ENS 40156
ENS Event | |
|---|---|
01:55 Sep 13, 2003 | |
| Title | Manual Reactor Trip Due to Unanticipated Negative Axial Shape Index (Asi). |
| Event Description | This report is being made pursuant to 10 CFR 50.72(b)(2)(iv)(B) due to manual initiation of the RPS, although briefed, was not part of any written pre-planned sequence. The unanticipated negative ASI response that began to approach RPS APD trip settings drove the decision to manually initiate an RPS trip.
Fort Calhoun Station Unit 1 was being shutdown for a planned refueling outage. During scheduled power shutdown at 3% per hour, ASI was trending more negative (power shifting to top of core) than expected. Reactor Engineering was contacted about the trend at 67% reactor power on September 11, 2003. New guidance was issued, however negative ASI trend continued. RPS Axial Power Distribution (APD) pretrip/trip setpoints were -0.55/-0.58 ASI Units. Below 15% power APD trips are bypassed. Operations briefed the continued power descension with manual trip criteria being the receipt of any 1 of 4 APD pretrip setpoints. At 15.8% delta T power it became apparent that with ASI approaching APD pretrips (-0.5305 ASIU recorded), an Automatic Trip could be initiated if the downpower continued. At 2055 on September 12, 2003, with power at 15.8% delta T, a briefing was conducted and an manual reactor trip was initiated by tripping the Primary RPS Trip pushbutton on Control Board-4. Operations entered EOP-00, "Standard Post Trip Actions" and transitioned to EOP-01, "Reactor Trip Recovery" with all safety functions verified. EOP-01 was exited at 2200 hours0.0255 days <br />0.611 hours <br />0.00364 weeks <br />8.371e-4 months <br /> and the plant entered OP-3A, "Plant Trip". The plant is currently stable in Mode 3 with RCS Tave at 535 degrees F. The only abnormal plant response noted was a feedwater side relief valve lifted and failed to fully reseat on FW-16A, High Pressure Feedwater Heater. The relief valve was cycled by maintenance and was reseated approximately 10 minutes after opening. The NRC Resident Inspector was notified of this event by the licensee. |
| Where | |
|---|---|
Ft Calhoun  Nebraska (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(iv)(B), RPS Actuation | |
| Time - Person (Reporting Time:+4.25 h0.177 days <br />0.0253 weeks <br />0.00582 months <br />) | |
| Opened: | Chris Verdoni 06:10 Sep 13, 2003 |
| NRC Officer: | John Mackinnon |
| Last Updated: | Sep 13, 2003 |
| 40156 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | Yes, Manual Scram |
| Before | Power Operation (16 %) |
| After | Hot Standby (0 %) |
WEEKMONTHYEARENS 520332016-06-22T13:41:00022 June 2016 13:41:00
[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 Trip Due to Turbine Trip ENS 506882014-12-17T16:14:00017 December 2014 16:14:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Due to Loss of Load ENS 499262014-03-17T17:02:00017 March 2014 17:02:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Due to Turbine Trip Initiated by Loss of Stator Cooling Water ENS 497172014-01-12T09:23:00012 January 2014 09:23:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Following Control Rod Position Deviation ENS 465062010-12-23T16:50:00023 December 2010 16:50:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Uncomplicated Reactor Trip from 100% Power ENS 458282010-04-08T21:22:0008 April 2010 21:22:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition, 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Technical Specification Required Shutdown Due to Inoperable Steam Generator Inlet Isolation Valve ENS 440662008-03-15T13:33:00015 March 2008 13:33:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Reactor Trip Due to Turbine Trip ENS 414462005-02-27T03:34:00027 February 2005 03:34:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Plant Had a Reactor Trip from 16.1% Power Due to a Loss of Turbine Load Signal ENS 401562003-09-13T01:55:00013 September 2003 01:55:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip Due to Unanticipated Negative Axial Shape Index (Asi). 2016-06-22T13:41:00 | |