ENS 53485
ENS Event | |
|---|---|
05:00 Jul 3, 2018 | |
| Title | En Revision Imported Date 8/1/2018 |
| Event Description | EN Revision Text: DISCOVERY OF AN UNANALYZED CONDITION THAT SIGNIFICANTLY DEGRADES PLANT SAFETY
On July 3, 2018, while performing a review of Emergency Operating Procedures, a concern was identified regarding the potential for excessive loss of ultimate heat sink inventory (UHS) through the auxiliary feedwater (AFW) system mini-flow recirculation pathway. This condition would have the potential to prevent the ultimate heat sink from providing an adequate inventory of water for a 30-day mission time. The normal water supply for the Callaway AFW system is the condensate storage tank (CST). The CST is a non-safety grade component. The safety-grade supply for AFW is the essential service water (ESW) system. The ESW system is supplied by the UHS. The UHS thermal performance analysis accounts for a loss of UHS inventory to the AFW system up until the point of the accident sequence that the AFW pumps would be secured. The analysis did not include an allowance for loss of UHS inventory through the AFW mini-flow recirculation pathway following the AFW pumps being secured. The EOP guidance that secures the AFW pumps does not isolate the mini-flow recirculation pathway. Initial estimates indicate that loss of UHS inventory through the mini-flow recirculation pathway, if not isolated, would preclude the UHS from completing its 30-day mission time. This potential for depletion of the UHS placed the plant in an unanalyzed condition that significantly degraded safety. Callaway has issued interim guidance to the on-shift personnel regarding this concern to ensure that the ultimate heat sink water level is maintained at a level that will be adequate to mitigate the potential loss of inventory. This condition is reportable per 10 CFR 50.72(b)(3)(ii)(B) for an unanalyzed condition that significantly degrades safety. The NRC Resident Inspectors have been notified of this condition.
Event Notification (EN) 53485, made on July 3, 2018, is being retracted because re-evaluation performed subsequent to the notification has demonstrated, based on actual plant equipment and environmental conditions, that the unanalyzed inventory losses previously reported by EN 53485 would not have depleted the UHS inventory to an unacceptable level during its 30-day mission time. The re-evaluation has led to the conclusion that the previously unanalyzed losses of UHS inventory would not have prevented the UHS from performing its specified safety functions and meeting its 30-day mission time requirements. With the UHS capable of performing its specified safety functions and meeting its 30-day mission time requirements, the systems supported by the UHS would have remained capable of performing their specified safety functions. Based on these considerations, it has been determined that the condition reported in EN 53485 did not result in the plant being in an unanalyzed condition that significantly degraded safety. Consequently, the condition did not meet the criteria for an 8-hour notification per 10 CFR 50.72(b)(3)(ii)(B) for an unanalyzed condition that significantly degrades safety. The NRC Resident Inspector has been notified of the Event Notification retraction. Notified R4DO (Gaddy). |
| Where | |
|---|---|
Callaway  Missouri (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+14.12 h0.588 days <br />0.084 weeks <br />0.0193 months <br />) | |
| Opened: | Jeremy Czeschin 19:07 Jul 3, 2018 |
| NRC Officer: | Vince Klco |
| Last Updated: | Jul 31, 2018 |
| 53485 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 548062020-07-30T13:15:00030 July 2020 13:15:00
[Table view]10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition ENS 534852018-07-03T05:00:0003 July 2018 05:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition En Revision Imported Date 8/1/2018 ENS 532232018-02-20T18:25:00020 February 2018 18:25:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition All Three Auxiliary Feedwater Pumps Inoperable Due to Helb Door Being Open ENS 529052017-08-15T16:46:00015 August 2017 16:46:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Discovery of Non-Conforming Conditions During Tornado Hazards Analysis ENS 526072017-03-13T18:58:00013 March 2017 18:58:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Discovery of Non-Conforming Conditions During Tornado Hazards Analysis ENS 518742016-04-20T19:05:00020 April 2016 19:05:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to Essential Service Water Pressure Transient ENS 506252014-11-19T01:00:00019 November 2014 01:00:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to All Four Safety Injection Accumulators Inoperable ENS 504742014-09-19T16:34:00019 September 2014 16:34:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to a Postulated Hot-Short Fire Event That Could Adversely Impact Safe Shutdown Equipment ENS 494222013-10-09T20:00:0009 October 2013 20:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Postulated Fire Event Could Result in a Hot Short That Could Adversely Impact Safe Shutdown Equipment ENS 478852012-05-01T18:00:0001 May 2012 18:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Floor Drain Blockage Adversely Affects Asumptions of Pipe Break Analysis for Electrical Switghear Rooms ENS 477832012-03-28T20:00:00028 March 2012 20:00:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Degraded Condition Identified in the B Train Containment Cooler Units ENS 474262011-11-09T23:50:0009 November 2011 23:50:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Potential Failure of High Density Polyethylene Piping in Esw System ENS 470842011-07-21T16:00:00021 July 2011 16:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Potential Adverse Effect on Esw Train During a Postulated Control Room Fire ENS 467152011-03-31T19:32:00031 March 2011 19:32:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Identified for Inoperable Rwst Level ENS 466932011-03-24T04:54:00024 March 2011 04:54:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Pressure Transmitters Needed for Auxiliary Feedwater Suction Path Not Analyzed for Potential High Energy Line Break ENS 465972011-02-07T15:18:0007 February 2011 15:18:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition High Energy Line Break Analysis for Aux Steam to the Auxiliary Building ENS 457472010-03-05T19:25:0005 March 2010 19:25:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition - Steam Supply Valve Credited as Closed in Fsar Analysis Is Normally Open During Operations ENS 455712009-12-15T20:30:00015 December 2009 20:30:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Helb Configuration Calculations Not Consistent with Previous Helb Analysis ENS 422422006-01-04T19:45:0004 January 2006 19:45:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Related to Emergency Diesel Fuel Oil Tank Vortex Formation ENS 413262005-01-12T19:30:00012 January 2005 19:30:00 Other Unspec Reqmnt, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition 24 Hour Condition of License Report Regarding Halon System Actuator Port Connection Error ENS 403732003-12-03T18:30:0003 December 2003 18:30:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Emergency Procedure Deficiency Causes Unanalyzed Condition 2020-07-30T13:15:00 | |