ENS 40340
ENS Event | |
|---|---|
18:30 Nov 19, 2003 | |
| Title | Two Failure Modes Not Previously Postulated Could Be Introduced by a Fire in Either Fire Zone 19 or Fire Zone 20. |
| Event Description | At approximately 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> (EDT) on November 19, 2003, during reviews being conducted on H. B. Robinson Steam Electric Plant (HBRSEP), Unit 2 No. 2, Appendix R fire scenario safe shutdown circuit analysis, it was concluded that two failure modes not previously postulated could be introduced by a fire in either Fire Zone 19, Cable Spreading Room, or Fire Zone 20, Emergency Switchgear Room. The suction source to the charging pump could spuriously close during a fire in one of these zones, which could cause a loss of Reactor Coolant System (RCS) make-up capability of the "A" Charging Pump were operating at the time if the event. The other failure mode involves spurious operation of both pressurizer power operated relief valves (PORVs), which could cause a loss of RCS inventory. Each of these failure modes could result in loss of safe shutdown capability. Therefore, this condition is being reported in accordance with 10 CFR 50.72(b)(3)(v)(A), any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are required to shut down the reactor and maintain it in safe shutdown condition.
Short term corrective actions for this situation include procedure changes to establish preemptive actions that will provide reasonable assurance that safe shutdown can be achieved and maintained. The procedure changes will include rapid verification at the onset of a fire scenario that the "A" Charging Pump is not operating, and will direct closure of the pressurizer PORV block valves. Additionally, the Fire Protection Program (FPP) requirements for loss of detection or suppression in these zones were reviewed. The FPP requires establishment of a continuous fire watch in these areas for loss of detection or suppression capability. Additional administrative controls will be implemented or transient combustibles to further reduce the probability of these failure modes occurring. Long term corrective actions are being developed via the Corrective Action Program and will be implemented to further reduce the likelihood of these failure modes The NRC Resident Inspector was notified of this event by the licensee. |
| Where | |
|---|---|
Robinson  South Carolina (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor | |
| Time - Person (Reporting Time:+-4.12 h-0.172 days <br />-0.0245 weeks <br />-0.00564 months <br />) | |
| Opened: | Chuck Baucom 14:23 Nov 19, 2003 |
| NRC Officer: | John Mackinnon |
| Last Updated: | Nov 19, 2003 |
| 40340 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 403402003-11-19T18:30:00019 November 2003 18:30:00
[Table view]10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor Two Failure Modes Not Previously Postulated Could Be Introduced by a Fire in Either Fire Zone 19 or Fire Zone 20. 2003-11-19T18:30:00 | |