05000387/LER-2015-001

LER-2015-001, Inoperability of the 'B' Emergency Diesel Generator due to Fuel Oil Leakage

Susquehanna Steam Electric Station Unit 1
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3872015001R00 - NRC Website

LER 15-001-01 for Susquehanna, Unit 1, Regarding Condition Prohibited by Technical Specifications Due to Drift of Reactor Pressure Steam Dome - Low Switches

ML16041A418
Person / Time
Site:	Susquehanna
Issue date:	02/10/2016
From:	Franke J A Susquehanna, Talen Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
PLA-7380 LER 15-001-01
Download: ML16041A418 (8)

the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

CONDITIONS PRIOR TO THE EVENT

Unit 1 — Mode 1, 100 percent Rated Thermal Power Unit 2 — Mode 1, 100 percent Rated Thermal Power Besides the affected DG, there were no systems, structures, or components that were inoperable at the start of the event and contributed to the event.

EVENT DESCRIPTION

During a routine surveillance test run on March 2, 2015, the 'B' Emergency Diesel Generator (DG) [EIIS System Identifier: EK] was declared inoperable due to fuel oil leakage from the fuel oil drain line crossover piping [EIIS System/Component Identifier: DC/PSP].

The DG was declared inoperable because it was not known if the DG would have been able to meet its mission time due to the risk of fire from the leaking fuel oil. The leaking drain line piping was replaced and the 'B' DG was restored to operable on March 3, 2015.

On January 31, 2015, fuel oil drain line pipe fretting and fuel oil leakage was identified on the 'B' DG at a leak rate of approximately 12 drops per minute. A prompt operability determination (POD) was performed that concluded that there was no impact on the ability of the DG to perform its safety function with the existing leak. The DG was later declared inoperable on March 2, 2015 when the leak rate increased to approximately 24 drops per minute with some spraying action observed. Based on the initial identification of leakage on January 31, 2015, firm evidence is considered to exist to indicate that the condition existed prior to the time of discovery. Therefore, this condition is considered to be reportable under 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specification 3.8.1.

CAUSE OF THE EVENT

The direct cause of the fuel oil leakage was determined to be fretting, due to normal engine vibration, from the fuel oil drain line crossover piping rubbing against a metal clamp used to support the piping. The underlying cause of the fretting was determined to be an inadequate design of the support clamp. The design did not take into account the engine vibration and the possibility of fretting-induced wear from metal-on-metal contact. Additional cause evaluation is in progress and a supplemental LER will be submitted based on the additional cause analysis, if necessary.

ANALYSIS/SAFETY SIGNIFICANCE

Given the location of the affected drain line piping and the design of the fuel oil system, the fuel oil leakage did not adversely impact the supply of fuel oil to the DG to perform its safety function for the required mission time. The DG was declared inoperable based on the condition not being bounded by the POD with respect to the risk of fire from the leaking fuel oil and the resulting potential impact of a fire on the DG's ability to meet its required mission time.

There were no actual consequences to the health and safety of the public as a result of this event.

CORRECTIVE ACTIONS

Immediate corrective action was taken to shut down the DG from its surveillance test, replace the affected piping, and complete the routine surveillance test run on the 'B' DG. The support clamp was then replaced with a clamp of a different design to account for engine vibration and fretting-induced wear. The extent of condition was evaluated and affected piping was replaced and clamps of a different design were installed on the 'A', `C', and 'D' DGs.

PREVIOUS SIMILAR EVENTS

Although no fuel oil leakage was identified, fretting at this piping location was previously addressed in 2001 by replacing the affected piping.