ENS 50456
ENS Event | |
|---|---|
07:26 Sep 14, 2014 | |
| Title | Operation in Unanalyzed Region of the Power to Flow Map |
| Event Description | At 0226 CDT on September 14, 2014, MNGP [Monticello Nuclear Generating Station] experienced a trip of the 12 Reactor Recirc Pump. The subsequent power drop and lowering of recirculating water flow resulted in the plant being outside of the analyzed region of the Power to Flow Map. Operators promptly restored operation within the analyzed region per procedural guidance. This event has been determined to be a condition where the plant was in an unanalyzed condition that significantly degrades plant safety and is reportable under 50.72(b)(3)(ii). The plant is in stable condition at 51% power and the health and safety of the public were not affected. The investigation of the cause of this event is in progress.
The licensee will notify the NRC Resident Inspector.
Further analysis has determined that the condition did not significantly degrade plant safety. General Electric Hitachi was requested to review the event and confirm the SIL653 guidance remains applicable for MELLLA+ [Maximum Extended Load Line Limit Analysis] operation. This review was completed and the conclusions of SIL653 remain valid . The SIL states that: 'unplanned events that result in the plant exceeding the licensed upper boundary do not constitute a safety concern. The consequences of such unplanned events are bounded by the GE safety analysis of limiting events initiated from within the licensed operating domain. Stability monitoring and protection using Detection and Suppression Solution Confirmation Density remained available throughout the event (oscillating power range monitors). The NRC Resident Inspector has been notified. Notified R3DO (Hills). |
| Where | |
|---|---|
Monticello  Minnesota (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+3.62 h0.151 days <br />0.0215 weeks <br />0.00496 months <br />) | |
| Opened: | Randy Sand 11:03 Sep 14, 2014 |
| NRC Officer: | Dong Park |
| Last Updated: | Nov 10, 2014 |
| 50456 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (88 %) |
| After | Power Operation (51 %) |