The extent of the damage at Japan’s Fukushima nuclear facility is still unknown, but comparisons to Chernobyl were inevitable as soon as fuel rods became exposed and an explosion rocked the site . But is the analogy accurate?

Chernobyl, the worst nuclear disaster thus far in the history of the industry, was the result of a drill that went catastrophically wrong on April 26, 1986. The drill, ironically, was intended to test a known time gap between a potential power failure and the performance of backup generator pumps. Workers had been made aware that the experiment would be taking place, but it still ended catastrophically.