Palisades Nuclear Plant Venting Radioactive Steam After Leaks Discovered in Cooling System

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Power Reactor Event Number: 47290
Region: 3 State: MI
Unit: [1] [ ] [ ]
RX Type: [1] CE
Notification Date: 09/25/2011
Notification Time: 18:21 [ET]
Event Date: 09/25/2011
Event Time: 15:06 [EDT]
Last Update Date: 09/25/2011
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(2)(iv)(B) – RPS ACTUATION – CRITICAL
Person (Organization):
Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
1 A/R Y 100 Power Operation 0 Hot Standby

Event Text

REACTOR TRIP DUE TO LOSS OF TWO 120 VOLT AC INSTRUMENT BUSSES“At 1506 EDT, while the electricians were working on the left train DC bus, a bus bar slipped causing an arc and a loss of the left train DC busses D-10 L and D-10 R. This resulted in the loss of two preferred AC [120 Volt Instrument] busses Y-10 and Y-30. The loss of both preferred AC busses caused a reactor trip, a safety injection signal, auxiliary feedwater actuation signal, containment high radiation isolation signal, and main steam isolation signal.

“All systems responded as expected. Electric power has been restored to the affected DC busses and preferred AC busses. The plant is stable in Mode 3 at NOT and NOP, and controlling temperature using Atmospheric Dump Valves. Pressurizer level is high due to the loss of letdown (result of containment isolation signal), however, it is recovering slowly.”

All rods fully inserted and the electrical lineup is back to normal.

The licensee has notified the NRC Resident Inspector, and will be notifying local agencies. The licensee will also be issuing a press release.

Entergy’s Palisades nuclear plant near South Haven is venting radioactive steam into the environment as part of an unplanned shutdown triggered by an electrical accident.

This shutdown, which began Sunday evening, came just five days after the plant restarted from a shutdown that was caused by a leak in the plant’s cooling system.

Nuclear Regulatory Commission spokeswoman Prema Chandrithal said that the current shutdown happened because an object slipped during work on a circuit breaker and caused an arc that took out power for one of two DC electrical systems that power safety valves and other devices. According to a notice filed with the Nuclear Regulatory Commission, the plant is stable and “controlling temperature using Atmospheric Dump Valves.”

“The steam that would normally go to the generators, that steam is now going into the environment … through the steam stack,” said Chandrithal. “This would have very low levels of tritium.” Tritium is a radioactive isotope of hydrogen.

The plant is monitoring the levels and will report them to the NRC, Chandrithal said. Palisades’ 798-megawatt reactor began operation in 1971, and through a license extension granted by NRC, may operate until 2031.


Source:, via Enformable
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