|Power Reactor||Event Number: 47290|
Region: 3 State: MI
Unit:  [ ] [ ]
RX Type:  CE
NRC Notified By: BRUCE BAUER
HQ OPS Officer: JOHN KNOKE
|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
50.72(b)(3)(iv)(A) – VALID SPECIF SYS ACTUATION
ANN MARIE STONE (R3DO)
|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|
|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.
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.
- March 11th 2011 – Fire at Tohuku Electric Onagawa Plant (enformable.com)
- Emergency declared at Michigan nuke plant: Reactor shut down after leak exceeded plant’s technical specifications – Cooling system spewing more than 10 gallons a minute (enenews.com)
- Cause of shutdown at North Anna nuclear plant sought – Post Earthquake Tour of Nuclear Power Station (enformable.com)
- March 12th, 2011 – ANSB Japanese Earthquake/Tsunami; Problems with Nuclear Reactors (enformable.com)
- March 11th, 2011 – NRC 23:15 Telecon Fukushima – Reactor 2 containment pressure almost double of design basis (enformable.com)
- NRC fails to change groundwater protection rules for nuclear plants despite recent tritium leaks and lax inspections (enformable.com)
- March 18th, 2011 – Tohoku-Taiheiyou-Oki Earthquake Effects On Japanese Nuclear Power Plants (enformable.com)
- NRC No. 11-046 March 13, 2011 – NRC SEES NO RADIATION AT HARMFUL LEVELS REACHING U.S. FROM DAMAGED JAPANESE NUCLEAR POWER PLANTS (enformable.com)