Nine years before the 2011 meltdown crisis at the Fukushima No. 1 nuclear power plant, Tokyo Electric Power Co. turned down a request from the government's nuclear watchdog for it to conduct a simulation of powerful tsunami that could hit the plant, a court document showed on Tuesday.

Written testimony was submitted to the Chiba District Court on Nov. 24 by Shuji Kawahara, who was head of a team responsible for quake safety issues at the now-defunct Nuclear and Industrial Safety Agency (NISA) — the predecessor of today's Nuclear Regulation Authority.

Kawahara's testimony showed that Tepco may have missed an opportunity to examine the possibility of a tsunami disaster almost a decade before such a crisis came to pass in 2011, when massive waves knocked out critical cooling systems at the Fukushima No. 1 plant.