ENS 45855
ENS Event | |
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03:25 Apr 19, 2010 | |
Title | Lco 3.0.3 Entry And Loss Of Safety Function Due To Loss Of Turbine Building High Energy Line Break Compensatory Measure |
Event Description | At 2225 CDT on 4/18/2010, Operations discovered that the Unit 1 Turbine Building Truck Aisle Rollup Door Security Fence was closed. This fence was to be maintained open as the truck aisle is a required drainage path from the Unit 1 Turbine Building to outside in the event of flooding resulting from a High Energy Line Break (HELB). With the expanded metal mesh door [fence] closed, turbine building debris could clog the drainage path and result in a higher than calculated water level being reached for this event. As the final water level cannot be predicted, this represented an unanalyzed condition. The higher water levels would be reached at least one hour after the postulated turbine building HELB event. High water levels could result in a Loss of Safety Function for Unit 1 Emergency Diesel Generators. Auxiliary Feedwater (both units) and DC Electrical Power (both units) if water levels exceed critical heights in the associated rooms.
The doors [fence] were reopened at 2227 CDT. Unit 1 entered LCO 3.0.3 for this two minute period. With the doors [fence] opened, Unit 1 and 2 LCO conditions were again satisfied. The Unit 2 truck aisle was in the assumed condition, and Unit 2 is in Mode 5 so loss of AFW or DC power would not result in an LCO 3.0.3 entry. Unit 2 Emergency Diesel Generators are not affected as the Unit 2 truck aisle drain path would prevent water levels from reaching critical heights. The initial investigation determined that a Security Officer had closed the gate at approximately 1855 CDT on 4/18/2010. The NRC Resident Inspector has been notified. A press release is not planned.
In reference to the 4/18/2010 discovery of the security fences (screen door) closed on the Unit One Turbine Building truck aisle door and the Tech Spec LCO 3.0.3 entry on Unit One, further analysis of HELB flooding scenarios in the plant configuration known to be in effect at that time has shown that the LCO 3.0.3 entry was not warranted. Engineering analysis demonstrates that water levels in the Unit One Turbine Building from a postulated worst case HELB flooding event would only have rendered the 12 Motor Driven Auxiliary Feedwater Pump inoperable. Thus TS LCO 3.7.5 Condition B would have been the only LCO action statement required to be entered. No loss of safety function existed." The licensee will notify the NRC Resident Inspector. Notified the R3DO (Skokowski). |
Where | |
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Prairie Island ![]() Minnesota (NRC Region 3) | |
Reporting | |
10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
Time - Person (Reporting Time:+-0.22 h-0.00917 days <br />-0.00131 weeks <br />-3.01356e-4 months <br />) | |
Opened: | John Kempkes 03:12 Apr 19, 2010 |
NRC Officer: | Donald Norwood |
Last Updated: | Apr 22, 2010 |
45855 - NRC Website
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Unit 1 | |
---|---|
Reactor critical | Critical |
Scram | No |
Before | Power Operation (100 %) |
After | Power Operation (100 %) |
Prairie Island ![]() | |
WEEKMONTHYEARENS 555292021-10-18T00:30:00018 October 2021 00:30:00
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Shutdown the Reactor Battery Rooms Declared Inoperable Due to Potential Flooding ENS 459372010-05-19T21:40:00019 May 2010 21:40:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Both Trains of Residual Heat Removal (Rhr) Inoperable ENS 458552010-04-19T03:25:00019 April 2010 03:25:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Lco 3.0.3 Entry and Loss of Safety Function Due to Loss of Turbine Building High Energy Line Break Compensatory Measure ENS 455672009-12-14T18:00:00014 December 2009 18:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Related to Certain Fire Conditions ENS 449312009-03-23T22:00:00023 March 2009 22:00:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition for Postulated Missile Hazard That Could Disable Both Trains of Component Cooling ENS 448592009-02-17T17:00:00017 February 2009 17:00:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - 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