Three former executives at the operator of Japan's Fukushima nuclear plant went on trial Friday, the only people ever to face a criminal court in connection with the 2011 meltdowns that left swathes of countryside uninhabitable. Ex-Tokyo Electric Power (Tepco) chairman Tsunehisa Katsumata, 77, and former vice presidents Sakae Muto, 66, and Ichiro Takekuro, 71, all pleaded not guilty to charges of professional negligence resulting in death and injury, over six years after the worst atomic accident in a generation. Katsumata told a three-judge panel hearing the case that it was impossible for him to have foreseen the risk of the towering waves that pummelled Japan's northeast coast and swamped reactors in March 2011.