ENS 53777
ENS Event | |
|---|---|
05:00 Oct 9, 2018 | |
| Title | 60-Day Optional Telephonic Notification of Invalid Specified System Actuation |
| Event Description | This 60-day telephone notification is being made in accordance with 10 CFR 50.73(a)(1) and 10 CFR 50.73(a)(2)(iv)(A) to provide information pertaining to an invalid Engineered Safety Feature actuation signal.
On October 9, 2018, Arkansas Nuclear One, Unit 2 was in refueling Mode 6, when a vital inverter failed while aligned from its alternate power source causing a loss of one of four vital instrument buses. The loss of the instrument bus resulted in one of the four engineered safety feature protection channels to enter a tripped state. Because one of the other four channels was already in a tripped state in support of a channel power supply replacement activity, two out of four protection channels were now in the tripped state resulting in a Safety Injection Actuation Signal, Containment Spray Actuation Signal, Containment Cooling Actuation Signal, Recirculation Actuation Signal, Emergency Feed Actuation Signal, and Containment Isolation Actuation Signal. In general, only one train of equipment is protected and assumed to be available during Mode 6 operations. Due to the defense-in-depth plant configuration in Mode 6, which is intended to avoid inadvertent start of emergency systems, the resulting actuations caused no adverse impact to Shutdown Cooling or Spent Fuel Pool cooling operations. At least one train of the following systems was aligned for automatic actuation: Containment Penetration Room Exhaust Fan Other non-essential components which are shed or realigned upon safeguards actuation The few systems and components that were aligned for automatic operation responded as designed, including containment isolation valves and valves associated with the above systems (if aligned for automatic operation). The Service Water system was already in operation and, therefore, no Service Water pumps actuated. All systems and components which were capable of automatic operation performed as designed. The Emergency Diesel Generator started but did not synchronize to the bus. No safety injection occurred to the core. This actuation was caused by equipment failure and was not an actual signal resulting from parameter inputs. The affected actuation signals do not perform a safety function in Mode 6 and are not required to be available or operable. Therefore, this actuation is considered invalid. This event was entered into ANO's corrective action program for resolution. This event did not result in any adverse impact to the health and safety of the public. In accordance with 10 CFR 50.73(a)(i) a telephone notification is being made in lieu of submitting a written Licensee Event Report. The licensee has notified the NRC Resident Inspector." |
| Where | |
|---|---|
Arkansas Nuclear  Arkansas (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+1376.9 h57.371 days <br />8.196 weeks <br />1.886 months <br />) | |
| Opened: | Benjamin Egnew 14:54 Dec 5, 2018 |
| NRC Officer: | Jeffrey Whited |
| Last Updated: | Dec 5, 2018 |
| 53777 - NRC Website | |
WEEKMONTHYEARENS 541472019-05-09T17:05:0009 May 2019 17:05:00
[Table view]10 CFR 50.73(a)(1), Submit an LER 60-Day Telephonic Notification of Invalid Engineered Safety Feature Actuation Signal ENS 537772018-10-09T05:00:0009 October 2018 05:00:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Telephonic Notification of Invalid Specified System Actuation ENS 422372005-12-31T20:12:00031 December 2005 20:12:00 10 CFR 50.73(a)(1), Submit an LER Automatic Actuation of the Emergency Feedwater (Efw) Due to a Transient on the "B" Main Feedwater (Mfw) Pump 2019-05-09T17:05:00 | |