Event Notification Report for March 04, 2024

PART 21 - SERVICE WATER BOOSTER PUMP BEARING HOUSING COVER OIL LEAK

The following information was provided by the licensee via phone and email:

"On August 27, 2022, while in Mode 1 at 100 percent power, Nebraska Public Power District (NPPD) Cooper Nuclear Station (CNS) identified a 3 drops per minute (dpm) oil leak from the radial (inboard) bearing housing cover on one of four residual heat removal (RHR) service water booster pumps (SWBP); specifically, SWBP-D.

"Subsequent analysis determined that the leak was a result of a deviation with the configuration of the labyrinth seal drain path. This deviation was due to an error introduced in a manufacturing drawing used by the vendor for the fabrication of four new replacement pumps. The bearing housing cover is a unique design to CNS for the RHR SWBPs.

"On March 1, 2024, NPPD completed a substantial safety hazard evaluation and determined that the manufacturing drawing error could cause a substantial safety hazard. The NRC Resident Senior Resident has been notified. This is a non-emergency notification required by 10 CFR 21.21(d)(3)(i). A written notification will be provided within 30 days."

The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:

All four SWBPs had a similar housing design. Three of the four pump housings have been replaced. No other nuclear plant is affected due to the housing design being unique to CNS.

INADVERTENT SIREN ACTIVATION

The following information was provided by the licensee via email:

"At 1330 CST, on March 1, 2024, an equipment vendor was coordinating with Wright County performing maintenance on an emergency siren when the county operator mistakenly sent an alarm signal instead of cancel signal, activating all Wright County emergency sirens for approximately 17 seconds. At 1345 CST, the Monticello Nuclear Generating Plant (MNGP) emergency planning coordinator received a notification from the vendor and notified the duty shift manager [of the inadvertent activation].

"Wright County officials are planning to make a public notification via social media to local residents.

"No press release by the licensee is planned at this time.

"This event is reportable per 10 CFR 50.72(b)(2)(xi), 'News Release or Notification of Other Government Agencies.' This is a 4-hour Reporting requirement.

"The NRC Resident has been notified."

AUTOMATIC REACTOR TRIP DUE TO LOSS OF MAIN FEEDWATER PUMP SUCTION

The following information was provided by the licensee via email:

"At 1142 CST on 3/3/2024, with Unit 2 in Mode 1 at 29 percent power, the reactor automatically tripped due to a turbine trip caused by a loss of suction to the 22 main feedwater pump. All systems responded normally post trip. Decay heat is being removed via the auxiliary feedwater water system. Secondary steam control mechanism is the steam generator PORVs [power operated relief valves]. Unit 1 remains at 100 percent power and is unaffected.

"This event is being reported pursuant to 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A). The resident NRC inspector has been notified."

The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:

The trip occurred while the licensee was returning to power operations after a refueling outage. During the trip, all rods inserted into the core. The plant is in a normal shutdown electrical lineup with offsite power available. The plant will be maintained at normal operating temperature and pressure. There is no known primary to secondary leakage. The cause of the loss of 22 main feedwater pump suction is under investigation.

AUTOMATIC REACTOR SCRAM DUE TO MAIN TURBINE TRIP ON LOW CONDENSER VACUUM

The following information was provided by the licensee via email:
"On 3/3/24 at 1942 EST, while performing a plant shutdown in preparation for a refuel outage, Nine Mile Point Unit 2 experienced a reactor scram due to a main turbine trip on low condenser vacuum. The plant was at approximately 55 percent power at the time of the reactor scram.

"Additionally, following the scram a low RPV [reactor pressure vessel] level scram and containment isolation signal on level 3 was received, as expected. The containment isolation signal impacted RHR [residual heat removal] shutdown cooling, RHR letdown to radwaste, and RHR sampling. All impacted valves were closed at the time the isolation occurred.

"All control rods were fully inserted. Plant response was as expected. Post scram, the main turbine bypass valves are being used to control decay heat, and normal post scram level control is via the feed / condensate system.

"This is being report under 10 CFR 50.72(b)(2)(iv)(B), 'RPS Actuation', and 10 CFR 50.72(b)(3)(iv)(A), 'Specified System Actuation'.

"Unit 1 is not affected. There was no impact on the health and safety of the public or plant personnel.

"The NRC Resident Inspector has been notified."

The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:

The cause of the low condenser vacuum was a momentary loss of sealing steam. The condenser remained viable for decay heat removal. All safety equipment is available. The grid is stable with the plant in its normal shutdown electrical configuration.