ENS 48809
ENS Event | |
|---|---|
10:01 Mar 6, 2013 | |
| Title | Momentary Loss of Shutdown Cooling |
| Event Description | At 0401 CST on 3/6/2013, while in RHR-High [Residual Heat Removal-High] water level the plant experienced a momentary Loss of Shutdown Cooling which resulted in a loss of safety function for Residual Heat Capability. Division 2 RHR shutdown cooling was restored within approximately 90 seconds without issue. No changes were experienced in refuel volume temperature or level during the loss of RHR shutdown cooling. This occurred shortly after a flow adjustment on the system was made utilizing the outboard valve. The inboard valve was reopened and an investigation is in progress. At the time of the valve closure, decay heat removal continued from Reactor Water Cleanup in heat reject mode and fuel pool cooling (with the fuel pool gates removed) is in service. Division 1 RHR (Shutdown Cooling) was available (not Operable) at the time of the loss. It is not currently understood why the injection valve closed. All systems functioned as required except for the spurious closing of MO-2015 (the Div 2 RHR inboard injection valve). The following make-up sources are available: Divisions 1 and 2 RHR, Divisions 1 and 2 Core Spray, CRD [Control Rod Drive], CST [Condensate Storage Tank] via a Core Spray with pressurizing station bypassed.
The licensee notified the NRC Resident Inspector.
On March 6, 2013 (Notification No. 48809) NSPM [Northern States Power Monticello] reported in accordance with 10 CFR 50.72 (b)(3)(v)(B), a momentary closure of valve MO-2015 in the operating Residual Heat Removal (RHR) subsystem as an event or condition that at the time of discovery could have prevented the fulfillment of a safety function. Following the event, the RHR SDC [shut down cooling] subsystem was removed from operation for equipment forensics and troubleshooting. Results validated that valve MO-2015 was operable and no issues were identified with the associated electrical circuitry, or the RHR SDC subsystem. The decay heat removal requirements of LCO 3.9.7, RHR - High Water Level, were met and there was not a loss of safety function. Therefore, NSPM retracts the March 6, 2013 notification for this event. The licensee notified the NRC Resident Inspector, state and local authorities, and may make a press release. Notified the R3DO (Passehl). |
| 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:+2.85 h0.119 days <br />0.017 weeks <br />0.0039 months <br />) | |
| Opened: | Jack Earsley 12:52 Mar 6, 2013 |
| NRC Officer: | Vince Klco |
| Last Updated: | Apr 11, 2013 |
| 48809 - NRC Website | |