Modelling the spread of radioactivity in seawater

When earthquake-triggered tsunami waves hit Japan in March, the surging water overtopped seawalls and caused massive damage. On top of the loss of life and general destruction, the disaster resulted in a release of radioactive seawater.

This visualization of the FVCOM simulated inundation process caused by the earthquake-induced tsunami in Japan on March 11 was designed by C. Chen and created by P. Xhe, with help from Z. Lai, G. Gao and Q. Xu.

Researchers Changsheng Chen of the University of Massachusetts at Dartmouth and Robert Beardsley of the Woods Hole Oceanographic Institute are investigating where that radioactivity may spread, using a mathematical model they developed in part through funding by the MIT Sea Grant College Program.

The meltdown at the Fukushima Daiichi Nuclear Power Plant released several different types of radioactive particles, but scientist are most interested in tracking a particularly persistent radioactive particle known as cesium-137.

This chemical has a half-life of 30 years - in other words, it takes about three decades for the particle's radioactivity to fall by half. If ingested, cesium-137 accumulates in living tissue, and it can travel up the food chain if one animal consumes a plant or animal that ingested contaminated particles.

Early estimates by oceanographers Chen and Beardsley suggest that the radioactive particles would disperse throughout the ocean differently at different depths. In some cases, contaminated seawater would reach the western coast of the United States in as little as five years.

The researchers have been building and refining their mathematical model of ocean circulation since 2003, and they recently received funding from the National Science Foundation to do an in-depth, collaborative study of how the particles would move through the ocean.