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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 54938 | 8 October 2020 16:25:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Notification of an Unusual Event | At 1125 CDT on 10/8/20 Monticello Nuclear Generating Plant declared a Notification of an Unusual Event (NOUE) due to a Security Condition that did not involve a hostile action, due to a helicopter that hovered over the site for approximately 10 minutes. The unit remained at 100 percent power during the event. The licensee notified the NRC Resident Inspector, the Minnesota State Duty Officer and the Wright County and Sherburne County Sherriff departments of the event. Notified DHS SWO, FEMA Operations Center, CISA Central, FEMA NWC (email), DHS Nuclear SSA (email), and FEMA NRCC SASC (email).
At 1715 CDT Monticello Nuclear Generating Plant terminated the Notice of Unusual Event (HU1.1), upon confirmation through federal law enforcement and conversation with the aircraft owner that the aircraft in question was performing power line inspections for a different utility and was not a threat to the plant. Monticello determined that this condition did not meet the 1-hour reporting requirements of 10 CFR 73.71. Notified R3DO (Orlikowski), NRR EO (Miller), and IRD MOC (Gott). Additionally, notified DHS SWO, FEMA Operations Center, CISA Central, FEMA NWC (email), DHS Nuclear SSA (email), and FEMA NRCC SASC (email).
Monticello Nuclear Generating Plant (MNGP) is retracting this event notification based on subsequent information received that was not available at the time of the original notification. Following review of the additional information collected by the site through an investigation performed with input from local and federal law enforcement, Xcel Energy determined the helicopter did not constitute a credible threat or compromise site safety or security. There was no impact to public health or safety. The NRC Resident Inspector has been notified. The licensee will notify the State and county. Notified R3DO (Peterson). | ||
| ENS 44498 | 17 September 2008 15:17:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(a)(1)(i), Emergency Class Declaration 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Unusual Event Due to Loss of Shutdown Cooling | Monticello lost the 1R offsite power transformer due to an industrial accident that grounded the bus and resulted in a fatality of an employee onsite. At the time of this event, the 2R offsite transformer was already out of service due to a previous event (see EN #44484). This effectively resulted in a loss of all normal offsite power. The 1AR safety related offsite power source remained available and the safety related buses are energized and diesels are available. However, shutdown cooling was lost during the event due to a Group 2 isolation and cannot be restored. The shutdown cooling suction isolation valves #2020 and #2030 have power but until the Group 2 logic can be reset the valves cannot be reopened. The licensee needs to repower the RPS bus to reset the logic. Based on the uncertainty in reestablishing shutdown cooling an Unusual Event was declared based on Emergency Director judgment (EAL HU5.1). Current reactor coolant temperature is approximately 110 degrees with a heatup rate of about 20 degrees an hour. State and local authorities and the NRC resident inspector have been notified. The licensee will likely be making a press release.
On Wednesday, September 17, 2008 Monticello Nuclear Generating Plant (MNGP) experienced a loss of power to the station transformer resulting in a valid actuation of the following systems: Reactor Protection System (with the reactor shutdown), Containment Isolation, and Emergency Diesel Generators. The cause of the loss of power was due to contact of a 115kV transmission line by a manlift. A vendor employee was electrocuted. On-site Medical Emergency Response personnel responded until the individual was transported to North Memorial Medical Center. The individual was pronounced dead at North Memorial Medical Center. Notifications of offsite agencies and a media press release are in progress. 'This notification is being made in accordance 10CFR50.72(b)(2)(xi) and 10CFR50.72(b)(3)(iv)(A).' Licensee notified the NRC Resident Inspector." Notified R3IRC (Garza)
This is a follow-up to Event notification #44498. The station has completed notifications to off-site agencies and to the media. The station continues to troubleshoot and restore plant equipment and respond to media inquiries. NUE update - As of 1113 CDT shutdown cooling was restored." Notified R3 IRC.
Monticello Nuclear Generating Plant exited their Notification of Unusual Event at 1100 CDT on 9/21/08. The exit criteria is supported on the following information: (1) This event did not result in the loss or potential loss of a fission product barrier and did not change the status of the current fuel condition. All three fission barriers are intact and were maintained throughout the event. (2) There were no radiation releases as a result of the event. (3) Restoration of plant loads including shutdown cooling onto a normal offsite power source (the 1R transformer) has been completed. (4) The 1R transformer offsite power source was recovered and is being protected. Protection of the 1R transformer will continue until availability of the other offsite power source supplied from the 2RS/2R transformers has been restored. (5) Shutdown cooling is in service. (6) The site organization challenges in response to the injury event and loss of decay heat removal are no longer present. The licensee has notified the NRC Resident Inspector, as well as state and local agencies. A media release will be issued. Notified R3DO (Stone), NRR EO (Galloway), IRD MOC (Clark), OPA (Burnell), DHS (S. Moore), and FEMA (D. Fuller). | Reactor Protection System Emergency Diesel Generator Shutdown Cooling Decay Heat Removal | 05000263/LER-2008-007 |