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:
- 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.
- 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.
- 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.
- 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.
- 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.
