05000387/LER-2021-002, Inoperability of Computer Room Floor Cooling Fan Caused by Extended Operation with Worn Belts Due to Less than Adequate Preventive Maintenance Replacement Interval
| ML21179A288 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 06/28/2021 |
| From: | Cimorelli K Susquehanna, Talen Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| PLA-7956 LER 2021-002-00 | |
| Download: ML21179A288 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 3872021002R00 - NRC Website | |
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June 28, 2021 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)/2021-002-00 UNIT 1 LICENSE NO. NPF-14 UNIT 2 LICENSE NO. NPF -22 PLA-7956 TALEN~.
ENERGY 10 CFR 50.73 Docl{et No. 50-387 50-388 Attached is Licensee Event Report (LER) 50-387(388)/2021-002-00 that reports an event involving inoperability of the Division II Computer Room Floor Cooling Fan. This event was determined to be reportable as a condition prohibited by Technical Specifications in accordance with 10 CFR 50.73(a)(2)(i)(B) and a condition that could have prevented fulfillment of a safety function in accordance with 10 CFR 50.73(a)(2)(v)(D).
There were no actual consequences to the health and safety of the public as a result of this event.
r revised regulatory commitments.
Attachment: LER 50-387(388)/2021-002-00 Copy:
NRC Region I Ms. A. Klett, NRC Project Manager Mr. C. Highley, NRC Senior Resident Inspector Mr. M. Shields, PA DEP/BRP
Abstract
On May 4, 2021 at 11:00, Technical Specification (TS) 3.7.3, Control Room Emergency Outside Air Supply (CREOAS)
System and TS 3.7.4, Control Room Floor Cooling System were entered for Units 1 and 2 to support the investigation of elevated vibration associated with the Division II Computer Room Floor Cooling Fan (0V115B) identified on April 29, 2021. During the May 4, 2021 investigation, 0V115B was found with two of the five belts thrown (disengaged from the sheaves) and one belt beginning to loosen. In the as-found condition, mission time requirements for the Division II systems could not be justified.
Concurrent with the elevated vibrations on Division II, the associated Division I systems were inoperable due to trip of the Division I Control Structure (CS) Chiller. Since the vibration is considered to have been the result of the degraded belts, both ventilation trains were concurrently inoperable from April 29, 2021 to April 30, 2021, when the Division I CS Chiller was returned to service. Based on information available, the concurrent inoperability is considered to have existed for longer than allowed by TS 3.0.3 and is reportable as a condition prohibited by TS (10 CFR 50.73(a)(2)(i)(B))
and a condition that could have prohibited the fulfillment of a safety function (10 CFR 50.73(a)(2)(v)(D)).
The cause was determined to be extended operation with worn belts due to less than adequate preventive maintenance (PM) replacement interval. Key corrective actions include replacing the belts and revising the PM frequency from eight years to six years.
There were no actual consequences to the health and safety of the public as a result of this event.
CONDITIONS PRIOR TO EVENT
Unit 1 - Mode 1, approximately 100 percent Rated Thermal Power Unit 2 - Mode 1, approximately 90 percent Rated Thermal Power The Division I Control Structure (CS) Chiller [EIIS System/Component Identifier: VI/CHU] was inoperable when the vibration in the Division II Computer Room Floor Cooling Fan (0V115B) [EIIS System/Component Identifier: VI/FAN] was identified.
EVENT DESCRIPTION
On May 4, 2021 at 11:00, Technical Specification (TS) 3.7.3, Control Room Emergency Outside Air Supply (CREOAS) System and TS 3.7.4, Control Room Floor Cooling System were entered for Units 1 and 2 to support the investigation of elevated vibration associated with the Division II Computer Room Floor Cooling Fan (0V115B) which was identified on April 29, 2021. During the May 4, 2021 investigation, 0V115B was found with two of the five belts thrown (disengaged from the sheaves) and one belt beginning to loosen. In the as-found condition, mission time requirements for the Division II systems could not be justified.
Concurrent with the elevated vibrations on Division II, the associated Division I systems were inoperable due to trip of the Division I CS Chiller. Since the vibration is considered to have been the result of the degraded belts, both ventilation trains were concurrently inoperable from April 29, 2021 to April 30, 2021, when the Division I CS Chiller was returned to service. Based on information available, the concurrent inoperability is considered to have existed for longer than allowed by TS 3.0.3 and is reportable as a condition prohibited by TS (10 CFR 50.73(a)(2)(i)(B)) and a condition that could have prevented the fulfillment of a safety function (10 CFR 50.73(a)(2)(v)(D)).
A detailed timeline of events is as follows:
4/28/2021 at approximately 12:14 - The Division I Control Structure Chiller tripped, and TS 3.7.3 and TS 3.7.4 were entered.
4/29/2021 at approximately 13:00 - Maintenance personnel performing routine predictive maintenance activities, identified that vibrations on the Division II Computer Room Fan were elevated. An immediate operability determination was performed that determined that the fan was operable, and a prompt operability determination was initiated.
4/30/2021 at approximately 20:35 - Division I components were declared operable and TS 3.7.3 and TS 3.7.4 were exited. Division I systems were subsequently placed in lead and Division II were placed in standby.
5/4/2021 at approximately 11:00 - Operations entered TS 3.7.3 and TS 3.7.4 to support investigation of the Division II Computer Room fan elevated vibrations. The fan plenum was inspected identifying two of the five belts thrown (disengaged from the sheaves) and one belt beginning to loosen. Belt replacement was initiated.
5/4/2021 at approximately 14:15 - Repairs were completed.
5/4/2021 at approximately 16:01 - Division II was declared operable and TS 3.7.3 and TS 3.7.4 were exited.
CAUSE OF EVENT
The direct cause of the Computer Room Floor Cooling Fan (0V115B) throwing its belts was extended operation with worn belts. This worn belt condition was due to less than adequate Preventive Maintenance (PM) replacement interval of the belts.
ANALYSIS/SAFETY SIGNIFICANCE
Evaluation determined that, although mission time requirements could not be justified, the fan was determined to have been performing its safety function during the time when both trains were considered inoperable. As a result, there was no actual loss of safety function. Based on this evaluation, this event will not be counted as a safety system functional failure for the NRC Reactor Oversight Process performance indicator.
CORRECTIVE ACTIONS
Key corrective actions include the following:
- 1. Replaced the belts with new belts.
- 2. Revise the PM frequency from eight years to six years.
COMPONENT FAILURE INFORMATION
Computer Room Floor Cooling Fan B (0V115B):
Manufacturer: Carrier Corporation Model No: 39ED75
PREVIOUS SIMILAR EVENTS
LER 50-387(388)/2019-001-01, Loss of Both Control Structure Chillers due to Misaligned Breaker Stab, dated December 11, 2019 LER 50-388(387)/2015-015-00, Loss of Safety Function due to Inoperability of Both Trains of the Control Room Emergency Outside Air Supply (CREOAS) System, dated May 5, 2016 LER 50-387(388)/2014-009-00, Loss of Both Trains of Control Structure Chilled Water during Application of Clearance Order, dated August 11, 2014 LER 50-387(388)/2014-008-00, Loss of Both Trains of Control Structure Chilled Water due to Personnel Error, dated August 11, 2014