ENS 42983
ENS Event | |
|---|---|
20:20 Nov 10, 2006 | |
| Title | Automatic Reactor Trip at Low Power |
| Event Description | On 11/10/2006 with a shutdown in progress to repair a degraded bearing on the turbine generator, an automatic reactor trip occurred due to a power range nuclear instrumentation (NI) low range - high flux trip. Reactor power had just been lowered to below 10% power (P-10) where the power range (NI) low range trips become active. The bistable for power range NI N-42 had been tripped due to an unrelated failure on 11/09/2006. When P-10 automatically unblocked, a power range NI low range high flux reactor trip was generated. At the time of the trip, reactor power was well below the trip setpoint of 24.5% power.
Following the trip, Main Feedwater Regulating Valve, FW-7A, did not automatically close as required on the reactor trip coincident with Low Tave (554F). The Reactor Operator reported FW-7A was mid-position and attempted to manually close FW-7A. It did not respond. As a result, levels in steam generator A rose to greater than 67%, which initiated feedwater isolation. The feedwater isolation signal tripped the running feedwater pump. With no feedwater pumps running, both Auxiliary Feedwater Pump A and Auxiliary Feedwater Pump B automatically started as required. The High-High steam generator level also resulted in a second reactor trip initiation signal. The Reactor Operator manually controlled Auxiliary Feedwater flow to steam generator A to restore normal level. Following the feedwater isolation, FW-7A fully closed. Following the trip, MS-201B1, the steam supply to main steam reheater B1 was locally isolated to limit the RCS cool down. This was a previously discussed contingency action. Main steam isolation valves remained open and normal condenser heat sink remained available. Further investigation as to the cause of the trip is in progress. Recovery actions per normal operating procedures are in progress. The plant was being shut down at a rate of a half percent power per minute at the time of the trip. All control rods fully inserted on the reactor trip and no safety or relief valves lifted. The plant was aligned for the normal shutdown electrical lineup prior to the trip. The temperature on the generator bearing reached a maximum of 190F with trip guidance set at 225F. The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Kewaunee  Wisconsin (NRC Region 3) | |
| 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:+-2.78 h-0.116 days <br />-0.0165 weeks <br />-0.00381 months <br />) | |
| Opened: | Scott Lieslewicz 17:33 Nov 10, 2006 |
| NRC Officer: | Mark Abramovitz |
| Last Updated: | Nov 10, 2006 |
| 42983 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (10 %) |
| After | Hot Shutdown (0 %) |
Kewaunee with 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
WEEKMONTHYEARENS 466662011-03-10T21:49:00010 March 2011 21:49:00
[Table view]10 CFR 50.72(b)(3)(iv)(A), System Actuation, 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Inadvertant Opening a Substation Breaker Causing Loss of Station Power ENS 454382009-10-15T17:04:00015 October 2009 17:04:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Momentary Loss of Shutdown Cooling with Autostart of Emergency Diesel Generator ENS 431962007-02-28T05:33:00028 February 2007 05:33:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Trip During the Performance of a Surveillance ENS 430962007-01-12T16:39:00012 January 2007 16:39:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Turbine Trip/Reactor Trip ENS 429832006-11-10T20:20:00010 November 2006 20:20:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip at Low Power ENS 429472006-10-30T14:48:00030 October 2006 14:48:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Trip ENS 425302006-04-27T01:49:00027 April 2006 01:49:00 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 Failure of Rps Signal to Initiate Reactor Trip ENS 421732005-11-29T04:20:00029 November 2005 04:20:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Following Main Feed Pump Trip ENS 414252005-02-20T17:58:00020 February 2005 17:58:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Rps Actuation on Steam Generator Low Level 2011-03-10T21:49:00 | |