A former chief U.S. nuclear regulator asserted Tuesday that the massive volumes of tritium-tainted water stored at the Fukushima No. 1 nuclear plant can be "safely" dumped into the sea after it is diluted to reduce the levels of radioactive tritium below the legal limit.

"Most people don't know what tritium is, so what they will think about is that it's bad, something that's really dangerous. But tritium is an element that we know a lot about," Dale Klein, chairman of Tokyo Electric Power Co.'s Nuclear Reform Monitoring Committee, told a news conference in Tokyo.

"It can be released safely into the ocean. We know worldwide what the safe limit for tritium release is," said Klein, who once headed the U.S. Nuclear Regulatory Commission.