ENS 50866
ENS Event | |
|---|---|
10:06 Mar 5, 2015 | |
| Title | Unit 2 Declares Unusual Event Due to Inability to Validate a Containment Fire Alarm within 15 Minutes |
| Event Description | The Instrument Air Containment Isolation failed closed on Unit 2. This isolated normal letdown / excess letdown and required Pressurizer level to be maintained by diverting Pressurizer level to the Pressurizer Relief Tank. The Pressurizer Relief Tank rupture disc ruptured which resulted in a fire alarm in Unit 2 Containment. The fire alarm could not be validated within 15 minutes which resulted in a declaration of an Unusual Event based on EAL HU2.1. The loss of Instrument Air to Unit 2 Containment resulted in a loss of cooling to the reactor vessel gap and support cooling systems. Due to the loss of reactor vessel ventilation systems a plant shutdown to Mode 3 has been initiated. No radioactive releases to the environment are in progress or expected to occur. The public health and safety has not been jeopardized.
The licensee informed state/local agencies and the NRC Resident Inspector and does plan to issue a press release. Notified other Federal Agencies (DHS SWO, FEMA Ops, FEMA NWC, NICC Watch Officer and NuclearSSA).
At 1725 [CST] on 3/5/15 Instrument Air to Unit 2 containment was established. Letdown was then reestablished. These actions stabilized the plant and stopped the 30 GPM [gallons per minute] identified leakage out of the PZR Relief Tank rupture disc into containment. This condition is what caused the fire detection alarm in containment, and is also Unusual Event criteria. Unit 2 containment was entered and it was confirmed that NO fire existed in containment. The Unusual Event was terminated at 0018 CST on 3/6/15 based on no fire and no identified RCS leakage into containment. The plant is currently in Mode 3. The health and safety of the public was not jeopardized. The licensee informed state/local agencies and the NRC Resident Inspector and does plan to issue a press release. Notified R3DO (Stone), EO (Ross-Lee) and IRD (Stapleton). Notified other Federal Agencies (DHS SWO, FEMA Ops, FEMA NWC, NICC Watch Officer and NuclearSSA). |
| Where | |
|---|---|
Prairie Island  Minnesota (NRC Region 3) | |
| Reporting | |
| Emergency class: | Unusual Event |
| 10 CFR 50.72(a) (1) (i), Emergency Class Declaration | |
| Time - Person (Reporting Time:+-4.52 h-0.188 days <br />-0.0269 weeks <br />-0.00619 months <br />) | |
| Opened: | Darrell Lapcinski 05:35 Mar 5, 2015 |
| NRC Officer: | Steve Sandin |
| Last Updated: | Mar 6, 2015 |
| 50866 - NRC Website | |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (92 %) |
WEEKMONTHYEARENS 565432023-05-27T23:34:00027 May 2023 23:34:00
[Table view]10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Notification of Unusual Event Due to Multiple Fire Alarms in Containment Not Verified within 15 Minutes ENS 521782016-08-14T04:59:00014 August 2016 04:59:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Declared Due to Excessive Reactor Coolant System Leakage ENS 516092015-12-17T19:18:00017 December 2015 19:18:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unusual Event Declared Due to Fire Alarm in Containment Not Verified within 15 Minutes ENS 508662015-03-05T10:06:0005 March 2015 10:06:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unit 2 Declares Unusual Event Due to Inability to Validate a Containment Fire Alarm within 15 Minutes ENS 484642012-10-31T19:18:00031 October 2012 19:18:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Notice of Unusual Event Due to Security Condition ENS 477202012-03-06T12:24:0006 March 2012 12:24:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Notification of Unusual Event Due to Unidentified Rcs Leakage Greater than 10 Gpm ENS 475692012-01-05T09:53:0005 January 2012 09:53:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Sodium Hypochlorite Leak Resulted in Airborne Concentrations Potentially Dangerous to Life and Health ENS 443802008-08-03T08:52:0003 August 2008 08:52:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event - Hydrazine Leak in Non-Vital Area of the Turbine Building 2023-05-27T23:34:00 | |