05000388/LER-2015-007

LER-2015-007, 1 of 3

Susquehanna Steam Electric Station, Unit 2
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3882015007R00 - NRC Website

CONDITIONS PRIOR TO EVENT

Unit 1 — Mode 1, 97.5 percent Rated Thermal Power Unit 2 — Mode 1, 100 percent Rated Thermal Power There were no structures, systems, or components that were inoperable at the start of the event that contributed to the event.

EVENT DESCRIPTION

On September 30, 2015, the Unit 2 Reactor Water Sample Outboard (0B) Isolation Valve (HV243F020) [El IS System Identifier: AD, Component Function Identifier: ISV] failed In-service Testing (IST) stroke time surveillance testing. The close stroke was timed at 3.85 seconds (the acceptance criteria requires closure in less than or equal to 2 seconds). This required entry into Limiting Condition for Operation (LCO) 3.6.1.3 Condition A.

Following the September 30, 2015 stroke time failure, the associated solenoid valve, SV24320, was replaced. The defective solenoid was returned to engineering for disassembly and inspection. Inspection results confirmed that the previously installed solenoid was sticky/sluggish in changing plunger state.

HV243F020 had failed stroke time testing during the previous quarterly test on July 1, 2015. Investigative valve strokes were performed and timed to be within 1ST stroke time acceptance criteria following the failure. The limit switch was lubricated and a successful surveillance test was performed. A subsequent Failure Modes Analysis was performed and identified solenoid valve sticking as a probable cause, and limit switch sticking as an unlikely cause.

The direct cause of the second failure was sticking/sluggishness of Solenoid Valve SV24320 resulting in excessive closed stroke time. One of the apparent causes for second failure included less than adequate corrective action following the July 1, 2015 failure.

Based on the history and cause, Susquehanna concluded that firm evidence existed that the condition existed prior to discovery on September 30, 2015 for a period longer than allowed by Technical Specifications. As a result, this condition is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications.

CAUSE OF EVENT

The direct cause was sticking/sluggishness of Solenoid SV24320 resulting in excessive closed stroke time.

The apparent causes were as follows:

1. Less than adequate corrective action following HV243F020 stroke time failure on July 1, 2015.

2. Less than adequate Preventive Maintenance (PM) strategy for HV243F020/SV24320

ANALYSIS/SAFETY SIGNIFICANCE

The actual consequence of this event was HV243F020 being declared inoperable, which involved isolating the affected penetration flow path as required by LCO 3.6.1.3 Condition A within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The stroke time failure also resulted in a Maintenance Preventable Functional Failure (MPFF).

Potential consequence of this event would be complete failure of HV243F020 to close, and concurrent failure of the Unit 2 Reactor Water Sample Inboard Isolation Valve, HV243F019. This would also require isolation of the penetration within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> (rather than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />) and, if unable to isolate the penetration, entry into MODE 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

CORRECTIVE ACTIONS

1. The faulty solenoid valve was replaced.

2. The HV243F020 actuator overhaul preventive maintenance scope will be revised to include solenoid valve replacement.

COMPONENT FAILURE INFORMATION

Component Identification — HV243F020 Component Name — Unit 2 Reactor Water Sample OB Isolation Valve Valve Manufacturer — Masoneilan Valve Type — Globe Valve Size — 1 inch Actuator Manufacturer — Masoneilan Actuator Model/Size — Model 38, Size 9

PREVIOUS SIMILAR EVENTS

The following are similar Susquehanna events that have occurred within the past five years:

CR-1733145 - On August 5, 2013, HV243F019 (Reactor Water Sample Inboard Isolation Valve) failed close stroke time. The cause was identified as solenoid exhaust port blockage combined with potential for solenoid valve internal sticking.

CR-2014-26599 - On August 21, 2014, HV143F019 (Reactor Water Sample Inboard Isolation Valve) failed surveillance testing. The caused was determined to be solenoid valve vent blockage and sticking.