05000387/LER-2022-003, Inoperable 13.8kV Startup Transformer Due to Misaligned Load Tap Charger Local/Remote Control Switch
| ML22353A082 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 12/19/2022 |
| From: | Cimorelli K Susquehanna, Talen Energy |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| PLA-8034 LER 2022-003-00 | |
| Download: ML22353A082 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3872022003R00 - NRC Website | |
text
December 19, 2022 Kevin Cimorelli Site Vice President Attn: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Susquehanna Nuclear, LLC 769 Salem Boulevard Berwick, PA 18603 Tel. 570.542.3795 Fax 570.542.1504 Kevin.Cimorelli@TalenEnergy.com SUSQUEHANNA STEAM ELECTRIC STATION LICENSEE EVENT REPORT 50-387(388)/2022-003-00 UNIT 1 LICENSE NO. NPF-14 UNIT 2 LICENSE NO. NPF-22 PLA-8034 TALEN~
ENERGY 10 CFR 50.73 Docket No. 50-387 And 50-388 Attached is Licensee Event Report (LER) 50-387(388)/2022-003-00. The LER reports an event in which one 13.8kV startup transformer was inoperable for longer than allowed by Technical Specifications (TS). This condition is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by TS.
There were no actual consequences to the health and safety of the public as a result of this event.
This letter contains no new or revised regulatory commitments.
~
K. Cimorelli Attachment: LER 50-387(388)/2022-003-00 Copy:
NRC Region I Mr. C. Highley, NRC Senior Resident Inspector Ms. A. Klett, NRC Project Manager Mr. M. Shields, PA DEP/BRP
Abstract
On October 22, 2022, operators at the Susquehanna Steam Electric Station identified the load tap changer (LTC) local/remote control switch on one of the two 13.8 kV startup transformers was in the remote position, as opposed to the required local position. Upon identification of the condition, operators entered Technical Specification (TS) 3.8.1, AC Sources-Operating, Condition A for one offsite circuit inoperable. The switch was restored to the local position and the transformer was declared operable at 21:00 on October 22, 2022.
Based on investigation and cause, the condition is likely to have existed since October 12, 2022, and is, therefore, being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by TS.
The cause of the event was determined to be inadvertent bumping of the LTC local/remote control switch during opening and closing of the transformer cabinet doors by maintenance personnel. This cause was attributed to a human performance error. Corrective actions include planned procedure revisions to verify the LTC control switches are properly positioned during transformer restoration. There were no actual consequences to the health and safety of the public as a result of this event.
<)P~ REc11~
/~ {Ko~
_2l_
i
~~~-Ir', ;
~,.,-:;-*'71 +01
- it-*~*
I I
I I
I I
I I
I I
I I
I I
I I
I I
I I
I I
I I
I I
I
CONDITIONS PRIOR TO EVENT
Unit 1 - Mode 1, approximately 85 percent Rated Thermal Power (RTP)
Unit 2 - Mode 1, approximately 100 percent RTP There were no structures, systems, or components that were inoperable at the start of the event and contributed to the event. One of the two 13.8kV startup transformers was inoperable for planned maintenance.
EVENT DESCRIPTION
On October 22, 2022, operators at the Susquehanna Steam Electric Station identified the load tap changer (LTC) local/remote control switch [EIIS Component Code: 33] on one of the two 13.8kV startup transformers [EIIS System/Component Code: E/XFMR] was in the remote position, as opposed to the required local position. Upon identification of the condition, operators entered Technical Specification (TS) 3.8.1, AC Sources-Operating, Condition A for one offsite circuit inoperable. Investigation determined the control switch was most likely inadvertently manipulated while restoring the transformer to operable from planned maintenance on October 12, 2022. The switch was restored to the local position and the transformer was declared operable at 21:00 on October 22, 2022.
The following timeline demonstrates the sequence of events:
10/10/2022 ~ 22:10: TS 3.8.1, Condition A is entered to support planned maintenance on one of the two 13.8 kV startup transformers.
10/11/2022 ~ 06:00: Routine preventative maintenance activities begin to inspect and change the oil in the transformer LTC. The LTC local/remote control switch is not manipulated per the work instructions.
10/11/2022 ~ 14:00: While removing the clearance order from the 480 V normal and alternate control cabinet [EIIS Component Code: CAB], the transformer cooling fans [EIIS Component Code: FAN] started unexpectedly, requiring troubleshooting to restore the transformer to operable.
10/11/2022 ~ 18:15: Maintenance of the LTC is completed and post maintenance testing (PMT) is completed successfully.
10/11/2022 through 10/12/2022 ~20:00: Troubleshooting on the unexpected fan start continued.
Troubleshooting activities require access in the cabinet where the LTC local/remote control switch is located.
Investigation determined this to be the most probable timeframe the switch was inadvertently bumped.
10/12/2022 ~ 20:00: The transformer is restored to service and declared Operable. TS 3.8.1, Condition A is exited.
10/22/2022 ~ 15:13: The control room received a report that the transformer LTC local/remote control switch was found in the remote position, as opposed to the expected local position. The transformer is declared inoperable and TS 3.8.1, Condition A is entered.
10/22/2022 ~ 21:00: The LTC local/remote control switch is placed in the correct position and the transformer is declared operable. TS 3.8.1, Condition A is exited.
Based on the timeline above, the transformer was inoperable for longer than allowed by TS. Therefore, this condition is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by TS.
CAUSE OF EVENT
The cause of the event was determined to be inadvertent bumping of the LTC local/remote control switch during opening and closing of the transformer cabinet doors by maintenance personnel. This cause was attributed to a human performance error.
ANALYSIS/SAFETY SIGNIFICANCE
Based on engineering analysis of the event, station AC sources could have performed their safety function for this condition. If the startup transformer were unable to provide power, the alternate startup transformer is capable of providing offsite AC power to systems and components required to operate the engineering safety features for one unit and safe shutdown loads on the other unit. In addition, if both offsite sources were unavailable, the four aligned Emergency Diesel Generators (DGs) would supply the required power to emergency loads. Both the alternate startup transformer and the DGs were available during the time the LTC was in the remote position. Therefore, the electrical distribution system could have fulfilled its safety function for the condition described.
This event will not be counted as a safety system functional failure for the NRC performance indicator based on the engineering analysis supporting the systems ability to fulfill the safety function. There were no actual consequences to the health and safety of the public as a result of this event.
CORRECTIVE ACTIONS
1.
Share lessons learned with station maintenance personnel.
2.
Revise station operation procedures to verify the LTC control switches are in proper positions for operability during transformer restoration.
COMPONENT FAILURE INFORMATION
Not applicable.
PREVIOUS OCCURRENCES
None.