Offsite Power Restored at Two Millstone Reactors

Both reactors at the Millstone nuclear plant in Connecticut tripped offline Sunday after they lost offsite power.

Millstone nuclear plant. Source: NRCQuoting a release from the Nuclear Regulatory Commission, the Hartford Courant reported that safety systems functioned as expected, with emergency diesel generators providing backup power. The trip happened shortly after 7 a.m. and offsite power was restored that afternoon. The problem was suspected to have originated in Millstone's switchyard.

Dominion operates both pressurized water reactors at the plant near New London, Conn. First licensed in 1975, unit 2 was designed by Combustion Engineering and generates 870 megawatts. Unit 3 generates 1,210 megawatts and was first licensed in 1986.

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  • This old safety principle of "off-site emergency power" is actually of NO value.

    It would be of value only in case it factually shows itself of a higher safety level than the nuclear plant and also immune to any kind of erratic external event (hurricane, earthquake, wild fires, floods, political riots, sabotage and so on..).

    In reality, as seen at Fukushima, it has no value. It shall be removed and substituted with duplicated diesel engines, systematically in use each month for 24hours non-stop, which produced diesel energy shall feed all internal plant needs.

    The 1945 old security concepts must be revised from time to time......

  • UPDATE: Event reports released today indicate the plant declared a notice of unusual event during the power outage and that a pressurizer relief tank leaked inside containment at unit 3.

    -- Peter

    Nuclear Street News Team

    Unit 3: UNUSUAL EVENT DUE TO LOSS OF OFFSITE POWER

    At 0702 EDT on 5/25/14, Millstone Units 2 and 3 experienced a loss of offsite power and subsequent trip of both units. An Unusual Event was declared by Millstone Units 2 and 3 at 0715 EDT.

    Power is currently being supplied to all emergency busses by the emergency diesel generators. Offsite power is not available.

    At this time, it appears that the loss of offsite power is due to a localized issue in the Millstone switchyard. The surrounding areas were not affected.

    A decision was made to take the NRC to monitoring mode at 0749 EDT with Region 1 in the lead.

    Notified DHS SWO, FEMA Ops Center, NICC Watch Officer, DOE Ops Center, USDA Ops Center, HHS Ops Center, and Nuclear SSA via email.

    * * * UPDATE FROM MICHAEL CICCONE TO DANIEL MILLS AT 1330 EDT * * *

    "The loss of offsite power was due to one main line coming into the plant shorting to ground. Emergency plan procedures have been implemented, natural circulation has been established, and the plant is stable. Offsite electrical power has been restored to both Unit 2 and Unit 3. Emergency diesel generators have been secured, and plant equipment has been restored to a normal line up.

    "Extended loss of instrument air following the loss of offsite power complicated the recovery actions. The normal reactor coolant system letdown flow path was not able to be established. This resulted in the rupture of the pressurizer relief tank rupture disk inside containment. The relief valve on the volume control tank lifted when restoring normal letdown. This caused the primary drains transfer tank to overflow into the auxiliary building. This overflow path has been isolated. Supplementary leakage collection system radiation monitor HVR-RE19B, and auxiliary building normal ventilation radiation monitor HVR-RE10B, are indicating normal levels."

    Notified R1DO (Gray), R1DRA (Lew), NRR EO (Kokajko), IRD MOC (Grant).

    * * * UPDATE FROM MICHAEL CICCONE TO DANIEL MILLS AT 1548 EDT * * *

    At 1414 EDT the licensee terminated the Unusual Event.

    Notified R1DO (Gray), R1DRA (Lew), NRR EO (Kokajko), IRD MOC (Grant), DHS SWO, FEMA Ops Center, NICC Watch Officer, DOE Ops Center, USDA Ops Center, HHS Ops Center, and Nuclear SSA via email.

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    Unit 2: UNUSUAL EVENT DUE TO LOSS OF OFFSITE POWER

    At 0702 EDT on 5/25/14, Millstone Units 2 and 3 experienced a loss of offsite power and subsequent trip of both units. An Unusual Event was declared by Millstone Units 2 and 3 at 0715 EDT.

    Power is currently being supplied to all emergency busses by the emergency diesel generators. Offsite power is not available.

    At this time, it appears that the loss of offsite power is due to a localized issue in the Millstone switchyard. The surrounding areas were not affected.

    A decision was made to take the NRC to monitoring mode at 0749 EDT with Region 1 in the lead.

    Notified DHS SWO, FEMA Ops Center, NICC Watch Officer, DOE Ops Center, USDA Ops Center, HHS Ops Center, and Nuclear SSA via email.

    * * * UPDATE FROM MICHAEL CICCONE TO CHARLES TEAL AT 1330 EDT ON 5/25/14 * * *

    All EDGs have been secured and offsite power has been restored.

    The licensee is reporting the loss of two stack radiation monitors - 8168 and 8169. This is reportable under 10CFR50.72(b)(3)(xiii).

    Notified R1DO (Gray), R1DRA (Lew), NRR EO (Kokajko), IRD MOC (Grant).

    * * * UPDATE FROM MICHAEL CICCONE TO DANIEL MILLS AT 1548 EDT * * *

    At 1414 EDT the licensee terminated the Unusual Event.

    Notified R1DO (Gray), R1DRA (Lew), NRR EO (Kokajko), IRD MOC (Grant), DHS SWO, FEMA Ops Center, NICC Watch Officer, DOE Ops Center, USDA Ops Center, HHS Ops Center, and Nuclear SSA via email.