The Nuclear Regulatory Agency said Tetsuo Nayuki, 54, will return to the Education, Culture, Sports, Science and Technology Ministry, where he previously worked, Kyodo News reported.
Officials said Friday Nayuki was reprimanded for giving a draft copy of the report to Japan Atomic Power, which operates the Tsuruga nuclear plant.
Officials say Nayuki handed over the document during a meeting Jan. 22, an action ascribed to carelessness.
"It is extremely regrettable that a senior official did such a thing. It was a thoughtless act, because we should be especially careful when having contact with parties subject to regulations and should be transparent in the exchanges," NRA Chairman Shunichi Tanaka said in a statement.