COLUMBIA — Flooding from a dam break at Lake Jocassee could overwhelm Oconee County’s nuclear plant in much the same way Japan’s Fukushima reactors were disabled by rising flood waters last year, a leading atomic safety expert said Wednesday.

Nuclear engineer David Lochbaum said the federal government should ensure all possible plant improvements are made at the northwest S.C. plant, as well as the Lake Jocassee dam. The Nuclear Regulatory Commission hasn’t required some flood-related improvements yet at the Duke Energy plant, he said.

“I don’t fully understand that,” Lochbaum said before a community meeting in Clemson. “We need to get all these things in the rear view mirror.”

Lochbaum said the odds of Fukushima experiencing a flood like that, which resulted from last year’s tsunami, were about 1 in 1,000 years. Odds of a dam break flooding the Oconee nuclear plant are even longer — but that doesn’t mean a catastrophe can’t happen, he said.

Flooding knocked out power at Fukushima, causing a loss of cooling water to keep reactors from overheating and leaking radiation.

“Fukushima shows that long shots do come in sometimes,” said Lochbaum, with the Union of Concerned Scientists, a watchdog group. “If there are things we can do to protect from that hazard, it is prudent to do so.”