ENS 52582
ENS Event | |
|---|---|
00:25 Mar 1, 2017 | |
| Title | Short Duration Loss of Secondary Containment Due to Severe Weather |
| Event Description | At 1825 [CST] on 02/28/2017, Dresden Station received unexpected alarm 923-5 C-1, RX BLDG DP LO [Reactor Building Differential Pressure Low]. Reactor Building differential pressure was observed to briefly lose vacuum and return to a normal reading of 0.6 inches vacuum water gauge. At the time of the transient, Grundy County was under a Severe Weather Warning and gusts of wind were being monitored from the Main Control Room up to approximately 57 mph. The Reactor Building differential pressure returned to [greater than or equal to] 0.25 inches vacuum water gauge at 18:25 after 18 seconds with no operator action. Operators observed differential pressure reading to lose vacuum, below 0 inches vacuum water gauge, for approximately 3 seconds.
This condition represents a failure to meet Surveillance Requirement 3.6.4.1.1. As a result, entry into Technical Specifications 3.6.4.1 condition A was made due to Secondary Containment being inoperable. This event is being reported in accordance with 10CFR50.72(b)(3)(v)(C) as a condition that could have prevented the fulfillment of a safety function. An issue report has been initiated and a 60-day Licensee Event Report will be submitted in accordance with 10CFR50.73(a)(2)(v)(C). The NRC Resident Inspector has been notified.
The purpose of this notification is to retract ENS notification 52582 made on 2/28/17 for Dresden Nuclear Power Station. The previous notification reported a potential loss of Reactor Building differential pressure due to high wind conditions and associated entry into Technical Specification 3.6.4.1 Condition A for failure to meet Surveillance Requirement 3.6.4.1.1 to maintain differential pressure above 0.25 inches vacuum water gauge. After further evaluation, it has been determined that the high winds caused a momentary low pressure pocket on the leeward side of the Reactor Building causing the differential pressure reading seen in the Main Control Room, but it did not challenge Reactor Building differential pressure or Secondary Containment. Reactor Building differential pressure indication utilizes four transmitters, one on each wall of the Reactor Building, and the most conservative reading is transmitted to the indicator in the Main Control Room. Wind conditions impacting a single transmitter would result in indication of low Reactor Building differential pressure in the Main Control Room. Procedures direct action to obtain local readings from all four Reactor Building differential pressure transmitters. After the low indication in the Main Control Room, Equipment Operators were dispatched to obtain local indication and all four transmitters were found to be indicating 0.6 inches vacuum water gauge. This was a short duration transient with no indications of an equipment failure that could impact Secondary Containment. The entire transient occurred within an 18 second window where differential pressure indication began at 0.6 inches vacuum water gauge, dropped to below 0 inches vacuum water gauge, and subsequently restored to 0.6 inches vacuum water gauge with no operator intervention. Furthermore, a significant change in Reactor Building differential pressure would impact readings on Drywell pressure because the Reactor Building pressure is used as a reference leg. Trends of Drywell pressure during the event indicated no adverse conditions implying that Reactor Building differential pressure was stable. Thus, it has been concluded that this was an indication issue and at no point during the transient would Secondary Containment have been unable to perform its safety function. Therefore, this event does not meet the criteria of 10 CFR 50.72(b)(3)(v)(C) as a condition that could have prevented the fulfillment of a safety function, and the ENS notification is being retracted. There is no longer a requirement for an associated 60-day Licensee Event Report in accordance with 10 CFR 50.73(a)(2)(v)(C). The NRC Resident Inspector has been notified. Notified R3DO (Jeffers). |
| Where | |
|---|---|
Dresden  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | |
| Time - Person (Reporting Time:+-2.85 h-0.119 days <br />-0.017 weeks <br />-0.0039 months <br />) | |
| Opened: | Tricia Loula 21:34 Feb 28, 2017 |
| NRC Officer: | Jeff Rotton |
| Last Updated: | Apr 14, 2017 |
| 52582 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 538512019-01-30T15:10:00030 January 2019 15:10:00
[Table view]10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Secondary Containment Inoperable ENS 525822017-03-01T00:25:0001 March 2017 00:25:00 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Short Duration Loss of Secondary Containment Due to Severe Weather ENS 523552016-11-08T11:10:0008 November 2016 11:10:00 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Reactor Building to Atmosphere Differential Pressure Out of Specifications ENS 517212016-02-10T03:42:00010 February 2016 03:42:00 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Secondary Containment Inoperable ENS 513742015-09-05T15:10:0005 September 2015 15:10:00 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Secondary Containment Inoperable Due to Loss of Vacuum from Open Inspection Hatch ENS 513712015-09-04T13:10:0004 September 2015 13:10:00 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Secondary Containment Inoperable Due to Both Airlock Doors Being Open Simultaneously ENS 499632014-03-27T06:51:00027 March 2014 06:51:00 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Failure of Secondary Containment Door Interlock ENS 495902013-11-28T08:58:00028 November 2013 08:58:00 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Secondary Containment Declared Inoperable While Two Secondary Containment Doors Were Simultaneously Open ENS 495432013-11-16T16:19:00016 November 2013 16:19:00 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Failure of Secondary Containment Interlock Mechanism ENS 495032013-11-05T14:42:0005 November 2013 14:42:00 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Secondary Containment Declared Inoperable Due to Failure of Interlock Mechanism ENS 493792013-09-23T21:55:00023 September 2013 21:55:00 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Both Secondary Containment Access Doors Opened Simultaneously ENS 491532013-06-28T12:49:00028 June 2013 12:49:00 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Door Interlock Malfunction Resulted in Brief Loss of Secondary Containment ENS 475402011-12-21T06:46:00021 December 2011 06:46:00 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Both Unit Two Secondary Containment Doors Were Inadvertently Left Open 2019-01-30T15:10:00 | |