You can never eliminate all risk, adherence to proceedure, and rigorous inspections are a good start, but things that are unforseen can occur... as people work with things more and more outside normal experience more accidents will happen... For instance many explosive accidents have occurred when using inert liquid nitrogen... an uninsulated line carrying LN2 will precipitate out liquid oxygen from the atmosphere, if that drips onto asphault it creates a shock sensitive explosive- not something most people know, its not like us monkies evolved with liquid nitrogen....

I have only seen small accidents occur because people were working with the unusual- no permanent injuries, but just recently 4 Los Alamos personnell were fired/suspended because a laser injured the eyes of an intern- apparently it was thought the laser was turned off- it was probably a laser at an invisible wavelength... technology can bite you if you arent careful...

These accidents will always occur, but they are the price of living in the modern world... they are still tragedies...