05000454/LER-2022-001, Ob Control Room Ventilation Supply Fan Failed to Start Due to Erroneous Position Indication from the Closed Limit Switch for Charcoal Deluge Valve Interlock
| ML22252A138 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 09/09/2022 |
| From: | Welt H Constellation Energy Generation |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BYRON 2022-0060 LER 2022-001-00 | |
| Download: ML22252A138 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4542022001R00 - NRC Website | |
text
Constellation.
September 9, 2022 L TR:
BYRON 2022-0060 File:
10.101 5A.108 United States Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Byron Station, Units 1 and 2 Renewed Facility Operating License No. NPF-37 and NPF-66 NRC Docket No. STN 50-454 Constellation Energy Generation, LLC (CEG)
Byron Station 4450 N. German Church Road Byron. IL 61010-9794 www.constellationenergy.com 10CFR50.73
Subject:
Licensee Event Report (LER) No. 454-2022-001-00 "OB Control Room Ventilation Supply Fan Failed to Start due to Erroneous Position Indication from the Closed Limit Switch for Charcoal Deluge Valve Interlock" Enclosed is Byron Station Licensee Event Report (LER) No. 454-2022-001-00 regarding failure of the OB Control Room Ventilation Supply fan to start due to an erroneous position indication from the closed limit switch for the charcoal deluge valve interlock. This condition is being submitted in accordance with 10 CFR 50.73, "Licensee Event Report System."
There are no regulatory commitments in this report.
Should you have any questions concerning this submittal, please contact Ms. Zoe Cox, Regulatory Assurance Manager, at (815) 406-2800.
Respectfully,
~
Harris Welt Site Vice President Byron Generating Station HW/ZC/hh
Enclosure:
LER 454-2022-001-00 cc:
Regional Administrator-NRC Region Ill NRC Senior Resident Inspector - Byron Generating Station
NRG FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 08/31/2023 (08-2020) 1, Facility Name
- 2. Docket Number 3.Page Byron Station, Unit 1 05000454 1 OF 3
- 4. Title OB Control Room Ventilation Supply Fan Failed to Start due to Erroneous Position Indication from the Closed Limit Switch for Charcoal Deluge Valve Interlock
- 5. Event Date
- 6. LER Number
- 7. Report Date 8, Other Facilities Involved Sequential Revision Facility Name Docket Number Month Day Year Year Month Day Year Number No.
Byron Station, Unit 2 05000455 07 12 2022 2022 001 00 09 09 2022 Facility Name Docket Number NIA NIA
- 9. Operating Mode Mode 1 110. Power Level 100
)
15, Expected Submission Date NA NA NA 16, Abstract (Limit to 1560 spaces, ie., approximately 15 single-spaced typewritten lines)
On July 12, 2022, the OB Control Room Ventilation (VC)[VI] supply fan (0VC01 CB) failed to start when commanded due to an erroneous position indication from the closed limit switch (0ZS-FP432B-A) for the OB VC recirculation charcoal deluge valve (0FP432B). The deluge valve was closed but the limit switch operating lever had rolled under the limit switch finger, causing the operating lever to be in the same position as if the deluge valve were in the "intermediate" or "open" position. This resulted in the OB train of VC not being operable for 48 days. Once identified, the actuator arm and limit switch were adjusted to properly make up the closed limit and the fan was started, restoring the OB train of VC to operable.
This event is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) for any operation or condition which was prohibited by the plant's Technical Specifications.
A. Plant Operating Conditions Before the Event
Event Date:
July 12, 2022 Unit 1 - Mode 1 - Power Operations, Reactor Power 100 percent Unit 2 - Mode 1 - Power Operations, Reactor Power 100 percent Reactor Coolant System (RCS) [AB): Normal Operating Temperature and Pressure YEAR 2022 SEQUENTIAL NUMBER 001 REV NO.
00 No structures, systems or components were inoperable at the start of this event that contributed to the event
B. Description of Event
On July 12, 2022, at 03:24 CDT, the OB Control Room (VC)[VI) supply fan (0VC01 CB) failed to start when commanded due to an erroneous position indication from the closed limit switch (0ZS-FP432B-A) for the OB VC recirculation charcoal deluge valve (0FP432B). The deluge valve was in the closed position; however, the limit switch operating lever had rolled under the limit switch finger, resulting in the operating lever being in the same position as if the deluge valve was in the intermediate or open position. In accordance with the OB VC Supply Fan control logic drawing (6E-0-4030VC02), if the 0FP432B valve limit switch is in the intermediate or open position (i.e., not closed), the supply fan shunt trip coil is energized, preventing the supply fan breaker from remaining closed after a start command, causing the fan to trip immediately.
A review was completed to determine the last time the 0FP432B valve was manipulated. On May 23, 2022, the OB VC System makeup filter and recirculation charcoal adsorber were placed in service for OB VC chiller performance verification testing. This was the last documented run of 0VC01 CB supply fan prior to July 12, 2022.
On May 25, 2022, 0FP432B, recirculation charcoal deluge valve was manually cycled to support performance of a Fire Protection (FP) surveillance. On July 12, 2022, at 03:24 CDT, the attempted start of the 0VC01 CB supply fan resulted in it immediately tripping. The 0A VC train was restarted 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 13 minutes later in accordance with procedural guidance. On July 12, 2022, at 14:05 CDT, the OB VC train was started after the actuator arm and limit switch were adjusted to properly make up the closed limit interlock. On July 12, 2022, at 19:48, after completion of post-maintenance testing, Limiting Condition for Operation (LCO) Condition A for Technical Specifications 3. 7.10, "Control Room Ventilation (VC) Filtration System" and LCO Condition A for TS 3.7.11, "Control Room Ventilation (VC) Temperature Control System" were exited, and operability of the OB train of VC was restored.
C. Cause of Event
The cause of the OB VC supply fan to not start was the limit switch operating lever had rolled under the limit switch finger which made the 0FP432B valve appear to be in the intermediate or open position causing the supply fan shunt trip coil to remain energized, thereby preventing the fan breaker from remaining closed after the start command. There were inadequate margins in the length of the limit switch operating levers to be made up with the limit switch finger.
D. Safety Consequences
This condition had no actual safety consequences impacting plant or public safety. This event is not considered an event or condition that could have prevented fulfillment of a safety function.
The VC system has two full capacity, redundant equipment trains that perform the same function. The VC HVAC system is designed to ensure control of environmental conditions within specified maximum and minimum SEQUENTIAL NUMBER 001 REV NO, 00 limits which are conducive to personnel habitability and prolonged service life of Safety Category I components under all normal and abnormal station operating conditions. The 0A Train of VC remained operable during this event (i.e., between May 23, 2022 and July 12, 2022).
E. Corrective Actions
The immediate corrective action performed was to adjust the actuator arm and limit switch to properly make up the closed limit and the OB VC supply fan was started.
A work order to replace the operating levers on the OB VC recirculation charcoal deluge valves using the same part number found on the 0A VC train, which are longer in length than the lever currently installed on the OB VC train is the long-term corrective action for this event.
F.
Previous Occurrences
No previous, similar Licensee Event Reports were identified at the Byron Station in the past three years.
G. Component Failure Data
Manufacturer NAMCO Nomenclature NAMCO EL Series Operating Levers Model Series EA 170 Mfg. Part Number EL010-53338 Page_3_ of _3_