During the 2011 nuclear disaster at Japan's Fukushima Daiichi power plant, the man at the helm of the Tokyo Electric Power Company (TEPCO) ordered workers not to use the term "meltdown" to describe damage.

Instead, TEPCO officials described the condition of the three reactors as less serious "core damage" for two months after a March 2011 earthquake and tsunami destroyed the plant.  Despite that fact that three reactors hadn't just melted down, the radioactive cores melted through the floor of the plant.  To this day, scientists do not know the exact location of the three molten cores. 

An outside investigation team consisting of three lawyers appointed by TEPCO put together a report claiming that it is "highly likely" the Japanese government pressured TEPCO's then-president Masataka Shimizu.  Although the report does not cite any direct evidence of that, there is video showing that TEPCO executives clearly believed it was the case.

On 14 March, TEPCO's then-vice president Sakae Muto uses the phrase "possibility of meltdown" at a news conference.  A company official rushes over to Muto, shows him a memo, and whispers into his ear:  "The Prime Minister's Office says never to use this word."  That memo has not been found.

"Mr. Shimizu's understanding was the term 'meltdown' could not be used without permission from the Prime Minister's Office," said Yasuhisa Tanaka, the lawyer who headed the investigation, at a news conference at TEPCO headquarters.  "The notion that the word should be avoided was shared company-wide.  But we don't believe it was a cover-up," he added.

The Prime Minister at the time of the disasater was Naoto Kan, who has since become an anti-nuclear evangelist.  Earlier this year, Mr. Muto and two other former TEPCO officials were indicted for their handling of the crisis.