Today in 1959, a clogged coolant channel led to the meltdown of 30 percent of the fuel elements in the core of the uncontained 20-MW Sodium Reactor Experiment nuclear reactor at the Santa Susana Field Laboratory, about 30 miles northwest of downtown Los Angeles above Simi Valley. 
The coolant disruption and partial meltdown triggered a power excursion that could have caused the reactor to explode (as happened at Chernobyl). Although automatic safety systems failed to shut down the reactor, the operators successfully initiated a manual scram.
Inexplicably, the operators restarted the reactor just a couple hours later, even though they could not determine the cause of the power excursion and knew there was a problem with the coolant. And they kept it running for two weeks even as radiation readings went off the scale.
Large quantities of highly-radioactive gases were diverted to tanks, then deliberately vented into the atmosphere for weeks. The levels were so high, automatic monitors could not read them and workers could not safely analyze them, making precise measurements impossible.
But independent experts believe the accident may have released up to 260 times more radioactive iodine-131 and 80-100 times more cesium-137 than the partial meltdown at Three Mile Island in Pennsylvania in 1979, generally considered the worst reactor accident in US history.
North American Aviation’s Atomics International division, which operated Santa Susana for the Atomic Energy Commission, did not alert the public to this serious accident for five weeks, and then only issued a grossly-misleading press release that lied about the dangers.
The full, shocking story would not come to light for another 20 years, when inquisitive UCLA college students unearthed the buried truth and released the official documents to the news media.
For years after the accident, workers at Santa Susana illegally disposed of sodium-contaminated reactor components in an on-site open burn pit, discharging toxic and radioactive materials into the open air and ground, contaminating the rapidly-developing area around the lab.
Today, more than 500,000 people live within 10 miles of the site (more than 2,000 acres of which was also used for developing and testing rocket engines); thousands live less than two miles away. A significant number, including many children, have developed cancer.
In January 2006, Boeing—which took over the lab when it acquired Rockwell International, North American Aviation’s successor, in 1996—settled a $30 million lawsuit by 133 local residents who alleged their cancers, tumors, and autoimmune disorders were caused by the 1959 accident.
For more, see data.nbcstations.com/national/KNBC/… and etec.energy.gov/Library/Main/D….
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