ENS Event | |
|---|---|
19:13 Aug 30, 2007 | |
| Title | Automatic Reactor Scram on Turbine Stop Valve Closure |
| Event Description | Event Description:
Reactor scram (4 hr notification) automatic scram Primary containment isolation of Groups 2,3,4, and 5 due to RPV Level < low level setpoint (<127") due to reactor scram. (8 hr notification). Actions Taken (reference applicable Technical Specifications): Implemented OT 3100 (Reactor Scram Procedure) EOP-1 (RPV Control). Placed the plant in a stable condition and implemented OP 0109, Plant Restoration. The NRC Resident Inspector was notified of this event by the licensee. Reactor was initially at approximately 63% power due to cooling tower damage which occurred more than a week ago. License was performing a surveillance test of the # 2 turbine stop valve. The valve was shut per the surveillance test procedure but they were unable to open the valve. Personnel were in the heater bay and mechanical assistance was applied to open the valve. The valve opened quickly at which point the licensee received a turbine stop valve closure signal which generated an automatic reactor scram. All rods fully inserted into the core. Reactor vessel water level decreased below 127 inches, due to the reactor scram, which caused primary containment isolation of groups 2,3,4 and 5. Reactor vessel water began to increase because Reactor feedwater pumps "A" & "B" were still operating. Reactor feedwater pump "B" was secured. When reactor vessel water increased to 173 inches, high level alarm, reactor feedwater pump "A" automatically tripped. Highest reactor vessel water level increased to was approximately 179 inches. No SRV's opened. All Emergency Core Cooling Systems, EDGs are fully operable if needed and the electrical grid is stable. Reactor vessel water level is being maintained using a reactor feedwater pump. Only other anomaly was that for some unknown reason automatic pressure control went to mechanical pressure control during the transient. Licensee is investigating the event. |
| Where | |
|---|---|
| Vermont Yankee File:NorthStar Vermont Yankee icon.png Vermont (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(iv)(B), RPS Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| Time - Person (Reporting Time:+-1.95 h-0.0813 days <br />-0.0116 weeks <br />-0.00267 months <br />) | |
| Opened: | M. Pletcher 17:16 Aug 30, 2007 |
| NRC Officer: | John Mackinnon |
| Last Updated: | Aug 30, 2007 |
| 43610 - NRC Website
Loading map... | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (62 %) |
| After | Hot Shutdown (0 %) |
Vermont YankeeFile:NorthStar Vermont Yankee icon.png with 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
WEEKMONTHYEARENS 459572010-05-26T19:26:00026 May 2010 19:26:00
[Table view]10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Scram While Increasing Power ENS 436102007-08-30T19:13:00030 August 2007 19:13:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Scram on Turbine Stop Valve Closure ENS 418682005-07-25T04:00:00025 July 2005 04:00:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation, 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge Automatic Reactor Trip Caused by Failure in Switchyard 2010-05-26T19:26:00 | |
