05000366/LER-2013-003
| Edwin 1. Hatch Nuclear Plant Unit 2 | |
| Event date: | 03-18-2013 |
|---|---|
| Report date: | 06-14-2013 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident |
| 3662013003R01 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
General Electric - Boiling Water Reactor Energy Industry Identification System codes appear in the text as (EIIS Code XX).
DESCRIPTION OF EVENT
On March 18, 2013 at approximately 0910 EDT, during startup from the 2R22 refueling outage, the Unit 2 HPCI system was declared inoperable when the TCV did not open as expected during the HPCI pump operability surveillance test performed at less than 165 psig. The HPCI (BJ) system had major maintenance performed during the refueling outage and was returned to an operable status based on completion of the maintenance activities and successful surveillances performed within the system prior to reactor vessel pressurization. Technical Specification (TS) 3.0.5 allows equipment removed from service to comply with actions to be returned to service under administrative controls.
The restriction in TS 3.0.5 states that the equipment can be operated only to demonstrate its operability, or the operability of other equipment. The final functional test surveillances for HPCI operability must occur at known reactor pressures. The first of these surveillances occurs when reactor pressure is less than 165 psig. The second surveillance is performed when reactor pressure is adequate to perform the surveillance test to demonstrate that the required flow can be achieved with reactor pressure between 920 psig and 1058 psig. HPCI is required to be operable when reactor pressure is greater than 150 psig in Mode 2 by Technical Specification 3.5.1. The crew is allowed to assume HPCI operability based on preliminary surveillances so that the plant can move from Mode 4 (Cold Shutdown) to Mode 2 (Startup/Hot Standby).
On the morning of March 18, 2013 the crew logged an entry for the HPCI Pump Operability 165 PSIG Test at 0803 EDT, At 0910 EDT, the crew entered a Required Action Statement for Technical Specification 3.5.1.0 because the system operators indicated that the HPCI Turbine Control Valve did not open as expected when performing the HPCI Pump Operability 165 psig Test. A surveillance test for Reactor Core Isolation Cooling (RCIC) System Operability had been performed at 0600 EDT that morning, at which time RCIC was proven operable. The crew began reducing pressure in the reactor vessel to less than 150 psig, and formed an Incident Response Team (IRT) to identify the cause(s) of the HPCI failure and to effect repairs as needed. The hydraulic lines to the hydraulic actuator and remote servo were found to have been inadvertently interchanged when reassembly of the hydraulic connections occurred during the maintenance performed on the HPCI system during the outage. The lines were properly reconnected, and the HPCI system returned to Operations at approximately 1033 EDT on 3/19/2013. The HPCI operability surveillance was successfully performed at approximately 1056 EDT on 3/19/2013.
CAUSE OF EVENT
The cause determination found that the hydraulic tubing between two ports on the hydraulic actuator and the remote servo had been interchanged. The resulting inability to remove the pressure at the affected port was determined to be the direct cause for the Turbine Control Valve (TCV) failure to open. The hydraulic actuator and remote servo had been replaced during the 2R22 refueling outage by vendors in February, 2013. The vendor workers performing the evolution had marked the tubing prior to removal with permanent marker, but the markings rubbed off and became illegible. The workers mistakenly believed that all the tubing was the same, so they tried to overcome their loss of markings by ensuring that the tubing was placed between the corresponding ports on the hydraulic actuator and remote servo. What they neglected to observe is that one line contained a check valve and this line was specific to the "E" ports. The "E" line was inadvertently interchanged with another line lacking a check valve. This lack of self-checking led to the failure of the TCV to open. The preventive maintenance (PM) procedure was a contributing cause as it lacked a diagram or details on how to reassemble the hydraulic actuator and its tubing, The PM procedure also did not discuss the presence of the check valve in one of the lines.
REPORTABILITY ANALYSIS And SAFETY ASSESSMENT The HPCI system was inoperable less than 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> which was well within the 14 Day completion time allowed in Technical Specifications 3.5.1, Required Action C.2, making this a condition allowed by the Technical Specifications. However, this event is reportable as required by 1OCFR50.73(a)(2)(v)(D) since the HPCI system failed to meet the Technical Specification surveillance requirements, which represents a condition that could have prevented the fulfillment of HPCI to perform its safety function While Technical Specifications allows HPCI to be inoperable with a completion time of 14 days, HPCI is a single-train high pressure injection system and any failure of the HPCI system could prevent the fulfillment of its safety function to mitigate the consequences of an accident. This failure of HPCI was discovered when the plant was returning to power from a refueling outage. The failure was discovered during a required Technical Specification surveillance test that was required for continued HPCI operability above 165 psig. The response to the failure was to reduce reactor pressure to less than 150 psig until the cause could be determined and the HPCI system repaired. The other high pressure core coolant injection system, RCIC was also confirmed to be operable at the time of the HPCI actuator failure. The residual heat removal (RHR) and Core Spray systems that are relied upon to mitigate the consequences of a design basis accident (DBA) were fully operable during this evolution which provided full capacity to mitigate the consequences of a DBA during the time that HPCI was considered inoperable. Given these conditions, this failure of the HPCI actuator was considered to have low safety significance.
CORRECTIVE ACTIONS
The lines were properly reconnected, and the HPCI system returned to Operations at approximately 1033 EDT on 3/19/2013. The HPCI operability surveillance was successfully performed at approximately 1056 EDT on 3/19/2013. Additionally, PM Procedure 52PM-E41-002-0 (HPCI Turbine and Auxiliaries Major Inspection) was revised to include detailed instructions on the labeling of the hydraulic actuator and remote servo piping prior to removal and to include additional post- maintenance testing criteria for the hydraulic actuator and remote servo.
ADDITIONAL INFORMATION
Other Systems Affected: None Failed Components Information:
Master Parts List Number:
Manufacturer: Woodward Model Number: DR9903-099 Type: E-GR Hydraulic Actuator Manufacturer Code: W290 2E41C002-5* EIIS System Code: BJ Reportable to Epix: Yes Root Cause Code: D EIIS Component Code: XCO *The Turbine Control Valve failed to open due to inappropriate replacement of the hydraulic tubing to