05000219/LER-2016-003

LER-2016-003, Manual SCRAM Inserted due to Leakage from the D' Reactor Recirculation Pump Seal

Oyster Creek, Unit 1
Event date:	3-0-2016
Report date:	06-29-2016
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(B), System Actuation 10 CFR 50.73(a)(2)(iv)(A), System Actuation
Initial Reporting
ENS 51895	10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation
2192016003R00 - NRC Website

LER 16-003-00 for Oyster Creek, Unit 1, Regarding Manual SCRAM Inserted due to Leakage from the 'D' Reactor Recirculation Pump Seal

ML16187A322
Person / Time
Site:	Oyster Creek
Issue date:	06/29/2016
From:	Gillin M Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RA-16-064 LER 16-003-00
Download: ML16187A322 (4)

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2. DOCKET

2015 002 00

Description of Event

On April 30, 2016, during the plant startup from 1M38 at approximately 1422 hours0.0165 days <br />0.395 hours <br />0.00235 weeks <br />5.41071e-4 months <br />, the station identified a rise in Unidentified Leak Rate (UILR). UILR rose from 0.21 gpm to 1.62 gpm at 1545 hours0.0179 days <br />0.429 hours <br />0.00255 weeks <br />5.878725e-4 months <br />. During this time reactor pressure was increased from 335 psi to 450 psi. As part of the troubleshooting for the unexpected rise in UILR, inspections in the drywell were performed and identified primary coolant leaking from the pump shaft of the D' Reactor Recirculation pump (RRP). At 1804 hours0.0209 days <br />0.501 hours <br />0.00298 weeks <br />6.86422e-4 months <br />, Control Room Operators initiated a manual SCRAM of the reactor to place the plant in a safe condition due to the leakage on the 'D' RRP.

Assessment of Safety Consequences

Following the manual SCRAM actuation, all systems responded as expected; therefore, this event is of low safety significance.

Cause of Event

In mid- 2015, unidentified drywell leak rate along with temperature and pressure trends on the 'D' RRP indicated degradation of the pump seal. The leakage was monitored for several months and remained within the limitations delineated by the Station's Technical Specifications (TS). In order to ensure that the condition did not degrade further, a maintenance outage (1M38) was scheduled to commence on April 25, 2016, with the replacement of the 'D' RRP seal as the main focus of the scope of work.

During 1M38 on April 27, 2016, the old 'D' RRP seal was removed and the new replacement seal was installed.

During the installation, the technicians discovered that the pump coupling could not be installed because it was too tall to fit onto the seal. The pump vendor then recommended machining the coupling and that minor machining is part of the normal fit-up process when installing new seal components. Additionally, the pump installation procedure specifically states that machining of up to 0.060" is permitted. Engineering prepared, approved and issued a technical evaluation to maintenance to machine the coupling to 0.060". The backing ring functions as a keeper for the 0-ring on, the shaft sleeve. Following this machining, the coupling fit and reassembly of the pump was completed.

Following completion of the maintenance work on the 'D' RRP and during the startup from 1M38, Control Room Operators identified a rising trend in UILR. UILR rose from 0.21 gpm to 1.62 gpm as reactor pressure was increased from 335 psi to 450 psi. Inspections conducted inside the drywell, identified primary coolant leaking from around the pump shaft of the 'D' RRP. At 1804 hours0.0209 days <br />0.501 hours <br />0.00298 weeks <br />6.86422e-4 months <br />, a manual SCRAM of the reactor was initiated to place the plant in a safe condition due to the leakage on the `D' RRP.

Following the SCRAM and during the disassembly of the 'D' RRP, when removing the pump half coupling keys the shaft sleeve 0-ring was found extruding on top of the back-up ring. Upon further disassembly the 0-ring was found to be cut, and an approximately one-inch piece of the 0-ring was found sitting on top of the back-up ring, which lead to the leakage from the seal cavity.

The Root Cause of the event was determined to be that the seal rebuild procedure was not properly revised in 2012 to prevent this failure from occurring.

Corrective Actions

• A Failure Mode analysis was conducted and implemented to determine the cause of the failure.

• The failed seal was replaced and tested satisfactorily.

• A Root Cause Evaluation was conducted.

• RRP seal replacement procedures will be revised to include critical dimension specifications with verifications and signoffs.

• Lessons learned have been communicated to Station Supervision.

Previous Occurrences

There were no previous occurrences of seal leakage resulting in manual SCRAM at Oyster Creek although several similar issues have been identified throughout the industry.