05000293/LER-2017-001

LER-2017-001, Reactor Building Isolation Dampers Failed to Isolate

Pilgrim Nuclear Power Station
Event date:	01-16-2017
Report date:	07-17-2017
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material
2932017001R01 - NRC Website

LER 17-001-01 for Pilgrim Nuclear Power Station Regarding Reactor Building Isolation Dampers Failed to Isolate

ML17220A065
Person / Time
Site:	Pilgrim
Issue date:	07/17/2017
From:	Perkins E P Entergy Nuclear Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
2.17.051 LER 17-001-01
Download: ML17220A065 (6)

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 uNsEe0d Bto-10i m20p02,se(3a1n50in-0104) ccoel leocf tiMonandaogeesmneontt daisnpdlaByuadgceutr,reWnuayshvi njdto r;r0DBC c2o0n5t0r031. nl fumabme re athnes NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

Pilgrim Nuclear Power Station 05000-293

BACKGROUND

The Reactor Building Isolation and Control System (RBIS) safety objective is to limit the release to the environment of radioactive material so that offsite doses from a postulated design basis accident will be below the guideline values stated in 10 CFR 100. The RBIS shall trip the Reactor Building supply and exhaust fans, isolate the normal ventilation system, and provide the initiation signals for the Standby Gas Treatment System in the event of a postulated Loss Of Coolant Accident (LOCA) in the drywell or a postulated fuel handling accident in the Reactor Building.

The Reactor Building Heating, Ventilation and Air Conditioning (HVAC) System includes the RBIS subsystem, which supports the secondary containment function by automatically closing HVAC-related openings in secondary containment in the event of high drywell pressure, low reactor pressure vessel water level, or high airborne radiation levels in the refuel floor area, and Equipment Area Cooling System components, which supply supplemental cooling to the Core Standby Cooling Systems spaces within the reactor building and reject heat to the Reactor Building Closed Cooling Water System.

Pilgrim Nuclear Power Station (PNPS) was performing surveillance testing for the secondary containment isolation supply dampers. During the performance of this test the refuel floor supply isolation dampers showed dual indication when the control switches were taken to close. This is indicative of a failure of dampers to close.

EVENT DESCRIPTION

On January 16, 2017, with the reactor at 100 percent power and the mode switch in RUN, PNPS was performing surveillance testing of secondary containment isolation dampers when dampers AO-N-82 and AO-N-83, refueling floor supply isolation dampers, failed to fully close on demand as revealed by dual indication in the Control Room.

An 8-hour non-emergency notification was made in accordance with 10 CFR 50.72(b)(3)(v), Any event or condition that at the time discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to: (C) Control the release of radioactive material; or (D) Mitigate the consequences of an accident.

The dampers were manually closed. The reactor building isolation dampers were then cleaned and lubricated.

The dampers were then cycled five times with satisfactory closure time results. PNPS has returned the dampers to operable status.

CAUSE OF THE EVENT

The root cause of this event is that the preventative maintenance strategy was inadequate for secondary containment isolation supply dampers AO-N-82 and AO-N-83 and was not sufficiently structured to prevent repetitive failures of high critical components. This caused the condition, since preventative maintenance actions (which are intended to prevent repetitive failures of high critical components) were not adequate to properly maintain these components, resulting in a loss of safety function for secondary containment.

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 and to the Desk Officer, Office of Information and 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 05000-293 ,

CORRECTIVE ACTIONS

The immediate corrective action was for the reactor building isolation dampers to be cleaned and lubricated and post-work tested and the dampers were then cycled five times with satisfactory closure time results.

PNPS used compensatory measures to restore the dampers to operable status.

The Corrective Action to Prevent Recurrence addresses revising the preventative maintenance strategy for secondary containment supply and exhaust isolation dampers as follows: Refurbish damper actuators in accordance with vendor recommendations; Perform annual inspection and maintenance of secondary containment dampers; and bench test and record torque values to verify the adequacy of the actuators prior to installation and after they have been removed and replaced.

SAFETY CONSEQUENCES

There were no consequences to the safety of the general public, nuclear safety, industrial safety, and radiological safety due to this event. The actual consequences were a loss of safety function for secondary containment and entry into Limiting Condition for Operation Action Statement 3.7.C.2.a. Per the guidance in NUREG-1022, Section 5.2.2 the event date is the date of discovery, January 16, 2017, since there is no firm evidence, based on a review of relevant information that the issue existed previously. The Limiting Condition for Operation Action Statement was entered at 1155 hours0.0134 days <br />0.321 hours <br />0.00191 weeks <br />4.394775e-4 months <br /> on January 16, 2017 and exited at 1206 hours0.014 days <br />0.335 hours <br />0.00199 weeks <br />4.58883e-4 months <br /> on the same day. As such, the loss of safety function for secondary containment existed for a total duration of 11 minutes.

There was no adverse impact on the public health or safety.

REPORTABILITY

This event is reportable under 10 CFR 50.73(a)(2)(v)(C) and 10 CFR 50.73(a)(2)(v)(D), event or condition that could have prevented fulfillment of a safety function of structures or systems that are needed to: (C) Control the release of radioactive material; or (D) Mitigate the consequences of an accident. Subsequent to submission of the initial LER, based on NRC questions, it was concluded that this notification should also be conservatively made in accordance with 10 CFR 50.73(a)(2)(i)(B), as a condition that was prohibited by Technical Specifications.

PREVIOUS EVENTS

A review of PNPS Licensee Event Reports for the past five years did not identify any loss of safety function due to isolation dampers failing to isolate.

REFERENCE

CR-PNP-2017-00494