05000293/LER-2016-001

LER-2016-001, Both Emergency Diesel Generators Inoperable

Pilgrim Nuclear Power Station
Event date:	04-12-2016
Report date:	06-09-2016
Reporting criterion:	10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor
2932016001R00 - NRC Website

LER 16-001-00 for Pilgrim Nuclear Power Station Regarding Both Emergency Diesel Generators Inoperable

ML16168A030
Person / Time
Site:	Pilgrim
Issue date:	06/09/2016
From:	Perkins E P Entergy Nuclear Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
2.16.030 LER 16-001-00
Download: ML16168A030 (7)

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to 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.

Pilgrim Nuclear Power Station 05000293

BACKGROUND

The standby alternating current (AC) power source provides two independent diesel generators as the onsite source of AC power to the emergency service portions of the station Auxiliary Power Distribution System.

Each onsite source provides AC power to safely shut down the reactor, maintain the safe shutdown condition, and operate all auxiliaries necessary for station safety.

On April 10, 2016 at 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br />, Emergency Diesel Generator (EDG) B was tagged out of service for planned preventative maintenance.

EVENT DESCRIPTION

At approximately 2130 hours0.0247 days <br />0.592 hours <br />0.00352 weeks <br />8.10465e-4 months <br /> on April 11, 2016, as part of the Operators outside tour of the EDG building, the Operator on tour reported a water leak from the C103C panel trailing across the EDG A floor towards the floor drain. This leak was evaluated and determined to be a leak in the EDG A Cooling Water System (EIIS code = LB) pressure boundary. The leak rate was determined to be approximately 130 drops per minute (dpm). At 0050 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> on April 12, 2016, EDG A was declared inoperable due to the jacket water pressure boundary leak.

PNPS entered an unplanned 24-hour LCO Action Statement per Technical Specification 3.5.F.1 because both EDGs were Inoperable.

The pipe fitting was replaced and EDG A was restored to operable status at 1059 hours0.0123 days <br />0.294 hours <br />0.00175 weeks <br />4.029495e-4 months <br /> on April 12, 2016.

CAUSE OF THE EVENT

The apparent cause of the EDG A jacket water pressure boundary leak was identified to be stress corrosion cracking (SCC) of the bulkhead pipe fitting. The pipe fitting was original plant equipment manufactured by Imperial—Eastman Corp (EIIS code = 1027), and was identified on plant drawings as Part #1298 Anchor Coupling (EIIS Code = PSF).

CORRECTIVE ACTIONS

The leaking anchor coupling bulkhead fitting on EDG A was replaced to restore EDG A operability.

Additional corrective actions were issued to mitigate the likelihood of event recurrence. These additional actions include: Procedure enhancement to inspect the opposite train EDG cabinets prior to performing scheduled maintenance on either EDG; and action to replace both EDG A and B anchor coupling pipe fittings associated with the jacket water pressure instruments with new fittings.

lessons learned are indorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to Regulatory Affairs, 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.

Pilgrim Nuclear Power Station 05000293

SAFETY CONSEQUENCES

The standby AC power source provides two independent diesel generators as the onsite source of AC power to the emergency service portions of the station Auxiliary Power Distribution System. Each onsite source provides AC power to safely shut down the reactor, maintain the safe shutdown condition, and operate all auxiliaries necessary for station safety.

The safety objective of the standby AC power source is to provide a single failure proof source of onsite AC power adequate for the safe shutdown of the reactor following abnormal operational transients and postulated accidents.

The unit AC power source provides AC power to all station auxiliaries and is the normal station AC power source when the main generator is operating. The station preferred (offsite) AC power source provides AC power to all station auxiliaries required for startup and shutdown and is normally in use when the unit AC power source is unavailable. The secondary (offsite) AC power source provides AC power to essential station auxiliaries. It is used to supply essential station auxiliary loads only when the main generator is shut down, there is a failure of the preferred AC power source, and failure of a standby AC power source.

The Station Blackout AC Power Source provides an independent diesel generator as the onsite source of AC power to the emergency service portions of the Auxiliary Power Distribution System in the unlikely event of a loss of preferred and secondary offsite power sources combined with a complete failure of the Standby AC Power System.

At the time of the event, the preferred AC and the secondary AC power sources were Operable and available to perform their intended safety function. In addition, the Station Blackout AC Power Source was Functional and available as the onsite source of AC power to the emergency service portions of the Auxiliary Power Distribution System.

Based on the operable and available preferred and secondary power sources, there was no adverse impact on the public health or safety.

REPORTABILITY

This report is submitted in accordance with 10 CFR 50.73(a)(2)(v)(A), 50.73(a)(2)(v)(B), and 50.73(a)(2)(v)(D) for a condition that could have prevented the fulfillment of the safety function of a system needed to shut down the reactor and maintain it in a safe shutdown condition, remove residual heat, and mitigate the consequences of an accident.

F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by Internet e-mail to 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.

Pilgrim Nuclear Power Station 05000293

PREVIOUS EVENTS

Events involving LERs where both EDGs were inoperable were reviewed. These LERs are summarized as follows:

were declared inoperable due to high ambient air temperatures. LER 98-004-00 and LER 98-002-00 involved events where both EDGs were declared inoperable due to low ambient temperatures.

These prior LERs involved events where both EDGs were declared inoperable at the same time; however, the events are different because, equipment failure and EDG maintenance was not involved.

ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) CODES The EIIS codes for Components and Systems referenced in this report are as follows:

COMPONENTS

Pipe Fitting

SYSTEMS

Diesel Cooling Water System

REFERENCES:

Condition Report CR-PNP-2016-2537