ENS 51034
ENS Event | |
|---|---|
17:47 May 2, 2015 | |
| Title | Loss of Shutdown Cooling Due to Loss of 4Kv Bus |
| Event Description | {{#Wiki_filter:On 5/2/2015 at 1247 CDT, while the plant was in MODE 5 for a refueling outage with the vessel cavity flooded, during logic testing of the non-credited essential 4kV bus, MNGP [Monticello Nuclear Generating Plant] experienced a human performance error that caused a loss of the 4kV bus and essential load center. Loss of the load center de-energized valve position indication on one shutdown cooling isolation valve. This tripped the shutdown cooling pump on a pump suction interlock, resulting in the loss of shutdown cooling. This is being reported under 10 CFR 50.72(b)(3)(v)(B) as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat.
Following the event, the safety related load centers were cross-tied to allow restoration of shutdown cooling. Shutdown cooling was restored at 1603. While shutdown cooling was out of service, vessel water temperature rose approximately 10�F to 91.1�F, which is within the allowed temperature band. This event did not result in the release of any radioactive material and did not challenge the health and safety of the public. The NRC Resident Inspector has been notified. }}[[Event description::Description::{{#Regex_clear:On 5/2/2015 at 1247 CDT, while the plant was in MODE 5 for a refueling outage with the vessel cavity flooded, during logic testing of the non-credited essential 4kV bus, MNGP [Monticello Nuclear Generating Plant] experienced a human performance error that caused a loss of the 4kV bus and essential load center. Loss of the load center de-energized valve position indication on one shutdown cooling isolation valve. This tripped the shutdown cooling pump on a pump suction interlock, resulting in the loss of shutdown cooling. This is being reported under 10 CFR 50.72(b)(3)(v)(B) as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat. Following the event, the safety related load centers were cross-tied to allow restoration of shutdown cooling. Shutdown cooling was restored at 1603. While shutdown cooling was out of service, vessel water temperature rose approximately 10�F to 91.1�F, which is within the allowed temperature band. This event did not result in the release of any radioactive material and did not challenge the health and safety of the public. The NRC Resident Inspector has been notified. }}| ]] |
| Where | |
|---|---|
Monticello  Minnesota (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat | |
| Time - Person (Reporting Time:+3.17 h0.132 days <br />0.0189 weeks <br />0.00434 months <br />) | |
| Opened: | Lt. Dana Anton 20:57 May 2, 2015 |
| NRC Officer: | Howie Crouch |
| Last Updated: | May 2, 2015 |
| 51034 - NRC Website
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