05000387/LER-2021-001, Electri Station, Unplanned Lnoperability of the High Pressure Coolant Injection (HPCI) System Due to a Primary Containment Isolation (PCIV) Valve Failure to Stroke Full Closed On-demand Due to an Intermittent Break
| ML21126A316 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 05/06/2021 |
| From: | Cimorelli K Susquehanna, Talen Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| PLA-7939 LER 2021-001-00 | |
| Download: ML21126A316 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 3872021001R00 - NRC Website | |
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May 6, 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 /2021-001-00 UNIT 1 LICENSE NO. NPF-14 PLA-7939 TALEN~
ENERGY 10 CFR 50.73 Docket No. 50-387 Attached is Licensee Event Report (LER) 50-3 87/2021-001-00. The LER reports an event involving the inoperability of the High Pressure Coolant Injection System (HPCI) due to the HPCI Turbine Exhaust Inboard Vacuum Breaker Valve failing to stroke fully closed on demand.
The condition is being reported in accordance with 10 CFR 50.73(a)(2)(v) as an event or condition that could have prevented fulfillment of a safety function.
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 50-387/2021-001-00 Copy:
NRC Region I Mr. C. Highley, NRC Senior Resident Inspector Ms. S. Goetz, NRC Project Manager Mr. M. Shields, PA DEP/BRP
Abstract
On March 9, 2021 at approximately 03:13, during performance of quarterly Unit 1 High Pressure Coolant Injection System (HPCI) valve exercising, dual indication was received in the control room for the HPCI Turbine Exhaust Vacuum Breaker inboard isolation valve (HV155F079) due to the valve failing to stroke fully closed on demand. Upon discovery of the condition, Operations entered Unit 1 Technical Specification (TS) 3.6.1.3, Condition A for one or more penetration flow paths with one Primary Containment Isolation Valves (PCIV) inoperable. The HPCI Turbine Exhaust Vacuum Breaker inboard isolation valve was then closed, resulting in unplanned inoperability of HPCI. At the time the condition was identified, Unit 1 was already in TS 3.5.1, Condition D, HPCI system inoperable, due to the planned surveillance testing.
This event was reported by Event Notification 55128 in accordance with 10 CFR 50.72(b)(3)(v)(D). The condition is also being reported in accordance with 10 CFR 50.73(a)(2)(v) as an event or condition that could have prevented fulfillment of a safety function. The cause of the event was an intermittent break in the valve's close control circuitry likely due to dirty contacts on HPCI Turbine Exhaust Vacuum Breaker inboard isolation valve hand switch. Key corrective actions include planned replacement of hand switch (HS15579). There were no actual consequences to the health and safety of the public as a result of this event.
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 08/31/2023
- 3. LERNUMBER Susquehanna Steam Electric Station, Unit 1
NARRATIVE
05000-387
CONDITIONS PRIOR TO EVENT
Unit 1 - Mode 1, approximately 100 percent Rated Thermal Power Unit 2 - Mode 1, approximately 75 percent Rated Thermal Power YEAR 2021 SEQUENTIAL NUMBER 001 There were no structures, systems, or components that were inoperable at the start of the event that contributed to the event.
EVENT DESCRIPTION
REV NO.
00 On March 9, 2021 at approximately 03:13, during performance of quarterly High Pressure Coolant Injection System (HPCI) [EIIS System Code: BJ] valve exercising, dual indication was received in the control room for the HPCI Turbine Exhaust Vacuum Breaker inboard isolation valve (HV155F079) [EIIS Component Code:
VACB] due to the valve failing to stroke fully closed on demand. Upon discovery of the condition, Operations entered Unit 1 Technical Specification (TS) 3.6.1.3, Condition A for one or more penetration flow paths with one Primary Containment Isolation Valve (PCIV) inoperable. The HPCI Turbine Exhaust Vacuum Breaker inboard isolation valve was then closed, resulting in unplanned inoperability of HPCI. At the time the condition was identified, Unit 1 was already in TS 3.5.1, Condition D, HPCI system inoperable, due to the planned surveillance testing. After the initial failure, operations personnel were dispatched to the valve and no issues were observed. The valve was successfully stroked open and closed within acceptance times. In addition, maintenance investigations observed and monitored the valve and valve closure circuitry during multiple subsequent valve strokes and no issues were noted. TS 3.6.1.3, Condition A was exited on March 10, 2021 at approximately 18:13 and TS 3.5.1 was exited on March 10, 2021 at approximately 18:59.
This event was reported by Event Notification 55128 in accordance with 10 CFR 50.72(b)(3)(v)(D). The condition is also being reported in accordance with 10 CFR 50. 73(a)(2)(v) as an event or condition that could have prevented fulfillment of a safety function.
CAUSE OF EVENT
The direct cause of the event was an intermittent break in the valve's close control circuitry likely due to dirty contacts on HPCI Turbine Exhaust Vacuum Breaker inboard isolation valve hand switch (HS15579).
05000-387
ANALYSIS/SAFETY SIGNIFICANCE
YEAR 2021 SEQUENTIAL NUMBER 001 REV NO.
00 An engineering evaluation was completed to analyze the HPCI Turbine Exhaust Vacuum Breaker valve's failure to stroke closed. The turbine exhaust header is equipped with a three-inch tap that forms the turbine exhaust vent header. The vent header contains two primary containment isolation valves HV155F079 (inboard) and HV155F075 (outboard). The open function of these valves supports HPCI operation and is not of concern since the valve successfully stroked open. The closure function of the valves supports primary containment isolation. Closure of any one valve is sufficient to achieve containment isolation. Review of the completed valve exercising surveillance determined valve HV155F075 (outboard) did successfully stroke closed and therefore would have performed the containment isolation function. With the containment isolation function successfully performed, the condition did not represent a safety system functional failure and all design requirements associated with the penetration continued to be met. Accordingly, this event will not be counted as a safety system functional failure in the Reactor Oversight Process Performance Indicators.
There were no actual consequences to the health and safety of the public as a result of this event.
CORRECTIVE ACTIONS
Key corrective actions include planned replacement of the HPCI Turbine Exhaust Vacuum Breaker inboard isolation valve hand switch (HS15579).
COMPONENT FAILURE INFORMATION
Component Identification - HV155F079 Component Name - HPCI Turbine Exhaust Inboard Vacuum Breaker Valve Valve Manufacturer - Anchor Darling Valve Type - 3" Flex Wedge Gate Valve Actuator Manufacturer - Limitorque Corporation Actuator Size - SMB-000
PREVIOUS OCCURRENCES
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