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Nuclear Event |Manual Reactor Trip – Unusual Event, Emergency Declared: Millstone Nuclear Power Plant, Connecticut

2016/05/17

North America – USA | State of Connecticut, Millstone Nuclear Power Plant [Unit 3]
Location: 41°18’43.0″N 72°10’07.0″W
Present Operational Age: ~30 years
Event: EMERGENCY DECLARED/RPS ACTUATION – CRITICAL

Nuclear Event in USA on Sunday, 15 April, 2016 at 06:38 [EDT].

UNUSUAL EVENT DUE TO MAIN GENERATOR HYDROGEN LEAK IN TURBINE BUILDING

At 0638 EDT on 5/15/2016, an Unusual Event (EAL GU.2) was declared on Millstone Unit 3 due to a Main Generator hydrogen gas leak into the Turbine Building. At 0645 EDT, operators manually tripped the reactor. All rods inserted. All systems functioned as expected following the reactor trip. Operators are currently venting the remaining hydrogen from the generator through the normal vent path. There is no safety related equipment out-of-service. The plant is in a normal post-trip electrical line-up. All Emergency Diesel Generators are available.

The licensee notified the State of Connecticut and the NRC Resident Inspector.

Notified DHS SWO, FEMA Ops Center, and DHS NICC Watch Officer. Notified via E-mail FEMA National Watch Center and NuclearSSA.

* * * UPDATE FROM MIKE CICCONE TO HOWIE CROUCH AT 1044 EDT ON 5/15/16 * * *

At 0949 EDT, the licensee terminated the Unusual Event.

“At 0645 EDT on 5/15/16, a manual reactor trip was initiated at Millstone Unit 3 due to a hydrogen leak from the main generator. As expected, Auxiliary Feedwater System (AFW) initiated on the reactor trip. The trip was uncomplicated and the plant is currently in Mode 3 with a normal electric lineup and decay heat is being removed via steam dumps to the condenser. The cause of the hydrogen leakage is under investigation. This is reportable under 10 CFR 50.72(b)(2)(iv)(B) – RPS actuation while critical, and 10 CFR 50.72 (b)(3)(iv)(A) – valid specified system actuation.”

The licensee has notified Waterford Township, the State of Connecticut and the NRC Resident Inspector.

Notified R1DO (Burritt), NRR ET (McDermott), NRR EO (Morris), IRD (Grant), DHS SWO, FEMA Ops Center, DHS NICC, FEMA National Watch Center (email) and NuclearSSA (email).

Source: NRC  Event Number: 51929
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