ENS 46417
ENS Event | |
|---|---|
18:10 Nov 12, 2010 | |
| Title | Unanalyzed 10Cfr50 Appendix R Scenario |
| Event Description | At approximately 1210 on November 12, 2010, a fire protection assessment identified a potentially unanalyzed condition in the plant's 10CFR50 Appendix R analysis. In the unlikely event of a fire in the main control room or cable spreading room, coincident with a fire induced loss of off site power, in which the control room must be evacuated, Operations personnel would proceed to the Alternate Shutdown System (ASDS) panel to perform required safe shutdown activities. During certain scenarios, High Pressure Coolant Injection (HPCI) may start on a reactor low-low water level signal or on high drywell pressure signal. Since HPCI is not controlled manually from the ASDS, a postulated fire induced short could prevent the HPCI system high reactor water level trip and possibly result in reactor vessel overfill.
Operation of the Safety Relief Valves in this condition has not been analyzed. For this scenario, the following unlikely sequence of events is required: 1. A fire would have to occur in the main control room or cable spreading room 2. The fire would have to be significant enough to require main control room evacuation 3. Offsite power would have to be lost 4. HPCI would have to initiate 5. A fire induced short preventing HPCI from tripping automatically would have to occur Applicable safety systems remain operable, and Operations personnel are trained in procedures to handle complex fire scenarios, including fires in the main control room and cable spreading room. Additionally, the cable spreading room is protected by an automatic Halon fire suppression system. As a precaution, a fire watch has been established as a compensatory measure. This event is being reported under 10CFR50.72(b)(3)(ii)(B). The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Monticello  Minnesota (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+2.53 h0.105 days <br />0.0151 weeks <br />0.00347 months <br />) | |
| Opened: | Martin Rajkowski 20:42 Nov 12, 2010 |
| NRC Officer: | Donald Norwood |
| Last Updated: | Nov 12, 2010 |
| 46417 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (47 %) |
| After | Power Operation (47 %) |