviewed to determine if the conductors are adequately protected and validate they do not have to potential to propagate a fire.
4. CORRECTIVE ACTIONS
Fuses have been installed to protect the control circuits for the Circulating Water Pump Discharge MOVs.
The design analysis will be revised to reflect the new configuration.
5. ADDITIONAL INFORMATION
A. FAILED COMPONETS
None.
B. PREVIOUS LERs ON SIMILAR EVENTS
LER-2013-003 Unanalyzed Condition for Potential Floodwater Intrusion into Vital Battery Rooms