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August 26, 2003
Blackouts Leave Emergency
Diesels as
Tenuous Protection at Nuclear Plants
On August 14th the largest electrical blackout
in history caused sixteen nuclear plants to automatically shut down in the
U.S. and Canada. Even when a reactor is off-line, large amounts of
circulating water must cool the reactor core and large, densely packed waste
fuel pools to prevent overheating, core meltdown and/or an uncontrollable
pool fire.
Nuclear power plants run on offsite
power, not their own reactors.
If the electrical grid
fails, reactors are designed to automatically close down. One or more
emergency diesel generators are supposed to start up, with capacity to power
basic safety equipment, including the cooling system. If the diesels fail,
the reactor cannot be restarted without offsite power.
Attacks, ice or wind storms can also knock
out transmission lines to nuclear plants for extended periods.
Restoring off-site power to the 16 nuclear plants during the blackout – long
before reactors could power back up – was a high priority in order to
restore safety and security systems. Some back-up generators may have
failed. Reporting in the U.S. will not be completed for weeks, and could be
restricted; there may have been close calls the public will never learn
about.
Emergency diesel generators are tested for one hour per
year, typically in spring or fall.
Every five years, testing is required for a
full day, but not under conditions encountered if the generators must run
for hours in hot or cold weather.
Emergency generators are
susceptible to overheating.
Most blackouts occur
during hot weather when electricity demand is high. This is also when the
air-cooling of highly complex, truck-sized diesel generators is least
effective.
Testing of emergency generators led to the Chernobyl disaster in
1986. Operators ran a test to see if
they could wait a few minutes before starting emergency diesel generators –
in case of loss of offsite power like that in the U.S. and Canada. The
reactor quickly heated up and exploded, contaminating over 6,000 square
kilometers for centuries and triggering the forced resettlement of 415
towns.
Emergency diesel generators frequently fail in the U.S.
In some cases, a reactor core might last up
to eight hours without backup generators – although eroding conditions could
damage safety systems and impair workers’ ability to protect the core. Loss
of offsite power is a major risk factor for a reactor meltdown, which could
also lead to a waste pool fire. A few examples of recent diesel mishaps:
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At the Fermi plant near
Detroit, all four backup generators were found inoperable on February 1,
2003. Had the regional blackout happened at that time, there could have
been a full-scale evacuation called for the Detroit area, further
complicated because sirens to alert citizens within ten miles would not
have worked because the power grid was down. Reportedly, the sirens were
rendered inoperable in the communities surrounding all 16 nuclear plants
affected by the blackout.
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In June 1998 a tornado
downed all external transmission lines at Ohio’s Davis-Besse plant. The
diesel generators ran for twenty-six hours until they overheated and
failed. The outside air was 93 degrees. One of the transmission lines
had been restored only one hour before the generators failed.
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According to
Public Citizen, there
have been 15 instances in the past 12 months in which emergency generators
have either malfunctioned or failed to operate at all in certain cases
leading to plant shutdowns. On several occasions all backup generators
failed at once.
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The Brunswick I unit in
Southport, NC lost off-site power for nine hours in March 2000, during
which time both emergency generators failed simultaneously. One was
restarted in 18 minutes, after water surrounding the core had risen
several degrees.
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Failures of emergency
generators occur frequently – 138 reported between 1985 and 2000 – the
majority during testing, when there was no emergency requiring immediate
use. Fifty-nine were failures to start; 79 were failures while running.
Causes ranged from errors in design, manufacturing,
construction/installation, accidental actions, incorrect procedure,
failure to follow procedure, inadequate training, inadequate maintenance,
fire/smoke, humidity, high/low temperature, electromagnetic disruption,
radiation, bio-organisms, dirt, bad weather, and calibration failures.
This wide spectrum of error
variables, for a system upon which
the reactor core and spent fuel pools depend during a blackout, create an
incalculable number of unforeseen consequences. This is comparable to
having a vehicle sitting unused in a parking lot for a year at a time, then
depending on it to take you away at 100 miles per hour for an unknown
distance.
The NRC regularly allows nuclear plant owners to violate safety
regulations. Since 2000, the U.S.
Nuclear Regulatory Commission has issued 106 Notices of Enforcement
Discretion (NOED) – many involving faulty diesel generators – which allow a
utility to continue operating even while in violation of a regulation that
requires it to shut down for safety purposes. This is like a police
allowing drivers to skip vision tests or drive while under the influence.
Social and economic devastation.
If internal or external power is lost and
not restored, a reactor core will melt or explode, and the waste fuel pool
will catch fire. The radiological release could be many times worse than
Chernobyl, killing thousands and destroying tens of thousands of square
miles of property.
Due to industry and NRC secrecy, paradoxically invoking
security as a justification for that secrecy, the public may never know the
extent of problems experienced with diesel generators at plants affected by
the blackout. |
