Event Notification Report for July 08, 2024

AGREEMENT STATE REPORT - STUCK OPEN SHUTTER
The following information was received from the state of Nevada via email:

"Nevada Gold Mines LLC - Goldstrike, [Nevada license] 05-11-13545-01, reported a stuck open shutter on a Berthold LB 7440, serial number 1459. The fixed gauge remains installed pending the arrival of a contractor to replace the failed shutter. Radiation surveys of the installed gauges are as expected for a gauge in service giving 0.11 mR/hour 1 foot back from the gauge (in walkway). Gauge is installed in a location where there is occasional foot traffic, providing no additional exposure mine/mill staff until it can be repaired. Licensee [was] reminded to report the failure to the manufacturer in accordance with the operations and maintenance manual for the gauge."

The gauge contains 50 mCi of Cs-137. The state of Nevada considers this event closed.

Nevada Item Number: NV240005

MANUAL REACTOR TRIP AND AUTOMATIC SAFEGUARDS ACTUATION

The following information was provided by the licensee via email:

"At 2125 EDT on 07/08/2024, with Unit 3 in Mode 1 at 100 percent power, the reactor was manually tripped due to main feedwater pump `A' miniflow valve failing open, which resulted in lowering steam generator water level. Additionally, an automatic safeguards actuation occurred due to the cooldown of the reactor coolant system. The trip was not complex, with all safety systems responding normally post-trip.

"Operations responded and stabilized the plant. Decay heat is being removed by the passive residual heat removal heat exchanger. Units 1, 2, and 4 are not affected.

"Due to the core makeup tank actuation, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(A). The reactor protection system actuation while critical is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). Additionally, this event is reportable per 10 CFR 50.72(b)(3)(iv)(A) as an event that resulted in a valid containment isolation actuation and a valid passive residual heat removal heat exchanger actuation.

"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 main feedwater pump 'A' miniflow valve failing open was unknown and under investigation at the time of the notification of this event to the NRC.

INADVERTENT SIREN ACTIVATION

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

"On July 8, 2024, at 0748 EDT, six emergency response sirens were inadvertently actuated. Four sirens are located in Chatham County and two sirens are in Wake County. The first notification was made to Wake County at 0754. Investigation is ongoing to determine the cause of the actuation. Duke Energy notified the state and all counties within the emergency planning zone (EPZ). A press release was issued by Wake and Chatham Counties.

"This is a four-hour notification, non-emergency for the notification of another government agency. This event is reportable in accordance with 10 CFR 50.72(b)(2)(xi).

"There was no impact to the health and safety of the public or plant personnel.

"The NRC resident inspector has been notified."

AUTOMATIC REACTOR TRIP

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

"At 1521 EDT on July 8, 2024, with Unit 1 in Mode 1 at 100 percent power, the reactor automatically tripped due to a main turbine trip. The [reactor] trip was not complex with all systems responding normally post trip.

"Operations responded and stabilized the plant. Decay heat is being removed by discharging steam to the main condenser using the steam dump system and the auxiliary feedwater (AFW) system. Unit 2 is not affected.

"Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). The expected actuation of the AFW system (an engineered safety feature) is being reported as an eight-hour report under 10 CFR 50.72(b)(3)(iv)(A).

"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 specific cause of the turbine trip is under investigation by the licensee.