UPDATE - Please See NRC Event Reports 46793 for
Browns Ferry and Event Number: 46797 for Sequoyah.
Browns Ferry Event 46793 http://www.nrc.gov/reading-rm/doc-collections/event-status/event/en.html#en46793
* Every plant Trip has some sort of complications
although, within the realm of operators' and plant personnel's ability, skill,
and training to deal with. A triple Loss of Offsite Power is a fairly
straight forward event, as long as the Diesels are running. The sooner
"reliable" grid power is restored, the better.
* Browns Ferry Units 1, 2, and 3 are General
Electric (GE) Boiling Water Reactors (BWRs) operated by the government
corporation known as Tennessee Valley Authority.
*
I do not know exactly where the tornados hit the Grid, to knock out offsite
power - I will attempt to find out.
*
Each BWR Unit has 3 Emergency Diesel Generators (EDG) that automatically power
up their Divisions when a Loss of Offsite Power occurs (this is supposed to be
an infrequent occurrence.
v RCIC (Reactor Core Isolation
Cooling Pump) is not functioning optimally. The HPCI (High Pressure Core
Isolation Pump) automatically started in response to a lowering Reactor Vessel
Water Level. I have to keep my eye on this because a later Unit 1 Update
indicates that the HPCI system may not be functioning to maintain and control
Vessel Water Level, and a PCIS (Pressure Containment Isolation Signal) was
necessary to "Bottle" up Containment to conserve water inventory. The
report is vague so I need to pursue this a bit.
v Unit 3 has it's
"B" Emergency Diesel Generator (EDG) Out-of-Service for Maintenance,
therefore it only has 2 EDGs running - as of last report. Fortunately, 1 EDG is
required.
v
Valve
Indication/Control Problem with Main Steam Isolation valve - probably minor
Sequoyah Event 46797 http://www.nrc.gov/reading-rm/doc-collections/event-status/event/en.html#en46797
* This reports means that although Offsite Power is
AVAILABLE, it is on shaky grounds due to instability. We call this
condition, Available, but not Operable. This could mean that there are
fewer grid energy sources than is deemed acceptable for a stable, reliable
grid. It could mean that there are actual Voltage Fluctuations. The report does
not state the reason that Sequoyah has removed the Operable "Good
Housekeeping Seal of Approval" from the Offsite Grid.
* I have included that wording from Technical
Specification 3.8.1.1, action d, which is the bible of operations and is
committed to memory by operators.
v T.S. LCO 3.8.1.1, action d,
requires verifying EDG operability within 8 hours and restoration of both
offsite power sources within 24 hours or placing both Units in mode 3.
v
Because
the T.S. LCO (Limiting Condition for Operation) was entered last night at 1930,
I assume that Sequoyah did not shut down because the Morning Status Report,
http://www.nrc.gov/reading-rm/doc-collections/event-status/reactor-status/ps.html
shows them at near full power - therefore this condition may be resolved.
Tornadic Activity once again removed normal power
from multiple nuclear reactors, forcing them to resort to Emergency Diesel Generators.
Only last week did the Surry Nuclear Power Plant Units 1 and 2, suffer a loss
of offsite power (LOOP) from tornados, causing them to exist on Emergency
Power for the better part of 2 days. Is there a pattern?
See This:
(Reuters) -
Severe storms and tornadoes moving through the Southeast dealt a severe blow to
the Tennessee Valley Authority on Wednesday, causing three nuclear reactors in
Alabama to shut and knocking out 11 high-voltage power lines, the utility and
regulators said.
All three units at TVA's 3,274-megawatt Browns Ferry
nuclear plant in Alabama tripped about 5:30 EDT (2230 GMT) after losing outside
power to the plant, a spokesman for the U.S. Nuclear Regulatory Agency said.
COMMENT
BY Chris Harris - TVA is a government owned facility, so expect slower than
usual response
Chris in Delaware