ENS 42995
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ENS Event | |
|---|---|
05:18 Nov 16, 2006 | |
| Title | Reactor Trip Due to Turbine Trip and Discovery of After-The-Fact Emergency Condition of an Unsual Event |
| Event Description | At 0018 Calvert Cliffs Unit 2 experienced an automatic reactor trip due to a turbine trip. "At the time a clearance order was being performed for upcoming maintenance on P-13000-2 [transformer]. As a result of the turbine trip, RCS pressure rose to approximately 2420 psia causing the PORV's to open. Unexpectedly, a Pressurizer Safety Valve, RV-200 also lifted and reclosed when RCS pressure was lowered to approximately 1500 psia. As a result of the pressure decrease, a Safety Injection Actuation Signal (SIAS) occurred. Once the Pressurizer Safety Valve reclosed, RCS pressure began to rise to return to normal values.
Decay heat is being removed via normal methods through the Turbine Bypass Valves to the Condenser. Normal Feedwater is being used. No Auxiliary Feedwater actuation occurred. Two Reactor Coolant Pumps were secured as a result of the SIAS. The plant responded normally to the event. The plant is currently stable and operators are conducting a plant cooldown to mode 5. All control rods fully inserted. The licensee notified the NRC Resident Inspector.
The automatic trip was due to high RCS pressure from the closure of the Turbine Intercept Valves. Both PORV's opened as designed. One remained open approximately 1.5 minutes causing RCS pressure to reduce to 1500 psia. The PORV should have closed at 2400 psia. Relief Valve 200 (RV-200) did not open as previously reported and was not the cause of the RCS pressure lowering. Acoustic monitoring indication were due to the close proximity of the PORV. Since the SIAS signal did not cause a reportable ECCS actuation, the reported 50.72(b)(2)(iv)(A) ECCS Actuation is retracted. The licensee notified the NRC Resident Inspector. Notified R1DO (P. Henderson).
Upon further review, the licensee has determined that this event met the criteria for Unusual Event Emergency Action Level (EAL A.U.2.2.1) for identified RCS leakage greater than 25 gpm. The licensee met this criteria for the duration that the PORV valve remained open (less than 2 minutes). The licensee did not recognize that it had met the criteria at the time of the event and is reporting this as an after-the-fact emergency condition of unusual event per the guidance in NUREG-1022. The licensee notified the NRC Resident Inspector. Notified R1DO (P. Henderson), NRR EO (Ross-Lee), and IRD Manager (Leach). |
| Where | |
|---|---|
Calvert Cliffs  Maryland (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(iv)(B), RPS Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| LER: | 05000318/LER-2006-001 |
| Time - Person (Reporting Time:+-2.27 h-0.0946 days <br />-0.0135 weeks <br />-0.00311 months <br />) | |
| Opened: | Kevin Umphrey 03:02 Nov 16, 2006 |
| NRC Officer: | Bill Gott |
| Last Updated: | Nov 17, 2006 |
| 42995 - NRC Website | |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (100 %) |
| After | Hot Standby (0 %) |
Calvert Cliffs with 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
WEEKMONTHYEARENS 569972024-02-28T18:50:00028 February 2024 18:50:00
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Remove Residual Heat, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Dual Unit Automatic Reactor Trips Due to a Voltage Transient Resulting in Generator Trips ENS 500782014-05-01T14:16:0001 May 2014 14:16:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip ENS 497542014-01-22T02:25:00022 January 2014 02:25:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Dual Unit Trip on the Loss of the "21" 13Kv Bus ENS 490542013-05-21T09:33:00021 May 2013 09:33:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip After a Feed Pump Trip ENS 490122013-05-09T01:47:0009 May 2013 01:47:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip ENS 472082011-08-28T03:02:00028 August 2011 03:02:00 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 - Transformer Explosion Near Turbine Building ENS 459202010-05-12T17:51:00012 May 2010 17:51:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Rps Actuation - Load Reject ENS 457092010-02-18T13:24:00018 February 2010 13:24:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Dual Unit Automatic Reactor Trips Due to Partial Loss of Offsite Power ENS 430462006-12-12T14:07:00012 December 2006 14:07:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip During Turbine Control System Maintenance ENS 429952006-11-16T05:18:00016 November 2006 05:18:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Trip Due to Turbine Trip and Discovery of After-The-Fact Emergency Condition of an Unsual Event ENS 414522005-03-01T05:43:0001 March 2005 05:43:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Scram from 15% Power Due to High Turbine Vibration ENS 406012004-03-20T18:40:00020 March 2004 18:40:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Trip at Calvert Cliffs Unit 1 Due to a Loss of Feedwater ENS 404722004-01-23T20:29:00023 January 2004 20:29:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip with Safety Injection Actuation Signals 2024-02-28T18:50:00 | |
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