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Nuclear Event |Manual Reactor Trip – Reactor Coolant System leakage: Millstone Nuclear Power Plant, Connecticut

2016/06/13

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: REQUIRED SHUTDOWN AND REACTOR TRIP /RPS ACTUATION – CRITICAL

Nuclear Event in USA on Sunday, 12 June, 2016 at 20:13 [EDT].

TECHNICAL SPECIFICATION REQUIRED SHUTDOWN AND REACTOR TRIP

At 2013 EDT on 6/12/16, Millstone Unit 3 commenced a Technical Specification (TS) required shutdown due to excessive Reactor Coolant System leakage from the “A” Reactor Coolant Pump (RCP) third stage seal. The leakage from the third stage seal was approximately two gpm which is greater than the Technical Specification (TS) limit of less than one gpm.

During the shutdown, oscillations developed in the Main Feedwater which required the operator to initiate a manual reactor trip. Unit 3 is currently stable in Mode 3. Decay heat is being released via the Steam Dumps to the Main Condenser. Normal offsite power is available and the unit is in a normal shutdown electrical line-up. The cause of the Main Feedwater oscillations is being investigated.

The licensee notified the NRC Resident Inspector. The licensee notified State and local government agencies.

* * * UPDATE FROM WALTER ORF TO DONALD NORWOOD AT 0129 EDT ON 6/13/2016 * * *

The following clarifies Feedwater isolation vs. Feedwater oscillation:

“At 2337 EDT on 6/12/16, a manual reactor trip was initiated on Unit 3 following feedwater isolation. As expected, Aux Feedwater system (AFW) initiated on the reactor trip. The trip was uncomplicated and the plant is currently in Mode 3 with a normal electric line-up and decay heat is being removed via steam dumps to the condenser. This is reportable under 10 CFR 50.72(b)(2)(iv)(B) – RPS Actuation – Critical and 10 CFR 50.72(b)(3)(iv)(A) – Valid Specific System Actuation.”

“The Feedwater isolation occurred due to high Steam Generator water level.”

The licensee notified the NRC Resident Inspector.

Notified R1DO (Arner).

Source: NRC  Event Number: 52000
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Previous Event

Nuclear Event in USA on Sunday, 15 April, 2016 at 06:38 [EDT]. UNUSUAL EVENT DUE TO MAIN GENERATOR HYDROGEN LEAK IN TURBINE BUILDING

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