The agreement, signed in May, includes a provision that the technology can only be used for power generation, the Asahi Shimbun reported. But it also allows Turkey to carry out uranium enrichment and plutonium extraction, potentially creating nuclear material for weapons.
The Diet, or parliament, is expected to debate the agreement soon before voting on its approval.
Mitsubishi Heavy Industries Ltd. is part of a consortium that negotiated a contract to build four reactors in Sinop, a Turkish city on the Black Sea. If the agreement goes through, it would be Japan's first nuclear technology export since the Fukushima disaster in March 2011.