The ongoing crisis at the Fukushima No. 1 plant is a sign that the world needs to seriously rethink nuclear safety and consider possibly ending its dependence on atomic power, the former chairman of the U.S. Nuclear Regulatory Commission said Tuesday in Tokyo.

"When you look at what happened around the Fukushima Daiichi (No. 1) area, it's simply unacceptable," as tens of thousands of people have been unable to return to their homes due to radioactive contamination, said Gregory Jaczko, who served as the top U.S. nuclear regulatory official for nearly three years until July 2012.

Given that Japan is extremely prone to earthquakes and tsunami, among other disasters, using nuclear power poses serious risks unless some kind of new technology is created to completely eliminate the possibility of severe accidents, Jaczko told reporters at the Foreign Correspondents' Club of Japan.