ENS 51451
ENS Event | |
|---|---|
23:19 Aug 7, 2015 | |
| Title | 60-Day Optional Telephone Notification for an Invalid Containment Isolation Activation |
| Event Description | This 60-day telephone notification is being submitted in accordance with 10 CFR 50.73(a)(1) and 10 CFR 50.73(a)(2)(iv)(A) to report an invalid actuation of the Unit 2, Train B Containment Ventilation Isolation (CVI) at Sequoyah Nuclear Plant.
At 1919 EDT on August 7, 2015, during planned performance of a Unit 2 containment vent, the Train B CVI actuated due to an invalid Hi Rad signal from 2-RM-90-131, Containment Vent Radiation Monitor. In addition to the Train B CVI alarm, unexpected alarms were received for 2-RM-90-106, Lower Containment Radiation Monitor and 2-RM-90-112, Upper Containment Radiation Monitor instrument malfunctions as they isolated for the CVI and 2-RM-90-131 Hi Rad alarm. Prior to the invalid Hi Rad alarm, all radiation monitors were stable at their normal values. All required automatic actuations occurred as designed. Upon investigation, the cause of the invalid Hi Rad alarm was due to an exposed shield wire at the 2-RM-90-131 detector. Preventative maintenance had been performed the week prior to the CVI and it is believed the damage occurred at that time. Control Room Operators performed Annunciator Response actions and verified by diverse indications that the subject condition was an invalid Hi Rad signal. There were no indications of degraded reactor coolant system parameters or fuel failure. Applicable Technical Specification (TS) Limiting Condition for Operations (LCOs) were entered and the radiation monitors declared inoperable. No Emergency Response criteria were applicable with the subject radiation monitors inoperable. Radiological surveys performed in the vicinity of 2-RM-90-131 verified no abnormal radiological conditions. Radiation Monitor 2-RM-90-131 was removed from service, the shield wire was repaired and returned to service with no issues. Radiation Monitors 2-RM-90-106 and 2-RM-90-112 were tested and returned to service. The applicable TS LCOs were exited. At the time of the event, plant conditions for a Hi Rad alarm did not exist; therefore, the CVI was invalid. The NRC Resident Inspector was notified. |
| Where | |
|---|---|
Sequoyah  Tennessee (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+1402.68 h58.445 days <br />8.349 weeks <br />1.921 months <br />) | |
| Opened: | Kevin Michael 10:00 Oct 5, 2015 |
| NRC Officer: | Vince Klco |
| Last Updated: | Oct 5, 2015 |
| 51451 - NRC Website | |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 551302021-01-11T16:52:00011 January 2021 16:52:00
[Table view]10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Telephonic Notification for Invalid Containment Ventilation Isolation Actuation ENS 514512015-08-07T23:19:0007 August 2015 23:19:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Telephone Notification for an Invalid Containment Isolation Activation ENS 511172015-04-12T17:20:00012 April 2015 17:20:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Telephonic Notification for an Invalid Containment Isolation Activation. ENS 470222011-06-04T19:17:0004 June 2011 19:17:00 10 CFR 50.73(a)(1), Submit an LER Invalid Specified System Actuation Caused All 4 Emergency Diesel Generators to Start ENS 472492011-05-05T19:20:0005 May 2011 19:20:00 10 CFR 50.73(a)(1), Submit an LER Invalid Specified System Actuation ENS 465042010-11-14T10:09:00014 November 2010 10:09:00 10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of Turbine Driven Auxiliary Feedwater Pump ENS 450852009-04-09T05:15:0009 April 2009 05:15:00 10 CFR 50.73(a)(1), Submit an LER Optional 60-Day Telephone Report of an Invalid Start of All Four Emergency Diesel Generators 2021-01-11T16:52:00 | |