Mainichi Daily News, November 17, 2009
A barrel containing chemicals exploded as workers at a company here tried to neutralize the contents, sending the barrel flying over elevated bullet train tracks and a station before coming crashing down into a parking lot more than 100 meters away.
[...]
Nippon Shinyaku officials and other sources said that the 200-liter steel drum had contained a coolant including hydrogen peroxide. Three workers were trying to neutralize the contents prior to disposal, and inserted caustic soda (sodium hydroxide) into the barrel, but this produced a violent chemical reaction, and the barrel exploded.
The chemicals were scattered around the premises, but the workers, who had sensed danger, had already escaped, and were unscathed.
A company spokesman speaking at a news conference after the accident said the workers had been unaware of the chemicals contained in the coolant.
"Mixing hydrogen peroxide and caustic soda is taboo. The workers didn't realize that the coolant contained hydrogen peroxide.
(Full Story)
Taboo?

Well, I guess the good news is that they weren't nuke plant workers...