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| Entered date | Event description | |
|---|---|---|
| ENS 54220 | 14 August 2019 20:00:00 | This 60-day telephone notification is being submitted in accordance with paragraphs 10 CFR 50.73(a)(1) and 50.73(a)(2)(iv)(A) to report an invalid Containment Ventilation Isolation (CVI) actuation at Watts Bar Nuclear Plant (WBN) Unit 2. On July 26, 2019, at 1003 Eastern Daylight Time (EDT), the Train A CVI actuated due to an invalid High Radiation signal from 2-RM-90-130, Containment Purge Air Exhaust Monitor. Prior to and following the invalid High Radiation alarm, all radiation monitors except 2-RM-90-130 were stable at their normal values. All required automatic actuations occurred as designed. Upon investigation, the cause of the invalid High Radiation alarm was due to a failed ratemeter for 2-RM-90-130. Control room operators performed appropriate checks and confirmed that the subject indication was an invalid high radiation signal. The ratemeter for 2-RM-90-130 was replaced and the monitor returned to service. At the time of the event, plant conditions for a High Radiation alarm did not exist; therefore, the CVI was invalid. The NRC Resident Inspector was notified. |