A strong earthquake and tsunami had cut off power to vital cooling systems at four of the six reactors at the plant, causing them to explode or catch fire.
Sea water was used to cool the reactors and the used water was then dumped into the ocean, raising concerns over maritime contamination.
The Korea Ocean Research and Development Institute (KORDI) said prevailing sea currents near the atomic power plant that started releasing radioactive materials on Mar 12, always head east toward the central Pacific and away from the Korean Peninsula.
The warm Kuroshio current from Taiwan and the subarctic Oyashio or Okhotsk from the Arctic Sea meet southeast of the Fukushima plant and form the North Pacific Current that flows east.
"From mid-March the North Pacific Current maintained a width of over 100 kilometers and moved at a maximum of 1 meters per second toward the North American Continent," the laboratory said.
Because the region where the Kuroshio and Oyashio collide is not far offshore from Fukushima, any radioactive materials in the water would have been drawn away from the coast and into the vast ocean, where they would become diluted and effectively harmless to marine life and humans, it added.
KORDI said that its assessment is based on a detailed model of how the currents in the western Pacific flow.