The SL-1, or Stationary Low-Power Reactor Number One, was a United States Army experimental nuclear power reactor which underwent a steam explosion and meltdown on January 3, 1961, killing its three operators. The direct cause was the improper withdrawal of the main control rod, responsible for 80% of neutron moderation in the poorly designed reactor core. The event's the only fatal reactor accident in the United States. The facility, located at the National Reactor Testing Station approximatel… (More on Sl-1)